Celldex Therapeutics (CLDX) 10-K 14 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Mar. 06, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	Celldex Therapeutics, Inc.
Entity Central Index Key	744,218
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 435
Entity Common Stock, Shares Outstanding		123,213,438
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and Cash Equivalents	$ 42,461	$ 72,108
Marketable Securities	147,315	217,781
Accounts and Other Receivables	1,784	970
Prepaid and Other Current Assets	4,009	4,077
Total Current Assets	195,569	294,936
Property and Equipment, Net	13,192	11,461
Intangible Assets, Net	81,487	20,794
Other Assets	2,134	1,428
Goodwill	90,976	8,965
Total Assets	383,358	337,584
Current Liabilities:
Accounts Payable	1,740	1,506
Accrued Expenses	28,657	24,316
Current Portion of Long-Term Liabilities	4,826	4,418
Total Current Liabilities	35,223	30,240
Other Long-Term Liabilities	82,704	17,239
Total Liabilities	117,927	47,479
Commitments and Contingent Liabilities (Notes 13 and 15)
Stockholders' Equity:
Convertible Preferred Stock, $.01 Par Value; 3,000,000 Shares Authorized; No Shares Issued and Outstanding at December 31, 2016 and 2015
Common Stock, $.001 Par Value; 297,000,000 Shares Authorized; 120,516,654 and 98,685,595 Shares Issued and Outstanding at December 31, 2016 and 2015, respectively	121	99
Additional Paid-In Capital	982,255	878,655
Accumulated Other Comprehensive Income	2,541	2,307
Accumulated Deficit	(719,486)	(590,956)
Total Stockholders' Equity	265,431	290,105
Total Liabilities and Stockholders' Equity	$ 383,358	$ 337,584

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
BALANCE SHEETS
Convertible Preferred Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Convertible Preferred Stock, Shares Authorized	3,000,000	3,000,000
Convertible Preferred Stock, Shares Issued	0	0
Convertible Preferred Stock, Shares Outstanding	0	0
Common Stock, Par Value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, Shares Authorized	297,000,000	297,000,000
Common Stock, Shares Issued	120,516,654	98,685,595
Common Stock, Shares Outstanding	120,516,654	98,685,595

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUE:
Product Development and Licensing Agreements	$ 2,174	$ 1,442	$ 838
Contracts and Grants	4,612	4,038	2,748
Total Revenue	6,786	5,480	3,586
OPERATING EXPENSE:
Research and Development	102,726	100,171	104,381
General and Administrative	35,979	33,837	20,622
Amortization of Acquired Intangible Assets	997	1,013	1,013
Total Operating Expense	139,702	135,021	126,016
Operating Loss	(132,916)	(129,541)	(122,430)
Investment and Other Income, Net	4,386	2,344	4,350
Net Loss	$ (128,530)	$ (127,197)	$ (118,080)
Basic and Diluted Net Loss Per Common Share (in dollars per share)	$ (1.27)	$ (1.31)	$ (1.32)
Shares Used in Calculating Basic and Diluted Net Loss per Share (in shares)	101,529	97,051	89,399
COMPREHENSIVE LOSS:
Net Loss	$ (128,530)	$ (127,197)	$ (118,080)
Other Comprehensive Income (Loss):
Foreign Currency Translation Adjustments		15	(5)
Unrealized Gain (Loss) on Marketable Securities	234	(298)	(73)
Comprehensive Loss	$ (128,296)	$ (127,480)	$ (118,158)

STATEMENTS OF STOCKHOLDERS' EQU

STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Balance at Dec. 31, 2013	$ 89	$ 662,717	$ 2,668	$ (345,679)	$ 319,795
Balance (in shares) at Dec. 31, 2013	89,246,832
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	$ 1	1,170			1,171
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)	193,775
Shares Issued in Connection with Supply Agreement		2,000			2,000
Shares Issued in Connection with Supply Agreement (in shares)	152,172
Share-Based Compensation		6,852			6,852
Foreign Currency Translation Adjustments			(5)		(5)
Unrealized Gains (Losses) on Marketable Securities			(73)		(73)
Net Loss				(118,080)	(118,080)
Balance at Dec. 31, 2014	$ 90	672,739	2,590	(463,759)	211,660
Balance (in shares) at Dec. 31, 2014	89,592,779
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	$ 1	4,310			4,311
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)	755,316
Shares Issued in Underwritten Offering	$ 8	188,832			188,840
Shares Issued in Underwritten Offering (in shares)	8,337,500
Share-Based Compensation		12,774			12,774
Foreign Currency Translation Adjustments			15		15
Unrealized Gains (Losses) on Marketable Securities			(298)		(298)
Net Loss				(127,197)	(127,197)
Balance at Dec. 31, 2015	$ 99	878,655	2,307	(590,956)	$ 290,105
Balance (in shares) at Dec. 31, 2015	98,685,595				98,685,595
Increase (Decrease) in Stockholders' Equity
Shares Issued under Stock Option and Employee Stock Purchase Plans	$ 1	534			$ 535
Shares Issued under Stock Option and Employee Stock Purchase Plans (in shares)	158,152
Shares Issued in Connection with Cantor Agreement	$ 3	13,943			13,946
Shares Issued in Connection with Cantor Agreement (in shares)	3,303,800
Shares Issued in Connection with the Kolltan Acquisition	$ 18	73,379			73,397
Shares Issued in Connection with the Kolltan Acquisition (in shares)	18,257,996
Shares Issued in Connection with Kolltan Severance		427			427
Shares Issued in Connection with Kolltan Severance (in shares)	111,111
Share-Based Compensation		15,317			15,317
Unrealized Gains (Losses) on Marketable Securities			234		234
Net Loss				(128,530)	(128,530)
Balance at Dec. 31, 2016	$ 121	$ 982,255	$ 2,541	$ (719,486)	$ 265,431
Balance (in shares) at Dec. 31, 2016	120,516,654				120,516,654

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows From Operating Activities:
Net Loss	$ (128,530)	$ (127,197)	$ (118,080)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	3,095	2,998	2,388
Amortization of Intangible Assets	997	1,013	1,013
Amortization and Premium of Marketable Securities, Net	926	350	95
Realized Gain on Sales and Maturities of Marketable Securities			(11)
Loss on Sale or Disposal of Assets	81		6
Stock-Based Compensation Expense	15,317	12,774	6,852
Non-Cash Expense	1,638	288	72
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	(814)	(543)	62
Prepaid and Other Current Assets	1,320	(653)	(2,026)
Other Assets	(89)	6	65
Accounts Payable and Accrued Expenses	(4,970)	4,875	1,450
Other Liabilities	(2,007)	7,202	6,577
Net Cash Used in Operating Activities	(113,036)	(98,887)	(101,537)
Cash Flows From Investing Activities:
Sales and Maturities of Marketable Securities	242,792	161,090	109,232
Purchases of Marketable Securities	(173,925)	(206,405)	(148,314)
Investment in Other	(1,801)
Cash Acquired in Kolltan Acquisition, net	4,592
Acquisition of Property and Equipment	(2,751)	(4,876)	(1,929)
Net Cash Provided by (Used in) Investing Activities	68,907	(50,191)	(41,011)
Cash Flows From Financing Activities:
Net Proceeds from Stock Issuances	13,946	188,840
Proceeds from Issuance of Stock from Employee Benefit Plans	536	4,311	1,171
Net Cash Provided by Financing Activities	14,482	193,151	1,171
Effect of Exchange Rate Changes on Cash and Cash Equivalents		15	(5)
Net (Decrease) Increase in Cash and Cash Equivalents	(29,647)	44,088	(141,382)
Cash and Cash Equivalents at Beginning of Period	72,108	28,020	169,402
Cash and Cash Equivalents at End of Period	42,461	72,108	28,020
Non-cash Investing Activities
Accrued construction in progress	159	$ 75	$ 1,027
Non-cash Supplemental Disclosure
Shares issued to former Kolltan executive for settlement of severance	426
Shares issued in connection with Kolltan Acquisition	$ 73,397

NATURE OF BUSINESS AND OVERVIEW

NATURE OF BUSINESS AND OVERVIEW	12 Months Ended
	Dec. 31, 2016
NATURE OF BUSINESS AND OVERVIEW
NATURE OF BUSINESS AND OVERVIEW	(1) NATURE OF BUSINESS AND OVERVIEW Celldex Therapeutics, Inc. (the "Company" or "Celldex") is a biopharmaceutical company focused on the development and commercialization of several immunotherapy technologies for the treatment of cancer and other difficult-to-treat diseases. The Company currently has seven drug candidates in clinical development including glembatumumab vedotin (also referred to as CDX-011), varlilumab (also referred to as CDX-1127), CDX-0158, CDX-3379, CDX-1401, CDX-301 and CDX-014. As more fully discussed in Note 17, on November 29, 2016, the Company acquired (the "Kolltan Acquisition") Kolltan Pharmaceuticals, Inc. ("Kolltan"), a privately held clinical-stage biotechnology company based in New Haven, Connecticut in accordance with the Agreement and Plan of Merger dated as of November 1, 2016 (the "Merger Agreement"). Under the terms of the Merger Agreement, Kolltan's investors received, in exchange for their share and debt interests in Kolltan, an aggregate of 18,257,996 shares of Celldex's common stock. In addition, following closing, certain officers of Kolltan will receive an aggregate of 437,901 shares of Celldex's common stock in lieu of cash severance obligations, less tax withholdings. In December 2016, the Company issued 111,111 shares of Celldex's common stock as partial payment of this obligation. In addition, in the event that certain specified preclinical and clinical development milestones related to Kolltan's development programs and/or Celldex's development programs and certain commercial milestones related to Kolltan's drug candidates are achieved, Celldex will be required to pay Kolltan's stockholders milestone payments of up to $172.5 million, which milestone payments may be made, at Celldex's sole election, in cash, in shares of Celldex's common stock or a combination of both, subject to NASDAQ listing requirements and provisions of the Merger Agreement. The number of shares of Celldex common stock issuable in connection with a milestone payment, if any, will be determined based on the average closing price per share of Celldex common stock for the five trading day period ending three calendar days prior to the achievement of such milestone. Pursuant to applicable NASDAQ listing rules, Celldex is required to obtain stockholder approval of such issuances of Celldex's common stock to the extent that such issuances exceed 19.9% of its common stock outstanding prior to the merger. If Celldex does not obtain stockholder approval of such common stock issuances, Celldex may elect to pay the milestone consideration in cash to maintain compliance with applicable NASDAQ listing standards. Celldex may still decide to pay cash even if Celldex obtains stockholder approval although it is required to maintain a certain percentage of the overall consideration paid in Celldex common stock to satisfy certain tax requirements under the Merger Agreement. At December 31, 2016, the Company had cash, cash equivalents and marketable securities of $189.8 million. The Company has had recurring losses and incurred a loss of $128.5 million for the year ended December 31, 2016. Net cash used in operations for the year ended December 31, 2016 was $113.0 million. The Company believes that the cash, cash equivalents and marketable securities at March 14, 2017 will be sufficient to meet estimated working capital requirements and fund planned operations for at least the next twelve months from the date of issuance of these financial statements. During the next twelve months and beyond, the Company will take further steps to raise additional capital to meet its liquidity needs. These capital raising activities may include, but may not be limited to, one or more of the following: the licensing of drug candidates with existing or new collaborative partners, possible business combinations, issuance of debt, or the issuance of common stock or other securities via private placements or public offerings. While the Company may seek capital through a number of means, there can be no assurance that additional financing will be available on acceptable terms, if at all, and the Company's negotiating position in capital-raising efforts may worsen as existing resources are used. There is also no assurance that the Company will be able to enter into further collaborative relationships. Additional equity financings may be dilutive to the Company's stockholders; debt financing, if available, may involve significant cash payment obligations and covenants that restrict the Company's ability to operate as a business; and licensing or strategic collaborations may result in royalties or other terms which reduce the Company's economic potential from products under development. The Company's ability to continue funding its planned operations into and beyond twelve months from the issuance date is also dependent on the timing and manner of payment of future contingent milestones from the Kolltan acquisition, in the event that the Company achieves the drug candidate milestones related to those payments. The Company may decide to pay those milestone payments in cash. Further, if the Company does not obtain shareholder approval to issue shares in lieu of cash payments, the Company would need to make those payments in cash in order to meet its NASDAQ listing requirements. If the Company is unable to raise the funds necessary to meet its long-term liquidity needs, it may have to delay or discontinue the development of one or more programs, discontinue or delay on-going or anticipated clinical trials, license out programs earlier than expected, raise funds at a significant discount or on other unfavorable terms, if at all, or sell all or a part of the Company.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2016
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	(2) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation Following the Kolltan Acquisition, the consolidated financial statements reflect the financial position, results of operation and cash flows of the combined companies. Accordingly, this report reflects the financial condition as of December 31, 2016 and the results of operations and cash flows for the period from the Kolltan Acquisition on November 29, 2016 through December 31, 2016. On December 31, 2016, the Company completed the merger of Kolltan with and into Celldex pursuant to a short-form merger effected under Delaware law. As a result, the separate corporate existence of Kolltan has ceased and the Company has succeeded to all rights, privileges, powers and franchises of Kolltan. On December 31, 2014, the Company's wholly-owned subsidiary, Celldex Research Corporation, merged into Celldex Therapeutics, Inc. In February 2016, the Company formed a wholly-owned subsidiary, Celldex Therapeutics Europe GmbH, in Zug, Switzerland. In July 2016, we formed a wholly-owned subsidiary, Celldex Australia Pty Ltd, in Brisbane, Australia. The statements of operations and comprehensive loss, of stockholders' equity, and of cash flows, are consolidated for the years ended December 31, 2016 and 2014. These consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary prior to the merger. All intercompany balances and transactions have been eliminated in consolidation. The Company operates in one segment, which is the business of development, manufacturing and commercialization of novel therapeutics for human health care. Use of Estimates The preparation of the financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and use assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the dates of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity date of 90 days or less at the date of purchase to be cash equivalents. Cash equivalents consist principally of money market funds and debt securities. Marketable Securities The Company invests its excess cash balances in marketable securities including municipal bond securities, U.S. government agency securities, and high-grade corporate bonds. The Company classifies all of its marketable securities as current assets on the balance sheets because they are available-for-sale and available to fund current operations. Marketable securities are stated at fair value with their unrealized gains and losses included as a component of accumulated other comprehensive income (loss), which is a separate component of stockholders' equity, until such gains and losses are realized. If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is transferred from other comprehensive income (loss) to the statements of operations. Realized gains and losses are determined on the specific identification method and are included in investment and other income, net. Concentration of Credit Risk and of Significant Customers and Suppliers Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash, cash equivalents, marketable securities and accounts receivable. The Company invests its cash, cash equivalents and marketable securities in debt instruments and interest bearing accounts at major financial institutions in excess of insured limits. The Company mitigates credit risk by limiting the investment type and maturity to securities that preserve capital, maintain liquidity and have a high credit quality. The Company has not historically experienced credit losses from its accounts receivable and therefore has not established an allowance for doubtful accounts. Revenue from Rockefeller and BMS represented 40% and 31% for the year ended December 31, 2016, 62% and 24% for the year ended December 31, 2015, and 75% and 20% for the year ended December 31, 2014, of total Company revenue, respectively. The Company relies on contract manufacturing organizations (CMO) to manufacture drug substance and drug product for its late-stage clinical study of glembatumumab vedotin as well as for future commercial supplies. The Company also relies on CMOs for supply of raw materials as well as filling, packaging, storage and shipping of drug product. These clinical studies would be adversely affected by a significant interruption in the supply of glembatumumab vedotin. The Company also relies on third-party collaborators to develop companion diagnostic tests for certain of its drug candidates, including glembatumumab vedotin. Fair Value Measurements The Company has certain assets and liabilities that are measured at fair value in the financial statements. The Company seeks to maximize the use of observable inputs (market data obtained from sources independent from the Company) and to minimize the use of unobservable inputs (the Company's assumptions about how market participants would price assets and liabilities) when measuring the fair value of its assets and liabilities. These assets and liabilities are classified into one of three levels of the following fair value hierarchy as defined by U.S. GAAP: Level 1: Observable inputs such as quoted prices in active markets for identical assets or liabilities. An active market for an asset or liability is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2: Observable inputs other than Level 1 prices, such as quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active. Level 3: Unobservable inputs based on the Company's assessment of the assumptions that market participants would use in pricing the asset or liability. Property and Equipment Property and equipment is stated at cost and depreciated over the estimated useful lives of the related assets using the straight-line method. Laboratory equipment and office furniture and equipment are depreciated over five years and computer equipment is depreciated over three years. Manufacturing equipment is amortized over seven to ten years. Leasehold improvements are amortized over the shorter of the estimated useful life or the non-cancelable term of the related lease, including any renewals that are reasonably assured of occurring. Property and equipment under construction is classified as construction in progress and is depreciated or amortized only after the asset is placed in service. Expenditures for maintenance and repairs are charged to expense whereas the costs of significant improvements which extend the life of the underlying asset are capitalized. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are eliminated and any resulting gain or loss is reflected in the Company's statements of operations and comprehensive loss. The treatment of costs to construct property and equipment depends on the nature of the costs and the stage of construction. Costs incurred in the project planning, design, construction and installation phases are capitalized as part of the cost of the asset. The Company stops capitalizing these costs when the asset is substantially complete and ready for its intended use. For manufacturing property and equipment, the Company also capitalizes the cost of validating these assets for the underlying manufacturing process. The Company completes the capitalization of validation costs when the asset is substantially complete and ready for its intended use. Costs capitalized include incremental labor and fringe benefits, and direct consultancy services. Business Combinations The Company records the fair value of the consideration transferred to acquire a business to the tangible assets and identifiable intangible assets acquired and liabilities assumed on the basis of their fair values at the date of acquisition. The Company assesses the fair value of assets, including intangible assets such as in-process research and development (IPR&D), using a variety of methods including present value models. Each asset is measured at fair value from the perspective of a market participant. The method used to estimate the fair values of IPR&D assets incorporates significant assumptions regarding the estimates a market participant would make in order to evaluate an asset, including a market participant's assumptions regarding the probability of completing IPR&D projects, which would require obtaining regulatory approval for marketing of the associated drug candidate; a market participant's estimates regarding the timing of and the expected costs to complete IPR&D projects; a market participant's estimates of future cash flows from potential product sales; and the appropriate discount rates for a market participant. Transaction costs and restructuring costs associated with the transaction are expensed as incurred. The Company records contingent consideration resulting from a business combination at its fair value on the acquisition date. The Company determines the fair value of the contingent consideration based primarily on the (i) timing and probability of success of clinical events or regulatory approvals; (ii) timing and probability of success of meeting clinical and commercial milestones; and (iii) discount rates. The Company's contingent consideration liabilities arose in connection with its acquisition of Kolltan. On a quarterly basis, the Company revalues these obligations and record increases or decreases in their fair value as an adjustment to operating earnings. Changes to contingent consideration obligations can result from adjustments to discount rates, accretion of the discount rates due to the passage of time, changes in the Company's estimates of the likelihood or timing of achieving development or commercial milestones, changes in the probability of certain clinical events or changes in the assumed probability associated with regulatory approval. The assumptions related to determining the value of contingent consideration include a significant amount of judgment, and any changes in the underlying estimates could have a material impact on the amount of contingent consideration expense recorded in any given period. Intangible Assets IPR&D assets acquired in a business combination initially are recorded at fair value and accounted for as indefinite-lived intangible assets. These assets are capitalized on the Company's balance sheets until either the project underlying them is completed or the assets become impaired. If a project is completed, the carrying value of the related intangible asset is amortized over the remaining estimated life of the asset beginning in the period in which the project is completed. If a project becomes impaired or is abandoned, the carrying value of the related intangible asset is written down to its fair value and an impairment charge is taken in the period in which the impairment occurs. IPR&D assets are tested for impairment on an annual basis during the third quarter, or earlier if impairment indicators are present. As part of the annual impairment test of the IPR&D assets as of July 1, 2016, the Company performed a calculation of the fair value of the asset and concluded that the IPR&D assets were not impaired. Intangible assets acquired in a business combination with a finite life are recorded at fair value and amortized over the greater of economic consumption or on a straight-line basis over their estimated useful life. Goodwill The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is evaluated for impairment on an annual basis during the third quarter, or earlier if impairment indicators are present. The Company has the option to assess qualitative factors to determine if it is more likely than not that goodwill might be impaired and whether it is necessary to perform the two-step goodwill impairment test required under U.S. GAAP. As part of its annual impairment test of the goodwill asset as of July 1, 2016, the Company bypassed the optional qualitative assessment and performed the two-step impairment test. The Company concluded that goodwill was not impaired. Impairment of Intangible and Long-Lived Assets The Company evaluates the recoverability of its long-lived assets, including property and equipment, and intangible assets when circumstances indicate that an event of impairment may have occurred. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Revenue Recognition The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the seller's price to the buyer is fixed or determinable; and collectability is reasonably assured. The Company has entered into and in the future may enter into biopharmaceutical product development agreements with collaborative partners for the research and development of therapeutic drug candidates. The terms of the agreements may include nonrefundable signing and licensing fees, funding for research, development and manufacturing, milestone payments and royalties on any product sales derived from collaborations. These multiple element arrangements are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting. In accounting for these transactions, the Company allocates revenue to the various elements based on their relative fair value. The fair value of a revenue generating element can be based on current selling prices offered by the Company or another party for current products or the Company's best estimate of a selling price for future products. Revenue allocated to an individual element is recognized when all other revenue recognition criteria are met for that element. These collaborative and other agreements may contain milestone payments. Revenues from milestones, if they are considered substantive, are recognized upon successful accomplishment of the milestones. Determining whether a milestone is substantive involves judgment, including an assessment of the Company's involvement in achieving the milestones and whether the amount of the payment is commensurate to the Company's performance. If not considered substantive, milestones are initially deferred and recognized over the period of the remaining performance obligation. Payments received to fund certain research activities are recognized as revenue in the period in which the research activities are performed. Revenue from contracts and grants is recognized as the services are performed and recorded as effort is expended on the contracted work and billed to the government or the Company's contractual partner. Payments received in advance that are related to future performance are deferred and recognized as revenue when the research projects are performed. Product royalty revenue consists of payments received from licensees for a portion of sales proceeds from products that utilize the Company's licensed technologies and are recognized when the amount of and basis for such royalty payments are reported to the Company in accurate and appropriate form and in accordance with the related license agreement. Research and Development Expenses Research and development costs, including internal and contract research costs, are expensed as incurred. Research and development expenses consist mainly of clinical trial costs, manufacturing of clinical material, toxicology and other preclinical studies, personnel costs, depreciation, license fees and funding of outside contracted research. Clinical trial expenses include expenses associated with clinical research organizations, or CRO, services. Contract manufacturing expenses include expenses associated with contract manufacturing organizations, or CMO, services. The invoicing from CROs and CMOs for services rendered can lag several months. The Company accrues the cost of services rendered in connection with CRO and CMO activities based on our estimate of costs incurred. The Company maintains regular communication with our CROs and CMOs to assess the reasonableness of its estimates. Differences between actual expenses and estimated expenses recorded have not been material and are adjusted for in the period in which they become known. Patent Costs Patent costs are expensed as incurred. Certain patent costs are reimbursed by the Company's product development and licensing partners. Any reimbursed patent costs are recorded as product development and licensing agreement revenues in the Company's financial statements. Stock-Based Compensation The Company records stock-based compensation expense for all stock-based awards made to employees and directors based on the estimated fair values of the stock-based awards expected to vest at the grant date and is adjusted, if necessary, to reflect actual forfeitures. Compensation expense for all stock-based awards to employees and directors is recognized using the straight-line method over the term of vesting or performance. The Company records stock-based compensation expense for stock options granted to non-employees based on the fair value of the stock options which is re-measured over the graded vesting term resulting in periodic adjustments to stock-based compensation expense. Foreign Currency Translation Net unrealized gains and losses resulting from foreign currency translation are included in other comprehensive income (loss). At December 31, 2016 and December 31, 2015, accumulated other comprehensive income includes a net unrealized gain related to foreign currency translation of $2.6 million. Income Taxes The Company uses the asset and liability method to account for income taxes, including the recognition of deferred tax assets and deferred tax liabilities for the anticipated future tax consequences attributable to differences between financial statement amounts and their respective tax basis. Quarterly, the Company reviews its deferred tax assets for recovery. A valuation allowance is established when the Company believes that it is more likely than not that its deferred tax assets will not be realized. Changes in valuation allowances from period to period are included in the Company's tax provision in the period of change. The Company records uncertain tax positions in the financial statements only if it is more likely than not that the uncertain tax position will be sustained upon examination by the taxing authorities. The Company records interest and penalties related to uncertain tax positions in income tax expense. Comprehensive Loss Comprehensive loss is comprised of net loss and certain changes in stockholders' equity that are excluded from net loss. The Company includes foreign currency translation adjustments and unrealized gains and losses on marketable securities in other comprehensive loss. The statements of operations and comprehensive loss reflect total comprehensive loss for the years ended December 31, 2016, 2015 and 2014. Net Loss Per Share Basic net loss per common share is based upon the weighted-average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is based upon the weighted-average number of common shares outstanding during the period plus additional weighted-average potentially dilutive common shares outstanding during the period when the effect is dilutive. The potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive are as follows: Year Ended December 31, 2016 2015 2014 Stock options Restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption. In May 2014, the FASB issued a new U.S. GAAP accounting standard that creates modifications to various other revenue accounting standards for specialized transactions and industries. The new U.S. GAAP accounting standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. In August 2015, the FASB deferred the effective date of the new standard from January 1, 2017 to January 1, 2018. The amendment allows for two methods of adoption, a full retrospective method or a modified retrospective approach with the cumulative effect recognized at the date of initial application. The Company will further study the implications of this standard in order to evaluate the expected impact on the financial statements. In February 2016, the FASB issued a new U.S. GAAP accounting standard which requires that all lessees recognize the assets and liabilities that arise from leases on the balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for the Company on January 1, 2019. The Company is currently evaluating the potential impact that this standard may have on the Company's financial statements. In March 2016, the FASB issued a new U.S. GAAP accounting standard which involves 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. The new standard will be effective for the Company on January 1, 2017. The adoption of this standard is not expected to have a material impact on our financial statements. In June 2016, the FASB issued a new U.S. GAAP accounting standard which changes the impairment model for most financial assets and certain other instruments. Under the new standard, entities holding financial assets and net investment in leases that are not accounted for at fair value through net income to be presented at the net amount expected to be collected. An allowance for credit losses will be a valuation account that will be deducted from the amortized cost basis of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset. The new standard will be effective for the Company on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company's financial statements. In August 2016, the FASB issued a new U.S. GAAP accounting standard which clarifies certain aspects of the statement of cash flows, including the classification of debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees and beneficial interests in securitization transactions. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard will be effective for us on January 1, 2018. The Company is currently evaluating the potential impact that this standard may have on the Company's financial statements.

COMPREHENSIVE LOSS

COMPREHENSIVE LOSS	12 Months Ended
	Dec. 31, 2016
COMPREHENSIVE LOSS
COMPREHENSIVE LOSS	(3) COMPREHENSIVE LOSS The changes in accumulated other comprehensive income (loss) by component for the years ended December 31, 2016, 2015 and 2014 are summarized below. No amounts were reclassified out of accumulated other comprehensive income during the years ended December 31, 2016, 2015 and 2014. Unrealized Foreign Total (In thousands) Balance at December 31, 2013 $ $ $ Other comprehensive loss before reclassifications ) ) ) Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive loss ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2014 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive (loss) gain before reclassifications ) ) Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive (loss) gain ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2015 $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive gain before reclassifications — Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive gain — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2016 $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2016
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	(4) FAIR VALUE MEASUREMENTS The following tables set forth the Company's financial assets subject to fair value measurements: As of Level 1 Level 2 Level 3 (In thousands) Assets: Money market funds and cash equivalents $ — $ — Marketable securities $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of Level 1 Level 2 Level 3 (In thousands) Assets: Money market funds and cash equivalents $ — $ — Marketable securities $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Kolltan acquisition contingent consideration $ — — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration liabilities related to acquisitions are classified as Level 3 within the valuation hierarchy and are valued based on various estimates, including probability of success, discount rates and amount of time until the conditions of the milestone payments are met. In connection with the Kolltan acquisition, we may be required to pay future consideration that is contingent upon the achievement of specified development, regulatory approvals or sales-based milestone events. We determine the fair value of these obligations on the acquisition date using various estimates that are not observable in the market and represent a Level 3 measurement within the fair value hierarchy. The following table represents a roll-forward of our acquisition-related contingent consideration (in thousands): December 31, 2016 Balance at beginning of period $ — Milestone payments — Changes in fair value — Kolltan acquisition contingent consideration $ ​ ​ ​ ​ ​ Balance at end of period $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ There have been no transfers of assets or liabilities between the fair value measurement classifications. The Company's financial instruments consist mainly of cash and cash equivalents, marketable securities, short-term accounts receivable and accounts payable. The Company values its marketable securities utilizing independent pricing services which normally derive security prices from recently reported trades for identical or similar securities, making adjustments based on significant observable transactions. At each balance sheet date, observable market inputs may include trade information, broker or dealer quotes, bids, offers or a combination of these data sources. Short-term accounts receivable and accounts payable are reflected in the accompanying financial statements at cost, which approximates fair value due to the short-term nature of these instruments.

MARKETABLE SECURITIES

MARKETABLE SECURITIES	12 Months Ended
	Dec. 31, 2016
MARKETABLE SECURITIES
MARKETABLE SECURITIES	(5) MARKETABLE SECURITIES A summary of marketable securities is shown below: Amortized Gross Gross Fair (In thousands) December 31, 2016 Marketable securities U.S. government and municipal obligations Maturing in one year or less $ $ $ ) $ Maturing after one year through three years — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total U.S. government and municipal obligations $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities Maturing in one year or less $ $ — $ ) $ Maturing after one year through three years — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total corporate debt securities $ $ — $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total marketable securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2015 Marketable securities U.S. government and municipal obligations Maturing in one year or less $ $ $ ) $ Maturing after one year through three years ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total U.S. government and municipal obligations $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities Maturing in one year or less $ $ $ ) $ Maturing after one year through three years ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total corporate debt securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total marketable securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The marketable securities held by the Company were high investment grade and there were no marketable securities that the Company considered to be other-than-temporarily impaired as of December 31, 2016. Marketable securities include $0.6 million and $1.5 million in accrued interest at December 31, 2016 and December 31, 2015, respectively.

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2016
PROPERTY AND EQUIPMENT, NET
PROPERTY AND EQUIPMENT, NET	(6) PROPERTY AND EQUIPMENT, NET Property and equipment include the following: December 31, December 31, (In thousands) Laboratory Equipment $ $ Manufacturing Equipment Office Furniture and Equipment Leasehold Improvements Construction in Progress ​ ​ ​ ​ ​ ​ ​ ​ Total Property and Equipment Less Accumulated Depreciation and Amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation and amortization expense related to property and equipment was $3.1 million, $3.0 million and $2.4 million for the years ended December 31, 2016, 2015 and 2014, respectively.

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	12 Months Ended
	Dec. 31, 2016
INTANGIBLE ASSETS AND GOODWILL
INTANGIBLE ASSETS AND GOODWILL	(7) INTANGIBLE ASSETS AND GOODWILL Intangible assets, net of accumulated amortization, and goodwill are as follows: December 31, 2016 December 31, 2015 Estimated Life Cost Accumulated Net Cost Accumulated Net (In thousands) Intangible Assets: IPR&D Indefinite $ $ — $ $ $ — $ Amgen Amendment 16 years ) ) Core Technology 11 years ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Intangible Assets $ $ ) $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill Indefinite $ $ — $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The IPR&D intangible asset recorded in connection with the CuraGen acquisition of $11.8 million relates to the development of glembatumumab vedotin. At the date of acquisition and at December 31, 2016, glembatumumab vedotin had not yet reached technological feasibility nor did it have any alternative future use. Glembatumumab vedotin is in a randomized, Phase 2b study for the treatment of triple negative breast cancer and a Phase 2 study for the treatment of metastatic melanoma. The IPR&D intangible asset recorded in connection with the Kolltan acquisition of $61.7 million relates to the development of the CDX-1058, CDX-3379 and TAM programs. At the date of acquisition and at December 31, 2016, the CDX-1058, CDX-3379 and TAM programs had not yet reached technological feasibility nor did they have any alternative future use. CDX-0158 is a humanized monoclonal antibody currently in a Phase 1 dose escalation study in refractory gastrointestinal stromal tumors and CDX-3379 is a human monoclonal antibody which recently completed a Phase 1b study in patients with solid tumors. The TAM program is a multi-faceted broad antibody discovery effort to generate antibodies that modulate the TAM family of RTKs, comprised of Tyro3, AXL and MerTK, which are expressed on tumor-infiltrating macrophages, dendritic cells and some tumors. Amortization expense for intangible assets was $1.0 million for the years ended December 31, 2016, 2015 and 2014. The estimated future amortization expense of intangible assets for the years ending December 31, 2017, 2018, 2019, 2020 and 2021 is $0.9 million, $0.9 million, $0.9 million, $0.9 million and $0.9 million, respectively.

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2016
ACCRUED EXPENSES
ACCRUED EXPENSES	(8) ACCRUED EXPENSES Accrued expenses include the following: December 31, December 31, (In thousands) Accrued Payroll and Employee Benefits $ $ Accrued Research and Development Contract Costs Accrued Professional Fees Other Accrued Expenses ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

OTHER LONG-TERM LIABILITIES

OTHER LONG-TERM LIABILITIES	12 Months Ended
	Dec. 31, 2016
OTHER LONG-TERM LIABILITIES
OTHER LONG-TERM LIABILITIES	(9) OTHER LONG-TERM LIABILITIES Other long-term liabilities include the following: December 31, December 31, (In thousands) Deferred Rent $ $ Net Deferred Tax Liability related to IPR&D (Note 17) Deferred Income from Sale of Tax Benefits Needham Expansion Restructuring (Note 18) — Long-Term Severance (Note 17) — Contingent Milestones (Note 17) — Deferred Revenue ​ ​ ​ ​ ​ ​ ​ ​ Total Less Current Portion ) ) ​ ​ ​ ​ ​ ​ ​ ​ Long-Term Portion $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In November 2015, December 2014, January 2014, January 2013 and January 2012, the Company received approval from the New Jersey Economic Development Authority and agreed to sell New Jersey tax benefits of $9.8 million, $1.9 million, $1.1 million, $0.8 million and $0.8 million to an independent third party for $9.2 million, $1.8 million, $1.0 million, $0.8 million and $0.7 million, respectively. Under the agreement, the Company must maintain a base of operations in New Jersey for five years or the tax benefits must be paid back on a pro-rata basis based on the number of years completed. During the years ended December 31, 2016, 2015 and 2014, the Company recorded $2.8 million, $1.0 million and $0.4 million to other income related to the sale of these tax benefits, respectively.

STOCKHOLDER'S EQUITY

STOCKHOLDER'S EQUITY	12 Months Ended
	Dec. 31, 2016
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	(10) STOCKHOLDERS' EQUITY Common Stock In December 2013, the Company filed an automatic shelf registration statement with the Securities and Exchange Commission to register for sale any combination of the types of securities described in the shelf registration statement. In December 2016, the Company filed a new shelf registration statement with the Securities and Exchange Commission to register for sale any combination of the types of securities described in the shelf registration statement up to a maximum aggregate offering price of $250 million. Such registration statement was declared effective on February 13, 2017. During the year ended December 31, 2014, the Company entered into an amended and restated supply agreement with Biosyn Corporation. Under the supply agreement, Biosyn will manufacture and supply keyhole limpet hemocyanin (KLH) to the Company for use in connection with the development, manufacture or commercial sale of Rintega. In connection with the supply agreement, the Company issued to Biosyn 152,172 shares of its common stock having a value of $2.0 million. During the years ended December 31, 2016, 2015 and 2014, the Company recorded $1.6 million, $0.3 million and $0.1 million to research and development expense related to this supply agreement, respectively. During the year ended December 31, 2015, the Company issued 8,337,500 shares of its common stock in underwritten public offerings resulting in net proceeds to the Company of $188.8 million, after deducting underwriting fees and offering expenses. During the year ended December 31, 2016, the Company entered into a research and collaboration agreement with an undisclosed private company to access novel technologies and paid $3.5 million to support research activities and make an investment in the private company. The Company initially recorded $1.8 million to other assets related to this investment and $1.7 million was recorded to prepaid and other currents assets and is being amortized over the term of the agreement. At December 31, 2016, $0.7 million remained recorded to prepaid research related to this collaboration. In May 2016, the Company entered into an agreement with Cantor Fitzgerald & Co. ("Cantor") to allow the Company to issue and sell shares of its common stock having an aggregate offering price of up to $60.0 million from time to time through Cantor, acting as agent. During the year ended December 31, 2016, Company issued 3,303,800 shares of its common stock under this controlled equity offering sales agreement with Cantor resulting in net proceeds to the Company of $13.9 million, after deducting commission and offering expenses. Convertible Preferred Stock At December 31, 2016, the Company had authorized 3,000,000 shares of preferred stock all of which have been designated Class C Preferred Stock including 350,000 shares which have been designated Series C-1 Junior Participating Cumulative Preferred Stock (the "Series C-1 Preferred Stock").

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2016
STOCK-BASED COMPENSATION
STOCK-BASED COMPENSATION	(11) STOCK-BASED COMPENSATION The Company has the following stock-based compensation plans: the 2004 Employee Stock Purchase Plan (the "2004 ESPP Plan"), the 2008 Stock Option and Incentive Plan (the "2008 Plan") and Celldex Research's 2005 Equity Incentive Plan (the "Celldex Research 2005 Plan"). There are no shares available for future grant under the Celldex Research 2005 Plan. Employee Stock Purchase Plan At December 31, 2016, a total of 200,000 shares of common stock are reserved for issuance under the 2004 ESPP Plan. Under the 2004 ESPP Plan, each participating employee may purchase shares of common stock through payroll deductions at a purchase price equal to 85% of the lower of the fair market value of the common stock at either the beginning of the offering period or the applicable exercise date. During the years ended December 31, 2016 and 2015, the Company issued 59,335 and 15,755 shares under the 2004 ESPP Plan, respectively. At December 31, 2016, 78,236 shares were available for issuance under the 2004 ESPP Plan. Employee Stock Option and Incentive Plan The 2008 Plan permits the granting of incentive stock options (intended to qualify as such under Section 422A of the Internal Revenue Code of 1986, as amended), non-qualified stock options, stock appreciation rights, performance share units, restricted stock and other awards of restricted stock in lieu of cash bonuses to employees, consultants and non-employee directors. At December 31, 2016, the 2008 Plan allowed for a maximum of 14,350,000 shares of common stock to be issued for grants of Stock Options and other Awards made prior to June 9, 2025 and grants of Incentive Stock Options made prior to April 16, 2025. The Company's board of directors determines the term of each option, option price, and number of shares for which each option is granted and the rate at which each option vests. Options generally vest over a period not to exceed four years. The term of each option cannot exceed ten years (five years for options granted to holders of more than 10% of the voting stock of the Company) and the exercise price of stock options cannot be less than the fair market value of the common stock at the date of grant (110% of fair market value for incentive stock options granted to holders of more than 10% of the voting stock of the Company). Vesting of all employee and non-employee director stock option awards may accelerate upon a change in control as defined in the 2008 Plan. A summary of stock option activity for the year ended December 31, 2016 is as follows: Shares Weighted Weighted Options Outstanding at December 31, 2015 $ Granted $ Exercised ) $ Canceled ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Vested and Expected to Vest at December 31, 2016 $ Options Exercisable at December 31, 2016 $ Shares Available for Grant under the 2008 Plan The total intrinsic value of stock options exercised during the years ended December 31, 2016, 2015 and 2014 was $0.1 million, $14.4 million and $2.7 million, respectively. The weighted average grant-date fair value of stock options granted during the years ended December 31, 2016, 2015 and 2014 was $3.18, $15.25 and $8.82, respectively. The total fair value of stock options vested during the years ended December 31, 2016, 2015 and 2014 was $17.0 million, $10.0 million and $5.7 million, respectively. The aggregate intrinsic value of stock options outstanding at December 31, 2016 was $0.4 million. The aggregate intrinsic value of stock options vested and expected to vest at December 31, 2016 was $0.4 million. As of December 31, 2016, total compensation cost related to non-vested employee and non-employee director stock options not yet recognized was approximately $27.4 million, net of estimated forfeitures, which is expected to be recognized as expense over a weighted average period of 2.8 years. Restricted Stock A summary of restricted stock activity under the 2008 Plan for the year ended December 31, 2016 is as follows: Shares Weighted Outstanding and unvested at December 31, 2015 $ Granted $ Vested ) $ Canceled ) $ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding and unvested at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Valuation and Expenses Information Stock-based compensation expense for the years ended December 31, 2016, 2015 and 2014 was recorded as follows: 2016 2015 2014 (In thousands) Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total stock-based compensation expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The fair values of employee stock options granted during the years ended December 31, 2016, 2015 and 2014 were valued using the Black-Scholes option-pricing model with the following assumptions: Year Ended Year Ended Year Ended Expected stock price volatility 70 - 77% 67 - 69% 70 - 72% Expected option term 6.0 Years 6.0 Years 6.0 Years Risk-free interest rate 1.4 - 2.3% 1.8 - 2.2% 1.9 - 2.2% Expected dividend yield None None None The Company estimates expected term based on historical exercise patterns. The Company uses its historical stock price volatility consistent with the expected term of grant as the basis for its expected volatility assumption. The risk-free interest rate is based upon the yield of U.S. Treasury securities consistent with the expected term of the option. The dividend yield assumption is based on the Company's history of zero dividend payouts and expectation that no dividends will be paid in the foreseeable future.

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2016
REVENUE
REVENUE	(12) REVENUE Bristol-Myers Squibb Company (BMS) In May 2014, the Company entered into a clinical trial collaboration with BMS to evaluate the safety, tolerability and preliminary efficacy of varlilumab and Opdivo®, BMS's PD-1 immune checkpoint inhibitor, in a Phase 1/2 study. Under the terms of this clinical trial collaboration, BMS made a one-time payment to the Company of $5.0 million and BMS and the Company amended the terms of the Company's existing license agreement with Medarex, which was acquired by BMS, related to the Company's CD27 program whereby certain future milestone payments were waived and future royalty rates were reduced that may have been due from the Company to Medarex. In return, BMS was granted a time-limited right of first negotiation if the Company wishes to out-license varlilumab. The companies also agreed to work exclusively with each other to explore anti-PD-1 antagonist antibody and anti-CD27 agonist antibody combination regimens. The clinical trial collaboration provides that the companies will share development costs and that the Company will be responsible for conducting the ongoing Phase 1/2 study. The Company has determined that its performance obligations under the BMS agreement, which primarily include performing research and development, supplying varlilumab and participating in the joint development committee, should be accounted for as a single unit of accounting and estimated that its performance period under the BMS agreement would be 5 years. Accordingly, the $5.0 million up-front payment was initially recorded as deferred revenue and is being recognized as revenue on a straight-line basis over the estimated 5-year performance period using the Contingency Adjusted Performance Model ("CAPM"). The BMS agreement also provides for BMS to reimburse the Company for 50% of the external costs incurred by the Company in connection with the clinical trial. These BMS payments are being recognized as revenue using the CAPM. The Company recorded $2.1 million, $1.3 million and $0.7 million in revenue related to the BMS agreement during the year ended December 31, 2016, 2015 and 2014, respectively. Rockefeller University (Rockefeller) In September 2013, the Company entered into an agreement, as amended, with Rockefeller pursuant to which the Company performs research and development services for Rockefeller. The Company bills Rockefeller quarterly for actual time and direct costs incurred and records those amounts to revenue in the quarter the services are performed. The Company recorded $2.7 million, $3.4 million and $2.7 million in revenue related to the Rockefeller agreement during the years ended December 31, 2016, 2015 and 2014, respectively.

COLLABORATION AGREEMENTS

COLLABORATION AGREEMENTS	12 Months Ended
	Dec. 31, 2016
COLLABORATION AGREEMENTS
COLLABORATION AGREEMENTS	(13) COLLABORATION AGREEMENTS The Company has entered into license agreements whereby the Company has received licenses or options to license technology, specified patents or patent applications. The Company's licensing and development collaboration agreements generally provide for royalty payments equal to specified percentages of product sales, annual license maintenance fees, continuing patent prosecution costs and potential future milestone payments to third parties upon the achievement of certain developmental, regulatory and/or commercial milestones. Nonrefundable license fee expense of $1.6 million, $0.9 million and $3.2 million was recorded to research and development expense for the years ended December 31, 2016, 2015 and 2014, respectively. Medarex, Inc. (Medarex), which was acquired by Bristol-Myers Squibb The Company and Medarex have entered into an assignment and license agreement, as amended, that provides for the assignment of certain patent and other intellectual property rights and a license to certain Medarex technology related to the Company's APC Targeting Technology™ and an anti-mannose receptor product. Under the terms of the agreement, the Company may be required to pay royalties in the low-single digits on any net product sale of a Licensed Royalty-Bearing Product or Anti-Mannose Product to Medarex until the later of (i) the expiration of the last to expire applicable patent and (ii) the tenth anniversary of the first commercial sale of such licensed product. The Company and Medarex have also entered into a research and commercialization agreement, as amended, that provides that the Company may be required to pay Medarex milestones of up to $7.0 million upon obtaining first approval for commercial sale in a first indication of a product containing a licensed antibody and royalty payments in the low-to-mid single digits on any net product sales with respect to the development of any products containing such licensed antibodies until the later of (i) the expiration of the last to expire applicable patent and (ii) the tenth anniversary of the first commercial sale of such licensed product. In September 2010, the Company exercised an option under the agreement, whereby it licensed from Medarex access to the UltiMab technology to develop and commercialize human antibodies to CD27, including varlilumab. In connection with the clinical trial collaboration, the Company entered into with BMS in May 2014, certain future milestone payments were waived and future royalty rates that the Company may have owed Medarex in connection with any CD27 program were reduced. Rockefeller University (Rockefeller) In November 2005, the Company and Rockefeller entered into a license agreement for the exclusive worldwide rights to human DEC-205 receptor, with the right to sublicense the technology. The license grant is exclusive except that Rockefeller may use and permit other nonprofit organizations to use the human DEC-205 receptor patent rights for educational and research purposes. The Company may be required to pay Rockefeller milestones of up to $3.8 million upon obtaining first approval for commercial sale in a first indication of a product targeting the licensed receptor and royalty payments in the low-to-mid single digits on any net product sales with respect to development and commercialization of the human DEC-205 receptor. University of Southampton, UK (Southampton) In November 2008, the Company entered into a license agreement with Southampton to develop human antibodies towards CD27, a potentially important target for immunotherapy of various cancers. The Company may be required to pay Southampton milestones of up to approximately $1.0 million upon obtaining first approval for commercial sale in a first indication and royalty payments in the low-single digits on any net product sales with respect to development and commercialization of varlilumab. Amgen Inc. (Amgen) In March 2009, the Company entered into a license agreement with Amgen to acquire the exclusive rights to CDX-301 and CD40 ligand (CD40L). CDX-301 and CD40L are immune modulating molecules that increase the numbers and activity of immune cells that control immune responses. The Company may be required to pay Amgen milestones of up to $0.9 million upon obtaining first approval for commercial sale in a first indication and royalty payments in the low-single digits on any net product sales with respect to development and commercialization of the technology licensed from Amgen, including CDX-301. Seattle Genetics, Inc. (Seattle Genetics) In connection with the acquisition of CuraGen, the Company assumed the license agreement between CuraGen and Seattle Genetics whereby CuraGen acquired the rights to proprietary antibody-drug conjugate (ADC) technology for use with the Company's proprietary antibodies for the potential treatment of cancer. The Company may be required to pay Seattle Genetics milestones of up to $5.0 million and $8.5 million for glembatumumab vedotin and CDX-014, respectively, upon obtaining first approval for commercial sale in a first indication and royalty payments in the mid-single digits on any net product sales with respect to development and commercialization of these drug candidates.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2016
INCOME TAXES
INCOME TAXES	(14) INCOME TAXES The components of income tax expense attributable to continuing operations consist of the following: Year Ended December 31, 2016 2015 2014 (In thousands) Income tax benefit (provision): Federal $ $ $ State Foreign — — Expiration of Net Operating Losses and Research & Development Tax Credits — ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax valuation allowance ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A reconciliation between the amount of reported income tax and the amount computed using the U.S. Statutory rate of 34% follows: 2016 2015 2014 (In thousands) Pre-tax loss $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss at Statutory Rates ) ) ) Difference in Foreign Tax Rates — — Research and Development Credits ) ) ) State Taxes ) ) ) Other Expiration of Net Operating Losses and Research & Development Tax Credits — Change in Valuation Allowance ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Company incurred a foreign pre-tax loss of $3.7 million during the year ended December 31, 2016. Deferred tax assets and liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using future expected enacted rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. The principal components of the deferred tax assets and liabilities at December 31, 2016 and 2015, respectively, are as follows: December 31, December 31, (In thousands) Gross Deferred Tax Assets Net Operating Loss Carryforwards $ $ Foreign Net Operating Loss Carryforwards — Tax Credit Carryforwards Deferred Research and Development Expenses Stock-based Compensation Fixed Assets Deferred Revenue Accrued Expenses and Other ​ ​ ​ ​ ​ ​ ​ ​ Gross Deferred Tax Liabilities Other Acquired Intangibles ) ) IPR&D Intangibles ) ) ​ ​ ​ ​ ​ ​ ​ ​ ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total Deferred Tax Assets and Liabilities Deferred Tax Assets Valuation Allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net Deferred Tax Asset (Liability) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The net deferred tax liability of $28.1 million and $4.7 million at December 31, 2016 and 2015, respectively relates to the temporary differences associated with the IPR&D intangible assets acquired in the Kolltan and CuraGen acquisitions, respectively, which are not deductible for tax purposes. Since the IPR&D intangible assets are indefinite-lived, the related deferred tax liability cannot be netted against definite-lived deferred tax assets to reduce the valuation allowance required. As of December 31, 2016, the Company had the following federal net operating loss ("NOL") carryforwards: • Prior to the merger of the Company and AVANT, $33.0 million was generated by the Company which expire at various dates starting in 2023 and going through 2028; • Prior to the merger of the Company and AVANT, $101.2 million, net of expirations and utilization, was generated by AVANT which expire at various dates starting in 2018 and going through 2028; • Following the merger of the Company and AVANT, $356.7 million was generated by the combined company which expire at various dates starting in 2028 and going through 2036; and • Prior to its acquisition by the Company, $518.3 million was generated by CuraGen. • Prior to its acquisition by the Company, $110.5 million was generated by Kolltan Pharmaceuticals, Inc. As of December 31, 2016, the Company had foreign net operating loss carryforwards of $3.7 million which can be carried forward indefinitely. As of December 31, 2016, the Company has an additional $17.7 million of federal and state net operating losses not reflected above, that are attributable to stock option exercises which will be recorded as an increase in additional paid in capital on the balance sheet once they are "realized" in accordance with ASC 718. As of December 31, 2016, the Company had federal and state net operating loss carryforwards of $458.5 million and $344.9 million, respectively, which may be available to offset certain future income tax liabilities and begin to expire in 2018 and 2028, respectively. As of December 31, 2016, the Company also had federal and state research and development tax credit carryforwards of $26.1 million and $9.4 million, respectively, which may be available to offset future income tax liabilities and begin to expire in 2018 and 2017, respectively. Utilization of the net operating loss carryforwards and research and credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company has estimated the amounts of net operating loss and research and development tax credit carryforwards which will expire unutilized as a result of its estimated annual limitations under Section 382, and has excluded those amounts from the carryforward amounts disclosed in this paragraph and in the deferred tax assets and liabilities table included in this footnote. The Company has concluded Section 382 studies through 2015 for Celldex generated NOLs. The Company as a stand-alone company experienced a change in ownership in October 2007. As a result of the ownership changes in October 2007, utilization of the Company's NOLs prior to October 2007 is subject to an annual limitation of $4.5 million on $28.3 million of NOLs generated before that date. As a result of the ownership changes in June 2009 and December 2009, there is an annual limitation amount of $6.0 million on $67.7 million of NOLs generated before that date. As a result of the ownership change in December 2013, there is an annual limitation amount of $77.0 million on $178.7 million of NOLs generated before that date. Any unused annual limitation may be carried over to later years, and the amount of the limitation may, under certain circumstances, be subject to adjustment if the fair value of the Company's net assets are determined to be below or in excess of the tax basis of such assets at the time of the ownership change, and such unrealized loss or gain is recognized during the five year period after the ownership change. However, the Company has not completed a 382 study to assess whether a change of control has occurred for the NOLs it has acquired in its various acquisitions, including most recently Kolltan, or whether there have been multiple changes of control since inception, particularly within the ownership of acquired entities prior to their acquisition by the Company, due to the significant complexity and cost associated with such a study. If the Company or its acquired entities have experienced additional changes of control, as defined by Section 382, at any time since inception, utilization of the net operating loss carryforwards or research and development tax credit carryforwards could be subject to additional annual limitations under Section 382, which are determined by first multiplying the value of the Company's stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any additional limitations may result in expiration of a portion of the net operating loss carryforwards or research and development tax credit carryforwards before utilization. Further, until a study is completed and any additional limitations are known, no amounts are being presented as an uncertain tax positions. The Company applies the authoritative guidance on account for and disclosure of uncertainty in income tax positions which requires the Company to determine whether an income tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. For income tax positions meeting the more likely than not threshold, the tax amount recognized in the financial statements is reduced to the largest benefit that has a greater than 50% likelihood of being realized upon the ultimate settlement with the relevant taxing authority. At December 31, 2016 and 2015, we had no unrecognized tax benefits. A full valuation allowance has been provided against our deferred tax assets and liabilities and, if an adjustment for unrecognized tax benefits is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the balance sheet or statement of operations if an adjustment were required. Massachusetts, New Jersey and Connecticut are the three states in which the Company primarily operates or has operated and has income tax nexus. The Company is not currently under examination by these or any other jurisdictions for any tax year. For federal and state jurisdictions, all years which generated net operating losses and/or tax credit carryforwards remain subject to examination to the extent those carryforwards are utilized in a subsequent period. The Company has evaluated the positive and negative evidence bearing upon the realizability of its net deferred tax assets, which are comprised principally of net operating loss carryforwards, capitalized R&D expenditures and R&D tax credit carryforwards. The Company has determined that it is more likely than not that it will not recognize the benefits of federal and state deferred tax assets and, as a result, a full valuation allowance was maintained at December 31, 2016 against the Company's net deferred tax assets. The net increase in the valuation allowance during the year ended December 31, 2016 primarily related to an increase in deferred tax assets for research and development expenses which have been deferred for tax purposes.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	(15) COMMITMENTS AND CONTINGENCIES The Company has facility and equipment leases that expire at various dates through 2020. Certain of these facility leases contain renewal options, early termination provisions, and provisions that escalate the base rent payments and require the Company to pay common area maintenance costs ("CAM") during the lease term. The following obligations for base rent and CAM costs under facility and other non-cancelable operating leases as of December 31, 2016 do not include the exercise of renewal terms or early termination provisions (in thousands): 2017 $ 2018 2019 2020 2021 — Thereafter — ​ ​ ​ ​ ​ Total minimum lease payments $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Company's total rent and CAM expense for all facility leases was $4.8 million, $2.9 million and $2.7 million for the years ended December 31, 2016, 2015 and 2014, respectively.

RETIREMENT SAVINGS PLAN

RETIREMENT SAVINGS PLAN	12 Months Ended
	Dec. 31, 2016
RETIREMENT SAVINGS PLAN
RETIREMENT SAVINGS PLAN	(16) RETIREMENT SAVINGS PLAN The Company maintains a 401(k) Plan which is available to substantially all employees. Under the terms of the 401(k) Plan, participants may elect to contribute up to 60% of their compensation, or the statutory prescribed limits. The Company may make 50% matching contributions on up to 4% of a participant's annual salary. Benefit expense for the 401(k) Plan was $0.4 million, $0.4 million and $0.3 million for the years ended December 31, 2016, 2015 and 2014, respectively.

KOLLTAN ACQUISITION

KOLLTAN ACQUISITION	12 Months Ended
	Dec. 31, 2016
KOLLTAN ACQUISITION
KOLLTAN ACQUISITION	(17) KOLLTAN ACQUISITION In connection with the Kolltan Acquisition, effective November 29, 2016, the Company issued 18,257,996 shares of common stock of the Company in exchange for all of the share and debt interests in Kolltan. Following closing, certain officers of Kolltan will receive an aggregate of 437,901 shares of Celldex's common stock in lieu of cash severance obligations, less tax withholdings. In December 2016, the Company issued 111,111 shares of Celldex's common stock as partial payment of this obligation. In addition, in the event that certain specified preclinical and clinical development milestones related to Kolltan's development programs and/or Celldex's development programs and certain commercial milestones related to Kolltan's drug candidates are achieved, Celldex will be required to pay Kolltan's stockholders milestone payments of up to $172.5 million, which milestone payments may be made, at Celldex's sole election, in cash, in shares of Celldex's common stock or a combination of both, subject to NASDAQ listing requirements and provisions of the Merger Agreement. The Company acquired Kolltan to gain access to Kolltan's programs including: (i) CLDX-0158 (formerly KTN0158) which is currently in a Phase 1 dose escalation study in patient with refractory gastrointestinal stromal tumors (GIST); (ii) CLDX-3379 (formerly KTN3379) which recently completed a Phase 1b study with combination cohorts where meaningful responses and stable disease were observed in cetuximab (Erbitux®) refractory patients in patients with head and neck squamous cell carcinoma and in BRAF-mutant non-small cell lung cancer (NSCLC); and (iii) a multi-faceted TAM program, a broad antibody discovery effort underway to generate antibodies that modulate the TAM family of RTKs, comprised of Tyro3, AXL and MerTK, which are expressed on tumor-infiltrating macrophages, dendritic cells and some tumors. The transaction is being accounted for as a business combination with Celldex treated as the accounting acquirer. All of the assets acquired and liabilities assumed in the transaction are recognized at their acquisition-date fair values, while transaction costs associated with the transaction are expensed as incurred. Purchase Price The purchase price for Kolltan is based on the acquisition-date fair value of the consideration transferred, which was calculated based on the closing price of the Company's common stock of $4.02 per share on November 29, 2016. The acquisition-date fair value of the consideration transferred consisted of the following (in thousands): Fair value of common stock issued for upfront payment $ Fair value of contingent consideration Kolltan transaction expenses paid in cash by the Company ​ ​ ​ ​ ​ Total consideration transferred $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The contingent consideration relates to the achievement of certain regulatory and sales milestones as described in the agreement. The estimate of fair value of contingent consideration was $44.2 million at the acquisition date and at December 31, 2016, which was recorded as a noncurrent liability. The Company determined the fair value of these obligations to pay additional milestone payments using various estimates, including probabilities of success, discount rates and amount of time until the conditions of the milestone payments are met. This fair value measurement is based on significant inputs not observable in the market, representing a Level 3 measurement within the fair value hierarchy. The resulting probability-weighted cash flows were discounted using a cost of debt rate ranging from 10-11% for the milestones. The range of estimated milestone payments is from zero, if no milestones are achieved, to $172.5 million if all milestones are met. In the future, if the estimate of the fair value of the contingent consideration changes, the changes in fair value will be recognized in operating earnings. Changes in fair values reflect new information about the probability and timing of meeting the conditions of the milestone payments. In the absence of new information, changes in fair value will only reflect the interest component of contingent consideration related to the passage of time as development work progresses towards the achievement of the milestones. Allocations of Assets and Liabilities The Company has allocated the consideration transferred for Kolltan to net tangible assets, intangible assets, and goodwill. The difference between the aggregate consideration transferred and the fair value of assets acquired and liabilities assumed was allocated to goodwill. This goodwill relates to the potential synergies from the Kolltan Acquisition and a deferred tax liability related to acquired IPR&D intangible assets. None of the goodwill is expected to be deductible for income tax purposes. The following table summarizes the fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands): Cash and cash equivalents $ Other current and long-term assets Property and Equipment, Net In-process research and development (IPR&D) Goodwill Deferred tax liabilities, net ) Other assumed liabilities ) ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The purchase price allocation has been prepared on a preliminary basis and is subject to change as additional information becomes available concerning the fair value and tax basis of the acquired assets and liabilities. Any adjustments to the purchase price allocation will be made as soon as practicable but no later than one year from the acquisition date. The estimated fair value attributed to IPR&D intangible assets represents an estimate of the fair value of purchased in-process technology for Kolltan's research programs that, as of November 29, 2016, had not reached technological feasibility and have no alternative future use. Only those research programs that had advanced to a stage of development where the Company believed reasonable net future cash flow forecasts could be prepared and a reasonable likelihood of technical success existed were included in the estimated fair value. Accordingly, the IPR&D programs primarily represent the estimated fair value of $40.0 million, $3.5 million and $18.0 million for the CDX-0158, CDX-3379 and TAM programs, respectively. The estimated fair value of the IPR&D programs was determined based on estimates of expected future net cash flows. These expected future net cash flows included estimates for revenue and associated costs for the IPR&D programs based on (i) relevant industry factors, (ii) current and expected trends in the product development life cycle, (iii) the ability to engage a strategic partner, (iv) the ability to obtain regulatory approval, and (v) the ability to manufacture and commercialize the products. The probability-adjusted future net cash flows which reflect the different stages of development of each program are then present valued utilizing an estimate of the appropriate discount rate which is consistent with the uncertainties of the cash flows utilized. The expected future net cash flows for the CDX-0158, CDX-3379 and TAM programs were based on the expectation that a Biologics License Application ("BLA") would be filed with the FDA no earlier than the end of 2023, 2024, and 2028, respectively. The Company expects the commercial launch as promptly as commercially practicable after necessary regulatory approvals are received. The estimated development costs included in the expected future net cash flows was approximately $132 million. These assumptions require various levels of in-house and external testing, clinical trials and approvals from the FDA or comparable foreign regulatory authorities before the CDX-0158, CDX-3379 and TAM programs could be commercialized in the U.S. or other territories. Drug development involves a high degree of risk and most products that make it into clinical development do not receive marketing approval. Numerous risks and uncertainties can delay or stop clinical development of a pharmaceutical product prior to the receipt of marketing approval, including, but not limited to, results from clinical trials that do not support continuing development, issues related to manufacturing or intellectual property protection, and other events or circumstances that cause unanticipated delays, technical problems or other difficulties. Given these risks and uncertainties, there can be no assurance that the development of the CDX-0158, CDX-3379 and TAM programs will be successfully completed. If the development of the CDX-0158, CDX-3379 and TAM programs are not successful, in whole or in part, or completed in a timely manner, the Company may not realize the expected financial benefits from the development of the CDX-0158, CDX-3379 and TAM programs or the transaction as a whole. The deferred tax liability, net of $23.4 million primarily relates to the temporary differences associated with the IPR&D intangible assets, which are not deductible for tax purposes. Acquisition-Related Expenses, Including Severance The Company incurred $0.7 million in acquisition-related expenses in the consolidated statements of operations for the year ended December 31, 2016. These costs include fees for legal, accounting, due diligence, tax, valuation, printing and other various services necessary to complete the transaction. In addition, the Company recorded $2.4 million and $0.7 million in Kolltan severance expenses to general and administrative and research and development, respectively, in the consolidated statements of operations for the year ended December 31, 2016 since the severance was determined to be for the benefit of the Company. Pro Forma Financial Information The operating results of Kolltan and pro forma adjustments including severance expense and transaction expenses of $3.1 million and $0.7 million, respectively, have been included in the accompanying consolidated financial statements from November 29, 2016 to December 31, 2016. Kolltan had no revenues from November 29, 2016 through December 31, 2016. The following unaudited pro forma financial summary is presented as if the operations of the Company and Kolltan were combined as of January 1, 2015. The unaudited pro forma combined results are not necessarily indicative of the actual results that would have occurred had the acquisition been consummated at that date or of the future operations of the combined entities. Unaudited 2016 2015 (In thousands) Revenue $ $ Net loss $ ) $ ) Basic and Diluted Net Loss Per Common Share $ ) $ )

RESTRUCTURING EXPENSE

RESTRUCTURING EXPENSE	12 Months Ended
	Dec. 31, 2016
RESTRUCTURING EXPENSE
RESTRUCTURING EXPENSE	(18) RESTRUCTURING EXPENSE In December 2016, the Company decided not to occupy the 11,500 square feet of expansion space ("Needham Expansion") at its Needham, Massachusetts facility. The Company agreed to lease the Needham Expansion in August 2015 and the term of the lease expires in July 2020. The Company is actively trying to sublease the lease obligation. The Company recorded restructuring expenses of $1.2 million to general and administrative expense for the twelve months ended December 31, 2016. The activity related to restructuring for the twelve months ended December 31, 2016, is presented below (in thousands): Charge for Cash Payments Accrual as of (In thousands) Needham Expansion $ $ — $ Short-term portion of lease accrual ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Long-term portion of lease accrual $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In accordance with U.S. GAAP, the Company recorded an initial estimate, at fair value, in the fourth quarter of 2016. The Company will review its assumptions and estimates quarterly and updates the liability as changes in circumstances require. The liability recorded with respect to the potential lease restructuring was calculated using probability weighted discounted cash flows based on the Company's assumptions and estimates regarding the possible outcomes of the potential time to sublease the space and sublease rental rates. The Company used a credit-adjusted risk-free rate of approximately 10% to discount the estimated cash flows. The expense and liability related to the potential lease restructuring requires the Company to make significant estimates and assumptions. The Company will review the estimates and assumptions on at least a quarterly basis, until the outcome is finalized, and make whatever modifications management believes to be necessary, based on the Company's best judgment, to reflect any changed circumstances. It is possible that such estimates could change in the future resulting in additional adjustments. Because the Company's estimate of the liability related to the potential lease restructuring includes the application of a discount rate to reflect the time value of money, the estimate of the liability will change as a result of time passing. Any such changes to the Company's estimate of the liability are recorded as additional restructuring and other expense.

SELECTED QUARTERLY FINANCIAL DA

SELECTED QUARTERLY FINANCIAL DATA (Unaudited)	12 Months Ended
	Dec. 31, 2016
SELECTED QUARTERLY FINANCIAL DATA (Unaudited)
SELECTED QUARTERLY FINANCIAL DATA (Unaudited)	(19) SELECTED QUARTERLY FINANCIAL DATA (Unaudited) 2015 Q1 2015 Q2 2015 Q3 2015 Q4 2015 (In thousands, except per share amounts) Total revenue $ $ $ $ Net loss ) ) ) ) Basic and diluted net loss per common share ) ) ) ) 2016 Q1 2016 Q2 2016 Q3 2016 Q4 2016 (In thousands, except per share amounts) Total revenue $ $ $ $ Net loss ) ) ) ) Basic and diluted net loss per common share ) ) ) )

SUMMARY OF SIGNIFICANT ACCOUN26

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2016
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation	Basis of Presentation Following the Kolltan Acquisition, the consolidated financial statements reflect the financial position, results of operation and cash flows of the combined companies. Accordingly, this report reflects the financial condition as of December 31, 2016 and the results of operations and cash flows for the period from the Kolltan Acquisition on November 29, 2016 through December 31, 2016. On December 31, 2016, the Company completed the merger of Kolltan with and into Celldex pursuant to a short-form merger effected under Delaware law. As a result, the separate corporate existence of Kolltan has ceased and the Company has succeeded to all rights, privileges, powers and franchises of Kolltan. On December 31, 2014, the Company's wholly-owned subsidiary, Celldex Research Corporation, merged into Celldex Therapeutics, Inc. In February 2016, the Company formed a wholly-owned subsidiary, Celldex Therapeutics Europe GmbH, in Zug, Switzerland. In July 2016, we formed a wholly-owned subsidiary, Celldex Australia Pty Ltd, in Brisbane, Australia. The statements of operations and comprehensive loss, of stockholders' equity, and of cash flows, are consolidated for the years ended December 31, 2016 and 2014. These consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary prior to the merger. All intercompany balances and transactions have been eliminated in consolidation. The Company operates in one segment, which is the business of development, manufacturing and commercialization of novel therapeutics for human health care.
Use of Estimates	Use of Estimates The preparation of the financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and use assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the dates of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with a maturity date of 90 days or less at the date of purchase to be cash equivalents. Cash equivalents consist principally of money market funds and debt securities.
Marketable Securities	Marketable Securities The Company invests its excess cash balances in marketable securities including municipal bond securities, U.S. government agency securities, and high-grade corporate bonds. The Company classifies all of its marketable securities as current assets on the balance sheets because they are available-for-sale and available to fund current operations. Marketable securities are stated at fair value with their unrealized gains and losses included as a component of accumulated other comprehensive income (loss), which is a separate component of stockholders' equity, until such gains and losses are realized. If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is transferred from other comprehensive income (loss) to the statements of operations. Realized gains and losses are determined on the specific identification method and are included in investment and other income, net.
Concentration of Credit Risk and of Significant Customers and Suppliers	Concentration of Credit Risk and of Significant Customers and Suppliers Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash, cash equivalents, marketable securities and accounts receivable. The Company invests its cash, cash equivalents and marketable securities in debt instruments and interest bearing accounts at major financial institutions in excess of insured limits. The Company mitigates credit risk by limiting the investment type and maturity to securities that preserve capital, maintain liquidity and have a high credit quality. The Company has not historically experienced credit losses from its accounts receivable and therefore has not established an allowance for doubtful accounts. Revenue from Rockefeller and BMS represented 40% and 31% for the year ended December 31, 2016, 62% and 24% for the year ended December 31, 2015, and 75% and 20% for the year ended December 31, 2014, of total Company revenue, respectively. The Company relies on contract manufacturing organizations (CMO) to manufacture drug substance and drug product for its late-stage clinical study of glembatumumab vedotin as well as for future commercial supplies. The Company also relies on CMOs for supply of raw materials as well as filling, packaging, storage and shipping of drug product. These clinical studies would be adversely affected by a significant interruption in the supply of glembatumumab vedotin. The Company also relies on third-party collaborators to develop companion diagnostic tests for certain of its drug candidates, including glembatumumab vedotin.
Fair Value Measurements	Fair Value Measurements The Company has certain assets and liabilities that are measured at fair value in the financial statements. The Company seeks to maximize the use of observable inputs (market data obtained from sources independent from the Company) and to minimize the use of unobservable inputs (the Company's assumptions about how market participants would price assets and liabilities) when measuring the fair value of its assets and liabilities. These assets and liabilities are classified into one of three levels of the following fair value hierarchy as defined by U.S. GAAP: Level 1: Observable inputs such as quoted prices in active markets for identical assets or liabilities. An active market for an asset or liability is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2: Observable inputs other than Level 1 prices, such as quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active. Level 3: Unobservable inputs based on the Company's assessment of the assumptions that market participants would use in pricing the asset or liability.
Property and Equipment	Property and Equipment Property and equipment is stated at cost and depreciated over the estimated useful lives of the related assets using the straight-line method. Laboratory equipment and office furniture and equipment are depreciated over five years and computer equipment is depreciated over three years. Manufacturing equipment is amortized over seven to ten years. Leasehold improvements are amortized over the shorter of the estimated useful life or the non-cancelable term of the related lease, including any renewals that are reasonably assured of occurring. Property and equipment under construction is classified as construction in progress and is depreciated or amortized only after the asset is placed in service. Expenditures for maintenance and repairs are charged to expense whereas the costs of significant improvements which extend the life of the underlying asset are capitalized. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are eliminated and any resulting gain or loss is reflected in the Company's statements of operations and comprehensive loss. The treatment of costs to construct property and equipment depends on the nature of the costs and the stage of construction. Costs incurred in the project planning, design, construction and installation phases are capitalized as part of the cost of the asset. The Company stops capitalizing these costs when the asset is substantially complete and ready for its intended use. For manufacturing property and equipment, the Company also capitalizes the cost of validating these assets for the underlying manufacturing process. The Company completes the capitalization of validation costs when the asset is substantially complete and ready for its intended use. Costs capitalized include incremental labor and fringe benefits, and direct consultancy services.
Business Combinations	Business Combinations The Company records the fair value of the consideration transferred to acquire a business to the tangible assets and identifiable intangible assets acquired and liabilities assumed on the basis of their fair values at the date of acquisition. The Company assesses the fair value of assets, including intangible assets such as in-process research and development (IPR&D), using a variety of methods including present value models. Each asset is measured at fair value from the perspective of a market participant. The method used to estimate the fair values of IPR&D assets incorporates significant assumptions regarding the estimates a market participant would make in order to evaluate an asset, including a market participant's assumptions regarding the probability of completing IPR&D projects, which would require obtaining regulatory approval for marketing of the associated drug candidate; a market participant's estimates regarding the timing of and the expected costs to complete IPR&D projects; a market participant's estimates of future cash flows from potential product sales; and the appropriate discount rates for a market participant. Transaction costs and restructuring costs associated with the transaction are expensed as incurred. The Company records contingent consideration resulting from a business combination at its fair value on the acquisition date. The Company determines the fair value of the contingent consideration based primarily on the (i) timing and probability of success of clinical events or regulatory approvals; (ii) timing and probability of success of meeting clinical and commercial milestones; and (iii) discount rates. The Company's contingent consideration liabilities arose in connection with its acquisition of Kolltan. On a quarterly basis, the Company revalues these obligations and record increases or decreases in their fair value as an adjustment to operating earnings. Changes to contingent consideration obligations can result from adjustments to discount rates, accretion of the discount rates due to the passage of time, changes in the Company's estimates of the likelihood or timing of achieving development or commercial milestones, changes in the probability of certain clinical events or changes in the assumed probability associated with regulatory approval. The assumptions related to determining the value of contingent consideration include a significant amount of judgment, and any changes in the underlying estimates could have a material impact on the amount of contingent consideration expense recorded in any given period.
Intangible Assets	Intangible Assets IPR&D assets acquired in a business combination initially are recorded at fair value and accounted for as indefinite-lived intangible assets. These assets are capitalized on the Company's balance sheets until either the project underlying them is completed or the assets become impaired. If a project is completed, the carrying value of the related intangible asset is amortized over the remaining estimated life of the asset beginning in the period in which the project is completed. If a project becomes impaired or is abandoned, the carrying value of the related intangible asset is written down to its fair value and an impairment charge is taken in the period in which the impairment occurs. IPR&D assets are tested for impairment on an annual basis during the third quarter, or earlier if impairment indicators are present. As part of the annual impairment test of the IPR&D assets as of July 1, 2016, the Company performed a calculation of the fair value of the asset and concluded that the IPR&D assets were not impaired. Intangible assets acquired in a business combination with a finite life are recorded at fair value and amortized over the greater of economic consumption or on a straight-line basis over their estimated useful life.
Goodwill	Goodwill The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is evaluated for impairment on an annual basis during the third quarter, or earlier if impairment indicators are present. The Company has the option to assess qualitative factors to determine if it is more likely than not that goodwill might be impaired and whether it is necessary to perform the two-step goodwill impairment test required under U.S. GAAP. As part of its annual impairment test of the goodwill asset as of July 1, 2016, the Company bypassed the optional qualitative assessment and performed the two-step impairment test. The Company concluded that goodwill was not impaired.
Impairment of Intangible and Long-Lived Assets	Impairment of Intangible and Long-Lived Assets The Company evaluates the recoverability of its long-lived assets, including property and equipment, and intangible assets when circumstances indicate that an event of impairment may have occurred. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the seller's price to the buyer is fixed or determinable; and collectability is reasonably assured. The Company has entered into and in the future may enter into biopharmaceutical product development agreements with collaborative partners for the research and development of therapeutic drug candidates. The terms of the agreements may include nonrefundable signing and licensing fees, funding for research, development and manufacturing, milestone payments and royalties on any product sales derived from collaborations. These multiple element arrangements are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting. In accounting for these transactions, the Company allocates revenue to the various elements based on their relative fair value. The fair value of a revenue generating element can be based on current selling prices offered by the Company or another party for current products or the Company's best estimate of a selling price for future products. Revenue allocated to an individual element is recognized when all other revenue recognition criteria are met for that element. These collaborative and other agreements may contain milestone payments. Revenues from milestones, if they are considered substantive, are recognized upon successful accomplishment of the milestones. Determining whether a milestone is substantive involves judgment, including an assessment of the Company's involvement in achieving the milestones and whether the amount of the payment is commensurate to the Company's performance. If not considered substantive, milestones are initially deferred and recognized over the period of the remaining performance obligation. Payments received to fund certain research activities are recognized as revenue in the period in which the research activities are performed. Revenue from contracts and grants is recognized as the services are performed and recorded as effort is expended on the contracted work and billed to the government or the Company's contractual partner. Payments received in advance that are related to future performance are deferred and recognized as revenue when the research projects are performed. Product royalty revenue consists of payments received from licensees for a portion of sales proceeds from products that utilize the Company's licensed technologies and are recognized when the amount of and basis for such royalty payments are reported to the Company in accurate and appropriate form and in accordance with the related license agreement.
Research and Development Expenses	Research and Development Expenses Research and development costs, including internal and contract research costs, are expensed as incurred. Research and development expenses consist mainly of clinical trial costs, manufacturing of clinical material, toxicology and other preclinical studies, personnel costs, depreciation, license fees and funding of outside contracted research. Clinical trial expenses include expenses associated with clinical research organizations, or CRO, services. Contract manufacturing expenses include expenses associated with contract manufacturing organizations, or CMO, services. The invoicing from CROs and CMOs for services rendered can lag several months. The Company accrues the cost of services rendered in connection with CRO and CMO activities based on our estimate of costs incurred. The Company maintains regular communication with our CROs and CMOs to assess the reasonableness of its estimates. Differences between actual expenses and estimated expenses recorded have not been material and are adjusted for in the period in which they become known.
Patent Costs	Patent Costs Patent costs are expensed as incurred. Certain patent costs are reimbursed by the Company's product development and licensing partners. Any reimbursed patent costs are recorded as product development and licensing agreement revenues in the Company's financial statements.
Stock-Based Compensation	Stock-Based Compensation The Company records stock-based compensation expense for all stock-based awards made to employees and directors based on the estimated fair values of the stock-based awards expected to vest at the grant date and is adjusted, if necessary, to reflect actual forfeitures. Compensation expense for all stock-based awards to employees and directors is recognized using the straight-line method over the term of vesting or performance. The Company records stock-based compensation expense for stock options granted to non-employees based on the fair value of the stock options which is re-measured over the graded vesting term resulting in periodic adjustments to stock-based compensation expense.
Foreign Currency Translation	Foreign Currency Translation Net unrealized gains and losses resulting from foreign currency translation are included in other comprehensive income (loss). At December 31, 2016 and December 31, 2015, accumulated other comprehensive income includes a net unrealized gain related to foreign currency translation of $2.6 million.
Income Taxes	Income Taxes The Company uses the asset and liability method to account for income taxes, including the recognition of deferred tax assets and deferred tax liabilities for the anticipated future tax consequences attributable to differences between financial statement amounts and their respective tax basis. Quarterly, the Company reviews its deferred tax assets for recovery. A valuation allowance is established when the Company believes that it is more likely than not that its deferred tax assets will not be realized. Changes in valuation allowances from period to period are included in the Company's tax provision in the period of change. The Company records uncertain tax positions in the financial statements only if it is more likely than not that the uncertain tax position will be sustained upon examination by the taxing authorities. The Company records interest and penalties related to uncertain tax positions in income tax expense.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and certain changes in stockholders' equity that are excluded from net loss. The Company includes foreign currency translation adjustments and unrealized gains and losses on marketable securities in other comprehensive loss. The statements of operations and comprehensive loss reflect total comprehensive loss for the years ended December 31, 2016, 2015 and 2014.
Net Loss Per Share	Net Loss Per Share Basic net loss per common share is based upon the weighted-average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is based upon the weighted-average number of common shares outstanding during the period plus additional weighted-average potentially dilutive common shares outstanding during the period when the effect is dilutive. The potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive are as follows: Year Ended December 31, 2016 2015 2014 Stock options Restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption. In May 2014, the FASB issued a new U.S. GAAP accounting standard that creates modifications to various other revenue accounting standards for specialized transactions and industries. The new U.S. GAAP accounting standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. In August 2015, the FASB deferred the effective date of the new standard from January 1, 2017 to January 1, 2018. The amendment allows for two methods of adoption, a full retrospective method or a modified retrospective approach with the cumulative effect recognized at the date of initial application. The Company will further study the implications of this standard in order to evaluate the expected impact on the financial statements. In February 2016, the FASB issued a new U.S. GAAP accounting standard which requires that all lessees recognize the assets and liabilities that arise from leases on the balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for the Company on January 1, 2019. The Company is currently evaluating the potential impact that this standard may have on the Company's financial statements. In March 2016, the FASB issued a new U.S. GAAP accounting standard which involves 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. The new standard will be effective for the Company on January 1, 2017. The adoption of this standard is not expected to have a material impact on our financial statements. In June 2016, the FASB issued a new U.S. GAAP accounting standard which changes the impairment model for most financial assets and certain other instruments. Under the new standard, entities holding financial assets and net investment in leases that are not accounted for at fair value through net income to be presented at the net amount expected to be collected. An allowance for credit losses will be a valuation account that will be deducted from the amortized cost basis of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset. The new standard will be effective for the Company on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company's financial statements. In August 2016, the FASB issued a new U.S. GAAP accounting standard which clarifies certain aspects of the statement of cash flows, including the classification of debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees and beneficial interests in securitization transactions. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard will be effective for us on January 1, 2018. The Company is currently evaluating the potential impact that this standard may have on the Company's financial statements.

SUMMARY OF SIGNIFICANT ACCOUN27

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2016
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive	Year Ended December 31, 2016 2015 2014 Stock options Restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

COMPREHENSIVE LOSS (Tables)

COMPREHENSIVE LOSS (Tables)	12 Months Ended
	Dec. 31, 2016
COMPREHENSIVE LOSS
Summary of changes in accumulated other comprehensive income (loss) by component	Unrealized Foreign Total (In thousands) Balance at December 31, 2013 $ $ $ Other comprehensive loss before reclassifications ) ) ) Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive loss ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2014 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive (loss) gain before reclassifications ) ) Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive (loss) gain ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2015 $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive gain before reclassifications — Amounts reclassified from other comprehensive income — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive gain — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2016 $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

FAIR VALUE MEASUREMENTS (Table)

FAIR VALUE MEASUREMENTS (Table)	12 Months Ended
	Dec. 31, 2016
FAIR VALUE MEASUREMENTS
Schedule of financial assets subject to fair value measurements	As of Level 1 Level 2 Level 3 (In thousands) Assets: Money market funds and cash equivalents $ — $ — Marketable securities $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of Level 1 Level 2 Level 3 (In thousands) Assets: Money market funds and cash equivalents $ — $ — Marketable securities $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Kolltan acquisition contingent consideration $ — — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of acquisition-related contingent consideration	December 31, 2016 Balance at beginning of period $ — Milestone payments — Changes in fair value — Kolltan acquisition contingent consideration $ ​ ​ ​ ​ ​ Balance at end of period $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2016
MARKETABLE SECURITIES
Summary of marketable securities	Amortized Gross Gross Fair (In thousands) December 31, 2016 Marketable securities U.S. government and municipal obligations Maturing in one year or less $ $ $ ) $ Maturing after one year through three years — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total U.S. government and municipal obligations $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities Maturing in one year or less $ $ — $ ) $ Maturing after one year through three years — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total corporate debt securities $ $ — $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total marketable securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2015 Marketable securities U.S. government and municipal obligations Maturing in one year or less $ $ $ ) $ Maturing after one year through three years ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total U.S. government and municipal obligations $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities Maturing in one year or less $ $ $ ) $ Maturing after one year through three years ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total corporate debt securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total marketable securities $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2016
PROPERTY AND EQUIPMENT, NET
Schedule of property and equipment	December 31, December 31, (In thousands) Laboratory Equipment $ $ Manufacturing Equipment Office Furniture and Equipment Leasehold Improvements Construction in Progress ​ ​ ​ ​ ​ ​ ​ ​ Total Property and Equipment Less Accumulated Depreciation and Amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	12 Months Ended
	Dec. 31, 2016
INTANGIBLE ASSETS AND GOODWILL
Schedule of intangible assets, net of accumulated amortization, and goodwill	December 31, 2016 December 31, 2015 Estimated Life Cost Accumulated Net Cost Accumulated Net (In thousands) Intangible Assets: IPR&D Indefinite $ $ — $ $ $ — $ Amgen Amendment 16 years ) ) Core Technology 11 years ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Intangible Assets $ $ ) $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill Indefinite $ $ — $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2016
ACCRUED EXPENSES
Schedule of accrued expenses	December 31, December 31, (In thousands) Accrued Payroll and Employee Benefits $ $ Accrued Research and Development Contract Costs Accrued Professional Fees Other Accrued Expenses ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

OTHER LONG-TERM LIABILITIES (Ta

OTHER LONG-TERM LIABILITIES (Tables)	12 Months Ended
	Dec. 31, 2016
OTHER LONG-TERM LIABILITIES
Schedule of other long-term liabilities	December 31, December 31, (In thousands) Deferred Rent $ $ Net Deferred Tax Liability related to IPR&D (Note 17) Deferred Income from Sale of Tax Benefits Needham Expansion Restructuring (Note 18) — Long-Term Severance (Note 17) — Contingent Milestones (Note 17) — Deferred Revenue ​ ​ ​ ​ ​ ​ ​ ​ Total Less Current Portion ) ) ​ ​ ​ ​ ​ ​ ​ ​ Long-Term Portion $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2016
STOCK-BASED COMPENSATION
Summary of stock option activity	Shares Weighted Weighted Options Outstanding at December 31, 2015 $ Granted $ Exercised ) $ Canceled ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Vested and Expected to Vest at December 31, 2016 $ Options Exercisable at December 31, 2016 $ Shares Available for Grant under the 2008 Plan
Summary of restricted stock activity	Shares Weighted Outstanding and unvested at December 31, 2015 $ Granted $ Vested ) $ Canceled ) $ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding and unvested at December 31, 2016 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of stock-based compensation expense	2016 2015 2014 (In thousands) Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total stock-based compensation expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of assumptions used for the fair values of employee and director stock options granted	Year Ended Year Ended Year Ended Expected stock price volatility 70 - 77% 67 - 69% 70 - 72% Expected option term 6.0 Years 6.0 Years 6.0 Years Risk-free interest rate 1.4 - 2.3% 1.8 - 2.2% 1.9 - 2.2% Expected dividend yield None None None

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2016
INCOME TAXES
Schedule of components of income tax expense attributable to continuing operations	Year Ended December 31, 2016 2015 2014 (In thousands) Income tax benefit (provision): Federal $ $ $ State Foreign — — Expiration of Net Operating Losses and Research & Development Tax Credits — ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax valuation allowance ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation between the amount of reported income tax and the amount computed using the U.S. Statutory rate	2016 2015 2014 (In thousands) Pre-tax loss $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss at Statutory Rates ) ) ) Difference in Foreign Tax Rates — — Research and Development Credits ) ) ) State Taxes ) ) ) Other Expiration of Net Operating Losses and Research & Development Tax Credits — Change in Valuation Allowance ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of principal components of the deferred tax assets and liabilities	December 31, December 31, (In thousands) Gross Deferred Tax Assets Net Operating Loss Carryforwards $ $ Foreign Net Operating Loss Carryforwards — Tax Credit Carryforwards Deferred Research and Development Expenses Stock-based Compensation Fixed Assets Deferred Revenue Accrued Expenses and Other ​ ​ ​ ​ ​ ​ ​ ​ Gross Deferred Tax Liabilities Other Acquired Intangibles ) ) IPR&D Intangibles ) ) ​ ​ ​ ​ ​ ​ ​ ​ ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total Deferred Tax Assets and Liabilities Deferred Tax Assets Valuation Allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net Deferred Tax Asset (Liability) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
Schedule of obligations for base rent and CAM costs under facility and other non-cancelable operating leases	The following obligations for base rent and CAM costs under facility and other non-cancelable operating leases as of December 31, 2016 do not include the exercise of renewal terms or early termination provisions (in thousands): 2017 $ 2018 2019 2020 2021 — Thereafter — ​ ​ ​ ​ ​ Total minimum lease payments $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

KOLLTAN ACQUISITION (Tables)

KOLLTAN ACQUISITION (Tables)	12 Months Ended
	Dec. 31, 2016
KOLLTAN ACQUISITION
Schedule of acquisition-date fair value of the consideration transferred	The acquisition-date fair value of the consideration transferred consisted of the following (in thousands): Fair value of common stock issued for upfront payment $ Fair value of contingent consideration Kolltan transaction expenses paid in cash by the Company ​ ​ ​ ​ ​ Total consideration transferred $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of fair values of the assets acquired and liabilities assumed at the acquisition date	The following table summarizes the fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands): Cash and cash equivalents $ Other current and long-term assets Property and Equipment, Net In-process research and development (IPR&D) Goodwill Deferred tax liabilities, net ) Other assumed liabilities ) ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of the unaudited pro forma financial information	Unaudited 2016 2015 (In thousands) Revenue $ $ Net loss $ ) $ ) Basic and Diluted Net Loss Per Common Share $ ) $ )

RESTRUCTURING EXPENSE (Tables)

RESTRUCTURING EXPENSE (Tables)	12 Months Ended
	Dec. 31, 2016
RESTRUCTURING EXPENSE
Schedule of activity related to restructuring	Charge for Cash Payments Accrual as of (In thousands) Needham Expansion $ $ — $ Short-term portion of lease accrual ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Long-term portion of lease accrual $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

SELECTED QUARTERLY FINANCIAL 40

SELECTED QUARTERLY FINANCIAL DATA (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
SELECTED QUARTERLY FINANCIAL DATA (Unaudited)
Schedule of selected quarterly financial data (unaudited)	2015 Q1 2015 Q2 2015 Q3 2015 Q4 2015 (In thousands, except per share amounts) Total revenue $ $ $ $ Net loss ) ) ) ) Basic and diluted net loss per common share ) ) ) ) 2016 Q1 2016 Q2 2016 Q3 2016 Q4 2016 (In thousands, except per share amounts) Total revenue $ $ $ $ Net loss ) ) ) ) Basic and diluted net loss per common share ) ) ) )

NATURE OF BUSINESS AND OVERVI41

NATURE OF BUSINESS AND OVERVIEW - (Details) $ in Thousands	Nov. 29, 2016USD ($)shares	Dec. 31, 2016USD ($)itemshares	Dec. 31, 2016USD ($)item	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)item	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
NATURE OF BUSINESS AND OVERVIEW
Number of drug candidates in clinical development | item		7	7								7
Cash, cash equivalents and marketable securities		$ 189,800	$ 189,800								$ 189,800
Net Loss			$ (32,307)	$ (29,598)	$ (31,952)	$ (34,673)	$ (32,684)	$ (31,980)	$ (32,359)	$ (30,174)	(128,530)	$ (127,197)	$ (118,080)
Net cash used in operations											$ 113,036	$ 98,887	$ 101,537
Minimum number of programs delayed or discontinued if unable to raise funds necessary to meet long-term liquidity needs | item											1
Kolltan
NATURE OF BUSINESS AND OVERVIEW
Shares issued as part of consideration (in shares) | shares	18,257,996
Shares issuable in lieu of cash severance obligations (in shares) | shares	437,901
Shares issued in lieu of cash severance obligations (in shares) | shares		111,111
Maximum amount of milestone payments	$ 172,500
Days used for comparable average closing price (in days)	5 days
Ending day of comparable average closing prices (in days)	3 days
Threshold of stock issuance which would require stockholder approval (percentage)	19.9

SUMMARY OF SIGNIFICANT ACCOUN42

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - CONCENTRATION OF CREDIT RISK (Details) - segment	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basis of Presentation
Number of operating segments	1
Revenue | Customer concentration | Rockefeller
Concentration risk
Concentration risk (as a percent)	40.00%	62.00%	75.00%
Revenue | Customer concentration | BMS
Concentration risk
Concentration risk (as a percent)	31.00%	24.00%	20.00%

SUMMARY OF SIGNIFICANT ACCOUN43

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PROPERTY AND EQUIPMENT (Details)	12 Months Ended
	Dec. 31, 2016
Laboratory Equipment
Property and Equipment
Estimated useful lives	5 years
Office Furniture and Equipment
Property and Equipment
Estimated useful lives	5 years
Computer Equipment
Property and Equipment
Estimated useful lives	3 years
Manufacturing Equipment | Minimum
Property and Equipment
Estimated useful lives	7 years
Manufacturing Equipment | Maximum
Property and Equipment
Estimated useful lives	10 years

SUMMARY OF SIGNIFICANT ACCOUN44

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - FOREIGN CURRENCY TRANSLATION (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Foreign Currency Translation
Net unrealized gain related to foreign currency translation included in accumulated other comprehensive income	$ 2.6	$ 2.6

SUMMARY OF SIGNIFICANT ACCOUN45

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - DILUTIVE COMMON SHARES (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net loss per share
Potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive	10,268,710	8,129,739	7,022,350
Stock options
Net loss per share
Potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive	10,218,710	8,110,239	7,015,350
Restricted stock
Net loss per share
Potentially dilutive common shares that have not been included in the net loss per common share calculations because the effect would have been anti-dilutive	50,000	19,500	7,000

COMPREHENSIVE LOSS (Details)

COMPREHENSIVE LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in accumulated other comprehensive income (loss) by component
Balance	$ 290,105	$ 211,660	$ 319,795
Balance	265,431	290,105	211,660
Unrealized Gain (Loss) on Marketable Securities
Changes in accumulated other comprehensive income (loss) by component
Balance	(289)	9	82
Other comprehensive (loss) gain before reclassifications	234	(298)	(73)
Net current-period other comprehensive (loss) gain	234	(298)	(73)
Balance	(55)	(289)	9
Foreign Currency Items
Changes in accumulated other comprehensive income (loss) by component
Balance	2,596	2,581	2,586
Other comprehensive (loss) gain before reclassifications		15	(5)
Net current-period other comprehensive (loss) gain		15	(5)
Balance	2,596	2,596	2,581
Accumulated Other Comprehensive Income
Changes in accumulated other comprehensive income (loss) by component
Balance	2,307	2,590	2,668
Other comprehensive (loss) gain before reclassifications	234	(283)	(78)
Net current-period other comprehensive (loss) gain	234	(283)	(78)
Balance	$ 2,541	$ 2,307	$ 2,590

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Liabilities:
Assets transferred between the fair value measurement classifications	$ 0
Liabilities transferred between the fair value measurement classifications	0
Fair value | Level 3
Liabilities:
Kolltan acquisition contingent consideration	44,200
Total financial liabilities at fair value	44,200
Fair Value Measurements | Level 2
Assets:
Money market funds and cash equivalents	20,445	$ 59,831
Marketable securities	147,315	217,781
Total financial assets at fair value	167,760	277,612
Fair Value Measurements | Fair value
Assets:
Money market funds and cash equivalents	20,445	59,831
Marketable securities	147,315	217,781
Total financial assets at fair value	167,760	$ 277,612
Liabilities:
Kolltan acquisition contingent consideration	44,200
Total financial liabilities at fair value	$ 44,200

MARKETABLE SECURITIES (Details)

MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost
Amortized cost	$ 147,370	$ 218,070
Gross Unrealized Gains
Gross Unrealized Gains	13	31
Gross Unrealized Losses
Gross Unrealized Losses	(68)	(320)
Fair Value
Fair Value	147,315	217,781
Marketable securities considered to be other-than-temporarily impaired	0
Accrued interest included in marketable securities	600	1,500
U.S. government and municipal obligations
Amortized Cost
Maturing in one year or less	52,754	48,871
Maturing after one year through three years	296	15,940
Amortized cost	53,050	64,811
Gross Unrealized Gains
Maturing in one year or less	5	4
Maturing after one year through three years	8	24
Gross Unrealized Gains	13	28
Gross Unrealized Losses
Maturing in one year or less	(12)	(20)
Maturing after one year through three years		(57)
Gross Unrealized Losses	(12)	(77)
Fair Value
Maturing in one year or less	52,747	48,855
Maturing after one year through three years	304	15,907
Fair Value	53,051	64,762
Corporate debt securities
Amortized Cost
Maturing in one year or less	94,320	129,327
Maturing after one year through three years		23,932
Amortized cost	94,320	153,259
Gross Unrealized Gains
Maturing in one year or less		2
Maturing after one year through three years		1
Gross Unrealized Gains		3
Gross Unrealized Losses
Maturing in one year or less	(56)	(141)
Maturing after one year through three years		(102)
Gross Unrealized Losses	(56)	(243)
Fair Value
Maturing in one year or less	94,264	129,188
Maturing after one year through three years		23,831
Fair Value	$ 94,264	$ 153,019

PROPERTY AND EQUIPMENT, NET (De

PROPERTY AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment
Total Property and Equipment	$ 33,158	$ 28,520
Less Accumulated Depreciation and Amortization	(19,966)	(17,059)
Property and Equipment, Net	13,192	11,461
Depreciation and amortization expense	3,095	2,998	$ 2,388
Laboratory Equipment
Property and Equipment
Total Property and Equipment	6,771	5,432
Manufacturing Equipment
Property and Equipment
Total Property and Equipment	4,312	4,178
Office Furniture and Equipment
Property and Equipment
Total Property and Equipment	3,677	3,088
Leasehold Improvements
Property and Equipment
Total Property and Equipment	17,115	15,371
Construction in Progress
Property and Equipment
Total Property and Equipment	$ 1,283	$ 451

INTANGIBLE ASSETS AND GOODWIL50

INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 29, 2016
Intangible Assets and Goodwill
Goodwill	$ 90,976	$ 8,965
Finite-lived intangible asset
Accumulated Amortization	(7,799)	(6,802)
Total Intangible Assets
Cost of total intangible assets	89,286	27,596
Intangible Assets, Net (Excluding Goodwill)	81,487	20,794
Amortization expense for intangible assets	997	1,013	$ 1,013
Estimated future amortization expense of intangible assets
2,017	900
2,018	900
2,019	900
2,020	900
2,021	$ 900
Kolltan
Intangible Assets and Goodwill
Goodwill				$ 82,011
Amgen Amendment
Finite-lived intangible asset
Estimated Life	16 years
Cost	$ 14,500	14,500
Accumulated Amortization	(6,503)	(5,605)
Net	$ 7,997	8,895
Core Technology
Finite-lived intangible asset
Estimated Life	11 years
Cost	$ 1,296	1,296
Accumulated Amortization	(1,296)	(1,197)
Net		99
IPR&D
Indefinite-lived intangible assets:
Indefinite-lived intangible assets	73,490	$ 11,800
IPR&D | CuraGen
Indefinite-lived intangible assets:
Indefinite-lived intangible assets	11,800
IPR&D | Kolltan
Indefinite-lived intangible assets:
Indefinite-lived intangible assets	$ 61,700

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
ACCRUED EXPENSES
Accrued Payroll and Employee Benefits	$ 7,132	$ 5,601
Accrued Research and Development Contract Costs	17,742	14,548
Accrued Professional Fees	1,146	399
Other Accrued Expenses	2,637	3,768
Accrued Expenses	$ 28,657	$ 24,316

OTHER LONG-TERM LIABILITIES (De

OTHER LONG-TERM LIABILITIES (Details) - USD ($) $ in Thousands	1 Months Ended					12 Months Ended
	Nov. 30, 2015	Dec. 31, 2014	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OTHER LONG-TERM LIABILITIES
Deferred Rent						$ 398	$ 409
Net Deferred Tax Liability related to IPR&D (Note 17)						28,054	4,661
Deferred Income from Sale of Tax Benefits						9,436	12,219
Needham Expansion Restructuring (Note 18)						1,154
Long-Term Severance (Note 17)						539
Contingent Milestones (Note 17)						44,200
Deferred Revenue						3,749	4,368
Total						87,530	21,657
Less Current Portion						(4,826)	(4,418)
Long-Term Portion						$ 82,704	17,239
Amount at which New Jersey tax benefit agreed to be sold	$ 9,800	$ 1,900	$ 1,100	$ 800	$ 800
Amount of sale of New Jersey tax benefit	$ 9,200	$ 1,800	$ 1,000	$ 800	$ 700
Period for which base of operations must be maintained						5 years
Other income related to sale of tax benefits						$ 2,800	$ 1,000	$ 400

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 31, 2016
Stockholders' Equity
Maximum aggregate offering price of securities in shelf registration statement	$ 250,000
Common Stock, Shares Issued	120,516,654	98,685,595
Shares Issued in Connection with Supply Agreement			$ 2,000
Research and development expense	$ 102,726	$ 100,171	$ 104,381
Net proceeds from sale of stock		188,840
Other assets	2,134	1,428
Prepaid and other current assets	4,009	4,077
Net proceeds from sale of common stock	$ 13,946	$ 188,840
Preferred stock, shares authorized	3,000,000	3,000,000
Amended and restated supply agreement
Stockholders' Equity
Common Stock, Shares Issued			152,172
Shares Issued in Connection with Supply Agreement			$ 2,000
Research and development expense	$ 1,600	$ 300	$ 100
Research and collaboration agreement
Stockholders' Equity
Payment for research and collaboration agreement and investment in company	3,500
Other assets	1,800
Prepaid and other current assets	1,700
Prepaid research	$ 700
Cantor agreement
Stockholders' Equity
Common stock issued (in shares)	3,303,800
Net proceeds from sale of common stock	$ 13,900
Cantor agreement | Maximum
Stockholders' Equity
Common stock available for sale (in shares)				60,000,000
Underwritten Public Offering
Stockholders' Equity
Common stock issued (in shares)		8,337,500
Net proceeds from sale of stock		$ 188,800
Class C Preferred Stock
Stockholders' Equity
Preferred stock, shares authorized	3,000,000
Series C-1 Preferred Stock
Stockholders' Equity
Preferred stock, shares authorized	350,000

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summary of Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
2004 ESPP Plan
Stock-Based Compensation
Common stock reserved for issuance (in shares)	200,000
Purchase price as a percentage of the lower of the fair market value of the common stock at either the beginning of the offering period or the applicable exercise date	85.00%
Shares issued under the plan	59,335	15,755
Shares
Shares Available for Grant (in shares)	78,236
Celldex Research 2005 Plan
Shares
Shares Available for Grant (in shares)	0
2008 Plan
Stock-Based Compensation
Maximum shares of common stock to be issued for grants (in shares)	14,350,000
Terms of options granted to the holders of more than 10% of the voting stock	5 years
Threshold percentage of voting stock	10.00%
Exercise price as a percentage of fair market value for options granted to the holders of more than 10% of the voting stock	110.00%
2008 Plan | Maximum
Stock-Based Compensation
Vesting period	4 years
Terms of options	10 years
2008 Plan | Stock options
Shares
Options Outstanding at beginning of the period (in shares)	8,110,239
Granted (in shares)	2,464,750
Exercised (in shares)	(48,817)
Canceled (in shares)	(307,462)
Options Outstanding at the end of the period (in shares)	10,218,710	8,110,239
Options Vested and Expected to Vest at the end of the period (in shares)	10,148,728
Options Exercisable at the end of the period (in shares)	6,086,840
Shares Available for Grant (in shares)	3,577,635
Weighted Average Exercise Price Per Share
Options Outstanding at beginning of the period (in dollars per share)	$ 13.13
Granted (in dollars per share)	4.78
Exercised (in dollars per share)	2.90
Canceled (in dollars per share)	14.05
Options Outstanding at the end of the period (in dollars per share)	11.14	$ 13.13
Options Vested and Expected to Vest at the end of the period (in dollars per share)	11.14
Options Exercisable at the end of the period (in dollars per share)	$ 10.86
Weighted Average Remaining Contractual Term (In Years)
Options Outstanding at the end of the period	6 years 6 months	6 years 8 months 12 days
Options Vested and Expected to Vest at the end of the period	6 years 6 months
Options Exercisable at the end of the period	5 years
Additional information
Total intrinsic value of stock options exercised (in dollars)	$ 0.1	$ 14.4	$ 2.7
Weighted average grant-date fair value (in dollars per share)	$ 3.18	$ 15.25	$ 8.82
Fair value of stock options vested (in dollars)	$ 17	$ 10	$ 5.7
Aggregate intrinsic value of stock options outstanding (in dollars)	0.4
Aggregate intrinsic value of stock options vested and expected to vest (in dollars)	0.4
Total compensation cost not yet recognized (in dollars)	$ 27.4
Weighted average period over which compensation cost is expected to be recognized as expense	2 years 9 months 18 days
2008 Plan | Restricted stock
Shares
Outstanding and unvested at the beginning of the period (in shares)	19,500
Granted (in shares)	60,000
Vested (in shares)	(19,500)
Canceled (in shares)	(10,000)
Outstanding and unvested at the end of the period (in shares)	50,000	19,500
Weighted Average Grant Date Fair Value (per share)
Outstanding and unvested at the beginning of the period (in dollars per share)	$ 25.41
Granted (in dollars per share)	4.72
Vested (in dollars per share)	25.41
Canceled (in dollars per share)	4.72
Outstanding and unvested at the end of the period (in dollars per share)	$ 4.72	$ 25.41

STOCK-BASED COMPENSATION - Valu

STOCK-BASED COMPENSATION - Valuation and Expenses Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation and Expenses Information
Total stock-based compensation expense	$ 15,317	$ 12,774	$ 6,852
Expected dividend payable in foreseeable future	$ 0
Stock options
Assumptions used for fair values of employee and director stock options granted
Expected stock price volatility, minimum (as a percent)	70.00%	67.00%	70.00%
Expected stock price volatility, maximum (as a percent)	77.00%	69.00%	72.00%
Expected option term	6 years	6 years	6 years
Risk-free interest rate, minimum (as a percent)	1.40%	1.80%	1.90%
Risk-free interest rate, maximum (as a percent)	2.30%	2.20%	2.20%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Research and development
Valuation and Expenses Information
Total stock-based compensation expense	$ 7,821	$ 6,186	$ 3,459
General and administrative
Valuation and Expenses Information
Total stock-based compensation expense	$ 7,496	$ 6,588	$ 3,393

REVENUE (Details)

REVENUE (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUE
Deferred revenue		$ 3,749	$ 4,368
Product development and licensing agreements revenue		2,174	1,442	$ 838
Contracts and grants revenue		4,612	4,038	2,748
BMS | PD-1 Immune Checkpoint Inhibitor
REVENUE
Deferred revenue	$ 5,000
Term of the agreement	5 years
Reimbursement of external costs incurred by the company (as a percent)	50.00%
Product development and licensing agreements revenue		2,100	1,300	700
Rockefeller
REVENUE
Contracts and grants revenue		$ 2,700	$ 3,400	$ 2,700

COLLABORATION AGREEMENTS (Detai

COLLABORATION AGREEMENTS (Details) - License agreements - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Collaborative Agreements
Nonrefundable license fee expense	$ 1.6	$ 0.9	$ 3.2
Medarex | Maximum
Collaborative Agreements
Period from the first commercial sale of licensed product for royalty payment	10 years
Milestone payment due	$ 7
Rockefeller | Maximum
Collaborative Agreements
Milestone payment due	3.8
Southampton | Maximum
Collaborative Agreements
Milestone payment due	1
Amgen | Maximum
Collaborative Agreements
Milestone payment due	0.9
Seattle Genetics | CuraGen | Maximum | Glembatumumab Vedotin
Collaborative Agreements
Milestone payment due	5
Seattle Genetics | CuraGen | Maximum | CDX-014
Collaborative Agreements
Milestone payment due	$ 8.5

INCOME TAXES - SUMMARY (Details

INCOME TAXES - SUMMARY (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income tax benefit (provision):
Federal									$ 45,518	$ 46,598	$ 43,536
State									7,268	10,642	7,328
Foreign									1,124
Expiration of Net Operating Losses and Research & Development Tax Credits										(155)	(2,302)
Income tax benefit (provision) before valuation allowance									53,910	57,085	48,562
Deferred tax valuation allowance									$ (53,910)	(57,085)	(48,562)
Reconciliation between the amount of reported income tax and the amount computed using U.S. Statutory rate
U.S. Statutory rate (as a percent)									34.00%
Pre-tax loss	$ (32,307)	$ (29,598)	$ (31,952)	$ (34,673)	$ (32,684)	$ (31,980)	$ (32,359)	$ (30,174)	$ (128,530)	(127,197)	(118,080)
Loss at Statutory Rates									(43,700)	(43,247)	(40,147)
Difference in Foreign Tax Rates									150
Research and Development Credits									(5,203)	(4,935)	(4,126)
State Taxes									(7,268)	(10,642)	(7,328)
Other									2,111	1,584	737
Expiration of Net Operating Losses and Research & Development Tax Credits										155	2,302
Change in Valuation Allowance									53,910	57,085	$ 48,562
Foreign pre-tax loss									3,700
Gross Deferred Tax Assets
Net Operating Loss Carryforwards	174,555				180,777				174,555	180,777
Foreign Net Operating Loss Carryforwards	1,124								1,124
Tax Credit Carryforwards	32,306				35,895				32,306	35,895
Deferred Research and Development Expenses	109,520				48,608				109,520	48,608
Stock-based Compensation	12,362				8,393				12,362	8,393
Fixed Assets	1,526				2,017				1,526	2,017
Deferred Revenue	1,418				1,703				1,418	1,703
Accrued Expenses and Other	894				219				894	219
Gross Deferred Tax Assets	333,705				277,612				333,705	277,612
Gross Deferred Tax Liabilities
Other Acquired Intangibles	(2,868)				(3,382)				(2,868)	(3,382)
IPR&D Intangibles	(28,054)				(4,661)				(28,054)	(4,661)
Gross Deferred Tax Liabilities	(30,922)				(8,043)				(30,922)	(8,043)
Total Deferred Tax Assets and Liabilities	302,783				269,569				302,783	269,569
Deferred Tax Assets Valuation Allowance	(330,837)				(274,230)				(330,837)	(274,230)
Net Deferred Tax Asset (Liability)	$ (28,054)				$ (4,661)				$ (28,054)	$ (4,661)

INCOME TAXES (Details)

INCOME TAXES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)item	Dec. 31, 2015USD ($)
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	$ 17,700
Uncertain tax position	0
Unrecognized tax benefits	$ 0	$ 0
Number of states in which the entity primarily operates or has operated and has income tax nexus | item	3
CuraGen
Net operating loss and tax credit carryforwards
Assets recorded for net operating losses not yet utilized	$ 0
Federal
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	$ 458,500
Period of recognition of unrealized loss or gain after the ownership change	5 years
Federal | R&D credit
Net operating loss and tax credit carryforwards
Tax credit carryforwards	$ 26,100
Federal | Ownership change in October 2007
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	28,300
Annual limitation	4,500
Federal | Ownership changes in June 2009 and December 2009
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	67,700
Annual limitation	6,000
Federal | Ownership Change in December 2013
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	178,700
Annual limitation	77,000
Federal | Prior to merger
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	33,000
Federal | AVANT
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	356,700
Federal | AVANT | Prior to merger
Net operating loss and tax credit carryforwards
NOL, net of expirations and utilization	101,200
Federal | CuraGen | Prior to acquisition
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	518,300
Federal | Kolltan | Prior to acquisition
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	110,500
State
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	344,900
State | R&D credit
Net operating loss and tax credit carryforwards
Tax credit carryforwards	9,400
Foreign
Net operating loss and tax credit carryforwards
Net operating loss carryforwards	$ 3,700

COMMITMENTS AND CONTINGENCIES60

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Obligations for base rent and CAM costs under facility and other non-cancelable operating leases
2,017	$ 4,319
2,018	4,782
2,019	4,381
2,020	2,348
Total minimum lease payments	15,830
Total rent and CAM expense	$ 4,800	$ 2,900	$ 2,700

RETIREMENT SAVINGS PLAN (Detail

RETIREMENT SAVINGS PLAN (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
RETIREMENT SAVINGS PLAN
Maximum contribution by participants (as a percent)	60.00%
Employer matching contributions (as a percent)	50.00%
Maximum percentage of employees' gross pay subject to employer matching contributions	4.00%
Benefit expense for the 401(k) Plan	$ 0.4	$ 0.4	$ 0.3

KOLLTAN ACQUISITION - Purchase

KOLLTAN ACQUISITION - Purchase Price (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 29, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Acquisition-date fair value of consideration transferred
Fair value of contingent consideration		$ 44,200	$ 44,200	$ 44,200
Kolltan
KOLLTAN ACQUISITION
Shares issued as part of consideration (in shares)	18,257,996
Shares issuable in lieu of cash severance obligations (in shares)	437,901
Shares issued in lieu of cash severance obligations (in shares)			111,111
Maximum amount of milestone payments	$ 172,500
Closing price of common stock (in dollars per share)	$ 4.02
Acquisition-date fair value of consideration transferred
Fair value of common stock issued for upfront payment	$ 73,397
Fair value of contingent consideration	44,200
Kolltan transaction expenses paid in cash by the Company	3,768	700		700
Total consideration transferred	121,365
Contingent consideration, noncurrent	$ 44,200	44,200	$ 44,200	$ 44,200
Range of estimated milestone payment, minimum		0
Range of estimated milestone payment, maximum		$ 172,500
Level 3 | Kolltan | Minimum
Acquisition-date fair value of consideration transferred
Discount rate (as a percent)	10.00%
Level 3 | Kolltan | Maximum
Acquisition-date fair value of consideration transferred
Discount rate (as a percent)	11.00%

KOLLTAN ACQUISITION - Allocatio

KOLLTAN ACQUISITION - Allocations of Assets and Liabilities (Details) - USD ($) $ in Thousands	Nov. 29, 2016	Dec. 31, 2016	Dec. 31, 2015
Summary of fair values of assets acquired and liabilities assumed at acquisition date
Goodwill		$ 90,976	$ 8,965
Kolltan
KOLLTAN ACQUISITION
Goodwill expected to be deductible for income tax purposes	$ 0
Summary of fair values of assets acquired and liabilities assumed at acquisition date
Cash and cash equivalents	8,160
Other current and long-term assets	799
Property and Equipment, Net	2,072
In-process research and development (IPR&D)	61,690
Goodwill	82,011
Deferred tax liabilities, net	(23,393)
Other assumed liabilities	(9,974)
Total	$ 121,365
Maximum period for adjustments to purchase price allocation from acquisition date (in years)	1 year
Kolltan | CDX-0158
Summary of fair values of assets acquired and liabilities assumed at acquisition date
In-process research and development (IPR&D)	$ 40,000
Kolltan | CDX-3379
Summary of fair values of assets acquired and liabilities assumed at acquisition date
In-process research and development (IPR&D)	3,500
Kolltan | TAM programs
Summary of fair values of assets acquired and liabilities assumed at acquisition date
In-process research and development (IPR&D)	$ 18,000
Kolltan | CDX- 0158 CDX-3379 and TAM
Summary of fair values of assets acquired and liabilities assumed at acquisition date
Estimated development costs included in expected future net cash flows		$ 132,000

KOLLTAN ACQUISITION - Acquisiti

KOLLTAN ACQUISITION - Acquisition Related Expenses, Including Severance and Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 29, 2016	Dec. 31, 2016	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
KOLLTAN ACQUISITION
Revenues			$ 1,874	$ 2,220	$ 1,389	$ 1,303	$ 1,790	$ 1,026	$ 2,178	$ 486	$ 6,786	$ 5,480	$ 3,586
Kolltan
KOLLTAN ACQUISITION
Acquisition-related expenses	$ 3,768	$ 700									700
Severance expenses		3,100
Revenues		$ 0
Pro Forma Financial Information
Revenue											6,786	5,480
Net loss											$ (146,905)	$ (157,690)
Basic and Diluted Net Loss Per Common Share											$ (1.24)	$ (1.37)
Kolltan | General and administrative
KOLLTAN ACQUISITION
Severance expenses											$ 2,400
Kolltan | Research and development
KOLLTAN ACQUISITION
Severance expenses											$ 700

RESTRUCTURING EXPENSE (Details)

RESTRUCTURING EXPENSE (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)ft²	Dec. 31, 2016USD ($)ft²
Restructuring Cost and Reserve [Line Items]
Restructuring, Accrual	$ 1,154	$ 1,154
Needham Expansion
Restructuring Cost and Reserve [Line Items]
Expansion space (in square feet) | ft²	11,500	11,500
Restructuring, Charges		$ 1,154
Restructuring, Accrual	$ 1,154	1,154
Short-term portion of lease accrual	378	378
Long-term portion of lease accrual	$ 776	$ 776
Credit-adjusted risk-free rate (as a percent)	10.00%

SELECTED QUARTERLY FINANCIAL 66

SELECTED QUARTERLY FINANCIAL DATA (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SELECTED QUARTERLY FINANCIAL DATA (Unaudited)
Total revenue	$ 1,874	$ 2,220	$ 1,389	$ 1,303	$ 1,790	$ 1,026	$ 2,178	$ 486	$ 6,786	$ 5,480	$ 3,586
Net loss	$ (32,307)	$ (29,598)	$ (31,952)	$ (34,673)	$ (32,684)	$ (31,980)	$ (32,359)	$ (30,174)	$ (128,530)	$ (127,197)	$ (118,080)
Basic and diluted net loss per common share (in dollars per share)	$ (0.30)	$ (0.29)	$ (0.32)	$ (0.35)	$ (0.33)	$ (0.32)	$ (0.33)	$ (0.33)	$ (1.27)	$ (1.31)	$ (1.32)