Alnylam Pharmaceuticals (ALNY) 10-Q 9 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	ALNY
Entity Registrant Name	ALNYLAM PHARMACEUTICALS, INC.
Entity Central Index Key	1,178,670
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		91,733,369

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 408,671	$ 193,617
Marketable securities	514,600	424,185
Investment in equity securities of Regulus Therapeutics Inc.		8,997
Billed and unbilled collaboration receivables	15,405	23,334
Prepaid expenses and other current assets	22,033	21,744
Total current assets	960,709	671,877
Marketable securities	174,570	324,799
Property, plant and equipment, net	147,533	114,572
Restricted investments	150,000	150,000
Other assets	1,471	1,562
Total assets	1,434,283	1,262,810
Current liabilities:
Accounts payable	23,170	54,465
Accrued expenses	43,820	42,118
Deferred rent	1,942	1,576
Deferred revenue	39,794	33,540
Total current liabilities	108,726	131,699
Deferred rent, net of current portion	7,697	8,431
Deferred revenue, net of current portion	42,079	49,392
Long-term debt	150,000	150,000
Other liabilities	2,815	3,067
Total liabilities	311,317	342,589
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.01 par value per share, 5,000,000 shares authorized and no shares issued and outstanding at June 30, 2017 and December 31, 2016
Common stock, $0.01 par value per share, 125,000,000 shares authorized; 91,701,397 shares issued and outstanding at June 30, 2017; 85,941,344 shares issued and outstanding at December 31, 2016	917	859
Additional paid-in capital	3,038,529	2,609,614
Accumulated other comprehensive loss	(33,959)	(33,441)
Accumulated deficit	(1,882,521)	(1,656,811)
Total stockholders’ equity	1,122,966	920,221
Total liabilities and stockholders’ equity	$ 1,434,283	$ 1,262,810

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	91,701,397	85,941,344
Common stock, shares outstanding	91,701,397	85,941,344

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net revenues from collaborators		$ 15,932	$ 8,709	$ 34,892	$ 16,054
Operating expenses:
Research and development	[1]	90,627	83,172	177,611	179,445
General and administrative	[1]	45,779	17,987	84,266	39,087
Total operating expenses		136,406	101,159	261,877	218,532
Loss from operations		(120,474)	(92,450)	(226,985)	(202,478)
Other income (expense):
Interest income		2,577	2,092	4,705	3,905
Other (expense) income		(523)	229	(3,430)	5,470
Total other income		2,054	2,321	1,275	9,375
Net loss		$ (118,420)	$ (90,129)	$ (225,710)	$ (193,103)
Net loss per common share - basic and diluted		$ (1.34)	$ (1.05)	$ (2.59)	$ (2.26)
Weighted-average common shares used to compute basic and diluted net loss per common share		88,098	85,545	87,068	85,411
Comprehensive loss:
Net loss		$ (118,420)	$ (90,129)	$ (225,710)	$ (193,103)
Unrealized loss on marketable securities, net of tax		(476)	(18,331)	(2,412)	(26,555)
Reclassification adjustment for realized loss (gain) on marketable securities included in net loss		345	(954)	1,894	(6,110)
Comprehensive loss		$ (118,551)	$ (109,414)	$ (226,228)	$ (225,768)
[1]	Stock-based compensation expenses included in operating expenses are as follows: Research and development $13,254 $9,277 $21,945 $23,633 General and administrative 10,776 6,539 17,802 15,663

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Stock-based compensation			$ 39,747	$ 39,296
Research and Development
Stock-based compensation	$ 13,254	$ 9,277	21,945	23,633
General and Administrative
Stock-based compensation	$ 10,776	$ 6,539	$ 17,802	$ 15,663

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net loss	$ (225,710)	$ (193,103)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,066	8,612
Stock-based compensation	39,747	39,296
Charge for 401(k) company stock match	1,074	781
Realized loss (gain) on sale of marketable equity securities	1,894	(6,110)
Other	608
Changes in operating assets and liabilities:
Billed and unbilled collaboration receivables	7,929	(1,216)
Prepaid expenses and other assets	(198)	(5,593)
Accounts payable	(8,326)	(3,590)
Accrued expenses and other	(3,404)	1,717
Deferred revenue	(1,059)	5,378
Net cash used in operating activities	(181,379)	(153,828)
Cash flows from investing activities:
Purchases of property, plant and equipment	(57,803)	(24,380)
Purchases of restricted investments		(150,000)
Purchases of marketable securities	(237,184)	(357,992)
Sales and maturities of marketable securities	302,392	605,977
Net cash provided by investing activities	7,405	73,605
Cash flows from financing activities:
Proceeds from exercise of stock options and other types of equity	12,644	6,266
Proceeds from issuance of common stock, net of offering costs	355,150
Proceeds from issuance of common stock to Sanofi Genzyme	21,381	14,301
Proceeds from issuance of long-term debt		150,000
Payments for repurchase of common stock for employee tax withholding	(147)	(163)
Net cash provided by financing activities	389,028	170,404
Net increase in cash and cash equivalents	215,054	90,181
Cash and cash equivalents, beginning of period	193,617	180,895
Cash and cash equivalents, end of period	$ 408,671	$ 271,076

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements of Alnylam Pharmaceuticals, Inc. are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, applicable to interim periods and, in the opinion of management, include all normal and recurring adjustments that are necessary to present fairly the results of operations for the reported periods. Our condensed consolidated financial statements have also been prepared on a basis substantially consistent with, and should be read in conjunction with, our audited consolidated financial statements for the year ended December 31, 2016, which were included in our Annual Report on Form 10-K that was filed with the Securities and Exchange Commission, or SEC, on February 15, 2017. The year-end condensed consolidated balance sheet data was derived from our audited financial statements, but does not include all disclosures required by GAAP. The results of our operations for any interim period are not necessarily indicative of the results of our operations for any other interim period or for a full fiscal year. The accompanying condensed consolidated financial statements reflect the operations of Alnylam and our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Liquidity Based on our current operating plan, we believe that our cash, cash equivalents and fixed income marketable securities at June 30, 2017, together with the cash we expect to generate under our current alliances, will be sufficient to enable us to advance our Alnylam 2020 Net Loss Per Common Share We compute basic net loss per common share by dividing net loss by the weighted-average number of common shares outstanding. We compute diluted net loss per common share by dividing net loss by the weighted-average number of common shares and dilutive potential common share equivalents then outstanding. Potential common shares consist of shares issuable upon the exercise of stock options (the proceeds of which are then assumed to have been repurchased using the treasury stock method). Because the inclusion of potential common shares would be anti-dilutive for all periods presented, diluted net loss per common share is the same as basic net loss per common share. The following table sets forth for the periods presented the potential common shares (prior to consideration of the treasury stock method) excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive, in thousands: At June 30, 2017 2016 Options to purchase common stock 12,372 10,377 Unvested restricted common stock 172 179 12,544 10,556 Public Offering In May 2017, we sold an aggregate of 5,000,000 shares of our common stock through an underwritten public offering at a price to the public of $71.87 per share. As a result of the offering, we received aggregate net proceeds of $355.2 million after deducting underwriting discounts and commissions and other offering expenses of $4.2 million. Equity Total stockholders’ equity at June 30, 2017 increased by $202.7 million compared to December 31, 2016. This increase was related primarily to increases to additional paid-in capital due to our public offering in May 2017, our issuance of common stock to Sanofi Genzyme in May 2017 and stock-based compensation, partially offset during the six months ended June 30, 2017 by our net loss. Fair Value Measurements The fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs utilize data points that are observable, such as quoted prices (adjusted), interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. The fair value hierarchy level is determined by the lowest level of significant input. Investments in Marketable Securities and Cash Equivalents We invest our excess cash balances in short-term and long-term marketable debt and equity securities. We classify our investments in marketable debt securities as either held-to-maturity or available-for-sale based on facts and circumstances present at the time we purchased the securities. At each balance sheet date presented, we classified all of our investments in debt and equity securities as available-for-sale. We report available-for-sale investments at fair value at each balance sheet date and include any unrealized holding gains and losses (the adjustment to fair value) in accumulated other comprehensive income (loss), a component of stockholders’ equity. At June 30, 2017, the balance in our accumulated other comprehensive loss was composed solely of activity related to our available-for-sale marketable securities, including our investment in equity securities of Regulus Therapeutics Inc., or Regulus. Realized gains and losses are determined using the specific identification method and are included in other income (expense). We recognized $0.3 million of realized losses and $1.0 million of realized gains from sales of our Regulus available-for-sale securities as other income (expense) in our condensed consolidated statements of comprehensive loss during the three months ended June 30, 2017 and 2016, respectively. In addition, we recognized $1.9 million of realized losses and $6.1 million of realized gains from sales of our Regulus available-for-sale securities as other income (expense) in our condensed consolidated statements of comprehensive loss during the six months ended June 30, 2017 and 2016, respectively. If any adjustment to arrive at fair value reflects a decline in the value of the investment, we consider all available evidence to evaluate the extent to which the decline is “other than temporary,” including our intention to sell and, if so, record a charge to our condensed consolidated statements of comprehensive loss. We did not record any impairment charges related to our fixed income marketable securities during the six months ended June 30, 2017 or 2016. Our marketable securities are classified as cash equivalents if the original maturity, from the date of purchase, is 90 days or less, and as marketable securities if the original maturity, from the date of purchase, is in excess of 90 days. Our cash equivalents are composed of commercial paper, money market funds, and U.S. government-sponsored enterprise securities During the second quarter of 2017, we sold all our remaining holdings in Regulus. We accounted for our investment in Regulus as an available-for-sale marketable security. Intraperiod tax allocation rules require us to allocate our provision for income taxes between continuing operations and other categories of earnings, such as other comprehensive income. In periods in which we have a year-to-date pre-tax loss from continuing operations and pre-tax income in other categories of earnings, such as other comprehensive income, we must allocate the tax provision to the other categories of earnings. We then record a related tax benefit in continuing operations. Upon sales of our available-for-sale marketable securities, we apply the aggregate portfolio approach to recognize the related tax provision or benefit into income (loss) from continuing operations. As a result, the disproportionate tax effect remains in accumulated other comprehensive income (loss) as long as we maintain an investment portfolio. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued a new revenue recognition standard which amends revenue recognition principles and provides a single, comprehensive set of criteria for revenue recognition within and across all industries. The new standard provides a five step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires enhanced disclosures pertaining to revenue recognition in both interim and annual periods. In August 2015, the FASB deferred the effective date of the new revenue standard from January 1, 2017 to January 1, 2018. In March 2016, the FASB issued amendments to clarify the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued amendments to clarify the guidance on accounting for licenses of intellectual property and identifying performance obligations. In May 2016, the FASB issued amendments related to collectibility, non-cash consideration, the presentation of sales and other similar taxes collected from customers and transition. The standard allows for adoption using a full retrospective method or a modified retrospective method. We plan to adopt this standard using the modified retrospective method. During the second half of 2017, we plan to complete our review of our revenue streams to determine the impact that this standard could have on our condensed consolidated financial statements and related disclosures. In January 2016, the FASB issued new guidance on recognition and measurement of financial assets and financial liabilities. The new guidance will impact the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. All equity investments in unconsolidated entities (other than those accounted for under the equity method of accounting) will generally be measured at fair value with changes in fair value recognized through earnings. There will no longer be an available-for-sale classification (changes in fair value reported in other comprehensive income (loss)) for equity securities with readily determinable fair values. In addition, the FASB clarified the need for a valuation allowance on deferred tax assets resulting from unrealized losses on available-for-sale debt securities. In general, the new guidance will require modified retrospective application to all outstanding instruments, with a cumulative effect adjustment recorded to opening retained earnings. This guidance will be effective for us on January 1, 2018. We are currently evaluating the expected impact that the standard could have on our condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued a new leasing standard that requires that all lessees recognize the assets and liabilities that arise from leases on the condensed consolidated balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for us on January 1, 2019. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In October 2016, the FASB issued guidance that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs instead of deferring the income tax effects. The new standard will be effective for us on a modified retrospective basis on January 1, 2018. We are currently evaluating the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In November 2016, the FASB issued guidance that requires restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. The new standard will be effective for us on January 1, 2018 using a retrospective transition method to each period presented. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In March 2017, the FASB issued guidance that amends the amortization period for certain purchased callable debt securities held at a premium by shortening the amortization period for the premium to the earliest call date. The new standard will be effective for us on January 1, 2019. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In May 2017, the FASB issued guidance that clarifies when changes to the terms or conditions of share-based payment awards must be accounted for as modifications. The new standard will be applied prospectively to awards modified on or after the adoption date and will be effective for us on January 1, 2018. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on our condensed consolidated financial statements and related disclosures. Subsequent Event We did not have any material recognized subsequent events. However, we did have the following nonrecognized subsequent event, which is more fully described in Note 5. • On August 8, 2017, Dicerna Pharmaceuticals, Inc., or Dicerna, filed a new complaint in the United States District Court for the District of Massachusetts asserting a claim for attempted monopolization under the Sherman Antitrust Act.

COLLABORATION AGREEMENTS

COLLABORATION AGREEMENTS	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
COLLABORATION AGREEMENTS	2. COLLABORATION AGREEMENTS The following table summarizes our total consolidated net revenues from collaborators, for the periods indicated, in thousands: Three Months Ended June 30, Six Months Ended June 30, Description 2017 2016 2017 2016 Sanofi Genzyme $ 14,375 $ 5,387 $ 26,652 $ 9,802 The Medicines Company 1,522 3,268 7,886 5,925 Other 35 54 354 327 Total net revenues from collaborators $ 15,932 $ 8,709 $ 34,892 $ 16,054 Product Alliances Sanofi Genzyme Collaboration In January 2014, we entered into a global, strategic collaboration with Sanofi Genzyme, the specialty care global business unit of Sanofi, to discover, develop and commercialize RNA interference, or RNAi, therapeutics as Genetic Medicines to treat orphan diseases. The 2014 Sanofi Genzyme collaboration superseded and replaced the previous collaboration between us and Sanofi Genzyme entered into in October 2012 to develop and commercialize RNAi therapeutics targeting transthyretin, or TTR, for the treatment of hereditary ATTR amyloidosis, including patisiran and revusiran, in Japan and the Asia-Pacific region. 2012 Sanofi Genzyme Agreement Under the 2012 Sanofi Genzyme agreement, Sanofi Genzyme paid us an upfront cash payment of $22.5 million. We were also entitled to receive certain milestone payments under the 2012 Sanofi Genzyme agreement. In the fourth quarter of 2013, we earned a milestone of $7.0 million based upon the completion of a successful patisiran Phase 2 clinical trial and a milestone of $4.0 million based upon the initiation of the APOLLO Phase 3 clinical trial for patisiran. We determined that the deliverables under the 2012 Sanofi Genzyme agreement included the license, a joint steering committee and any additional TTR-specific RNAi therapeutic compounds that comprised the ALN-TTR program. We also determined that, pursuant to the accounting guidance governing revenue recognition on multiple element arrangements, the license and undelivered joint steering committee and any additional TTR-specific RNAi therapeutic compounds did not have standalone value due to the specialized nature of the services to be provided by us. In addition, while Sanofi Genzyme had the ability to grant sublicenses, it could not sublicense all or substantially all of its rights under the 2012 Sanofi Genzyme agreement. The uniqueness of our services and the limited sublicense right were indicators that standalone value was not present in the arrangement. Therefore the deliverables were not separable and, accordingly, the license and undelivered services were treated as a single unit of accounting. We were unable to reasonably estimate the period of performance under the 2012 Sanofi Genzyme agreement, as we were unable to estimate the timeline of our deliverables related to the deliverable for any additional TTR-specific RNAi therapeutic compounds. Through December 31, 2013, we had deferred all revenue, or $33.5 million, under the 2012 Sanofi Genzyme agreement. 2014 Sanofi Genzyme Collaboration In January 2014, we entered into the 2014 Sanofi Genzyme collaboration. As noted above, the 2014 Sanofi Genzyme collaboration superseded and replaced the 2012 Sanofi Genzyme agreement. The 2014 Sanofi Genzyme collaboration is structured as an exclusive relationship for the worldwide development and commercialization of RNAi therapeutics in the field of Genetic Medicines, which includes our current and future Genetic Medicine programs that reach Human Proof-of-Principle Study Completion (as defined in the Sanofi Genzyme master agreement), or Human POP, by the end of 2019, subject to extension to the end of 2021 in various circumstances. We will retain product rights in the United States, Canada and Western Europe, referred to as the Alnylam Territory, while Sanofi Genzyme will obtain exclusive rights to develop and commercialize collaboration products in the rest of the world, referred to as the Sanofi Genzyme Territory, together with certain broader co-development/co-commercialize or worldwide rights for certain products. Sanofi Genzyme’s rights, described in detail below, are structured as an opt-in that is triggered upon achievement of Human POP. We maintain development control for all programs prior to Sanofi Genzyme’s opt-in and maintain development and commercialization control after Sanofi Genzyme’s opt-in for all programs in the Alnylam Territory. We will retain global rights to any RNAi therapeutic Genetic Medicine program that does not reach Human POP by the end of 2019, subject to certain limited exceptions. We retain full rights to all current and future RNAi therapeutic programs outside of the field of Genetic Medicines, including the right to form new collaborations. Under the 2014 Sanofi Genzyme collaboration, Sanofi Genzyme’s specific license rights and the programs into which Sanofi Genzyme has opted include the following: • Regional license terms and programs — Upon opt-in, we will retain product rights in the Alnylam Territory, while Sanofi Genzyme will obtain exclusive rights to develop and commercialize the product in the Sanofi Genzyme Territory. Sanofi Genzyme can elect this license for any of our current and future Genetic Medicine programs that complete Human POP by the end of 2019, subject to limited extension. Development costs for products once Sanofi Genzyme exercises an option will be shared between Sanofi Genzyme and us, with Sanofi Genzyme responsible for twenty percent of the global development costs. Upon the effective date of the 2014 Sanofi Genzyme collaboration, Sanofi Genzyme expanded the scope of its regional license and collaboration for patisiran, an investigational RNAi therapeutic currently in Phase 3 clinical development, which was originally established under the 2012 Sanofi Genzyme agreement. In September 2015, Sanofi Genzyme elected to opt into our fitusiran clinical development program for the treatment of hemophilia and other rare bleeding disorders under the regional license terms. Cost-sharing for the fitusiran program began in January 2016 under the regional license terms. Sanofi Genzyme also had the right to elect to co-develop and co-commercialize fitusiran in the Alnylam Territory pursuant to the co-development/co-commercialize license terms described below. In November 2016, Sanofi Genzyme exercised this right and elected to co-develop and co-commercialize fitusiran in the Alnylam Territory. In addition, during 2016, Sanofi Genzyme elected not to opt into the development and commercialization of givosiran or ALN-CC5 in the Sanofi Genzyme Territory. Sanofi Genzyme will be required to make payments totaling up to $50.0 million upon the achievement of certain patisiran development milestones. We could potentially earn the next patisiran milestone payment, ranging between $5.0 million and $20.0 million based on the geographic region, upon the achievement of specified events in connection with a regulatory filing or approval. In addition, Sanofi Genzyme will be required to make payments totaling up to $75.0 million per regional product other than patisiran, consisting of up to $55.0 million in development milestones and $20.0 million in commercial milestones. Sanofi Genzyme will also be required to pay tiered double-digit royalties up to twenty percent for each regional product based on annual net sales, if any, of such regional product by Sanofi Genzyme, its affiliates and sublicensees. • Co-development/co-commercialize license terms and programs — Upon opt-in, we will retain product rights in the Alnylam Territory, while Sanofi Genzyme will obtain exclusive rights to develop and commercialize the product in the Sanofi Genzyme Territory, and will co-commercialize the product in the Alnylam Territory. Upon the effective date of the 2014 Sanofi Genzyme collaboration, Sanofi Genzyme expanded its regional rights for revusiran, an investigational RNAi therapeutic that was previously being advanced in a Phase 3 clinical trial, which were originally granted under the 2012 Sanofi Genzyme agreement, to include a co-development/co-commercialize license and collaboration. In October 2016, upon the recommendation of the revusiran ENDEAVOUR Phase 3 study Data Monitoring Committee to suspend dosing, we decided to discontinue development of revusiran. As noted above, in November 2016, Sanofi Genzyme exercised its right to elect a co-development/co-commercialize license for fitusiran. Development costs for co-development/co-commercialize products, once Sanofi Genzyme exercises an option, will be shared between Sanofi Genzyme and us, with Sanofi Genzyme responsible for fifty percent of the global development costs. In connection with the exercise of its co-development/co-commercialize rights for fitusiran, Sanofi Genzyme paid us approximately $6.0 million in January 2017 for its incremental share of co-development costs incurred from January 2016 through September 2016. Sanofi Genzyme will be required to make payments totaling up to $75.0 million in development milestones for fitusiran, and, prior to the discontinuation of the revusiran program, was required to make certain milestone payments for revusiran. In December 2014, we earned a development milestone payment of $25.0 million based upon the initiation of the first global Phase 3 clinical trial for revusiran. We expect to earn the first fitusiran milestone payment of $25.0 million upon the dosing of the first patient in our ATLAS Phase 3 program for fitusiran. We announced the initiation of the ATLAS Phase 3 program in July 2017. Sanofi Genzyme will also be required to pay tiered double-digit royalties up to twenty percent for each co-development/co-commercialize product based on annual net sales, if any, in the Sanofi Genzyme Territory for such co-development/co-commercialize product by Sanofi Genzyme, its affiliates and sublicensees. The parties will share profits equally and we expect to book product sales in the Alnylam Territory. • Global license terms and programs — Upon opt-in, Sanofi Genzyme will obtain a worldwide license to develop and commercialize the product. Sanofi Genzyme had the right to elect a global license for givosiran, but instead elected a license to co-develop and co-commercialize fitusiran, as described above. Sanofi Genzyme continues to have one right to a global license through 2019, subject to limited extension, for a future Genetic Medicine program that was not one of our defined Genetic Medicine programs as of the effective date of the 2014 Sanofi Genzyme collaboration. Sanofi Genzyme shall be responsible for one hundred percent of global development costs. Sanofi Genzyme will be required to make payments totaling up to $200.0 million for such global product, including up to $100.0 million in development milestones and $100.0 million in commercial milestones. Sanofi Genzyme will also be required to pay tiered double-digit royalties up to twenty percent for such global product based on annual net sales, if any, of such global product by Sanofi Genzyme, its affiliates and sublicensees. Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, we may not receive any additional milestone payments or any royalty payments from Sanofi Genzyme under the 2014 Sanofi Genzyme collaboration. Under the master agreement, the parties will collaborate in the development of option products, with us leading development for all programs prior to Sanofi Genzyme’s opt-in and also leading development and commercialization for all programs in the Alnylam Territory after Sanofi Genzyme’s opt-in. If Sanofi Genzyme does not exercise its option to license rights to a particular program, we will retain the exclusive right to develop and commercialize such program throughout the world, including the right to sublicense to third parties. The 2014 Sanofi Genzyme collaboration is governed by an alliance joint steering committee that is comprised of an equal number of representatives from each party. There are additional committees to manage various aspects of each regional, co-developed/co-commercialized and global program. We and Sanofi Genzyme intend to enter into supply agreements to provide for supply of collaboration products to Sanofi Genzyme for clinical studies, and, at Sanofi Genzyme’s request, commercial sales. Sanofi Genzyme also has certain rights to manufacture collaboration products. Additionally, Sanofi Genzyme has certain limited opt-out rights, as specified in the master agreement, upon which products revert fully back to us with no further obligations to Sanofi Genzyme. Upon the closing of the equity transaction in February 2014, we sold to Sanofi Genzyme 8,766,338 shares of our common stock and Sanofi Genzyme paid $700.0 million in aggregate cash consideration to us. As a condition to the closing of the equity transaction, Sanofi Genzyme entered into an investor agreement with us containing provisions regarding Sanofi Genzyme’s holding and “standstill” obligations, additional purchase, voting and registration rights, as well as certain other rights and obligations of the parties. We recorded the issuance of 8,766,338 shares of our common stock under the stock purchase agreement using the price of our common stock on the date the shares were issued to Sanofi Genzyme. Based on the common stock price of $85.72, the fair value of the shares issued was $751.5 million, which was $51.5 million in excess of the proceeds received from Sanofi Genzyme for the issuance of our common stock. This $51.5 million is being amortized on a straight-line basis over the performance period. In addition, due to intraperiod tax allocation rules, upon closing of the equity transaction we recorded a benefit from income taxes of $15.2 million due to the Sanofi Genzyme equity purchase being recorded in additional paid-in capital, net of tax. In accordance with the investor agreement, as a result of our issuance of shares in connection with our acquisition of Sirna Therapeutics, Inc., or Sirna, in March 2014, Sanofi Genzyme exercised its right to purchase an additional 344,448 shares of our common stock for $23.0 million. In addition, in connection with our public offerings, Sanofi Genzyme exercised its right to purchase directly from us, in concurrent private placements, 744,566 shares of common stock in January 2015 at the public offering price resulting in $70.7 million in proceeds to us and 297,501 shares of common stock in May 2017 at the public offering price resulting in $21.4 million in proceeds to us. The sales of common stock to Sanofi Genzyme were not registered as part of these public offerings, though they were consummated simultaneously with such public offerings. Sanofi Genzyme also has the right at the beginning of each year to purchase a number of shares of our common stock based on the number of shares we issued during the previous year for compensation-related purposes. Sanofi Genzyme exercised this right to purchase directly from us 196,251 shares of our common stock on January 22, 2015 for $18.3 million and 205,030 shares of our common stock on February 1, 2016 for $14.3 million. In January 2017, Sanofi Genzyme elected not to exercise its compensation-related right for 2016. The sales of these shares to Sanofi Genzyme were consummated as private placements. In each instance, the purchase by Sanofi Genzyme described above allowed Sanofi Genzyme to maintain its ownership level of our common stock of approximately 12 percent. We determined that the deliverables for the programs on which Sanofi Genzyme was collaborating with us upon initiation of the 2014 Sanofi Genzyme collaboration included the licenses to our patisiran and revusiran clinical programs, which licenses were delivered to Sanofi Genzyme upon the closing date of the transaction, and the associated development activities, joint steering committee participation and information exchange for these clinical programs. We also determined that, pursuant to the accounting guidance governing revenue recognition on multiple element arrangements, the license and associated undelivered development activities, joint steering committee participation and information exchange activities did not have standalone value due to the specialized nature of the services to be provided by us. In addition, while Sanofi Genzyme has the ability to grant sublicenses, it cannot sublicense all or substantially all of its rights under the 2014 Sanofi Genzyme collaboration. The uniqueness of our services and the limited sublicense rights are indicators that standalone value is not present in the arrangement. Therefore the deliverables are not separable and, accordingly, the license and undelivered services were treated as a single unit of accounting. When multiple deliverables are accounted for as a single unit of accounting, we base our revenue recognition model on the final deliverable. Under the 2014 Sanofi Genzyme collaboration, the last deliverables for patisiran and revusiran were expected to be completed within approximately six years from the closing date of the transaction and the last deliverables for fitusiran are expected to be completed within approximately five years from the date Sanofi Genzyme elected to opt into our fitusiran clinical development program under the regional license terms. Our estimate regarding the performance period under the 2014 Sanofi Genzyme collaboration related to the license to our patisiran and revusiran clinical programs was adjusted in October 2016 due to our decision to discontinue development of revusiran. As a result, with respect to these programs, we currently expect the last deliverables to be completed within approximately five years from the closing date of the transaction. We determined that the total cash received from Sanofi Genzyme under the now superseded 2012 Sanofi Genzyme agreement reflects consideration for certain of the performance obligations for ALN-TTR programs included in the 2014 Sanofi Genzyme collaboration. Therefore we are recognizing the $33.5 million of deferred revenue under the 2012 Sanofi Genzyme agreement on a straight-line basis over the period of performance of the ALN-TTR programs. As consideration is achieved, including any milestones or reimbursement for development activities, we recognize as revenue a portion of these payments equal to the percentage of the performance period completed when the milestone or activities have been satisfied, multiplied by the amount of the payment. We recognize the remaining portion of consideration received over the remaining performance period on a straight-line basis. The following table presents information related to the 2014 Sanofi Genzyme collaboration, in thousands: Excess of fair value of our common stock issued to Sanofi Genzyme in February 2014 $ (51,450 ) Deferred revenue remaining under the 2012 Sanofi Genzyme agreement upon execution of the 2014 Sanofi Genzyme collaboration 33,500 Milestone payment received: Year-ended December 31, 2014 25,000 Expense reimbursement from Sanofi Genzyme: Year-ended December 31, 2015 33,949 Year-ended December 31, 2016 54,337 Quarter-ended March 31, 2017 13,012 Quarter-ended June 30, 2017 15,037 Total consideration at June 30, 2017 $ 123,385 Cumulative revenue recognized at June 30, 2017 $ 70,041 Deferred revenue at June 30, 2017 $ 53,344 We determined that the opt-in rights that Sanofi Genzyme has for future Genetic Medicine programs represent separate and additional deliverables that Sanofi Genzyme may receive from us in future periods. Upon each initial opt-in by Sanofi Genzyme, we have determined that each program and the related activities will represent a single unit of accounting and, consistent with our accounting policies, we will base our revenue recognition period on the final deliverable associated with each future opt-in.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	3. FAIR VALUE MEASUREMENTS The following tables present information about our assets that are measured at fair value on a recurring basis at June 30, 2017 and December 31, 2016, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value, in thousands: Description At June 30, 2017 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Commercial paper $ 3,990 $ — $ 3,990 $ — U.S. government-sponsored enterprise securities 7,987 — 7,987 — Money market funds 373,415 373,415 — — Marketable securities (fixed income): Certificates of deposit 12,900 — 12,900 — Commercial paper 62,758 — 62,758 — Corporate notes 269,009 — 269,009 — U.S. government-sponsored enterprise securities 304,518 — 304,518 — U.S. treasury securities 39,985 — 39,985 — Restricted cash (money market funds) 1,471 1,471 — — Total $ 1,076,033 $ 374,886 $ 701,147 $ — Description At December 31, 2016 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Commercial paper $ 17,199 $ — $ 17,199 $ — Money market funds 151,479 151,479 — — Marketable securities (fixed income): Certificates of deposit 17,999 — 17,999 — Commercial paper 59,340 — 59,340 — Corporate notes 333,872 — 333,872 — U.S. government-sponsored enterprise securities 297,773 — 297,773 — U.S. treasury securities 40,000 — 40,000 — Marketable securities (Regulus equity holdings) 8,997 8,997 — — Restricted cash (money market funds) 1,471 1,471 — — Total $ 928,130 $ 161,947 $ 766,183 $ — During the six months ended June 30, 2017, there were no transfers between Level 1 and Level 2 financial assets. The carrying amounts reflected in our condensed consolidated balance sheets for cash, billed and unbilled collaboration receivables, other current assets, accounts payable and accrued expenses approximate fair value due to their short-term maturities. The fair value of our long-term debt at , computed pursuant to a discounted cash flow technique using a market interest rate, was $150.2 million and is considered a Level 3 fair value measurement. The effective interest rate reflects the current market rate.

MARKETABLE SECURITIES

MARKETABLE SECURITIES	6 Months Ended
	Jun. 30, 2017
Investments Debt And Equity Securities [Abstract]
MARKETABLE SECURITIES	4. MARKETABLE SECURITIES The following tables summarize the fair value, accumulated other comprehensive income (loss) and intraperiod tax allocation regarding our investment in Regulus available-for-sale marketable securities at June 30, 2017 and 2016, and for the activity recorded for the three months ended June 30, 2017 and 2016, in thousands: Description At March 31, 2017 Sales of Regulus Shares During Three Months Ended June 30, 2017 All Other Activity During Three Months Ended June 30, 2017 Balance at June 30, 2017 Carrying value $ 2,682 $ (2,682 ) $ — $ — Accumulated other comprehensive income (loss), before tax — 345 (345 ) — Investment in equity securities of Regulus, as reported $ 2,682 $ (2,337 ) $ (345 ) $ — Accumulated other comprehensive income (loss), before tax $ — $ 345 $ (345 ) $ — Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (32,792 ) $ 345 $ (345 ) $ (32,792 ) Description At March 31, 2016 Sales of Regulus Shares During Three Months Ended June 30, 2016 All Other Activity During Three Months Ended June 30, 2016 Balance at June 30, 2016 Carrying value $ 9,911 $ (574 ) $ — $ 9,337 Accumulated other comprehensive income (loss), before tax 24,023 (954 ) (19,074 ) 3,995 Investment in equity securities of Regulus, as reported $ 33,934 $ (1,528 ) $ (19,074 ) $ 13,332 Accumulated other comprehensive income (loss), before tax $ 24,023 $ (954 ) $ (19,074 ) $ 3,995 Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (8,769 ) $ (954 ) $ (19,074 ) $ (28,797 ) The following tables summarize the fair value, accumulated other comprehensive income (loss) and intraperiod tax allocation regarding our investment in Regulus available-for-sale marketable securities at June 30, 2017 and 2016, and for the activity recorded for the six months ended June 30, 2017 and 2016, in thousands: Description At December 31, 2016 Sales of Regulus Shares During Six Months Ended June 30, 2017 All Other Activity During Six Months Ended June 30, 2017 Balance at June 30, 2017 Carrying value $ 8,093 $ (7,485 ) $ (608 ) $ — Accumulated other comprehensive income (loss), before tax 904 1,894 (2,798 ) — Investment in equity securities of Regulus, as reported $ 8,997 $ (5,591 ) $ (3,406 ) $ — Accumulated other comprehensive income (loss), before tax $ 904 $ 1,894 $ (2,798 ) $ — Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (31,888 ) $ 1,894 $ (2,798 ) $ (32,792 ) Description At Sales of Regulus Shares During Six Months Ended June 30, 2016 All Other Activity During Six Months Ended June 30, 2016 Balance at June 30, 2016 Carrying value $ 11,935 $ (2,598 ) $ — $ 9,337 Accumulated other comprehensive income (loss), before tax 39,484 (6,110 ) (29,379 ) 3,995 Investment in equity securities of Regulus, as reported $ 51,419 $ (8,708 ) $ (29,379 ) $ 13,332 Accumulated other comprehensive income (loss), before tax $ 39,484 $ (6,110 ) $ (29,379 ) $ 3,995 Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ 6,692 $ (6,110 ) $ (29,379 ) $ (28,797 ) We obtain fair value measurement data for our marketable securities from independent pricing services. We perform validation procedures to ensure the reasonableness of this data. This includes meeting with the independent pricing services to understand the methods and data sources used. Additionally, we perform our own review of prices received from the independent pricing services by comparing these prices to other sources and confirming those securities are trading in active markets. The following tables summarize our marketable securities, other than our holdings in Regulus noted above, at June 30, 2017 and December 31, 2016, in thousands: At June 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 12,900 $ — $ — $ 12,900 Commercial paper 62,761 — (3 ) 62,758 Corporate notes 269,265 30 (286 ) 269,009 U.S. government-sponsored enterprise securities 305,400 1 (883 ) 304,518 U.S. treasury securities 40,011 — (26 ) 39,985 Total $ 690,337 $ 31 $ (1,198 ) $ 689,170 At December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 17,999 $ — $ — $ 17,999 Commercial paper 59,340 — — 59,340 Corporate notes 334,266 47 (441 ) 333,872 U.S. government-sponsored enterprise securities 298,910 9 (1,146 ) 297,773 U.S. treasury securities 40,022 1 (23 ) 40,000 Total $ 750,537 $ 57 $ (1,610 ) $ 748,984 We classify our debt security investments based on their contractual maturity dates. The following table summarizes our available-for-sale debt securities by contractual maturity, at June 30, 2017, in thousands: At June 30, 2017 Amortized Cost Fair Value Less than one year $ 515,123 $ 514,600 Greater than one year but less than two years 175,214 174,570 Total $ 690,337 $ 689,170

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	5. COMMITMENTS AND CONTINGENCIES Manufacturing Facility In February 2016, we entered into an agreement with 20 Commerce LLC to purchase 12 acres of undeveloped land in Norton, Massachusetts. We completed the purchase and closed this transaction on April 4, 2016. We are constructing a manufacturing facility at this site for drug substance, including small interfering RNAs, or siRNAs, and siRNA conjugates, for clinical and commercial use. At June 30, 2017 and December 31, 2016, property, plant and equipment, net, on our condensed consolidated balance sheets reflects $105.3 million and $73.2 million, respectively, of land and associated costs related to the construction of our drug substance manufacturing facility. Credit Agreements On April 29, 2016, we entered into term loan agreements with two lenders for an aggregate of $150.0 million, with Alnylam U.S., Inc., our wholly-owned subsidiary, as the borrower, and us, as a guarantor, which mature on April 29, 2021, referred to as the Credit Agreements. The Credit Agreements were entered into in connection with the planned build out of our new drug substance manufacturing facility. The proceeds of the borrowing under each of the Credit Agreements are to be used for working capital and general corporate purposes. Interest on borrowings under the Credit Agreements is calculated based on LIBOR plus 0.45 percent, except in the event of default. The borrower may prepay loans under each of the Credit Agreements at any time, without premium or penalty, subject to certain notice requirements and LIBOR breakage costs. The obligations of the borrower under each Credit Agreement are guaranteed by us. The obligations of the borrower and us under each Credit Agreement are secured by cash collateral in an amount equal to, at any given time, at least 100 percent of the principal amount of all term loans outstanding under such Credit Agreement at such time. At each of June 30, 2017 and December 31, 2016, we have recorded $150.0 million of cash collateral in connection with the Credit Agreements as restricted investments on our condensed consolidated balance sheets. Each Credit Agreement contains limited representations and warranties and limited affirmative and negative covenants, including quarterly reporting obligations, as well as certain customary events of default. During the three and six months ended June 30, 2017, we recorded $0.4 million and $0.8 million, respectively, of interest expense related to the Credit Agreements that is reflected in other income (expense) on our condensed consolidated statements of comprehensive loss. During the three and six months ended June 30, 2016, we recorded $0.7 million of interest expense related to the Credit Agreements that is reflected in other income (expense) on our condensed consolidated statements of comprehensive loss. Litigation From time to time, we are a party to legal proceedings in the course of our business, including the matter described below. The claims and legal proceedings in which we could be involved include challenges to the scope, validity or enforceability of patents relating to our product candidates, and challenges by us to the scope, validity or enforceability of the patents held by others. These include claims by third parties that we infringe their patents. The outcome of any such legal proceedings, regardless of the merits, is inherently uncertain. In addition, litigation and related matters are costly and may divert the attention of our management and other resources that would otherwise be engaged in other activities. If we were unable to prevail in any such legal proceedings, our business, results of operations, liquidity and financial condition could be adversely affected Dicerna Litigation On June 10, 2015, we filed a trade secret misappropriation lawsuit against Dicerna, in the Superior Court of Middlesex County, Massachusetts, seeking to stop misappropriation by Dicerna of our confidential, proprietary and trade secret information related to the RNAi assets we purchased from Merck, including certain N-acetylgalactosamine, or GalNAc, conjugate technology. In addition to permanent injunctive relief, we are also seeking monetary damages from Dicerna. On July 10, 2015, Dicerna filed its answer to our complaint, in which it denied our claims, along with initial discovery requests, to which we responded in a timely fashion. On July 27, 2015, Dicerna filed a motion seeking removal of the case to the Business Litigation Session of the Superior Court of Suffolk County, which we opposed. On August 31, 2015, the Court denied Dicerna’s motion. We and Dicerna agreed to a protective order, which was entered by the Court on November 12, 2015. On June 7, 2017, Dicerna filed a motion requesting leave of the Court to amend its answer to our complaint to add counterclaims alleging abuse of process, tortious interference and unfair trade practices and seeking unspecified damages. We opposed the motion and do not believe the claims alleged by Dicerna are meritorious. Following a hearing on August 1, 2017, the Court granted Dicerna’s motion to amend its answer to add its counterclaims. To the extent such claims are not dismissed or struck, we intend to vigorously defend against such claims. Fact discovery on our claims against Dicerna is expected to close in August 2017, while fact discovery on issues related to Dicerna’s counterclaims will continue until December 2017. The trial for this lawsuit now is scheduled for April 2018. In addition, on August 8, 2017, Dicerna filed a new complaint in the United States District Court for the District of Massachusetts asserting a claim for attempted monopolization under the Sherman Antitrust Act. Dicerna’s allegations related to its new claim largely overlap with its counterclaims in the state court action. The new complaint has not yet been served and no schedule has been set. We do not believe the claim is meritorious and intend to vigorously defend against the claim. Although we believe we have meritorious claims against Dicerna and meritorious defenses and responses to the counterclaims and new federal claim now being asserted by Dicerna, as noted above, litigation is subject to inherent uncertainty and a court could ultimately rule against us.

SUMMARY OF SIGNIFICANT ACCOUN12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements of Alnylam Pharmaceuticals, Inc. are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, applicable to interim periods and, in the opinion of management, include all normal and recurring adjustments that are necessary to present fairly the results of operations for the reported periods. Our condensed consolidated financial statements have also been prepared on a basis substantially consistent with, and should be read in conjunction with, our audited consolidated financial statements for the year ended December 31, 2016, which were included in our Annual Report on Form 10-K that was filed with the Securities and Exchange Commission, or SEC, on February 15, 2017. The year-end condensed consolidated balance sheet data was derived from our audited financial statements, but does not include all disclosures required by GAAP. The results of our operations for any interim period are not necessarily indicative of the results of our operations for any other interim period or for a full fiscal year. The accompanying condensed consolidated financial statements reflect the operations of Alnylam and our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Liquidity	Liquidity Based on our current operating plan, we believe that our cash, cash equivalents and fixed income marketable securities at June 30, 2017, together with the cash we expect to generate under our current alliances, will be sufficient to enable us to advance our Alnylam 2020
Net Loss Per Common Share	Net Loss Per Common Share We compute basic net loss per common share by dividing net loss by the weighted-average number of common shares outstanding. We compute diluted net loss per common share by dividing net loss by the weighted-average number of common shares and dilutive potential common share equivalents then outstanding. Potential common shares consist of shares issuable upon the exercise of stock options (the proceeds of which are then assumed to have been repurchased using the treasury stock method). Because the inclusion of potential common shares would be anti-dilutive for all periods presented, diluted net loss per common share is the same as basic net loss per common share. The following table sets forth for the periods presented the potential common shares (prior to consideration of the treasury stock method) excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive, in thousands: At June 30, 2017 2016 Options to purchase common stock 12,372 10,377 Unvested restricted common stock 172 179 12,544 10,556
Public Offering	Public Offering In May 2017, we sold an aggregate of 5,000,000 shares of our common stock through an underwritten public offering at a price to the public of $71.87 per share. As a result of the offering, we received aggregate net proceeds of $355.2 million after deducting underwriting discounts and commissions and other offering expenses of $4.2 million.
Equity	Equity Total stockholders’ equity at June 30, 2017 increased by $202.7 million compared to December 31, 2016. This increase was related primarily to increases to additional paid-in capital due to our public offering in May 2017, our issuance of common stock to Sanofi Genzyme in May 2017 and stock-based compensation, partially offset during the six months ended June 30, 2017 by our net loss.
Fair Value Measurements	Fair Value Measurements The fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs utilize data points that are observable, such as quoted prices (adjusted), interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. The fair value hierarchy level is determined by the lowest level of significant input.
Investments in Marketable Securities and Cash Equivalents	Investments in Marketable Securities and Cash Equivalents We invest our excess cash balances in short-term and long-term marketable debt and equity securities. We classify our investments in marketable debt securities as either held-to-maturity or available-for-sale based on facts and circumstances present at the time we purchased the securities. At each balance sheet date presented, we classified all of our investments in debt and equity securities as available-for-sale. We report available-for-sale investments at fair value at each balance sheet date and include any unrealized holding gains and losses (the adjustment to fair value) in accumulated other comprehensive income (loss), a component of stockholders’ equity. At June 30, 2017, the balance in our accumulated other comprehensive loss was composed solely of activity related to our available-for-sale marketable securities, including our investment in equity securities of Regulus Therapeutics Inc., or Regulus. Realized gains and losses are determined using the specific identification method and are included in other income (expense). We recognized $0.3 million of realized losses and $1.0 million of realized gains from sales of our Regulus available-for-sale securities as other income (expense) in our condensed consolidated statements of comprehensive loss during the three months ended June 30, 2017 and 2016, respectively. In addition, we recognized $1.9 million of realized losses and $6.1 million of realized gains from sales of our Regulus available-for-sale securities as other income (expense) in our condensed consolidated statements of comprehensive loss during the six months ended June 30, 2017 and 2016, respectively. If any adjustment to arrive at fair value reflects a decline in the value of the investment, we consider all available evidence to evaluate the extent to which the decline is “other than temporary,” including our intention to sell and, if so, record a charge to our condensed consolidated statements of comprehensive loss. We did not record any impairment charges related to our fixed income marketable securities during the six months ended June 30, 2017 or 2016. Our marketable securities are classified as cash equivalents if the original maturity, from the date of purchase, is 90 days or less, and as marketable securities if the original maturity, from the date of purchase, is in excess of 90 days. Our cash equivalents are composed of commercial paper, money market funds, and U.S. government-sponsored enterprise securities During the second quarter of 2017, we sold all our remaining holdings in Regulus. We accounted for our investment in Regulus as an available-for-sale marketable security. Intraperiod tax allocation rules require us to allocate our provision for income taxes between continuing operations and other categories of earnings, such as other comprehensive income. In periods in which we have a year-to-date pre-tax loss from continuing operations and pre-tax income in other categories of earnings, such as other comprehensive income, we must allocate the tax provision to the other categories of earnings. We then record a related tax benefit in continuing operations. Upon sales of our available-for-sale marketable securities, we apply the aggregate portfolio approach to recognize the related tax provision or benefit into income (loss) from continuing operations. As a result, the disproportionate tax effect remains in accumulated other comprehensive income (loss) as long as we maintain an investment portfolio.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued a new revenue recognition standard which amends revenue recognition principles and provides a single, comprehensive set of criteria for revenue recognition within and across all industries. The new standard provides a five step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires enhanced disclosures pertaining to revenue recognition in both interim and annual periods. In August 2015, the FASB deferred the effective date of the new revenue standard from January 1, 2017 to January 1, 2018. In March 2016, the FASB issued amendments to clarify the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued amendments to clarify the guidance on accounting for licenses of intellectual property and identifying performance obligations. In May 2016, the FASB issued amendments related to collectibility, non-cash consideration, the presentation of sales and other similar taxes collected from customers and transition. The standard allows for adoption using a full retrospective method or a modified retrospective method. We plan to adopt this standard using the modified retrospective method. During the second half of 2017, we plan to complete our review of our revenue streams to determine the impact that this standard could have on our condensed consolidated financial statements and related disclosures. In January 2016, the FASB issued new guidance on recognition and measurement of financial assets and financial liabilities. The new guidance will impact the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. All equity investments in unconsolidated entities (other than those accounted for under the equity method of accounting) will generally be measured at fair value with changes in fair value recognized through earnings. There will no longer be an available-for-sale classification (changes in fair value reported in other comprehensive income (loss)) for equity securities with readily determinable fair values. In addition, the FASB clarified the need for a valuation allowance on deferred tax assets resulting from unrealized losses on available-for-sale debt securities. In general, the new guidance will require modified retrospective application to all outstanding instruments, with a cumulative effect adjustment recorded to opening retained earnings. This guidance will be effective for us on January 1, 2018. We are currently evaluating the expected impact that the standard could have on our condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued a new leasing standard that requires that all lessees recognize the assets and liabilities that arise from leases on the condensed consolidated balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for us on January 1, 2019. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In October 2016, the FASB issued guidance that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs instead of deferring the income tax effects. The new standard will be effective for us on a modified retrospective basis on January 1, 2018. We are currently evaluating the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In November 2016, the FASB issued guidance that requires restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. The new standard will be effective for us on January 1, 2018 using a retrospective transition method to each period presented. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In March 2017, the FASB issued guidance that amends the amortization period for certain purchased callable debt securities held at a premium by shortening the amortization period for the premium to the earliest call date. The new standard will be effective for us on January 1, 2019. Early adoption is permitted. We are currently evaluating the timing of our adoption and the expected impact that this standard could have on our condensed consolidated financial statements and related disclosures. In May 2017, the FASB issued guidance that clarifies when changes to the terms or conditions of share-based payment awards must be accounted for as modifications. The new standard will be applied prospectively to awards modified on or after the adoption date and will be effective for us on January 1, 2018. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on our condensed consolidated financial statements and related disclosures.
Subsequent Event	Subsequent Event We did not have any material recognized subsequent events. However, we did have the following nonrecognized subsequent event, which is more fully described in Note 5. • On August 8, 2017, Dicerna Pharmaceuticals, Inc., or Dicerna, filed a new complaint in the United States District Court for the District of Massachusetts asserting a claim for attempted monopolization under the Sherman Antitrust Act.

SUMMARY OF SIGNIFICANT ACCOUN13

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Common Shares Excluded from the Calculation of Net Loss Per Common Share	The following table sets forth for the periods presented the potential common shares (prior to consideration of the treasury stock method) excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive, in thousands: At June 30, 2017 2016 Options to purchase common stock 12,372 10,377 Unvested restricted common stock 172 179 12,544 10,556

COLLABORATION AGREEMENTS (Table

COLLABORATION AGREEMENTS (Tables)	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Revenue from Collaborators	The following table summarizes our total consolidated net revenues from collaborators, for the periods indicated, in thousands: Three Months Ended June 30, Six Months Ended June 30, Description 2017 2016 2017 2016 Sanofi Genzyme $ 14,375 $ 5,387 $ 26,652 $ 9,802 The Medicines Company 1,522 3,268 7,886 5,925 Other 35 54 354 327 Total net revenues from collaborators $ 15,932 $ 8,709 $ 34,892 $ 16,054
Information Related to 2014 Sanofi Genzyme Collaboration	The following table presents information related to the 2014 Sanofi Genzyme collaboration, in thousands: Excess of fair value of our common stock issued to Sanofi Genzyme in February 2014 $ (51,450 ) Deferred revenue remaining under the 2012 Sanofi Genzyme agreement upon execution of the 2014 Sanofi Genzyme collaboration 33,500 Milestone payment received: Year-ended December 31, 2014 25,000 Expense reimbursement from Sanofi Genzyme: Year-ended December 31, 2015 33,949 Year-ended December 31, 2016 54,337 Quarter-ended March 31, 2017 13,012 Quarter-ended June 30, 2017 15,037 Total consideration at June 30, 2017 $ 123,385 Cumulative revenue recognized at June 30, 2017 $ 70,041 Deferred revenue at June 30, 2017 $ 53,344

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Assets Measured on a Recurring Basis	The following tables present information about our assets that are measured at fair value on a recurring basis at June 30, 2017 and December 31, 2016, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value, in thousands: Description At June 30, 2017 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Commercial paper $ 3,990 $ — $ 3,990 $ — U.S. government-sponsored enterprise securities 7,987 — 7,987 — Money market funds 373,415 373,415 — — Marketable securities (fixed income): Certificates of deposit 12,900 — 12,900 — Commercial paper 62,758 — 62,758 — Corporate notes 269,009 — 269,009 — U.S. government-sponsored enterprise securities 304,518 — 304,518 — U.S. treasury securities 39,985 — 39,985 — Restricted cash (money market funds) 1,471 1,471 — — Total $ 1,076,033 $ 374,886 $ 701,147 $ — Description At December 31, 2016 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Commercial paper $ 17,199 $ — $ 17,199 $ — Money market funds 151,479 151,479 — — Marketable securities (fixed income): Certificates of deposit 17,999 — 17,999 — Commercial paper 59,340 — 59,340 — Corporate notes 333,872 — 333,872 — U.S. government-sponsored enterprise securities 297,773 — 297,773 — U.S. treasury securities 40,000 — 40,000 — Marketable securities (Regulus equity holdings) 8,997 8,997 — — Restricted cash (money market funds) 1,471 1,471 — — Total $ 928,130 $ 161,947 $ 766,183 $ —

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2017
Investments Debt And Equity Securities [Abstract]
Summary of Fair Value Accumulated Other Comprehensive Income (Loss) and Intraperiod Tax Allocation in Regulus Available-for-Sale Marketable Securities	The following tables summarize the fair value, accumulated other comprehensive income (loss) and intraperiod tax allocation regarding our investment in Regulus available-for-sale marketable securities at June 30, 2017 and 2016, and for the activity recorded for the three months ended June 30, 2017 and 2016, in thousands: Description At March 31, 2017 Sales of Regulus Shares During Three Months Ended June 30, 2017 All Other Activity During Three Months Ended June 30, 2017 Balance at June 30, 2017 Carrying value $ 2,682 $ (2,682 ) $ — $ — Accumulated other comprehensive income (loss), before tax — 345 (345 ) — Investment in equity securities of Regulus, as reported $ 2,682 $ (2,337 ) $ (345 ) $ — Accumulated other comprehensive income (loss), before tax $ — $ 345 $ (345 ) $ — Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (32,792 ) $ 345 $ (345 ) $ (32,792 ) Description At March 31, 2016 Sales of Regulus Shares During Three Months Ended June 30, 2016 All Other Activity During Three Months Ended June 30, 2016 Balance at June 30, 2016 Carrying value $ 9,911 $ (574 ) $ — $ 9,337 Accumulated other comprehensive income (loss), before tax 24,023 (954 ) (19,074 ) 3,995 Investment in equity securities of Regulus, as reported $ 33,934 $ (1,528 ) $ (19,074 ) $ 13,332 Accumulated other comprehensive income (loss), before tax $ 24,023 $ (954 ) $ (19,074 ) $ 3,995 Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (8,769 ) $ (954 ) $ (19,074 ) $ (28,797 ) The following tables summarize the fair value, accumulated other comprehensive income (loss) and intraperiod tax allocation regarding our investment in Regulus available-for-sale marketable securities at June 30, 2017 and 2016, and for the activity recorded for the six months ended June 30, 2017 and 2016, in thousands: Description At December 31, 2016 Sales of Regulus Shares During Six Months Ended June 30, 2017 All Other Activity During Six Months Ended June 30, 2017 Balance at June 30, 2017 Carrying value $ 8,093 $ (7,485 ) $ (608 ) $ — Accumulated other comprehensive income (loss), before tax 904 1,894 (2,798 ) — Investment in equity securities of Regulus, as reported $ 8,997 $ (5,591 ) $ (3,406 ) $ — Accumulated other comprehensive income (loss), before tax $ 904 $ 1,894 $ (2,798 ) $ — Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ (31,888 ) $ 1,894 $ (2,798 ) $ (32,792 ) Description At Sales of Regulus Shares During Six Months Ended June 30, 2016 All Other Activity During Six Months Ended June 30, 2016 Balance at June 30, 2016 Carrying value $ 11,935 $ (2,598 ) $ — $ 9,337 Accumulated other comprehensive income (loss), before tax 39,484 (6,110 ) (29,379 ) 3,995 Investment in equity securities of Regulus, as reported $ 51,419 $ (8,708 ) $ (29,379 ) $ 13,332 Accumulated other comprehensive income (loss), before tax $ 39,484 $ (6,110 ) $ (29,379 ) $ 3,995 Intraperiod tax allocation recorded as a benefit from income taxes (32,792 ) — — (32,792 ) Accumulated other comprehensive income (loss), net of tax $ 6,692 $ (6,110 ) $ (29,379 ) $ (28,797 )
Summary of Company's Marketable Securities Excluding Regulus	The following tables summarize our marketable securities, other than our holdings in Regulus noted above, at June 30, 2017 and December 31, 2016, in thousands: At June 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 12,900 $ — $ — $ 12,900 Commercial paper 62,761 — (3 ) 62,758 Corporate notes 269,265 30 (286 ) 269,009 U.S. government-sponsored enterprise securities 305,400 1 (883 ) 304,518 U.S. treasury securities 40,011 — (26 ) 39,985 Total $ 690,337 $ 31 $ (1,198 ) $ 689,170 At December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 17,999 $ — $ — $ 17,999 Commercial paper 59,340 — — 59,340 Corporate notes 334,266 47 (441 ) 333,872 U.S. government-sponsored enterprise securities 298,910 9 (1,146 ) 297,773 U.S. treasury securities 40,022 1 (23 ) 40,000 Total $ 750,537 $ 57 $ (1,610 ) $ 748,984
Summary of Available-For-Sale Debt Securities by Contractual Maturity	The following table summarizes our available-for-sale debt securities by contractual maturity, at June 30, 2017, in thousands: At June 30, 2017 Amortized Cost Fair Value Less than one year $ 515,123 $ 514,600 Greater than one year but less than two years 175,214 174,570 Total $ 690,337 $ 689,170

Potential Common Shares Exclude

Potential Common Shares Excluded from Calculation of Net Loss Per Common Share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	12,544	10,556
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	12,372	10,377
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	172	179

Summary of Significant Accoun18

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Issuance of common stock, net of offering costs (in shares)	5,000,000
Underwritten public offering amount per share	$ 71.87
Issuance of common stock, net of offering costs	$ 355,200
Underwriting discounts and commissions and other estimated offering expenses	$ 4,200
Stockholders' equity, increase				$ 202,700
Realized gain (loss) on sale of marketable securities		$ (345)	$ 954	$ (1,894)	$ 6,110
Marketable securities classified as cash equivalents, maximum original maturity				90 days
Policy for marketable securities				90 days

Revenue from Collaborators (Det

Revenue from Collaborators (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net revenues from collaborators	$ 15,932	$ 8,709	$ 34,892	$ 16,054
Sanofi Genzyme
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net revenues from collaborators	14,375	5,387	26,652	9,802
The Medicines Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net revenues from collaborators	1,522	3,268	7,886	5,925
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net revenues from collaborators	$ 35	$ 54	$ 354	$ 327

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Detail) - USD ($)

Feb. 01, 2016

Jan. 22, 2015

Jan. 14, 2014

Oct. 31, 2012

May 31, 2017

Jan. 31, 2017

Oct. 31, 2016

Jan. 31, 2015

Mar. 31, 2014

Feb. 28, 2014

Dec. 31, 2014

Dec. 31, 2013

Jun. 30, 2017

Jun. 30, 2016

Sep. 30, 2016

Dec. 31, 2014

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Issuance of common stock, net of offering costs (in shares)

5,000,000

Proceeds from issuance of common stock to Sanofi Genzyme

$ 21,381,000

$ 14,301,000

Common stock price

$ 71.87

Sanofi Genzyme

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Amount earned upon achievement of milestone

$ 25,000,000

Deferred revenue

$ 53,344,000

Issuance of common stock, net of offering costs (in shares)

344,448

8,766,338

Proceeds from issuance of common stock to Sanofi Genzyme

$ 23,000,000

$ 700,000,000

Common stock price

$ 85.72

Fair value of shares issued

$ 751,500,000

Excess of fair value over cash received for stock issuance

51,450,000

Provision for (Benefit from) income taxes

$ (15,200,000)

Percentage ownership interest owned by noncontrolling owners

12.00%

12.00%

12.00%

Sanofi Genzyme | Concurrent Private Placement

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Issuance of common stock, net of offering costs (in shares)

297,501

744,566

Proceeds from issuance of common stock to Sanofi Genzyme

$ 21,400,000

$ 70,700,000

Sanofi Genzyme | Compensatory Purposes

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Issuance of common stock, net of offering costs (in shares)

205,030

196,251

Proceeds from issuance of common stock to Sanofi Genzyme

$ 14,300,000

$ 18,300,000

Sanofi Genzyme | Product Alliances

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Upfront fee received

$ 22,500,000

Deferred revenue

$ 33,500,000

Sanofi Genzyme | Product Alliances | Patisiran and Revusiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Performance period

5 years

6 years

Sanofi Genzyme | Product Alliances | Fitusiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Performance period

5 years

Sanofi Genzyme | Product Alliances | Phase Two Clinical Trial ALN-TTR

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Amount earned upon achievement of milestone

7,000,000

Sanofi Genzyme | Product Alliances | Phase Three Clinical Trial

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Amount earned upon achievement of milestone

$ 4,000,000

Sanofi Genzyme | Regional Collaboration Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Percentage of sharing in development cost

20.00%

Potential future payment for the achievement of certain development milestones

$ 55,000,000

Maximum number of potential future milestones

75,000,000

Potential future payment for the achievement of specified commercialization milestones

$ 20,000,000

Royalty rate

20.00%

Sanofi Genzyme | Regional Collaboration Product | Patisiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Potential future payment for the achievement of certain development milestones

$ 50,000,000

Sanofi Genzyme | Regional Collaboration Product | Minimum | Patisiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Potential milestone payments to be earned

$ 5,000,000

Sanofi Genzyme | Regional Collaboration Product | Maximum | Patisiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Potential milestone payments to be earned

20,000,000

Sanofi Genzyme | Co-developed/ Co-commercialized Collaboration Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Percentage of sharing in development cost

50.00%

Maximum number of potential future milestones

$ 75,000,000

Royalty rate

20.00%

Received incremental share of co-development costs for exercise of right, fitusiran

$ 6,000,000

Expected first milestone payment to be received fitusiran

25,000,000

Sanofi Genzyme | Co-developed/ Co-commercialized Collaboration Product | Revusiran

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Amount earned upon achievement of milestone

$ 25,000,000

Sanofi Genzyme | Global Collaboration Product

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Percentage of sharing in development cost

100.00%

Potential future payment for the achievement of certain development milestones

100,000,000

Maximum number of potential future milestones

$ 200,000,000

Potential future payment for the achievement of specified commercialization milestones

$ 100,000,000

Royalty rate

20.00%

Information Related to 2014 San

Information Related to 2014 Sanofi Genzyme Collaboration (Detail) - Sanofi Genzyme - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Feb. 28, 2014	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Excess of fair value of our common stock issued to Sanofi Genzyme in February 2014	$ (51,450)
Deferred revenue		$ 53,344
Milestone payment received:
Milestone payment						$ 25,000
Expense reimbursement from Sanofi Genzyme:
Expense reimbursement		15,037	$ 13,012	$ 54,337	$ 33,949
Total consideration at June 30, 2017		123,385
Cumulative revenue recognized at June 30, 2017		$ 70,041
Product Alliances
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue							$ 33,500

Fair Value Measured on Recurrin

Fair Value Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	$ 689,170	$ 748,984
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale equity securities, Fair value disclosure		8,997
Total	1,076,033	928,130
Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale equity securities, Fair value disclosure		8,997
Total	374,886	161,947
Recurring | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	701,147	766,183
Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,990	17,199
Available for sale debt securities, Fair value disclosure	62,758	59,340
Recurring | Commercial paper | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,990	17,199
Available for sale debt securities, Fair value disclosure	62,758	59,340
Recurring | U.S. government-sponsored enterprise securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,987
Available for sale debt securities, Fair value disclosure	304,518	297,773
Recurring | U.S. government-sponsored enterprise securities | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,987
Available for sale debt securities, Fair value disclosure	304,518	297,773
Recurring | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	373,415	151,479
Restricted cash	1,471	1,471
Recurring | Money Market Funds | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	373,415	151,479
Restricted cash	1,471	1,471
Recurring | Certificate of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	12,900	17,999
Recurring | Certificate of deposit | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	12,900	17,999
Recurring | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	269,009	333,872
Recurring | Corporate notes | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	269,009	333,872
Recurring | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	39,985	40,000
Recurring | U.S. treasury securities | Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities, Fair value disclosure	$ 39,985	$ 40,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) $ in Millions	Jun. 30, 2017USD ($)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long-term debt	$ 150.2

Summary of Fair Value Accumulat

Summary of Fair Value Accumulated Other Comprehensive Income (Loss) and Intraperiod Tax Allocation in Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Accumulated other comprehensive income (loss), net of tax	$ (476)	$ (18,331)	$ (2,412)	$ (26,555)
Regulus Therapeutics Inc
Schedule of Available-for-sale Securities [Line Items]
Carrying value		9,337		9,337	$ 2,682	$ 8,093	$ 9,911	$ 11,935
Accumulated other comprehensive income (loss), before tax		3,995		3,995		904	24,023	39,484
Investment in equity securities of Regulus, as reported		13,332		13,332	2,682	8,997	33,934	51,419
Intraperiod tax allocation recorded as a benefit from income taxes	(32,792)	(32,792)	(32,792)	(32,792)	(32,792)	(32,792)	(32,792)	(32,792)
Accumulated other comprehensive income (loss), net of tax	(32,792)	(28,797)	(32,792)	(28,797)	$ (32,792)	$ (31,888)	$ (8,769)	$ 6,692
Regulus Therapeutics Inc | Sales of Regulus Shares
Schedule of Available-for-sale Securities [Line Items]
Carrying value	(2,682)	(574)	(7,485)	(2,598)
Accumulated other comprehensive income (loss), before tax	345	(954)	1,894	(6,110)
Investment in equity securities of Regulus, as reported	(2,337)	(1,528)	(5,591)	(8,708)
Accumulated other comprehensive income (loss), net of tax	345	(954)	1,894	(6,110)
Regulus Therapeutics Inc | All Other Activity
Schedule of Available-for-sale Securities [Line Items]
Carrying value			(608)
Accumulated other comprehensive income (loss), before tax	(345)	(19,074)	(2,798)	(29,379)
Investment in equity securities of Regulus, as reported	(345)	(19,074)	(3,406)	(29,379)
Accumulated other comprehensive income (loss), net of tax	$ (345)	$ (19,074)	$ (2,798)	$ (29,379)

Summary of Company's Marketable

Summary of Company's Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 690,337	$ 750,537
Gross Unrealized Gains	31	57
Gross Unrealized Losses	(1,198)	(1,610)
Fair Value	689,170	748,984
Certificate of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,900	17,999
Fair Value	12,900	17,999
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,761	59,340
Gross Unrealized Losses	(3)
Fair Value	62,758	59,340
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	269,265	334,266
Gross Unrealized Gains	30	47
Gross Unrealized Losses	(286)	(441)
Fair Value	269,009	333,872
U.S. government-sponsored enterprise securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	305,400	298,910
Gross Unrealized Gains	1	9
Gross Unrealized Losses	(883)	(1,146)
Fair Value	304,518	297,773
U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	40,011	40,022
Gross Unrealized Gains		1
Gross Unrealized Losses	(26)	(23)
Fair Value	$ 39,985	$ 40,000

Summary of Available-For-Sale D

Summary of Available-For-Sale Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Less than one year	$ 515,123
Greater than one year but less than two years	175,214
Amortized Cost	690,337	$ 750,537
Fair Value
Less than one year	514,600
Greater than one year but less than two years	174,570
Total	$ 689,170	$ 748,984

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Apr. 29, 2016USD ($)Lender	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Apr. 04, 2016a
Commitments and Contingencies [Line Items]
Property, plant and equipment, net		$ 147,533,000		$ 147,533,000		$ 114,572,000
Restricted investments		150,000,000		150,000,000		150,000,000
Term Loan Facility | Other Income (Expense)
Commitments and Contingencies [Line Items]
Interest expense		400,000	$ 700,000	800,000	$ 700,000
Term Loan Agreement
Commitments and Contingencies [Line Items]
Number of lenders | Lender	2
Line of credit facility, maximum borrowing capacity	$ 150,000,000
Line of credit facility, expiration date	Apr. 29, 2021
Cash collateral required for principal amount outstanding, percentage	100.00%
Term Loan Agreement | LIBOR
Commitments and Contingencies [Line Items]
Debt instrument, basis spread on variable rate	0.45%
Norton, Massachusetts
Commitments and Contingencies [Line Items]
Undeveloped land acquired | a							12
Norton, Massachusetts | Land and costs related to the construction of manufacturing facility
Commitments and Contingencies [Line Items]
Property, plant and equipment, net		$ 105,300,000		$ 105,300,000		$ 73,200,000