Document and Entity Information	3 Months Ended
Document and Entity Information	Mar. 31, 2012	Apr. 30, 2012
Document and Entity Information
Entity Registrant Name	MERRIMACK PHARMACEUTICALS INC
Entity Central Index Key	0001274792
Document Type	10-Q
Document Period End Date	Mar. 31, 2012
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		93,299,961
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1

Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 30,555	$ 50,454
Restricted cash	100
Accounts receivable	5,980	7,426
Deferred financing costs	2,631	1,946
Prepaid expenses and other current assets	6,526	5,763
Total current assets	45,792	65,589
Restricted cash	381	381
Property and equipment, net	5,232	6,206
Other assets	23	23
Intangible assets, net	2,405	2,485
In-process research and development	7,010	7,010
Goodwill	3,605	3,605
Total assets	64,448	85,299
Current liabilities:
Accounts payable	2,599	4,656
Accrued expenses and other	13,061	12,855
Capital lease obligations	10	48
Deferred revenue	8,245	7,712
Deferred lease benefit	135	125
Deferred tax incentives	755	755
Total current liabilities	24,805	26,151
Deferred revenues	80,862	78,033
Deferred lease benefits	231	23
Deferred tax incentives	1,199	1,267
Convertible preferred stock warrants	957	1,516
Total liabilities	108,054	106,990
Commitments and contingencies (Note 10)
Convertible preferred stock	268,225	268,225
Non-controlling interest	456	574
Stockholders' deficit:
Common stock, 138,500 and 200,000 authorized $0.01 par value shares at December 31, 2011 and March 31, 2012, respectively, 11,834 and 11,907 issued and outstanding at December 31, 2011 and March 31, 2012, respectively	119	118
Additional paid-in capital	61,717	60,231
Accumulated deficit	(374,123)	(350,839)
Total stockholders' deficit	(312,287)	(290,490)
Total liabilities, convertible preferred stock, non-controlling interest and stockholders' deficit	$ 64,448	$ 85,299

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheets
Common stock, authorized shares	200,000	138,500
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued shares	11,907	11,834
Common stock, outstanding shares	11,907	11,834

Total number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Shares outstanding equals shares issued minus shares held in treasury and other adjustments, if any.

+ References+ Details

Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Collaboration revenues	$ 11,344	$ 6,461
Operating expenses
Research and development	31,651	18,001
General and administrative	3,728	3,101
Total operating expenses	35,379	21,102
Loss from operations	(24,035)	(14,641)
Other income and expenses
Interest income	9	14
Interest expense	(1)	(6)
Other, net	625	1,098
Net loss	(23,402)	(13,535)
Less net loss attributable to non-controlling interest	(118)	(78)
Net loss attributable to Merrimack Pharmaceuticals, Inc.	$ (23,284)	$ (13,457)
Net loss per share available to common stockholders-basic (in dollars per share)	$ (2.14)	$ (1.35)
Net loss per share available to common stockholders-diluted (in dollars per share)	$ (2.14)	$ (1.35)
Weighted-average common shares used in computing net loss per share available to common stockholders-basic (in shares)	11,846	11,106
Weighted-average common shares used in computing net loss per share available to common stockholders-diluted (in shares)	11,846	11,106

Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities
Net loss	$ (23,402)	$ (13,535)
Adjustments to reconcile net loss to net cash used in operating activities
Loss (gain) on mark-to-market on convertible preferred stock warrants	(559)	716
Amortization of deferred lease benefits and tax incentives	(179)	(167)
Depreciation and amortization	1,380	1,316
Stock-based compensation	1,339	1,020
Changes in operating assets and liabilities
Accounts receivable	1,446	(4,873)
Prepaid expenses and other current assets	(763)	(1,324)
Accounts payable	(2,057)	(317)
Accrued expenses and other	(299)	219
Deferred revenues	3,362	5,782
Deferred lease benefits and tax incentive	329	1,212
Other assets and liabilities, net		7
Net cash used in operating activities	(19,403)	(9,944)
Cash flows from investing activities
Purchase of property and equipment	(326)	(563)
Other investing activities, net	(100)	2
Net cash used in investing activities	(426)	(561)
Cash flows from financing activities
Proceeds from issuance of common stock	148	48
Proceeds received in advance of Series G issuance		12,508
Deferred financing costs	(180)
Principal payment on capital lease obligations	(38)	(169)
Net cash provided by (used in) financing activities	(70)	12,387
Net increase (decrease) in cash and cash equivalents	(19,899)	1,882
Cash and cash equivalents, beginning of period	50,454	30,713
Cash and cash equivalents, end of period	30,555	32,595
Non cash investing and financing activities
Deferred financing costs included in ending accrued expenses	505
Supplemental disclosure of cash flows
Cash paid for interest		$ 6

Nature of the Business

3 Months Ended

Mar. 31, 2012

Nature of the Business

Nature of the Business

1. Nature of the Business

Merrimack Pharmaceuticals, Inc. (the “Company”) is a biopharmaceutical company discovering, developing and preparing to commercialize innovative medicines consisting of novel therapeutics paired with companion diagnostics. The Company has five targeted therapeutic oncology candidates in clinical development (MM-398, MM-121, MM-111, MM-302 and MM-151), multiple product candidates in preclinical development and a discovery effort advancing additional candidate medicines. The Company uses its interdisciplinary Network Biology approach in drug discovery and development. The Company is incorporated in the State of Delaware.

The Company is subject to risks and uncertainties common to companies in the biopharmaceutical industry, including, but not limited to, its ability to secure additional capital to fund operations, 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 additional 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. However, the Company has incurred significant losses and does not have commercial operations underway. As of March 31, 2012, the Company had cash and cash equivalents of $30,555,000. In April 2012, the Company closed the initial public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company sold an aggregate of 15,042,459 shares of common stock under the registration statement at a public offering price of $7.00 per share, including 742,459 shares pursuant to the exercise by the underwriters of an over-allotment option. Net proceeds were approximately $100.5 million, after deducting underwriting discounts and commissions but prior to the payment of remaining offering expenses payable by the Company and accrued dividends on the Company’s Series B convertible preferred stock. The Company expects its existing cash and cash equivalents on hand as of March 31, 2012, together with the net proceeds from the initial public offering, to be sufficient to fund operations into the second half of 2013.

The Company may seek additional funding through public or private financings, or through existing or new collaboration arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into additional collaborative arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Arrangements with collaborators or others may require the Company to relinquish rights to certain of its technologies or product candidates. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs or commercialization efforts, which could adversely affect its business prospects.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2012

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Significant accounting policies followed by the Company in the preparation of its condensed consolidated financial statements are as follows:

Basis of Presentation

The accompanying condensed consolidated financial statements as of March 31, 2012, and for the three months ended March 31, 2011 and 2012, 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 Current Report on Form 8-K filed with the SEC on April 27, 2012.

The information presented in the condensed consolidated financial statements and related notes as of March 31, 2012, and for the three months ended March 31, 2011 and 2012, is unaudited. The December 31, 2011 condensed consolidated balance sheet included herein was 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 months ended March 31, 2012 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2012, or any future period.

Principles of Consolidation

These condensed consolidated financial statements include the accounts of the Company, its wholly owned subsidiary Hermes BioSciences, Inc., which was merged with and into the Company during 2011, its wholly owned subsidiary Merrimack Pharmaceuticals (Bermuda) Ltd., which was incorporated during 2011, and its 74% majority owned subsidiary Silver Creek Pharmaceuticals, Inc. (“Silver Creek”). All intercompany transactions and balances have been eliminated in consolidation.

There were no changes to the Company’s ownership of Silver Creek during the three months ended March 31, 2011 and 2012. The Company’s consolidated financial statement activity related to Silver Creek during these periods is as follows:

(in thousands)	Non-Controlling Interest
Balance at December 31, 2010	$	1,027
Net loss attributable to Silver Creek	(78		)
Balance at March 31, 2011	$	949

	Non-Controlling Interest
Balance at December 31, 2011	$	574
Net loss attributable to Silver Creek	(118		)
Balance at March 31, 2012	$	456

Use of estimates

GAAP requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The significant estimates in these condensed consolidated financial statements include revenue recognition, useful lives with respect to long-lived assets and intangibles, valuation of stock options, convertible preferred stock warrants, contingencies, accrued expenses, intangible assets, goodwill, in-process research and development and tax valuation reserves. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management.

Cash, Cash Equivalents and Restricted Cash

Cash and cash equivalents are short-term, highly liquid investments with an original maturity of three months or less at the date of purchase. Investments qualifying as cash equivalents primarily consist of money market funds.

Cash accounts with any type of restriction are classified as restricted cash. If restrictions are expected to be lifted in the next twelve months, the restricted cash account is classified as current. As of December 31, 2011 and March 31, 2012, the Company recorded restricted cash of $381,000 and $481,000, respectively.

Revenue Recognition

The Company enters into biopharmaceutical product development agreements with collaborative partners for the research and development of therapeutic and diagnostic products. The terms of the agreements may include nonrefundable signing and licensing fees, funding for research, development and manufacturing, milestone payments and royalties on any product sales derived from collaborations. These multiple element arrangements are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting.

In January 2011, the Company adopted new authoritative guidance on revenue recognition for multiple element arrangements. This guidance, which applies to multiple element arrangements entered into or materially modified on or after January 1, 2011, amends the criteria for separating and allocating consideration in a multiple element arrangement by modifying the fair value requirements for revenue recognition and eliminating the use of the residual method. The fair value of deliverables under the arrangement may be derived using a best estimate of selling price if vendor specific objective evidence and third-party evidence are not available. Deliverables under the arrangement will be separate units of accounting provided that a delivered item has value to the customer on a stand-alone basis and if the arrangement does not include a general right of return relative to the delivered item and delivery or performance of the undelivered item is considered probable and substantially in the control of the vendor. The Company also adopted guidance that permits the recognition of revenue contingent upon the achievement of a milestone in its entirety, in the period in which the milestone is achieved, only if the milestone meets certain criteria and is considered to be substantive. The Company did not enter into any significant multiple element arrangements or materially modify any of its existing multiple element arrangements during the year ended December 31, 2011 or the three months ended March 31, 2012. The Company’s existing license and collaboration agreements continue to be accounted for under previously issued revenue recognition guidance for multiple element arrangements and milestone revenue recognition, as described below.

The Company recognized upfront license payments as revenue upon delivery of the license only if the license had stand-alone value and the fair value of the undelivered performance obligations could be determined. If the fair value of the undelivered performance obligations could be determined, such obligations were accounted for separately as the obligations were fulfilled. If the license was considered to either not have stand-alone value or have stand-alone value but the fair value of any of the undelivered performance obligations could not be determined, the arrangement was accounted for as a single unit of accounting and the license payments and payments for performance obligations were recognized as revenue over the estimated period of when the performance obligations would be performed.

Whenever the Company determined that an arrangement should be accounted for as a single unit of accounting, it determined the period over which the performance obligations would be performed and revenue would be recognized. If the Company could not reasonably estimate the timing and the level of effort to complete its performance obligations under the arrangement, then revenue under the arrangement was recognized on a straight-line basis over the period the Company expected to complete its performance obligations, which is reassessed at each subsequent reporting period.

The Company’s collaboration agreements may include additional payments upon the achievement of performance-based milestones. As milestones are achieved, a portion of the milestone payment, equal to the percentage of the total time that the Company has performed the performance obligations to date over the total estimated time to complete the performance obligations, multiplied by the amount of the milestone payment, will be recognized as revenue upon achievement of such milestone. The remaining portion of the milestone will be recognized over the remaining performance period. Milestones that are tied to regulatory approval are not considered probable of being achieved until such approval is received. Milestones tied to counter-party performance are not included in the Company’s revenue model until the performance conditions are met.

Royalty revenue will be recognized upon the sale of the related products provided the Company has no remaining performance obligations under the arrangement.

Convertible Preferred Stock and Convertible Preferred Stock Warrants

Convertible preferred stock is initially recorded at the proceeds received, net of issuance costs and warrants, where applicable. There was no activity related to the convertible preferred stock for the three months ended March 31, 2012. However, as described in Note 3, in April 2012, the Company closed the initial public offering of its common stock. Upon closing, all outstanding shares of the Company’s convertible preferred stock were converted into 66,255,529 shares of common stock.

The Company accounts for freestanding warrants as liabilities at their fair value. The Company measures the fair value of the convertible preferred stock warrants at the end of each reporting period and records the change in fair value to other income (expense). For the three months ended March 31, 2011 and 2012, the Company recorded other income (expense) related to this re-measurement of $(716,000) and $559,000, respectively. However, as described in Note 3, in April 2012, the Company closed the initial public offering of its common stock. Upon closing, all outstanding warrants to purchase shares of convertible preferred stock were converted into warrants to purchase shares of common stock.

Other Income (Expense)

The Company records gains and losses on the change in value and time to expiration of convertible preferred stock warrants, the recognition of federal and state sponsored tax incentives and other one-time income or expense-related items in other income (expense) on the Company’s condensed consolidated statement of operations. Other income for the three months ended March 31, 2011 included a cash settlement of $1.8 million from a former service provider.

Deferred Financing Costs

The Company capitalizes certain legal, accounting and other fees that are directly associated with in-process equity financings as current assets until such financings occur. After occurrence, these costs are recorded in equity, in the case of a common stock financing, or mezzanine equity, in the case of a convertible preferred stock financing, net of proceeds received.

As of December 31, 2011 and March 31, 2012, the Company recorded deferred financing costs of $1,946,000 and $2,631,000, respectively, on the accompanying condensed consolidated balance sheet in contemplation of an initial public offering. As discussed in Note 3, in April 2012, the Company closed the initial public offering of its common stock. Upon closing, these deferred financing costs were netted against the equity proceeds within stockholders’ equity (deficit).

Initial Public Offering

3 Months Ended

Mar. 31, 2012

Initial Public Offering

Initial Public Offering

3. Initial Public Offering

In April 2012, the Company closed the initial public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company sold an aggregate of 15,042,459 shares of common stock under the registration statement at a public offering price of $7.00 per share, including 742,459 shares pursuant to the exercise by the underwriters of an over-allotment option. Net proceeds were approximately $100.5 million, after deducting underwriting discounts and commissions but prior to the payment of remaining offering expenses payable by the Company and accrued dividends on the Company’s Series B convertible preferred stock.

Upon closing the initial public offering, all outstanding shares of the Company’s convertible preferred stock were converted into 66,255,529 shares of common stock, all outstanding warrants to purchase shares of convertible preferred stock were converted into warrants to purchase shares of common stock and approximately $4.3 million of cash dividends became payable to the holders of Series B convertible preferred stock.

Net Loss per Common Share

3 Months Ended

Mar. 31, 2012

Net Loss per Common Share

Net Loss per Common Share

4. Net Loss per Common Share

Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, convertible preferred stock, stock options and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

The following table presents the computation of basic and diluted net loss per share available to common stockholders for the three months ended March 31, 2011 and 2012:

	Three months ended March 31,
(in thousands, except per share amount)	2011			2012

Net Loss Per Share:
Numerator:
Net loss attributable to Merrimack Pharmaceuticals, Inc.	$	(13,457	)	$	(23,284	)
Plus: Unaccreted dividends on convertible preferred stock	(1,537		)	(2,040		)

Net loss available to common stockholders—basic and diluted	(14,994		)	(25,324		)
Denominator:
Weighted-average common shares—basic and diluted	11,106			11,846

Net loss per share available to common stockholders—basic and diluted	$	(1.35	)	$	(2.14	)

The following common stock equivalents of potentially dilutive securities have been excluded from the computation of diluted weighted average shares outstanding as of March 31, 2011 and 2012, as the Company recorded a net loss in all periods and, therefore, they would be anti-dilutive:

	Three months ended March 31,
(in thousands)	2011	2012

Convertible preferred stock	55,254	66,256
Options to purchase common stock	15,939	17,515
Convertible preferred stock warrants	304	302
Common stock warrants	2,937	2,631

- Definition

The entire disclosure for earnings per share.

+ References+ Details

License and Collaboration Agreements

3 Months Ended

Mar. 31, 2012

License and Collaboration Agreements

License and Collaboration Agreements

5. License and Collaboration Agreements

Sanofi

On September 30, 2009, the Company entered into a license and collaboration agreement with Sanofi for the development and commercialization of a drug candidate being developed by the Company under the name MM-121. The agreement became effective on November 10, 2009 and Sanofi paid the Company a nonrefundable, noncreditable upfront license fee of $60.0 million. During the third quarter of 2010 and the fourth quarter of 2011, the Company received a total of $20.0 million in milestone payments associated with dosing the first patients in Phase 2 clinical trials in breast cancer and non-small cell lung cancer. During the first quarter of 2012, the Company received an additional milestone payment of $5.0 million associated with dosing the first patient in a Phase 2 clinical trial in ovarian cancer. The Company is eligible to receive additional future development, regulatory and sales milestone payments as well as future royalty payments depending on the success of MM-121.

Under the agreement, Sanofi is responsible for all MM-121 development and manufacturing costs. The Company retained the right to participate in the development of MM-121 through Phase 2 proof of concept trials. The Company also has the right, but not the obligation, to co-promote MM-121 in the United States. Sanofi reimburses the Company for direct costs incurred in development and compensates the Company for its internal development efforts based on a full time equivalent (“FTE”) rate. Also as part of the agreement, the Company was required to manufacture certain quantities of MM-121 and, at Sanofi’s and the Company’s option, may continue to manufacture additional quantities of MM-121 in the future. Sanofi reimburses the Company for direct costs incurred in manufacturing and compensates the Company for its internal manufacturing efforts based on an FTE rate. The Company satisfied its manufacturing obligations during 2010 and has elected to continue to manufacture quantities of MM-121.

The Company applied revenue recognition guidance to determine whether the performance obligations under this collaboration, including the license, the right to future technology, back-up compounds, participation on steering committees, development services and manufacturing services, could be accounted for separately or as a single unit of accounting. The Company determined that its development services performance obligation is considered a separate unit of accounting, as it is set at the Company’s option, has stand-alone value and the FTE rate is considered fair value. Therefore, the Company recognizes cost reimbursements for MM-121 development services as incurred. The Company determined that the license, the right to future technology, back-up compounds, participation on steering committees and manufacturing services performance obligations represented a single unit of accounting. As the Company cannot reasonably estimate its level of effort over the collaboration, the Company recognizes revenue from the upfront payment, milestone payment and manufacturing services payments using the contingency-adjusted performance model over the expected development period, which is currently estimated to be 12 years from the effective date of the agreement. Under this model, when a milestone is earned or manufacturing services are rendered and product is delivered, revenue is immediately recognized on a pro-rata basis in the period the milestone was achieved or product was delivered based on the time elapsed from the effective date of the agreement. Thereafter, the remaining portion is recognized on a straight-line basis over the remaining development period.

During the three months ended March 31, 2011 and 2012, the Company recognized revenue based on the following components of the Sanofi agreement:

	Three months ended March 31,
(in thousands)	2011		2012

Upfront payment	$	1,250	$	1,250
Milestone payment	208		1,412
Development services	4,705		8,142
Manufacturing services and other	255		521

Total	$	6,418	$	11,325

As of December 31, 2011 and March 31, 2012, the Company maintained the following assets and liabilities related to the Sanofi agreement:

(in thousands)	December 31, 2011		March 31, 2012

Accounts receivable, billed	$	4,478	$	2,123
Accounts receivable, unbilled	2,925		3,827
Deferred revenue	84,466		87,847

PharmaEngine, Inc.

On May 5, 2011, the Company entered into an assignment, sublicense and collaboration agreement with PharmaEngine, Inc. (“PharmaEngine”) under which the Company reacquired rights in Europe and certain countries in Asia to a drug being developed under the name MM-398. In exchange, the Company agreed to pay PharmaEngine a nonrefundable, noncreditable upfront payment of $10.0 million and will be required to make up to an aggregate of $80.0 million in development and regulatory milestone payments and $130.0 million in sales milestone payments upon the achievement of specified development, regulatory and annual net sales milestones. During the first quarter of 2012, the Company paid a milestone of $5.0 million under the collaboration agreement with PharmaEngine in connection with dosing the first patient in a Phase 3 clinical trial of MM-398 in pancreatic cancer. PharmaEngine is also entitled to tiered royalties on net sales of MM-398 in Europe and certain countries in Asia. The Company is responsible for all future development costs of MM-398 except those required specifically for regulatory approval in Taiwan. The Company determined that PharmaEngine is a variable interest entity based on an analysis of PharmaEngine’s capitalization. However, the Company determined that the Company cannot control the activities of PharmaEngine, and therefore, the Company is not the primary beneficiary and should not consolidate the financial results of PharmaEngine.

During the three months ended March 31, 2012, the Company recognized research and development expenses of $5.3 million related to the agreement with PharmaEngine, which consisted of the $5.0 million milestone payment and $0.3 million of research and development reimbursement.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2012

Fair Value of Financial Instruments

Fair Value of Financial Instruments

6. Fair Value of Financial Instruments

The carrying amounts of cash and cash equivalents, prepaid expenses, accounts receivable, accounts payable and accrued expenses and other short-term assets and liabilities approximate fair value due to the short-term nature of these instruments. The capital lease obligations and convertible preferred stock warrants are also carried at fair value.

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.

The following tables show assets and liabilities measured at fair value on a recurring basis as of December 31, 2011 and March 31, 2012 and the input categories associated with those assets and liabilities:

As of December 31, 2011 (in thousands)	Level 1		Level 2		Level 3

Assets
Cash equivalents — Money Markets	$	35,076	$	—	$	—
Liabilities
Convertible preferred stock warrants	—		—		1,516

As of March 31, 2012 (in thousands)	Level 1		Level 2	Level 3

Assets
Cash equivalents — Money Markets	$	3,636	—	—
Liabilities
Convertible preferred stock warrants	—		—	957

The Company’s investment portfolio consists of investments classified as cash equivalents. All highly liquid investments with an original maturity of three months or less when purchased are considered to be cash equivalents. The Company’s cash and cash equivalents are invested in a U.S. treasury and federal agency-backed money market fund that approximates its face value. The fair value of the convertible preferred stock warrants as of December 31, 2011 and March 31, 2012 was determined using the Black-Scholes option valuation model.

The following table provides a roll-forward of the fair value of the convertible preferred stock warrants categorized as Level 3 instruments, for the three months ended March 31, 2011 and 2012:

(in thousands)	Convertible preferred stock warrants

Balance, December 31, 2010	$	652
Unrealized loss included in other income (expense)	716

Balance, March 31, 2011	$	1,368

(in thousands)	Convertible preferred stock warrants

Balance, December 31, 2011	$	1,516
Unrealized gain included in other income (expense)	(559		)

Balance, March 31, 2012	$	957

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13504-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19296-110258

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 30

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44A, 44B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15C, 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15A

-Subparagraph a-d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15B

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 3, 10, 14, 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32, 33, 34

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 17-22, 27, 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13537-108611

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

+ Details

Accrued Expenses and other

3 Months Ended

Mar. 31, 2012

Accrued Expenses and other

Accrued Expenses and other

7. Accrued Expenses and other

Accrued expenses and other as of December 31, 2011 and March 31, 2012 consisted of the following:

(in thousands)	December 31, 2011		March 31, 2012

Goods and services	$	9,189	$	8,457
Payroll and related benefits	3,666		3,382
Contractual liability	—		1,222

Total accrued expenses and other	$	12,855	$	13,061

As described in Note 10, the Company has recorded a contractual liability of $1.2 million related to a contractual matter with Sanofi.

Common Stock

3 Months Ended

Mar. 31, 2012

Common Stock

Common Stock

8. Common Stock

During the first quarter of 2012, the Company amended its certificate of incorporation to increase the number of authorized shares of common stock to 200.0 million. As of December 31, 2011 and March 31, 2012, the Company had 138.5 million shares and 200.0 million shares, respectively, of common stock, $0.01 par value per share, authorized.

There were 11,834,000 and 11,907,000 shares of common stock issued and outstanding as of December 31, 2011 and March 31, 2012, respectively. The shares reserved for future issuance as of December 31, 2011 and March 31, 2012 consisted of the following:

(in thousands)	December 31, 2011	March 31, 2012

Conversion of Series B, Series C, Series D, Series E, Series F and Series G convertible preferred stock	66,256	66,256
Convertible preferred stock warrants	302	302
Common stock warrants	2,640	2,631
1999 Stock Option Plan and 2008 Stock Incentive Plan	17,617	17,515

	86,815	86,704

As discussed in Note 3, in April 2012, the Company closed the initial public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company sold an aggregate of 15,042,459 shares of common stock under the registration statement at a public offering price of $7.00 per share, including 742,459 shares pursuant to the exercise by the underwriters of an over-allotment option. Upon closing, all outstanding shares of the Company’s convertible preferred stock were converted into 66,255,529 shares of common stock.

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(d),(e))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 4

-Subparagraph (SAB TOPIC 4.C)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187143-122770

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section C

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 4.E)

-URI http://asc.fasb.org/extlink&oid=6228006&loc=d3e74512-122707

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-31)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Preferred Stock

-URI http://asc.fasb.org/extlink&oid=6521494

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 15: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 17: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph d

Reference 18: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 1

-Section B

-Paragraph 7, 11A

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 19: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 3, 4, 5, 6, 7, 8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 20: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Article 4

Reference 21: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 22: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

Reference 23: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section E

+ Details

Stock-Based Compensation

3 Months Ended

Mar. 31, 2012

Stock-Based Compensation

Stock-Based Compensation

9. Stock-Based Compensation

During the three months ended March 31, 2011 and 2012, the Company did not issue options to purchase shares of common stock.

As of December 31, 2011 and March 31, 2012, there were 830,000 and 866,111 shares of common stock, respectively, available to be issued under the 2008 Stock Incentive Plan, as amended (the “2008 Plan”).

The 2011 Stock Incentive Plan (the “2011 Plan”) became effective upon closing of the Company’s initial public offering in April 2012. Upon effectiveness of the 2011 Plan, no further awards were available to be issued under the 2008 Plan. The 2011 Plan is administered by the Board of Directors of the Company 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. The 2011 Plan increases the total number of shares of common stock available to be issued by 3.5 million.

The Company recognized stock-based compensation expense as follows for the three months ended March 31, 2011 and 2012:

	Three months ended March 31,
(in thousands)	2011		2012

Employee awards:
Research and development	$	700	$	909
General and administrative	273		430

Stock-based compensation for employee awards	973		1,339
Stock-based compensation for nonemployee awards	47		—

Total stock-based compensation	$	1,020	$	1,339

The following table summarizes stock option activity during the three months ended March 31, 2012:

(in thousands, except per share amounts)	Number of shares		Weighted average exercise price		Aggregate intrinsic value

Outstanding, December 31, 2011	17,617		$	2.56	$	74,329

Exercised	(66	)	$	2.24
Forfeited	(36	)	$	3.37

Outstanding, March 31, 2012	17,515		$	2.56	$	63,769

Exercisable, March 31, 2012	14,171		$	2.23	$	56,177
Vested and expected to vest, March 31, 2012	17,339		$	2.54	$	63,485

The aggregate intrinsic value was calculated as the difference between the exercise price of the stock options and the fair value of the underlying common stock as of the respective balance sheet date.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64, 65, A240

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 53

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 50

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5444-113901

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Commitments and Contingencies

3 Months Ended

Mar. 31, 2012

Commitments and Contingencies

Commitments and Contingencies

10. Commitments and Contingencies

Operating leases

The Company leases its office, laboratory and manufacturing space under non-cancellable operating leases. Total rent expense under these operating leases was $700,000 and $893,000 for the three months ended March 31, 2011 and 2012, respectively.

During the first quarter of 2012, the Company entered into a lease amendment to further expand its office, laboratory and manufacturing space. The amendment leases additional space for a seven year term effective March 2012. The aggregate rent due over the seven year term of the lease amendment is approximately $2.7 million. As part of this agreement, the landlord agreed to reimburse the Company for a portion of tenant improvements made to the facility, up to a total of $464,000. Tenant improvements are recorded in deferred lease benefits on the accompanying condensed consolidated balance sheets and amortized over the term of the lease as reductions to rent expense.

During the first quarter of 2012, the Company completed tenant improvements to the leased facility and recorded a related receivable from the landlord of $329,000 in prepaid expenses and other assets on the accompanying condensed consolidated balance sheets as of March 31, 2012.

Contingencies

Contractual matter

The Company manufactures MM-121 under a license and collaboration agreement with Sanofi. Under this agreement, Sanofi reimburses the Company for direct costs incurred in manufacturing. During 2009 and 2010, the Company utilized a third party contractor to perform fill-finish manufacturing services. This third party contractor experienced U.S. Food and Drug Administration (“FDA”) inspection issues with its quality control process that resulted in a formal warning letter from the FDA. Following a review by Sanofi and the Company, some MM-121 was pulled from clinical trial sites and replaced with MM-121 that was filled by a different contractor. Sanofi had requested that the Company assume financial responsibility for the MM-121 material that was pulled from clinical trial sites. The Company and Sanofi have since agreed that, during 2012 and 2013, the Company will reimburse Sanofi approximately $1.2 million of previously billed amounts. The Company has recorded a contractual liability of $1.2 million in accrued expenses and other on the accompanying condensed consolidated balance sheets as of March 31, 2012. The Company’s revenue recognition model for manufacturing services performed under the license and collaboration agreement with Sanofi is to recognize these services over the period of performance, which is currently estimated to be 12 years from the effective date of the agreement. Removal of these previously billed amounts from the revenue recognition model and establishing this contractual liability resulted in an earnings reduction of $0.2 million for the three months ended March 31, 2012 in the accompanying condensed consolidated statement of operations.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 14

-Paragraph 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.25)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25287-109308

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621

+ Details

Related Party Transactions

3 Months Ended

Mar. 31, 2012

Related Party Transactions

Related Party Transactions

11. Related Party Transactions

In connection with the initial public offering of the Company’s common stock, Sanofi purchased 5,217,391 shares of the Company’s common stock in April 2012.

- Definition

The entire disclosure for related party transactions, including the nature of the relationship(s), a description of the transactions, the amount of the transactions, the effects of any change in the method of establishing the terms of the transaction from the previous period, stated interest rate, expiration date, terms and manner of settlement per the agreement with the related party, and amounts due to or from related parties. If the entity and one or more other entities are under common ownership or management control and this control affects the operating results or financial position, disclosure includes the nature of the control relationship even if there are no transactions between the entities. Disclosure may also include the aggregate amount of current and deferred tax expense for each statement of earnings presented where the entity is a member of a group that files a consolidated tax return, the amount of any tax related balances due to or from affiliates as of the date of each statement of financial position presented, the principal provisions of the method by which the consolidated amount of current and deferred tax expense is allocated to the members of the group and the nature and effect of any changes in that method. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph k

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 3A

-Section 04

-Paragraph b

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 1-4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(k))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39691-107864

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864

+ Details