Dicerna Pharmaceuticals (DRNA) 10-Q 8 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 06, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	DRNA
Entity Registrant Name	DICERNA PHARMACEUTICALS INC
Entity Central Index Key	1,399,529
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		52,949,660

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 42,426,000	$ 68,789,000
Held-to-maturity investments	39,875,000	44,889,000
Withholding tax receivable	1,583,000	1,583,000
Prepaid expenses and other current assets	3,728,000	3,415,000
Total current assets	87,612,000	118,676,000
NONCURRENT ASSETS:
Property and equipment—net	1,293,000	1,512,000
Restricted cash equivalents	744,000	744,000
Other noncurrent assets	66,000	70,000
Total noncurrent assets	2,103,000	2,326,000
TOTAL ASSETS	89,715,000	121,002,000
CURRENT LIABILITIES:
Accounts payable	3,757,000	4,920,000
Accrued expenses and other current liabilities	6,299,000	5,726,000
Current portion of deferred revenue	6,180,000	6,180,000
Total current liabilities	16,236,000	16,826,000
NONCURRENT LIABILITIES:
Long-term payable and accrued interest	8,904,000
Deferred revenue, net of current portion	0	3,090,000
Total noncurrent liabilities	8,904,000	3,090,000
TOTAL LIABILITIES	25,140,000	19,916,000
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS’ EQUITY:
Preferred stock, $0.0001 par value—5,000,000 shares authorized; no shares issued or outstanding at June 30, 2018 or December 31, 2017
Common stock, $0.0001 par value—150,000,000 shares authorized; 52,867,771 and 51,644,841 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	5,000	5,000
Additional paid-in capital	431,749,000	417,037,000
Accumulated deficit	(367,179,000)	(315,956,000)
Total stockholders’ equity	64,575,000	101,086,000
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 89,715,000	$ 121,002,000

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
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	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	52,867,771	51,644,841
Common stock, shares outstanding	52,867,771	51,644,841

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue from collaborative arrangements	$ 1,545		$ 3,090
Operating expenses:
Research and development	10,339	$ 9,068	20,232	$ 17,811
General and administrative	4,760	4,066	9,095	8,188
Litigation expense	22,244	2,234	25,428	3,608
Total operating expenses	37,343	15,368	54,755	29,607
Loss from operations	(35,798)	(15,368)	(51,665)	(29,607)
Other income (expense):
Interest income	330	143	619	181
Interest expense	(176)		(176)
Total other income, net	154	143	443	181
Net loss	(35,644)	(15,225)	(51,222)	(29,426)
Dividends on redeemable convertible preferred stock		(2,622)		(2,622)
Deemed dividend related to beneficial conversion feature of redeemable convertible preferred stock		(6,144)		(6,144)
Net loss attributable to common stockholders	$ (35,644)	$ (23,991)	$ (51,222)	$ (38,192)
Net loss per share attributable to common stockholders— basic and diluted	$ (0.68)	$ (1.15)	$ (0.98)	$ (1.84)
Weighted average common shares outstanding—basic and diluted	52,555,751	20,794,193	52,141,849	20,792,925

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (51,222)	$ (29,426)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash litigation expense	10,315
Stock-based compensation	3,525	4,033
Depreciation	393	363
Loss on disposal of property and equipment		51
Amortization of (discount)/premium on investments	(195)	(35)
Changes in operating assets and liabilities:
Long-term payable	8,904
Deferred revenue	(3,090)
Prepaid expenses and other assets	(313)	(1,013)
Accounts payable	(1,163)	(599)
Accrued expenses and other liabilities	573	(272)
Net cash used in operating activities	(32,273)	(26,898)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(173)	(58)
Maturities of held-to-maturity investments	35,000	25,000
Purchases of held-to-maturity investments	(29,790)	(49,908)
Net cash provided by (used in) investing activities	5,037	(24,966)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		69,700
Proceeds from stock option exercises and issuances under Employee Stock Purchase Plan	908	87
Settlement of restricted stock for tax withholding	(35)	(11)
Net cash provided by financing activities	873	69,776
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH EQUIVALENTS	(26,363)	17,912
CASH, CASH EQUIVALENTS AND RESTRICTED CASH EQUIVALENTS — Beginning of period	69,533	21,981
CASH, CASH EQUIVALENTS AND RESTRICTED CASH EQUIVALENTS — End of period	43,170	39,893
NONCASH FINANCING ACTIVITIES:
Dividends on redeemable convertible preferred stock		2,622
Deemed dividend related to beneficial conversion feature of redeemable preferred stock		6,144
Redeemable convertible preferred stock issuance costs included in accounts payable		$ 450
NONCASH INVESTING ACTIVITIES:
Property and equipment purchases included in accounts payable	$ 6

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Operating Cash Flows Direct Method [Abstract]
Cash and cash equivalents	$ 42,426	$ 68,789	$ 38,777
Restricted cash equivalents	744	744	1,116
Cash, cash equivalents and restricted cash equivalents presented above	$ 43,170	$ 69,533	$ 39,893	$ 21,981

Description of Business and Bas

Description of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Business Dicerna Pharmaceuticals, Inc. (“Dicerna” or the “Company”), a Delaware corporation founded in 2006 and located in Cambridge, Massachusetts, is a biopharmaceutical company focused on the discovery and development of innovative subcutaneously delivered ribonucleic acid interference (“RNAi”)-based pharmaceuticals using its GalXC TM Basis of presentation These condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, these condensed consolidated financial statements do not include all of the information and notes required by GAAP to constitute a complete set of financial statements. These condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position at June 30, 2018 and results of operations and cash flows for the interim periods ended June 30, 2018 and 2017. These unaudited condensed consolidated interim financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The results of the three and six months ended June 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year. Significant judgments and estimates The preparation of consolidated 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 Company’s consolidated financial statements, as well as the revenues and expenses incurred during the reporting periods. On an ongoing basis, the Company evaluates judgments and estimates, including those related to revenue recognition and accrued expenses. The Company bases its estimates on historical experience and on various other factors that the Company believes are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not apparent from other sources. Changes in estimates are reflected in reported results for the period in which they become known. Actual results could differ materially from those estimates. Liquidity Based on the Company’s current operating plan and liquidity, management believes that available cash, cash equivalents, and held-to-maturity investments will be sufficient to fund the Company’s planned level of operations for at least the 12-month period following, August 8, 2018, which is the date that these condensed consolidated financial statements have been issued. Notwithstanding the availability of current liquidity, the Company’s ability to fund its preclinical and clinical operations, including completion of its clinical trials, will depend on the Company’s ability to raise additional capital through a combination of public or private equity offerings, debt financings, and research collaborations and license agreements. If the Company is unable to generate funding from one or more of these sources within a reasonable timeframe, it may have to delay, reduce, or terminate its research and development programs, preclinical or clinical trials, limit strategic opportunities, or undergo reductions in its workforce or other corporate restructuring activities. Summary of Significant Accounting Policies — There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K, except as a result of adopting the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“Topic 606”), as discussed below. Revenue recognition The Company generates revenue from research collaboration and license agreements with third-party customers. Goods and services in the agreements typically include (i) the grant of licenses for the use of the Company’s technology and (ii) the provision of services associated with the research and development of customer product candidates. Such agreements may provide for consideration to the Company in the form of upfront payments, research and development services, option payments, milestone payments, and royalty payments on licensed products. The Company accounts for a contract when the Company has approval and commitment from both parties, when the rights of the parties are identified, when payment terms are identified, when the contract has commercial substance, and when collectability of consideration is probable. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, management completes the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations; (iii) measurement of the transaction price, including whether there are any constraints on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for the relevant arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the underlying contract. The Company uses key assumptions to determine the stand-alone selling price which may include, as applicable, relevant market data, forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, or probabilities of technical and regulatory success. Licenses of intellectual property: If a license granted to a customer to use the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from consideration allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company applies judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, to conclude upon the appropriate method of measuring progress for purposes of recognizing revenue related to consideration allocated to the performance obligation. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each contract with a customer that includes development or regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or of the licensee, such as regulatory approvals, are assessed as to the probability of achieving the related milestones. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of all milestones and any related constraint, and, if necessary, adjusts the estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis and are recorded as revenue and through earnings in the period of adjustment. Options: Customer options, such as options granted to allow a licensee to choose to research and develop product candidates against target genes to be identified in the future, generally do not provide a material right to the customer and therefore do not give rise to a separate performance obligation. As such, the additional consideration that would result from a customer exercising an option in the future is not included in the transaction price for the current contract. Instead, additional option fee payments are recognized or begin being recognized as revenue when the licensee exercises the options, and the exercise of the option would be treated as a separate contract for accounting purposes. Research and development services: Arrangements that include a promise to provide research or development services at the licensee’s discretion are assessed to determine whether the services provide a material right to the licensee and are capable of being distinct, are not highly interdependent or do not significantly modify one another, and if so, the services are accounted for as separate performance obligations as the services are provided to the customer. Otherwise, where research or development services are determined not to be capable of being distinct or distinct within the context of the contract, those services are added to the performance obligation that includes the underlying license. Royalties: For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, and when the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any out-licensing arrangement. The Company receives payments from its licensees as established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Where applicable, amounts are recorded as contracts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. Recent Accounting Pronouncements Adopted in 2018 Revenue recognition In May 2014, the FASB issued Topic 606, which amends the guidance for accounting for revenue from contracts with customers, superseding the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition Income taxes In October 2016, the FASB issued ASU No. 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory Statement of cash flows In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash Stock-based compensation In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting Not yet adopted Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Nonemployee stock-based compensation In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Compensation—Stock Compensation (Topic 718) Equity—Equity Based Payments to Nonemployees (Topic 505)

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	2. Net Loss Per Share The outstanding securities presented below were excluded from the calculation of net loss per share, because such securities would have been anti-dilutive due to the Company’s net loss per share during the periods ending on the dates presented. June 30, 2018 2017 Options to purchase common stock 7,556,554 6,212,437 Warrants to purchase common stock 2,198 87,901 Unvested restricted common stock — 10,000 Redeemable convertible preferred stock — 718,404 Total 7,558,752 7,028,742

Held-to-maturity Investments

Held-to-maturity Investments	6 Months Ended
	Jun. 30, 2018
Text Block [Abstract]
Held-to-maturity Investments	3. Held-to-maturity investments The following tables provide information relating to the Company’s held-to-maturity investments (amounts in thousands). Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value As of June 30, 2018: Held-to-maturity investments U.S. treasury securities maturing in one year or less $ 39,875 $ — $ (17 ) $ 39,858 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value As of December 31, 2017: Held-to-maturity investments U.S. treasury securities maturing in one year or less $ 44,889 $ — $ (30 ) $ 44,859

Stock Option Plan and Stock-Bas

Stock Option Plan and Stock-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Plan and Stock-Based Compensation	4. Stock Option Plan and Stock-Based Compensation During the three and six months ended June 30, 2018, the Company granted stock options to purchase 442,000 and 1,761,350 shares, respectively, of common stock to employees with aggregate grant date fair values of $3.8 million and $13.2 million, respectively, compared to stock options to purchase 352,500 and 1,330,997 shares of common stock granted to employees with aggregate grant date fair values of $0.7 million and $2.7 million, for the three and six months ended June 30, 2017, respectively. The assumptions used to estimate the grant date fair value using the Black-Scholes option pricing model were as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Common stock price $9.14 – $14.41 $9.14 – $14.41 Expected option term (in years) 5.50-6.25 5.50-6.25 Expected volatility 76.8% – 78.33% 75.89% –90.9% Risk-free interest rate 2.65% – 2.84% 2.32% – 2.84% Expected dividend yield 0.00% 0.00% Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Common stock price $2.91 – $3.47 $2.49 – $3.47 Expected option term (in years) 5.50-6.25 5.50-6.25 Expected volatility 79.7% – 80.8% 79.4% – 80.8% Risk-free interest rate 1.86% – 1.89% 1.86% – 2.07% Expected dividend yield 0.00% 0.00% The Company has classified stock-based compensation in its condensed consolidated statements of operations as follows (amounts in thousands): Three Months Ended June 30, Six Months Ended June 30, Three Months Ended June 30, Six Months Ended June 30, 2018 2018 2017 2017 Research and development expense $ 751 $ 1,557 $ 972 $ 1,917 General and administrative expenses 1,028 1,968 1,053 2,116 Total $ 1,779 $ 3,525 $ 2,025 $ 4,033

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. Fair Value Measurements A summary of the Company’s financial assets that are measured or disclosed at fair value on a recurring basis as of June 30, 2018 and December 31, 2017 are presented below (amounts in thousands). Description At June 30, 2018 Level 1 Level 2 Level 3 Cash equivalents Money market fund $ 38,258 $ 38,258 $ $ — Held-to-maturity investments U.S. treasury securities 39,858 — $ 39,858 — Restricted cash equivalents Money market fund 744 744 — Total $ 78,860 $ 38,258 $ 40,602 $ — Description At December 31, 2017 Level 1 Level 2 Level 3 Cash equivalents Money market fund $ 51,441 $ 51,441 $ — $ — Held-to-maturity investments U.S. treasury securities 44,859 — 44,859 — Restricted cash equivalents Money market fund 744 — 744 — Total $ 97,044 $ 51,441 $ 45,603 $ — The Company’s cash equivalents, which are in money market funds, are classified within Level 1 of the fair value hierarchy because they are valued using quoted prices as of June 30, 2018 and December 31, 2017. The Company’s restricted cash equivalents bore interest at the prevailing market rates for instruments with similar characteristics and, accordingly, the carrying value of these instruments also approximated their fair value. These financial instruments were classified within Level 2 of the fair value hierarchy because the inputs to the fair value measurement are valued using observable inputs as of June 30, 2018 and December 31, 2017. The Company’s held-to-maturity investments bore interest at the prevailing market rates for instruments with similar characteristics. The financial instruments were classified within Level 2 of the fair value hierarchy because the inputs to the fair value measurement are valued using observable inputs as of June 30, 2018 and December 31, 2017. As of June 30, 2018, and December 31, 2017, the carrying amounts of the withholding tax receivable, accounts payable, and accrued expenses approximated their estimated fair values because of the short-term nature of these financial instruments. As of June 30, 2018, we had an $8.7 million long-term payable to Alnylam Pharmaceuticals, Inc. (“Alnylam”). The long-term payable carries an interest rate set at current market rates, which is the primary driver in our conclusion that the carrying value approximates fair value. There was no long-term payable for the period ended June 30, 2017. For the three and six months ended June 30, 2018 and 2017, there were no transfers between Level 1 and Level 2.

Collaborative Research and Lice

Collaborative Research and License Agreement	6 Months Ended
	Jun. 30, 2018
Research And Development [Abstract]
Collaborative Research and License Agreement	6. Collaborative Research and License Agreement On October 27, 2017, the Company entered into a collaborative research and license agreement with Boehringer Ingelheim International GmbH (“BI”) (the “BI Agreement”), pursuant to which the Company and BI jointly research and develop product candidates for the treatment of chronic liver disease using the GalXC platform, Dicerna’s proprietary RNAi-based technology. The BI Agreement is for the development of product candidates against one target gene with an option for BI to add the development of product candidates that target a second gene. Also, pursuant to the BI Agreement, Dicerna granted BI a worldwide license in connection with the research and development of the product candidates and will transfer to BI intellectual property rights of the product candidates selected by BI for clinical development and commercialization. Dicerna also may provide assistance to BI in order to help BI further develop selected product candidates. Under the terms of the BI Agreement, BI agreed to pay Dicerna a non-refundable upfront payment of $10.0 million for the first target, less a refundable withholding tax in Germany of $1.6 million. The German withholding tax was withheld by BI and remitted to the German tax authorities in accordance with local tax law; the Company received reimbursement of this tax in July 2018. During the term of the research program, BI will reimburse Dicerna the cost of certain materials and third-party expenses that have been included in the preclinical studies. The Company is eligible to receive up to $191.0 million in potential development and commercial milestones related to the initial target. Dicerna is also eligible to receive royalty payments on potential global net sales, subject to certain adjustments, tiered from high single digits up to low double digits. BI’s option to add a second target would provide for an option fee payment and success-based development and commercialization milestones and royalty payments to Dicerna. Milestone payments that are contingent upon the Company’s performance under the BI Agreement include potential developmental milestones totaling $99.0 million, including milestones for the first commercial sale. The Company has excluded the amounts from allocable consideration at the outset of the arrangement, as described below. All potential net sales milestones, totaling $95.0 million, will be accounted for in the same manner as royalties and recorded as revenue at the later of the achievement of the milestone or the satisfaction of the performance obligation. The Company assessed the BI Agreement in accordance with Topic 606 and concluded that BI is a customer. The Company identified the following performance obligations under the contract: the license of intellectual property and conducting agreed-upon research program services. The Company has concluded that the license and research and development services do not have standalone value and are not capable of being distinct, therefore, the Company considers these as one performance obligation. The Company concluded the option underlying the transfer of future licenses and potential associated research for any not-yet-known target gene is not a performance obligation of the contract at inception because the option is not considered to be a material right, as the option fee reflects the standalone selling price of the option. The Company considered the level of BI’s therapeutic expertise specifically related to RNAi, as well as BI’s know-how vis-à-vis the Company’s GalXC conjugates, and concluded that BI cannot currently benefit from the granted license on its own or together with other resources that are readily available to BI, including relationships with oligonucleotide vendors who synthesize GalXC conjugates under contract with the Company. As a result, the combination of the license of intellectual property together with the provision of research and development support services together represent the highest level of goods and services that can be deemed distinct. Based on management’s evaluation, the non-refundable upfront fee and the agreed-upon reimbursable third-party expenses constituted the amount of the consideration to be included in the transaction price and has been allocated to the performance obligations identified based on the Company’s best estimate of the relative standalone selling price via application of a market assessment approach. None of the development milestones have been included in the transaction price, since none of such milestone amounts are within the control of the Company and are not considered probable to occur until confirmed by BI, at BI’s sole discretion. Any consideration related to commercial sales-based milestones (including royalties) will be recognized when the related sales occur, since these amounts have been determined to relate predominantly to the license granted to BI and therefore are recognized at the later of when the performance obligation is satisfied or the related sales occur. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The $10.3 million transaction price is being recognized over the current research term, which is estimated to extend through June 30, 2019, which represents the Company’s best estimate of the period of the obligation to provide research support services to BI, and is the expected period over which we estimate the deferred revenue balance will be recognized in revenue. Related revenue is being recognized on a straight-line basis, which is in management’s judgment an appropriate measure of progress toward satisfying the performance obligation, largely in absence of evidence that obligations are fulfilled in a specific pattern. The following table presents changes in the Company’s deferred revenue accounts during the six months ended June 30, 2018 (amounts in thousands). Six months ended June 30, 2018 Balance at beginning of period Additions Deductions Balance at end of period Current portion of deferred revenue $ 6,180 — $ 6,180 Deferred revenue, net of current portion $ 3,090 — $ (3,090 ) $ — The Company recognized revenues of $1.5 million and $3.1 million for the three and six months ended June 30, 2018, as a result of changes in the deferred revenue balances. There was no activity related to the Company’s deferred revenue accounts during the three and six months ended June 30, 2017.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Facility lease Future minimum lease payments on the Company’s non-cancelable operating lease for office and laboratory space are as follows (amounts in thousands): Years Ending December 31, Operating Lease Remaining 2018 $ 817 2019 $ 1,678 2020* 1,580 Total $ 4,075 * The end of the lease term is November 30, 2020. Litigation On June 10, 2015, Alnylam filed a complaint against the Company in the Superior Court of Middlesex County, Massachusetts (the “Court”). The complaint alleged misappropriation of confidential, proprietary, and trade secret information, as well as other related claims, in connection with the Company’s hiring of a number of former employees of Merck & Co., Inc. (“Merck”) and its discussions with Merck regarding the acquisition of its subsidiary, Sirna Therapeutics, Inc., which was subsequently acquired by Alnylam. On April 18, 2018, the Company and Alnylam entered into a Confidential Settlement Agreement and General Release (the “Settlement Agreement”), resolving all ongoing litigation between the Company and Alnylam. The terms of the Settlement Agreement include mutual releases and dismissals with prejudice of all claims and counterclaims in the following litigation between the parties: (i) Alnylam Pharmaceuticals, Inc. v. Dicerna Pharmaceuticals, Inc. Dicerna Pharmaceuticals, Inc., v. Alnylam Pharmaceuticals, Inc. Under the Settlement Agreement, for periods ranging from 18 months up to four years, the Company will be restricted in its development and other activities relating to oligonucleotide-based therapeutics directed toward a defined set of eight Alnylam targets (the “Oligo Restrictions”). The Oligo Restrictions pertain to targets where Dicerna does not have, or does not currently intend to have, a therapeutic program, or are expected to be consistent with Dicerna’s execution on programs in the normal course of business. The Settlement Agreement does not include any admission of liability or wrongdoing by either party or any licenses to any intellectual property from either party. On April 20, 2018, the Company and Alnylam entered into the Share Issuance Agreement, pursuant to which the Company agreed to issue to Alnylam 983,208 Shares in satisfaction of the Company’s obligation under the Settlement Agreement to deliver Shares to Alnylam. The Share Issuance Agreement contains customary representations and warranties of each party. Pursuant to the terms of the Share Issuance Agreement, Alnylam may not, without the prior approval of the Company, dispose of any of the Shares for a six-month period commencing on the closing date of the Share issuance. Thereafter, through the fifth anniversary of the closing date of the Share issuance, Alnylam will only dispose of the maximum number of Shares that it would be permitted to dispose if the Shares were subject to the volume restrictions set forth in Rule 144(e) of the Securities Act of 1933, as amended. The Company paid the upfront payment of $2.0 million dollars in May 2018 and recorded the future payment of $13.0 million as a long-term payable discounted to present value of $8.7 million at an effective interest rate of 10%. The 983,208 shares issued pursuant to the Share Issuance Agreement was recorded at fair market value of $10.3 million based on the Company’s closing share price on April 18, 2018, the date the Settlement Agreement was executed. The Settlement Agreement resulted in the Company recording an additional $21.0 million of litigation expenses for the three and six months ended June 30, 2018. The Company did not assign any value to the Oligo Restrictions as the Company did not incur additional losses or give up any value as a result of the restrictions. Total litigation expense was $22.2 million and $25.4 million for the three and six months ended June 30, 2018, respectively, all of which related to the litigation with Alnylam, of which $21.0 million related to the Settlement Agreement. The Company recorded litigation expenses, also related to the Alnylam litigation, of $2.2 million and $3.6 million for three and six months ended June 30, 2017, respectively, which was previously recorded as a component of general and administrative expenses and recast to litigation expense for comparative purposes. From time to time, the Company may be subject to various claims and legal proceedings. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount is reasonably estimable, the Company will accrue a liability for the estimated loss. There were no contingent liabilities recorded as of June 30, 2018 and December 31, 2017.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	8. Subsequent Events Under the BI Agreement, BI paid to Dicerna a non-refundable upfront payment of $10.0 million for the first target, less a refundable withholding tax in Germany of $1.6 million. The German withholding tax was withheld by BI and remitted to the German tax authorities in accordance with local tax law, and the Company received reimbursement of this tax in July of 2018.

Description of Business and B15

Description of Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Business	Business Dicerna Pharmaceuticals, Inc. (“Dicerna” or the “Company”), a Delaware corporation founded in 2006 and located in Cambridge, Massachusetts, is a biopharmaceutical company focused on the discovery and development of innovative subcutaneously delivered ribonucleic acid interference (“RNAi”)-based pharmaceuticals using its GalXC TM
Basis of presentation	Basis of presentation These condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, these condensed consolidated financial statements do not include all of the information and notes required by GAAP to constitute a complete set of financial statements. These condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position at June 30, 2018 and results of operations and cash flows for the interim periods ended June 30, 2018 and 2017. These unaudited condensed consolidated interim financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The results of the three and six months ended June 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year.
Significant judgments and estimates	Significant judgments and estimates The preparation of consolidated 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 Company’s consolidated financial statements, as well as the revenues and expenses incurred during the reporting periods. On an ongoing basis, the Company evaluates judgments and estimates, including those related to revenue recognition and accrued expenses. The Company bases its estimates on historical experience and on various other factors that the Company believes are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not apparent from other sources. Changes in estimates are reflected in reported results for the period in which they become known. Actual results could differ materially from those estimates.
Liquidity	Liquidity Based on the Company’s current operating plan and liquidity, management believes that available cash, cash equivalents, and held-to-maturity investments will be sufficient to fund the Company’s planned level of operations for at least the 12-month period following, August 8, 2018, which is the date that these condensed consolidated financial statements have been issued. Notwithstanding the availability of current liquidity, the Company’s ability to fund its preclinical and clinical operations, including completion of its clinical trials, will depend on the Company’s ability to raise additional capital through a combination of public or private equity offerings, debt financings, and research collaborations and license agreements. If the Company is unable to generate funding from one or more of these sources within a reasonable timeframe, it may have to delay, reduce, or terminate its research and development programs, preclinical or clinical trials, limit strategic opportunities, or undergo reductions in its workforce or other corporate restructuring activities.
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies — There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K, except as a result of adopting the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“Topic 606”), as discussed below.
Revenue recognition	Revenue recognition The Company generates revenue from research collaboration and license agreements with third-party customers. Goods and services in the agreements typically include (i) the grant of licenses for the use of the Company’s technology and (ii) the provision of services associated with the research and development of customer product candidates. Such agreements may provide for consideration to the Company in the form of upfront payments, research and development services, option payments, milestone payments, and royalty payments on licensed products. The Company accounts for a contract when the Company has approval and commitment from both parties, when the rights of the parties are identified, when payment terms are identified, when the contract has commercial substance, and when collectability of consideration is probable. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, management completes the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations; (iii) measurement of the transaction price, including whether there are any constraints on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for the relevant arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the underlying contract. The Company uses key assumptions to determine the stand-alone selling price which may include, as applicable, relevant market data, forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, or probabilities of technical and regulatory success. Licenses of intellectual property: If a license granted to a customer to use the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from consideration allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company applies judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, to conclude upon the appropriate method of measuring progress for purposes of recognizing revenue related to consideration allocated to the performance obligation. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each contract with a customer that includes development or regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or of the licensee, such as regulatory approvals, are assessed as to the probability of achieving the related milestones. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of all milestones and any related constraint, and, if necessary, adjusts the estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis and are recorded as revenue and through earnings in the period of adjustment. Options: Customer options, such as options granted to allow a licensee to choose to research and develop product candidates against target genes to be identified in the future, generally do not provide a material right to the customer and therefore do not give rise to a separate performance obligation. As such, the additional consideration that would result from a customer exercising an option in the future is not included in the transaction price for the current contract. Instead, additional option fee payments are recognized or begin being recognized as revenue when the licensee exercises the options, and the exercise of the option would be treated as a separate contract for accounting purposes. Research and development services: Arrangements that include a promise to provide research or development services at the licensee’s discretion are assessed to determine whether the services provide a material right to the licensee and are capable of being distinct, are not highly interdependent or do not significantly modify one another, and if so, the services are accounted for as separate performance obligations as the services are provided to the customer. Otherwise, where research or development services are determined not to be capable of being distinct or distinct within the context of the contract, those services are added to the performance obligation that includes the underlying license. Royalties: For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, and when the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any out-licensing arrangement. The Company receives payments from its licensees as established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Where applicable, amounts are recorded as contracts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted in 2018 Revenue recognition In May 2014, the FASB issued Topic 606, which amends the guidance for accounting for revenue from contracts with customers, superseding the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition Income taxes In October 2016, the FASB issued ASU No. 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory Statement of cash flows In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash Stock-based compensation In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting Not yet adopted Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Nonemployee stock-based compensation In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Compensation—Stock Compensation (Topic 718) Equity—Equity Based Payments to Nonemployees (Topic 505)

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Dilutive Securities Outstanding	The outstanding securities presented below were excluded from the calculation of net loss per share, because such securities would have been anti-dilutive due to the Company’s net loss per share during the periods ending on the dates presented. June 30, 2018 2017 Options to purchase common stock 7,556,554 6,212,437 Warrants to purchase common stock 2,198 87,901 Unvested restricted common stock — 10,000 Redeemable convertible preferred stock — 718,404 Total 7,558,752 7,028,742

Held-to-maturity Investments (T

Held-to-maturity Investments (Tables)	6 Months Ended
	Jun. 30, 2018
Text Block [Abstract]
Schedule of Held-To-Maturity Investments	The following tables provide information relating to the Company’s held-to-maturity investments (amounts in thousands). Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value As of June 30, 2018: Held-to-maturity investments U.S. treasury securities maturing in one year or less $ 39,875 $ — $ (17 ) $ 39,858 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value As of December 31, 2017: Held-to-maturity investments U.S. treasury securities maturing in one year or less $ 44,889 $ — $ (30 ) $ 44,859

Stock Option Plan and Stock-B18

Stock Option Plan and Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
Stock-Based Compensation Expense	The Company has classified stock-based compensation in its condensed consolidated statements of operations as follows (amounts in thousands): Three Months Ended June 30, Six Months Ended June 30, Three Months Ended June 30, Six Months Ended June 30, 2018 2018 2017 2017 Research and development expense $ 751 $ 1,557 $ 972 $ 1,917 General and administrative expenses 1,028 1,968 1,053 2,116 Total $ 1,779 $ 3,525 $ 2,025 $ 4,033
Stock Options Granted to Non-Employees [Member]
Schedule of Valuation Assumptions	The assumptions used to estimate the grant date fair value using the Black-Scholes option pricing model were as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Common stock price $9.14 – $14.41 $9.14 – $14.41 Expected option term (in years) 5.50-6.25 5.50-6.25 Expected volatility 76.8% – 78.33% 75.89% –90.9% Risk-free interest rate 2.65% – 2.84% 2.32% – 2.84% Expected dividend yield 0.00% 0.00% Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Common stock price $2.91 – $3.47 $2.49 – $3.47 Expected option term (in years) 5.50-6.25 5.50-6.25 Expected volatility 79.7% – 80.8% 79.4% – 80.8% Risk-free interest rate 1.86% – 1.89% 1.86% – 2.07% Expected dividend yield 0.00% 0.00%

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Assets Measured or Disclosed at Fair Value	A summary of the Company’s financial assets that are measured or disclosed at fair value on a recurring basis as of June 30, 2018 and December 31, 2017 are presented below (amounts in thousands). Description At June 30, 2018 Level 1 Level 2 Level 3 Cash equivalents Money market fund $ 38,258 $ 38,258 $ $ — Held-to-maturity investments U.S. treasury securities 39,858 — $ 39,858 — Restricted cash equivalents Money market fund 744 744 — Total $ 78,860 $ 38,258 $ 40,602 $ — Description At December 31, 2017 Level 1 Level 2 Level 3 Cash equivalents Money market fund $ 51,441 $ 51,441 $ — $ — Held-to-maturity investments U.S. treasury securities 44,859 — 44,859 — Restricted cash equivalents Money market fund 744 — 744 — Total $ 97,044 $ 51,441 $ 45,603 $ —

Collaborative Research and Li20

Collaborative Research and License Agreement (Tables)	6 Months Ended
	Jun. 30, 2018
Research And Development [Abstract]
Schedule of Changes in Deferred Revenue Accounts	The following table presents changes in the Company’s deferred revenue accounts during the six months ended June 30, 2018 (amounts in thousands). Six months ended June 30, 2018 Balance at beginning of period Additions Deductions Balance at end of period Current portion of deferred revenue $ 6,180 — $ 6,180 Deferred revenue, net of current portion $ 3,090 — $ (3,090 ) $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Minimum Lease Payments on Company's Non-cancelable Operating Lease	Future minimum lease payments on the Company’s non-cancelable operating lease for office and laboratory space are as follows (amounts in thousands): Years Ending December 31, Operating Lease Remaining 2018 $ 817 2019 $ 1,678 2020* 1,580 Total $ 4,075 * The end of the lease term is November 30, 2020.

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Dilutive Securities Outstanding (Detail) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	7,558,752	7,028,742
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	7,556,554	6,212,437
Hercules Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	2,198	87,901
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities		10,000
Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities		718,404

Held-to-maturity Investments -

Held-to-maturity Investments - Schedule of Held-To-Maturity Investments (Detail) - US Treasury Securities [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investments, Amortized Cost	$ 39,875	$ 44,889
Held-to-maturity investments, Gross Unrealized Gains	0	0
Held-to-maturity investments, Gross Unrealized Losses	(17)	(30)
Held-to-maturity investments, Fair Value, Total	$ 39,858	$ 44,859

Stock Option Plan and Stock-B24

Stock Option Plan and Stock-Based Compensation - Additional Information (Detail) - Employee Stock Option [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, granted	442,000	352,500	1,761,350	1,330,997
Fair value of stock options	$ 3.8	$ 0.7	$ 13.2	$ 2.7

Stock Option Plan and Stock-B25

Stock Option Plan and Stock-Based Compensation - Schedule of Valuation Assumptions (Detail) - Employee Stock Option [Member] - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price	$ 9.14	$ 2.91	$ 9.14	$ 2.49
Expected option term (in years)	5 years 6 months	5 years 6 months	5 years 6 months	5 years 6 months
Expected volatility	76.80%	79.70%	75.89%	79.40%
Risk-free interest rate	2.65%	1.86%	2.32%	1.86%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price	$ 14.41	$ 3.47	$ 14.41	$ 3.47
Expected option term (in years)	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months
Expected volatility	78.33%	80.80%	90.90%	80.80%
Risk-free interest rate	2.84%	1.89%	2.84%	2.07%

Stock Option Plan and Stock-B26

Stock Option Plan and Stock-Based Compensation - Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,779	$ 2,025	$ 3,525	$ 4,033
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	751	972	1,557	1,917
General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,028	$ 1,053	$ 1,968	$ 2,116

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets Measured or Disclosed at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Restricted cash equivalents
Total	$ 78,860	$ 97,044
Money Market Fund [Member]
Cash equivalents
Money market fund	38,258	51,441
Restricted cash equivalents
Restricted investments, at fair value	744	744
US Treasury Securities [Member]
Held-to-maturity investments
U.S. treasury securities	39,858	44,859
Level 1 [Member]
Restricted cash equivalents
Total	38,258	51,441
Level 1 [Member] | Money Market Fund [Member]
Cash equivalents
Money market fund	38,258	51,441
Level 2 [Member]
Restricted cash equivalents
Total	40,602	45,603
Level 2 [Member] | Money Market Fund [Member]
Restricted cash equivalents
Restricted investments, at fair value	744	744
Level 2 [Member] | US Treasury Securities [Member]
Held-to-maturity investments
U.S. treasury securities	$ 39,858	$ 44,859

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Jun. 30, 2018	Jun. 30, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term payable and accrued interest	$ 8,904,000	$ 0
Transfers between Level 1 and Level 2	0	$ 0
Alnylam [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term payable and accrued interest	$ 8,700,000

Collaborative Research and Li29

Collaborative Research and License Agreement - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2018USD ($)PerformanceObligation	Dec. 31, 2017USD ($)	Oct. 27, 2017USD ($)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial non-refundable upfront payment				$ 10,000
Proceeds from income tax refunds	$ 1,583	$ 1,583	$ 1,583
Number of performance obligation | PerformanceObligation		1
Recognition of transaction price over current research term		$ 10,300
Revenue recognized	1,500	3,090
BI Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Additional payments upon potential development and commercial milestones	191,000	191,000
BI Agreement [Member] | Potential Development Milestones [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Potential Development Milestone		99,000
BI Agreement [Member] | Net Sales Milestones [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Net Sales Milestone	$ 95,000	$ 95,000
Foreign Tax Authority [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Proceeds from income tax refunds				$ 1,600

Collaborative Research and Li30

Collaborative Research and License Agreement - Schedule of Changes in Deferred Revenue Accounts (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Revenue Recognition And Deferred Revenue [Abstract]
Balance at beginning of period		$ 6,180
Additions		0
Balance at end of period	$ 6,180	6,180
Balance at beginning of period		3,090
Additions		0
Deductions	(1,500)	(3,090)
Balance at end of period	$ 0	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Summary of Future Minimum Lease Payments on Company's Non-cancelable Operating Lease (Detail) $ in Thousands	Jun. 30, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Remaining 2,018	$ 817
2,019	1,678
2,020	1,580	[1]
Total	$ 4,075
[1]	The end of the lease term is November 30, 2020.

Commitments and Contingencies32

Commitments and Contingencies - Summary of Future Minimum Lease Payments on Company's Non-cancelable Operating Lease (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Lease Expiration Date	Nov. 30, 2020

Commitments and Contingencies33

Commitments and Contingencies - Additional Information (Detail)	Apr. 18, 2018USD ($)shares	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	May 31, 2018USD ($)	Apr. 20, 2018shares	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Litigation settlement expense		$ 22,244,000	$ 2,234,000	$ 25,428,000	$ 3,608,000
Settled Litigation [Member]
Loss Contingencies [Line Items]
Contingent liabilities		0		$ 0				$ 0
Settled Litigation [Member] | Alnylam [Member]
Loss Contingencies [Line Items]
Settlement agreement date	April 18, 2018
Settlement agreement terms				The terms of the Settlement Agreement include mutual releases and dismissals with prejudice of all claims and counterclaims in the following litigation between the parties: (i) Alnylam Pharmaceuticals, Inc. v. Dicerna Pharmaceuticals, Inc., No. 15-4126 pending in the Massachusetts Superior Court for Middlesex County and (ii) Dicerna Pharmaceuticals, Inc., v. Alnylam Pharmaceuticals, Inc. No.1:17-cv-11466 pending in the United States District Court for the District of Massachusetts.
Litigation settlement upfront payment	$ 2,000,000					$ 2,000,000
Percentage of consideration receivable related to future collaboration	10.00%
Additional litigation settlement payment	$ 13,000,000
Additional litigation settlement payment date	Apr. 28, 2022
Loss contingency settlement agreement counterparty's name	Alnylam Pharmaceuticals, Inc.
Number of Oligo Restrictions target	8
Issuance of shares under shares issuance agreement | shares	983,208						983,208
Litigation future payment						13,000,000
Litigation settlement discounted present value of long-term payable						$ 8,700,000
Debt instrument effective interest percentage						10.00%
Share issued at fair market value	$ 10,300,000
Litigation settlement expense		22,200,000	$ 2,200,000	$ 25,400,000	$ 3,600,000
Settled Litigation [Member] | Alnylam [Member] | Settlement Agreement
Loss Contingencies [Line Items]
Litigation settlement expense		$ 21,000,000		$ 21,000,000
Settled Litigation [Member] | Alnylam [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Loss contingency settlement agreement period	18 months
Settled Litigation [Member] | Alnylam [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Loss contingency settlement agreement period	4 years

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 08, 2018	Jul. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Oct. 27, 2017
Subsequent Events [Line Items]
Initial non-refundable upfront payment					$ 10,000
Proceeds from income tax refunds			$ 1,583	$ 1,583
Subsequent Event [Member]
Subsequent Events [Line Items]
Initial non-refundable upfront payment	$ 10,000
Foreign Tax Authority [Member]
Subsequent Events [Line Items]
Proceeds from income tax refunds					$ 1,600
Foreign Tax Authority [Member] | Subsequent Event [Member]
Subsequent Events [Line Items]
Proceeds from income tax refunds		$ 1,600