Viridian Therapeutics (VRDN) 10-Q 8 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	MIRAGEN THERAPEUTICS, INC.
Entity Central Index Key	0001590750
Document Type	10-Q
Document Period End Date	Sep. 30, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		31,788,113

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 24,857	$ 32,606
Short-term investments	8,981	29,875
Accounts receivable	979	24
Prepaid expenses and other current assets	3,400	2,865
Total current assets	38,217	65,370
Property and equipment, net	596	727
Other assets	0	50
Total assets	38,813	66,147
Current liabilities:
Accounts payable	1,556	571
Accrued liabilities	4,857	3,868
Current portion of note payable	3,972	2,294
Total current liabilities	10,385	6,733
Note payable, net of current portion	5,259	8,004
Other liabilities	0	66
Total liabilities	15,644	14,803
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 100,000,000 shares authorized; 31,181,749 and 30,839,463 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	312	308
Additional paid-in capital	180,905	177,335
Accumulated other comprehensive gain (loss)	3	(3)
Accumulated deficit	(158,051)	(126,296)
Total stockholders’ equity	23,169	51,344
Total liabilities and stockholders’ equity	$ 38,813	$ 66,147

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	31,181,749	30,839,463
Common stock, shares outstanding (in shares)	31,181,749	30,839,463

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Total revenue	$ 695	$ 944	$ 3,581	$ 7,910
Operating expenses:
Research and development	9,027	7,399	26,377	22,187
General and administrative	2,898	2,696	9,112	8,354
Total operating expenses	11,925	10,095	35,489	30,541
Loss from operations	(11,230)	(9,151)	(31,908)	(22,631)
Other income (expense):
Interest and other income	204	362	818	890
Interest and other expense	(204)	(222)	(665)	(645)
Net loss	(11,230)	(9,011)	(31,755)	(22,386)
Change in unrealized gain on investments	(8)	(10)	6	(6)
Comprehensive loss	(11,238)	(9,021)	(31,749)	(22,392)
Net loss	$ (11,230)	$ (9,011)	$ (31,755)	$ (22,386)
Net loss per share, basic and diluted (in dollars per share)	$ (0.36)	$ (0.29)	$ (1.02)	$ (0.77)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	31,081,594	30,723,704	30,984,582	29,182,872
Collaboration revenue
Revenue:
Total revenue	$ 625	$ 814	$ 3,471	$ 6,938
Grant revenue
Revenue:
Total revenue	$ 70	$ 130	$ 110	$ 972

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Public offering	At-the-market	Private placement	Common Stock	Common StockPublic offering	Common StockAt-the-market	Common StockPrivate placement	Additional Paid-in Capital	Additional Paid-in CapitalPublic offering	Additional Paid-in CapitalAt-the-market	Additional Paid-in CapitalPrivate placement	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017					22,568,006
Beginning balance at Dec. 31, 2017	$ 38,510				$ 226				$ 131,877				$ 0	$ (93,593)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)						7,414,996
Issuance of common stock, net of issuance cost		$ 37,845				$ 74				$ 37,771
Shares issued for cash upon the exercise of stock options (in shares)					179,598
Shares issued for cash upon the exercise of stock options	112				$ 2				110
Issuance of common stock for cash under employee stock purchase plan (in shares)					23,940
Issuance of common stock for cash under employee stock purchase plan	110								110
Share-based compensation expense	790								790
Net loss	(4,661)													(4,661)
Ending balance (in shares) at Mar. 31, 2018					30,186,540
Ending balance at Mar. 31, 2018	72,706				$ 302				170,658				0	(98,254)
Beginning balance (in shares) at Dec. 31, 2017					22,568,006
Beginning balance at Dec. 31, 2017	38,510				$ 226				131,877				0	(93,593)
Stockholders’ deficit
Change in unrealized gain on investments	(6)
Net loss	(22,386)
Ending balance (in shares) at Sep. 30, 2018					30,833,367
Ending balance at Sep. 30, 2018	60,718				$ 308				176,395				(6)	(115,979)
Beginning balance (in shares) at Mar. 31, 2018					30,186,540
Beginning balance at Mar. 31, 2018	72,706				$ 302				170,658				0	(98,254)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)							372,852
Issuance of common stock, net of issuance cost			$ 2,657				$ 4				$ 2,653
Shares issued for cash upon the exercise of stock options (in shares)					36,401
Shares issued for cash upon the exercise of stock options	34				$ 0				34
Share-based compensation expense	984								984
Change in unrealized gain on investments	4												4
Net loss	(8,714)													(8,714)
Ending balance (in shares) at Jun. 30, 2018					30,595,793
Ending balance at Jun. 30, 2018	67,671				$ 306				174,329				4	(106,968)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)								150,987
Issuance of common stock, net of issuance cost				$ 935				$ 2				$ 933
Shares issued for cash upon the exercise of stock options (in shares)					58,083
Shares issued for cash upon the exercise of stock options	33				$ 0				33
Issuance of common stock for cash under employee stock purchase plan (in shares)					28,504
Issuance of common stock for cash under employee stock purchase plan	132								132
Share-based compensation expense	968								968
Change in unrealized gain on investments	(10)												(10)
Net loss	(9,011)													(9,011)
Ending balance (in shares) at Sep. 30, 2018					30,833,367
Ending balance at Sep. 30, 2018	$ 60,718				$ 308				176,395				(6)	(115,979)
Beginning balance (in shares) at Dec. 31, 2018	30,839,463				30,839,463
Beginning balance at Dec. 31, 2018	$ 51,344				$ 308				177,335				(3)	(126,296)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)							47,589
Issuance of common stock, net of issuance cost			134				$ 1				133
Issuance of common stock for cash under employee stock purchase plan (in shares)					34,167
Issuance of common stock for cash under employee stock purchase plan	84								84
Share-based compensation expense	1,018								1,018
Change in unrealized gain on investments	5												5
Net loss	(11,629)													(11,629)
Ending balance (in shares) at Mar. 31, 2019					30,921,219
Ending balance at Mar. 31, 2019	$ 40,956				$ 309				178,570				2	(137,925)
Beginning balance (in shares) at Dec. 31, 2018	30,839,463				30,839,463
Beginning balance at Dec. 31, 2018	$ 51,344				$ 308				177,335				(3)	(126,296)
Stockholders’ deficit
Change in unrealized gain on investments	6
Net loss	$ (31,755)
Ending balance (in shares) at Sep. 30, 2019	31,181,749				31,181,749
Ending balance at Sep. 30, 2019	$ 23,169				$ 312				180,905				3	(158,051)
Beginning balance (in shares) at Mar. 31, 2019					30,921,219
Beginning balance at Mar. 31, 2019	40,956				$ 309				178,570				2	(137,925)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)							96,652
Issuance of common stock, net of issuance cost			$ 278				$ 1				$ 277
Shares issued for cash upon the exercise of stock options (in shares)					19,492
Shares issued for cash upon the exercise of stock options	15				$ 0				15
Share-based compensation expense	1,075								1,075
Change in unrealized gain on investments	9												9
Net loss	(8,896)													(8,896)
Ending balance (in shares) at Jun. 30, 2019					31,037,363
Ending balance at Jun. 30, 2019	33,437				$ 310				179,937				11	(146,821)
Stockholders’ deficit
Shares issued for cash upon the exercise of stock options (in shares)					122,300
Shares issued for cash upon the exercise of stock options	70				$ 1				69
Issuance of common stock for cash under employee stock purchase plan (in shares)					22,086
Issuance of common stock for cash under employee stock purchase plan	26				$ 1				25
Share-based compensation expense	874								874
Change in unrealized gain on investments	(8)												(8)
Net loss	$ (11,230)													(11,230)
Ending balance (in shares) at Sep. 30, 2019	31,181,749				31,181,749
Ending balance at Sep. 30, 2019	$ 23,169				$ 312				$ 180,905				$ 3	$ (158,051)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (31,755)	$ (22,386)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	2,967	2,742
Non-cash interest expense	266	283
Depreciation and amortization	215	206
Amortization of premiums and discounts on available-for-sale securities	(410)	(229)
Changes in operating assets and liabilities:
Accounts receivable	(955)	74
Prepaid expenses and other assets	(486)	(927)
Accounts payable	985	287
Accrued and other liabilities	923	1,281
Net cash used in operating activities	(28,250)	(18,669)
Cash flows from investing activities:
Purchases of short-term investments	(32,690)	(38,604)
Maturities of short-term investments	54,000	0
Purchases of property and equipment	(84)	(394)
Net cash provided by (used in) investing activities	21,226	(38,998)
Cash flows from financing activities:
Payments of principal on note payable	1,333	0
Proceeds from stock purchases under employee stock purchase plan	110	242
Proceeds from the exercise of stock options	85	179
Net cash provided by (used in) financing activities	(725)	41,926
Net decrease in cash and cash equivalents	(7,749)	(15,741)
Cash and cash equivalents at beginning of period	32,606	47,441
Cash and cash equivalents at end of period	24,857	31,700
Supplemental disclosure of cash flow information
Cash paid for interest	406	358
Supplemental disclosure of non-cash investing and financing activities
Change in unrealized gain on investments	6	(6)
Amortization of public offering costs	1	55
Unpaid common stock issuance costs included in current liabilities	0	13
At-the-market
Cash flows from financing activities:
Proceeds from the sale of common stock	426	2,747
Payment of issuance costs associated with the sale of common stock	(13)	(82)
Public offering
Cash flows from financing activities:
Proceeds from the sale of common stock	0	40,782
Payment of issuance costs associated with the sale of common stock	0	(2,890)
Private placement
Cash flows from financing activities:
Proceeds from the sale of common stock	0	1,000
Payment of issuance costs associated with the sale of common stock	$ 0	$ (52)

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	DESCRIPTION OF BUSINESS Miragen Therapeutics, Inc., a Delaware corporation (the “Company” or “Miragen”), is a clinical-stage biopharmaceutical company discovering and developing proprietary RNA-targeted therapies with a specific focus on microRNAs and their role in certain diseases where there is a high unmet medical need. microRNAs are short RNA molecules, or oligonucleotides, that regulate gene expression and play vital roles in influencing the pathways responsible for many disease processes. The Company has three product candidates, cobomarsen, remlarsen, and MRG-110, in clinical development. Liquidity The accompanying condensed consolidated financial statements have been prepared on a basis which assumes the Company is a going concern, and does not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classifications of liabilities that may result from any uncertainty related to its ability to continue as a going concern. The Company has funded its operations to date principally through proceeds received from the sale of the Company’s common stock (“Common Stock”) and other equity securities, debt financings, and up-front milestones and reimbursements received under a license and collaboration agreement (the “Servier Collaboration Agreement”) with Les Laboratoires Servier and Institut de Recherches Servier (collectively, “Servier”). In August 2019, the Company received notice of Servier’s intention to terminate the Servier Collaboration Agreement effective February 1, 2020. As a result, the Company does not expect to generate future revenue under the Servier Collaboration Agreement. As of September 30, 2019 , the Company had approximately $33.8 million in cash, cash equivalents, and short-term investments. Based on its current operating plans, management believes that the Company’s cash, cash equivalents, and short-term investments may not be sufficient to fund its operations for the period one year following the issuance of these financial statements, without adjustment to its current operating plans. The Company expects that its current cash, cash-equivalents, and short-term investments will be sufficient to fund the Company’s current operations through the second quarter of 2020 . The Company intends to seek additional capital through equity and/or debt financings, collaborative, or other funding arrangements with partners or through other sources of financing. Should the Company seek additional financing from outside sources, the Company may not be able to raise such financing on terms acceptable to the Company, or at all. If the Company is unable to raise additional capital when required or on acceptable terms, the Company may be required to scale back or discontinue the development of its product candidates, reduce headcount, file for bankruptcy, reorganize, merge with another entity, or cease operations altogether. The Company has no products approved for commercial sale, has not generated any revenue from product sales, and cannot guarantee when or if it will generate any revenue. Since its inception and through September 30, 2019 , the Company has generated an accumulated deficit of $158.1 million . Substantially all of the Company’s operating losses resulted from expenses incurred in connection with its research and development programs and from general and administrative costs associated with its operations. The Company expects to incur significant expenses and increased operating losses for at least the next several years as it continues the clinical development of, and seeks regulatory approval for, its product candidates. It is expected that operating losses will fluctuate significantly from quarter to quarter and year to year due to timing of clinical development programs and efforts to achieve regulatory approval. To continue its operations at the current level, the Company will continue to require additional capital. The amount and timing of future funding requirements will depend on many factors, including the pace and results of the Company’s clinical development efforts, securing partnerships and collaborations, and issuing debt or other financing vehicles. The Company’s ability to secure additional capital is dependent upon several factors, some of which are outside of the Company’s control, including success in developing its technology and drug product candidates, operational performance, and market conditions. Failure to raise capital as and when needed, on favorable terms or at all, would have a negative impact on the Company’s financial condition and its ability to develop its product candidates. Changing circumstances may cause the Company to consume capital significantly faster or slower than currently anticipated. If the Company is unable to acquire additional capital or resources, it will be required to modify its operational plans. The estimates included herein are based on assumptions that may prove to be wrong, and the Company could exhaust its available financial resources sooner than currently anticipated.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Miragen Therapeutics Europe Limited and miRagen Therapeutics S.à.r.l., each of which were formed for the sole purpose of submitting regulatory filings in Europe. The Company’s subsidiaries have no employees or operations. The financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2019 , or for any other interim period, or for any other future year. The balance sheet as of December 31, 2018 has been derived from audited consolidated financial statements at that date but does not include all the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements of the Company and the notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2018 , filed with the SEC on March 14, 2019. The Company’s management performed an evaluation of its activities through the date of filing of these financial statements and concluded that there are no subsequent events requiring disclosure, other than as disclosed. Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with U.S. GAAP, which requires it to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Although these estimates are based on the Company’s knowledge of current events and actions it may take in the future, actual results may ultimately differ from these estimates and assumptions. Revenue Recognition Effective January 1, 2019, the Company adopted the provisions set forth in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”), using the modified retrospective transition method. Under this method, there was no cumulative effect of initially applying ASC 606 to all contracts as of the date of the adoption. The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license, or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such agreements. The terms of these agreements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; developmental, clinical, regulatory, and commercial sales milestone payments; and royalties on net sales of licensed products. In Accordance with ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized, for agreements within the scope of ASC 606, the Company performs the following five steps: (i) identification of the goods or services within the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct within the terms of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the identified performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s agreements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. Performance obligations are promises in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available, and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each agreement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenue in the period of adjustment. For agreements that include sales-based royalties, including milestone payments based on the level of sales, and 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 of the Company’s collaboration or strategic alliance agreements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction, and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes 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, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees and members of its board of directors under its 2008 Equity Incentive Plan (the “2008 Plan”) and under its 2016 Equity Incentive Plan (the “2016 Plan”) by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model. The Company recognizes share-based compensation expense on a straight-line basis over the vesting term. Prior to 2019, the Company accounted for stock options issued to non-employees (other than board members) by valuing each award using the Black-Scholes option pricing model and remeasuring the awards to the current fair value until the awards vested. Beginning in 2019, the Company accounts for share-based compensation expense related to stock options granted to non-employees by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model and recognizing share-based compensation expense on a straight-line basis over the vesting term. Research and Development Research and development costs are expensed as incurred in performing research and development activities. The costs include employee-related expense including salaries, benefits, share-based compensation, fees for acquiring and maintaining licenses under third-party license agreements, consulting fees, market research, costs of research and development activities conducted by third parties on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, and facilities and overhead costs. The Company records research and development expense in the period in which the Company receives or takes ownership of the applicable goods or when the applicable services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records up-front and milestone payments to acquire and retain contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights. The Company considers future economic benefits from acquired contractual rights to licensed technology to be uncertain until such a drug candidate is approved for sale by the U.S. Food and Drug Administration or when other significant risk factors are abated. Clinical Trial and Preclinical Study Accruals The Company makes estimates of accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on certain facts and circumstances at that time. The Company’s accrued expenses for clinical trials and preclinical studies are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and other providers. Payments under the Company’s agreements with external service providers depend on a number of factors, such as site initiation, patient screening, enrollment, delivery of reports, and other events. In accruing for these activities, the Company obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to the Company’s research and development expenses may be necessary in future periods as its estimates change. Cash and Cash Equivalents All highly-liquid investments that have maturities of 90 days or less at the date of purchase are classified as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments. Investments The Company has designated its investments as available-for-sale securities and accounts for them at their respective fair values. The securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are readily available for use in current operations are classified as short-term available-for-sale securities and are reported as a component of current assets in the accompanying condensed consolidated balance sheets. Securities that are classified as available-for-sale are measured at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders’ equity until their disposition. The Company reviews available-for-sale securities at the end of each period to determine whether they remain available-for-sale based on its then current intent. The cost of securities sold is based on the specific identification method. The securities are subject to a periodic impairment review. An impairment charge would occur when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary. As of September 30, 2019 , the Company’s short-term available-for-sale securities had an amortized cost of $9.0 million , fair value of $9.0 million , and an unrealized gain of $3 thousand . As of December 31, 2018 , the Company’s short-term available-for-sale securities had an amortized cost of $29.9 million , fair value of $29.9 million , and an unrealized loss of $3 thousand . The Company had no long-term investments as of September 30, 2019 or December 31, 2018 . Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. September 30, 2019 December 31, 2018 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 24,917 $ — $ 32,936 $ — U.S. treasury securities (included in short-term investments) 8,981 — 29,875 — Total assets $ 33,898 $ — $ 62,811 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 82 $ — $ 82 ____________________ (1) The sum of amounts presented for each period above differ from cash and cash equivalents reported in the condensed consolidated balance sheets due to uninvested cash balances and outstanding disbursements and deposits. Fair Value of Financial Instruments Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate their fair value due to the short-term nature of their maturities, such as cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses. The carrying amount of the Company’s note payable approximates its fair value (a Level 2 fair value measurement), reflecting interest rates currently available to the Company. The Company accounts for warrants to purchase its stock pursuant to ASC Topic 470, Debt, and ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for Common Stock as liabilities or equity. The warrants classified as liabilities are reported at their estimated fair value and any changes in fair value are reflected in interest expense and other related expenses. The warrants classified as equity are reported at their estimated fair value with no subsequent remeasurement. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts. The Company invests its excess cash primarily in deposits and money market funds held with one financial institution. Property and Equipment The Company carries its property and equipment at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the life of the lease (including any renewal periods that are deemed to be reasonably assured) or the estimated useful life of the assets. Construction in progress is not depreciated until placed in service. Repairs and maintenance costs are expensed as incurred and expenditures for major improvements are capitalized. Impairment of Long-Lived Assets The Company assesses the carrying amount of its property and equipment whenever events or changes in circumstances indicate the carrying amount of such assets may not be recoverable. No impairment charges were recorded during the three and nine months ended September 30, 2019 and 2018 . Net Loss per Share Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is antidilutive. Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments. Unrealized accumulated comprehensive gains or losses are reflected as a separate component in the statement of stockholders’ equity. As of September 30, 2019 and December 31, 2018 , the Company had an accumulated other comprehensive gain of $3 thousand and loss of $3 thousand , respectively. The Company had no realized gains or losses during the three and nine months ended September 30, 2019 and 2018 . Income Taxes The Company accounts for income taxes by using an asset and liability method of accounting for deferred income taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is recorded to the extent it is more likely than not that a deferred tax asset will not be realized. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. The Company’s significant deferred tax assets are for net operating loss carryforwards, tax credits, accruals and reserves, and capitalized start-up costs. The Company has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, the Company has concluded that it is more likely than not that its deferred tax assets will not be realized. The Company has no unrecognized tax benefits. The Company classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations and comprehensive loss as general and administrative expenses. No such expenses have been recognized during the three and nine months ended September 30, 2019 and 2018 . The Tax Cuts and Jobs Act of 2017 (“Tax Act”) was signed into law on December 22, 2017. The Tax Act includes significant changes to the U.S. corporate income tax system, including: (i) a federal corporate rate reduction from 35% to 21%; (ii) limitations on the deductibility of interest expense and executive compensation; (iii) elimination of the corporate alternative minimum tax (“AMT”) and a change in how existing AMT credits can be realized; (iv) change in the rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017; (v) reduction of the orphan drug credit from 50% to 25%; and (vi) transition of U.S. international taxation from a worldwide tax system to a territorial tax system. The Tax Act did not have a material impact on the condensed consolidated financial statements primarily due to the valuation allowance recorded against its net deferred tax assets. Segment Information The Company operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with the Company’s partners are denominated in U.S. dollars, except where noted. Recent Accounting Pronouncements – Adopted Revenue Recognition In May 2014, the FASB issued Accounting Standards Update ( “ ASU”) No. 2014-09 , Revenue from Contracts with Customers (Accounting Standards Codification Topic 606) , and has issued a number of clarifying ASUs subsequently, all of which outline a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.” The standard provides enhancements to the quality and consistency of how revenue is reported by companies, while also improving comparability in the financial statements of companies reporting using International Financial Reporting Standards or U.S. GAAP. The new standard requires enhanced revenue disclosures, provides guidance for transactions that were not previously addressed comprehensively, and improves guidance for multiple-element arrangements. Effective January 1, 2019, the Company adopted ASC 606 using the modified retrospective method approach, which consists of applying and recognizing the cumulative effect of ASC 606 at the date of initial application and providing certain additional disclosures defined per ASC 606. As part of this adoption, the Company completed its assessment of the Servier Collaboration Agreement under ASC 606. The adoption of ASC 606 did not have a material impact on the Company’s condensed consolidated financial statements, and it did not result in a cumulative adjustment of initially applying ASC 606 to all contracts as of the date of the adoption. Share-based Compensation In June 2018, the FASB issued ASU No. 2018-07, Compensation — Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting , which simplifies the accounting for share-based payments to non-employees by aligning it with the accounting for share-based payments to employees, with specified exceptions. The Company adopted this standard on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s condensed consolidated financial statements. Recent Accounting Pronouncements – Not Yet Adopted Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842) and subsequent amendments to the initial guidance: ASU No. 2017-13, ASU No. 2018-10, and ASU No. 2018-11 (collectively, “Topic 842”). Topic 842 requires companies to generally recognize on the balance sheet operating and financing lease liabilities and corresponding right-of-use assets. The standard is effective for the Company for interim and annual reports beginning after December 15, 2019, with early adoption permitted. At adoption, this update will be applied using a modified retrospective approach, with an option to use certain transition relief. The Company currently expects that its building operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon its adoption of Topic 842, which will increase the Company’s total assets and total liabilities that are reported relative to such amounts prior to adoption. The Company is continuing to evaluate the full impact of this standard on its condensed consolidated financial statements. Fair Value Measurement In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which modifies the disclosure requirements of fair value measurements. This standard is effective for the Company in the first quarter of 2020, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this standard on its condensed consolidated financial statements.

Cost Restructuring Plan

Cost Restructuring Plan	9 Months Ended
	Sep. 30, 2019
Restructuring and Related Activities [Abstract]
Cost Restructuring Plan	COST RESTRUCTURING PLAN On August 7, 2019, the Company announced a cost restructuring plan focused on reducing costs and directing resources to advance cobomarsen and microRNA-29 mimics, including remlarsen, while reducing investments in new discovery research. As a result of the cost restructuring plan, approximately 26 positions were identified for elimination, primarily in positions relating to research and corresponding projects, general and administrative support, and other costs related to these areas. The initial total cost restructuring plan included approximately $1.5 million of identified restructuring charges, of which $1.0 million is associated with retention, $0.3 million is associated with severance, and $0.2 million is associated with other restructuring-related costs. The following table summarizes restructuring expense during the three and nine months ended September 30, 2019 and 2018 (in thousands): 2019 2018 Retention $ 787 $ — Severance 288 — Other (1) 17 — Total restructuring charges $ 1,092 $ — ____________________ (1) Other consists of benefits primarily associated with outplacement services and extended medical insurance benefits that are electable by certain employees. Expense for other services is recognized over the period the benefits are incurred. Restructuring charges of $1.1 million related to the cost restructuring plan were recorded during the three and nine months ended September 30, 2019 , of which $0.9 million was recorded in research and development expense and $0.2 million recorded in general and administrative expense on the condensed consolidated statements of operations and comprehensive loss. Additional restructuring costs of approximately $0.4 million are expected to be incurred in the remainder of 2019 . The following table summarizes the Company’s accrued restructuring balance and associated activity (in thousands): December 31, 2018 Additions Cash Payments Adjustments September 30, 2019 Retention $ — $ 787 $ — $ — $ 787 Severance — 288 (288 ) — — Other — 17 — — 17 Total restructuring liability $ — $ 1,092 $ (288 ) $ — $ 804

Strategic Alliance and Collabor

Strategic Alliance and Collaboration with Servier	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Strategic Alliance and Collaboration with Servier	STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER In October 2011, the Company entered into the Servier Collaboration Agreement with Servier for the research, development, and commercialization of RNA-targeting therapeutics in cardiovascular disease. Under the Servier Collaboration Agreement, the Company granted Servier an exclusive license to research, develop, manufacture, and commercialize RNA-targeting therapeutics for certain microRNA targets in the cardiovascular field. Under the Servier Collaboration Agreement, Servier’s rights to named targets in the field of cardiovascular disease, as defined, and in their territory, which is worldwide except for the United States and Japan. The Company retained all other rights including commercialization of therapeutics developed under the Servier Collaboration Agreement in the field of cardiovascular disease in the United States and Japan. In accordance with the terms of the Servier Collaboration Agreement and based on the notice we received from Servier in August 2019, the Servier Collaboration Agreement will be terminated in February 2020. During the period from receipt of notice from Servier and termination in February 2020, the Company expects to complete certain activities under its development plan with Servier, which will include finalizing the two Phase 1 clinical trials of MRG-110, for which the Company recently reported data. The activities for which the Company expects to be reimbursed for under the Servier Collaboration Agreement continue to be considered a research and development performance obligation and revenue will be recognized in accordance with ASC 606. Accounting Analysis The Company evaluated the Servier Collaboration Agreement in accordance with the provisions in ASC 606. The Company has accounted for amendments to the Servier Collaboration Agreement as modifications to the original contract and not as separate contracts. The Company combined the amendments with the original agreement due to the modifications not resulting in increased promised goods or services that were distinct, and the price of the contract did not increase by an amount of consideration that reflects the Company’s standalone selling prices. The Company identified the following performance obligations under the Servier Collaboration Agreement: (i) up-front license fee a multiple-year research collaboration, under which it jointly performed agreed upon research activities directed to the identification and characterization of named targets and oligonucleotides in the cardiovascular field (the “Research Collaboration”); (ii) research and development activities; (iii) transfer of materials; (iv) developmental, clinical, regulatory, and commercial sales milestone payments; and (v) royalties on net sales of licensed products. The Company acts as a principal as it controls the goods or services prior to transfer to the customer. The Company performed the research and development activities specified in the contracts and controlled the laboratories and resources that performed the research and development activities. The Company concluded that the up-front license fees were not distinct from the Research Collaboration as Servier cannot obtain the benefit of the license without the Research Collaboration. This performance obligation represented the licensing of Company‑owned intellectual property related to the Company’s knowledge of microRNA therapeutics for certain specific diseases, together with research activities that were interdependent with licensed intellectual property to determine feasibility of commercialization. As of January 1, 2019, the date of the initial application of ASC 606 by the Company, the remaining total transaction price associated with the Servier Collaboration Agreement was determined to be approximately $3.1 million consisting of maximum reimbursements of development costs under the development plan. During February 2019, the Joint Steering Committee approved an additional $1.0 million of development plan activities. As of January 1, 2019, the Company identified up to $60.4 million in development and regulatory milestones under the Servier Collaboration agreement, and the Company had recognized $7.5 million in milestone revenue through the initial application date. The Company utilizes the most likely amount method to estimate any development and regulatory milestone payments to be received. The Company considered the stage of development and the risks associated with the remaining development required to achieve these milestones, as well as whether the achievement of the milestones is outside the control of the Company. The Company determined that the remaining milestone payments were fully constrained, as a result of the uncertainty whether the milestones would be achieved by September 30, 2019. The Company also determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur and, therefore, these payments have also been excluded from the transaction price. The Company re-evaluates the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. As of September 30, 2019, no adjustments to the transaction price were noted. The transaction price was allocated to the performance obligations based on the relative estimated standalone selling prices of each performance obligation or, in the case of certain variable consideration, to one or more performance obligations. Research and development activities are priced generally at the standard labor rates for the respective activity and transfer of materials are generally priced at cost. Milestone payments are individually negotiated and because of the unique nature of each milestone, there are no comparable transactions to compare to; therefore, the negotiated amounts of the milestones in the agreement are the standalone selling price. Amounts incurred and billable, but not billed to Servier, for research and related intellectual property activities totaled $0.6 million and $0.5 million as of September 30, 2019 and December 31, 2018 , respectively. These amounts are included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheets. As of September 30, 2019 , the Company had $1.0 million in accounts receivable outstanding for Servier research and related intellectual property activities. As of December 31, 2018 , the Company had no accounts receivable balances outstanding for Servier research and related intellectual property activities. Collaboration revenue under the Servier Collaboration Agreement consisted of the following: Three Months Ended Nine Months Ended 2019 2018 2019 2018 (in thousands) Milestone payments $ — $ — $ — $ 3,690 Research and development reimbursable costs 625 814 3,471 3,248 Total collaboration revenue $ 625 $ 814 $ 3,471 $ 6,938

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	PROPERTY AND EQUIPMENT Property and equipment, net, consisted of the following: September 30, December 31, (in thousands) Lab equipment $ 2,519 $ 2,489 Leasehold improvements 741 741 Computer hardware and software 461 428 Furniture and fixtures 166 159 Property and equipment, gross 3,887 3,817 Less: accumulated depreciation and amortization (3,291 ) (3,090 ) Property and equipment, net $ 596 $ 727 During the three months ended September 30, 2019 and 2018 , depreciation and amortization expense was $0.1 million . During the nine months ended September 30, 2019 and 2018 , depreciation and amortization expense was $0.2 million . Depreciation and amortization expense is recorded primarily in research and development expense on the condensed consolidated statements of operations and comprehensive loss.

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Accrued Liabilities	ACCRUED LIABILITIES Accrued liabilities consisted of the following: September 30, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 2,607 $ 1,129 Restructuring liability 804 — Accrued employee compensation and related taxes 652 1,704 Accrued other professional service fees 263 246 Accrued legal fees and expenses 258 376 Deferred and accrued facility lease obligations 88 124 Value of liability-classified stock purchase warrants 82 82 Accrued equipment and lab materials — 33 Other accrued liabilities 103 174 Total accrued liabilities $ 4,857 $ 3,868

Notes Payable

Notes Payable	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Notes Payable	NOTES PAYABLE 2017 Silicon Valley Bank Loan Agreement In November 2017, the Company entered into a loan and security agreement with Silicon Valley Bank (the “2017 SVB Loan Agreement”). Upon entry into the 2017 SVB Loan Agreement, the Company borrowed $10.0 million with a 30 -month payment period following an 18 -month interest-only payment period ending in November 2021. Amounts outstanding bear interest at the prime rate ( 5.00% and 5.50% at September 30, 2019 and December 31, 2018 , respectively), with a final payment fee equal to $0.9 million due upon maturity. As of September 30, 2019 , no additional amounts are available under the 2017 SVB Loan Agreement. The Company may elect to prepay prior to maturity all or any portion of the outstanding principal amounts under the 2017 SVB Loan Agreement, subject to a prepayment charge, depending on the date of prepayment or upon the occurrence of an event of default in which the Company’s obligations to repay the outstanding principal is accelerated. The Company’s obligations under the 2017 SVB Loan Agreement are secured by a first-priority security interest, right, and title in all business assets, excluding the Company’s intellectual property, which is subject to a negative pledge. The 2017 SVB Loan Agreement includes customary representations, warranties, and covenants (affirmative and negative), including restrictive covenants that limit the Company’s ability to: encumber or dispose of the collateral securing the loan; change the business of the Company; transfer a material portion of the Company’s assets; acquire other businesses; and merge or consolidate with or into any other business organization; incur additional indebtedness; declare or pay any cash dividend or make a cash distribution on any class of stock or other equity interest; enter into specified material transactions with Company affiliates; make non-ordinary course payments or enter into any amendment regarding subordinated debt of the Company; or become an “investment company” under the Investment Company Act of 1940, as amended; in each case subject to specified exceptions. The 2017 SVB Loan Agreement also includes standard events of default, including payment defaults; breaches of covenants following any applicable cure period; material breaches of representations or warranties; the occurrence of a material adverse change (as defined in the 2017 SVB Loan Agreement); events relating to bankruptcy or insolvency; breaches of material third-party agreements; the occurrence of an unsatisfied material judgment against the Company; and specified governmental actions against the Company, including specified actions by the U.S. Food and Drug Administration. Upon the occurrence of an event of default, Silicon Valley Bank may declare all outstanding obligations immediately due and payable, including a prepayment charge, and take such other actions as are set forth in the 2017 SVB Loan Agreement. Upon the occurrence of an event of default, at the Silicon Valley Bank’s discretion, interest on the 2017 SVB Loan Agreement will accrue at 5.0% above the rate that is otherwise applicable thereto until the earlier of the repayment of the Company’s obligations under the 2017 SVB Loan Agreement or the cure of such event of default. Amounts outstanding under the 2017 SVB Loan Agreement were as follows: September 30, December 31, (in thousands) Principal amount outstanding $ 8,667 $ 10,000 Unamortized debt discount (39 ) (69 ) Accreted final payment fee 603 367 Total note payable 9,231 10,298 Less: current maturities (3,972 ) (2,294 ) Note payable, net of current portion $ 5,259 $ 8,004 Future annual minimum principal payments under the 2017 SVB Loan Agreement as of September 30, 2019 for the respective calendar years are as follows (in thousands): 2019 $ 1,000 2020 4,000 2021 3,667 Total $ 8,667

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Indemnification Agreements The Company has entered into indemnification agreements with each of its directors and officers whereby it has agreed to indemnify such persons for certain events or occurrences while the individual is, or was, serving as a director, officer, employee, or other agent of the Company. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. Employment Agreements The Company has entered into agreements with its executives and certain of its employees that provide for base salary, severance, eligibility for bonuses, and other generally available benefits. The agreements provide that the Company may terminate the employment of its employees, including executives, at any time, with or without cause. If an employee under an employment agreement is terminated without cause, as defined in the employment agreements, or an employee under an employment agreement resigns for good reason, as defined in the employment agreements, then the employee under the employment agreement is entitled to receive, upon the execution of a release agreement, a severance package consisting of one or more of the following provisions: (i) the equivalent of up to 12 months of the employee’s base salary in effect immediately prior to date of termination; (ii) acceleration of vesting of the equivalent of up to 12 months of vesting of the executive’s outstanding unvested stock options or other equity awards that were outstanding as of the effective date of the executive’s employment agreement; and (iii) up to 12 months of continued health coverage. If an executive is terminated without cause or resigns for good reason within one month prior to or 12 months following a change of control, as defined in the employment agreements, the executive is entitled to receive, upon the execution of a release agreement, a severance package consisting of: (i) the equivalent of 12 months of the executive’s base salary in effect immediately prior to date of termination; (ii) the vesting in full of the executive’s then-outstanding stock options or other equity awards subject to time-based vesting; and (iii) 12 months of continued health coverage. Solely in the case of the Company’s Chief Executive Officer, if such termination occurs one month before or 12 months following a change of control, then, upon the execution of a release agreement, the executive is entitled to: (i) the equivalent of 24 months of the executive’s base salary in effect immediately prior to the date of termination; (ii) the vesting in full of the executive’s outstanding stock options or other equity awards subject to time-based vesting; and (iii) 12 months of continued health coverage. License Agreement with the University of Texas As of September 30, 2019 , the Company had one exclusive patent license agreement (the “UT License Agreement”) with the Board of Regents of The University of Texas System (the “University of Texas”). Under the UT License Agreement, the University of Texas granted the Company exclusive and nonexclusive license(s) to certain patent and technology rights. At the time the UT License Agreement was entered into, the University of Texas was a minority stockholder of the Company. In consideration of rights granted by the University of Texas, the Company is required to: (i) pay a nonrefundable up-front license documentation fee in the amount of $10 thousand per license; (ii) pay an annual license maintenance fee in the amount of $10 thousand per license starting one year from the date of each agreement; (iii) reimburse the University of Texas for actual costs incurred in conjunction with the filing, prosecution, enforcement, and maintenance of patent rights prior to the effective date; and (iv) bear all future costs of and manage the filing, prosecution, enforcement, and maintenance of patent rights. During the three and nine months ended September 30, 2019 and 2018 , the Company incurred immaterial up-front and maintenance fees, which were recorded as research and development expense. All costs related to the filing, prosecution, and maintenance of patent and technology rights are recorded as general and administrative expense when incurred. Under the terms of the UT License Agreement, the Company may be obligated to make the following future milestone payments for each licensed product candidate: (i) up to approximately $0.6 million upon the initiation of defined clinical trials; (ii) $2.0 million upon regulatory approval in the United States; and (iii) $0.5 million per region upon regulatory approval in other specified regions. Additionally, if the Company or any of its sublicensees successfully commercializes any product candidate subject to the UT License Agreement, it is responsible for royalty payments in the low-single digits based upon net sales of such licensed products and payments at a percentage in the mid-teens of any sublicense income, subject to specified exceptions. The University of Texas’s right to these royalty payments will expire as to each license agreement upon the expiration of the last patent claim subject to the applicable UT License Agreement. In August 2018, the Company met its first specified milestone and made an immaterial milestone payment to the University of Texas. During the three and nine months ended September 30, 2019 , the Company did not incur any milestone payments. The Company incurred $0.1 million in milestone payments to the University of Texas during the nine months ended September 30, 2018, and no milestone payments during the three months ended September 30, 2018 . The license term extends on a product-by-product and country-by-country basis until the expiration of the last to expire of the licensed patents that covers such product in such country. Upon expiration of the royalty payment obligation, the Company will have a fully-paid license in such country. The Company may also terminate each UT License Agreement for convenience upon a specified number of days’ prior notice to the University of Texas. The University of Texas also has the right to earlier terminate the UT License Agreement after a defined date under specified circumstances where the Company has effectively abandoned its research and development efforts or has no sales. The UT License Agreement will terminate under customary termination provisions including automatic termination upon the Company’s bankruptcy or insolvency, upon notice of an uncured material breach, and upon mutual written consent. All charges incurred under the UT License Agreement have been expensed to date due to the uncertainty as to future economic benefit from the acquired rights. License Agreement with Roche Innovation Center Copenhagen A/S (formerly Santaris Pharma A/S) The Company is party to a license agreement with Santaris Pharma A/S, which subsequently changed its name to Roche Innovation Center Copenhagen A/S (“RICC”), which was acquired by F. Hoffmann-La Roche Ltd (“Roche”), in 2014 and subsequently changed its name to RICC. The agreement was entered into in June 2010, was amended in October 2011, amended and restated in December 2012, and further amended in August 2019 (the “RICC License Agreement”). At the time the RICC License Agreement was entered into, Roche was a minority stockholder of the Company. Under the RICC License Agreement, the Company has received exclusive and nonexclusive licenses from RICC to use specified technology of RICC (the “RICC Technology”) for specified uses, including research, development, and commercialization of pharmaceutical products using this technology worldwide. Under the RICC License Agreement, the Company has the right to develop and commercialize the RICC Technology directed to four specified targets and the option to obtain exclusive product licenses for up to six additional targets. The acquisition of Santaris Pharma A/S by Roche was considered a change of control under the RICC License Agreement, and as such, certain terms and conditions of the RICC License Agreement changed, as contemplated and in accordance with the RICC License Agreement. These changes primarily relate to milestone payments reflected in the disclosures below. If the Company exercises its option to obtain additional product licenses or to replace the target families, it will be required to make additional payments to RICC. Under the terms of the RICC License Agreement, milestone payments were previously decreased by a specified percentage as a result of the change of control by RICC referenced above. The Company is obligated to make milestone payments for each licensed product of up to $5.2 million , which is inclusive of a potential product license option fee. Certain of these milestones will be increased by a specified percentage if the Company undergoes a change of control as defined under the RICC License Agreement. If the Company grants a third party a sublicense to the RICC Technology, it is required to remit to Roche up to a specified percentage of the up-front, milestone, and other specified payments it receives under its sublicense, and if such sublicense covers use of the RICC Technology in the United States or the entire European Union, the Company will not have any further obligation to pay the fixed milestone payments noted above. During the nine months ended September 30, 2019 and 2018, the Company incurred $0.1 million and $0.7 million , respectively, of expense related to a milestone reached, which is included in research and development expense in the Company’s condensed consolidated statements of operations and comprehensive loss. No milestone payments were made during the three months ended September 30, 2019 and 2018. If the Company or its sublicensee successfully commercializes any product candidate subject to the RICC License Agreements, then RICC is entitled to royalty payments in the mid-single digits on the net sales of such product, provided that if such net sales are made by a sublicensee under the RICC License Agreement, RICC is entitled to royalty payments equal to the lesser of a percentage in the mid-single digits on the net sales of such product or a specified percentage of the royalties paid to the Company by such sublicensee, subject to specified restrictions. The Company is obligated to make any such royalty payments until the later of: (i) a specified anniversary of the first commercial sale of the applicable product or (ii) the expiration of the last valid patent claim licensed by RICC under the RICC License Agreement underlying such product. Upon the occurrence of specified events, the royalty owed to RICC will be decreased by a specified percentage. The RICC License Agreement will terminate upon the latest of the expiration of all of RICC’s royalty rights, the termination of the last Miragen target, or the expiration of its right to obtain a product license for a new target under the RICC License Agreement. The Company may also terminate the RICC License Agreement for convenience upon a specified number of days’ prior notice to RICC, subject to specified terms and conditions. Either party may terminate the RICC License Agreement upon an uncured material breach by the other party and RICC may terminate the RICC License Agreement upon the occurrence of other specified events immediately or after such event is not cured within a specified number of days, as applicable. All charges incurred under the RICC License Agreement have been expensed to date due to the uncertainty as to future economic benefit from the acquired rights. During the three and nine months ended September 30, 2019 , the Company made no payments to RICC for raw materials to be used in its drug manufacturing process. During the three months ended September 30, 2018 , the Company made no payments to RICC for raw materials, and during the nine months ended September 30, 2018 , the Company made $0.3 million in payments to RICC for raw materials. Subcontract Agreement with Yale University The Company is party to a subcontract agreement that began in October 2014 and a subaward agreement that began in March 2015 (the “Yale Agreements”) with Yale University (“Yale”), which were subsequently amended. Under the Yale Agreements, the Company is providing specified services regarding the development of a proprietary compound that targets microRNA-29 in the indication of idiopathic pulmonary fibrosis. Yale entered into the Yale Agreements in connection with a grant that Yale received from the National Institutes of Health (“NIH”) for the development of a microRNA-29 mimic as a potential therapy for pulmonary fibrosis. In consideration of the Company’s services under the Yale Agreements, Yale has agreed to reimburse the Company up to a specified amount over five years , subject to the availably of funds under the grant and continued eligibility. Under the terms of the Yale Agreements, the Company retains all rights to any and all intellectual property developed solely by the Company in connection with the Yale Agreements. Yale has also agreed to provide the Company with an exclusive option to negotiate in good faith for an exclusive, royalty-bearing license from Yale for any intellectual property developed by Yale or jointly by the parties under the Yale Agreements. Yale is responsible for filing, prosecuting, and maintaining foreign and domestic patent applications and patents on all inventions jointly developed by the parties under the Yale Agreements. Through September 30, 2019 , the Company received $0.9 million under the Yale Agreements. The Yale Agreements terminate automatically on the date that Yale delivers its final research report to the NIH under the terms of the grant underlying the Yale Agreements. Each party may also terminate the Yale Agreements upon a specified number of days’ notice in the event that the NIH’s grant funding is reduced or terminated or upon material breach by the other party. License Agreements with the t2cure GmbH The Company is party to a license and collaboration agreement (the “t2cure Agreement”) that began in October 2010 with t2cure GmbH (“t2cure”), which was subsequently amended. Under the t2cure Agreement, the Company received a worldwide, royalty-bearing, and exclusive license to specified patent and technology rights relating to microRNA-92. In consideration of rights granted by t2cure, an up-front fee of $46 thousand was paid and the Company is obligated to: (i) pay an annual license maintenance fee in the amount of €3 thousand ( $3 thousand as of September 30, 2019 ); and (ii) reimburse t2cure for costs incurred in conjunction with the filing, prosecution, enforcement, and maintenance of patent rights. Under the terms of the t2cure Agreement, the Company is obligated to make the following future milestone payments for each licensed product, as defined in the t2cure Agreement: (i) up to approximately $0.7 million upon the initiation of certain defined clinical trials; (ii) $2.5 million upon regulatory approval in the United States; and (iii) up to $1.5 million per region upon regulatory approval in the European Union or Japan. Additionally, if the Company or any of its sublicensees successfully commercialize any product candidate subject to the t2cure Agreement, it is responsible for royalty payments equal to percentages in the low-single digits upon net sales of licensed products, and under specified circumstances, sublicense fees equal to a percentage in the low twenties of sublicense income received by it. The Company is obligated to make any such royalty payment until the later of: (i) the tenth anniversary of the first commercial sale of the applicable product or (ii) the expiration of the last valid claim to a patent licensed by t2cure under the t2cure Agreement covering such product. If such patent claims expire prior to the end of the ten -year term, then the royalty owed to t2cure will be decreased by a specified percentage. The Company also has the right to decrease its royalty payments by a specified percentage for royalties paid to third parties for licenses to certain third-party intellectual property. The license term extends on a country-by-country basis until the later of: (i) the tenth anniversary of the first commercial sale of a licensed product in a country and (ii) the expiration of the last to expire valid claim that claims such licensed product in such country. Upon expiration of the royalty payment obligation, the Company will have a fully-paid license in such country. The Company has the right to terminate the t2cure Agreement at will, on a country-by-country basis, after 60 days’ written notice. The t2cure Agreement will also automatically terminate upon the Company’s bankruptcy or insolvency or upon notice of an uncured material breach. All charges incurred under the t2cure Agreement have been expensed to date, due to the uncertainty as to future economic benefit from the acquired rights. License Agreement with The Brigham and Women’s Hospital The Company is party to an exclusive patent license agreement (the “BWH License Agreement”) with The Brigham and Women’s Hospital (“BWH”). The BWH License Agreement began in May 2016 and provides the Company with an exclusive, worldwide license, including a right to sublicense, to specified patent rights and a nonexclusive, worldwide license, including a right to sublicense, to specified technology rights of BWH, each related to certain microRNAs believed to be involved in various neurodegenerative disorders. As consideration for these rights, the Company is obligated to pay a specified annual license fee. BWH is also entitled to milestone payments of up to approximately $2.6 million for each of the Company’s product candidates developed based on the patent rights subject to the BWH License Agreement plus a one-time sales milestone payment of $0.3 million for all product candidates developed based on the patent rights subject to the BWH License Agreement. If the Company were to successfully commercialize any product candidate subject to the BWH License Agreement, then BWH is entitled to royalty payments in the low-single digits on the net sales of such product. BWH’s right to these royalty payments will expire on a product-by-product and country-by-country basis upon the expiration of the last patent claim in such country that is subject to the BWH License Agreement and covers the product, and the Company’s license to such product in such country will become fully paid at such time. BWH is also entitled to a percentage in the low-double digits of any sublicense income from such product, subject to specified exceptions. The Company is also responsible for all costs associated with the preparation, filing, prosecution, and maintenance of the patent rights subject to the BWH License Agreement. Additionally, the Company is obligated to use commercially-reasonable efforts to develop a product under the BWH License Agreement and to meet specified diligence milestones thereunder. The BWH License Agreement will terminate upon the expiration of all issued patents and patent applications subject to the patent rights under the agreement. The Company may also terminate the BWH License Agreement for convenience upon a specified number of days’ prior notice to BWH. BWH may terminate the BWH License Agreement upon a breach by the Company of its payment obligations and upon the occurrence of other specified events that are not cured within a specified number of days, provided that such termination is automatic upon the Company’s bankruptcy or insolvency. During the nine months ended September 30, 2019 and 2018 , the Company paid immaterial annual license fees to BWH under the BWH License Agreement. During the three months ended September 30, 2019 and 2018 , the Company did not make any license fee payments to BWH under the BWH License Agreement. Facility Lease The Company is party to a multi-year, noncancelable lease agreement that began in December 2010 for its current office and lab space. The agreement was subsequently amended to extend the term through August 2020. The lease agreement includes rent escalation clauses through the lease term and a Company option to extend the lease term for up to two terms of three years each. Minimum base lease payments, including the impact of tenant improvement allowances, under the operating lease are recognized on a straight-line basis over the full term of the lease. During the nine months ended September 30, 2019 and 2018 , rent expense was $0.2 million and $0.3 million , respectively. During the three months ended September 30, 2019 and 2018 , rent expense was $0.1 million . The Company is also required to pay for operating expenses related to the leased space, which were $0.3 million and $0.2 million for the nine months ended September 30, 2019 and 2018, respectively. Operating expenses were $0.1 million during the three months ended September 30, 2019 and 2018 . Future annual minimum payments under the lease as of September 30, 2019 for the respective calendar year were as follows (in thousands): 2019 $ 102 2020 277 Total $ 379

Capital Stock

Capital Stock	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Capital Stock	CAPITAL STOCK Common Stock The Company is authorized to issue 105,000,000 shares of its stock, of which 100,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as preferred stock with a par value of $0.01 per share. The number of authorized shares of Common Stock may be increased or decreased by the affirmative vote of the holders of a majority of the Company’s stock who are entitled to vote. Each share of Common Stock is entitled to one vote. The holders of Common Stock are entitled to receive dividends when and as declared or paid by its board of directors. Common Stock Purchase Agreement In August 2018 , the Company and The Leukemia & Lymphoma Society, Inc. (“LLS”) entered into a Common Stock Purchase Agreement (the “LLS Stock Purchase Agreement”), which was subsequently assigned pursuant to LLS TAP Miragen, LLC (“LLS TAP”) pursuant to an Assignment and Assumption Agreement, effective October 28, 2019 (the “Assignment Agreement”), for the sale of up to $5.0 million of shares of Common Stock to LLS and its affiliates in a private placement (the “Offering”). Under the terms of the LLS Stock Purchase Agreement, the Company expects to raise up to approximately $5.0 million in gross proceeds by selling shares of Common Stock to LLS and its affiliates in up to five separate closings. The initial closing of the Offering was held on August 6, 2018 . At the initial closing, the Company issued 150,987 shares of Common Stock at a price per share equal to $ 6.62 . Subsequently, on October 31, 2019, the Company issued 606,364 shares of Common Stock to LLS TAP at a price per share of approximately $0.82 in a subsequent closing. The Company has received aggregate net proceeds of approximately $1.4 million after expenses incurred in connection with the Offering. The price per share of Common Stock to be sold in any subsequent closing will be equal to the average of the volume weighted-average prices of a share of Common Stock on the Nasdaq Capital Market for the three trading days beginning with the first trading day after the date of achievement of the relevant milestone for each such closing. Each closing is subject to the Company’s achievement of specified operational milestones under the LLS Stock Purchase Agreement and other customary closing conditions, provided, however, that each such closing must be completed prior to December 31, 2021. Common Stock Sales Agreement In March 2017 , the Company entered into an at the market issuance Common Stock Sales Agreement (the “ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its Common Stock having an aggregate offering price of up to $50.0 million through Cowen as its sales agent. Cowen may sell the Common Stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, including without limitation sales made by means of ordinary brokers’ transactions on The Nasdaq Capital Market or otherwise at market prices prevailing at the time of sale, in block transactions, or as otherwise directed by the Company. Cowen will use commercially-reasonable efforts to sell the Common Stock from time to time, based upon instructions from the Company (including any price, time, or size limits or other customary parameters or conditions the Company may impose). The Company will pay Cowen a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the ATM Agreement. The Company also has provided Cowen with customary indemnification rights. The Company is not obligated to make any sales of Common Stock under the ATM Agreement. The offering of shares of Common Stock pursuant to the ATM Agreement will terminate upon the earlier of: (i) the sale of all Common Stock subject to the ATM Agreement or (ii) termination of the ATM Agreement in accordance with its terms. During the nine months ended September 30, 2019 , the Company sold, pursuant to the terms of the ATM Agreement, 144,241 shares of Common Stock, at a weighted average price of $2.95 per share, for aggregate net proceeds of approximately $0.4 million , including commissions to Cowen as sales agent. Since March 2017 and through September 30, 2019 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 1,357,627 shares of Common Stock, at a weighted average price of $8.13 per share, for aggregate net proceeds of approximately $10.6 million , including initial expenses for executing the “at the market offering” and commissions to Cowen as sales agent. Common Stock Public Offering In February 2018, the Company entered into an underwriting agreement relating to a public offering of its Common Stock, pursuant to which the Company sold 7,414,996 shares of Common Stock at a price of $5.50 per share, which resulted in net proceeds of approximately $37.9 million after deducting underwriting commissions and discounts and other offering expenses payable by the Company. Series Preferred As of September 30, 2019 , the Company had no shares of preferred stock outstanding and had not designated any class or series of preferred stock. Under the Company’s amended and restated certificate of incorporation, the Company’s board of directors has the authority to designate and issue up to 5,000,000 shares of preferred stock, at its discretion, in one or more classes or series and to fix the powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, and liquidation preferences, without further vote or action by the Company’s stockholders. WARRANTS As of September 30, 2019 , the Company had 46,522 Common Stock warrants outstanding at a weighted average exercise price of $17.93 . A summary of outstanding Common Stock purchase warrants as of September 30, 2019 is as follows: Number of Underlying Shares Exercise Price Expiration Date 10,707 $52.50 2020 11,718 $8.53 2025 24,097 $7.15 2024 46,522 Stock purchase warrant activity is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2018 49,349 $ 27.65 Expiries (2,827 ) $ 187.50 Outstanding at September 30, 2019 46,522 $ 17.93

Warrants

Warrants	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Warrants	CAPITAL STOCK Common Stock The Company is authorized to issue 105,000,000 shares of its stock, of which 100,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as preferred stock with a par value of $0.01 per share. The number of authorized shares of Common Stock may be increased or decreased by the affirmative vote of the holders of a majority of the Company’s stock who are entitled to vote. Each share of Common Stock is entitled to one vote. The holders of Common Stock are entitled to receive dividends when and as declared or paid by its board of directors. Common Stock Purchase Agreement In August 2018 , the Company and The Leukemia & Lymphoma Society, Inc. (“LLS”) entered into a Common Stock Purchase Agreement (the “LLS Stock Purchase Agreement”), which was subsequently assigned pursuant to LLS TAP Miragen, LLC (“LLS TAP”) pursuant to an Assignment and Assumption Agreement, effective October 28, 2019 (the “Assignment Agreement”), for the sale of up to $5.0 million of shares of Common Stock to LLS and its affiliates in a private placement (the “Offering”). Under the terms of the LLS Stock Purchase Agreement, the Company expects to raise up to approximately $5.0 million in gross proceeds by selling shares of Common Stock to LLS and its affiliates in up to five separate closings. The initial closing of the Offering was held on August 6, 2018 . At the initial closing, the Company issued 150,987 shares of Common Stock at a price per share equal to $ 6.62 . Subsequently, on October 31, 2019, the Company issued 606,364 shares of Common Stock to LLS TAP at a price per share of approximately $0.82 in a subsequent closing. The Company has received aggregate net proceeds of approximately $1.4 million after expenses incurred in connection with the Offering. The price per share of Common Stock to be sold in any subsequent closing will be equal to the average of the volume weighted-average prices of a share of Common Stock on the Nasdaq Capital Market for the three trading days beginning with the first trading day after the date of achievement of the relevant milestone for each such closing. Each closing is subject to the Company’s achievement of specified operational milestones under the LLS Stock Purchase Agreement and other customary closing conditions, provided, however, that each such closing must be completed prior to December 31, 2021. Common Stock Sales Agreement In March 2017 , the Company entered into an at the market issuance Common Stock Sales Agreement (the “ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its Common Stock having an aggregate offering price of up to $50.0 million through Cowen as its sales agent. Cowen may sell the Common Stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, including without limitation sales made by means of ordinary brokers’ transactions on The Nasdaq Capital Market or otherwise at market prices prevailing at the time of sale, in block transactions, or as otherwise directed by the Company. Cowen will use commercially-reasonable efforts to sell the Common Stock from time to time, based upon instructions from the Company (including any price, time, or size limits or other customary parameters or conditions the Company may impose). The Company will pay Cowen a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the ATM Agreement. The Company also has provided Cowen with customary indemnification rights. The Company is not obligated to make any sales of Common Stock under the ATM Agreement. The offering of shares of Common Stock pursuant to the ATM Agreement will terminate upon the earlier of: (i) the sale of all Common Stock subject to the ATM Agreement or (ii) termination of the ATM Agreement in accordance with its terms. During the nine months ended September 30, 2019 , the Company sold, pursuant to the terms of the ATM Agreement, 144,241 shares of Common Stock, at a weighted average price of $2.95 per share, for aggregate net proceeds of approximately $0.4 million , including commissions to Cowen as sales agent. Since March 2017 and through September 30, 2019 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 1,357,627 shares of Common Stock, at a weighted average price of $8.13 per share, for aggregate net proceeds of approximately $10.6 million , including initial expenses for executing the “at the market offering” and commissions to Cowen as sales agent. Common Stock Public Offering In February 2018, the Company entered into an underwriting agreement relating to a public offering of its Common Stock, pursuant to which the Company sold 7,414,996 shares of Common Stock at a price of $5.50 per share, which resulted in net proceeds of approximately $37.9 million after deducting underwriting commissions and discounts and other offering expenses payable by the Company. Series Preferred As of September 30, 2019 , the Company had no shares of preferred stock outstanding and had not designated any class or series of preferred stock. Under the Company’s amended and restated certificate of incorporation, the Company’s board of directors has the authority to designate and issue up to 5,000,000 shares of preferred stock, at its discretion, in one or more classes or series and to fix the powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, and liquidation preferences, without further vote or action by the Company’s stockholders. WARRANTS As of September 30, 2019 , the Company had 46,522 Common Stock warrants outstanding at a weighted average exercise price of $17.93 . A summary of outstanding Common Stock purchase warrants as of September 30, 2019 is as follows: Number of Underlying Shares Exercise Price Expiration Date 10,707 $52.50 2020 11,718 $8.53 2025 24,097 $7.15 2024 46,522 Stock purchase warrant activity is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2018 49,349 $ 27.65 Expiries (2,827 ) $ 187.50 Outstanding at September 30, 2019 46,522 $ 17.93

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION Equity Incentive Plans As of September 30, 2019 , there were 1,459,885 options outstanding and no remaining equity awards available for future issuances under the 2008 Plan. All awards granted under the 2008 Plan that, after February 13, 2017, expire or terminate for any reason prior to exercise or settlement, are forfeited, or are reacquired, withheld, or not issued to satisfy a tax withholding obligation or to satisfy the exercise price of a stock award, will become available for grant under the 2016 Plan in accordance with its terms. The 2016 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, other stock awards, and performance awards that may be settled in cash, stock, or other property. All employees and non-employee directors are eligible to participate in the 2016 Plan and may receive all types of awards other than incentive stock options. Incentive stock options may be granted under the 2016 Plan only to employees (including officers) and employees of the Company’s affiliates. The aggregate number of shares of Common Stock that may be issued under the 2016 Plan will not exceed 4,182,404 shares, which number is the sum of: (i) 1,681,294 shares, plus (ii) the number of shares subject to outstanding stock awards that were granted under the 2008 Plan, that, from and after February 13, 2017, expire or terminate for any reason prior to exercise or settlement, are forfeited because of the failure to meet a contingency or condition required to vest such shares, or are reacquired, withheld, or not issued to satisfy a tax withholding obligation in connection with an award or to satisfy the purchase price or exercise price of a stock award, if any, as such shares become available from time to time, plus (iii) shares from automatic increases to the share reserve, as described in more detail below. In accordance with the 2016 Plan, the share reserve will automatically increase on January 1 of each year, for a period of not more than ten years , commencing on January 1 of the year following the year in which the effective date of the 2016 Plan occurs, and ending on (and including) January 1, 2026, in an amount equal to 4% of the shares of Common Stock outstanding on December 31 of the preceding calendar year; however, the board of directors or compensation committee may act prior to January 1 of a given year to provide that there will be no January 1 increase in the share reserve for such year or that the increase in the share reserve for such year will be a lesser number of shares of Common Stock than would otherwise occur pursuant to the automatic increase. On January 1, 2019 and 2018, the share reserve automatically increased by 1,233,578 and 902,720 shares, respectively. As of September 30, 2019 , there were outstanding stock options to purchase 2,574,463 shares of Common Stock and 1,290,930 shares of Common Stock available for issuance pursuant to the terms under the 2016 Plan. Options granted under the 2008 Plan and 2016 Plan have an exercise price equal to the market value of the Common Stock at the date of grant and expire ten years from the date of grant. Generally, options vest 25% on the first anniversary of the vesting commencement date and 75% ratably in equal monthly installments over the remaining 36 months . The Company has also granted options that vest in equal monthly or quarterly amounts over periods up to 48 months . A summary of Common Stock option activity is as follows: Number of Options Weighted Average Exercise Price Outstanding at December 31, 2018 3,527 $ 5.76 Granted 1,078 $ 2.89 Exercised (142 ) $ 0.60 Forfeited or expired (429 ) $ 5.49 Outstanding at September 30, 2019 4,034 $ 5.20 Fair Value Assumptions The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options granted under its equity compensation plans. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility, and expected lives of the options. Because the Company has a limited history of stock purchase and sale activity, expected volatility is based on historical data from public companies that are similar to the Company in size and nature of operations. The Company will continue to use similar entity volatility information until its historical volatility is relevant to measure expected volatility for option grants. The Company accounts for forfeitures as they occur. The risk-free rate for periods within the contractual life of each option is based on the U.S. Treasury yield curve in effect at the time of the grant for a period commensurate with the expected term of the grant. The expected term (without regard to forfeitures) for options granted represents the period of time that options granted are expected to be outstanding and is derived from the contractual terms of the options granted and expected option-exercise behaviors. The fair value of the underlying Common Stock is based on the closing price of the Common Stock on The Nasdaq Capital Market at the date of grant. Stock Options Granted to Employees and Directors The weighted-average grant-date fair value of options granted to the Company’s employees and members of its board of directors during the three and nine months ended September 30, 2019 and 2018 was $2.31 and $5.51 , respectively. The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Nine Months Ended 2019 2018 Expected term, in years 6.35 6.33 Expected volatility 98.8 % 84.9 % Risk-free interest rate 2.5 % 2.6 % Expected dividend yield — % — % Weighted-average exercise price $ 2.97 $ 7.48 Stock Options Granted to Non-Employees (Other than Directors) The Company adopted ASU 2018-07 on January 1, 2019. Prior to 2019, the Company determined the value of Common Stock options issued to non-employees (other than members of its board of directors) using the Black-Scholes option pricing model and adjusting the value of such awards to current fair value each reporting period until the awards were vested or a performance commitment had otherwise been reached. After adoption of ASU 2018-07, non-employee stock options are valued at the award’s inception using grant-date fair value, in the same manner of stock options granted to employees. Any outstanding and partially vested non-employee stock option shares were remeasured on January 1, 2019. The adoption of this standard had an immaterial impact on the Company’s condensed consolidated financial statements. No Common Stock options were issued to non-employees (other than members of the Company’s board of directors) during the three and nine months ended September 30, 2019 and 2018 . Employee Stock Purchase Plan The 2016 Employee Stock Purchase Plan (“ESPP”) allows qualified employees to purchase shares of Common Stock at a price equal to 85% of the lower of: (i) the closing price at the beginning of the offering period or (ii) the closing price at the end of the offering period. The Company expects that a new 6-month offering period will begin each August 22 and February 22. As of September 30, 2019 , the Company had 622,347 shares available for issuance and 121,890 shares had been issued under the ESPP. Share-Based Compensation Expense Share-based compensation related to all equity awards issued pursuant to the 2008 Plan and 2016 Plan and for estimated shares to be issued under the ESPP for the purchase periods active during each respective period is included in the condensed consolidated statements of operations and comprehensive loss as follows: Nine Months Ended 2019 2018 (in thousands) Research and development $ 1,175 $ 933 General and administrative 1,792 1,809 Total share-based compensation expense $ 2,967 $ 2,742 As of September 30, 2019 , the Company had $6.4 million of total unrecognized employee and non-employee share-based compensation costs, which the Company expects to recognize over a weighted-average remaining period of 2.25 years.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	NET LOSS PER SHARE Basic net loss per share is computed by dividing the net loss available to common stockholders by the weighted-average number of Common Stock outstanding. Diluted net loss per share is computed similarly to basic net loss per share except that the denominator is increased to include the number of additional shares of Common Stock that would have been outstanding if the potential shares of Common Stock had been issued and if the additional shares of Common Stock were dilutive. Diluted net loss per share is the same as basic net loss per share of Common Stock, as the effects of potentially dilutive securities are antidilutive. Potentially dilutive securities include the following: September 30, 2019 2018 (in thousands) Options to purchase Common Stock 4,034 3,517 Warrants to purchase Common Stock 47 49 Total 4,081 3,566

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Miragen Therapeutics Europe Limited and miRagen Therapeutics S.à.r.l., each of which were formed for the sole purpose of submitting regulatory filings in Europe. The Company’s subsidiaries have no employees or operations. The financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2019 , or for any other interim period, or for any other future year. The balance sheet as of December 31, 2018 has been derived from audited consolidated financial statements at that date but does not include all the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements of the Company and the notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2018 , filed with the SEC on March 14, 2019. The Company’s management performed an evaluation of its activities through the date of filing of these financial statements and concluded that there are no subsequent events requiring disclosure, other than as disclosed.
Use of Estimates	Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with U.S. GAAP, which requires it to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Although these estimates are based on the Company’s knowledge of current events and actions it may take in the future, actual results may ultimately differ from these estimates and assumptions.
Revenue Recognition	Revenue Recognition Effective January 1, 2019, the Company adopted the provisions set forth in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”), using the modified retrospective transition method. Under this method, there was no cumulative effect of initially applying ASC 606 to all contracts as of the date of the adoption. The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license, or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such agreements. The terms of these agreements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; developmental, clinical, regulatory, and commercial sales milestone payments; and royalties on net sales of licensed products. In Accordance with ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized, for agreements within the scope of ASC 606, the Company performs the following five steps: (i) identification of the goods or services within the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct within the terms of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the identified performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s agreements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. Performance obligations are promises in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available, and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each agreement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenue in the period of adjustment. For agreements that include sales-based royalties, including milestone payments based on the level of sales, and 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 of the Company’s collaboration or strategic alliance agreements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction, and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes 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, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.
Share-Based Compensation	Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees and members of its board of directors under its 2008 Equity Incentive Plan (the “2008 Plan”) and under its 2016 Equity Incentive Plan (the “2016 Plan”) by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model. The Company recognizes share-based compensation expense on a straight-line basis over the vesting term. Prior to 2019, the Company accounted for stock options issued to non-employees (other than board members) by valuing each award using the Black-Scholes option pricing model and remeasuring the awards to the current fair value until the awards vested. Beginning in 2019, the Company accounts for share-based compensation expense related to stock options granted to non-employees by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model and recognizing share-based compensation expense on a straight-line basis over the vesting term.
Research and Development	Research and Development Research and development costs are expensed as incurred in performing research and development activities. The costs include employee-related expense including salaries, benefits, share-based compensation, fees for acquiring and maintaining licenses under third-party license agreements, consulting fees, market research, costs of research and development activities conducted by third parties on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, and facilities and overhead costs. The Company records research and development expense in the period in which the Company receives or takes ownership of the applicable goods or when the applicable services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records up-front and milestone payments to acquire and retain contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights. The Company considers future economic benefits from acquired contractual rights to licensed technology to be uncertain until such a drug candidate is approved for sale by the U.S. Food and Drug Administration or when other significant risk factors are abated.
Clinical Trials and Preclinical Study Accruals	Clinical Trial and Preclinical Study Accruals The Company makes estimates of accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on certain facts and circumstances at that time. The Company’s accrued expenses for clinical trials and preclinical studies are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and other providers. Payments under the Company’s agreements with external service providers depend on a number of factors, such as site initiation, patient screening, enrollment, delivery of reports, and other events. In accruing for these activities, the Company obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to the Company’s research and development expenses may be necessary in future periods as its estimates change.
Cash and Cash Equivalents	Cash and Cash Equivalents All highly-liquid investments that have maturities of 90 days or less at the date of purchase are classified as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments.
Investments	Investments The Company has designated its investments as available-for-sale securities and accounts for them at their respective fair values. The securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are readily available for use in current operations are classified as short-term available-for-sale securities and are reported as a component of current assets in the accompanying condensed consolidated balance sheets. Securities that are classified as available-for-sale are measured at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders’ equity until their disposition. The Company reviews available-for-sale securities at the end of each period to determine whether they remain available-for-sale based on its then current intent. The cost of securities sold is based on the specific identification method. The securities are subject to a periodic impairment review. An impairment charge would occur when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary.
Fair Value Measurements	Fair Value of Financial Instruments Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate their fair value due to the short-term nature of their maturities, such as cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses. The carrying amount of the Company’s note payable approximates its fair value (a Level 2 fair value measurement), reflecting interest rates currently available to the Company. The Company accounts for warrants to purchase its stock pursuant to ASC Topic 470, Debt, and ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for Common Stock as liabilities or equity. The warrants classified as liabilities are reported at their estimated fair value and any changes in fair value are reflected in interest expense and other related expenses. The warrants classified as equity are reported at their estimated fair value with no subsequent remeasurement. Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts. The Company invests its excess cash primarily in deposits and money market funds held with one financial institution.
Property and Equipment	Property and Equipment The Company carries its property and equipment at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the life of the lease (including any renewal periods that are deemed to be reasonably assured) or the estimated useful life of the assets. Construction in progress is not depreciated until placed in service. Repairs and maintenance costs are expensed as incurred and expenditures for major improvements are capitalized.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company assesses the carrying amount of its property and equipment whenever events or changes in circumstances indicate the carrying amount of such assets may not be recoverable.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is antidilutive.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments. Unrealized accumulated comprehensive gains or losses are reflected as a separate component in the statement of stockholders’ equity.
Income Taxes	Income Taxes The Company accounts for income taxes by using an asset and liability method of accounting for deferred income taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is recorded to the extent it is more likely than not that a deferred tax asset will not be realized. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. The Company’s significant deferred tax assets are for net operating loss carryforwards, tax credits, accruals and reserves, and capitalized start-up costs. The Company has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, the Company has concluded that it is more likely than not that its deferred tax assets will not be realized. The Company has no unrecognized tax benefits. The Company classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations and comprehensive loss as general and administrative expenses. No such expenses have been recognized during the three and nine months ended September 30, 2019 and 2018 . The Tax Cuts and Jobs Act of 2017 (“Tax Act”) was signed into law on December 22, 2017. The Tax Act includes significant changes to the U.S. corporate income tax system, including: (i) a federal corporate rate reduction from 35% to 21%; (ii) limitations on the deductibility of interest expense and executive compensation; (iii) elimination of the corporate alternative minimum tax (“AMT”) and a change in how existing AMT credits can be realized; (iv) change in the rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017; (v) reduction of the orphan drug credit from 50% to 25%; and (vi) transition of U.S. international taxation from a worldwide tax system to a territorial tax system. The Tax Act did not have a material impact on the condensed consolidated financial statements primarily due to the valuation allowance recorded against its net deferred tax assets.
Segment Information	Segment Information The Company operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with the Company’s partners are denominated in U.S. dollars, except where noted.
Recent Accounting Pronouncements	Recent Accounting Pronouncements – Adopted Revenue Recognition In May 2014, the FASB issued Accounting Standards Update ( “ ASU”) No. 2014-09 , Revenue from Contracts with Customers (Accounting Standards Codification Topic 606) , and has issued a number of clarifying ASUs subsequently, all of which outline a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.” The standard provides enhancements to the quality and consistency of how revenue is reported by companies, while also improving comparability in the financial statements of companies reporting using International Financial Reporting Standards or U.S. GAAP. The new standard requires enhanced revenue disclosures, provides guidance for transactions that were not previously addressed comprehensively, and improves guidance for multiple-element arrangements. Effective January 1, 2019, the Company adopted ASC 606 using the modified retrospective method approach, which consists of applying and recognizing the cumulative effect of ASC 606 at the date of initial application and providing certain additional disclosures defined per ASC 606. As part of this adoption, the Company completed its assessment of the Servier Collaboration Agreement under ASC 606. The adoption of ASC 606 did not have a material impact on the Company’s condensed consolidated financial statements, and it did not result in a cumulative adjustment of initially applying ASC 606 to all contracts as of the date of the adoption. Share-based Compensation In June 2018, the FASB issued ASU No. 2018-07, Compensation — Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting , which simplifies the accounting for share-based payments to non-employees by aligning it with the accounting for share-based payments to employees, with specified exceptions. The Company adopted this standard on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s condensed consolidated financial statements. Recent Accounting Pronouncements – Not Yet Adopted Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842) and subsequent amendments to the initial guidance: ASU No. 2017-13, ASU No. 2018-10, and ASU No. 2018-11 (collectively, “Topic 842”). Topic 842 requires companies to generally recognize on the balance sheet operating and financing lease liabilities and corresponding right-of-use assets. The standard is effective for the Company for interim and annual reports beginning after December 15, 2019, with early adoption permitted. At adoption, this update will be applied using a modified retrospective approach, with an option to use certain transition relief. The Company currently expects that its building operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon its adoption of Topic 842, which will increase the Company’s total assets and total liabilities that are reported relative to such amounts prior to adoption. The Company is continuing to evaluate the full impact of this standard on its condensed consolidated financial statements. Fair Value Measurement In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which modifies the disclosure requirements of fair value measurements. This standard is effective for the Company in the first quarter of 2020, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this standard on its condensed consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. September 30, 2019 December 31, 2018 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 24,917 $ — $ 32,936 $ — U.S. treasury securities (included in short-term investments) 8,981 — 29,875 — Total assets $ 33,898 $ — $ 62,811 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 82 $ — $ 82 ____________________ (1) The sum of amounts presented for each period above differ from cash and cash equivalents reported in the condensed consolidated balance sheets due to uninvested cash balances and outstanding disbursements and deposits.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. September 30, 2019 December 31, 2018 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 24,917 $ — $ 32,936 $ — U.S. treasury securities (included in short-term investments) 8,981 — 29,875 — Total assets $ 33,898 $ — $ 62,811 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 82 $ — $ 82 ____________________ (1) The sum of amounts presented for each period above differ from cash and cash equivalents reported in the condensed consolidated balance sheets due to uninvested cash balances and outstanding disbursements and deposits.

Cost Restructuring Plan (Tables

Cost Restructuring Plan (Tables)	9 Months Ended
	Sep. 30, 2019
Restructuring and Related Activities [Abstract]
Summary of Restructuring Activity	The following table summarizes restructuring expense during the three and nine months ended September 30, 2019 and 2018 (in thousands): 2019 2018 Retention $ 787 $ — Severance 288 — Other (1) 17 — Total restructuring charges $ 1,092 $ — ____________________ (1) Other consists of benefits primarily associated with outplacement services and extended medical insurance benefits that are electable by certain employees. Expense for other services is recognized over the period the benefits are incurred. The following table summarizes the Company’s accrued restructuring balance and associated activity (in thousands): December 31, 2018 Additions Cash Payments Adjustments September 30, 2019 Retention $ — $ 787 $ — $ — $ 787 Severance — 288 (288 ) — — Other — 17 — — 17 Total restructuring liability $ — $ 1,092 $ (288 ) $ — $ 804

Strategic Alliance and Collab_2

Strategic Alliance and Collaboration with Servier (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Components of Collaboration Revenue	Collaboration revenue under the Servier Collaboration Agreement consisted of the following: Three Months Ended Nine Months Ended 2019 2018 2019 2018 (in thousands) Milestone payments $ — $ — $ — $ 3,690 Research and development reimbursable costs 625 814 3,471 3,248 Total collaboration revenue $ 625 $ 814 $ 3,471 $ 6,938

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment, net, consisted of the following: September 30, December 31, (in thousands) Lab equipment $ 2,519 $ 2,489 Leasehold improvements 741 741 Computer hardware and software 461 428 Furniture and fixtures 166 159 Property and equipment, gross 3,887 3,817 Less: accumulated depreciation and amortization (3,291 ) (3,090 ) Property and equipment, net $ 596 $ 727

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Components of Accrued Liabilities	Accrued liabilities consisted of the following: September 30, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 2,607 $ 1,129 Restructuring liability 804 — Accrued employee compensation and related taxes 652 1,704 Accrued other professional service fees 263 246 Accrued legal fees and expenses 258 376 Deferred and accrued facility lease obligations 88 124 Value of liability-classified stock purchase warrants 82 82 Accrued equipment and lab materials — 33 Other accrued liabilities 103 174 Total accrued liabilities $ 4,857 $ 3,868

Notes Payable (Tables)

Notes Payable (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Composition of Notes Payable	Amounts outstanding under the 2017 SVB Loan Agreement were as follows: September 30, December 31, (in thousands) Principal amount outstanding $ 8,667 $ 10,000 Unamortized debt discount (39 ) (69 ) Accreted final payment fee 603 367 Total note payable 9,231 10,298 Less: current maturities (3,972 ) (2,294 ) Note payable, net of current portion $ 5,259 $ 8,004
Future Annual Minimum Principal Payments of Notes Payable	Future annual minimum principal payments under the 2017 SVB Loan Agreement as of September 30, 2019 for the respective calendar years are as follows (in thousands): 2019 $ 1,000 2020 4,000 2021 3,667 Total $ 8,667

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future annual minimum payments under the lease as of September 30, 2019 for the respective calendar year were as follows (in thousands): 2019 $ 102 2020 277 Total $ 379

Warrants (Tables)

Warrants (Tables)	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Summary of Warrants	As of September 30, 2019 , the Company had 46,522 Common Stock warrants outstanding at a weighted average exercise price of $17.93 . A summary of outstanding Common Stock purchase warrants as of September 30, 2019 is as follows: Number of Underlying Shares Exercise Price Expiration Date 10,707 $52.50 2020 11,718 $8.53 2025 24,097 $7.15 2024 46,522 Stock purchase warrant activity is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2018 49,349 $ 27.65 Expiries (2,827 ) $ 187.50 Outstanding at September 30, 2019 46,522 $ 17.93

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Stock Option Activity	A summary of Common Stock option activity is as follows: Number of Options Weighted Average Exercise Price Outstanding at December 31, 2018 3,527 $ 5.76 Granted 1,078 $ 2.89 Exercised (142 ) $ 0.60 Forfeited or expired (429 ) $ 5.49 Outstanding at September 30, 2019 4,034 $ 5.20
Fair Value Assumptions for Stock Options	The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Nine Months Ended 2019 2018 Expected term, in years 6.35 6.33 Expected volatility 98.8 % 84.9 % Risk-free interest rate 2.5 % 2.6 % Expected dividend yield — % — % Weighted-average exercise price $ 2.97 $ 7.48
Allocation of Share-based Compensation Expense	Share-based compensation related to all equity awards issued pursuant to the 2008 Plan and 2016 Plan and for estimated shares to be issued under the ESPP for the purchase periods active during each respective period is included in the condensed consolidated statements of operations and comprehensive loss as follows: Nine Months Ended 2019 2018 (in thousands) Research and development $ 1,175 $ 933 General and administrative 1,792 1,809 Total share-based compensation expense $ 2,967 $ 2,742

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities	Potentially dilutive securities include the following: September 30, 2019 2018 (in thousands) Options to purchase Common Stock 4,034 3,517 Warrants to purchase Common Stock 47 49 Total 4,081 3,566

Description of Business - Narra

Description of Business - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents and short-term investments	$ 33,800
Accumulated deficit	$ (158,051)	$ (126,296)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
U.S. treasury securities	$ 9,000	$ 29,900
Level 1
Assets:
Money market funds (included in cash and cash equivalents)	24,917	32,936
Total assets	33,898	62,811
Liabilities:
Common Stock warrants (included in accrued and other liabilities)	0	0
Level 3
Assets:
Money market funds (included in cash and cash equivalents)	0	0
Total assets	0	0
Liabilities:
Common Stock warrants (included in accrued and other liabilities)	82	82
Short-term Investments | Level 1
Assets:
U.S. treasury securities	8,981	29,875
Short-term Investments | Level 3
Assets:
U.S. treasury securities	$ 0	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)segment	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Property, Plant and Equipment [Line Items]
Available-for-sale securities, cost basis	$ 9,000,000		$ 9,000,000		$ 29,900,000
U.S. treasury securities	9,000,000		9,000,000		29,900,000
Unrealized gain	3,000		3,000
Unrealized loss					(3,000)
Impairment charges	0	$ 0	0	$ 0
Accumulated other comprehensive gain (loss)	3,000		3,000		$ (3,000)
Realized Investment Gains (Losses)	0	0	0	0
Income tax penalties and interest expense	$ 0	$ 0	$ 0	$ 0
Number of operating segments | segment			1
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives			3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives			5 years

Cost Restructuring Plan - Narra

Cost Restructuring Plan - Narrative (Details) $ in Thousands	Aug. 07, 2019position	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)
Restructuring and Related Activities [Abstract]
Expected position eliminations | position	26
Expected costs remaining		$ 400		$ 400
Restructuring Cost and Reserve [Line Items]
Initial restructuring costs expected		1,500		1,500
Restructuring charges		1,092	$ 0	1,092	$ 0
Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring charges		900		900
General and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring charges		200		200
Retention
Restructuring Cost and Reserve [Line Items]
Initial restructuring costs expected		1,000		1,000
Restructuring charges		787	0	787	0
Severance
Restructuring Cost and Reserve [Line Items]
Initial restructuring costs expected		300		300
Restructuring charges		288	0	288	0
Other
Restructuring Cost and Reserve [Line Items]
Initial restructuring costs expected		200		200
Restructuring charges		$ 17	$ 0	$ 17	$ 0

Cost Restructuring Plan - Sched

Cost Restructuring Plan - Schedule of Restructuring Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 1,092	$ 0	$ 1,092	$ 0
Retention
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	787	0	787	0
Severance
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	288	0	288	0
Other
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 17	$ 0	$ 17	$ 0

Cost Restructuring Plan - Rollf

Cost Restructuring Plan - Rollforward of Restructuring Reserve (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Reserve [Roll Forward]
Beginning balance			$ 0
Additions	$ 1,092	$ 0	1,092	$ 0
Cash Payments			(288)
Adjustments			0
Ending balance	804		804
Retention
Restructuring Reserve [Roll Forward]
Beginning balance			0
Additions	787	0	787	0
Cash Payments			0
Adjustments			0
Ending balance	787		787
Severance
Restructuring Reserve [Roll Forward]
Beginning balance			0
Additions	288	0	288	0
Cash Payments			(288)
Adjustments			0
Ending balance	0		0
Other
Restructuring Reserve [Roll Forward]
Beginning balance			0
Additions	17	$ 0	17	$ 0
Cash Payments			0
Adjustments			0
Ending balance	$ 17		$ 17

Strategic Alliance and Collab_3

Strategic Alliance and Collaboration with Servier - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		17 Months Ended
	Feb. 28, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 695,000	$ 944,000	$ 3,581,000	$ 7,910,000
Amounts incurred but not yet billed		600,000		600,000		$ 600,000		$ 500,000
Accounts receivable		979,000		979,000		979,000		24,000
Servier Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum reimbursements of development costs							$ 3,100,000
Incremental increase in amount	$ 1,000,000
Development and regulatory milestones							$ 60,400,000
Servier
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable		971,000		971,000		971,000		$ 0
Milestone payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 0	$ 0	$ 0	$ 3,690,000
Milestone payments | Servier Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue						$ 7,500,000

Strategic Alliance and Collab_4

Strategic Alliance and Collaboration with Servier - Collaboration Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 695	$ 944	$ 3,581	$ 7,910
Milestone payments
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	3,690
Research and development reimbursable costs
Disaggregation of Revenue [Line Items]
Total revenue	625	814	3,471	3,248
Collaboration revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 625	$ 814	$ 3,471	$ 6,938

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,887	$ 3,817
Less: accumulated depreciation and amortization	(3,291)	(3,090)
Property and equipment, net	596	727
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,519	2,489
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	741	741
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment	461	428
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	$ 166	$ 159

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 100	$ 100	$ 215	$ 206

Accrued Liabilities - Component

Accrued Liabilities - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued outsourced clinical trials and preclinical studies	$ 2,607	$ 1,129
Restructuring liability	804	0
Accrued employee compensation and related taxes	652	1,704
Accrued other professional service fees	263	246
Accrued legal fees and expenses	258	376
Deferred and accrued facility lease obligations	88	124
Value of liability-classified stock purchase warrants	82	82
Accrued equipment and lab materials	0	33
Other accrued liabilities	103	174
Total accrued liabilities	$ 4,857	$ 3,868

Notes Payable - Narrative (Deta

Notes Payable - Narrative (Details) - 2017 SVB Loan Agreement - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Nov. 30, 2017
Debt Instrument [Line Items]
Interest margin in event of default	5.00%
Notes Payable to Banks
Debt Instrument [Line Items]
Face amount			$ 10
Repayment period	30 months
Interest-only period	18 months
Interest rate at period end	5.00%	5.50%
Final payment fee	$ 0.9

Notes Payable - Composition of

Notes Payable - Composition of Notes Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Principal amount outstanding	$ 8,667	$ 10,000
Unamortized debt discount	(39)	(69)
Accreted final payment fee	603	367
Total note payable	9,231	10,298
Less: current maturities	(3,972)	(2,294)
Note payable, net of current portion	$ 5,259	$ 8,004

Notes Payable - Future Annual M

Notes Payable - Future Annual Minimum Principal Payments (Details) $ in Thousands	Sep. 30, 2019USD ($)
Debt Disclosure [Abstract]
2019	$ 1,000
2020	4,000
2021	3,667
Total	$ 8,667

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) € in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		60 Months Ended	108 Months Ended
	Oct. 31, 2010EUR (€)	Oct. 31, 2010USD ($)	Sep. 30, 2019USD ($)arrangement	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)arrangementrenewal_term	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)arrangement	Sep. 30, 2019USD ($)arrangement
Commitments and Contingencies [Line Items]
License fee expense			$ 0	$ 0	$ 100,000	$ 700,000
Number of renewal terms | renewal_term					2
Renewal term			3 years		3 years		3 years	3 years
Rent expense			$ 100,000	100,000	$ 200,000	300,000
Operating expenses of leases			$ 100,000	100,000	$ 300,000	200,000
Yale University
Commitments and Contingencies [Line Items]
Term of agreement					5 years
Proceeds from collaboration							$ 900,000
University of Texas
Commitments and Contingencies [Line Items]
Number of arrangements | arrangement			1		1		1	1
Nonrefundable upfront license documentation fee					$ 10,000
Annual license maintenance fee					10,000
Potential milestone payment for initiation of defined clinical trials			$ 600,000		600,000		$ 600,000	$ 600,000
License fee expense			0	0	0	100,000
University of Texas | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			2,000,000		2,000,000		2,000,000	2,000,000
University of Texas | Other Regions
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			500,000		500,000		500,000	500,000
RICC
Commitments and Contingencies [Line Items]
Potential future milestone payments per licensed product			5,200,000		5,200,000		5,200,000	5,200,000
Payments for raw materials			0	$ 0	0	$ 300,000
t2cure
Commitments and Contingencies [Line Items]
Nonrefundable upfront license documentation fee		$ 46,000
Annual license maintenance fee	€ 3							3,000
Potential milestone payment for initiation of defined clinical trials			700,000		$ 700,000		700,000	700,000
Term of agreement					10 years
Period to terminate agreement					60 days
t2cure | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			2,500,000		$ 2,500,000		2,500,000	2,500,000
t2cure | European Union or Japan
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			$ 1,500,000		1,500,000		$ 1,500,000	$ 1,500,000
BWH
Commitments and Contingencies [Line Items]
Potential milestone payments					2,600,000
One-time sales milestone payment					$ 300,000

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Rental Payments (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 102
2020	277
Total	$ 379

Capital Stock - Narrative (Deta

Capital Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 31, 2019	Mar. 31, 2017	Aug. 31, 2018	Feb. 28, 2018	Mar. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Shares authorized (in shares)						105,000,000		105,000,000
Common stock, shares authorized (in shares)						100,000,000		100,000,000	100,000,000
Preferred stock, shares authorized (in shares)						5,000,000		5,000,000
Common stock, par value (in dollars per share)						$ 0.01		$ 0.01	$ 0.01
Preferred stock, par value (in usd per share)						$ 0.01		$ 0.01
Underwriter Option
Class of Stock [Line Items]
Shares sold (in shares)				7,414,996
Proceeds from the sale of common stock				$ 37,900
Underwriting Agreement
Class of Stock [Line Items]
Sale price (in usd per share)				$ 5.50
ATM Agreement
Class of Stock [Line Items]
Proceeds from the sale of common stock						$ 426	$ 2,747
Commission fee percent		3.00%
LLS Stock Purchase Agreement
Class of Stock [Line Items]
Transaction value			$ 5,000
Shares sold (in shares)			150,987
Sale price (in usd per share)			$ 6.62
LLS Stock Purchase Agreement | Subsequent Event
Class of Stock [Line Items]
Shares sold (in shares)	606,364
Sale price (in usd per share)	$ 0.82
Aggregate offering	$ 1,400
Maximum | ATM Agreement
Class of Stock [Line Items]
Aggregate offering					$ 50,000
Common Stock
Class of Stock [Line Items]
Shares sold (in shares)								1,357,627
Proceeds from the sale of common stock								$ 10,600
Weighted-average share price (in usd per share)								$ 8.13
Common Stock | ATM Agreement
Class of Stock [Line Items]
Shares sold (in shares)						144,241
Proceeds from the sale of common stock						$ 400
Weighted-average share price (in usd per share)						$ 2.95

Warrants - Narrative (Details)

Warrants - Narrative (Details) - Common Stock Warrants - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	46,522
Warrant exercise price (in usd per share)	$ 17.93	$ 27.65

Warrants - Stock Warrants Outst

Warrants - Stock Warrants Outstanding (Details) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Common Stock Warrants
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	46,522
Exercise price (in usd per share)	$ 17.93	$ 27.65
Expiration Date 2020
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	10,707
Exercise price (in usd per share)	$ 52.50
Expiration Date 2025
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	11,718
Exercise price (in usd per share)	$ 8.53
Expiration Date 2024
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	24,097
Exercise price (in usd per share)	$ 7.15

Warrants - Stock Warrant Activi

Warrants - Stock Warrant Activity (Details) - Warrants to purchase Common Stock	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Number
Beginning balance (in shares) | shares	49,349
Expiries (in shares) | shares	(2,827)
Ending balance (in shares) | shares	46,522
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 27.65
Expiries (in usd per share) | $ / shares	187.50
Ending balance (in usd per share) | $ / shares	$ 17.93

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2019	Jan. 01, 2018	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance (in shares)			4,182,404				4,182,404		4,182,404
Expiration period							10 years
Percent of common stock authorized under plan							4.00%
Additional shares authorized for plan (in shares)	1,233,578	902,720
Outstanding, exercisable equity awards			2,574,463				2,574,463		2,574,463
Remaining equity awards available for future issuances			1,290,930				1,290,930		1,290,930
Unrecognized employee stock-based compensation costs			$ 6.4				$ 6.4		$ 6.4
Remaining weighted-average period for RSUs							2 years 2 months 30 days
Options to purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)			4,034,000				4,034,000		4,034,000	3,527,000
Expiration period							10 years
Weighted average fair value per option (in usd per share)			$ 2.31		$ 2.31		$ 5.51	$ 5.51
Shares issued in period (in shares)							1,078,000
Options to purchase Common Stock | Initial vesting period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent							25.00%
Options to purchase Common Stock | Subsequent vesting period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent							75.00%
Vesting period							36 months
Options to purchase Common Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							48 months
Non-employee Stock Option | Non-employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period (in shares)			0		0		0	0
2008 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)			1,459,885				1,459,885		1,459,885
2016 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Basis for equity incentive plan (in shares)			1,681,294				1,681,294		1,681,294
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuance under ESPP (in shares)			622,347				622,347		622,347
Issuance of common stock for cash under employee stock purchase plan (in shares)			22,086	34,167	28,504	23,940			121,890

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - Options to purchase Common Stock shares in Thousands	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Number of Options (in thousands)
Beginning balance (in shares) | shares	3,527
Granted (in shares) | shares	1,078
Exercised (in shares) | shares	(142)
Forfeited or Expired (in shares) | shares	(429)
Ending balance (in shares) | shares	4,034
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 5.76
Granted (in usd per share) | $ / shares	2.89
Exercised (in usd per share) | $ / shares	0.60
Forfeited or expired (in usd per share) | $ / shares	5.49
Ending balance (in usd per share) | $ / shares	$ 5.20

Share-Based Compensation - Fair

Share-Based Compensation - Fair Value Assumption for Stock Options (Details) - Options to purchase Common Stock - $ / shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term, in years	6 years 4 months 5 days	6 years 3 months 29 days
Expected volatility	98.80%	84.90%
Risk-free interest rate	2.50%	2.60%
Expected dividend yield	0.00%	0.00%
Weighted-average exercise price (in usd per share)	$ 2.97	$ 7.48

Share-Based Compensation - Allo

Share-Based Compensation - Allocation of Share-based Compensation Expense on Statements of Operations (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 2,967	$ 2,742
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	1,175	933
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 1,792	$ 1,809

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potential Dilutive Securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	4,081	3,566
Options to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	4,034	3,517
Warrants to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	47	49