Merrimack Pharmaceuticals (MACK) 10-Q 7 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	MACK
Title of 12(b) Security	Common stock, $0.01 par value
Security Exchange Name	NASDAQ
Entity Registrant Name	MERRIMACK PHARMACEUTICALS INC
Entity Central Index Key	0001274792
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-35409
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3210530
Entity Address, Address Line One	One Broadway
Entity Address, Address Line Two	14th Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	441-1000
Entity Common Stock, Shares Outstanding		13,380,243
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 15,735	$ 16,580
Prepaid expenses and other current assets	3,631	2,112
Total current assets	19,366	18,692
Other assets	315	1,390
Total assets	19,681	20,082
Current liabilities:
Accounts payable, accrued expenses and other	2,279	2,714
Other current liability	56	56
Total current liabilities	2,335	2,770
Total liabilities	2,335	2,770
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value: 10,000 shares authorized at June 30, 2020 and December 31, 2019; no shares issued or outstanding at June 30, 2020 or December 31, 2019
Common stock, $0.01 par value: 30,000 shares authorized at June 30, 2020 and December 31, 2019; 13,380 shares issued and outstanding at June 30, 2020 and December 31, 2019	1,334	1,334
Additional paid-in capital	557,535	556,587
Accumulated deficit	(541,523)	(540,609)
Total stockholders’ equity	17,346	17,312
Total liabilities and stockholders’ equity	$ 19,681	$ 20,082

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
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	30,000,000	30,000,000
Common stock, shares issued	13,380,000	13,380,000
Common stock, shares outstanding	13,380,000	13,380,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development expenses		$ 4,739		$ 11,100
General and administrative expenses	$ 1,184	5,929	$ 3,119	9,612
Gain on sale of assets		(1,410)	(2,139)	(1,410)
Total operating expenses	1,184	9,258	980	19,302
Loss from operations	(1,184)	(9,258)	(980)	(19,302)
Other income and expenses:
Interest income	3	207	48	572
Interest expense		(1,049)		(1,527)
Other income, net	18	670	18	369
Total other income and expenses	21	(172)	66	(586)
Net loss	(1,163)	(9,430)	(914)	(19,888)
Other comprehensive income:
Unrealized gain on marketable securities				9
Other comprehensive income				9
Comprehensive loss	$ (1,163)	$ (9,430)	$ (914)	$ (19,879)
Net loss per common share - basic and diluted	$ (0.09)	$ (0.71)	$ (0.07)	$ (1.49)
Weighted-average common shares used to compute basic and diluted net loss per common share	13,380	13,344	13,380	13,343

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2018	$ 58,819	$ 1,334	$ 580,771	$ (9)	$ (523,277)
Balance (in shares) at Dec. 31, 2018		13,343
Stock-based compensation	594		594
Unrealized gain on marketable securities	9			9
Net income (loss)	(10,458)				(10,458)
Balance at Mar. 31, 2019	48,964	$ 1,334	581,365		(533,735)
Balance (in shares) at Mar. 31, 2019		13,343
Balance at Dec. 31, 2018	58,819	$ 1,334	580,771	$ (9)	(523,277)
Balance (in shares) at Dec. 31, 2018		13,343
Unrealized gain on marketable securities	9
Net income (loss)	(19,888)
Balance at Jun. 30, 2019	40,044	$ 1,334	581,875		(543,165)
Balance (in shares) at Jun. 30, 2019		13,349
Balance at Mar. 31, 2019	48,964	$ 1,334	581,365		(533,735)
Balance (in shares) at Mar. 31, 2019		13,343
Stock-based compensation	487		487
Exercise of stock options	23		23
Exercise of stock options (in shares)		6
Net income (loss)	(9,430)				(9,430)
Balance at Jun. 30, 2019	40,044	$ 1,334	581,875		(543,165)
Balance (in shares) at Jun. 30, 2019		13,349
Balance at Dec. 31, 2019	17,312	$ 1,334	556,587		(540,609)
Balance (in shares) at Dec. 31, 2019		13,380
Stock-based compensation	484		484
Net income (loss)	249				249
Balance at Mar. 31, 2020	18,045	$ 1,334	557,071		(540,360)
Balance (in shares) at Mar. 31, 2020		13,380
Balance at Dec. 31, 2019	17,312	$ 1,334	556,587		(540,609)
Balance (in shares) at Dec. 31, 2019		13,380
Net income (loss)	(914)
Balance at Jun. 30, 2020	17,346	$ 1,334	557,535		(541,523)
Balance (in shares) at Jun. 30, 2020		13,380
Balance at Mar. 31, 2020	18,045	$ 1,334	557,071		(540,360)
Balance (in shares) at Mar. 31, 2020		13,380
Stock-based compensation	464		464
Net income (loss)	(1,163)				(1,163)
Balance at Jun. 30, 2020	$ 17,346	$ 1,334	$ 557,535		$ (541,523)
Balance (in shares) at Jun. 30, 2020		13,380

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net income (loss)	$ (914)	$ (19,888)
Adjustments to reconcile net loss to net cash used in operating activities
Non-cash interest expense		141
Loss on extinguishment of debt		971
Depreciation and amortization expense		2,228
Gain on sale of equipment		(1,984)
Gain on sale of in progress research and development	(2,139)
Amortization and accretion on marketable securities		(279)
Stock-based compensation expense	948	1,081
Gain on equity method investment		(372)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(444)	2,432
Accounts payable, accrued expenses and other	(435)	(9,855)
Net cash used in operating activities	(2,984)	(25,525)
Cash flows from investing activities
Proceeds from sale of property and equipment		2,025
Proceeds from sale of in progress research and development	2,139
Proceeds from sale of equity method investment		7,800
Proceeds from maturities and sales of marketable securities		48,500
Net cash provided by investing activities	2,139	58,325
Cash flows from financing activities
Proceeds from exercise of stock options		23
Repayment of debt		(15,000)
Payment of debt extinguishment costs		(985)
Net cash used in financing activities		(15,962)
Net (decrease) increase in cash, cash equivalents and restricted cash	(845)	16,838
Cash, cash equivalents and restricted cash, beginning of period	16,580	20,663
Cash, cash equivalents and restricted cash, end of period	$ 15,735	37,501
Supplemental disclosure of cash flows
Cash paid for interest		$ 1,399

Nature of the Business

Nature of the Business	6 Months Ended
	Jun. 30, 2020
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 eligible to receive up to $450.0 million in contingent milestone payments related to its sale of ONIVYDE ® and up to $54.5 million in contingent milestone payments related to its sale of MM-121 and MM-111 to Elevation Oncology, Inc. (formerly known as 14ner Oncology, Inc.), or Elevation, in July 2019 The $450.0 million in contingent milestone payments resulting from the Ipsen sale consist of: • $225.0 million upon approval by the U.S. Food and Drug Administration (“FDA”) of ONIVYDE for the first-line treatment of metastatic adenocarcinoma of the pancreas, subject to certain conditions; • $150.0 million upon approval by the FDA of ONIVYDE for the treatment of small-cell lung cancer after failure of first-line chemotherapy; and • $75.0 million upon approval by the FDA of ONIVYDE for an additional indication unrelated to those described above. On April 15, 2019, the Company repaid in full all principal, accrued and unpaid interest, fees, costs and expenses under its Loan and Security Agreement (the “Loan Agreement”) with Hercules Capital, Inc. (“Hercules”) in an aggregate amount equal to $16.0 million. In May 2019, the Company monetized certain assets to strengthen its cash position. This includes the sale of its entire equity position in Silver Creek Pharmaceuticals, Inc. (“Silver Creek”), resulting in $7.8 million in cash, and the sale of laboratory equipment from its research and development operations, resulting in approximately $1.4 million in cash. On May 30, 2019, the Company announced the completion of its review of strategic alternatives, following which the Company’s board of directors (the “Board”) implemented a series of measures designed to extend the Company’s cash runway and preserve its ability to capture the potential milestone payments resulting from the Ipsen sale. In connection with that announcement, the Company discontinued the discovery efforts on its remaining preclinical programs: MM-401, an agonistic antibody targeting a novel immuno-oncology target, TNFR2; and MM-201, a highly stabilized agonist-Fc fusion protein targeting death receptors 4 and 5. The Company is seeking potential acquirers for its remaining preclinical and clinical assets. The Company’s termination of its executive management team and all other employees was substantially completed by June 28, 2019 and fully completed by July 12, 2019. As of July 12, 2019, the Company does not have any employees. The Company has engaged external consultants to run the day-to-day operations of the Company. The Company has also entered into consulting agreements with certain former members of its executive management team who are supporting the Company’s relationship with current partners, assisting with the potential sale of remaining preclinical and clinical assets, and assisting with certain legal and regulatory matters and the continued wind-down of operations. On July 12, 2019, the Company completed the sale to Elevation Oncology, Inc. (formerly known as 14ner Oncology, Inc.) (“Elevation”) of its anti-HER3 antibody programs, MM-121 (Seribantumab) and MM-111 (the “Elevation sale”). In connection with the Elevation sale, the Company received an upfront cash payment of $3.5 million. The Company is also eligible to receive up to $54.5 million in additional potential development, regulatory approval and commercial-based milestone payments, consisting of: • $3.0 million for achievement of the primary endpoint in the first registrational clinical study of either MM-121 or MM-111; • Up to $16.5 million in total payments for the achievement of various regulatory approval and reimbursement-based milestones in the United States, Europe and Japan; and • Up to $35.0 million in total payments for achieving various cumulative worldwide net sales targets between $100.0 million and $300.0 million for MM-121 and MM-111. On July 25, 2019, the Board authorized and declared a special cash dividend of $ 20.0 million to holders of the Company's common stock, which was payable on September 5, 2019 to stockholders of record as of the close of business on August 28, 2019 . On November 29, 2019, the Company received the remaining $5.0 million milestone payment that became payable for the ex-U.S. development and commercialization of ONIVYDE pursuant to a license and collaboration agreement (the “Servier Agreement”) between Ipsen and Les Laboratoires Servier SAS (as assignee from Shire plc). On December 3, 2019, the Board authorized and declared a special cash dividend of $6.7 million to holders of the Company's common stock, which was payable on December 23, 2019 to stockholders of record as of the close of business on December 16, 2019. On March 27, 2020, the Company entered into an Asset Purchase Agreement (the “Celator Agreement”) with Celator Pharmaceuticals, Inc. (“Celator”), pursuant to which Celator agreed to purchase certain assets relating to certain of the Company’s preclinical nanoliposome programs (the “Celator sale”). The Company and Celator completed the Celator sale simultaneously with the execution of the Celator Agreement. Under the terms of the Celator Agreement, Celator paid to the Company a cash payment of $2.3 million and reimbursed the Company for $0.2 million related to certain specified expenses. The Company incurred $0.4 million expenses related to the Celator sale as of June 30, 2020. The Company is subject to risks and uncertainties common to companies in the biopharmaceutical industry, including, among other things, development by competitors of new technological innovations, protection of proprietary technology and compliance with government regulations, approval by the FDA and other foreign health agencies to approve any pharmaceutical under development, obtaining insurance reimbursement for any drug if and when approved by regulators, and its ability to secure additional capital to fund operations. None of the Company’s product candidates are approved for any indication by the FDA or any other regulatory agency. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies, among others. In addition, the Company is dependent upon the services of its external consultants for the operation of the Company. The Company’s business strategy depends substantially upon its ability to receive future milestone payments from Ipsen and Elevation. Any failure to achieve such milestones or a perception that the milestones may not be achieved will materially and adversely affect the Company and the value of its common stock. The recent COVID-19 outbreak has created significant volatility and economic disruption and the impact on the Company’s future consolidated results of operations is uncertain In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern will allow the Company to continue its operations into 2027, when the Company estimates the longest-term potential Ipsen milestone may be achieved. The continued viability of the Company beyond that point is dependent on its ability to realize milestone payments from its licensed product candidates, raise additional capital to finance its operations or to reduce operating expenses. There can be no assurance that the Company will be successful in receiving future milestone payments or able to obtain sufficient capital to cover its costs on acceptable terms, if at all. The Company expects that it would seek to finance any future cash needs through a combination of divestitures of its product candidates or other assets, equity offerings and debt financings. There can be no assurance as to the timing, terms or consummation of any divestiture or financing, and the terms of any such financing may adversely affect the holdings or the rights of the Company’s stockholders or require the Company to relinquish rights to certain of its revenue streams or product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements reflect the operations of Merrimack Pharmaceuticals, Inc. and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated. The condensed consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accounting policies followed in the preparation of the interim condensed consolidated financial statements are consistent in all material respects with those presented in Note 1 to the financial statements included in the Company’s Annual Report on Form 1 0-K for the year ended December 31, 2019 . Consolidation The accompanying condensed consolidated financial statements reflect Merrimack Pharmaceuticals, Inc. and its wholly owned subsidiaries. Unaudited Interim Financial Information The condensed consolidated balance sheet as of December 31, 2019 was derived from audited financial statements, but does not include all disclosures required by GAAP. The condensed consolidated balance sheet as of June 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed consolidated statements of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and the condensed consolidated statements of cash flows for the six months ended June 30, 2020 and 2019 are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2020, the results of its operations for the three and six months ended June 30, 2020 and 2019, its statements of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and its statements of cash flows for the six months ended June 30, 2020 and 2019. The financial data and other information disclosed in the notes related to the three and six months ended June 30, 2020 and 2019 are unaudited. The results for the three and six months ended June 30, 2020 and 2019 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. The unaudited interim financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements and the notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on March 12, 2020. Condensed Consolidated Statements of Cash Flows The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows: (in thousands) June 30, 2020 June 30, 2019 Cash and cash equivalents $ 15,735 $ 36,917 Restricted cash (short-term) — 584 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 15,735 $ 37,501 Restricted cash on the statement of financial position for 2019 primarily represents amounts pledged as collateral for operating lease obligations as contractually required. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates, assumptions and judgments reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments The following tables show assets measured at fair value on a recurring basis as of June 30, 2020 and December 31, 2019: June 30, 2020 (in thousands) Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 14,442 $ — $ — Totals $ 14,442 $ — $ — December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 16,375 $ — $ — Totals $ 16,375 $ — $ — The Company’s cash, prepaid expenses and other current assets, accounts payable and accrued expenses are recorded at cost, which approximates fair value due to their short-term nature.

Accounts Payable, Accrued Expen

Accounts Payable, Accrued Expenses and Other	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accounts Payable, Accrued Expenses and Other	4. Accounts Payable, Accrued Expenses and Other Accounts payable, accrued expenses and other as of June 30, 2020 and December 31, 2019 consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Accounts payable $ 208 $ 271 Accrued goods and services 216 372 Accrued clinical trial costs 155 320 Accrued drug purchase costs 371 371 Accrued restructuring expenses 15 66 Deferred tax incentives 1,314 1,314 Total accounts payable, accrued expenses and other $ 2,279 $ 2,714

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	5. Stock-Based Compensation The Company’s 2011 Stock Incentive 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. There were no options granted during the three and six months ended June 30, 2020. At June 30, 2020, there were 1.5 million shares remaining available for grant under the 2011 Plan. The Company recognized stock-based compensation expense during the three and six months ended June 30, 2020 and 2019 as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2020 2019 2020 2019 Research and development expense $ — $ 40 $ — $ 223 General and administrative expense 464 447 948 858 Total stock-based compensation expense $ 464 $ 487 $ 948 $ 1,081

Net Loss Per Common Share

Net Loss Per Common Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Common Share	6. Net Loss Per Common Share Basic net loss per share is calculated by dividing the net loss attributable to the Company by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing the net loss attributable to the Company 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. Outstanding stock options were not included in the diluted net loss per share calculation because the options were out of the money or to do so would have been antidilutive (i.e., the total proceeds upon exercise would have exceeded the market value of the underlying common shares). 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. Stock options are excluded from the calculation of diluted loss per share because the net loss for the three and six months ended June 30, 2020 and 2019 causes such securities to be anti-dilutive. Outstanding options excluded from the calculation of diluted loss per share for the three and six months ended June 30, 2020 and 2019 are shown in the chart below: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2020 2019 2020 2019 Outstanding options to purchase common stock 1,877 1,573 1,877 1,573

Restructuring Activities

Restructuring Activities	6 Months Ended
	Jun. 30, 2020
Restructuring And Related Activities [Abstract]
Restructuring Activities	7. Restructuring Activities On November 7, 2018, the Company announced that it was implementing a reduction in headcount as part of a corporate restructuring. The accrued balance as of December 31, 2019 approximated to $0.1 million. No additional restructuring expenses were recognized during the three and six months ended June 30, 2020. the Company recognized additional restructuring expenses of $4.6 million and $4.9 million, respectively, consisting of one-time employee termination benefits of $1.8 million and $2.0 million, respectively, recorded in research and development expense and $2.8 million and $2.9 million, respectively, recorded in general and administrative expense. 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 Company paid and adjusted approximately less than $0.1 million and $0.1 million of these restructuring expenses during the three and six months ended June 30, 2020, respectively. The remaining payments of less than $0.1 million will be paid during the three months ended September 30, 2020. During the three and six months ended June 30, 2019, the Company paid approximately $3.8 million and $4.8 million of these restructuring expenses, respectively. The following table summarizes the charges related to the restructuring activities as of June 30, 2020 and 2019: (in thousands) Accrued Restructuring Expenses at December 31, 2019 Expenses Less: Payments and Adjustments Accrued Restructuring Expenses at June 30, 2020 Severance, benefits and related costs due to workforce reduction $ 66 $ — $ (51 ) $ 15 Totals $ 66 $ — $ (51 ) $ 15 (in thousands) Accrued Restructuring Expenses at December 31, 2018 Expenses Less: Payments Accrued Restructuring Expenses at June 30, 2019 Severance, benefits and related costs due to workforce reduction $ 921 $ 4,890 $ (4,755 ) $ 1,056 Totals $ 921 $ 4,890 $ (4,755 ) $ 1,056

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2020
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Pronouncements	8. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed above, the Company does not believe that the adoption of recently issued standards has or may have a material impact on the Company’s condensed consolidated financial statements or disclosures.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements reflect the operations of Merrimack Pharmaceuticals, Inc. and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated. The condensed consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accounting policies followed in the preparation of the interim condensed consolidated financial statements are consistent in all material respects with those presented in Note 1 to the financial statements included in the Company’s Annual Report on Form 1 0-K for the year ended December 31, 2019 .
Consolidation	Consolidation The accompanying condensed consolidated financial statements reflect Merrimack Pharmaceuticals, Inc. and its wholly owned subsidiaries.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated balance sheet as of December 31, 2019 was derived from audited financial statements, but does not include all disclosures required by GAAP. The condensed consolidated balance sheet as of June 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed consolidated statements of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and the condensed consolidated statements of cash flows for the six months ended June 30, 2020 and 2019 are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2020, the results of its operations for the three and six months ended June 30, 2020 and 2019, its statements of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and its statements of cash flows for the six months ended June 30, 2020 and 2019. The financial data and other information disclosed in the notes related to the three and six months ended June 30, 2020 and 2019 are unaudited. The results for the three and six months ended June 30, 2020 and 2019 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. The unaudited interim financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements and the notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on March 12, 2020.
Condensed Consolidated Statements of Cash Flows	Condensed Consolidated Statements of Cash Flows The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows: (in thousands) June 30, 2020 June 30, 2019 Cash and cash equivalents $ 15,735 $ 36,917 Restricted cash (short-term) — 584 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 15,735 $ 37,501 Restricted cash on the statement of financial position for 2019 primarily represents amounts pledged as collateral for operating lease obligations as contractually required.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates, assumptions and judgments reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.
Recent Accounting Pronouncements	In June 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed above, the Company does not believe that the adoption of recently issued standards has or may have a material impact on the Company’s condensed consolidated financial statements or disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows: (in thousands) June 30, 2020 June 30, 2019 Cash and cash equivalents $ 15,735 $ 36,917 Restricted cash (short-term) — 584 Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows $ 15,735 $ 37,501

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Summary of Assets Measured at Fair Value on a Recurring Basis	The following tables show assets measured at fair value on a recurring basis as of June 30, 2020 and December 31, 2019: June 30, 2020 (in thousands) Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 14,442 $ — $ — Totals $ 14,442 $ — $ — December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 16,375 $ — $ — Totals $ 16,375 $ — $ —

Accounts Payable, Accrued Exp_2

Accounts Payable, Accrued Expenses and Other (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accounts Payable, Accrued Expenses and Other	Accounts payable, accrued expenses and other as of June 30, 2020 and December 31, 2019 consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Accounts payable $ 208 $ 271 Accrued goods and services 216 372 Accrued clinical trial costs 155 320 Accrued drug purchase costs 371 371 Accrued restructuring expenses 15 66 Deferred tax incentives 1,314 1,314 Total accounts payable, accrued expenses and other $ 2,279 $ 2,714

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Recognized Stock-Based Compensation Expense	The Company recognized stock-based compensation expense during the three and six months ended June 30, 2020 and 2019 as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2020 2019 2020 2019 Research and development expense $ — $ 40 $ — $ 223 General and administrative expense 464 447 948 858 Total stock-based compensation expense $ 464 $ 487 $ 948 $ 1,081

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Outstanding Options Excluded from Computation of Diluted Loss Per Share	Outstanding options excluded from the calculation of diluted loss per share for the three and six months ended June 30, 2020 and 2019 are shown in the chart below: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2020 2019 2020 2019 Outstanding options to purchase common stock 1,877 1,573 1,877 1,573

Restructuring Activities (Table

Restructuring Activities (Tables)	6 Months Ended
	Jun. 30, 2020
Restructuring And Related Activities [Abstract]
Summary of Charges Related to Restructuring Activities	The following table summarizes the charges related to the restructuring activities as of June 30, 2020 and 2019: (in thousands) Accrued Restructuring Expenses at December 31, 2019 Expenses Less: Payments and Adjustments Accrued Restructuring Expenses at June 30, 2020 Severance, benefits and related costs due to workforce reduction $ 66 $ — $ (51 ) $ 15 Totals $ 66 $ — $ (51 ) $ 15 (in thousands) Accrued Restructuring Expenses at December 31, 2018 Expenses Less: Payments Accrued Restructuring Expenses at June 30, 2019 Severance, benefits and related costs due to workforce reduction $ 921 $ 4,890 $ (4,755 ) $ 1,056 Totals $ 921 $ 4,890 $ (4,755 ) $ 1,056

Nature of the Business - Additi

Nature of the Business - Additional Information (Detail) - USD ($)

Mar. 27, 2020

Dec. 03, 2019

Jul. 25, 2019

Jul. 12, 2019

May 31, 2019

Jun. 30, 2020

Jun. 30, 2019

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2019

Jul. 31, 2019

Apr. 15, 2019

Apr. 30, 2017

Apr. 03, 2017

Summary Of Significant Accounting Policies [Line Items]

Proceeds from maturities and sales of marketable securities

$ 48,500,000

Proceeds on sale of property and equipment

2,025,000

Special cash dividend paid

$ 6,700,000

$ 20,000,000

Dividend payable date

Dec. 23, 2019

Sep. 5, 2019

Dividend payable, date of record

Dec. 16, 2019

Aug. 28, 2019

Accumulated deficit

$ 541,523,000

$ 541,523,000

$ 540,609,000

Net loss

1,163,000

$ 9,430,000

914,000

19,888,000

Cash used in operating activities

2,984,000

$ 25,525,000

Cash, cash equivalents and marketable securities

$ 15,700,000

$ 15,700,000

Silver Creek Pharmaceuticals, Inc. [Member]

Summary Of Significant Accounting Policies [Line Items]

Proceeds from maturities and sales of marketable securities

$ 7,800,000

Silver Creek Pharmaceuticals, Inc. [Member] | Laboratory Equipment [Member]

Summary Of Significant Accounting Policies [Line Items]

Proceeds on sale of property and equipment

$ 1,400,000

Celator Pharmaceuticals Inc [Member]

Summary Of Significant Accounting Policies [Line Items]

Cash payment received

$ 2,300,000

Reimbursement of expenses

200,000

Transaction expenses

$ 400,000

Loan Agreement [Member] | Hercules Capital Inc [Member] | Term Loan [Member]

Summary Of Significant Accounting Policies [Line Items]

Payoff Amount

$ 16,000,000

IpsenSAMember | First Line Treatment of Metastatic Adenocarcinoma of Pancreas [Member]

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

$ 225,000,000

IpsenSAMember | After Failure of First Line Chemotherapy [Member]

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

150,000,000

IpsenSAMember | Additional Indication [Member]

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

75,000,000

IpsenSAMember | Ongoing Multi Part Clinical

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

$ 5,000,000

IpsenSAMember | Asset Sale Agreement [Member]

Summary Of Significant Accounting Policies [Line Items]

Additional payments receivable on achievement of certain milestone events

$ 450,000,000

IpsenSAMember | Asset Sale Agreement [Member] | Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

$ 450,000,000

14ner Sale [Member]

Summary Of Significant Accounting Policies [Line Items]

Upfront cash payment received

$ 3,500,000

14ner Sale [Member] | Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

Additional payments receivable on achievement of certain milestone events

54,500,000

14ner Sale [Member] | Maximum [Member] | Achievement of the Primary Endpoint in the First Registrational Clinical Study of Either MM-121 or MM-111 [Member]

Summary Of Significant Accounting Policies [Line Items]

Additional payments receivable on achievement of certain milestone events

3,000,000

14ner Sale [Member] | Maximum [Member] | Achievement of Various Regulatory Approval and Reimbursement-Based Milestones in the United States, Europe and Japan [Member]

Summary Of Significant Accounting Policies [Line Items]

Additional payments receivable on achievement of certain milestone events

16,500,000

14ner Sale [Member] | Maximum [Member] | Achievement Various Cumulative Worldwide Net Sales Targets Between $100.0 million and $300.0 million for MM-121 and MM-111 [Member]

Summary Of Significant Accounting Policies [Line Items]

Additional payments receivable on achievement of certain milestone events

35,000,000

Cumulative worldwide net sales target

300,000,000

14ner Sale [Member] | Minimum [Member] | Achievement Various Cumulative Worldwide Net Sales Targets Between $100.0 million and $300.0 million for MM-121 and MM-111 [Member]

Summary Of Significant Accounting Policies [Line Items]

Cumulative worldwide net sales target

$ 100,000,000

14ner Sale [Member] | Asset Sale Agreement [Member] | Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

Contingent milestone payments receivable

$ 54,500,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 15,735	$ 16,580	$ 36,917
Restricted cash (short-term)			584
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows	$ 15,735	$ 16,580	$ 37,501	$ 20,663

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Assets Measured at Fair Value on a Recurring Basis (Detail) - Recurring Basis [Member] - Level 1 [Member] - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 14,442	$ 16,375
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 14,442	$ 16,375

Accounts Payable, Accrued Exp_3

Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 208	$ 271
Accrued goods and services	216	372
Accrued clinical trial costs	155	320
Accrued drug purchase costs	371	371
Accrued restructuring expenses	15	66	$ 1,056	$ 921
Deferred tax incentives	1,314	1,314
Total accounts payable, accrued expenses and other	$ 2,279	$ 2,714

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - Stock Incentive Plan 2011 [Member]	3 Months Ended	6 Months Ended
	Jun. 30, 2020shares	Jun. 30, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for grant (in shares)	1,500,000	1,500,000
Number of Options, Granted	0	0

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Recognized Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 464	$ 487	$ 948	$ 1,081
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		40		223
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	$ 464	$ 447	$ 948	$ 858

Net Loss Per Common Share - Sch

Net Loss Per Common Share - Schedule of Outstanding Options Excluded from Computation of Diluted Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Outstanding Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted loss per share	1,877	1,573	1,877	1,573

Restructuring Activities - Addi

Restructuring Activities - Additional Information (Detail) - USD ($)	3 Months Ended			6 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Accrued restructuring expenses		$ 15,000	$ 1,056,000	$ 15,000	$ 1,056,000	$ 66,000	$ 921,000
Restructuring expenses		0		0	4,890,000
Payments for restructuring			3,800,000		4,755,000
Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Payments for restructuring		$ 100,000		$ 100,000
Scenario Forecast [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Payments for restructuring	$ 100,000
One-time Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses			4,600,000		4,900,000
One-time Termination Benefits [Member] | Research and Development Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses			1,800,000		2,000,000
One-time Termination Benefits [Member] | General and Administrative Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses			$ 2,800,000		$ 2,900,000
November 2018 Corporate Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring activity, announcement date				Nov. 7, 2018

Restructuring Activities - Summ

Restructuring Activities - Summary of Charges Related to Restructuring Activities (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost And Reserve [Line Items]
Accrued Restructuring Expenses			$ 66,000	$ 921,000
Expenses	$ 0		0	4,890,000
Less: Payments and Adjustments			(51,000)
Less: Payments		$ (3,800,000)		(4,755,000)
Accrued Restructuring Expenses	15,000	1,056,000	15,000	1,056,000
Severance Benefits and Related Costs Due to Workforce Reduction [Member]
Restructuring Cost And Reserve [Line Items]
Accrued Restructuring Expenses			66,000	921,000
Expenses				4,890,000
Less: Payments and Adjustments			(51,000)
Less: Payments				(4,755,000)
Accrued Restructuring Expenses	$ 15,000	$ 1,056,000	$ 15,000	$ 1,056,000