Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Nov. 07, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	MACK
Entity Registrant Name	MERRIMACK PHARMACEUTICALS INC
Entity Central Index Key	0001274792
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		13,332,967

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 107,245	$ 21,524
Restricted cash	102	102
Accounts receivable, net	190	275
Prepaid expenses and other current assets	8,040	2,239
Assets held for sale		33,295
Total current assets	115,577	57,435
Restricted cash	60,682	674
Property and equipment, net	10,188	14,212
Equity method investment	11,400
Other assets		27
Assets held for sale, net of current portion		9,135
Total assets	197,847	81,483
Current liabilities:
Accounts payable, accrued expenses and other	23,983	29,369
Deferred rent	2,117	2,014
Accrued intraperiod tax allocation	6,613
Income taxes payable	1,844
Liabilities held for sale		56,839
Total current liabilities	34,557	88,222
Deferred rent, net of current portion	1,772	3,386
Long-term debt	49,884	216,861
Liabilities held for sale, net of current portion		25,673
Total liabilities	86,213	334,142
Commitments and contingencies (Note 10)
Non-controlling interest		(1,539)
Stockholders’ equity/(deficit):
Preferred stock, $0.01 par value: 10,000 shares authorized at September 30, 2017 and December 31, 2016; no shares issued or outstanding at September 30, 2017 or December 31, 2016
Common stock, $0.01 par value: 20,000 shares authorized at September 30, 2017 and December 31, 2016; 13,274 and 13,020 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	1,328	1,302
Additional paid-in capital	580,126	702,377
Accumulated (deficit)	(469,820)	(954,799)
Total stockholders’ equity/(deficit)	111,634	(251,120)
Total liabilities, non-controlling interest and stockholders’ equity/(deficit)	$ 197,847	$ 81,483

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	20,000,000	20,000,000
Common stock, shares issued	13,274,000	13,020,000
Common stock, shares outstanding	13,274,000	13,020,000

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Costs and expenses:
Research and development expenses	$ 13,598	$ 28,247	$ 54,954	$ 83,944
General and administrative expenses	3,366	6,448	23,798	21,038
Restructuring expenses		809		809
Total costs and expenses	16,964	35,504	78,752	105,791
Loss from continuing operations	(16,964)	(35,504)	(78,752)	(105,791)
Other income and expenses:
Interest income	250	64	646	258
Interest expense	(1,659)	(1,560)	(30,400)	(20,708)
Gain on deconsolidation of Silver Creek Pharmaceuticals, Inc.	10,848		10,848
Gain on sale of asset			1,703
Other income (expense), net	69	385	(592)	278
Net loss from continuing operations before income tax benefit	(7,456)	(36,615)	(96,547)	(125,963)
Income tax benefit	2,133	9,770	32,372	9,770
Net loss from continuing operations	(5,323)	(26,845)	(64,175)	(116,193)
Discontinued operations:
Income (loss) from discontinued operations, net of tax	8,456	(3,430)	547,994	(3,698)
Net income (loss)	3,133	(30,275)	483,819	(119,891)
Net income (loss) attributable to non-controlling interest	31	(207)	(1,160)	(600)
Net income (loss) attributable to Merrimack Pharmaceuticals, Inc.	3,102	(30,068)	484,979	(119,291)
Other comprehensive income (loss):
Unrealized loss on available-for-sale securities		(3)		(2)
Other comprehensive loss		(3)		(2)
Comprehensive income (loss)	3,102	(30,071)	484,979	(119,293)
Amounts attributable to Merrimack Pharmaceuticals, Inc.:
Net loss from continuing operations	(5,354)	(26,638)	(63,015)	(115,593)
Income (loss) from discontinued operations, net of tax	8,456	(3,430)	547,994	(3,698)
Net income (loss) attributable to Merrimack Pharmaceuticals, Inc.	$ 3,102	$ (30,068)	$ 484,979	$ (119,291)
Basic and dilutive net income (loss) per common share
Net loss from continuing operations	$ (0.40)	$ (2.06)	$ (4.77)	$ (9.33)
Net income (loss) from discontinued operations, net of tax	0.64	(0.27)	41.52	(0.30)
Net income (loss) per share	$ 0.24	$ (2.33)	$ 36.75	$ (9.63)
Weighted-average common shares used per share calculations—basic and diluted	13,282	12,921	13,197	12,383
Cash dividend paid per common share			$ 10.55

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income (loss)	$ 483,819	$ (119,891)
Income (loss) from discontinued operations	547,994	(3,698)
Loss from continuing operations	(64,175)	(116,193)
Adjustments to reconcile net loss to net cash used in operating activities
Non-cash interest expense	3,352	4,672
Loss on extinguishment of debt	4,887	14,566
Benefit from intraperiod tax allocation	(32,372)	(9,970)
Depreciation and amortization expense	2,813	4,181
Non-cash activity related to discontinued operations	10,241	9,970
Gain on deconsolidation of Silver Creek Pharmaceuticals, Inc.	(10,848)
Loss (gain) on sale of property and equipment	(439)	187
Stock-based compensation expense	11,110	8,251
Changes in operating assets and liabilities:
Accounts receivable	85	11
Prepaid expenses and other current assets	(6,205)	1,087
Income taxes payable	1,844
Accounts payable, accrued expenses and other	(3,140)	(4,061)
Deferred rent	(334)	493
Net cash used in continuing operations for operating activities	(83,181)	(86,806)
Net cash used in discontinuing operations for operating activities	(37,964)	(52,538)
Net cash used in operating activities	(121,145)	(139,344)
Cash flows from investing activities
Purchase of property and equipment	(729)	(2,868)
Proceeds from maturities and sales of available for sale securities		72,160
Proceeds on sale of property and equipment	1,094
Purchases of available for sale securities		(84,262)
Proceeds from sale of business	575,000
Changes in restricted cash	(60,008)
Net cash provided by (used in) investing activities	511,355	(14,970)
Cash flows from financing activities
Proceeds from exercise of options to purchase common stock	6,517	4,007
Repayment of debt	(175,000)
Payment of dividend	(140,000)
Other financing activities, net		(21)
Net cash provided by (used in) financing activities	(304,489)	5,171
Net increase (decrease) in cash and cash equivalents	85,721	(149,143)
Cash and cash equivalents, beginning of period	21,524	185,606
Cash and cash equivalents, end of period	107,245	36,463
Non-cash investing and financing activities
Purchases of property and equipment in accounts payable, accrued expenses and other	159	105
Receivables related to stock option exercises in prepaid expenses and other current assets		39
Receivables related to property and equipment sale in other current assets	145	40
Transaction costs related to conversion of convertible notes due 2020 in accounts payable, accrued expenses and other		148
Principal amount of convertible notes due 2020 converted into shares of common stock		64,209
Supplemental disclosure of cash flows
Cash paid for income taxes	6,122
Cash paid for interest	30,250	13,851
Silver Creek Pharmaceuticals Inc [Member]
Adjustments to reconcile net loss to net cash used in operating activities
Gain on deconsolidation of Silver Creek Pharmaceuticals, Inc.	(10,848)
Cash flows from investing activities
Deconsolidation of Silver Creek Pharmaceuticals, Inc. cash	(4,002)
Cash flows from financing activities
Proceeds from issuance of Series C preferred stock by Silver Creek Pharmaceuticals, Inc., net of issuance costs	$ 3,994	$ 1,185

Nature of the Business

9 Months Ended

Sep. 30, 2017

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of the Business

1. Nature of the Business

Merrimack Pharmaceuticals, Inc. (the “Company”) is a biopharmaceutical company based in Cambridge, Massachusetts that is outthinking cancer to ensure that patients and their families live fulfilling lives. The Company’s mission is to transform cancer care through the smart design and development of targeted solutions based on a deep understanding of cancer pathways and biological markers. All of the Company’s development programs, including four clinical studies in distinct indications and six candidates in preclinical development, fit into the Company’s strategy of (1) understanding the biological problems the Company is trying to solve, (2) designing specific solutions and (3) developing those solutions for biomarker-selected patients. This three-pronged strategy seeks to ensure optimal patient outcomes.

On April 3, 2017, the Company completed the previously announced transaction (the “Asset Sale”) with Ipsen S.A. (“Ipsen”). Pursuant to the Asset Purchase and Sale Agreement, dated as of January 7, 2017 (the “Asset Sale Agreement”), between the Company and Ipsen, the Company sold to Ipsen its right, title and interest in the non-cash assets, equipment, inventory, contracts and intellectual property primarily related to or used in the Company’s business operations and activities involving or relating to developing, manufacturing and commercializing ONIVYDE, the Company’s first commercial product, and MM-436 (the “Commercial Business”). The Company received $575.0 million in cash, subject to a working capital adjustment, and is eligible to receive up to $450.0 million in additional regulatory approval-based milestone payments. The Company reached a settlement on certain working capital adjustments with Ipsen in the amount of $0.8 million, which was received in September 2017. The remaining working capital adjustment is currently estimated as a $4.9 million receivable presented in prepaid expenses and other currents assets within the condensed consolidated balance sheets, which was received in the fourth quarter of 2017. The Company also retained the right to receive net milestone payments of up to $33.0 million that may become payable pursuant to the license and collaboration agreement with Baxalta Incorporated, Baxalta US Inc. and Baxalta GmbH (collectively, “Baxalta”) for the ex-U.S. development and commercialization of ONIVYDE.

The Company’s non-commercial assets, including its clinical and preclinical development programs, were not included in the Asset Sale and remain assets of the Company. The Company’s most advanced assets are as follows:

•

MM-121 (seribantumab), a fully human monoclonal antibody that binds to the ErbB3 (HER3) receptor and targets heregulin positive cancers. There are two active development programs for MM-121, each in a Phase 2 clinical trial. The Company is currently conducting the Phase 2 randomized SHERLOC clinical trial, evaluating MM-121 in heregulin positive non-small cell lung cancer patients in combination with docetaxel. The Company has also initiated trial sites for the Phase 2 randomized SHERBOC clinical trial in patients with heregulin positive, hormone receptor positive, ErbB2 (HER2) negative, metastatic breast cancer in combination with fulvestrant, and expects to dose the first patient in the SHERBOC clinical trial in the fourth quarter of 2017;

•

MM-141 (istiratumab), a fully human bispecific tetravalent monoclonal antibody designed to block tumor survival signals by targeting receptor complexes containing the insulin-like growth factor 1 (“IGF-1”) receptor and ErbB3 (HER3) cell surface receptors. The Company is currently conducting and has completed enrollment of the Phase 2 randomized CARRIE clinical trial evaluating MM-141 in previously untreated metastatic pancreatic cancer patients with high levels of free IGF-1 in combination with nab-paclitaxel and gemcitabine; and

•

MM-310, an antibody-directed nanotherapeutic (“ADN”) that contains a novel prodrug of the highly potent chemotherapy docetaxel and targets the ephrin receptor A2 (“EphA2”) receptor, which is highly expressed in most solid tumor types. MM-310 was designed to improve the therapeutic window of docetaxel in major oncology indications, such as prostate, ovarian, bladder, gastric, pancreatic and lung cancers. The Company initiated a Phase 1 clinical trial to evaluate safety and preliminary activity of MM-310 in the first quarter of 2017.

The Company is subject to risks and uncertainties common to companies in the biopharmaceutical industry, including, among other things, its ability to secure additional capital to fund operations, success of clinical trials, development by competitors of new technological innovations, dependence on collaborative arrangements, protection of proprietary technology, compliance with government regulations and dependence on key personnel. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of capital, adequate personnel, infrastructure and extensive compliance reporting capabilities.

The accompanying condensed consolidated financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business. Until such time, if ever, as the Company can generate sufficient product revenues, the Company expects to finance its cash needs through a combination of equity offerings, debt financings, collaborations, licensing arrangements and other marketing and distribution arrangements. The Company could also engage in discussions with third parties regarding partnerships, joint ventures, combinations or divestitures of one or more of its businesses as it seeks to further the development of its research programs, improve its cash position and maximize stockholder value.

Basis of Presentation and Consolidation	9 Months Ended
Basis of Presentation and Consolidation	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and Consolidation	2. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of September 30, 2017 and December 31, 2016, and for the three and nine months ended September 30, 2017 and 2016, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all adjustments which are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 filed with the SEC on March 1, 2017. The information presented in the condensed consolidated financial statements and related notes as of September 30, 2017, and for the three and nine months ended September 30, 2017 and 2016, is unaudited. The December 31, 2016 condensed consolidated balance sheets included herein were derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the three and nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2017, or any future period. As of March 31, 2017, the Commercial Business met all the conditions to be classified as a discontinued operation since the disposal of the Commercial Business represented a strategic shift that will have a major effect on the Company’s operations and financial results. The Company will not have further significant involvement in the operations of the discontinued Commercial Business. The operating results of the Commercial Business are reported as a loss from discontinued operations, net of tax in the condensed consolidated statements of operations and comprehensive income (loss) for all periods presented. The gain recognized on the sale of the Commercial Business is presented in income (loss) from discontinued operations, net of tax in the consolidated statement of operations and comprehensive income (loss). In addition, in the condensed consolidated balance sheets as of December 31, 2016, the assets and liabilities held for sale have been presented separately. For additional information, see Note 3, “Sale of Commercial Business.” The condensed consolidated financial statements have historically included the accounts of the Company and Silver Creek Pharmaceuticals, Inc. (“Silver Creek”) with all intercompany transactions and balances eliminated in consolidation. Silver Creek represented a variable interest entity that the Company consolidated as the primary beneficiary. As discussed in Note 12, “Investment in Silver Creek,” Silver Creek completed a preferred stock financing in the third quarter of 2017, which reduced the Company’s ownership percentage in Silver Creek below 50% and resulted in the Company no longer controlling the Silver Creek board of directors. The Company determined that it is no longer the primary beneficiary of Silver Creek since the Company does not control the board of directors and does not direct the activities that have the most significant impact on Silver Creek’s economic performance. Therefore, the Company deconsolidated Silver Creek from its financial statements in the third quarter of 2017 in accordance with Accounting Standards Codification (“ASC”) 810-10-40-4(c), Consolidation. The Company accounts for its investment in Silver Creek under the equity method of accounting as of September 30, 2017. The Company’s consolidated balance sheet at December 31, 2016, as reported, included Silver Creek’s assets and liabilities, after intercompany eliminations. The Company’s unaudited consolidated balance sheet at September 30, 2017 does not include the assets and liabilities of Silver Creek since the Company deconsolidated Silver Creek in the third quarter of 2017. The Company’s unaudited consolidated statements of operations for the nine months ended September 30, 2017 include Silver Creek’s results for the period through July 13, 2017, the day immediately preceding the deconsolidation of Silver Creek. For the three and nine months ended September 30, 2016, the Company’s unaudited consolidated results include Silver Creek’s results for the full periods presented. On August 11, 2017, the Company’s stockholders approved an amendment to the Company's certificate of incorporation to effect a one-for-ten reverse stock split of its issued and outstanding common stock (the “Reverse Split”). On September 5, 2017, the Company filed the amendment to its certificate of incorporation to effect the Reverse Split, and on September 6, 2017, the Reverse Split was effective for trading purposes. As a result of the Reverse Split, every ten shares of common stock issued and outstanding was converted into one share of common stock, reducing the number of issued and outstanding shares of common stock from approximately 132.8 million shares to approximately 13.28 million shares. No fractional shares were issued in connection with the Reverse Split. The amendment to the certificate of incorporation also proportionately reduced the number of authorized shares of common stock from 200 million to 20 million. The Reverse Split did not change the par value of the common stock. The Reverse Split did not change the number of authorized shares or par value of the Company’s preferred stock, of which there are no shares issued or outstanding. All outstanding stock options and convertible notes entitling their holders to purchase shares of common stock or acquire shares of common stock upon conversion, as the case may be, were adjusted as a result of the Reverse Split, as required by the terms of these securities. For additional information, see Note 11, “Stock Compensation.”

Sale of Commercial Business

9 Months Ended

Sep. 30, 2017

Discontinued Operations And Disposal Groups [Abstract]

Sale of Commercial Business

3. Sale of Commercial Business

Ipsen

On April 3, 2017, the Company completed the sale of the Commercial Business to Ipsen. Pursuant to the Asset Sale Agreement, the Company may be entitled to up to $450.0 million in additional payments based on the achievement by or on behalf of Ipsen of certain milestone events if the U.S. Food and Drug Administration (the “FDA”) approves ONIVYDE for certain indications as follows: (i) $225.0 million upon the regulatory approval by the FDA of ONIVYDE for the first-line treatment of metastatic adenocarcinoma of the pancreas (a) in combination with fluorouracil and leucovorin (with or without oxaliplatin), (b) in combination with gemcitabine and abraxane or (c) following submission and filing of regulatory approval by Ipsen for purposes of commercialization by Ipsen; (ii) $150.0 million upon the regulatory approval by the FDA of ONIVYDE for the treatment of small cell lung cancer after failure of first-line chemotherapy; and (iii) $75.0 million upon the regulatory approval by the FDA of ONIVYDE for an additional indication unrelated to those described above.

In connection with the sale of the Commercial Business, on April 3, 2017, the Company entered into a transition services agreement with Ipsen pursuant to which the Company and Ipsen are providing certain services to each other for a period of 24 months following the closing, including Ipsen’s agreement to manufacture MM-310 and to perform certain quality related services in accordance with a manufacturing services agreement, the accounting impact of which is immaterial.

In connection with the completion of the Asset Sale, on April 3, 2017, the Company irrevocably deposited the redemption price of the 11.50% senior secured notes due 2022 (the “2022 Notes”) of $175.0 million outstanding aggregate principal amount, interest of $7.4 million through the redemption date and an additional make-whole premium payment of approximately $20.1 million with U.S. Bank National Association as trustee (the “Trustee”) under the Indenture dated as of December 22, 2015 (the “Indenture”) and irrevocably instructed the Trustee to apply such amount to the redemption in full of the 2022 Notes on the redemption date of April 27, 2017. The Indenture was satisfied and discharged on April 3, 2017.

In connection with the completion of the Asset Sale, on April 3, 2017, the Company entered into a sublease with Ipsen, pursuant to which Ipsen is subleasing from the Company approximately 70,237 square feet of leased space in the Company’s Cambridge, Massachusetts facility through the end of the term of the lease on June 30, 2019. Payments under the sublease are recorded as an offset to rent expense in the condensed consolidated statement of operations and comprehensive income (loss).

Also in connection with the completion of the Asset Sale, on April 3, 2017, the Company entered into an intellectual property license agreement with Ipsen, pursuant to which Ipsen granted to the Company a perpetual, worldwide, non-exclusive, royalty-free, fully paid-up license in and to all patents included in the transferred intellectual property, other than certain patents relating to generic liposomal technology, with respect to which the license will be exclusive, in each case for use outside of the Commercial Business. The Company granted to Ipsen a non-exclusive, royalty-free, fully paid up, perpetual, irrevocable and worldwide license to all patents it owned at the time of the closing of the transaction contemplated by the Asset Sale Agreement for use in connection with the Commercial Business. This transfer of intellectual property did not impact the financial statements as no amounts related to the intellectual property had previously been recorded.

On April 5, 2017, the Company announced that its Board of Directors authorized and declared a special cash dividend of $140.0 million on the Company's common stock. The special dividend was payable on May 26, 2017 to stockholders of record as of the close of business on May 17, 2017. The special dividend resulted in a decrease to additional paid-in capital.

Discontinued Operations and Assets Held for Sale

The condensed consolidated financial statements for the three and nine months ended September 30, 2017 and 2016 reflect the operations of the Commercial Business as a discontinued operation. For the three months ended September 30, 2017, the Company recorded a gain of $3.5 million on the Asset Sale, resulting from an increase in the estimated working capital adjustment. The Company reached a settlement on certain working capital adjustments with Ipsen in the amount of $0.8 million, which was received in September 2017. The remaining working capital adjustment is currently estimated as a $4.9 million receivable that was received in the fourth quarter of 2017. For the nine months ended September 30, 2017, the Company recorded a gain of approximately $601.7 million on the Asset Sale, which is included in gain from discontinued operations on the condensed consolidated statements of operations and comprehensive income (loss). Discontinued operations for the three and nine months ended September 30, 2017 and 2016 includes the following:

(in thousands)	Three Months Ended September 30,					Nine Months Ended September 30,
	2017		2016			2017			2016
Revenues:
Product revenues, net	$	—	$	14,493		$	16,135		$	37,312
License and collaboration revenues		—		12,417			7,797			43,062
Other revenues		—		1,161			1,973			2,659
Total revenues		—		28,071			25,905			83,033
Costs and expenses:
Cost of revenues		—		1,010			3,890			3,593
Research and development expenses		—		3,830			3,730			22,012
Selling, general and administrative expenses		—		11,600			8,732			35,485
Restructuring expenses		—		—			9,535			—
Total costs and expenses		—		16,440			25,887			61,090
Other income and expenses:
Interest expense		—		(5,291	)		(6,743	)		(15,871	)
Gain on sale of commercial business		3,497		—			601,670			—
Income from discontinued operations	$	3,497	$	6,340		$	594,945		$	6,072
Income tax benefit (expense)		4,959		(9,770	)		(46,951	)		(9,770	)
Total income (loss) from discontinued operations	$	8,456	$	(3,430	)	$	547,994		$	(3,698	)

The carrying value of the assets and liabilities of the Commercial Business classified as “Discontinued operations” in the condensed consolidated balance sheets is as follows:

(in thousands)	December 31, 2016
Assets
Current assets:
Accounts receivable, net	$	17,194
Inventory		14,554
Prepaid expenses and other current assets		1,547
Total current assets held for sale		33,295
Property and equipment, net		1,553
Intangible assets, net		3,977
Goodwill		3,605
Total long-term assets held for sale		9,135
Liabilities
Current liabilities:
Accounts payable, accrued expenses and other		20,613
Deferred revenues		36,226
Total current liabilities held for sale		56,839
Deferred revenues, net of current portion		25,673
Total liabilities held for sale		25,673

Inventory

Inventory of the Commercial Business as of December 31, 2016 consisted of the following:

(in thousands)	December 31, 2016
Raw materials	$	4,483
Work in process		8,651
Finished goods		1,420
Total inventory	$	14,554

Restructuring Activities

On January 8, 2017, the Company announced a reduction in headcount by approximately 30% in connection with the Asset Sale and the completion of its strategic pipeline review. Upon the closing of the Asset Sale and the completion of its strategic pipeline review, the Company had approximately 80 employees.

Under this corporate restructuring, for the three and nine months ended September 30, 2017, the Company recognized total restructuring expenses of $0.0 million and $9.5 million, respectively, which was related to contractual termination benefits for employees with pre-existing severance arrangements. These one-time employee termination benefits are comprised of severance, benefits and related costs, all of which are expected to result in cash expenditures. The majority of these payments were made during the second quarter of 2017. The remaining payments represent severance payments that will be paid over one year. The expense of $9.5 million was included in discontinued operations, as the costs are directly associated with the sale of the Commercial Business.

The following table summarizes the charges related to the restructuring activities as of September 30, 2017:

(in thousands)	Accrued Restructuring Expenses at December 31, 2016		Expenses		Less: Payments		Accrued Restructuring Expenses at September 30, 2017
Severance, benefits and related costs	$	—	$	9,521	$	8,434	$	1,087
Totals	$	—	$	9,521	$	8,434	$	1,087

These amounts are included in accounts payable, accrued expenses and other in the September 30, 2017 balance sheet.

License and Collaboration Agreements Related to the Asset Sale

Baxalta

On September 23, 2014, the Company and Baxter International Inc., Baxter Healthcare Corporation and Baxter Healthcare SA entered into a license and collaboration agreement (the “Baxalta Agreement”) for the development and commercialization of ONIVYDE outside of the United States and Taiwan (the “Licensed Territory”). In connection with Baxter International Inc.’s separation of the Baxalta business, the Baxalta Agreement was assigned to Baxalta during the second quarter of 2015. As part of the Baxalta Agreement, the Company granted Baxalta an exclusive, royalty-bearing right and license under the Company’s patent rights and know-how to develop and commercialize ONIVYDE in the Licensed Territory.

On April 3, 2017, the Baxalta Agreement and all related agreements, including the Company’s agreement related to the commercial supply of ONIVYDE, were assigned to Ipsen in connection with the Asset Sale. Pursuant to the Asset Sale Agreement, the Company retained the right to receive net milestone payments of up to $33.0 million that may become payable pursuant to the Baxalta Agreement for the ex-U.S. development and commercialization of ONIVYDE, which is comprised of potential payments of $18.0 million from the sale of ONIVYDE in two additional major European countries, $5.0 million related to the sale of ONIVYDE in the first major non-European, non-Asian country and $10.0 million for the first patient dosed in a pivotal clinical trial in an indication other than pancreatic cancer.

PharmaEngine, Inc.

On May 5, 2011, the Company and PharmaEngine, Inc. (“PharmaEngine”) entered into an assignment, sublicense and collaboration agreement (the “PharmaEngine Agreement”) under which the Company reacquired rights in Europe and certain countries in Asia to ONIVYDE. In exchange, the Company agreed to pay PharmaEngine a nonrefundable, noncreditable upfront payment of $10.0 million and up to an additional $80.0 million in aggregate development and regulatory milestones and $130.0 million in aggregate sales milestones.

On April 3, 2017, the PharmaEngine Agreement and all related agreements, including the Company’s agreement related to its commercial supply of ONIVYDE, were assigned to Ipsen in connection with the Asset Sale.

Going Concern	9 Months Ended
Going Concern	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Going Concern	4. Going Concern In accordance with ASC 205-40, Going Concern, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. As of December 31, 2016, the Company had $21.5 million in unrestricted cash and cash equivalents, had suffered recurring losses from operations and had negative working capital and cash outflows from operating activities. Based on the evaluation completed in connection with the filing of the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, including consideration of management’s plans, the Company previously concluded that there was substantial doubt as to its ability to continue as a going concern within one year after March 1, 2017, the date that the consolidated financial statements were issued. On April 3, 2017, the Company closed the Asset Sale with Ipsen and received a $575.0 million upfront cash payment, subject to a working capital adjustment. The Company reached a settlement on certain working capital adjustments with Ipsen in the amount of $0.8 million, which was received in September 2017. The remaining working capital adjustment is currently estimated as a $4.9 million receivable that was received in the fourth quarter of 2017. The Company used a portion of the cash payment to redeem the $175.0 million outstanding aggregate principal amount of the 2022 Notes, which also required an additional make-whole premium payment of approximately $20.1 million, and deposited $60.0 million into an escrow account in response to a lawsuit filed by the trustee and certain holders of its 4.50% convertible notes due 2020 (the “Convertible Notes”). The Company distributed $140.0 million of the upfront cash payment in the form of a special cash dividend to stockholders, which was payable on May 26, 2017 to stockholders of record as of the close of business on May 17, 2017. After consideration of the Company’s cash and cash equivalents balance at March 31, 2017 of $17.2 million and the net proceeds from the Asset Sale, the Company has concluded that the previous conditions and events that raised substantial doubt about its ability to continue as a going concern have been alleviated. The Company updated its going concern assessment for the three months ended September 30, 2017 and concluded the Company is able to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	5. Income Taxes Deferred tax assets and liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using future enacted tax 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 Company completed the Asset Sale and recorded the income tax implications of the sale in the second quarter of 2017. The Asset Sale generated taxable income for the Company which has resulted in income tax expense. The Company released a portion of its valuation allowance in the three months ended June 30, 2017 as it is now able to utilize its net operating loss carryforwards to offset the taxable income generated from the Asset Sale. The Company’s current income tax expense for the nine months ended September 30, 2017 is $8.0 million, which is comprised primarily of federal Alternative Minimum Tax and state income tax. As of September 30, 2017, the income tax payable was $1.8 million. Intraperiod tax allocation rules require the Company to allocate the provision for income taxes between continuing operations and other categories of earnings, such as discontinued operations. In periods in which there is pre-tax loss from continuing operations and pre-tax income in other categories of earnings, such as discontinued operations, the Company must allocate to continuing operations a tax benefit for the loss in continuing operations with an offsetting tax expense to discontinued operations. For the three and nine months ended September 30, 2017, the Company recognized an income tax benefit of $2.1 million and $32.4 million, respectively, in continuing operations and income tax benefit in discontinued operations of $5.0 million and income tax expense of $47.0 million, respectively, related to the income generated in connection with the Asset Sale. For the three and nine months ended September 30, 2016, the Company recognized an income tax benefit of $9.8 million in continuing operations and income tax expense in discontinued operations of $9.8 million. In connection with the Asset Sale, the Company recorded an income tax provision in discontinued operations of $224.3 million prior to the release of the valuation allowance. The Company released $177.4 million of its valuation allowance in discontinued operations, resulting in a total income tax expense of $47.0 million in discontinued operations for the nine months ended September 30, 2017.

Net Income (Loss) Per Common Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Net Income (Loss) Per Common Share

6. Net Income (Loss) Per Common Share

Basic net income (loss) per share is calculated by dividing the net income (loss) attributable to Merrimack Pharmaceuticals, Inc. by the weighted-average number of common shares outstanding during the period.

Diluted net income (loss) per share is computed by dividing the net income (loss) attributable to Merrimack Pharmaceuticals, Inc. by the weighted-average number of dilutive common shares outstanding during the period. Dilutive shares outstanding is calculated by adding to the weighted shares outstanding any potential (unissued) shares of common stock from outstanding stock options based on the treasury stock method. In a period when a net loss is reported, all common stock equivalents are excluded from the calculation because they would have an anti-dilutive effect, meaning the loss per share would be reduced. Therefore, in periods where a loss is reported, there is no difference in basic and dilutive loss per share.

The Company follows the two-class method when computing net income (loss) per share, when it has issued shares that meet the definition participating securities. The two–class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participating rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based on their respective rights to receive dividends, as if all income for the period has been distributed or losses to be allocated if they are contractually required to fund losses. There were no amounts allocated to participating securities for the three and nine months ended September 30, 2017 and 2016, as the Company was in a loss position and had no shares that met the definition of participating securities outstanding as of September 30, 2017 and 2016.

In addition, as discussed in Note 10, “Borrowings,” in July 2013, the Company issued $125.0 million aggregate principal amount of Convertible Notes in an underwritten public offering. Following the repayment and satisfaction in full of the Company’s obligations to Hercules Technology Growth Capital, Inc. (“Hercules”) under its Loan and Security Agreement with Hercules (the “Loan Agreement”), which occurred in December 2015, upon any conversion of the Convertible Notes, the Convertible Notes may be settled, at the Company’s election, in cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock. For purposes of calculating the maximum dilutive impact, it is presumed that the conversion premium will be settled in common stock, inclusive of a contractual make-whole provision resulting from a fundamental change, and the resulting potential common shares included in diluted earnings per share if the effect is more dilutive. As of September 30, 2017, $60.8 million aggregate principal amount of the Convertible Notes remained outstanding.

The stock options and conversion premium on the Convertible Notes are excluded from the calculation of diluted loss per share because the net loss for the three and nine months ended September 30, 2016 causes such securities to be anti-dilutive. Outstanding securities excluded from the calculation of diluted loss per share for the three and nine months ended September 30, 2017 and 2016 are shown in the chart below:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2017		2016		2017		2016
Outstanding options to purchase common stock		1,824		2,100		1,824		2,100
Conversion of the Convertible Notes		1,216		1,216		1,216		1,216

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

7. Fair Value of Financial Instruments

Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value.

Recurring Fair Value Measurements

The carrying values of cash, restricted cash, prepaid expenses, accounts receivable, accounts payable and accrued expenses, and other short-term assets and liabilities approximate their respective fair values due to the short-term maturities of these assets and liabilities.

The following tables show assets measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016:

	September 30, 2017
(in thousands)	Level 1		Level 2		Level 3
Assets:
Money market funds	$	99,079	$	—	$	—
Totals	$	99,079	$	—	$	—

	December 31, 2016
(in thousands)	Level 1		Level 2		Level 3
Assets:
Money market funds	$	12,373	$	—	$	—
Totals	$	12,373	$	—	$	—

Liabilities:
Silver Creek warrant liability	$	—	$	—	$	1,499
Totals	$	—	$	—	$	1,499

In December 2016, Silver Creek issued warrants to purchase an aggregate of 1.9 million shares of Silver Creek Series C preferred stock (the “Silver Creek warrants”). During the first quarter of 2017, Silver Creek issued additional Silver Creek warrants to purchase an aggregate of 1.8 million shares of Silver Creek Series C preferred stock. During the second quarter of 2017, Silver Creek issued additional Silver Creek warrants to purchase an aggregate of 0.3 million shares of Silver Creek Series C preferred stock. In June 2017, Silver Creek amended the outstanding warrant purchase agreements to increase the number of shares for which each warrant is redeemable.

During the third quarter of 2017, Silver Creek completed its Series C preferred stock financing, issuing 2.0 million shares of Series C preferred stock at $1.50 per share for proceeds of $2.9 million. In conjunction with this sale, Silver Creek also issued warrants to purchase 1.7 million shares of Series C preferred stock to investors. The sale of additional shares of Series C preferred stock in the third quarter resulted in the deconsolidation of Silver Creek, effective July 14, 2017. As such, the Company valued the warrants on that date. The warrants were valued at $5.2 million and $1.5 million as of July 14, 2017 and December 31, 2016, respectively, using a Black-Scholes option pricing model, probability-weighted for different exercise scenarios. The key assumptions utilized in the Black-Scholes option pricing model as of July 14, 2017 were a risk-free interest rate of 2.1%, expected dividend yield of 0.0%, expected volatility of 60.0% and expected term of 6.4 years – 7.0 years. The key assumptions utilized in the Black-Scholes option pricing model as of December 31, 2016 were a risk-free interest rate of 2.3%, expected dividend yield of 0.0%, expected volatility of 61.7% and expected term of 6.9 years. Changes in the fair value of the Silver Creek warrants are recognized as a component of “other income and expenses” in the condensed consolidated statements of operations and comprehensive income (loss). The change in fair value for the three and nine months ended September 30, 2017 was $0.1 million and $1.1 million, respectively, and is recorded in other income (expense) on the statement of operations and comprehensive loss.

There were no changes in valuation techniques or transfers between the fair value measurement levels during the three or nine months ended September 30, 2017 or during the year ended December 31, 2016.

Other Fair Value Measurements

The estimated fair value of the Convertible Notes was $51.0 million as of September 30, 2017. The Company estimated the fair value of the Convertible Notes by using a quoted market rate in an inactive market, which is classified as a Level 2 input. The carrying value of the Convertible Notes was $49.9 million as of September 30, 2017 due to the bifurcation of the conversion feature of the Convertible Notes as described more fully in Note 10, “Borrowings.”

As discussed in Note 10, “Borrowings,” in December 2015, the Company closed a private placement of $175.0 million aggregate principal amount of 2022 Notes. The Company estimated the fair value of the 2022 Notes by using publicly-available information related to one of the 2022 Notes borrower’s portfolio of debt investments based on unobservable inputs, which is classified as a Level 3 input. In connection with the completion of the Asset Sale, on April 3, 2017, the liability under the 2022 Notes was satisfied. The Company incurred a loss on extinguishment of $25.0 million as a result of the early repayment of the 2022 Notes, which is included in interest expense on the statement of operations. For additional information, see Note 3, “Sale of Commercial Business.”

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Marketable Securities	9 Months Ended
Marketable Securities	Sep. 30, 2017
Investments Debt And Equity Securities [Abstract]
Marketable Securities	8. Marketable Securities As of both September 30, 2017 and December 31, 2016, the Company maintained only cash equivalents comprised of money market funds. As of September 30, 2017, the Company did not hold any securities that were in an unrealized loss position. There were no realized gains or losses on available-for-sale securities for the three or nine months ended September 30, 2017 or 2016.

Accounts Payable, Accrued Expenses and Other

9 Months Ended

Sep. 30, 2017

Payables And Accruals [Abstract]

Accounts Payable, Accrued Expenses and Other

9. Accounts Payable, Accrued Expenses and Other

Accounts payable, accrued expenses and other as of September 30, 2017 and December 31, 2016 consisted of the following:

(in thousands)	September 30, 2017		December 31, 2016
Accounts payable	$	8,835	$	2,692
Accrued goods and services		4,688		8,233
Accrued clinical trial costs		3,845		8,776
Accrued drug purchase costs		950		480
Accrued payroll and related benefits		2,500		3,394
Accrued severance expenses		1,166		774
Accrued interest		578		2,100
Accrued dividends payable		19		19
Silver Creek warrant liability		—		1,499
Deferred tax incentives		1,402		1,402
Total accounts payable, accrued expenses and other	$	23,983	$	29,369

Borrowings

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Borrowings

10. Borrowings

2022 Notes

On December 22, 2015, the Company closed a private placement of $175.0 million aggregate principal amount of 2022 Notes. As a result of this placement, the Company received net proceeds of approximately $168.5 million, after deducting private placement and offering expenses payable by the Company. The 2022 Notes bore interest at a rate of 11.50% per year, payable semi-annually on June 15 and December 15 of each year, beginning on June 15, 2016. The 2022 Notes contained customary covenants, including covenants that limited or restricted the Company’s ability to incur liens, incur indebtedness and make certain restricted payments, but did not contain covenants related to future financial performance. The 2022 Notes were secured by a first priority lien on substantially all of the Company’s assets.

In connection with the completion of the Asset Sale on April 3, 2017, the liability under the 2022 Notes was satisfied. As a result of the early repayment, a loss on extinguishment of $25.0 million was recognized in interest expense in the condensed consolidated statement of operations and comprehensive income (loss) for the nine months ended September 30, 2017. The $25.0 million loss on extinguishment included a $20.1 million prepayment penalty and $4.9 million of amortization expense recognized for the remaining debt discount at settlement as a result of the early repayment. For the three and nine months ended September 30, 2017, interest expense related to the 2022 Notes was $0.0 million and $6.7 million, respectively. For the three and nine months ended September 30, 2016, interest expense related to the 2022 Notes was $5.2 million and $15.6 million, respectively. These amounts are included in discontinued operations.

Convertible Notes

In July 2013, the Company issued $125.0 million aggregate principal amount of Convertible Notes in an underwritten public offering. As a result of the Convertible Notes offering, the Company received net proceeds of approximately $120.6 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company.

The Convertible Notes bear interest at a rate of 4.50% per year, payable semiannually in arrears on January 15 and July 15 of each year, beginning on January 15, 2014. The Convertible Notes are general unsecured senior obligations of the Company and rank (i) senior in right of payment to any of the Company’s indebtedness that is expressly subordinated in right of payment to the Convertible Notes, (ii) equal in right of payment to any of the Company’s unsecured indebtedness that is not so subordinated, (iii) effectively junior in right of payment to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness and (iv) structurally junior to all indebtedness and other liabilities (including trade payables) of the Company’s subsidiaries.

The Company separately accounted for the liability and equity components of the Convertible Notes by bifurcating gross proceeds between the indebtedness, or liability component, and the embedded conversion option, or equity component. This bifurcation was done by estimating an effective interest rate as of the date of issuance for similar notes which do not contain an embedded conversion option. The gross proceeds received from the issuance of the Convertible Notes less the initial amount allocated to the indebtedness resulted in a $53.8 million allocation to the embedded conversion option. The embedded conversion option was recorded in stockholders’ deficit and as debt discount, to be subsequently amortized as interest expense over the term of the Convertible Notes. Underwriting discounts and commissions and offering expenses totaled $4.4 million and were allocated to the indebtedness and the embedded conversion option based on their relative values.

On April 13, 2016, the Company entered into separate, privately-negotiated conversion agreements (the “Conversion Agreements”) with certain holders of the Convertible Notes. Under the Conversion Agreements, such holders agreed to convert an aggregate principal amount of $64.2 million of Convertible Notes held by them. The Company initially settled each $1,000 principal amount of Convertible Notes surrendered for conversion by delivering 136 shares of the Company’s common stock on April 18, 2016. In total, the Company issued an aggregate of 8,732,152 shares of its common stock on this initial closing date. In addition, pursuant to the Conversion Agreements, at the additional closings (as defined in the Conversion Agreements), the Company issued an aggregate of 3,635,511 shares of the Company’s common stock representing an aggregate of $27.7 million as additional payments in respect of the conversion of the Convertible Notes. The number of additional shares was determined based on the daily VWAP (as defined in the Conversion Agreements) of the Company’s common stock for each of the trading days in the 10-day trading period following the date of the Conversion Agreements. The issuance of 12,367,663 total shares of the Company’s common stock pursuant to the Conversion Agreements resulted in an increase to common stock and additional paid-in capital of $101.0 million.

As a result of the conversion, the Company recognized an overall loss on extinguishment of $14.6 million representing the difference between the total settlement consideration transferred to the holders that was attributed to the liability component of the Convertible Notes, based on the fair value of that component at the time of conversion, and the net carrying value of the liability. The loss on extinguishment was recorded as interest expense during the second quarter of 2016. The remaining settlement consideration transferred was allocated to the reacquisition of the embedded conversion option and recognized as a $39.8 million reduction of additional paid-in capital. Transaction costs incurred with third parties related to the conversion were allocated to the liability and equity components and resulted in an additional $0.2 million of interest expense and a $0.2 million reduction of additional paid-in capital.

The outstanding Convertible Notes will mature on July 15, 2020 (the “Maturity Date”), unless earlier repurchased by the Company or converted at the option of holders. Holders may convert their Convertible Notes at their option at any time prior to the close of business on the business day immediately preceding April 15, 2020 only under the following circumstances:

•

during any calendar quarter commencing after September 30, 2013 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day;

•

during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined in the Convertible Notes) per $1,000 principal amount of Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; or

•

upon the occurrence of specified corporate events set forth in the indenture governing the Convertible Notes.

On or after April 15, 2020 until the close of business on the business day immediately preceding the Maturity Date, holders may convert their Convertible Notes at any time, regardless of the foregoing circumstances.

Following the repayment and satisfaction in full of the Company’s obligations to Hercules under the Loan Agreement, which occurred in December 2015, upon any conversion of the Convertible Notes, the Convertible Notes may be settled, at the Company’s election, in cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock.

The initial conversion rate of the Convertible Notes was 160.0000 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes, which is equivalent to an initial conversion price of $6.25 per share of common stock. As a result of the special dividend that was payable on May 26, 2017 to stockholders of record as of the close of business on May 17, 2017, the conversion rate of the Convertible Notes was adjusted from 160.0000 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes to 235.2112 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes. As a result of the one-for-ten reverse stock split of the Company’s common stock effected on September 5, 2017, the conversion rate of the Convertible Notes was further adjusted from 235.2112 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes to 23.5210 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes. The conversion rate will be subject to further adjustment in some events, but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the Maturity Date, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such a corporate event in certain circumstances.

In connection with a lawsuit filed by the trustee and certain holders of the Convertible Notes in the Court of Chancery in the State of Delaware, captioned Wells Fargo Bank, National Association, Wolverine Flagship Fund Trading Limited, Highbridge International LLC, and Highbridge Tactical Credit & Convertibles Master Fund, L.P. v. Merrimack Pharmaceuticals, Inc. (the “Delaware Action”), the Company deposited $60.0 million in proceeds from the Asset Sale into an escrow account. The funds will remain in escrow for the duration of the Delaware Action in order to provide security to the plaintiffs for their claims in the Delaware Action. For additional information regarding the Delaware Action, see Note 14, “Subsequent Events.”

For the three and nine months ended September 30, 2017, interest expense related to the Convertible Notes was $1.7 million and $5.0 million, respectively. For the three and nine months ended September 30, 2016, interest expense related to the Convertible Notes was $1.7 million and $21.1 million, respectively. The year-over-year decrease was primarily attributable to interest expense related to a reduction in the principal based on the conversion of some of the Convertible Notes that occurred in April 2016.

Future Minimum Payments under Outstanding Borrowings

Future minimum payments under outstanding borrowings as of September 30, 2017 are as follows:

(in thousands)	Convertible Notes
Remainder of 2017	$	—
2018		2,736
2019		2,736
2020 and thereafter		63,526
Total		68,998
Less interest		(8,207	)
Less unamortized discount		(10,907	)
Less current portion		—
Long-term debt	$	49,884

Stock-Based Compensation

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

As of December 31, 2015, there were 0.3 million shares of common stock available to be granted under the Company’s 2011 Stock Incentive Plan (the “2011 Plan”). The 2011 Plan is administered by the Company’s Board of Directors and permits the Company to grant incentive and non-qualified stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards.

In February 2016, 0.4 million additional shares of common stock became available for grant to employees, officers, directors and consultants under the 2011 Plan. At September 30, 2017, there were 0.3 million shares remaining available for grant under the 2011 Plan.

During the three and nine months ended September 30, 2017, the Company issued options to purchase 0.2 million and 2.1 million shares of common stock, respectively. During the three and nine months ended September 30, 2016 the Company issued options to purchase 0.0 million and 0.4 million shares of common stock, respectively. These options generally vest over a three-year period for employees. Options granted to directors vest immediately.

As described in Note 3, “Sale of Commercial Business,” the Board of Directors authorized and declared a special cash dividend of $140.0 million on the Company's common stock, which was payable on May 26, 2017 to stockholders of record as of the close of business on May 17, 2017. The Board of Directors determined, in accordance with the adjustment provision of each of the Company’s 1999 Stock Option Plan, as amended, the 2008 Stock Incentive Plan, as amended, and the 2011 Plan (collectively, the “Equity Plans”), that the special cash dividend was unusual and non-recurring and that appropriate adjustment to the stock options to purchase shares of the Corporation’s common stock outstanding under the Equity Plans was required. The Company treated this adjustment as a modification to the original stock option grant because the terms of the agreements were modified in order to preserve the value of the option awards after a large non-recurring cash dividend. The calculation of the incremental compensation expense is based on the excess of the fair value of the award measured immediately before and after the modification. As a result, the Company recognized an incremental compensation expense of $5.6 million associated with the modification that occurred in the second quarter of 2017.

On August 11, 2017, the Company’s stockholders approved an amendment to the Company's certificate of incorporation to effect the Reverse Split. On September 5, 2017, the Company filed the amendment to its certificate of incorporation to effect the Reverse Split, and on September 6, 2017, the Reverse Split was effective for trading purposes. As a result of the Reverse Split, every ten shares of common stock issued and outstanding was converted into one share of common stock, reducing the number of issued and outstanding shares of common stock from approximately 132.8 million shares to approximately 13.28 million shares. No fractional shares were issued in connection with the Reverse Split. The amendment to the certificate of incorporation also proportionately reduced the number of authorized shares of common stock from 200 million to 20 million. The Reverse Split did not change the par value of the common stock. The Reverse Split did not change the number of authorized shares or par value of the Company’s preferred stock, of which there are no shares issued or outstanding. All outstanding stock options and convertible notes entitling their holders to purchase shares of common stock or acquire shares of common stock upon conversion, as the case may be, were adjusted as a result of the Reverse Split, as required by the terms of these securities.

The fair value of stock options granted to employees during the three and nine months ended September 30, 2017 and 2016 was estimated at the date of grant using the following assumptions:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2017	2016	2017	2016
Risk-free interest rate	1.7 – 1.8%	1.1 – 1.4%	1.7 – 2.1%	1.1 – 1.5%
Expected dividend yield	0%	0%	0%	0%
Expected term	5.0 – 5.8 years	5.8 years	5.0 – 6.1 years	5.0 – 5.8 years
Expected volatility	64 – 66%	67%	64 – 68%	67 – 69%

The Company uses the simplified method to calculate the expected term, as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate expected term. The computation of expected volatility is based on the historical volatility of comparable companies from a representative peer group selected based on industry and market capitalization. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected life of the stock options. Management estimates expected forfeitures based on historical experience and recognizes compensation costs only for those equity awards expected to vest.

In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting,” which simplifies several areas of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either liabilities or equity and classification of excess tax benefits on the statement of cash flows. This guidance also permits a new entity-wide accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The Company adopted the guidance, electing to account for forfeitures when they occur, and it did not have an impact on the consolidated financial statements.

The Company recognized stock-based compensation expense during the three and nine months ended September 30, 2017 and 2016 as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2017		2016		2017		2016
Employee awards:
Research and development expense	$	734	$	1,216	$	6,118	$	4,206
General and administrative expense		846		958		4,992		4,045
Total stock-based compensation expense	$	1,580	$	2,174	$	11,110	$	8,251

The following table summarizes stock option activity during the nine months ended September 30, 2017:

						Weighted-Average Remaining		Aggregate
(in thousands, except per share amounts)	Options			Weighted-Average Exercise Price		Contractual Term (in years)		Intrinsic Value
Outstanding at December 31, 2016		1,902		$	57.68		5.97	$	7,564
Granted		2,098		$	23.77
Exercised		(290	)	$	21.74
Forfeited		(1,886	)	$	59.37
Outstanding at September 30, 2017		1,824		$	22.65		6.21	$	1,187
Vested and expected to vest at September 30, 2017		1,822		$	22.64		6.21	$	1,187
Exercisable at September 30, 2017		1,159		$	26.71		4.34	$	969

The weighted-average grant date fair value per share of stock options granted during the three and nine months ended September 30, 2017 was $7.68 and $4.06, respectively. The weighted-average grant date fair value per share of stock options granted during the three and nine months ended September 30, 2016 was $30.66 and $33.19, respectively.

The aggregate intrinsic value is calculated as the difference between the exercise price of the stock options and the fair value of the underlying common stock. The aggregate intrinsic value of stock options exercised during the three and nine months ended September 30, 2017 was $0.0 million and $2.3 million, respectively. The aggregate intrinsic value of stock options exercised during the three and nine months ended September 30, 2016 was $1.1 million and $3.8 million, respectively.

As of September 30, 2017, there was $5.7 million of total unrecognized stock-based compensation expense related to unvested employee stock awards. The Company expects to recognize this expense over a weighted-average period of approximately 2.77 years.

Investment in Silver Creek

9 Months Ended

Sep. 30, 2017

Noncontrolling Interest [Abstract]

Investment in Silver Creek

12. Investment in Silver Creek

On August 20, 2010, the Company acquired a controlling financial interest in Silver Creek. At such time, the Company had the ability to direct the activities of Silver Creek that most significantly impacted Silver Creek’s economic performance through its ownership percentage and through the board of director seats controlled by the Company. As such, Silver Creek was consolidated by the Company.

Since the Company acquired its financial interest, Silver Creek has raised funding through the issuance of Series A, B and C preferred stock. The Company has not participated in any Silver Creek financings nor has it provided any funding. As of December 31, 2016, the Company held an ownership interest in Silver Creek greater than 50% and maintained the ability to control the board of directors and the activities that most significantly impacted the economic performance of Silver Creek.

During the third quarter of 2017, Silver Creek completed its Series C preferred stock financing, which reduced the Company’s ownership percentage in Silver Creek below 50% and resulted in the Company no longer controlling the Silver Creek board of directors. As of September 30, 2017, the Company’s ownership percentage in Silver Creek was approximately 43%. The Company determined that it is no longer the primary beneficiary of Silver Creek since the Company does not control the board of directors and does not direct the activities that have the most significant impact on Silver Creek’s economic performance. Therefore, the Company deconsolidated Silver Creek from its financial statements on July 13, 2017 in accordance with ASC 810-10-40-4(c), Consolidation. Starting on July 14, 2017, the Company accounted for its investment in Silver Creek under the equity method of accounting as it has the ability to exercise significant influence over Silver Creek. Under the equity method of accounting, the Company will record its proportionate share of the investee’s earnings (losses) in its results of operations with a corresponding increase (decrease) in the carrying value of the investment. Silver Creek continues to be a related party to the Company after deconsolidation.

The Company recorded a gain on the deconsolidation of Silver Creek of $10.8 million for the three and nine months ended September 30, 2017 in the condensed consolidated statement of operations and comprehensive income (loss). On the date of deconsolidation, the fair value of the Company’s investment in Silver Creek exceeded the Company’s share of the net assets of Silver Creek, which generated the gain. On July 14, 2017, the Company recorded its investment in Silver Creek at a fair value of $11.4 million, which was based on a third party valuation report. The gain on deconsolidation includes the following:

(in thousands)
Fair value of the Company's retained investment in Silver Creek	$	11,400
Carrying value of non-controlling interest		(1,852	)
Derecognition of Silver Creek's net liabilities		1,300
Gain recognized on deconsolidation of Silver Creek	$	10,848

The change in the non-controlling interest related to Silver Creek was as follows:

(in thousands)	Non- Controlling Interest
Balance at December 31, 2016	$	(1,539	)
Net loss attributable to Silver Creek through July 13, 2017		(1,160	)
Issuance of Silver Creek Series C preferred stock		847
Balance at date of deconsolidation		(1,852	)
Carrying value of non-controlling interest		1,852
Balance at September 30, 2017	$	—

(in thousands)	Non- Controlling Interest
Balance at December 31, 2015	$	239
Net loss attributable to Silver Creek		(600	)
Balance at September 30, 2016	$	(361	)

Recent Accounting Pronouncements

9 Months Ended

Sep. 30, 2017

Accounting Changes And Error Corrections [Abstract]

Recent Accounting Pronouncements

13. Recent Accounting Pronouncements

In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606),” which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new 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. This guidance was originally effective for interim and annual periods beginning after December 15, 2016 and allows for adoption using a full retrospective method, or a modified retrospective method. Early adoption was originally not permitted. Subsequent to the issuance of ASU 2014-09, the FASB also issued the following updates related to ASC 606, Revenue from Contracts with Customers:

•

In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date,” whereby the effective date for the new revenue standard was deferred by one year. As a result of ASU 2015-14, the new revenue standard is now effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017, and early adoption is now permitted for annual periods beginning after December 15, 2016, including interim periods within that annual period.

•

In March 2016, the FASB issued ASU 2016-08, “Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” to clarify the implementation guidance on principal versus agent considerations.

•

In April 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing,” to clarify the principle for determining whether a good or service is “separately identifiable” from other promises in the contract and to clarify the categorization of licenses of intellectual property.

•

In May 2016, the FASB issued ASU 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Technical Expedients,” to clarify guidance on transition, determining collectability, non-cash consideration and the presentation of sales and other similar taxes.

The Company does not currently have any revenue generating contracts with customers due to the sale of its commercial business in the second quarter of 2017. The Company expects to adopt the new revenue standard on January 1, 2018 using the modified retrospective approach.

In January 2016, the FASB issued ASU 2016-01, “Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Liabilities,” which contains a number of provisions related to the measurement, presentation and disclosure of financial instruments. This guidance will be effective for annual reporting periods beginning after December 15, 2017, including interim periods within those annual periods. Early adoption of this guidance is not permitted with the exception of certain specific presentation requirements that are not currently applicable to the Company. The Company does not anticipate a material impact to the consolidated financial statements as a result of the adoption of this guidance.

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” which supersedes all existing lease accounting guidance within ASC 840, Leases. The new standard requires that lease assets and lease liabilities be recognized by lessees for those leases previously classified as operating leases under ASC 840, with limited exceptions. This update also creates a new definition of a lease and provides guidance as to whether a contract is or contains a lease. This guidance will be effective for annual reporting periods beginning after December 15, 2018, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that the adoption of this guidance may have on the consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” which represents a new credit loss standard that will change the impairment model for most financial assets and certain other financial instruments. Specifically, this guidance will require entities to utilize a new “expected loss” model as it relates to trade and other receivables. In addition, entities will be required to recognize an allowance for estimated credit losses on available-for-sale debt securities, regardless of the length of time that a security has been in an unrealized loss position. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that the adoption of this guidance may have on the consolidated financial statements.

In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments,” which is intended to reduce diversity in practice in how entities present certain types of cash transactions in the statement of cash flows. This guidance also clarifies how the predominance principle should be applied when classifying cash receipts and cash payments that have attributes of more than one class of cash flows. This guidance will be effective for annual reporting periods beginning after December 15, 2017, including interim periods within those annual reporting periods, and early adoption is permitted. An entity that elects early adoption must adopt all of the amendments in the same period. The Company does not anticipate a material impact to the consolidated financial statements as a result of the adoption of this guidance.

In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting,” which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The standard should be applied prospectively to awards modified on or after the adoption date. This guidance will be effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, including adoption in any interim period. The Company is currently evaluating the potential impact that the adoption of this guidance may have on the consolidated financial statements.

Other accounting standards that have been issued by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On October 6, 2017, the Company entered into a settlement agreement (the “Settlement Agreement”) to resolve the Delaware Action. In accordance with the Settlement Agreement, the Company paid $32.5 million in cash to the noteholder plaintiffs, which represents $0.90 per each $1.00 of Convertible Notes held by the noteholder plaintiffs, plus accrued and unpaid interest on the Convertible Notes held by the noteholder plaintiffs through October 2, 2017. The noteholder plaintiffs collectively held approximately $35.8 million aggregate principal amount of the Convertible Notes. In addition, the Company paid a total of $3.8 million in attorneys’ fees and expenses to the plaintiffs’ attorneys. The noteholder plaintiffs have executed a full release in favor of the Company for any claims arising out of or related to the Delaware Action or the Convertible Notes, which release shall become effective upon the occurrence of certain conditions. The Company paid such settlement amounts on or about October 11, 2017. On October 13, 2017, in connection with the entry into the Settlement Agreement, the Company commenced a cash tender offer (the “Tender Offer”) to purchase any and all of its remaining $25.0 million aggregate principal amount of outstanding Convertible Notes. Upon the terms and subject to the conditions set forth in the Company’s Offer to Purchase, dated October 13, 2017, and the related Letter of Transmittal, the Company is offering to pay, in cash, an amount equal to $900 per $1,000 principal amount of Convertible Notes purchased, plus accrued and unpaid interest to, but not including, the date of purchase. The Tender Offer will expire on November 10, 2017, or any other date and time to which the Company extends such Tender Offer, unless earlier terminated. On October 16, 2017, the Company and Ipsen reached agreement on the final working capital adjustment related to the Asset Sale, resulting in the Company receiving cash proceeds of $4.9 million.

Recent Accounting Pronouncements (Policies)

9 Months Ended

Sep. 30, 2017

Accounting Changes And Error Corrections [Abstract]

Equity Method Accounting

The condensed consolidated financial statements have historically included the accounts of the Company and Silver Creek Pharmaceuticals, Inc. (“Silver Creek”) with all intercompany transactions and balances eliminated in consolidation. Silver Creek represented a variable interest entity that the Company consolidated as the primary beneficiary. As discussed in Note 12, “Investment in Silver Creek,” Silver Creek completed a preferred stock financing in the third quarter of 2017, which reduced the Company’s ownership percentage in Silver Creek below 50% and resulted in the Company no longer controlling the Silver Creek board of directors. The Company determined that it is no longer the primary beneficiary of Silver Creek since the Company does not control the board of directors and does not direct the activities that have the most significant impact on Silver Creek’s economic performance. Therefore, the Company deconsolidated Silver Creek from its financial statements in the third quarter of 2017 in accordance with Accounting Standards Codification (“ASC”) 810-10-40-4(c), Consolidation. The Company accounts for its investment in Silver Creek under the equity method of accounting as of September 30, 2017.

Recent Accounting Pronouncements

•

Sale of Commercial Business (Tables)

9 Months Ended

Sep. 30, 2017

Discontinued Operations And Disposal Groups [Abstract]

Schedule of Discontinued Operations and Assets Held for Sale

Discontinued operations for the three and nine months ended September 30, 2017 and 2016 includes the following:

(in thousands)	Three Months Ended September 30,					Nine Months Ended September 30,
	2017		2016			2017			2016
Revenues:
Product revenues, net	$	—	$	14,493		$	16,135		$	37,312
License and collaboration revenues		—		12,417			7,797			43,062
Other revenues		—		1,161			1,973			2,659
Total revenues		—		28,071			25,905			83,033
Costs and expenses:
Cost of revenues		—		1,010			3,890			3,593
Research and development expenses		—		3,830			3,730			22,012
Selling, general and administrative expenses		—		11,600			8,732			35,485
Restructuring expenses		—		—			9,535			—
Total costs and expenses		—		16,440			25,887			61,090
Other income and expenses:
Interest expense		—		(5,291	)		(6,743	)		(15,871	)
Gain on sale of commercial business		3,497		—			601,670			—
Income from discontinued operations	$	3,497	$	6,340		$	594,945		$	6,072
Income tax benefit (expense)		4,959		(9,770	)		(46,951	)		(9,770	)
Total income (loss) from discontinued operations	$	8,456	$	(3,430	)	$	547,994		$	(3,698	)

Schedule of Carrying Value of Assets and Liabilities Classified as Discontinued Operations Relates to Commercial Business

The carrying value of the assets and liabilities of the Commercial Business classified as “Discontinued operations” in the condensed consolidated balance sheets is as follows:

(in thousands)	December 31, 2016
Assets
Current assets:
Accounts receivable, net	$	17,194
Inventory		14,554
Prepaid expenses and other current assets		1,547
Total current assets held for sale		33,295
Property and equipment, net		1,553
Intangible assets, net		3,977
Goodwill		3,605
Total long-term assets held for sale		9,135
Liabilities
Current liabilities:
Accounts payable, accrued expenses and other		20,613
Deferred revenues		36,226
Total current liabilities held for sale		56,839
Deferred revenues, net of current portion		25,673
Total liabilities held for sale		25,673

Schedule of Inventory of Commercial Business

Inventory of the Commercial Business as of December 31, 2016 consisted of the following:

(in thousands)	December 31, 2016
Raw materials	$	4,483
Work in process		8,651
Finished goods		1,420
Total inventory	$	14,554

Summary of Charges Related to Restructuring Activities

The following table summarizes the charges related to the restructuring activities as of September 30, 2017:

(in thousands)	Accrued Restructuring Expenses at December 31, 2016		Expenses		Less: Payments		Accrued Restructuring Expenses at September 30, 2017
Severance, benefits and related costs	$	—	$	9,521	$	8,434	$	1,087
Totals	$	—	$	9,521	$	8,434	$	1,087

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721533-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721665-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1474-107760

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721683-107760

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=84176398&loc=SL51724579-110230

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5C
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721675-107760

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721663-107760

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2941-110230

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721659-107760

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721671-107760

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5D
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721677-107760

+ Details

Net Income (Loss) Per Common Share (Tables)

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Schedule of Outstanding Securities Excluded from Computation of Diluted Loss Per Share

Outstanding securities excluded from the calculation of diluted loss per share for the three and nine months ended September 30, 2017 and 2016 are shown in the chart below:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2017		2016		2017		2016
Outstanding options to purchase common stock		1,824		2,100		1,824		2,100
Conversion of the Convertible Notes		1,216		1,216		1,216		1,216

Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following tables show assets measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016:

	September 30, 2017
(in thousands)	Level 1		Level 2		Level 3
Assets:
Money market funds	$	99,079	$	—	$	—
Totals	$	99,079	$	—	$	—

	December 31, 2016
(in thousands)	Level 1		Level 2		Level 3
Assets:
Money market funds	$	12,373	$	—	$	—
Totals	$	12,373	$	—	$	—

Liabilities:
Silver Creek warrant liability	$	—	$	—	$	1,499
Totals	$	—	$	—	$	1,499

Accounts Payable, Accrued Expenses and Other (Tables)

9 Months Ended

Sep. 30, 2017

Payables And Accruals [Abstract]

Schedule of Accounts Payable, Accrued Expenses and Other

Accounts payable, accrued expenses and other as of September 30, 2017 and December 31, 2016 consisted of the following:

(in thousands)	September 30, 2017		December 31, 2016
Accounts payable	$	8,835	$	2,692
Accrued goods and services		4,688		8,233
Accrued clinical trial costs		3,845		8,776
Accrued drug purchase costs		950		480
Accrued payroll and related benefits		2,500		3,394
Accrued severance expenses		1,166		774
Accrued interest		578		2,100
Accrued dividends payable		19		19
Silver Creek warrant liability		—		1,499
Deferred tax incentives		1,402		1,402
Total accounts payable, accrued expenses and other	$	23,983	$	29,369

Borrowings (Tables)

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Schedule of Future Minimum Payments under the Loans Payable

Future minimum payments under outstanding borrowings as of September 30, 2017 are as follows:

(in thousands)	Convertible Notes
Remainder of 2017	$	—
2018		2,736
2019		2,736
2020 and thereafter		63,526
Total		68,998
Less interest		(8,207	)
Less unamortized discount		(10,907	)
Less current portion		—
Long-term debt	$	49,884

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Assumptions Used to Calculate Fair Value of Options Granted to Employees

The fair value of stock options granted to employees during the three and nine months ended September 30, 2017 and 2016 was estimated at the date of grant using the following assumptions:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2017	2016	2017	2016
Risk-free interest rate	1.7 – 1.8%	1.1 – 1.4%	1.7 – 2.1%	1.1 – 1.5%
Expected dividend yield	0%	0%	0%	0%
Expected term	5.0 – 5.8 years	5.8 years	5.0 – 6.1 years	5.0 – 5.8 years
Expected volatility	64 – 66%	67%	64 – 68%	67 – 69%

Schedule of Recognized Stock-Based Compensation Expense

The Company recognized stock-based compensation expense during the three and nine months ended September 30, 2017 and 2016 as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2017		2016		2017		2016
Employee awards:
Research and development expense	$	734	$	1,216	$	6,118	$	4,206
General and administrative expense		846		958		4,992		4,045
Total stock-based compensation expense	$	1,580	$	2,174	$	11,110	$	8,251

Summary of Stock Option Activity

The following table summarizes stock option activity during the nine months ended September 30, 2017:

						Weighted-Average Remaining		Aggregate
(in thousands, except per share amounts)	Options			Weighted-Average Exercise Price		Contractual Term (in years)		Intrinsic Value
Outstanding at December 31, 2016		1,902		$	57.68		5.97	$	7,564
Granted		2,098		$	23.77
Exercised		(290	)	$	21.74
Forfeited		(1,886	)	$	59.37
Outstanding at September 30, 2017		1,824		$	22.65		6.21	$	1,187
Vested and expected to vest at September 30, 2017		1,822		$	22.64		6.21	$	1,187
Exercisable at September 30, 2017		1,159		$	26.71		4.34	$	969

Investment in Silver Creek (Tables)

9 Months Ended

Sep. 30, 2017

Noncontrolling Interest [Abstract]

Schedule of Gain on Deconsolidation

The gain on deconsolidation includes the following

(in thousands)
Fair value of the Company's retained investment in Silver Creek	$	11,400
Carrying value of non-controlling interest		(1,852	)
Derecognition of Silver Creek's net liabilities		1,300
Gain recognized on deconsolidation of Silver Creek	$	10,848

Schedule of Non-Controlling Interest in Subsidiary

The change in the non-controlling interest related to Silver Creek was as follows:

(in thousands)	Non- Controlling Interest
Balance at December 31, 2016	$	(1,539	)
Net loss attributable to Silver Creek through July 13, 2017		(1,160	)
Issuance of Silver Creek Series C preferred stock		847
Balance at date of deconsolidation		(1,852	)
Carrying value of non-controlling interest		1,852
Balance at September 30, 2017	$	—

(in thousands)	Non- Controlling Interest
Balance at December 31, 2015	$	239
Net loss attributable to Silver Creek		(600	)
Balance at September 30, 2016	$	(361	)

Nature of the Business - Additional Information (Detail)		1 Months Ended
	Oct. 16, 2017 USD ($)	Sep. 30, 2017 USD ($) Program	Apr. 03, 2017 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of development programs active \| Program		2
Ipsen [Member] \| Asset Sale Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront cash payment received			$ 575,000,000
Working capital adjustments received		$ 800,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional payments receivable on achievement of certain milestone events			450,000,000
Baxalta [Member] \| License and Collaboration Agreements [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Net milestone payments expected to be received			$ 33,000,000
Subsequent Event [Member] \| Ipsen [Member] \| Asset Sale Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Working capital adjustments received	$ 4,900,000

Basis of Presentation and Consolidation - Additional Information (Detail)		9 Months Ended
	Aug. 11, 2017 shares	Sep. 30, 2017 shares	Sep. 05, 2017 shares	Dec. 31, 2016 shares
Summary Of Significant Accounting Policies [Line Items]
Reverse stock split description		Reverse Split, every ten shares of common stock issued and outstanding was converted into one share of common stock
Reverse stock split, conversion ratio	0.1
Common stock, shares issued	132,800,000	13,274,000	13,280,000	13,020,000
Common stock, shares outstanding	132,800,000	13,274,000	13,280,000	13,020,000
Common stock, shares authorized	200,000,000	20,000,000	20,000,000	20,000,000
Number of fractional shares issued			0
Preferred stock, shares issued		0	0	0
Preferred stock, shares outstanding		0	0	0
Silver Creek [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest percentage held by parent		50.00%

Sale of Commercial Business - Additional Information (Detail)						1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 16, 2017 USD ($)	Apr. 05, 2017 USD ($)	Apr. 03, 2017 USD ($) ft²	Jan. 08, 2017 Employee	May 05, 2011 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 22, 2015
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate principal amount outstanding redeemed									$ 175,000,000
Dividend date declared									Apr. 05, 2017
Special cash dividend paid		$ 140,000,000
Dividend payable date		May 26, 2017
Dividend payable, date of record		May 17, 2017
Restructuring expenses								$ 809,000		$ 809,000
January 2017 Corporate Restructuring [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring activity, announcement date									Jan. 08, 2017
Restructuring and related cost, headcount reduction percentage				30.00%
Restructuring and related cost, number of employees after headcount reduction \| Employee				80
January 2017 Corporate Restructuring [Member] \| Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring expenses									$ 9,500,000
January 2017 Corporate Restructuring [Member] \| Contractual Termination Benefits [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring expenses							$ 0		$ 9,500,000
January 2017 Corporate Restructuring [Member] \| One-time Employee Termination Benefits [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring And Related Activities Description									One-time employee termination benefits are comprised of severance, benefits and related costs, all of which are expected to result in cash expenditures. The majority of these payments were made during the second quarter of 2017. The remaining payments represent severance payments that will be paid over one year.
Severance payments payment period									1 year
2022 Notes [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Interest rate (as a percent)											11.50%
Asset Sale Agreement [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Transition services agreement period			24 months
Special cash dividend paid			$ 140,000,000
Gain from discontinued operations							$ 3,500,000		$ 601,700,000
Asset Sale Agreement [Member] \| 2022 Notes [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate principal amount outstanding redeemed			175,000,000
Additional premium payment			$ 20,100,000
Interest rate (as a percent)			11.50%
Aggregate principal amount of interest redeemed			$ 7,400,000
Ipsen [Member] \| Asset Sale Agreement [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Working capital adjustments received						$ 800,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Subsequent Event [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Working capital adjustments received	$ 4,900,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Manufacturing Facility [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Area of sublease property \| ft²			70,237
Lease expiration date			Jun. 30, 2019
Ipsen [Member] \| Asset Sale Agreement [Member] \| Clinical Trials in Pancreas as First-Line Treatment [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			$ 225,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Clinical Trials in Small Cell Lung Cancer [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			150,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Other Unrelated Clinical Trials [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			75,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Development and Commercialization Milestones [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum amount of milestone payments that can be received			33,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Sale Milestones in Major European Countries [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			18,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Sale Milestones in Major Non-European and Non-Asian Country [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			5,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Clinical Trials in Lung Cancer [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			10,000,000
Ipsen [Member] \| Asset Sale Agreement [Member] \| Maximum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			$ 450,000,000
PharmaEngine [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Upfront license fees paid					$ 10,000,000
PharmaEngine [Member] \| Development and Regulatory Milestone [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum milestone payment obligation					80,000,000
PharmaEngine [Member] \| Sales Milestone [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum milestone payment obligation					$ 130,000,000

Sale of Commercial Business - Schedule of Discontinued Operations and Assets Held for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other income and expenses:
Income tax benefit (expense)	$ 5,000	$ (9,800)	$ (47,000)	$ (9,800)
Total income (loss) from discontinued operations	8,456	(3,430)	547,994	(3,698)
Commercial Business [Member]
Revenues:
Product revenues, net		14,493	16,135	37,312
License and collaboration revenues		12,417	7,797	43,062
Other revenues		1,161	1,973	2,659
Total revenues		28,071	25,905	83,033
Costs and expenses:
Cost of revenues		1,010	3,890	3,593
Research and development expenses		3,830	3,730	22,012
Selling, general and administrative expenses		11,600	8,732	35,485
Restructuring expenses			9,535
Total costs and expenses		16,440	25,887	61,090
Other income and expenses:
Interest expense		(5,291)	(6,743)	(15,871)
Gain on sale of commercial business	3,497		601,670
Income from discontinued operations	3,497	6,340	594,945	6,072
Income tax benefit (expense)	4,959	(9,770)	(46,951)	(9,770)
Total income (loss) from discontinued operations	$ 8,456	$ (3,430)	$ 547,994	$ (3,698)

Sale of Commercial Business - Schedule of Carrying Value of Assets and Liabilities Classified as Assets Held for Sale Relates to Commercial Business (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Current assets:
Total current assets held for sale	$ 33,295
Total long-term assets held for sale	9,135
Current liabilities:
Total current liabilities held for sale	56,839
Total liabilities held for sale	25,673
Commercial Business [Member]
Current assets:
Accounts receivable, net	17,194
Inventory	14,554
Prepaid expenses and other current assets	1,547
Total current assets held for sale	33,295
Property and equipment, net	1,553
Intangible assets, net	3,977
Goodwill	3,605
Total long-term assets held for sale	9,135
Current liabilities:
Accounts payable, accrued expenses and other	20,613
Deferred revenues	36,226
Total current liabilities held for sale	56,839
Deferred revenues, net of current portion	25,673
Total liabilities held for sale	$ 25,673

Sale of Commercial Business - Schedule of Inventory of Commercial Business (Detail) - Commercial Business [Member] $ in Thousands	Dec. 31, 2016 USD ($)
Inventory [Line Item]
Raw materials	$ 4,483
Work in process	8,651
Finished goods	1,420
Total inventory	$ 14,554

Sale of Commercial Business - Summary of Charges Related to Restructuring Activities (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Accrued Restructuring Expenses at Dec 31, 2016		$ 774
Expenses	$ 809		$ 809
Accrued Restructuring Expenses at September 30, 2017		1,166
Commercial Business [Member]
Restructuring Cost And Reserve [Line Items]
Expenses		9,521
Less: Payments		8,434
Accrued Restructuring Expenses at September 30, 2017		1,087
Commercial Business [Member] \| Severance Benefits and Related Costs [Member]
Restructuring Cost And Reserve [Line Items]
Expenses		9,521
Less: Payments		8,434
Accrued Restructuring Expenses at September 30, 2017		$ 1,087

Going Concern - Additional Information (Detail) - USD ($) $ in Thousands				1 Months Ended	9 Months Ended
	Oct. 16, 2017	Apr. 05, 2017	Apr. 03, 2017	Sep. 30, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 22, 2015	Jul. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unrestricted cash and cash equivalents				$ 107,245	$ 107,245	$ 17,200	$ 21,524	$ 36,463	$ 185,606
Special cash dividend distributed		$ 140,000
Dividend payable date		May 26, 2017
Dividend payable, date of record		May 17, 2017
Aggregate principal amount outstanding redeemed					175,000
Convertible Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)			4.50%								4.50%
Deposited into escrow account			$ 60,000	60,000	$ 60,000
2022 Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)										11.50%
Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Special cash dividend distributed			$ 140,000
Asset Sale Agreement [Member] \| 2022 Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)			11.50%
Aggregate principal amount outstanding redeemed			$ 175,000
Additional premium payment			20,100
Ipsen [Member] \| Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront cash payment received			$ 575,000
Working capital adjustments received				$ 800
Subsequent Event [Member] \| Ipsen [Member] \| Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Working capital adjustments received	$ 4,900

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Current Income tax expense			$ 8,000
Income tax payable	$ 1,844		1,844
Income tax expense (benefit)	(2,133)	$ (9,770)	(32,372)	$ (9,770)
Income tax expense (benefit) in discontinued operations	$ (5,000)	$ 9,800	47,000	$ 9,800
Income tax provision in discontinued operations			224,300
Valuation allowance in discontinued operations			$ 177,400

- Definition

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

+ References + Details

Net Income (Loss) Per Common Share - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jul. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Amounts allocated to participating securities	$ 0	$ 0	$ 0	$ 0
Participating securities outstanding, shares	0	0	0	0
Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Aggregate principal amount					$ 125,000,000
Aggregate principal amount of outstanding debt	$ 60,800,000		$ 60,800,000

Net Income (Loss) Per Common Share - Schedule of Outstanding Securities Excluded from Computation of Diluted Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Outstanding Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities excluded from calculation of diluted loss per share	1,824	2,100	1,824	2,100
Conversion of the Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding securities excluded from calculation of diluted loss per share	1,216	1,216	1,216	1,216

Fair Value of Financial Instruments - Schedule of Assets Measured at Fair Value on a Recurring Basis (Detail) - Recurring Basis [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	$ 99,079	$ 12,373
Level 1 [Member] \| Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	$ 99,079	12,373
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities		1,499
Level 3 [Member] \| Silver Creek [Member] \| Warrant Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities		$ 1,499

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended		12 Months Ended
	Jul. 14, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Sep. 05, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 22, 2015
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred stock, shares issued		0	0		0	0
Transfers between fair value measurement levels		$ 0	$ 0		$ 0
Loss on extinguishment of debt			4,887,000	$ 14,566,000
Senior Convertible Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Aggregate principal amount of outstanding debt		49,900,000	49,900,000
Senior Convertible Notes [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fair value of debt		51,000,000	51,000,000
2022 Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Aggregate principal amount of loan									$ 175,000,000
Loss on extinguishment of debt			25,000,000
Silver Creek [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Net cash proceeds from stock issuance			3,994,000	$ 1,185,000
Risk-free interest rate	2.10%				2.30%
Expected dividend yield	0.00%				0.00%
Expected volatility	60.00%				61.70%
Expected term					6 years 10 months 25 days
Change in fair value of warrant		$ 100,000	$ 1,100,000
Silver Creek [Member] \| Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Expected term	6 years 4 months 25 days
Silver Creek [Member] \| Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Expected term	7 years
Silver Creek [Member] \| Series C Preferred Stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issued to purchase preferred stock, shares		1,700,000	1,700,000		1,900,000		300,000	1,800,000
Preferred stock, shares issued		2,000,000	2,000,000
Preferred stock price per share		$ 1.50	$ 1.50
Net cash proceeds from stock issuance		$ 2,900,000
Warrants to purchase preferred stock, value	$ 5,200,000				$ 1,500,000

Marketable Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended
Marketable Securities - Additional Information (Detail)	Sep. 30, 2017 USD ($) Security	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Security	Sep. 30, 2016 USD ($)
Amortized Cost And Fair Value Debt Securities [Abstract]
Number of securities held in unrealized loss position \| Security	0		0
Realized gains (losses) on sale of available-for-sale securities \| $	$ 0	$ 0	$ 0	$ 0

Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts Payable And Accrued Liabilities [Line Items]
Accounts payable	$ 8,835	$ 2,692
Accrued goods and services	4,688	8,233
Accrued clinical trial costs	3,845	8,776
Accrued drug purchase costs	950	480
Accrued payroll and related benefits	2,500	3,394
Accrued severance expenses	1,166	774
Accrued interest	578	2,100
Accrued dividends payable	19	19
Deferred tax incentives	1,402	1,402
Total accounts payable, accrued expenses and other	$ 23,983	29,369
Silver Creek [Member]
Accounts Payable And Accrued Liabilities [Line Items]
Warrant liability		$ 1,499

Borrowings - 2022 Notes - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 22, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule Of Debt Instruments [Line Items]
Loss on extinguishment of debt				$ 4,887	$ 14,566
Interest expense		$ 1,659	$ 1,560	30,400	20,708
2022 Notes [Member]
Schedule Of Debt Instruments [Line Items]
Aggregate principal amount	$ 175,000
Net proceeds from the debt issuance	$ 168,500
Interest rate (as a percent)	11.50%
Loss on extinguishment of debt				25,000
Prepayment penalty of extinguishment of debt				20,100
Amortization expense recognized for remaining debt discount at settlement				4,900
Interest expense		$ 0	$ 5,200	6,700	$ 15,600
2022 Notes [Member] \| Interest Expense [Member]
Schedule Of Debt Instruments [Line Items]
Loss on extinguishment of debt				$ 25,000

Borrowings - Convertible Notes - Additional Information (Detail)							1 Months Ended	3 Months Ended			9 Months Ended
	Sep. 05, 2017 shares	Aug. 11, 2017 shares	May 26, 2017	Apr. 18, 2016 shares	Apr. 13, 2016 USD ($) shares	Jul. 31, 2013 USD ($) $ / shares	Jul. 31, 2013 USD ($) $ / shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($) shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Apr. 03, 2017 USD ($)	Dec. 31, 2016 shares
Debt Instrument [Line Items]
Principal amount of convertible notes due 2020 converted into shares of common stock												$ 64,209,000
Common stock, shares issued \| shares	13,280,000	132,800,000						13,274,000			13,274,000			13,020,000
Loss on extinguishment of debt											$ 4,887,000	14,566,000
Debt maturity date											Jul. 15, 2020
Reverse stock split description											Reverse Split, every ten shares of common stock issued and outstanding was converted into one share of common stock
Reverse stock split, conversion ratio		0.1
Interest expense								$ 1,659,000	$ 1,560,000		$ 30,400,000	20,708,000
Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount						$ 125,000,000	$ 125,000,000
Net proceeds from the debt issuance							$ 120,600,000
Interest rate (as a percent)						4.50%	4.50%						4.50%
Embedded conversion option						$ 53,800,000	$ 53,800,000
Underwriting discounts and commissions and offering expenses						4,400,000
Principal amount of convertible notes due 2020 converted into shares of common stock					$ 64,200,000
Conversion ratio, principal amount					$ 1,000	$ 1,000	$ 1,000
Conversion rate of common stock shares per $1,000 principal amount	23.5210		235.2112	136		160.0000
Common stock, shares issued \| shares				8,732,152	3,635,511					12,367,663
Value of additional shares issued for conversion					$ 27,700,000
Trading period					10 days
Increase to additional paid in capital pursuant to conversion										$ 101,000,000
Loss on extinguishment of debt										14,600,000
Reduction in additional paid-in capital attributable to embedded conversion option										$ 39,800,000
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be convertible						30 days
Convertibility of debt, closing price of stock test, percentage of stock price to conversion price for the notes that must be exceeded						130.00%
Number of consecutive business days immediately after any five consecutive trading day period during the note measurement period						5 days
Number of consecutive trading days before five consecutive business days during the note measurement period						5 days
Initial conversion price of shares (in dollars per share) \| $ / shares						$ 6.25	$ 6.25
Reverse stock split description											one-for-ten reverse stock split
Reverse stock split, conversion ratio	0.1
Deposited into escrow account								60,000,000			$ 60,000,000		$ 60,000,000
Interest expense								$ 1,700,000	$ 1,700,000		5,000,000	$ 21,100,000
Convertible Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be convertible						20 days
Convertible Notes [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Convertibility of debt, trading price of debt test, percentage of closing price of stock used in calculation						98.00%
Convertible Notes [Member] \| Transaction Costs Incurred With Third Parties [Member]
Debt Instrument [Line Items]
Reduction in additional paid-in capital											200,000
Convertible Notes [Member] \| Interest Expense [Member] \| Transaction Costs Incurred With Third Parties [Member]
Debt Instrument [Line Items]
Transaction costs related to conversion of convertible notes due 2020 incurred and paid											$ 200,000

Borrowings - Schedule of Future Minimum Payments under the Loans Payable (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt	$ 49,884	$ 216,861
Convertible Notes [Member]
Debt Instrument [Line Items]
2018	2,736
2019	2,736
2020 and thereafter	63,526
Loans payable, gross including contractual interest	68,998
Less interest	(8,207)
Less unamortized discount	(10,907)
Long-term debt	$ 49,884

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended			9 Months Ended
	Aug. 11, 2017 shares	Apr. 05, 2017 USD ($)	Feb. 29, 2016 shares	Sep. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 05, 2017 shares	Dec. 31, 2016 shares	Dec. 31, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Granted							2,098,000
Special cash dividend paid \| $		$ 140.0
Dividend payable date		May 26, 2017
Dividend payable, date of record		May 17, 2017
Incremental compensation expense \| $					$ 5.6
Reverse stock split description							Reverse Split, every ten shares of common stock issued and outstanding was converted into one share of common stock
Reverse stock split, conversion ratio	0.1
Common stock, shares issued	132,800,000			13,274,000			13,274,000		13,280,000	13,020,000
Common stock, shares outstanding	132,800,000			13,274,000			13,274,000		13,280,000	13,020,000
Common stock, shares authorized	200,000,000			20,000,000			20,000,000		20,000,000	20,000,000
Number of fractional shares issued									0
Preferred stock, shares issued				0			0		0	0
Preferred stock, shares outstanding				0			0		0	0
Weighted-average grant date fair value per share of stock options \| $ / shares				$ 7.68		$ 30.66	$ 4.06	$ 33.19
Aggregate intrinsic value of options exercised \| $				$ 0.0		$ 1.1	$ 2.3	$ 3.8
Unrecognized stock-based compensation expense related to nonvested stock awards \| $				$ 5.7			$ 5.7
Weighted average period over which unrecognized stock-based compensation expense is expected to be recognized							2 years 9 months 8 days
Stock Incentive Plan 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for grant (in shares)				300,000			300,000				300,000
Additional common stock available for issuance (in shares)			400,000
Number of Options, Granted				200,000		0	2,100,000	400,000
Stock Incentive Plan 2011 [Member] \| Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period							3 years

Stock-Based Compensation - Schedule of Assumptions Used to Calculate Fair Value of Options Granted to Employees (Detail) - Options to Purchase Common Stock [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility		67.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term		5 years 9 months 18 days
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.70%	1.10%	1.70%	1.10%
Expected volatility	64.00%		64.00%	67.00%
Expected term	5 years		5 years	5 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.80%	1.40%	2.10%	1.50%
Expected volatility	66.00%		68.00%	69.00%
Expected term	5 years 9 months 18 days		6 years 1 month 6 days	5 years 9 months 18 days

Stock-Based Compensation - Schedule of Recognized Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,580	$ 2,174	$ 11,110	$ 8,251
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense for employee awards	734	1,216	6,118	4,206
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense for employee awards	$ 846	$ 958	$ 4,992	$ 4,045

Stock-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Number of Options, Outstanding, Beginning balance \| shares	1,902
Number of Options, Granted \| shares	2,098
Number of Options, Exercised \| shares	(290)
Number of Options, Forfeited \| shares	(1,886)
Number of Options, Outstanding, Ending balance \| shares	1,824	1,902
Number of Options, Vested and expected to vest \| shares	1,822
Number of Options, Exercisable \| shares	1,159
Weighted-Average Exercise Price, Outstanding, Beginning balance \| $ / shares	$ 57.68
Weighted-Average Exercise Price, Granted \| $ / shares	23.77
Weighted-Average Exercise Price, Exercised \| $ / shares	21.74
Weighted-Average Exercise Price, Forfeited \| $ / shares	59.37
Weighted-Average Exercise Price, Outstanding, Ending balance \| $ / shares	22.65	$ 57.68
Weighted-Average Exercise Price, Vested and expected to vest \| $ / shares	22.64
Weighted-Average Exercise Price, Exercisable \| $ / shares	$ 26.71
Weighted-Average Remaining Contractual Term	6 years 2 months 16 days	5 years 11 months 19 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 2 months 16 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 4 months 2 days
Aggregate Intrinsic Value, Outstanding \| $	$ 1,187	$ 7,564
Aggregate Intrinsic Value, Vested and expected to vest \| $	1,187
Aggregate Intrinsic Value, Exercisable \| $	$ 969

Investment in Silver Creek - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Jul. 14, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Gain on deconsolidation		$ 10,848	$ 10,848
Silver Creek [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Ownership interest percentage held		43.00%	43.00%
Gain on deconsolidation		$ 10,800	$ 10,848
Investment at fair value	$ 11,400		$ 11,400
Silver Creek [Member] \| Minimum [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Ownership interest percentage held by parent and its de facto agents				50.00%
Silver Creek [Member] \| Maximum [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Ownership interest percentage held by parent		50.00%	50.00%

Investment in Silver Creek - Schedule of Gain on Deconsolidation (Detail) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Jul. 14, 2017	Sep. 30, 2017	Sep. 30, 2017
Minority Interest [Line Items]
Carrying value of non-controlling interest			$ (1,852)
Gain recognized on deconsolidation of Silver Creek		$ 10,848	10,848
Silver Creek [Member]
Minority Interest [Line Items]
Fair value of the Company's retained investment in Silver Creek	$ 11,400		11,400
Carrying value of non-controlling interest			(1,852)
Derecognition of Silver Creek's net liabilities			1,300
Gain recognized on deconsolidation of Silver Creek		$ 10,800	$ 10,848

Investment in Silver Creek - Schedule of Non-Controlling Interest in Subsidiary (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Minority Interest [Line Items]
Balance at the beginning of the period			$ (1,539)	$ 239
Net loss attributable to Silver Creek	$ 31	$ (207)	(1,160)	(600)
Balance at date of deconsolidation			(1,852)
Carrying value of non-controlling interest			1,852
Balance at the end of the period		$ (361)		$ (361)
Series C Preferred Stock [Member]
Minority Interest [Line Items]
Issuance of Silver Creek Series C preferred stock			$ 847

Subsequent Events - Additional Information (Detail) $ in Millions	Oct. 13, 2017 USD ($) $ / shares	Oct. 11, 2017 USD ($)	Oct. 06, 2017 USD ($) $ / shares	Oct. 16, 2017 USD ($)	Jul. 31, 2013 USD ($)
Convertible Notes [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 125.0
Subsequent Event [Member] \| Settlement Agreement [Member]
Subsequent Event [Line Items]
Name of plaintiff			Delaware
Attorneys’ fees and expenses to the plaintiff		$ 3.8
Subsequent Event [Member] \| Settlement Agreement [Member] \| Convertible Notes [Member]
Subsequent Event [Line Items]
Settlement agreement, cash paid			$ 32.5
Settlement amount paid per unit to plaintiff \| $ / shares			0.90
Amount held by plaintiff per unit \| $ / shares			1.00
Aggregate principal amount			$ 35.8
Subsequent Event [Member] \| Settlement Agreement Cash Tender Offer [Member]
Subsequent Event [Line Items]
Tender offer expiration date	Nov. 10, 2017
Subsequent Event [Member] \| Settlement Agreement Cash Tender Offer [Member] \| Convertible Notes [Member]
Subsequent Event [Line Items]
Remaining aggregate principal amount	$ 25.0
Offering amount of per unit debt instrument issued at discount \| $ / shares	900
Principal amount of per unit debt instrument issued at discount \| $ / shares	1,000
Subsequent Event [Member] \| Asset Sale Agreement [Member] \| Ipsen [Member]
Subsequent Event [Line Items]
Working capital adjustment receivable				$ 4.9