Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Entity Registrant Name	MACROGENICS INC
Entity Central Index Key	0001125345
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,918,852
Entity Public Float			$ 936

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 211,727	$ 84,098
Marketable securities	93,394	192,898
Accounts receivable	13,643	2,764
Prepaid expenses	3,151	3,483
Other current assets	383	704
Total current assets	322,298	283,947
Property, equipment and software, net	49,983	17,961
Marketable securities, non-current	0	7,986
Other assets	1,602	1,369
Total assets	373,883	311,263
Current liabilities:
Accounts payable	2,451	3,995
Accrued expenses	38,581	16,134
Deferred revenue	7,202	4,261
Deferred rent	1,048	1,319
Lease exit liability	298	1,593
Other current liabilities	175	0
Total current liabilities	49,755	27,302
Deferred revenue, net of current portion	13,637	10,045
Deferred rent, net of current portion	11,253	4,867
Lease exit liability, net of current portion	0	298
Total liabilities	74,645	42,512
Stockholders' equity:
Common stock, $0.01 par value – 125,000,000 shares authorized, 36,859,077 and 34,870,607 shares outstanding at December 31, 2017 and 2016, respectively	369	349
Additional paid-in capital	611,270	561,198
Accumulated other comprehensive loss	(61)	(82)
Accumulated deficit	(312,340)	(292,714)
Total stockholders' equity	299,238	268,751
Total liabilities and stockholders' equity	$ 373,883	$ 311,263

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	125,000,000	125,000,000
Common stock, shares outstanding (in shares)	36,859,077	34,870,607

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Revenue from collaborative agreements	$ 155,516	$ 86,582	$ 99,368
Revenue from government agreements	2,226	5,298	1,486
Total revenues	157,742	91,880	100,854
Costs and expenses:
Research and development	147,232	122,091	98,271
General and administrative	32,653	29,831	22,765
Total costs and expenses	179,885	151,922	121,036
Loss from operations	(22,143)	(60,042)	(20,182)
Other income	2,517	1,514	42
Net loss	(19,626)	(58,528)	(20,140)
Other comprehensive loss:
Unrealized loss on investments	(21)	(77)	(5)
Comprehensive loss	$ (19,647)	$ (58,605)	$ (20,145)
Basic and diluted net loss per common share	$ (0.54)	$ (1.69)	$ (0.63)
Basic and diluted weighted average number of common shares	36,095,080	34,685,274	31,801,645

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2014	$ 121,286	$ 280	$ (19)	$ 335,071	$ (214,046)	$ 0
Balance (in shares) at Dec. 31, 2014		27,995,638	865
Share-based compensation	7,847			7,847
Issuance of common stock, net of offering costs	203,467	$ 60		203,407
Issuance of common stock, net of offering costs (in shares)		5,976,827
Stock plan related activity	882	$ 3	$ (29)	908
Stock plan related activity (in shares)		373,289	925
Retirement of treasury stock	0		$ 48	(48)
Retirement of treasury stock (in shares)			(1,790)
Unrealized gain on investments	(5)					(5)
Net loss	(20,140)				(20,140)
Balance at Dec. 31, 2015	313,337	$ 343	$ 0	547,185	(234,186)	(5)
Balance (in shares) at Dec. 31, 2015		34,345,754	0
Share-based compensation	12,165			12,165
Stock plan related activity	1,854	$ 6	$ (39)	1,887
Stock plan related activity (in shares)		524,853	1,862
Retirement of treasury stock	0		$ 39	(39)
Retirement of treasury stock (in shares)			(1,862)
Unrealized gain on investments	(77)					(77)
Net loss	(58,528)				(58,528)
Balance at Dec. 31, 2016	268,751	$ 349	$ 0	561,198	(292,714)	(82)
Balance (in shares) at Dec. 31, 2016		34,870,607	0
Share-based compensation	14,744			14,744
Issuance of common stock, net of offering costs	34,244	$ 17		34,227
Issuance of common stock, net of offering costs (in shares)		1,699,284
Stock plan related activity	1,104	$ 3	$ (40)	1,141
Stock plan related activity (in shares)		289,186	1,862
Retirement of treasury stock	0		$ 40	(40)
Retirement of treasury stock (in shares)			(1,862)
Unrealized gain on investments	21					21
Net loss	(19,626)				(19,626)
Balance at Dec. 31, 2017	$ 299,238	$ 369	$ 0	$ 611,270	$ (312,340)	$ (61)
Balance (in shares) at Dec. 31, 2017		36,859,077	0

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (19,626)	$ (58,528)	$ (20,140)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization expense	7,228	7,608	2,863
Share-based compensation	14,744	12,165	7,847
Changes in operating assets and liabilities:
Accounts receivable	(10,878)	(1,540)	1,711
Prepaid expenses	332	(1,677)	2,405
Restricted cash	0	0	300
Other assets	262	276	(285)
Accounts payable	(1,544)	2,232	(163)
Accrued expenses	12,832	4,659	3,545
Lease exit liability	(1,593)	(2,822)	(3,293)
Deferred revenue	6,533	(4,191)	(12,223)
Deferred rent	6,115	(1,134)	4,650
Other liabilities	0	(727)	(878)
Net cash provided by (used in) operating activities	14,405	(43,679)	(13,661)
Cash flows from investing activities
Purchases of marketable securities	(135,122)	(347,762)	(142,910)
Proceeds from sales and maturities of marketable securities	242,401	288,894	0
Purchases of property, equipment and software	(29,403)	(11,381)	(9,197)
Net cash provided by (used in) investing activities	77,876	(70,249)	(152,107)
Cash flows from financing activities
Proceeds from issuance of common stock, net of offering costs	34,244	0	203,467
Proceeds from stock option exercises and ESPP purchases	1,144	1,893	911
Purchase of treasury stock	(40)	(39)	(29)
Net cash provided by financing activities	35,348	1,854	204,349
Net change in cash and cash equivalents	127,629	(112,074)	38,581
Cash and cash equivalents at beginning of period	84,098	196,172	157,591
Cash and cash equivalents at end of period	$ 211,727	$ 84,098	$ 196,172

Organization and Nature of Operations	12 Months Ended
Organization and Nature of Operations	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Nature of Operations	Organization and Nature of Operations MacroGenics, Inc. (the Company) was incorporated in Delaware on August 14, 2000. The Company is a biopharmaceutical company focused on discovering and developing innovative antibody-based therapeutics designed to modulate the human immune response for the treatment of cancer. The Company currently has a pipeline of product candidates in human clinical testing that have been created primarily using its proprietary technology platforms, which have broad applicability across other therapeutic domains, including autoimmune disorders and infectious disease. The Company believes its programs have the potential to have a meaningful effect on treating patients' unmet medical needs as monotherapy or, in some cases, in combination with other therapeutic agents.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The consolidated financial statements include the accounts of MacroGenics, Inc. and its wholly owned subsidiary, MacroGenics UK Limited. All intercompany accounts and transactions have been eliminated in consolidation. The Company currently operates in one operating segment. Operating segments are defined as components of an enterprise about which separate discrete information is available for the chief operating decision maker, or decision making group, in deciding how to allocate resources and assessing performance. The Company views its operations and manages its business in one segment, which is developing monoclonal antibody-based therapeutics for cancer, autoimmune and infectious diseases.

Use of Estimates

The preparation of the financial statements in accordance with generally accepted accounting principles (GAAP) requires the Company to make estimates and judgments in certain circumstances that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. In preparing these consolidated financial statements, management has made its best estimates and judgments of certain amounts included in the financial statements, giving due consideration to materiality. On an ongoing basis, the Company evaluates its estimates, including those related to revenue recognition, fair values of assets, stock-based compensation, income taxes, preclinical study and clinical trial accruals and other contingencies. Management bases its estimates on historical experience or on various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from these estimates.

Cash, Cash Equivalents and Marketable Securities

The Company considers all investments in highly liquid financial instruments with a maturity of 90 days or less at the date of purchase to be cash equivalents. Cash and cash equivalents includes investments in money market funds with commercial banks and financial institutions, securities issued by the U.S. government and its agencies, Government Sponsored Enterprise agency debt obligations and corporate debt obligations. Cash equivalents are stated at amortized cost, plus accrued interest, which approximates fair value.

The Company carries marketable securities classified as available-for-sale at fair value as determined by prices for identical or similar securities at the balance sheet date. Marketable securities consist of Level 2 financial instruments in the fair-value hierarchy. The Company records unrealized gains and losses as a component of other comprehensive loss within the statements of operations and comprehensive loss and as a separate component of stockholders' equity. Realized gains or losses on available-for-sale securities are determined using the specific identification method and the Company includes net realized gains and losses in other income (expense).

At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the unrealized loss is other-than-temporary. The Company considers factors including: the significance of the decline in value compared to the cost basis, underlying factors contributing to a decline in the prices of securities in a single asset class, the length of time the market value of the security has been less than its cost basis, the security's relative performance versus its peers, sector or asset class, expected market volatility and the market and economy in general. The Company also evaluates whether it is more likely than not that it will be required to sell a security prior to recovery of its fair value. An impairment loss is recognized at the time the Company determines that a decline in the fair value below its cost basis is other-than-temporary. There were no unrealized losses at December 31, 2017 or 2016 that the Company determined to be other-than-temporary.

Accounts Receivable

Accounts receivable that management has the intent and ability to collect are reported in the consolidated balance sheets at outstanding amounts, less an allowance for doubtful accounts. The Company writes off uncollectible receivables when the likelihood of collection is remote.

The Company evaluates the collectability of accounts receivable on a regular basis. The allowance, if any, is based upon various factors including the financial condition and payment history of customers, an overall review of collections experience on other accounts and economic factors or events expected to affect future collections experience. No allowance was recorded as of December 31, 2017 or 2016, as the Company has a history of collecting on all outstanding accounts.

Fair Value of Financial Instruments

The Company's financial instruments consist of cash and cash equivalents, marketable securities, accounts receivable, accounts payable and accrued expenses. The carrying amount of accounts receivable, accounts payable and accrued expenses are generally considered to be representative of their respective fair values because of their short-term nature. The Company accounts for recurring and non-recurring fair value measurements in accordance with the Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 820, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value, establishes a fair value hierarchy for assets and liabilities measured at fair value, and requires expanded disclosures about fair value measurements. The ASC 820 hierarchy ranks the quality of reliability of inputs, or assumptions, used in the determination of fair value and requires assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories:


•	Level 1 – Fair value is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities.

•

Level 2 – Fair value is determined by using inputs other than Level 1 quoted prices that are directly or indirectly observable. Inputs can include quoted prices for similar assets and liabilities in active markets or quoted prices for identical assets and liabilities in inactive markets. Related inputs can also include those used in valuation or other pricing models, such as interest rates and yield curves that can be corroborated by observable market data.


•	Level 3 – Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by a reporting entity – e.g., determining an appropriate adjustment to a discount factor for illiquidity associated with a given security.

The Company evaluates financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level at which to classify them each reporting period. This determination requires the Company to make subjective judgments as to the significance of inputs used in determining fair value and where such inputs lie within the ASC 820 hierarchy.

Financial assets measured at fair value on a recurring basis were as follows (in thousands):



	Fair Value Measurement at December 31, 2017
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	61,512	$	61,512	$	—	$	—
U.S Treasury securities	3,990		—		3,990		—
Government-sponsored enterprises	11,990		—		11,990		—
Corporate debt securities	78,418		—		78,418		—
Total assets measured at fair value ^(a)	$	155,910	$	61,512	$	94,398	$	—

(a) Total assets measured at fair value at December 31, 2017 includes approximately $62.5 million reported in cash and cash equivalents on the balance sheet.



	Fair Value Measurement at December 31, 2016
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	46,781	$	46,781	$	—	$	—
U.S Treasury securities	8,826		—		8,826		—
Government-sponsored enterprises	29,759		—		29,759		—
Corporate debt securities	166,300		—		166,300		—
Total assets measured at fair value ^(a)	$	251,666	$	46,781	$	204,885	$	—

(a) Total assets measured at fair value at December 31, 2016 includes approximately $50.8 million reported in cash and cash equivalents on the balance sheet.

The fair value of Level 2 securities is determined from market pricing and other observable market inputs for similar securities obtained from various third-party data providers. These inputs either represent quoted prices for similar assets in active markets or have been derived from observable market data. There were no transfers between Level 1 and Level 2 investments during the periods presented.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents, marketable securities and accounts receivable. We maintain our cash and money market funds with financial institutions that are federally insured. While balances deposited in these institutions often exceed Federal Deposit Insurance Corporation limits, we have not experienced any losses on related accounts to date. Our investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The counterparties are various corporations, financial institutions and government agencies of high credit standing.

The Company's revenue relates to agreements with various collaborators and contracts and research grants received from U.S. government agencies. The following table includes those collaborators that represent more than 10% of total revenue earned in the periods indicated:



	Year Ended December 31,
	2017	2016	2015
Incyte Corporation (Incyte)	96%	*	*
Janssen Biotech, Inc. (Janssen)	*	85%	72%
Boehringer Ingelheim GmbH (Boehringer)	*	*	12%

The following table includes those counterparties that represent more than 10% of accounts receivable at the date indicated:



	December 31,
	2017	2016
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche)	73%	*
Les Laboratoires Servier and Institut de Recherches Servier (Servier)	12%	31%
Janssen	*	40%
U.S. Government	*	19%

* Balance is less than 10%

Property, Equipment and Software

Property, equipment and software are stated at cost. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation or amortization are removed from the accounts and any resulting gain or loss is credited or charged to operations. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are computed using the straight-line method over the following estimated useful lives:



Computer equipment	3 years
Software	3 years
Furniture	10 years
Laboratory and office equipment	5 years
Leasehold improvements	Shorter of lease term or useful life

Impairment of Long-Lived Assets

The Company assesses the recoverability of its long-lived assets in accordance with the provisions of ASC 360, Property, Plant and Equipment. ASC 360 requires that long-lived assets be reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of the long-lived asset is measured by a comparison of the carrying amount of the asset to future undiscounted net cash flows expected to be generated by the asset or asset group. If carrying value exceeds the sum of undiscounted cash flows, the Company then determines the fair value of the underlying asset group. Any impairment to be recognized is measured by the amount by which the carrying amount of the asset group exceeds the estimated fair value of the asset group. Assets to be disposed of are reported at the lower of the carrying amount or fair value, less costs to sell. As of December 31, 2017 and 2016, the Company determined that there were no impaired assets and had no assets held-for-sale.

Income Taxes

Deferred tax assets and liabilities are determined based on differences between the financial reporting and tax basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that such tax rate changes are enacted. The measurement of a deferred tax asset is reduced, if necessary, by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. Financial statement recognition of a tax position taken or expected to be taken in a tax return is determined based on a more-likely-than-not threshold of that position being sustained. If the tax position meets this threshold, the benefit to be recognized is measured as the largest amount that is more likely than not to be realized upon ultimate settlement. The Company's policy is to record interest and penalties related to uncertain tax positions as a component of income tax expense.

Revenues

Revenue Recognition

The Company enters into collaboration and license agreements with collaborators for the development of monoclonal antibody-based therapeutics to treat cancer and other complex diseases. The terms of these agreements contain multiple deliverables which may include (i) licenses, or options to obtain licenses, to the Company's technological platforms, such as its Fc Optimization and DART® technologies, (ii) rights to future technological improvements, (iii) research and development activities to be performed on behalf of the collaborator or as part of the collaboration, and (iv) the manufacture of preclinical or clinical materials for the collaborator. Payments to the Company under these agreements may include nonrefundable license fees, option fees, exercise fees, payments for research and development activities, payments for the manufacture of preclinical or clinical materials, license maintenance payments, payments based upon the achievement of certain milestones and royalties on product sales. Other benefits to the Company of these agreements include the right to sell products resulting from the collaborative efforts of the parties in specific geographic territories. The Company follows the provisions of FASB ASC Topic 605-25, Revenue Recognition – Multiple-Element Arrangements, and FASB ASC Topic 605-28, Revenue Recognition–Milestone Method, in accounting for these agreements. In order to account for these agreements, the Company must identify the deliverables included within the agreement and evaluate which deliverables represent separate units of accounting based on the achievement of certain criteria, including whether the delivered element has stand-alone value to the collaborator. The consideration received is allocated among the separate units of accounting, and the applicable revenue recognition criteria are applied to each of the separate units.

For the periods presented, the Company had the following two types of agreements: 1) exclusive development and commercialization licenses to use the Company's technology and/or certain other intellectual property to develop compounds against specified targets (referred to herein as exclusive licenses); and 2) option/research agreements to secure on established terms, development and commercialization licenses to therapeutic product candidates to collaborator-selected targets developed by the Company during an option period (referred to herein as right-to-develop agreements).

There are no performance, cancellation, termination or refund provisions in any of the arrangements that contain material financial consequences to the Company.

Exclusive Licenses

The deliverables under an exclusive license agreement generally include the exclusive license to the Company's DART technology with respect to a specified antigen target, and may also include deliverables related to rights to future technological improvements, research and preclinical development activities to be performed on behalf of the collaborator. In some cases, the Company may have an option to participate in the co-development of product candidates that result from such agreements.

Generally, exclusive license agreements contain nonrefundable terms for payments and, depending on the terms of the agreement, provide that the Company will (i) at the collaborator's request, provide research and preclinical development services at negotiated prices which are generally consistent with what other third parties would charge, (ii) earn payments upon the achievement of certain milestones, (iii) earn royalty payments, and (iv) in some cases grant the Company an option to participate in the development and commercialization of products that result from such agreements. Royalty rates may vary over the royalty term depending on the Company's intellectual property rights and whether the Company exercises any co-development and co-commercialization rights. The Company does not directly control when any collaborator will achieve milestones or become liable for royalty payments.

When entering into a new collaboration arrangement or materially modifying an existing arrangement, the Company must identify the deliverables included within the agreement and evaluate which deliverables represent separate units of accounting based on the achievement of certain criteria, including whether the delivered element has stand-alone value to the collaborator. The selling prices of deliverables under an arrangement may be derived using third-party evidence (TPE), or a best estimate of selling price (BESP), if vendor specific objective evidence (VSOE) is not available. The objective of BESP is to determine the price at which the Company would transact a sale if the element within the license agreement was sold on a standalone basis. Establishing BESP involves management's judgment and considers multiple factors, including market conditions, company-specific factors, and factors contemplated in negotiating the agreements, as well as internally developed models that include assumptions related to market opportunity, discounted cash flows, estimated development costs, probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating the BESP, management considers whether changes in key assumptions used to determine the BESP will have a significant effect on the allocation of the arrangement consideration between the multiple deliverables. Deliverables under the arrangement are separate units of accounting if (i) the delivered item has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probable and substantially within the Company's control. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. The appropriate revenue recognition model is applied to each element and revenue is accordingly recognized as each element is delivered. Management exercises significant judgment in determining whether a deliverable is a separate unit of accounting.

In determining the separate units of accounting, the Company evaluates whether the exclusive license has standalone value to the collaborator based on consideration of the relevant facts and circumstances for each arrangement. Factors considered in this determination include the research and development capabilities of the collaborator and the availability of relevant research expertise in the marketplace. In addition, the Company considers whether or not (i) the collaborator could use the license for its intended purpose without the receipt of the remaining deliverables, (ii) the value of the license was dependent on the undelivered items and (iii) the collaborator or other vendors could provide the undelivered items. If the Company concludes that the license has stand-alone value and therefore will be accounted for as a separate unit of accounting, the Company then determines the estimated selling prices of the license and all other units of accounting based on market conditions, similar arrangements entered into by third parties, and entity-specific factors such as the terms of the Company's previous collaboration agreements, recent preclinical and clinical testing results of therapeutic product candidates that use the Company's technology platforms, the Company's pricing practices and pricing objectives, the likelihood that technological improvements will be made, the likelihood that technological improvements made will be used by the Company's collaborators and the nature of the research services to be performed on behalf of its collaborators and market rates for similar services. Total arrangement consideration is then allocated to each of the units of accounting using the relative-selling-price method. If facts and circumstances dictate that the exclusive license does not have stand-alone value, then the related payments are deferred and revenue is recognized throughout the period of performance.

Management reassesses the period of performance over which the Company recognizes deferred upfront license fees and makes adjustments as appropriate in the period in which a change in the estimated period of performance is identified. In the event a collaborator elects to discontinue development of a specific product candidate under a single target license, but retains its right to use the Company's technology to develop an alternative product candidate to the same target or a target substitute, the Company would cease amortization of any remaining portion of the upfront fee until there is substantial preclinical activity on another product candidate and its remaining period of substantial involvement can be estimated. In the event that a single target license was to be terminated, the Company would recognize as revenue any portion of the upfront fee that had not previously been recorded as revenue, but was classified as deferred revenue, at the date of such termination or through the remaining substantial involvement in the wind down of the agreement.

Upfront payments on exclusive licenses may be recognized upon delivery of the license if facts and circumstances dictate that the license has stand-alone value from the undelivered elements, which generally include rights to future technological improvements, research services and the manufacture of preclinical and clinical materials.

The Company recognizes revenue related to research and preclinical development services that represent separate units of accounting as they are performed, as long as there is persuasive evidence of an arrangement, the fee is fixed or determinable, and collection is reasonably assured. The Company recognizes revenue related to the rights to future technological improvements over the estimated term of the applicable license.

The Company typically performs research activities and preclinical development services, including generating and engineering product candidates, on behalf of its licensees during the early evaluation and preclinical testing stages of drug development under its exclusive licenses. The Company records amounts received for research materials produced or services performed as revenue from collaborative agreements.

The Company's license agreements have milestone payments which for reporting purposes are aggregated into three categories: (i) development milestones, (ii) regulatory milestones, and (iii) sales milestones. Development milestones are typically payable when a product candidate initiates or advances into different clinical trial phases. Regulatory milestones are typically payable upon submission for marketing approval with the U.S. Food and Drug Administration (FDA) or other countries' regulatory authorities or on receipt of actual marketing approvals for the compound or for additional indications. Sales milestones are typically payable when annual sales reach certain levels.

At the inception of each agreement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether (i) the consideration is commensurate with either (a) the entity's performance to achieve the milestone, or (b) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity's performance to achieve the milestone, (ii) the consideration relates solely to past performance and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respective milestone and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment.

Non-refundable development and regulatory milestones that are expected to be achieved as a result of the Company's efforts during the period of substantial involvement are considered substantive and are recognized as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria are met. Milestones that are not considered substantive because the Company does not contribute effort to their achievement are generally recognized as revenue upon achievement of the milestone, as there are no undelivered elements remaining and no continuing performance obligations, assuming all other revenue recognition criteria are met.

Right-to-Develop Agreements

The Company's right-to-develop agreements provide collaborators with an exclusive option to obtain licenses to develop and commercialize in specified geographic territories product candidates developed by the Company under agreed upon research and preclinical development product programs. The product candidates resulting from each program are all directed to a specific target selected by the collaborator. Under these agreements, fees may be due to the Company (i) at the inception of the arrangement (referred to as "upfront" fees or payments), (ii) the selection of a target for a program, (iii) upon the exercise of an option to acquire a development and commercialization license (referred to as exercise fees or payments earned) for a program, or (iv) some combination of all of these fees.

The accounting for right-to-develop agreements is dependent on the nature of the options granted to the collaborator. Options are considered substantive if, at the inception of a right-to-develop agreement, the Company is at risk as to whether the collaborator will choose to exercise the options to secure development and commercialization licenses. Factors that are considered in evaluating whether options are substantive include the overall objective of the arrangement, the benefit the collaborator might obtain from the agreement without exercising the options, the cost to exercise the options relative to the total upfront consideration, and the additional financial commitments imposed on the collaborator as a result of exercising the options.

For right-to-develop agreements where the options to secure development and commercialization licenses to a product program are considered substantive, the Company does not consider the development and commercialization licenses to be a deliverable at the inception of the agreement, and therefore defers any upfront payments received and recognizes this revenue over the period during which the collaborator could elect to exercise options for development and commercialization licenses. These periods are specific to each collaboration agreement. If a collaborator selects a target for a product program, any substantive option fee is deferred and recognized over the life of the option. For right-to-develop agreements that include multiple deliverables, the Company determines the selling prices of deliverables under the arrangement using TPE or a BESP, if VSOE is not available. The objective of BESP is to determine the price at which the Company would transact a sale if the element within the right-to-develop agreement was sold on a standalone basis. Establishing BESP involves management's judgment and considers multiple factors, including market conditions and company-specific factors, including those factors contemplated in negotiating the agreements, as well as internally developed models that include assumptions related to market opportunity, discounted cash flows, estimated development costs, probability of success and the time needed to commercialize a product candidate pursuant to the right-to-develop agreement. In validating the BESP, management considers whether changes in key assumptions used to determine the BESP will have a significant effect on the allocation of the arrangement consideration between the multiple deliverables. Deliverables under the arrangement are separate units of accounting if (i) the delivered item has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probable and substantially within the Company's control. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. The appropriate revenue recognition model is applied to each element and revenue is accordingly recognized as each element is delivered. Management exercises significant judgment in determining whether a deliverable is a separate unit of accounting.

If a collaborator exercises an option and acquires a development and commercialization license to a product program, the Company attributes the exercise fee to the development and commercialization license. The Company determines the selling price of the option license, upon exercise, through management's best estimate using the process for an exclusive license as described above.

Upon exercise of an option to acquire a development and commercialization license, the Company would also attribute any remaining deferred option fee, in addition to the consideration received for the license upon exercise of the option, to the development and commercialization license. The Company then applies the multiple-element revenue recognition criteria to the development and commercialization license and other deliverables, if any, to determine the appropriate revenue recognition method. This model is consistent with the Company's accounting policy for upfront payments on exclusive licenses (discussed above). In the event a right-to-develop agreement were to be terminated, the Company would recognize as revenue any portion of the upfront fee that had not previously been recorded as revenue, but was classified as deferred revenue, at the date of such termination. The Company's right-to-develop agreements have been determined to contain substantive options.

For right-to-develop agreements where the options to secure development and commercialization licenses to product programs are not considered substantive, the Company considers the development and commercialization licenses to be a deliverable at the inception of the agreement and applies the multiple-element revenue recognition criteria to determine the appropriate revenue recognition. The Company does not directly control when any collaborator will exercise its options for development and commercialization licenses.

Research and Development Costs

Research and development expenditures are expensed as incurred. Research and development costs primarily consist of employee related expenses, including salaries and benefits, expenses incurred under agreements with contract research organizations, investigative sites and consultants that conduct the Company's clinical trials, the cost of acquiring and manufacturing clinical trial materials and other allocated expenses, license fees for and milestone payments related to in-licensed products and technologies, stock-based compensation expense, and costs associated with non-clinical activities and regulatory approvals.

Right-to-develop agreements may contain cost-sharing provisions whereby the Company and the collaborator share the cost of research and development activities. Reimbursement of research and development expenses received in connection with these agreements is recorded as a reduction of such expenses.

Comprehensive Loss

Comprehensive loss represents net loss adjusted for the change during the periods attributed to unrealized gains and losses on available-for-sale securities.

Stock-based Compensation

Stock-based payments are accounted for in accordance with the provisions of ASC 718, Compensation – Stock Compensation. The fair value of stock-based payments is estimated, on the date of grant, using the Black-Scholes model. The resulting fair value is recognized ratably over the requisite service period, which is generally the vesting period of the option.

For all time-vesting awards granted, expense is amortized using the straight-line attribution method. For awards that contain a performance condition, expense is amortized using the accelerated attribution method. Recognition of stock-based compensation expense is based on the value of the portion of stock-based awards that is ultimately expected to vest during the period.

The Company utilizes the Black-Scholes model for estimating fair value of its stock options granted. Option valuation models, including the Black-Scholes model, require the input of highly subjective assumptions, and changes in the assumptions used can materially affect the grant-date fair value of an award. These assumptions include the risk-free rate of interest, expected dividend yield, expected volatility and the expected life of the award.

Net Loss Per Share

Basic loss per common share is determined by dividing loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted loss per share is computed by dividing the loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company's stock option grants.

Basic and diluted loss per common share is computed as follows (in thousands except share and per share data):



	Year Ended December 31,
	2017			2016			2015
Numerator:
Net loss used for calculation of basic and diluted EPS	$	(19,626	)	$	(58,528	)	$	(20,140	)

Denominator:
Weighted average shares outstanding, basic	36,095,080			34,685,274			31,801,645
Effect of dilutive securities:
Stock options and restricted stock units	—			—			—

Weighted average shares outstanding, diluted	36,095,080			34,685,274			31,801,645
Net loss per share, basic and diluted	$	(0.54	)	$	(1.69	)	$	(0.63	)

The following common stock equivalents were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive:



	Year Ended December 31,
	2017	2016	2015
Stock options	4,504,642	3,838,060	4,146,064

Recently Issued Accounting Standards

In May 2014, the (FASB issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017 and interim periods therein, with early adoption permitted for interim and annual reporting periods beginning after December 15, 2016. ASU 2014-09 may be adopted either retrospectively or on a modified retrospective basis whereby ASU 2014-09 would be applied to new contracts and existing contracts with remaining performance obligations as of the effective date, with a cumulative catch-up adjustment recorded to beginning retained earnings at the effective date for existing contracts with remaining performance obligations. In 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations, ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing, and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09. The effective date for these new standards is the same as the effective date and transition requirements for ASU 2014-09. The Company will adopt the new standard in the first quarter of 2018 using the modified retrospective method.

The Company has substantially completed extensive contract specific reviews to determine the impact of the new standard on its historical and prospective revenue recognition. Due to the unique contract terms of certain agreements, the Company is still in the process of finalizing its analysis of those agreements. Upon completion of the Company’s analysis, it will determine the cumulative effect of initially applying the new standard (if any). The Company is also finalizing its accounting policy and designing and implementing the necessary changes to processes and controls to account for revenue under the new standard. Based on the Company's timeline and planned resources, the Company anticipates completing its implementation in connection with its first quarter 2018 interim financial statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02) that provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. ASU 2016-02 includes a short-term lease exception for leases with a term of 12 months or less, in which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases, using classification criteria that are substantially similar to the previous guidance. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with earlier application permitted. Entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. The Company is currently evaluating the effect of the standard on its consolidated financial statements and related disclosures.

In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This amendment addresses several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within that year. The Company adopted ASU 2016-09 effective January 1, 2017 and has elected to continue to estimate the number of stock-based awards expected to vest, as permitted by ASU 2016-09, rather than electing to account for forfeitures as they occur. The adoption of this standard did not have a material impact on the Company's financial statements or related disclosures.

The Company has evaluated all other ASUs issued through the date the consolidated financials were issued and believes that the adoption of these will not have a material impact on the Company's consolidated financial statements.

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (the Tax Act) was signed into law making significant changes to the Internal Revenue Code, which included how the U.S. imposes income tax on multinational corporations. Key changes in the Tax Act which are relevant to us, and generally effective January 1, 2018, include a flat corporate income tax rate of 21% to replace the marginal rates that range from 15% to 35% and the elimination of the corporate alternative minimum tax. The Tax Act also imposes limits on executive compensations and interest expense deductions, while permitting the immediate expensing for the cost of new investments in certain property acquired after September 27, 2017.

On December 22, 2017, the SEC issued Staff Accounting Bulletin No. 118 (SAB 118) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. SAB 118 allows registrants to include a provisional amount to account for the implications of the Tax Act where a reasonable estimate can be made and requires the completion of the accounting no later than one year from the date of the enactment of the Tax Act, or December 22, 2018.

ASC 740 requires changes in tax rates and tax laws to be accounted for in the period of enactment in continuing operations. Accordingly, of significance, we recorded a provisional estimate for the re-measurement of our U.S. deferred tax assets and liabilities to 21%. This change in value of these deferred tax assets and liabilities, which is provisional, was offset by a corresponding change in our valuation allowance, thus no tax expense or benefit was recorded. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional information necessary to complete the computation and analysis thereof, additional regulatory guidance that may be issued, and actions we may take as a result of the Tax Act. The accounting is expected to be complete by December 22, 2018.

Marketable Securities

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Available-for-sale marketable securities as of December 31, 2017 and 2016 were as follows (in thousands):



	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	3,995	$	—	$	(6	)	$	3,989
Government-sponsored enterprises	11,998		—		(7		)	11,991
Corporate debt securities	77,462		2		(50		)	77,414
Total	$	93,455	$	2	$	(63	)	$	93,394



	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	4,826	$	—	$	(1	)	$	4,825
Government-sponsored enterprises	29,764		5		(10		)	29,759
Corporate debt securities	166,376		51		(127		)	166,300
Total	$	200,966	$	56	$	(138	)	$	200,884

All of the Company's available-for-sale securities held at December 31, 2017 had maturity dates of less than one year. The contractual maturities of the available-for-sale marketable securities as of December 31, 2016 were as follows (in thousands):



	Amortized Cost		Fair Value
Mature in one year or less	$	192,985	$	192,898
Mature between one and five years	7,981		7,986
Total	$	200,966	$	200,884

All available-for-sale securities in an unrealized loss position as of December 31, 2017 and 2016 were in a loss position for less than twelve months. There were no unrealized losses at December 31, 2017 or 2016 that the Company determined to be other-than-temporary. The Company recorded interest income of $2.4 million, $2.3 million and $0.2 million during the years ended December 31, 2017, 2016 and 2015, respectively, which is included in other income.

Property, Equipment and Software

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Equipment and Software

Property, equipment and software consists of the following (in thousands):



	December 31,
	2017			2016
Computer equipment	$	2,261		$	2,520
Software	5,111			2,352
Furniture and office equipment	656			897
Lab equipment	20,549			20,208
Leasehold improvements	17,525			17,807
Construction in progress	32,800			—
Property, equipment and software	78,902			43,784
Less accumulated depreciation and amortization	(28,919		)	(25,823		)
Property, equipment and software, net	$	49,983		$	17,961

Construction in progress at December 31, 2017 consists of the costs incurred for the build-out of a manufacturing suite at our headquarters building in Rockville, Maryland, which is expected to be completed in mid-2018.

We had $9.6 million in property, equipment and software at December 31, 2017 that was purchased in 2017 but was not paid for by year end. Property, equipment and software balance at December 31, 2016 includes approximately $0.3 million in assets that were purchased in 2016 but were not paid for by year end. Depreciation and amortization expense related to property, equipment and software for the years ended December 31, 2017, 2016 and 2015 was $7.0 million, $6.8 million and $3.2 million, respectively.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity The Company's amended and restated certificate of incorporation authorizes 125,000,000 shares of common stock, and 5,000,000 shares of undesignated preferred stock, both with a par value of $0.01 per share. There were no shares of undesignated preferred stock issued or outstanding as of December 31, 2017 or 2016. In February 2014, the Company completed an equity offering, in which the Company sold 1,800,000 shares of its common stock at a price of $36.50 per share. Additionally, the underwriters of the offering exercised the full amount of their over-allotment option resulting in the sale of an additional 450,000 shares of the Company's common stock at a price of $36.50 per share. The Company received proceeds of $76.7 million from this offering, net of underwriting discounts and commissions and other offering expenses. In January 2015, the Company's stock purchase agreement and investor agreement, each with Johnson & Johnson Innovation – JJDC, Inc. (JJDC) became effective (see Note 9 for additional information). Under these agreements, JJDC purchased 1,923,077 new shares of the Company's common stock at a price of $39.00 per share, representing proceeds of $75.0 million. In July 2015, the Company completed an equity offering, in which the Company sold 3,525,000 shares of its common stock at a price of $37.00 per share. Additionally, the underwriters of the offering exercised the full amount of their over-allotment option resulting in the sale of an additional 528,750 shares of the Company's common stock at a price of $37.00 per share. The Company received net proceeds of $141.0 million from this offering, net of underwriting discounts and commissions and other estimated offering expenses. On April 26, 2017, the Company entered into a definitive agreement with an institutional healthcare investor to purchase 1,100,000 shares of its common stock at a purchase price of $21.50 per share in a registered direct offering. Proceeds to the Company, before deducting estimated offering expenses, were $23.7 million. The shares were offered pursuant to the Company’s effective shelf registration on Form S-3 that was filed with the SEC on November 2, 2016. On May 3, 2017, the Company entered into a sales agreement with an agent to sell, from time to time, shares of its common stock having an aggregate sales price of up to $75.0 million through an “at the market offering” (ATM Offering) as defined in Rule 415 under the Securities Act of 1933, as amended. The shares that may be sold under the sales agreement would be issued and sold pursuant to the Company's shelf registration statement on Form S-3 that was filed with the SEC on November 2, 2016. During the year ended December 31, 2017, the Company sold 599,284 shares of common stock resulting in net proceeds of $10.8 million related to the ATM Offering.

Stock-based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation

Employee Stock Purchase Plan

In May 2017, the Company’s stockholders approved the 2016 Employee Stock Purchase Plan (the 2016 ESPP). The 2016 ESPP is structured as a qualified employee stock purchase plan under Section 423 of the Internal Revenue Code of 1986, as amended, and is not subject to the provisions of the Employee Retirement Income Security Act of 1974. The Company reserved 800,000 shares of common stock for issuance under the 2016 ESPP. The 2016 ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 10% of their eligible compensation, subject to any plan limitations. The 2016 ESPP provides for six-month offering periods ending on May 31 and November 30 of each year. At the end of each offering period, employees are able to purchase shares at 85% of the fair market value of the Company’s common stock on the last day of the offering period. During the year ended December 31, 2017, employees purchased 38,012 shares of common stock under the 2016 ESPP for net proceeds to the Company of approximately $0.6 million.

Employee Stock Option Plans

Effective February 2003, the Company implemented the 2003 Equity Incentive Plan (2003 Plan), and it was amended and approved by the Company's stockholders in 2005. The 2003 Plan originally allowed for the grant of awards in respect of an aggregate of 2,051,644 shares of the Company's common stock. Between 2006 and 2012, the maximum number of shares of common stock authorized to be issued by the Company under the 2003 Plan was increased to 4,336,730. Stock options granted under the 2003 Plan may be either incentive stock options as defined by the Internal Revenue Code (IRC), or non-qualified stock options. In 2013, the 2003 Plan was terminated, and no further awards may be issued under the plan. Any shares of common stock subject to awards under the 2003 Plan that expire, terminate, or are otherwise surrendered, canceled, forfeited or repurchased without having been fully exercised, or resulting in any common stock being issued, will become available for issuance under the 2013 Stock Incentive Plan (2013 Plan), up to a specified number of shares. As of December 31, 2017, under the 2003 Plan, there were options to purchase an aggregate of 955,296 shares of common stock outstanding at a weighted average exercise price of $1.85 per share.

In October 2013, the Company implemented the 2013 Plan. The 2013 Plan provides for the grant of stock options and other stock-based awards, as well as cash-based performance awards. The aggregate number of shares of common stock initially available for issuance pursuant to awards under the 2013 Plan was 1,960,168 shares. The number of shares of common stock reserved for issuance will automatically increase on January 1 of each year from January 1, 2014 through and including January 1, 2023, by the lesser of (a) 1,960,168 shares, (b) 4.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or (c) the number of shares of common stock determined by the Board of Directors. During the year ended December 31, 2017, the maximum number of shares of common stock authorized to be issued by the Company under the 2013 Plan was increased to 6,769,888. If an option expires or terminates for any reason without having been fully exercised, if any shares of restricted stock are forfeited, or if any award terminates, expires or is settled without all or a portion of the shares of common stock covered by the award being issued, such shares are available for the grant of additional awards. However, any shares that are withheld (or delivered) to pay withholding taxes or to pay the exercise price of an option are not available for the grant of additional awards. As of December 31, 2017, under the 2013 Plan, there were options to purchase an aggregate of 3,549,346 shares of common stock outstanding at a weighted average exercise price of $24.62 per share.

The following stock-based compensation amounts were recognized for the periods indicated (in thousands):



	Year Ended December 31,
	2017		2016		2015

Research and development	$	7,388	$	5,778	$	3,623
General and administrative	7,356		6,387		4,224
Total stock-based compensation expense	$	14,744	$	12,165	$	7,847

Employee Stock Options

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model using the assumptions in the following table:



	Year Ended December 31,
	2017	2016	2015
Expected dividend yield	0%	0%	0%
Expected volatility	67% - 68%	64% - 69%	73% - 75%
Risk-free interest rate	1.9% - 2.3%	1.2% - 2.4%	1.6% - 2.1%
Expected term	6.25 years	6.25 years	6.25 years

Expected Dividend Yield – The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Expected Volatility – Volatility is a measure of the amount by which a financial variable such as a share price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. As the Company does not yet have sufficient history of its own volatility, the Company has identified several public entities of similar size, complexity and stage of development and estimates volatility based on the volatility of these companies.

Risk-Free Interest Rate – This is the U.S. Treasury rate for the week of each option grant during the year, having a term that most closely resembles the expected life of the option.

Expected Term – This is the period of time that the options granted are expected to remain unexercised. Options granted have a maximum term of ten years. The Company uses a simplified method to calculate the average expected term.

In addition to the assumptions above, the Company estimates the forfeiture rate based on turnover data with further consideration given to the class of the employees to whom the options were granted. The forfeiture rate is the estimated percentage of options granted that is expected to be forfeited or canceled on an annual basis before becoming fully vested.

The following table summarizes stock option and restricted stock unit (RSU) activity for 2017:



	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	3,838,060		$	18.93	7.0
Granted	1,246,225		20.05
Options exercised or RSUs vested	(253,036	)	2.16
Forfeited or expired	(326,607	)	24.26
Outstanding, December 31, 2017	4,504,642		19.79		7.0	$	18,343

December 31, 2017:
Exercisable	2,910,171		17.65		6.1	17,495
Vested and expected to vest	4,337,015		19.60		6.9	18,275

During 2017, 2016 and 2015 the Company issued 253,036, 526,715 and 374,214 net shares of common stock, respectively, in conjunction with stock option exercises and RSU lapses. The Company received cash proceeds from the exercise of stock options of approximately $0.5 million, $1.9 million and $0.9 million during 2017, 2016 and 2015, respectively.

The weighted-average grant-date fair value of options granted during 2017, 2016 and 2015 was $12.53, $15.17 and $20.90 per share, respectively. The total intrinsic value of options exercised during 2017, 2016 and 2015 was approximately $4.2 million, $10.8 million and $10.9 million, respectively. The total fair value of stock options which vested during 2017, 2016 and 2015 was $14.6 million, $11.6 million and $7.3 million, respectively. As of December 31, 2017, the total unrecognized compensation expense related to non-vested stock options and RSUs, net of related forfeiture estimates, was $20.3 million, which the Company expects to recognize over a weighted-average period of approximately 2.3 years.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

For the years ended December 31, 2017, 2016 and 2015 there was no provision for income taxes due to taxable losses generated, fully offset by a valuation allowance.

The significant components of the Company's deferred income tax assets (liabilities) were as follows (in thousands):



	December 31,
	2017			2016
Deferred income tax assets:
Federal U.S. net operating loss carryforward	$	50,346		$	75,377
State net operating loss carryforward	7,551			6,583
Research and development credit, net	21,284			12,829
Orphan drug credit, net	21,708			19,855
Deferred rent	3,385			2,497
Deferred revenue	2,982			5,098
Depreciation	155			2,926
Other	5,847			5,085
Gross deferred income tax assets	113,258			130,250
Valuation allowance	(112,453		)	(128,844		)
Net deferred income tax assets	805			1,406

Deferred income tax liabilities:
Prepaid expenditures	(805		)	(1,406		)
Gross deferred income tax liabilities	(805		)	(1,406		)
Net deferred income tax asset/(liability)	$	—		$	—

The Company recognizes valuation allowances to reduce deferred tax assets to the amount that is more likely than not to be realized. In assessing the likelihood of realization, management considers (i) future reversals of existing taxable temporary differences; (ii) future taxable income exclusive of reversing temporary difference and carryforwards; (iii) taxable income in prior carryback years if carryback is permitted under applicable tax law; and (iv) tax planning strategies. The Company's net deferred income tax asset is not more likely than not to be utilized due to the lack of sufficient sources of future taxable income and cumulative book losses which have resulted over the years. The net decrease in the valuation allowance in 2017 is primarily as a result of the legislation enacted in 2017, which lowers the statutory corporate tax rate from 35% to 21%,, which decreased the net deferred tax asset.

As of December 31, 2017, the Company has U.S. federal and state NOL carryforwards of approximately $239.7 million that will expire in various years beginning in 2025 through 2037. In addition, the Company has U.S. federal tax credits of $42.8 million which will expire in various years beginning in 2025 through 2037.

The use of the Company's U.S. federal NOL and tax credit carryforwards in future years are restricted due to changes in the Company's ownership and tax attributes acquired through the Company's acquisitions. As of December 31, 2017, $13.5 million of the Company's U.S. Federal NOLs are limited for use over the years 2018 – 2028 in which a range of such amounts could be utilized on an annual basis of $0.2 million to $1.4 million. The remaining $226.2 million of NOLs is not limited and can be offset against future taxable income, subject to certain limitations for newly enacted tax legislation. The Company adopted ASU 2016-09 as of January 1, 2017. Accordingly, the Company recognized the previously unrecognized excess tax benefits of approximately $18.6 million ($6.5 million tax effected) recorded as deferred tax assets with a corresponding offsetting full valuation allowance at the beginning of 2017 without any tax impact. Further, despite the NOL and tax credit carryforwards, the Company may have a future tax liability due to recent changes in tax legislation or state tax requirements in which net operating losses do not exist. The Company is still quantifying the impact of these changes.

The reconciliation of the reported estimated income tax benefit to the amount that would result by applying the U.S. federal statutory tax rate to the net income is as follows (in thousands):



	Year Ended December 31,
	2017			2016			2015

United States federal tax at statutory rate	$	(6,869	)	$	(20,489	)	$	(7,049	)
State taxes (net of federal benefit)	(735		)	(3,116		)	(897		)
Deferred income tax adjustments	607			173			661
Deferred state blended rate adjustments	(485		)	(32		)	(493		)
Deferred federal rate change reduction in corporate rate	39,447			—			—
Research credit, net	(8,455		)	(2,551		)	(3,296		)
Orphan drug credit, net	(1,853		)	(571		)	(106		)
Other permanent items	276			145			(25		)
Equity-based compensation	2,067			1,997			1,102
Change in valuation allowance	(24,000		)	24,444			10,103
Income tax expense/(benefit)	$	—		$	—		$	—

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in thousands):



	Year Ended December 31,
	2017		2016			2015
Beginning balance	$	2,465	$	2,425		$	2,047
Increases for current year tax positions	569		308			357
Increases/(decreases) for prior year tax positions	361		(268		)	21
Ending balance	$	3,395	$	2,465		$	2,425

As of December 31, 2017 and 2016, of the total gross unrecognized tax benefits, approximately $3.4 million and $2.4 million would favorably impact the Company's effective income tax rate, respectively. Although, due to the Company's determination that the deferred income tax asset would not more likely than not be realized, a valuation allowance would be recorded, therefore, zero net impact would result within the Company's effective income tax rate. The Company's uncertain income tax position liability has been recorded to deferred income taxes to offset the tax attribute carryforward amounts.

For the years ended December 31, 2017, 2016 and 2015, the Company has not recognized any interest or penalties related to the uncertain income tax positions due to the fact such position is related to tax attribute carryforwards which have not yet been utilized. The Company does not expect its unrecognized income tax position to significantly decrease within the next twelve months.

The Company's U.S. Federal and state income tax returns from 2001 forward remain open to examination due to the carryover of unused net operating losses and tax credits.

As more fully described in Note 2 to the consolidated financial statements, the Tax Act was signed into law making significant changes to the Internal Revenue Code on December 22, 2017. Under ASC 740-10-25-47, the effects of the new legislation are to be recognized in the period of enactment. As such, recognition of the tax impact of the Tax Act is required in the interim and annual periods that include December 22, 2017. As a result, the Company has revalued the deferred tax asset as of December 31, 2017, fully offset by a valuation allowance without impact to the financial statements. The Company does not anticipate that other provisions of the Act would have a material impact on its financial statements.

Lease Exit Liability

12 Months Ended

Dec. 31, 2017

Restructuring and Related Activities [Abstract]

Lease Exit Liability

In 2008, the Company acquired Raven Biotechnologies, Inc. (Raven), a private South San Francisco-based company focused on the development of monoclonal antibody therapeutics for treating cancer. The Company undertook restructuring activities related to the acquisition of Raven. In connection with these restructuring activities, as part of the cost of acquisition, the Company established a restructuring liability attributed to an existing operating lease. During the year ended December 31, 2016, the Company entered into an agreement to sublease a portion of the space subject to this operating lease. The Company will receive approximately $1.3 million in sublease payments over its term, which ends at the same time as the original lease in February 2018. No sublease income was contemplated when the restructuring liability was recorded in 2008; therefore, the Company adjusted the liability to reflect the future sublease income during the year ended December 31, 2016 and recorded an offset to research and development expense of approximately $1.3 million in the same period.

Changes in the lease exit liability are as follows (in thousands):



Accrual balance at December 31, 2015	$	4,713
Principal payments and other adjustments	(2,822		)
Accrual balance at December 31, 2016	1,891
Principal payments and other adjustments (net of sublease receipts)	(1,593		)
Accrual balance at December 31, 2017	$	298

During 2015, the Company corrected an immaterial error attributed to the estimated lease term that resulted in a reduction of research and development expense of $1.9 million.

Collaboration and Other Agreements	12 Months Ended
Collaboration and Other Agreements	Dec. 31, 2017
Collaboration and License Agreements [Abstract]
Collaboration and Other Agreements	Collaboration and Other Agreements Incyte In October 2017, the Company entered into an exclusive global collaboration and license agreement with Incyte Corporation (Incyte) for MGA012, an investigational monoclonal antibody that inhibits programmed cell death protein 1 (PD-1). Incyte has obtained exclusive worldwide rights for the development and commercialization of MGA012 in all indications, while the Company retains the right to develop its pipeline assets in combination with MGA012. The Company received a $150.0 million upfront payment from Incyte when the transaction closed in the fourth quarter of 2017. Under the terms of the collaboration and license agreement, Incyte will lead global development of MGA012. Assuming successful development and commercialization by Incyte, the Company could receive up to approximately $420.0 million in development and regulatory milestones, and up to $330.0 million in commercial milestones. The Company determined that each potential future clinical and regulatory milestone is substantive. Although the sales milestones are not considered substantive, they will be recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. If commercialized, the Company would be eligible to receive tiered royalties of 15% to 24% on any global net sales. The Company retains the right to develop its pipeline assets in combination with MGA012, with Incyte commercializing MGA012 and the Company commercializing its asset(s), if any such potential combinations are approved. In addition, the Company retains the right to manufacture a portion of both companies' global clinical and commercial supply needs of MGA012. The Company and Incyte have agreed to initiate negotiations for a separate clinical supply agreement that will set forth terms and conditions. Finally, Incyte will fund the Company's activities related to the ongoing monotherapy clinical study until such time as the Company can transfer the Investigational New Drug application (IND) to Incyte. The Company evaluated the collaboration and license agreement with Incyte and determined that it is a revenue arrangement with multiple deliverables, or performance obligations. The Company’s substantive performance obligations under the collaboration and license agreement include the delivery of the license and clinical activities through a brief technology transfer period. The Company evaluated the collaboration and license agreement with Incyte and determined that the license and clinical trial activities each represented separate deliverables and were accounted for as separate units of accounting. The Company concluded that the license had standalone value to Incyte and was separable from the clinical trial activities because the license was sublicensable and Incyte has significant capabilities in performing clinical trials. Thus, the total arrangement consideration for these two deliverables was allocated using the relative best estimate of selling price (BESP) to each deliverable. The BESP for the exclusive license was determined using information from other similar collaboration and license agreements. The BESP for the clinical trial activities was determined using similar arrangements and is estimated at approximately $4.0 million, which will be recognized over the technology transfer period as work is performed and the expenses are reimbursed by Incyte. The Company recognized revenue of $151.1 million under the Incyte collaboration and license agreement during the year ended December 31, 2017, including the $150.0 million upfront payment and $1.1 million related to clinical trial activities performed. Roche In December 2017, the Company entered into a research collaboration and license agreement with Roche to jointly discover and develop novel bispecific molecules to undisclosed targets. During the research term, both companies will leverage their respective platforms, including the Company's DART platform and Roche's CrossMAb and DutaFab technologies to select a bispecific format and lead product candidate. Roche would then further develop and commercialize any such product candidate. Under the terms of this agreement, Roche received rights to use certain of the Company’s intellectual property rights to exploit collaboration compounds and products, and paid the Company an upfront payment of $10.0 million which was received in January 2018. The Company will also be eligible to receive up to $370.0 million in potential milestone payments and royalties on future sales. The Company evaluated the research collaboration and license agreement with Roche and determined that it is a revenue arrangement with multiple deliverables, or performance obligations. The Company’s substantive performance obligations under the research collaboration and license agreement include the delivery of the license and activities during the research period. The Company evaluated the collaboration and license agreement with Roche and determined that the license and research activities do not have value on a standalone basis and therefore represented one unit of accounting. The $10.0 million will be recognized over the expected research period, which is 30 months. Each company will be responsible for their own expenses during the research period. In addition, the Company determined that each potential future development and regulatory milestone is substantive. Although sales milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. At December 31, 2017, $10.0 million of revenue was deferred under this agreement, $4.0 million of which was current and $6.0 million of which was non-current. Janssen In December 2014, the Company entered into a collaboration and license agreement with Janssen for the development and commercialization of MGD011 (also known as JNJ-64052781 or duvortuxizumab), a product candidate that incorporates the Company's proprietary DART technology to simultaneously target CD19 and CD3 for the potential treatment of B-cell hematological malignancies (MGD011 Agreement). The Company contemporaneously entered into an agreement with JJDC under which JJDC agreed to purchase 1,923,077 new shares of the Company's common stock for proceeds of $75.0 million. Upon closing the transaction in January 2015, the Company received a $50.0 million upfront payment from Janssen as well as the $75.0 million investment in the Company's common stock. In August 2017, Janssen notified the Company that they were terminating the MGD011 Agreement. Under the MGD011 Agreement, the Company granted an exclusive license to Janssen to develop and commercialize duvortuxizumab. Following the Company's submission of the Investigational New Drug (IND) application, Janssen became fully responsible for the development and commercialization of duvortuxizumab. At the inception of the MGD011 Agreement, the Company evaluated it and determined that it was a revenue arrangement with multiple deliverables, or performance obligations. The Company's substantive performance obligations under the collaboration and license agreement included the delivery of an exclusive license and research and development services during the preclinical research period (through the filing of the IND for duvortuxizumab). The Company evaluated the MGD011 Agreement and determined that the license and preclinical research and development activities each represented separate deliverables and were accounted for as separate units of accounting. The Company concluded that the license had standalone value to Janssen and was separable from the research and development services because the license was sublicensable, there were no restrictions as to Janssen's use of the license and Janssen or other third parties have significant research capabilities in this field. Thus, the total arrangement consideration for these two deliverables was allocated using the relative BESP method to each deliverable. The BESP for the exclusive license was determined using a discounted cash flow model that includes Level 3 fair value measurements. The BESP for the research and development services was determined using third party evidence of other similar research and development arrangements, which are Level 2 fair value measurements. The Company evaluated the stock purchase agreement and the collaboration and license agreement as one arrangement and determined that the stock purchase price of $39.00 per share exceeded the fair value of the common stock by $12.3 million. This excess was recognized in the same manner as the upfront payment allocated to the license and preclinical research and development activities. Of the total arrangement consideration of $125.0 million, the Company allocated $62.7 million to equity (representing the fair value of common stock purchased), $62.3 million to the license and preclinical research and development activities, and a de minimis amount to the ongoing research and development activities. The Company submitted the IND application and therefore met its performance obligation during the year ended December 31, 2015. In July 2015, Janssen dosed the first patient in an open-label Phase 1 study of duvortuxizumab which triggered a $10.0 million milestone to the Company. No revenue was recognized under the MGD011 Agreement during the year ended December 31, 2017. During the years ended December 31, 2016 and 2015, the Company recognized revenue of approximately $2.0 million and $72.3 million, respectively, under the MGD011 agreement. In May 2016, the Company entered into a separate collaboration and license agreement with Janssen, a related party through ownership of the Company's common stock, for the development and commercialization of MGD015, a product candidate that incorporates the Company's proprietary DART technology to simultaneously target CD3 and an undisclosed tumor target for the potential treatment of various hematological malignancies and solid tumors (MGD015 Agreement). Under the MGD015 Agreement, the Company granted an exclusive license to Janssen to develop and commercialize MGD015. The Company received a $75.0 million upfront payment from Janssen upon closing the transaction. In January 2018, Janssen notified the Company that they were terminating the MGD015 Agreement. At the inception of the MGD015 Agreement, the Company evaluated it and determined that it was a revenue arrangement with multiple deliverables, or performance obligations. The Company's substantive performance obligations under the MGD015 Agreement included the delivery of an exclusive license and research and development services during the preclinical research period. The Company evaluated the MGD015 Agreement with Janssen and determined that the license and preclinical research and development activities each represented separate deliverables and were accounted for as two separate units of accounting. The Company concluded that the license had standalone value to Janssen and was separable from the research and development services because the license was sublicensable, there were no restrictions as to Janssen's use of the license and Janssen or other third parties have significant research capabilities in this field. Thus, the total arrangement consideration for these two deliverables was allocated using the BESP method to each deliverable. The BESP for the exclusive license was determined using information from the previous collaboration and license agreement with Janssen as well as other third party collaboration and license agreements, which are Level 2 fair value measurements. The BESP for the research and development services was determined using other similar research and development arrangements, which are also Level 2 fair value measurements. During the years ended December 31, 2017 and 2016, the Company recognized revenue of $0.6 million and $75.8 million, respectively, under the MGD015 Agreement. Revenue recognized in 2016 included the $75.0 million upfront fee for the exclusive license. Takeda In May 2014, the Company entered into a license and option agreement with Takeda for the development and commercialization of MGD010, a product candidate that incorporates the Company's proprietary DART technology to simultaneously engage CD32B and CD79B, which are two B-cell surface proteins. MGD010 is being developed for the treatment of autoimmune disorders. Upon execution of the agreement, Takeda made a non-refundable payment of $15.0 million to the Company. Takeda had an option to obtain an exclusive worldwide license for MGD010 following the completion of a pre-defined Phase 1a study. Following the announcement of its therapeutic area re-prioritization, Takeda gave formal notification in September 2016 that it did not intend to exercise this option. As a result of Takeda not exercising the option, the Company regained worldwide development and commercialization rights to MGD010. At the inception of the license and option agreement with Takeda, the Company evaluated it and determined that it was a revenue arrangement with multiple deliverables, or performance obligations. The Company's substantive performance obligations under the license and option agreement included exclusivity, research and development services through the Phase 1a study and delivery of a future license for an initial research compound. The Company concluded that the MGD010 option was substantive and that the license fee payable upon exercise of the option was not a deliverable at the inception of the arrangement as there was considerable uncertainty that the option would be exercised. The Company determined that each potential future clinical and regulatory milestone was substantive. Although sales milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. The Company determined that these performance obligations represent a single unit of accounting, because the exclusivity clause does not have stand-alone value to Takeda without the Company's technical expertise and development through the pre-defined Phase 1a study. After identifying the deliverables included within the arrangement, the Company determined its best estimate of selling price. The Company allocated $10.0 million to the exclusivity clause to its technology and the research and development services and $5.0 million to the exclusive license for the initial research compound. The Company's determination of best estimate of selling price for the research and development services relied upon other similar transactions. The Company relied upon the income approach (e.g., discounted future cash flows) to determine the value of the license of the to-be-delivered compound along with other similar license transactions with differing indications but similar stage of development. The portion of the up-front fee allocated to the MGD010 option was being recognized over an initial 24-month period, which represented the expected period of development through the completion of a pre-defined Phase 1a study. During the first quarter of 2016, the Company determined that the development period would be extended by eight months, and prospectively adjusted the MGD010 option fee recognition period. The portion of the up-front fee allocated to the license for the initial research compound was deferred until the research collaboration and license option agreement was executed and the license delivered in September 2014. Upon the notification that Takeda would not exercise the option to obtain an exclusive worldwide license for MGD010 during the three months ended September 30, 2016, the Company's performance obligation to Takeda ceased, and the remaining deferred revenue under the MGD010 agreement was recognized in full. No revenue under was recognized under this agreement during the year ended December 31, 2017. The Company recognized revenue of approximately $2.1 million and $8.0 million under the MGD010 agreement during the years ended December 31, 2016 and 2015, respectively. Revenue recognized during the year ended December 31, 2015 included a $3.0 million milestone payment received upon initiation of a Phase 1a trial of MGD010. No revenue was deferred under this agreement at December 31, 2017 or 2016. Servier In September 2012, the Company entered into a right-to-develop collaboration agreement with Servier and granted it options to obtain three separate exclusive licenses to develop and commercialize DART molecules, consisting of those designated by the Company as MGD006 (or flotetuzumab) (also known as S80880) and MGD007, as well as a third DART molecule, in all countries other than the United States, Canada, Mexico, Japan, South Korea and India. During 2014, Servier exercised its exclusive option to develop and commercialize flotetuzumab, and during 2016 Servier notified the Company that it did not intend to exercise the option for the third DART molecule. Servier retains the option to obtain a license for MGD007. Upon execution of the agreement, Servier made a nonrefundable payment of $20.0 million to the Company. In addition, the Company will be eligible to receive up to $40.0 million in license fees, $63.0 million in clinical milestone payments, $188.0 million in regulatory milestone payments and $420.0 million in sales milestone payments if Servier exercises the remaining available options and successfully develops, obtains regulatory approval for, and commercializes a product under each license. In addition to these milestones, the Company and Servier will share Phase 2 and Phase 3 development costs. The Company has determined that each potential future clinical and regulatory milestone is substantive. Although sales milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. Under this agreement, Servier would be obligated to pay the Company from low double-digit to mid-teen royalties on net product sales in its territories. The Company evaluated the research collaboration agreement with Servier and determined that it is a revenue arrangement with multiple deliverables, or performance obligations. The Company concluded that each option is substantive and that the license fees for each option are not deliverables at the inception of the arrangement and were not issued with a substantial discount. The Company's substantive performance obligations under this research collaboration include an exclusivity clause to its technology, technical, scientific and intellectual property support to the research plan and participation on an executive committee and a research and development committee. The Company determined that the performance obligations with respect to the preclinical development represent a single unit of accounting, since the license does not have stand-alone value to Servier without the Company's technical expertise and committee participation. As such, the initial upfront license payment was deferred and initially recognized ratably over a 29-month period, which represented the expected development period. During 2014, the Company and Servier further refined the research plan related to the three DART molecules and as such, the development period was extended. Based on this revised development period, the Company prospectively adjusted its period of recognition of the upfront payment to a 75-month period. The impact of this change in accounting estimate reduced revenue that would have been recognized in 2014 by $3.7 million. As a result of Servier exercising its option in 2014, the Company received a $15.0 million payment from Servier for its license to develop and commercialize flotetuzumab in its territories. Upon exercise of the option, the Company evaluated its performance obligations with respect to the license for flotetuzumab. The Company's substantive performance obligations under this research collaboration include an exclusive license to its technology, technical, scientific and intellectual property support to the research plan and participation on an executive committee and a research and development committee. The Company determined that the performance obligations with respect to the clinical development represent a single unit of accounting, since the license does not have stand-alone value to Servier without the Company's technical expertise and committee participation. As such, the $15.0 million license fee was deferred and was being recognized ratably over a period of 82 months, which represented the expected development period for flotetuzumab. During the year ended December 31, 2017, the Company and Servier determined that the expected development period should be extended to 124 months. The impact of this change in accounting estimate reduced revenue that would have been recognized in 2017 by $0.8 million. In accordance with the agreement, the Company and Servier will share costs incurred to develop flotetuzumab. Reimbursement of research and development expenses received in connection with this collaborative cost-sharing agreement is recorded as a reduction to research and development expense. During the years ended December 31, 2017, 2016 and 2015 the Company recorded approximately $3.2 million, $2.6 million and $0.5 million as an offset to research and development costs under this collaboration arrangement, respectively. During the years ended December 31, 2017, 2016 and 2015 the Company recognized revenue of $2.5 million, $3.3 million, and $3.5 million, respectively, under this agreement. At December 31, 2017, $8.5 million of revenue was deferred under this agreement, $2.3 million of which was current and $6.2 million of which was non-current. At December 31, 2016, $11.1 million of revenue was deferred under this agreement, $3.3 million of which was current and $7.8 million of which was non-current. Boehringer In October 2010 the Company entered into a collaboration and license agreement with Boehringer to discover, develop and commercialize multiple DART molecules that were to be evaluated during a five-year period that ended in October 2015. Under the terms of the agreement, the Company granted Boehringer an exclusive, worldwide, royalty-bearing, license under its intellectual property to research, develop, and market DART molecules generated under the agreement. Upon execution of the agreement, the Company received an upfront payment of $15.0 million. The Company subsequently received three annual maintenance payments. These maintenance payments were being recognized over the estimated period of development. The Company has the potential to earn additional milestone payments of approximately $34.0 million related to preclinical and clinical development, $88.5 million related to regulatory milestones and $82.5 million related to sales milestones for each of the two ongoing programs under this agreement. The Company determined that each potential future preclinical, clinical and regulatory milestone is substantive. Although sales milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. Boehringer would be required to pay the Company mid-single digit royalties on product sales. The Company determined that the deliverables under the Boehringer agreement include the license, the research and development services to be performed by the Company, and the co-promotion/manufacturing services. The Company concluded that the co-promotional activities were optional and were subject to further negotiation upon reaching regulatory approval. As such, the co-promotional period is not included in the expected obligation period to perform services. The Company concluded that the undelivered element of research and development services had fair value. The Company concluded that the license did not have value on a standalone basis (e.g. absent the provision of the research and development services) and therefore did not represent a separate unit of accounting. The Company concluded that because the drug candidate had not yet been developed, the license was of no value to Boehringer without the ensuing research and development activities using the DART technology, which is proprietary to the Company. Likewise, Boehringer could not sell the license to another party (without the Company agreeing to provide the research and development activities for the other party). Therefore, the upfront license fee and research and development services were treated as a combined unit of accounting and recognized over the expected obligation period associated with the research and development services through October 2015, which represented the estimated period of development. The Company and Boehringer also agreed to establish a joint research committee to facilitate the governance and oversight of the parties' activities under the agreements. Management considered whether participation on the joint committee may be a deliverable and determined that it was not a deliverable. However, had management considered participation on the joint committee as a deliverable, it would not have had a material impact on the accounting for the arrangement as the period of participation in this committee matched the obligation period for the research and development services. The Company recognized no revenue under this agreement during the years ended December 31, 2017 and December 31, 2016. The Company recognized revenue of approximately $12.5 million during the year ended December 31, 2015 under this agreement, including a payment of $5.0 million for the achievement of preclinical milestones. No revenue was deferred under this agreement at December 31, 2017 or 2016. Green Cross In June 2010, the Company entered into a collaboration agreement with Green Cross Corp. (Green Cross) for the development of the Company's anti-HER2 antibody margetuximab. This arrangement grants Green Cross an exclusive license to conduct specified Phase 1 and Phase 2 clinical trials and commercialize margetuximab in South Korea. In March 2014, the Company and Green Cross entered into an amendment to the original agreement, causing the terms of the original agreement to be materially modified. Upon execution of the amendment, the Company became eligible to receive reimbursement for costs incurred for Phase 2 and Phase 3 clinical trials up to $5.5 million as well as clinical development and commercial milestone payments of up to $2.5 million. The Company determined that each potential clinical development and commercial milestone is substantive. The Company is also entitled to receive royalties on net sales of margetuximab in South Korea. The Company and Green Cross have formed a joint steering committee to coordinate and oversee activities on which the companies collaborate under the agreement. The Company evaluated the collaboration agreement with Green Cross and determined that it is a revenue arrangement with multiple deliverables or performance obligations. As a result of the material modification to the arrangement in March 2014, the Company reassessed the entire arrangement in accordance with the guidance provided by ASC 605-25, Multiple Element Arrangements (Revenue Recognition) as the original agreement was accounted for prior to adopting ASU 2009-13. The Company's substantive performance obligations under this agreement include an exclusive license to its technologies, research and development services, and participation in a joint steering committee. The Company concluded that the license and the reimbursements for research and development services do not have value on a standalone basis and therefore do not represent separate units of accounting. The initial $1.0 million upfront payment received by the Company upon execution of the original agreement is non-refundable; as such, there is no right of return for the license. Therefore, the upfront license fee and participation on the joint steering committee were treated as a combined unit of accounting and will be recognized over the term of the agreement through June 2020. Further, due to the fact the research and development services are not deemed to have stand-alone value, revenue for those services will be recognized over the entire term of the agreement (through June 2020). As a result of reassessing the arrangement in accordance with ASC 605-25, the Company was required to record an adjustment on the date of the material modification to reflect the revenue that would have resulted had the entity applied the requirements of ASC 605-25 from the inception of the agreement. As a result, the Company recorded an additional $1.3 million of revenue during 2014. The Company has received a total of $5.5 million through December 31, 2017 for reimbursement of research and development services, which is also being recognized over the remaining term of the agreement. The Company recognized revenues of approximately $0.9 million, $0.8 million and $0.5 million under this agreement during the years ended December 31, 2017, 2016 and 2015, respectively. No milestones were achieved under this agreement during the years ended December 31, 2017, 2016 and 2015. At December 31, 2017, $2.3 million of revenue was deferred under this agreement, $0.9 million of which was current and $1.4 million of which was non-current. At December 31, 2016, $3.2 million of revenue was deferred under this agreement, $0.9 million of which was current and $2.3 million of which was non-current. NIAID Contract The Company entered into a contract with the National Institute of Allergy and Infectious Diseases (NIAID), effective as of September 15, 2015, to perform product development and to advance up to two DART molecules, including MGD014. Under this contract, the Company will develop these product candidates for Phase 1/2 clinical trials as therapeutic agents, in combination with latency reversing treatments, to deplete cells infected with human immunodeficiency virus (HIV) infection. This contract includes a base period of $7.5 million to support development of MGD014 through IND application submission with the FDA, as well as up to $17.0 million in additional development funding via NIAID options. Should NIAID fully exercise such options, the Company could receive total payments of up to $24.5 million. The total potential period of performance under the award is from September 15, 2015 through September 14, 2022. During the year ended December 31, 2017, NIAID exercised the first option in the amount of $10.8 million. The Company recognized revenue of $1.7 million, $5.1 million and $0.2 million in revenue under this contract during the years ended December 31, 2017, 2016 and 2015, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

The Company leases manufacturing, office and laboratory space in Rockville, Maryland under five leases that have terms that expire between 2019 and 2027 unless renewed. During the year ended December 31, 2017, the Company entered into an agreement to sublease a portion of the space it leases. Under the terms of the sublease, the Company will receive a total of $2.4 million over the 30 month term.

The Rockville leases include a lease executed in July 2015 for space that the Company uses as its headquarters with office and laboratory space and manufacturing space currently under construction. Under the terms of the lease, which commenced on January 1, 2016, the Company received an assignment fee from the former tenant and a tenant improvement allowance from the landlord totaling $5.1 million. In July 2017, the Company executed a lease amendment for its headquarters building which extends the term of the lease to August 2027, restructures the rent due under the lease, and provides for an additional tenant improvement allowance from the landlord of $7.5 million, which was received during the third quarter. The assignment fee and tenant improvement allowances have been recorded as deferred rent and are being recognized over the new lease term.

The Company also leases office and laboratory space in South San Francisco under a lease that expires on February 28, 2018. During the year ended December 31, 2016, the Company entered into a sublease agreement for a portion of the South San Francisco space (see Note 8). As of December 31, 2017, future payments to be received by the Company under this sublease total approximately $0.1 million. In April 2017, the Company entered into a 72-month lease commencing in December 2017 for office and laboratory space which will replace our current South San Francisco location.

All of the leases contain rent escalation clauses and certain leases contain rent abatements. For financial reporting purposes, rent expense is charged to operations on a straight-line basis over the term of the lease. As of December 31, 2017 and 2016, the Company had recorded a deferred rent liability of $12.3 million and $6.2 million, respectively. Rent expense for the years ended December 31, 2017, 2016 and 2015 was $3.1 million, $3.0 million and $0.9 million, respectively.

Future minimum lease payments under noncancelable operating leases as of December 31, 2017 are as follows (in thousands):



2018	$	6,574
2019	6,342
2020	4,775
2021	4,743
2022	4,885
Thereafter	18,484
	$	45,803

Contingencies

From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business. The Company does not believe it is currently subject to any material matters where there is at least a reasonable possibility that a material loss may be incurred.

Quarterly Financial Information (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information (Unaudited)

Quarterly Financial Information (unaudited)



	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
	(in thousands, except per share data)
2017
Revenue	$	2,055		$	1,666		$	1,663		$	152,359
Net income (loss)	(37,655		)	(40,654		)	(47,043		)	105,727
Net income (loss) per share, basic	$	(1.08	)	$	(1.14	)	$	(1.28	)	$	2.87
Net income (loss) per share, diluted	$	(1.08	)	$	(1.14	)	$	(1.28	)	$	2.80

2016
Revenue	$	2,846		$	80,673		$	3,255		$	5,106
Net income (loss)	(30,363		)	40,464			(33,846		)	(34,783		)
Net income (loss) per share, basic	$	(0.88	)	$	1.17		$	(0.97	)	$	(1.00	)
Net income (loss) per share, diluted	$	(0.88	)	$	1.12		$	(0.97	)	$	(1.00	)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Use of Estimates

Cash, Cash Equivalents and Marketable Securities

Accounts Receivable

Fair Value of Financial Instruments


•	Level 1 – Fair value is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities.

•


•	Level 3 – Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by a reporting entity – e.g., determining an appropriate adjustment to a discount factor for illiquidity associated with a given security.

Concentration of Credit Risk

Property, Equipment and Software

Impairment of Long-Lived Assets

Income Taxes

Revenues

Revenue Recognition

There are no performance, cancellation, termination or refund provisions in any of the arrangements that contain material financial consequences to the Company.

Exclusive Licenses

Right-to-Develop Agreements

Research and Development Costs

Comprehensive Loss

Comprehensive loss represents net loss adjusted for the change during the periods attributed to unrealized gains and losses on available-for-sale securities.

Stock-based Compensation

Net Loss Per Share

Recently Issued Accounting Standards

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Fair Value Measurement Financial Assets

Financial assets measured at fair value on a recurring basis were as follows (in thousands):



	Fair Value Measurement at December 31, 2017
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	61,512	$	61,512	$	—	$	—
U.S Treasury securities	3,990		—		3,990		—
Government-sponsored enterprises	11,990		—		11,990		—
Corporate debt securities	78,418		—		78,418		—
Total assets measured at fair value ^(a)	$	155,910	$	61,512	$	94,398	$	—

(a) Total assets measured at fair value at December 31, 2017 includes approximately $62.5 million reported in cash and cash equivalents on the balance sheet.



	Fair Value Measurement at December 31, 2016
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	46,781	$	46,781	$	—	$	—
U.S Treasury securities	8,826		—		8,826		—
Government-sponsored enterprises	29,759		—		29,759		—
Corporate debt securities	166,300		—		166,300		—
Total assets measured at fair value ^(a)	$	251,666	$	46,781	$	204,885	$	—

(a) Total assets measured at fair value at December 31, 2016 includes approximately $50.8 million reported in cash and cash equivalents on the balance sheet.

Summary of Percentage of Customer Concentration

The following table includes those collaborators that represent more than 10% of total revenue earned in the periods indicated:



	Year Ended December 31,
	2017	2016	2015
Incyte Corporation (Incyte)	96%	*	*
Janssen Biotech, Inc. (Janssen)	*	85%	72%
Boehringer Ingelheim GmbH (Boehringer)	*	*	12%

The following table includes those counterparties that represent more than 10% of accounts receivable at the date indicated:



	December 31,
	2017	2016
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche)	73%	*
Les Laboratoires Servier and Institut de Recherches Servier (Servier)	12%	31%
Janssen	*	40%
U.S. Government	*	19%

* Balance is less than 10%

Estimated Useful Lives

Depreciation and amortization are computed using the straight-line method over the following estimated useful lives:



Computer equipment	3 years
Software	3 years
Furniture	10 years
Laboratory and office equipment	5 years
Leasehold improvements	Shorter of lease term or useful life

Computation of Basic and Diluted Loss Per Common Share

Basic and diluted loss per common share is computed as follows (in thousands except share and per share data):



	Year Ended December 31,
	2017			2016			2015
Numerator:
Net loss used for calculation of basic and diluted EPS	$	(19,626	)	$	(58,528	)	$	(20,140	)

Denominator:
Weighted average shares outstanding, basic	36,095,080			34,685,274			31,801,645
Effect of dilutive securities:
Stock options and restricted stock units	—			—			—

Weighted average shares outstanding, diluted	36,095,080			34,685,274			31,801,645
Net loss per share, basic and diluted	$	(0.54	)	$	(1.69	)	$	(0.63	)

Schedule of Antidilutive Securities Excluded from the Calculation of Diluted Loss Per Share

The following common stock equivalents were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive:



	Year Ended December 31,
	2017	2016	2015
Stock options	4,504,642	3,838,060	4,146,064

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Available-For-Sale Securities

Available-for-sale marketable securities as of December 31, 2017 and 2016 were as follows (in thousands):



	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	3,995	$	—	$	(6	)	$	3,989
Government-sponsored enterprises	11,998		—		(7		)	11,991
Corporate debt securities	77,462		2		(50		)	77,414
Total	$	93,455	$	2	$	(63	)	$	93,394



	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	4,826	$	—	$	(1	)	$	4,825
Government-sponsored enterprises	29,764		5		(10		)	29,759
Corporate debt securities	166,376		51		(127		)	166,300
Total	$	200,966	$	56	$	(138	)	$	200,884



	Amortized Cost		Fair Value
Mature in one year or less	$	192,985	$	192,898
Mature between one and five years	7,981		7,986
Total	$	200,966	$	200,884

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Property, Equipment and Software (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property, equipment and software consists of the following (in thousands):



	December 31,
	2017			2016
Computer equipment	$	2,261		$	2,520
Software	5,111			2,352
Furniture and office equipment	656			897
Lab equipment	20,549			20,208
Leasehold improvements	17,525			17,807
Construction in progress	32,800			—
Property, equipment and software	78,902			43,784
Less accumulated depreciation and amortization	(28,919		)	(25,823		)
Property, equipment and software, net	$	49,983		$	17,961

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock-Based Compensation Expense

The following stock-based compensation amounts were recognized for the periods indicated (in thousands):



	Year Ended December 31,
	2017		2016		2015

Research and development	$	7,388	$	5,778	$	3,623
General and administrative	7,356		6,387		4,224
Total stock-based compensation expense	$	14,744	$	12,165	$	7,847

Schedule of Employee Stock Options Award Valuation Assumptions

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model using the assumptions in the following table:



	Year Ended December 31,
	2017	2016	2015
Expected dividend yield	0%	0%	0%
Expected volatility	67% - 68%	64% - 69%	73% - 75%
Risk-free interest rate	1.9% - 2.3%	1.2% - 2.4%	1.6% - 2.1%
Expected term	6.25 years	6.25 years	6.25 years

Schedule of Stock Option and Restricted Stock Unit Activity

The following table summarizes stock option and restricted stock unit (RSU) activity for 2017:



	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	3,838,060		$	18.93	7.0
Granted	1,246,225		20.05
Options exercised or RSUs vested	(253,036	)	2.16
Forfeited or expired	(326,607	)	24.26
Outstanding, December 31, 2017	4,504,642		19.79		7.0	$	18,343

December 31, 2017:
Exercisable	2,910,171		17.65		6.1	17,495
Vested and expected to vest	4,337,015		19.60		6.9	18,275

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Components of the Company's Deferred Income Tax Assets (Liabilities)

The significant components of the Company's deferred income tax assets (liabilities) were as follows (in thousands):



	December 31,
	2017			2016
Deferred income tax assets:
Federal U.S. net operating loss carryforward	$	50,346		$	75,377
State net operating loss carryforward	7,551			6,583
Research and development credit, net	21,284			12,829
Orphan drug credit, net	21,708			19,855
Deferred rent	3,385			2,497
Deferred revenue	2,982			5,098
Depreciation	155			2,926
Other	5,847			5,085
Gross deferred income tax assets	113,258			130,250
Valuation allowance	(112,453		)	(128,844		)
Net deferred income tax assets	805			1,406

Deferred income tax liabilities:
Prepaid expenditures	(805		)	(1,406		)
Gross deferred income tax liabilities	(805		)	(1,406		)
Net deferred income tax asset/(liability)	$	—		$	—

Reconciliation of Reported Estimated Income Tax Benefit

The reconciliation of the reported estimated income tax benefit to the amount that would result by applying the U.S. federal statutory tax rate to the net income is as follows (in thousands):



	Year Ended December 31,
	2017			2016			2015

United States federal tax at statutory rate	$	(6,869	)	$	(20,489	)	$	(7,049	)
State taxes (net of federal benefit)	(735		)	(3,116		)	(897		)
Deferred income tax adjustments	607			173			661
Deferred state blended rate adjustments	(485		)	(32		)	(493		)
Deferred federal rate change reduction in corporate rate	39,447			—			—
Research credit, net	(8,455		)	(2,551		)	(3,296		)
Orphan drug credit, net	(1,853		)	(571		)	(106		)
Other permanent items	276			145			(25		)
Equity-based compensation	2,067			1,997			1,102
Change in valuation allowance	(24,000		)	24,444			10,103
Income tax expense/(benefit)	$	—		$	—		$	—

Reconciliation of the Beginning and Ending Amount of Gross Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in thousands):



	Year Ended December 31,
	2017		2016			2015
Beginning balance	$	2,465	$	2,425		$	2,047
Increases for current year tax positions	569		308			357
Increases/(decreases) for prior year tax positions	361		(268		)	21
Ending balance	$	3,395	$	2,465		$	2,425

Lease Exit Liability (Tables)

12 Months Ended

Dec. 31, 2017

Restructuring and Related Activities [Abstract]

Changes in Lease Exit Liability

Changes in the lease exit liability are as follows (in thousands):



Accrual balance at December 31, 2015	$	4,713
Principal payments and other adjustments	(2,822		)
Accrual balance at December 31, 2016	1,891
Principal payments and other adjustments (net of sublease receipts)	(1,593		)
Accrual balance at December 31, 2017	$	298

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of Minimum Future Lease Payments

Future minimum lease payments under noncancelable operating leases as of December 31, 2017 are as follows (in thousands):



2018	$	6,574
2019	6,342
2020	4,775
2021	4,743
2022	4,885
Thereafter	18,484
	$	45,803

Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Company's Consolidated Quarterly Results of Operations



	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
	(in thousands, except per share data)
2017
Revenue	$	2,055		$	1,666		$	1,663		$	152,359
Net income (loss)	(37,655		)	(40,654		)	(47,043		)	105,727
Net income (loss) per share, basic	$	(1.08	)	$	(1.14	)	$	(1.28	)	$	2.87
Net income (loss) per share, diluted	$	(1.08	)	$	(1.14	)	$	(1.28	)	$	2.80

2016
Revenue	$	2,846		$	80,673		$	3,255		$	5,106
Net income (loss)	(30,363		)	40,464			(33,846		)	(34,783		)
Net income (loss) per share, basic	$	(0.88	)	$	1.17		$	(0.97	)	$	(1.00	)
Net income (loss) per share, diluted	$	(0.88	)	$	1.12		$	(0.97	)	$	(1.00	)

Summary of Significant Accounting Policies (Details)	12 Months Ended
Summary of Significant Accounting Policies (Details)	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Number of operating segments \| Segment	1
Available-for-sale securities, other than temporary impairment losses	$ 0	$ 0
Allowance recorded	0	0
Impaired assets	0	0
Assets held-for-sale	$ 0	$ 0

Summary of Significant Accounting Policies - Summary of Fair Value Measurement Financial Asset and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and cash equivalents	$ 62,500	$ 50,800
Total assets measured at fair value	155,910	251,666
Money market funds
Assets [Abstract]
Cash and cash equivalents	61,512	46,781
U.S Treasury securities
Assets [Abstract]
Marketable securities	3,990	8,826
Government-sponsored enterprises
Assets [Abstract]
Marketable securities	11,990	29,759
Corporate debt securities
Assets [Abstract]
Marketable securities	78,418	166,300
Quoted Prices in Active Markets for Identical Assets, Level 1
Assets [Abstract]
Total assets measured at fair value	61,512	46,781
Quoted Prices in Active Markets for Identical Assets, Level 1 \| Money market funds
Assets [Abstract]
Cash and cash equivalents	61,512	46,781
Quoted Prices in Active Markets for Identical Assets, Level 1 \| U.S Treasury securities
Assets [Abstract]
Marketable securities	0	0
Quoted Prices in Active Markets for Identical Assets, Level 1 \| Government-sponsored enterprises
Assets [Abstract]
Marketable securities	0	0
Quoted Prices in Active Markets for Identical Assets, Level 1 \| Corporate debt securities
Assets [Abstract]
Marketable securities	0	0
Significant Other Observable Inputs, Level 2
Assets [Abstract]
Total assets measured at fair value	94,398	204,885
Significant Other Observable Inputs, Level 2 \| Money market funds
Assets [Abstract]
Cash and cash equivalents	0	0
Significant Other Observable Inputs, Level 2 \| U.S Treasury securities
Assets [Abstract]
Marketable securities	3,990	8,826
Significant Other Observable Inputs, Level 2 \| Government-sponsored enterprises
Assets [Abstract]
Marketable securities	11,990	29,759
Significant Other Observable Inputs, Level 2 \| Corporate debt securities
Assets [Abstract]
Marketable securities	78,418	166,300
Significant Unobservable Inputs, Level 3
Assets [Abstract]
Total assets measured at fair value	0	0
Significant Unobservable Inputs, Level 3 \| Money market funds
Assets [Abstract]
Cash and cash equivalents	0	0
Significant Unobservable Inputs, Level 3 \| U.S Treasury securities
Assets [Abstract]
Marketable securities	0	0
Significant Unobservable Inputs, Level 3 \| Government-sponsored enterprises
Assets [Abstract]
Marketable securities	0	0
Significant Unobservable Inputs, Level 3 \| Corporate debt securities
Assets [Abstract]
Marketable securities	$ 0	$ 0

Summary of Significant Accounting Policies - Summary of Collaborators that Represent More Than 10% of Total Revenue Earned (Details) - Sales revenue, net - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Incyte Corporation (Incyte)
Concentration Risk [Line Items]
Percentage of all significant revenue earned	96.00%
Janssen Biotech, Inc. (Janssen)
Concentration Risk [Line Items]
Percentage of all significant revenue earned		85.00%	72.00%
Boehringer Ingelheim GmbH (Boehringer)
Concentration Risk [Line Items]
Percentage of all significant revenue earned			12.00%

Summary of Significant Accounting Policies - Summary of Collaborators that Represent More Than 10% of Accounts Receivable (Details) - Customer Concentration Risk - Accounts receivable	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche)
Concentration Risk [Line Items]
Percentage of significant accounts receivable	73.00%
Les Laboratoires Servier and Institut de Recherches Servier (Servier)
Concentration Risk [Line Items]
Percentage of significant accounts receivable	12.00%	31.00%
Janssen Biotech, Inc. (Janssen)
Concentration Risk [Line Items]
Percentage of significant accounts receivable		40.00%
U.S. Government
Concentration Risk [Line Items]
Percentage of significant accounts receivable		19.00%

Summary of Significant Accounting Policies - Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2017
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Software
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Furniture
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Laboratory and office equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Leasehold improvements	Shorter of lease term or useful life

Summary of Significant Accounting Policies - Computation of Basic and Diluted Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss used for calculation of basic and diluted EPS	$ 105,727	$ (47,043)	$ (40,654)	$ (37,655)	$ (34,783)	$ (33,846)	$ 40,464	$ (30,363)	$ (19,626)	$ (58,528)	$ (20,140)
Denominator:
Weighted average shares outstanding, basic									36,095,080	34,685,274	31,801,645
Effect of dilutive securities:
Stock options and restricted stock units									0	0	0
Weighted average shares outstanding, diluted									36,095,080	34,685,274	31,801,645
Net loss per share, basic and diluted									$ (0.54)	$ (1.69)	$ (0.63)

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from the Calculation of Diluted Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive stock options	4,504,642	3,838,060	4,146,064

Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 93,455	$ 200,966
Gross Unrealized Gains	2	56
Gross Unrealized Losses	(63)	(138)
Fair Value	93,394	200,884
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,995	4,826
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(1)
Fair Value	3,989	4,825
Government-sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,998	29,764
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(7)	(10)
Fair Value	11,991	29,759
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	77,462	166,376
Gross Unrealized Gains	2	51
Gross Unrealized Losses	(50)	(127)
Fair Value	$ 77,414	$ 166,300

Marketable Securities - Available-For-Sale Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities, other than temporary impairment losses	$ 0	$ 0
Amortized Cost
Mature in one year or less		192,985,000
Mature between one and five years		7,981,000
Amortized Cost	93,455,000	200,966,000
Fair Value
Mature in one year or less		192,898,000
Mature between one and five years		7,986,000
Fair Value	93,394,000	200,884,000
Interest Income, Other	$ 2,400,000	$ 2,300,000	$ 200,000

Property, Equipment and Software (Details) - USD ($)	12 Months Ended
Property, Equipment and Software (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, equipment and software	$ 78,902,000	$ 43,784,000
Construction in progress	32,800,000	0
Less accumulated depreciation and amortization	(28,919,000)	(25,823,000)
Property, equipment and software, net	49,983,000	17,961,000
Property and equipment purchased but not yet paid	9,615,000	300,000
Depreciation expense	7,000,000	6,800,000	$ 3,200,000
Computer equipment
Property, Plant and Equipment [Line Items]
Property, equipment and software	2,261,000	2,520,000
Software
Property, Plant and Equipment [Line Items]
Property, equipment and software	5,111,000	2,352,000
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property, equipment and software	656,000	897,000
Lab equipment
Property, Plant and Equipment [Line Items]
Property, equipment and software	20,549,000	20,208,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and software	$ 17,525,000	$ 17,807,000

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			12 Months Ended
	May 03, 2017	Apr. 26, 2017	Jul. 31, 2015	Jan. 31, 2015	Feb. 28, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized (in shares)						125,000,000	125,000,000
Common stock, par value (in dollars per share)						$ 0.01	$ 0.01
Number of shares issued or sold (in shares)			3,525,000		1,800,000
Price per share (in dollars per share)			$ 37.00		$ 36.50
Additional shares sold under over-allotments option to underwriter (in shares)			528,750		450,000
Proceeds from sale of shares			$ 141,000		$ 76,700
Proceeds from issuance of common stock, net of offering costs						$ 34,244	$ 0	$ 203,467
Johnson & Johnson Innovation JJDC, Inc,
Class of Stock [Line Items]
Sale of common stock (in shares)				1,923,077
Sale of common stock (in dollars per share)				$ 39
Proceeds of stock sale				$ 75,000
Undesignated Preferred Stock
Class of Stock [Line Items]
Undesignated preferred stock, shares authorized (in shares)						5,000,000
Undesignated preferred stock, par value (in dollars per share)						$ 0.01
Undesignated preferred stock, shares issued (in shares)						0	0
Undesignated preferred stock, shares outstanding (in shares)						0	0
Registered Direct Offering
Class of Stock [Line Items]
Number of shares issued or sold (in shares)		1,100,000
Common stock purchase price (in dollars per share)		$ 21.50
Proceeds from issuance of common stock, net of offering costs		$ 23,700
At The Market Offering
Class of Stock [Line Items]
Number of shares issued or sold (in shares)						599,284
Proceeds of stock sale						$ 10,800
Common stock maximum amount available for issuance	$ 75,000

Stock- based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of common stock, net of offering costs		$ 34,244	$ 0	$ 203,467
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares authorized (in shares)					800,000
Common stock discount percent	10.00%
Percent of fair market value to purchase shares	85.00%
Common stock purchased by employees (in shares)		38,012
Proceeds from issuance of common stock, net of offering costs		$ 600

Stock- based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended			84 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Oct. 31, 2013	Feb. 28, 2003
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares)	4,504,642	3,838,060
Weighted average exercise price (in dollars per share)	$ 19.79	$ 18.93
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 14,744	$ 12,165	$ 7,847
Equity Incentive Plan 2003
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares authorized (in shares)						2,051,644
Increased number of shares authorized (in shares)				4,336,730
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares)	955,296
Weighted average exercise price (in dollars per share)	$ 1.85
Stock Incentive Plan 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares authorized (in shares)					1,960,168
Increased number of shares authorized (in shares)	6,769,888
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares)	3,549,346
Weighted average exercise price (in dollars per share)	$ 24.62
Stock reserved for future issuance (in shares)	1,960,168
Percentage of common stock share outstanding	4.00%
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 7,388	5,778	3,623
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 7,356	$ 6,387	$ 4,224

Stock- based Compensation - Option Pricing Assumptions (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected term	6 years 3 months	6 years 3 months	6 years 3 months
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	67.00%	64.00%	73.00%
Risk-free interest rate	1.90%	1.20%	1.60%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	68.00%	69.00%	75.00%
Risk-free interest rate	2.30%	2.40%	2.10%
Options granted, maximum term	10 years

Stock- based Compensation - Stock Option and Restricted Stock Unit Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
December 31, 2016	3,838,060
Granted	1,246,225
Options exercised or RSUs vested	(253,036)	(526,715)	(374,214)
Forfeited or expired	(326,607)
December 31, 2017	4,504,642	3,838,060
Exercisable	2,910,171
Vested and expected to vest	4,337,015
Weighted-Average Exercise Price
December 31, 2016	$ 18.93
Granted	20.05
Options exercised or RSUs vested	2.16
Forfeited or expired	24.26
December 31, 2017	19.79	$ 18.93
Exercisable	17.65
Vested and expected to vest	$ 19.60
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual term, Outstanding	7 years	7 years
Weighted-average remaining contractual term, Exercisable	6 years 1 month 6 days
Weighted-average remaining contractual term, Vested and expected to vest	6 years 10 months 24 days
Aggregate intrinsic value, Outstanding	$ 18,343
Aggregate intrinsic value, Exercisable	17,495
Aggregate intrinsic value, Vested and expected to vest	$ 18,275
Common stock, shares issued (in shares)	253,036	526,715	374,214
Cash proceeds from exercise of stock options	$ 500	$ 1,900	$ 900
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 12.53	$ 15.17	$ 20.90
Share-based compensation arrangement by share-based payment award, options, exercises in period, intrinsic value	$ 4,200	$ 10,800	$ 10,900
Fair value of shares vested	14,600	$ 11,600	$ 7,300
Unrecognized compensation cost related to non-vested stock-based compensation arrangements	$ 20,300
Unrecognized compensation expense recognition period	2 years 3 months 18 days

Income Taxes - Components of the Company's Deferred Tax Assets (Liabilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision for federal or state income taxes	$ 0	$ 0	$ 0
Deferred income tax assets:
Federal U.S. net operating loss carryforward	50,346,000	75,377,000
State net operating loss carryforward	7,551,000	6,583,000
Research and development credit, net	21,284,000	12,829,000
Orphan drug credit, net	21,708,000	19,855,000
Deferred rent	3,385,000	2,497,000
Deferred revenue	2,982,000	5,098,000
Depreciation	155,000	2,926,000
Other	5,847,000	5,085,000
Gross deferred income tax assets	113,258,000	130,250,000
Valuation allowance	(112,453,000)	(128,844,000)
Net deferred income tax assets	805,000	1,406,000
Deferred income tax liabilities:
Prepaid expenditures	(805,000)	(1,406,000)
Gross deferred income tax liabilities	(805,000)	(1,406,000)
Net deferred income tax asset/(liability)	0	$ 0
Operating Loss Carryforwards [Line Items]
Remaining portion of net operating losses	226,200,000
Previously unrecognized excess tax benefits	18,600,000
Previously unrecognized excess tax benefits, tax effected portion	6,500,000
U.S. Federal and State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	239,700,000
U.S. Federal Government
Operating Loss Carryforwards [Line Items]
US Federal tax credits carry forward	42,800,000
Net operating loss for limited use	13,500,000
U.S. Federal Government \| Minimum
Operating Loss Carryforwards [Line Items]
Net operating losses limited for use utilized on an annual basis	200,000
U.S. Federal Government \| Maximum
Operating Loss Carryforwards [Line Items]
Net operating losses limited for use utilized on an annual basis	$ 1,400,000

Income Taxes - Reconciliation of Reported Estimated Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States federal tax at statutory rate	$ (6,869)	$ (20,489)	$ (7,049)
State taxes (net of federal benefit)	(735)	(3,116)	(897)
Deferred income tax adjustments	607	173	661
Deferred state blended rate adjustments	(485)	(32)	(493)
Deferred federal rate change reduction in corporate rate	39,447	0	0
Research credit, net	(8,455)	(2,551)	(3,296)
Orphan drug credit, net	(1,853)	(571)	(106)
Other permanent items	276	145	(25)
Equity-based compensation	2,067	1,997	1,102
Change in valuation allowance	(24,000)	24,444	10,103
Income tax expense/(benefit)	$ 0	$ 0	$ 0

Income Taxes - Reconciliation of the Beginning and Ending Amount of Gross Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 2,465,000	$ 2,425,000	$ 2,047,000
Increases/(decreases) for current year tax positions	569,000	308,000	357,000
Increases for prior year tax positions	361,000		21,000
Decreases for prior year tax positions		(268,000)
Ending balance	3,395,000	2,465,000	2,425,000
Gross unrecognized tax benefits	3,400,000	2,400,000
Unrecognized interest or penalties	$ 0	$ 0	$ 0

Lease Exit Liability Lease Exit Liability - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015	Jul. 06, 2017	May 31, 2016
Restructuring Cost and Reserve [Line Items]
Future sublease payments to be received	$ 0.1		$ 2.4
Reduction in research and development expense	$ 1.3
Reduction of research and development expense		$ 1.9
Raven Biotechnologies Inc.
Restructuring Cost and Reserve [Line Items]
Future sublease payments to be received				$ 1.3

Lease Exit Liability - Changes in Lease Exit Liability (Details) - Contract termination - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Accrual beginning balance	$ 1,891	$ 4,713
Principal payments and other adjustments (net of sublease receipts)	(1,593)	(2,822)
Accrual ending balance	$ 298	$ 1,891

Collaboration and Other Agreements Collaboration and Other Agreements, Incyte Corporation (Details) - Incyte MGA012 Agreement - Incyte Corporation (Incyte) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2017
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment		$ 150.0	$ 150.0
Clinical trial activities selling price amount	$ 4.0
Recognized revenue under agreement			151.1
Clinical trial activities performed, revenue recognized			$ 1.1
Maximum
Collaboration and Other Agreements [Line Items]
Potential development and regulatory milestone payments	420.0
Potential commercial milestone payments	$ 330.0
Potential proceeds from royalties percent	24.00%
Minimum
Collaboration and Other Agreements [Line Items]
Potential proceeds from royalties percent	15.00%

Collaboration and Other Agreements, F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. (Details) - USD ($) $ in Thousands	1 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaboration and Other Agreements [Line Items]
Deferred revenue included in current liabilities		$ 7,202	$ 4,261
Deferred revenue included in long-term liabilities		13,637	$ 10,045
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche)
Collaboration and Other Agreements [Line Items]
Potential milestone payments and royalties on future sales		$ 370,000
Expected period of development		30 months
Deferred revenue		$ 10,000
Deferred revenue included in current liabilities		4,000
Deferred revenue included in long-term liabilities		$ 6,000
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche) \| Subsequent Event
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 10,000

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References + Details

- Definition

The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Collaboration and Other Agreements, Janssen Biotech, Inc. (Details) - Janssen Biotech Inc. - USD ($) $ / shares in Units, $ in Millions	1 Months Ended			12 Months Ended
	Jul. 31, 2016	Jan. 31, 2015	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015
Janssen MGD011 Agreement
Collaboration and Other Agreements [Line Items]
Sale of common stock (in shares)			1,923,077
Proceeds of stock sale		$ 75.0	$ 75.0
Non-refundable upfront payment						$ 50.0
Sale of common stock (in dollars per share)		$ 39.00
Premium received on stock purchase		$ 12.3
Total consideration		125.0
Amount allocated to equity		62.7
Amount allocated to license and R&D		$ 62.3
Clinical milestone earned during period							$ 10.0
Recognized revenue under agreement				$ 0.0	$ 2.0	$ 72.3
Janssen MGD015 Agreement
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 75.0				75.0
Recognized revenue under agreement				$ 0.6	$ 75.8

Collaboration and Other Agreements, Takeda (Details) - Takeda Pharmaceutical Company Limited (Takeda) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2014	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Takeda MGD010 Agreement
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 15,000,000
Amount allocated to agreement	$ 10,000,000
Expected period of development	24 months
Option exercise fee recognition period		8 months
Recognized revenue under agreement			$ 0	$ 2,100,000	$ 8,000,000
Milestone received					$ 3,000,000
Deferred revenue			$ 0	$ 0
Research Collaboration and License Option Agreement
Collaboration and Other Agreements [Line Items]
Amount allocated to agreement	$ 5,000,000

Collaboration and Other Agreements, Servier (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Collaboration and Other Agreements [Line Items]
Deferred revenue included in current liabilities		$ 7,202,000	$ 4,261,000
Deferred revenue included in long-term liabilities		13,637,000	10,045,000
Servier \| Servier DART
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 20,000,000
Original period of development	29 months
Expected period of development	75 months
Change in accounting estimate, current year impact		$ 800,000			$ 3,700,000
Option exercise fee					$ 15,000,000
Option exercise fee recognition period		124 months			82 months
Offset to research and development costs under collaboration arrangement		$ 3,200,000	2,600,000	$ 500,000
Recognized revenue under agreement		2,500,000	3,300,000	$ 3,500,000
Deferred revenue		8,500,000	11,100,000
Deferred revenue included in current liabilities		2,300,000	3,300,000
Deferred revenue included in long-term liabilities		$ 6,200,000	$ 7,800,000
Servier \| Maximum \| Servier DART
Collaboration and Other Agreements [Line Items]
Potential License Fee	$ 40,000,000
Potential clinical milestone payments under agreement	63,000,000
Potential regulatory milestone payments under agreement	188,000,000
Potential sales milestone payments under agreement	$ 420,000,000

Collaboration and Other Agreements, Boehringer (Details) - Boehringer Ingelheim GmbH (Boehringer)	1 Months Ended	12 Months Ended
	Oct. 31, 2010 USD ($) Payment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 15,000,000
Number of annual maintenance payments received \| Payment	3
Clinical milestone payments	$ 34,000,000
Additional potential regulatory milestone payments under agreement	88,500,000
Additional potential sales milestone payments under agreement	$ 82,500,000
Recognized revenue under agreement		$ 0	$ 0	$ 12,500,000
Milestone payment				$ 5,000,000
Deferred revenue		$ 0	$ 0

Collaboration and Other Agreements, Green Cross (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2010	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Collaboration and Other Agreements [Line Items]
Deferred revenue included in current liabilities		$ 7,202,000	$ 4,261,000
Deferred revenue included in long-term liabilities		13,637,000	10,045,000
Green Cross
Collaboration and Other Agreements [Line Items]
Non-refundable upfront payment	$ 1,000,000
Adjustment to revenue from contract material modification					$ 1,300,000
Proceeds from research and development services		5,500,000
Recognized revenue under agreement		900,000	800,000	$ 500,000
Milestone achieved		0	0	$ 0
Deferred revenue		2,300,000	3,200,000
Deferred revenue included in current liabilities		900,000	900,000
Deferred revenue included in long-term liabilities		$ 1,400,000	$ 2,300,000
Green Cross \| Maximum
Collaboration and Other Agreements [Line Items]
Aggregate potential future cost reimbursement	5,500,000.0
Clinical and commercial milestone payments	$ 2,500,000.0

Collaboration and Other Agreements, NIAID Contract (Details) - NIAID		12 Months Ended
	Sep. 15, 2015 USD ($) Molecule	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Collaboration and Other Agreements [Line Items]
Commercialization of molecules \| Molecule	2
Base period value	$ 7,500,000
Proceeds from additional development funding options under agreement		$ 10,800,000
Recognized revenue under agreement		$ 1,700,000	$ 5,100,000	$ 200,000
Maximum
Collaboration and Other Agreements [Line Items]
Additional development funding options	17,000,000.0
Total potential value	$ 24,500,000.0

Commitments and Contingencies (Details) $ in Thousands			1 Months Ended		12 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Jul. 21, 2017 USD ($)	Jul. 06, 2017 USD ($)	Apr. 30, 2017	Jul. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) Lease	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Number of leases \| Lease					5
Future sublease payments to be received		$ 2,400			$ 100
Lessee leasing arrangements, term of operating leases		30 months	72 months
Lease incentives	$ (7,500)			$ (5,100)
Deferred rent liability					12,300	$ 6,200
Rent expense					3,100	$ 3,000	$ 900
Future minimum rental payments required under all non-cancelable operating leases [Abstract]
2018					6,574
2019					6,342
2020					4,775
2021					4,743
2022					4,885
Thereafter					18,484
Total					$ 45,803

Employee Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefit Plan (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012
Retirement Benefits [Abstract]
Eligible age to participate in plan				21 years
Percentage of employee contribution to salary				100.00%
Percentage of employee vested contribution	100.00%
Defined contribution plan, employer discretionary contribution amount	$ 1.1	$ 1.0	$ 0.4

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 152,359	$ 1,663	$ 1,666	$ 2,055	$ 5,106	$ 3,255	$ 80,673	$ 2,846	$ 157,742	$ 91,880	$ 100,854
Net loss	$ 105,727	$ (47,043)	$ (40,654)	$ (37,655)	$ (34,783)	$ (33,846)	$ 40,464	$ (30,363)	$ (19,626)	$ (58,528)	$ (20,140)
Net income (loss) per share, basic (in dollars per share)	$ 2.87	$ (1.28)	$ (1.14)	$ (1.08)	$ (1.00)	$ (0.97)	$ 1.17	$ (0.88)
Net income (loss) per share, diluted (in dollars per share)	$ 2.80	$ (1.28)	$ (1.14)	$ (1.08)	$ (1.00)	$ (0.97)	$ 1.12	$ (0.88)

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit Plan In 2002, the Company established the MacroGenics 401(k) Plan (the Plan) for its employees under Section 401(k) of the IRC. Under this Plan, all employees at least 21 years of age are eligible to participate in the Plan, starting on the first day of each month. Employees may contribute up to 100% of their salary, subject to government maximums. Employees are 100% vested in their contributions to the Plan. The Company's contribution to the Plan, as determined by the Board of Directors, is discretionary. The Company's contributions to the Plan totaled $1.1 million, $1.0 million and $0.4 million for the years ended December 31, 2017, 2016 and 2015, respectively.