Viridian Therapeutics (VRDN) 10-Q 7 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	MIRAGEN THERAPEUTICS, INC.
Entity Central Index Key	1,590,750
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		30,839,463

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 31,700	$ 47,441
Short-term investments	38,827	0
Accounts receivable	1,382	1,456
Prepaid expenses and other current assets	3,843	2,971
Total current assets	75,752	51,868
Property and equipment, net	751	563
Other assets	50	50
Total assets	76,553	52,481
Current liabilities:
Accounts payable	1,206	906
Accrued liabilities	4,336	2,991
Current portion of note payable	1,291	0
Total current liabilities	6,833	3,897
Note payable, net of current portion	8,914	9,922
Other liabilities	88	152
Total liabilities	15,835	13,971
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 100,000,000 shares authorized; 30,833,367 and 22,568,006 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	308	226
Additional paid-in capital	176,395	131,877
Accumulated other comprehensive loss	(6)	0
Accumulated deficit	(115,979)	(93,593)
Total stockholders’ equity	60,718	38,510
Total liabilities and stockholders’ equity	$ 76,553	$ 52,481

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
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)	30,833,367	22,568,006
Common stock, shares outstanding (in shares)	30,833,367	22,568,006

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue	$ 944	$ 1,631	$ 7,910	$ 2,811
Operating expenses:
Research and development	7,399	5,018	22,187	14,625
General and administrative	2,696	2,502	8,354	8,364
Total operating expenses	10,095	7,520	30,541	22,989
Loss from operations	(9,151)	(5,889)	(22,631)	(20,178)
Other income (expense):
Interest and other income	362	113	890	245
Interest and other expense	(222)	(58)	(645)	(193)
Net loss	(9,011)	(5,834)	(22,386)	(20,126)
Change in unrealized loss on investments	(10)	0	(6)	0
Comprehensive loss	(9,021)	(5,834)	(22,392)	(20,126)
Accretion of redeemable convertible preferred stock to redemption value	0	0	0	(5)
Net loss available to common stockholders	$ (9,011)	$ (5,834)	$ (22,386)	$ (20,131)
Net loss per share, basic and diluted (in dollars per share)	$ (0.29)	$ (0.27)	$ (0.77)	$ (1.11)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	30,723,704	21,572,498	29,182,872	18,215,857
Collaboration revenue
Revenue:
Total revenue	$ 814	$ 1,493	$ 6,938	$ 1,991
Grant revenue
Revenue:
Total revenue	$ 130	$ 138	$ 972	$ 820

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated Other Comprehensive Loss	Accumulated deficit	Public Offering	Public OfferingCommon stock	Public OfferingAdditional paid-in capital	At-the-market Offering	At-the-market OfferingCommon stock	At-the-market OfferingAdditional paid-in capital	Private placement	Private placementCommon stock	Private placementAdditional paid-in capital
Beginning balance (in shares) at Dec. 31, 2017	22,568,006	22,568,006
Beginning balance at Dec. 31, 2017	$ 38,510	$ 226	$ 131,877	$ 0	$ (93,593)
Stockholders’ deficit
Issuance of common stock in public offering, net of issuance cost (in shares)							7,414,996			372,852			150,987
Issuance of common stock in public offering, net of issuance cost						$ 37,845	$ 74	$ 37,771	$ 2,657	$ 4	$ 2,653	$ 935	$ 2	$ 933
Shares issued for cash upon the exercise of stock options (in shares)		274,082
Shares issued for cash upon the exercise of stock options	179	$ 2	177
Issuance of common stock for cash under employee stock purchase plan (in shares)		52,444
Issuance of common stock for cash under employee stock purchase plan	242		242
Share-based compensation expense	2,742		2,742
Change in unrealized loss on investments	(6)			(6)
Net loss	$ (22,386)				(22,386)
Ending balance (in shares) at Sep. 30, 2018	30,833,367	30,833,367
Ending balance at Sep. 30, 2018	$ 60,718	$ 308	$ 176,395	$ (6)	$ (115,979)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (22,386)	$ (20,126)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	206	227
Share-based compensation expense	2,742	1,693
Non-cash interest expense	283	85
Amortization of premiums and discounts on available-for-sale securities	(229)	0
Changes in operating assets and liabilities:
Accounts receivable	74	(615)
Prepaid expenses and other assets	(927)	(719)
Accounts payable	287	(598)
Accrued and other liabilities	1,281	(871)
Net cash used in operating activities	(18,669)	(20,924)
Cash flows from investing activities:
Purchases of short-term investments	38,604	0
Purchases of property and equipment	(394)	(212)
Cash acquired in reverse merger	0	1,280
Net cash provided by (used in) investing activities	(38,998)	1,068
Cash flows from financing activities:
Proceeds from the exercise of stock options	179	220
Proceeds from stock purchases under employee stock purchase plan	242	110
Payments of principal on note payable	0	(1,500)
Net cash provided by financing activities	41,926	40,557
Net increase (decrease) in cash and cash equivalents	(15,741)	20,701
Cash and cash equivalents at beginning of period	47,441	22,104
Cash and cash equivalents at end of period	31,700	42,805
Supplemental disclosure of cash flow information
Cash paid for interest	358	112
Supplemental disclosure of non-cash investing and financing activities
Amortization of public offering costs	55	0
Unpaid common stock issuance costs included in current liabilities	13	3
Change in unrealized loss on investments	(6)	0
Conversion of preferred stock to common stock	0	76,981
Liabilities assumed, net of non-cash assets received in reverse merger	0	1,076
Reclassification of preferred stock warrant (accrued liability) to common stock warrant (equity)	0	51
Accretion of redeemable convertible preferred stock to redemption value	0	5
Public Offering
Cash flows from financing activities:
Proceeds from the sale of common stock	40,782	0
Payment of issuance costs associated with the sale of common stock	(2,890)	0
Private Financing
Cash flows from financing activities:
Proceeds from the sale of common stock	1,000	40,703
Payment of issuance costs associated with the sale of common stock	(52)	(1,216)
Supplemental disclosure of non-cash investing and financing activities
Transfer of common stock issuance costs from prepaid expenses and other current assets to equity (private financing and at the market sales)	0	339
Shelf Registration
Cash flows from financing activities:
Payment of issuance costs associated with the sale of common stock	$ 0	$ (299)

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2018
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 clinical-stage product candidates, cobomarsen, remlarsen, and MRG-110. The Company is developing MRG-110 under a license and collaboration agreement (the “Servier Collaboration Agreement”) with Les Laboratoires Servier and Institut de Recherches Servier (collectively, “Servier”). Liquidity The Company has incurred annual net operating losses since its inception. As of September 30, 2018 , the Company had an accumulated deficit of $116.0 million and a net loss of $9.0 million and $22.4 million for the three and nine months ended September 30, 2018 , respectively. The Company’s management believes that the $31.7 million of cash and cash equivalents and $38.8 million of short-term investments on hand at September 30, 2018 will be sufficient to fund its operations in the normal course of business and allow the Company to meet its liquidity needs into early 2020. The Company has funded its operations to date principally through proceeds from equity financings, including notes payable that previously converted to equity explained further in Note 9. Common Stock . The Company will continue to require additional capital beyond early 2020 to continue its clinical development and potential commercialization activities. 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, continued performance under the Servier Collaboration Agreement, securing additional partnerships and collaborations, and issuing debt or other financing vehicles. The Company’s ability to secure additional capital is dependent upon a number of 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.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
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 subsidiary, Miragen Therapeutics Europe Limited (“Miragen Europe”), which was formed in January 2011 for the sole purpose of submitting regulatory filings in Europe. Miragen Europe has 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, 2018, or for any other interim period, or for any other future year. The balance sheet as of December 31, 2017 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 unaudited 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, 2017, filed with the SEC on March 15, 2018. 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 revenues 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 The Company recognizes revenue principally from its strategic alliance and collaboration agreement. Revenue is recognized from upfront payments for licenses and milestone payments that are generated from defined research or development events, as well as from the reimbursement of amounts for research and development services under its strategic alliance and collaboration agreement. The Company recognizes revenue when all four of the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) products have been delivered or services rendered; (3) the selling price is fixed or determinable; and (4) collectability is reasonably assured. Multiple-element arrangements are examined to determine whether the deliverables can be separated or must be accounted for as a single unit of accounting. The Servier Collaboration Agreement, for example, includes a combination of upfront license fees, payments for research and development activities, and milestone payments that are evaluated to determine whether each deliverable under the agreement has value to the customer on a stand-alone basis and whether reliable evidence of fair value for the deliverable exists. Deliverables in an arrangement that do not meet this separation criteria are treated as a single unit of accounting, generally applying applicable revenue recognition guidance for the final deliverable to the combined unit of accounting. The Company recognizes revenue from non-refundable upfront license fees over the term of performance when combined with other deliverables. When the performance period is not specified, the Company estimates the performance period based upon provisions contained within the agreement, such as the duration of the research or development term, the existence, or likelihood, of achievement of development commitments, and any other significant commitments. These advance payments are deferred and recorded as deferred revenue upon receipt, pending recognition, and are classified as a short-term or long-term liability in the accompanying condensed consolidated balance sheets. Expected performance periods are reviewed periodically and, if applicable, the amortization period is adjusted, which may accelerate or decelerate revenue recognition. The timing of revenue recognition, specifically as it relates to the amortization of upfront license fees, is significantly influenced by the Company’s estimates. The Company applies the milestone method of accounting to recognize revenue from milestone payments when earned, as evidenced by persuasive evidence that the milestone has been achieved and the payment is non-refundable, provided that the milestone event is substantive. A milestone event is defined as an event (1) that can only be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance; (2) for which there is substantive uncertainty at the inception of the arrangement that the event will be achieved; and (3) that would result in additional payments being due to the Company. Events for which the occurrence is either contingent solely upon the passage of time or the result of a counterparty’s performance are not considered to be milestone events. A milestone event is substantive if all of the following conditions are met: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value to the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) the consideration relates solely to past performance; and (iii) the consideration is reasonable relative to all the deliverables and payment terms (including other potential milestone consideration) within the arrangement. The Company assesses whether a milestone is substantive at the inception of each arrangement. If a milestone is deemed non-substantive, the Company accounts for the milestone payment using a method consistent with the related units of accounting for the arrangement over the estimated performance period. 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. The Company accounts for stock options issued to non-employees (other than board members) by valuing the award using an option pricing model and remeasuring such awards to the current fair value until the awards are vested or a performance commitment has otherwise been reached. 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, costs of research and development activities conducted by third parties on the Company’s behalf, 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 goods or when the services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records upfront and milestone payments to acquire 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 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 each period end 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, 2018 , the Company’s short-term available-for-sale securities had an amortized cost of $38.8 million , fair value of $38.8 million , and a gross unrealized loss of $6 thousand . The Company had no long-term investments as of September 30, 2018 . The Company had no investments as of December 31, 2017. Fair Value of Financial Instruments 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, December 31, Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 32,539 $ — $ 47,653 $ — U.S. treasury securities (included in short-term investments) 38,827 — — — Total assets $ 71,366 $ — $ 47,653 $ — 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. 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, 2018 and 2017 . 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 anti-dilutive. 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 are reflected as a separate component in the statement of stockholders’ equity. As of September 30, 2018 , the Company had accumulated other comprehensive loss of $6 thousand . The Company had no accumulated other comprehensive income (loss) at December 31, 2017. The Company had no realized gain or loss during the three and nine months ended September 30, 2018 and 2017 . 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, 2018 and 2017 . The Tax Cuts and Jobs Act (“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 Company does not anticipate the Tax Act to 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 – Not Yet Adopted Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ( “ ASU”) No. 2014-09 , Revenue from Contracts with Customers (Accounting Standards Codification Topic 606) (“ASC 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 also will require enhanced revenue disclosures, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. This accounting standard becomes effective for the Company for reporting periods beginning after December 15, 2018, and interim reporting periods thereafter. Early adoption is permitted for annual reporting periods (including interim periods) beginning after December 15, 2016. This new standard permits the use of either the retrospective or cumulative effect transition method. The Company has elected to not early adopt ASC 606. The Company is assessing the impact of ASC 606 on its accounting policies and procedures and evaluating the new requirements as applied to existing revenue contracts. While this assessment is still in process, the Company does not believe the adoption of ASC 606 will have a material impact on its condensed consolidated financial statements because the Company has limited active contracts in effect. The Company also continues to evaluate the method of adoption and believes the selected implementation method will be dependent upon the contract or contracts that are in place at the transition date. In addition to the assessment of the impact of ASC 606, the Company is analyzing and updating its internal controls over financial reporting to ensure that information required to fulfill the new standard is properly secured and recorded. The Company will implement any changes as required by the adoption of ASC 606 beginning in the first quarter of 2019. 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. 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. This standard is effective for the Company in the first quarter of 2020, and early adoption is permitted. The Company expects the impact of the pending adoption of this standard will not have a significant impact on its condensed consolidated financial statements upon adoption. 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. Other new pronouncements issued but not effective as of September 30, 2018 are not expected to have a material impact on the Company’s condensed consolidated financial statements.

Strategic Alliance and Collabor

Strategic Alliance and Collaboration with Servier	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Strategic Alliance and Collaboration with Servier	STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER Collaboration revenue under the Servier Collaboration Agreement consisted of the following: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (in thousands) Collaboration revenue: Milestone payments $ — $ — $ 3,690 $ — Reimbursed payments 814 1,493 3,248 1,991 Total collaboration revenue $ 814 $ 1,493 $ 6,938 $ 1,991 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. In 2017, the Company and Servier agreed to amend the Servier Collaboration Agreement to remove all existing targets, add one new target (microRNA-92), and grant Servier the right to add one additional target through September 2019. In April 2018, the Company and Servier entered into a seventh amendment to the Servier Collaboration Agreement (the “Servier Amendment”). The Servier Amendment, among other things, (i) updated the development plan for MRG-110 and cost-sharing provisions; (ii) provided for specified development cost reimbursement by Servier to the Company following a determination by a joint committee established by the parties under the Servier Collaboration Agreement that the outcome of a specified portion of a Phase 1 clinical trial has met its primary end point; and (iii) provided for additional development plan cost reimbursement by Servier to the Company following a determination by a joint committee established by the parties under the Servier Collaboration Agreement that a product candidate targeting microRNA-92 will proceed into a Phase 2 clinical trial. Servier’s rights to each named target are limited to therapeutics in the field of cardiovascular disease, as defined, and in their territory, which is worldwide except for the United States and Japan. The Company retains 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. The Company is eligible to receive non-refundable development milestone payments of €5.8 million to €13.8 million ( $6.7 million to $16.0 million as of September 30, 2018 ) and regulatory milestone payments of €10.0 million to €40.0 million ( $11.6 million to $46.4 million as of September 30, 2018 ) for each target. Additionally, the Company may receive up to €175.0 million ( $203.0 million as of September 30, 2018 ) in commercialization milestones, as well as quarterly royalty payments expressed in percentages ranging from the low-double digits to the mid-teens (subject to reductions for patent expiration, generic competition, third-party royalty, and costs of goods) on the net sales of any licensed product commercialized by Servier. Servier is obligated to make royalty payments for a period specified under the Servier Collaboration Agreement. The Company applies the milestone method of accounting to recognize revenue from milestone payments when earned, as evidenced by persuasive evidence that the milestone has been achieved and the payment is non-refundable, provided that the milestone event is substantive. In March 2018, the Company and Servier initiated a Phase 1 clinical trial of MRG-110. As a result, under the terms of the Servier Collaboration Agreement, the Company earned and received its first development milestone payment of €3.0 million (or $3.7 million ). This amount is included as revenue in the accompanying condensed consolidated statements of operations and comprehensive loss during the nine months ended September 30, 2018 . As part of the Servier Collaboration Agreement, the Company established a multiple-year research collaboration, under which it jointly performs agreed upon research activities directed to the identification and characterization of named targets and oligonucleotides in the cardiovascular field, which is referred to as the Research Collaboration. The current amended term of the Research Collaboration extends through September 2019. Servier is responsible for funding certain costs of the Research Collaboration, as defined under the Servier Collaboration Agreement. The development of each product candidate (commencing with registration enabling toxicology studies) under the Servier Collaboration Agreement is performed pursuant to a mutually agreed upon development plan to be conducted by the parties as necessary to generate data useful for both parties to obtain regulatory approval of such product candidates. Servier is responsible for a specified percentage of the cost of research and development activities under the development plan through the completion of one or more Phase 2 clinical trials and will reimburse the Company for a specified portion of such costs it incurs. The costs of Phase 3 clinical trials for each product candidate will be allocated between the parties at a specified percentage of costs. The applicable percentage for each product candidate will be based upon whether certain events under the Servier Collaboration Agreement occur, including if the Company enters into a third-party agreement for the development and/or commercialization of a product in the United States at least 180 days before the initiation of the first Phase 3 clinical trial, or if the Company subsequently enters into a U.S. partner agreement, or if it does not enter into a U.S. partner agreement but files for approval in the United States using data from the Phase 3 clinical trial. Under the Servier Collaboration Agreement, the Company also granted Servier a royalty-free, non-exclusive license to develop a companion diagnostic in its territory for any therapeutic product that may be developed by Servier under the Servier Collaboration Agreement. The Company also granted Servier an exclusive, royalty-free license to commercialize such a companion diagnostic in its territory for use in connection with the development and commercialization of such therapeutic product in its territory. The Servier Collaboration Agreement will expire as to each underlying product candidate when Servier’s royalty obligations as to such product candidate have expired. Servier may also terminate the Servier Collaboration Agreement for: (i) convenience upon a specified number of days’ prior notice to the Company or (ii) upon determination of a safety issue relating to development under the agreement upon a specified number of days’ prior notice to the Company. Either party may terminate the Servier Collaboration Agreement upon a material breach by the other party that is not cured within a specified number of days. The Company may also terminate the agreement if Servier challenges any of the patents licensed by the Company to Servier. The Company determined that the elements within the Servier Collaboration Agreement should be treated as a single unit of accounting because the delivered elements, the licenses, did not have stand-alone value to Servier at the time the license was granted. As such, the Company recognized license fees earned under the Servier Collaboration Agreement as revenue on a proportional performance basis over the estimated period to complete the activities under the Research Collaboration. The total period of performance is equal to the estimated term of the Research Collaboration. The Company measured its progress under the proportional performance method based on actual and estimated full-time equivalents. The Company received a total of $12.4 million ( €9.0 million ) in non-refundable license fees under the Servier Collaboration Agreement. Based on earlier estimates of the term of the Research Collaboration, these license fees had been fully recognized as revenue during the period from October 2011 through December 2016. Accordingly, no amounts were recognized as license revenue during the three and nine months ended September 30, 2018 and 2017 , respectively. Amounts incurred but not billed to Servier for research and related intellectual property activities totaled $0.8 million and $1.1 million as of September 30, 2018 and December 31, 2017 , respectively. These amounts are included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheets. As of September 30, 2018 and December 31, 2017 , accounts receivable for Servier research and related intellectual property activities totaled $1.4 million .

Reverse Merger

Reverse Merger	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Reverse Merger	REVERSE MERGER In February 2017, the Company, then known as Signal Genetics, Inc. (“Signal”), completed its merger with Miragen Therapeutics, Inc., a then privately-held Delaware corporation (“Private Miragen”). Pursuant to the Agreement and Plan of Merger and Reorganization (the “Merger Agreement”) by and among the Company, Private Miragen, and Signal Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”), Merger Sub merged with and into Private Miragen, with Private Miragen surviving as a wholly-owned subsidiary of the Company (the “Merger”). Immediately, following the Merger, Private Miragen merged with and into the Company, with the Company as the surviving corporation (the “Short-Form Merger” and, together with the Merger, the “Mergers”). In connection with the Short-Form Merger, the Company changed its corporate name to “Miragen Therapeutics, Inc.” For accounting purposes, Private Miragen is considered to have acquired Signal in the Merger. Private Miragen was determined to be the accounting acquirer based upon the terms of the Merger and other factors including: (i) the Private Miragen security holders owned approximately 95.2% of the combined company’s outstanding common stock immediately following the closing of the Mergers; (ii) former Private Miragen directors held all of the board seats in the combined company immediately following the closing of the Mergers; and (iii) Private Miragen management held key management positions of the combined company. The Merger has been accounted for as an asset acquisition rather than business combination because the assets acquired and liabilities assumed by Private Miragen do not meet the definition of a business as defined by U.S. GAAP. The net assets acquired in connection with this transaction were recorded at their estimated acquisition date fair values in February 2017 as of the date the Mergers were completed. Immediately prior to the effective date of the Merger, all shares of preferred stock of Private Miragen converted into shares of common stock of Private Miragen on a one -for-one basis. At the effective date of the Merger, the Company issued shares of its Common Stock to Private Miragen stockholders, at an exchange rate of approximately 0.7031 shares of Common Stock in exchange for each share of Private Miragen common stock outstanding immediately prior to the Merger. The exchange rate was calculated by a formula that was determined through arms-length negotiations between the Company and Private Miragen. The combined company assumed all the outstanding options, whether or not vested, under the 2008 Plan with such options representing the right to purchase a number of shares of Common Stock equal to approximately 0.7031 multiplied by the number of shares of Private Miragen common stock previously represented by such options. Immediately after the Merger, there were 21,309,440 shares of Common Stock outstanding. In addition, immediately after the Merger, Private Miragen stockholders, warrant holders, and option holders owned approximately 95.9% of the aggregate number of shares of Common Stock, and the stockholders of the Company immediately prior to the Merger owned approximately 4.1% of the aggregate number of shares of Common Stock (each on a fully diluted basis). The accompanying unaudited condensed consolidated financial statements and notes to the unaudited condensed consolidated financial statements give retroactive effect to the exchange ratio and change in par value for all periods presented. On February 13, 2017, prior to the effectiveness of the Merger, Signal had 1,024,960 shares of Common Stock outstanding and a market capitalization of $12.6 million . The estimated fair value of the net assets of Signal on February 13, 2017, prior to the Merger, was $0.2 million . The fair value of Common Stock on the Merger closing date, prior to the Merger, was above the fair value of the Company’s net assets. As the Company’s net assets were predominantly comprised of cash offset by current liabilities, the fair value of the Company’s net assets as of February 13, 2017, prior to the Merger, is considered to be the best indicator of the fair value and, therefore, the purchase consideration. The following table summarizes the net assets acquired based on their estimated fair values immediately prior to the Merger (in thousands): Cash and cash equivalents $ 1,280 Prepaid and other assets 248 Accrued liabilities (1,324 ) Net acquired tangible assets $ 204

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2018
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 $ 2,490 $ 2,229 Leasehold improvements 741 737 Computer hardware and software 409 355 Furniture and fixtures 126 77 Property and equipment, gross 3,766 3,398 Less: accumulated depreciation and amortization (3,015 ) (2,835 ) Property and equipment, net $ 751 $ 563 During the three months ended September 30, 2018 and 2017 , depreciation and amortization expense was $0.1 million . During the nine months ended September 30, 2018 and 2017 , 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, 2018
Payables and Accruals [Abstract]
Accrued Liabilities	ACCRUED LIABILITIES Accrued liabilities consisted of the following: September 30, December 31, (in thousands) Accrued outsourced clinical trial and preclinical studies $ 2,005 $ 581 Accrued employee compensation and related taxes 1,259 1,538 Accrued legal fees and expenses 358 185 Accrued equipment and lab materials 284 197 Accrued other professional service fees 101 232 Deferred and accrued facility lease obligations 83 74 Value of liability-classified stock purchase warrants 82 82 Other accrued liabilities 164 102 Total accrued liabilities $ 4,336 $ 2,991

Notes Payable

Notes Payable	9 Months Ended
	Sep. 30, 2018
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”), which amended and restated the loan and security agreement Private Miragen entered into with Silicon Valley Bank in April 2015 (the “2015 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. Under certain circumstances, the interest-only period can be extended by an additional six months. Amounts outstanding bear interest at the prime rate ( 5.25% at September 30, 2018 ), with a final payment fee equal to $0.9 million due upon maturity. As of September 30, 2018 , 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. 2015 Silicon Valley Bank Loan Agreement In April 2015, Private Miragen entered into the 2015 SVB Loan Agreement and $5.0 million was funded in May 2015, which had a 30 -month payment period following an 18 -month interest-only payment period that ended in November 2016. Interest accrued on amounts outstanding at the prime rate minus 0.25% , with a final payment fee equal to 5.50% of amounts borrowed. Upon the execution of the 2017 SVB Loan Agreement, the 2015 SVB Loan agreement was terminated in its entirety. As a result, the Company paid the remaining principal and final interest payment with proceeds from the 2017 SVB Loan Agreement. The Company accounted for the termination of the 2015 SVB Loan Agreement as an extinguishment and incurred a loss on debt extinguishment of $0.1 million , which was recorded within interest expense. Amounts outstanding under the SVB loan agreements were as follows: September 30, December 31, (in thousands) Principal amount outstanding $ 10,000 $ 10,000 Unamortized debt discount (80 ) (119 ) Accreted final payment fee 285 41 Total note payable 10,205 9,922 Less: current maturities (1,291 ) — Long-term note payable, net of current portion $ 8,914 $ 9,922 Future annual minimum principal payments under the 2017 SVB Loan Agreement as of September 30, 2018 for the respective calendar years are as follows (in thousands): 2018 $ — 2019 2,333 2020 4,000 2021 3,667 Total $ 10,000

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
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 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 executives at any time, with or without cause. If an executive is terminated without cause, as defined in the employment agreements, or an executive resigns for good reason, as defined in the employment agreements, then 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) acceleration of vesting of the equivalent of 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) 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 Agreements with the University of Texas As of September 30, 2018 , the Company had two exclusive patent license agreements (the “UT License Agreements”) with the Board of Regents of The University of Texas System (the “University of Texas”). Under each of the UT License Agreements, the University of Texas granted the Company exclusive and nonexclusive licenses to certain patent and technology rights. The University of Texas is 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 upfront 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 nine months ended September 30, 2018 and 2017 , the Company incurred immaterial upfront 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 Agreements, 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 Agreements, 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. During the nine months ended September 30, 2018 , the Company made an immaterial milestone payment, which was recorded as research and development expense. Prior to September 30, 2018 , the Company did not incur any milestone payments. 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 Agreements 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 Agreements 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 Agreements 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) In June 2010, Private Miragen entered into a license agreement with the Santaris Pharma A/S, which was subsequently acquired by F. Hoffmann-La Roche Ltd (“Roche”) in 2014, and subsequently changed its name to Roche Innovation Center Copenhagen A/S (“RICC”). The agreement was amended in October 2011 and amended and restated in December 2012 (the “RICC License Agreement”). 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 for 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 during the term of 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 upfront and 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, 2018 , the Company incurred $0.7 million in 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. 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 nine months ended September 30, 2018 and 2017 , the Company paid $0.3 million and $0.5 million , respectively, to RICC for raw materials to be used in its drug manufacturing process. Subcontract Agreement with Yale University In October 2014, Private Miragen and Yale University (“Yale”) entered into a subcontract agreement and then into a subaward agreement in March 2015 (the “Yale Agreements”), which were subsequently amended. Under the Yale Agreements, the Company is providing specified services regarding the development of a proprietary compound that targets miR-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 miR-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 certain 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, 2018 , the Company received $0.8 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 In October 2010, Private Miragen entered into a license and collaboration agreement (the “t2cure Agreement”) 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 miR-92. In consideration of rights granted by t2cure, Private Miragen paid an upfront fee of $46 thousand and agreed to: (i) pay an annual license maintenance fee in the amount of €3 thousand ( $3 thousand as of September 30, 2018 ); 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 certain circumstances, sublicense fees equal to a percentage 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. The Company has expensed all charges incurred under the t2cure Agreement to date, due to the uncertainty as to future economic benefit from the acquired rights. License Agreement with The Brigham and Women’s Hospital In May 2016, Private Miragen and The Brigham and Women’s Hospital (“BWH”) entered into an exclusive patent license agreement (the “BWH License Agreement”). Under the BWH License Agreement, the Company has 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. Facility Lease In December 2010, Private Miragen entered into a multi-year lease agreement for its current office and lab space. The agreement was subsequently amended to extend the term through August 2020. This lease is noncancelable. 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 three months ended September 30, 2018 and 2017 , rent expense was $0.1 million . The Company is also required to pay for operating expenses related to the leased space, which were $0.1 million for the three months ended September 30, 2018 and 2017 . During the nine months ended September 30, 2018 and 2017 , rent expense was $0.3 million and $0.2 million , respectively. Operating expenses were $0.2 million for the nine months ended September 30, 2018 and 2017 . Future annual minimum payments under the lease as of September 30, 2018 for the respective calendar year were as follows (in thousands): 2018 $ 99 2019 404 2020 277 Total $ 780

Capital Stock

Capital Stock	9 Months Ended
	Sep. 30, 2018
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”) for the sale of up to $5.0 million of shares of Common Stock to LLS 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 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 , which resulted in net proceeds of approximately $0.9 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, 2018 , the Company sold, pursuant to the terms of the ATM Agreement, 372,852 shares of Common Stock, at a weighted average price of $7.37 per share, for aggregate net proceeds of approximately $2.7 million , including commissions to Cowen as sales agent. Through September 30, 2018 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 1,213,386 shares of Common Stock, at a weighted average price of $8.74 per share, for aggregate net proceeds of approximately $10.2 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 (the “Underwriting Agreement”) with underwriters relating to a public offering of its Common Stock. Under the Underwriting Agreement, in February 2018, 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. Private Miragen Common Stock Offering In February 2017, immediately prior to the Merger and in accordance with subscription agreements entered into with certain investors in October 2016, Private Miragen issued and sold an aggregate of 9,045,126 shares of Private Miragen’s common stock at a price per share of $4.50 , or 6,359,628 shares of Common Stock at a price per share of $6.40 as adjusted for the exchange ratio in the Merger, which resulted in net proceeds of approximately $39.2 million , after giving effect to associated financing fees of $1.5 million . Series Preferred As of September 30, 2018 , the Company had no shares of preferred stock outstanding and had not designated the rights, preferences, or privileges of any class or series of preferred stock. The Company’s board of directors has the authority to issue preferred stock at its discretion in one or more classes or series and to fix the designations, powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, and the number of shares constituting any class or series of preferred stock, without further vote or action by the stockholders. WARRANTS As of September 30, 2018 , the Company had 49,349 Common Stock Warrants outstanding at a weighted average exercise price of $27.65 . A summary of outstanding Common Stock purchase warrants as of September 30, 2018 is as follows: Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 24,097 $7.15 2024 49,349 The Company had no stock purchase warrant activity during the nine months ended September 30, 2018 .

Warrants

Warrants	9 Months Ended
	Sep. 30, 2018
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”) for the sale of up to $5.0 million of shares of Common Stock to LLS 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 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 , which resulted in net proceeds of approximately $0.9 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, 2018 , the Company sold, pursuant to the terms of the ATM Agreement, 372,852 shares of Common Stock, at a weighted average price of $7.37 per share, for aggregate net proceeds of approximately $2.7 million , including commissions to Cowen as sales agent. Through September 30, 2018 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 1,213,386 shares of Common Stock, at a weighted average price of $8.74 per share, for aggregate net proceeds of approximately $10.2 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 (the “Underwriting Agreement”) with underwriters relating to a public offering of its Common Stock. Under the Underwriting Agreement, in February 2018, 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. Private Miragen Common Stock Offering In February 2017, immediately prior to the Merger and in accordance with subscription agreements entered into with certain investors in October 2016, Private Miragen issued and sold an aggregate of 9,045,126 shares of Private Miragen’s common stock at a price per share of $4.50 , or 6,359,628 shares of Common Stock at a price per share of $6.40 as adjusted for the exchange ratio in the Merger, which resulted in net proceeds of approximately $39.2 million , after giving effect to associated financing fees of $1.5 million . Series Preferred As of September 30, 2018 , the Company had no shares of preferred stock outstanding and had not designated the rights, preferences, or privileges of any class or series of preferred stock. The Company’s board of directors has the authority to issue preferred stock at its discretion in one or more classes or series and to fix the designations, powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, and the number of shares constituting any class or series of preferred stock, without further vote or action by the stockholders. WARRANTS As of September 30, 2018 , the Company had 49,349 Common Stock Warrants outstanding at a weighted average exercise price of $27.65 . A summary of outstanding Common Stock purchase warrants as of September 30, 2018 is as follows: Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 24,097 $7.15 2024 49,349 The Company had no stock purchase warrant activity during the nine months ended September 30, 2018 .

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION Equity Incentive Plans As of September 30, 2018 , there were 1,645,892 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 the closing date of the Merger, 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) 902,720 shares from previous automatic increases to the share reserve (as described in more detail below), including the automatic increase of 902,720 shares effected on January 1, 2018. In addition, 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. As of September 30, 2018 , there were equity awards exercisable for 1,840,317 shares of Common Stock outstanding and 722,269 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, 2017 2,863 $ 4.85 Granted 1,069 $ 7.48 Exercised (274 ) $ 0.66 Forfeited or canceled (141 ) $ 9.80 Outstanding at September 30, 2018 3,517 $ 5.78 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. Prior to the Merger, Private Miragen estimated the fair value of underlying shares of its common stock using a third-party valuation report that derived the fair value using the probability-weighted expected return method. After the Merger, 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 The weighted-average grant-date fair value of options granted during the nine months ended September 30, 2018 and 2017 was $5.51 and $8.32 , respectively. The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Nine Months Ended 2018 2017 Expected term, in years 6.33 6.44 Expected volatility 84.9 % 83.8 % Risk-free interest rate 2.6 % 2.1 % Expected dividend yield — % — % Weighted-average exercise price $ 7.48 $ 11.48 Stock Options Granted to Non-Employees The Company determines the value of Common Stock options issued to non-employees using the Black-Scholes option pricing model and adjusting the value of such awards to current fair value each reporting period until the awards are vested or a performance commitment has otherwise been reached. No Common Stock options were issued to non-employees during the nine months ended September 30, 2018 and 2017 . Employee Stock Purchase Plan The 2016 Employee Stock Purchase Plan (“ESPP”) allows qualified employees to purchase shares of the Company's 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, 2018 , the Company had 0.4 million shares available for issuance and 66 thousand 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 2018 2017 (in thousands) Research and development $ 933 $ 643 General and administrative 1,809 1,050 Total share-based compensation expense $ 2,742 $ 1,693 As of September 30, 2018 , the Company had $9.3 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 2.8 years.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2018
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, 2018 2017 (in thousands) Options to purchase Common Stock 3,517 2,969 Warrants to purchase Common Stock 49 25 Total 3,566 2,994

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
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 subsidiary, Miragen Therapeutics Europe Limited (“Miragen Europe”), which was formed in January 2011 for the sole purpose of submitting regulatory filings in Europe. Miragen Europe has 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, 2018, or for any other interim period, or for any other future year. The balance sheet as of December 31, 2017 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 unaudited 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, 2017, filed with the SEC on March 15, 2018. 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 revenues 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 The Company recognizes revenue principally from its strategic alliance and collaboration agreement. Revenue is recognized from upfront payments for licenses and milestone payments that are generated from defined research or development events, as well as from the reimbursement of amounts for research and development services under its strategic alliance and collaboration agreement. The Company recognizes revenue when all four of the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) products have been delivered or services rendered; (3) the selling price is fixed or determinable; and (4) collectability is reasonably assured. Multiple-element arrangements are examined to determine whether the deliverables can be separated or must be accounted for as a single unit of accounting. The Servier Collaboration Agreement, for example, includes a combination of upfront license fees, payments for research and development activities, and milestone payments that are evaluated to determine whether each deliverable under the agreement has value to the customer on a stand-alone basis and whether reliable evidence of fair value for the deliverable exists. Deliverables in an arrangement that do not meet this separation criteria are treated as a single unit of accounting, generally applying applicable revenue recognition guidance for the final deliverable to the combined unit of accounting. The Company recognizes revenue from non-refundable upfront license fees over the term of performance when combined with other deliverables. When the performance period is not specified, the Company estimates the performance period based upon provisions contained within the agreement, such as the duration of the research or development term, the existence, or likelihood, of achievement of development commitments, and any other significant commitments. These advance payments are deferred and recorded as deferred revenue upon receipt, pending recognition, and are classified as a short-term or long-term liability in the accompanying condensed consolidated balance sheets. Expected performance periods are reviewed periodically and, if applicable, the amortization period is adjusted, which may accelerate or decelerate revenue recognition. The timing of revenue recognition, specifically as it relates to the amortization of upfront license fees, is significantly influenced by the Company’s estimates. The Company applies the milestone method of accounting to recognize revenue from milestone payments when earned, as evidenced by persuasive evidence that the milestone has been achieved and the payment is non-refundable, provided that the milestone event is substantive. A milestone event is defined as an event (1) that can only be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance; (2) for which there is substantive uncertainty at the inception of the arrangement that the event will be achieved; and (3) that would result in additional payments being due to the Company. Events for which the occurrence is either contingent solely upon the passage of time or the result of a counterparty’s performance are not considered to be milestone events. A milestone event is substantive if all of the following conditions are met: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value to the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) the consideration relates solely to past performance; and (iii) the consideration is reasonable relative to all the deliverables and payment terms (including other potential milestone consideration) within the arrangement. The Company assesses whether a milestone is substantive at the inception of each arrangement. If a milestone is deemed non-substantive, the Company accounts for the milestone payment using a method consistent with the related units of accounting for the arrangement over the estimated performance period.
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. The Company accounts for stock options issued to non-employees (other than board members) by valuing the award using an option pricing model and remeasuring such awards to the current fair value until the awards are vested or a performance commitment has otherwise been reached.
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, costs of research and development activities conducted by third parties on the Company’s behalf, 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 goods or when the services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records upfront and milestone payments to acquire 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 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 each period end 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 of Financial Instruments	Fair Value of Financial Instruments 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. 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	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 anti-dilutive.
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 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, 2018 and 2017 . The Tax Cuts and Jobs Act (“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 Company does not anticipate the Tax Act to 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 - Not Yet Adopted	Recent Accounting Pronouncements – Not Yet Adopted Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ( “ ASU”) No. 2014-09 , Revenue from Contracts with Customers (Accounting Standards Codification Topic 606) (“ASC 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 also will require enhanced revenue disclosures, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. This accounting standard becomes effective for the Company for reporting periods beginning after December 15, 2018, and interim reporting periods thereafter. Early adoption is permitted for annual reporting periods (including interim periods) beginning after December 15, 2016. This new standard permits the use of either the retrospective or cumulative effect transition method. The Company has elected to not early adopt ASC 606. The Company is assessing the impact of ASC 606 on its accounting policies and procedures and evaluating the new requirements as applied to existing revenue contracts. While this assessment is still in process, the Company does not believe the adoption of ASC 606 will have a material impact on its condensed consolidated financial statements because the Company has limited active contracts in effect. The Company also continues to evaluate the method of adoption and believes the selected implementation method will be dependent upon the contract or contracts that are in place at the transition date. In addition to the assessment of the impact of ASC 606, the Company is analyzing and updating its internal controls over financial reporting to ensure that information required to fulfill the new standard is properly secured and recorded. The Company will implement any changes as required by the adoption of ASC 606 beginning in the first quarter of 2019. 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. 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. This standard is effective for the Company in the first quarter of 2020, and early adoption is permitted. The Company expects the impact of the pending adoption of this standard will not have a significant impact on its condensed consolidated financial statements upon adoption. 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. Other new pronouncements issued but not effective as of September 30, 2018 are not expected to have a material impact on the Company’s condensed consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
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, December 31, Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 32,539 $ — $ 47,653 $ — U.S. treasury securities (included in short-term investments) 38,827 — — — Total assets $ 71,366 $ — $ 47,653 $ — 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, December 31, Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) (1) $ 32,539 $ — $ 47,653 $ — U.S. treasury securities (included in short-term investments) 38,827 — — — Total assets $ 71,366 $ — $ 47,653 $ — 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.

Strategic Alliance and Collab_2

Strategic Alliance and Collaboration with Servier (Tables)	9 Months Ended
	Sep. 30, 2018
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 2018 2017 2018 2017 (in thousands) Collaboration revenue: Milestone payments $ — $ — $ 3,690 $ — Reimbursed payments 814 1,493 3,248 1,991 Total collaboration revenue $ 814 $ 1,493 $ 6,938 $ 1,991

Reverse Merger (Tables)

Reverse Merger (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	The following table summarizes the net assets acquired based on their estimated fair values immediately prior to the Merger (in thousands): Cash and cash equivalents $ 1,280 Prepaid and other assets 248 Accrued liabilities (1,324 ) Net acquired tangible assets $ 204

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
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 $ 2,490 $ 2,229 Leasehold improvements 741 737 Computer hardware and software 409 355 Furniture and fixtures 126 77 Property and equipment, gross 3,766 3,398 Less: accumulated depreciation and amortization (3,015 ) (2,835 ) Property and equipment, net $ 751 $ 563

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Components of Accrued Liabilities	Accrued liabilities consisted of the following: September 30, December 31, (in thousands) Accrued outsourced clinical trial and preclinical studies $ 2,005 $ 581 Accrued employee compensation and related taxes 1,259 1,538 Accrued legal fees and expenses 358 185 Accrued equipment and lab materials 284 197 Accrued other professional service fees 101 232 Deferred and accrued facility lease obligations 83 74 Value of liability-classified stock purchase warrants 82 82 Other accrued liabilities 164 102 Total accrued liabilities $ 4,336 $ 2,991

Notes Payable (Tables)

Notes Payable (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Composition of Notes Payable	Amounts outstanding under the SVB loan agreements were as follows: September 30, December 31, (in thousands) Principal amount outstanding $ 10,000 $ 10,000 Unamortized debt discount (80 ) (119 ) Accreted final payment fee 285 41 Total note payable 10,205 9,922 Less: current maturities (1,291 ) — Long-term note payable, net of current portion $ 8,914 $ 9,922
Future Annual Minimum Principal Payments of Notes Payable	Future annual minimum principal payments under the 2017 SVB Loan Agreement as of September 30, 2018 for the respective calendar years are as follows (in thousands): 2018 $ — 2019 2,333 2020 4,000 2021 3,667 Total $ 10,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 for the respective calendar year were as follows (in thousands): 2018 $ 99 2019 404 2020 277 Total $ 780

Warrants (Tables)

Warrants (Tables)	9 Months Ended
	Sep. 30, 2018
Other Liabilities Disclosure [Abstract]
Summary of Warrants	As of September 30, 2018 , the Company had 49,349 Common Stock Warrants outstanding at a weighted average exercise price of $27.65 . A summary of outstanding Common Stock purchase warrants as of September 30, 2018 is as follows: Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 24,097 $7.15 2024 49,349

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [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, 2017 2,863 $ 4.85 Granted 1,069 $ 7.48 Exercised (274 ) $ 0.66 Forfeited or canceled (141 ) $ 9.80 Outstanding at September 30, 2018 3,517 $ 5.78
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 2018 2017 Expected term, in years 6.33 6.44 Expected volatility 84.9 % 83.8 % Risk-free interest rate 2.6 % 2.1 % Expected dividend yield — % — % Weighted-average exercise price $ 7.48 $ 11.48
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 2018 2017 (in thousands) Research and development $ 933 $ 643 General and administrative 1,809 1,050 Total share-based compensation expense $ 2,742 $ 1,693

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Potentially dilutive securities include the following: September 30, 2018 2017 (in thousands) Options to purchase Common Stock 3,517 2,969 Warrants to purchase Common Stock 49 25 Total 3,566 2,994

Description of Business - Narra

Description of Business - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (115,979)		$ (115,979)		$ (93,593)
Net loss	(9,011)	$ (5,834)	(22,386)	$ (20,126)
Cash and cash equivalents	31,700	$ 42,805	31,700	$ 42,805	47,441	$ 22,104
Short-term investments	$ 38,827		$ 38,827		$ 0

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
U.S. treasury securities (included in short-term investments)	$ 38,800
Level 1
Assets:
Money market funds (included in cash and cash equivalents)	32,539	$ 47,653
U.S. treasury securities (included in short-term investments)	38,827	0
Total assets	71,366	47,653
Liabilities:
Liabilities, fair value disclosure	0	0
Level 3
Assets:
Money market funds (included in cash and cash equivalents)	0	0
U.S. treasury securities (included in short-term investments)	0	0
Total assets	0	0
Liabilities:
Liabilities, fair value disclosure	$ 82	$ 82

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)segment	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Accounting Policies [Abstract]
Impairment charges	$ 0	$ 0	$ 0	$ 0
Income tax penalties and interest expense	0	$ 0	$ 0	$ 0
Number of operating segments | segment			1
Available-for-sale securities, cost basis	38,800,000		$ 38,800,000
Available-for-sale securities, fair value	38,800,000		38,800,000
Available-for-sale securities, unrealized loss	(6,000)		(6,000)
Accumulated other comprehensive loss	$ (6,000)		$ (6,000)		$ 0
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives			3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives			5 years

Strategic Alliance and Collab_3

Strategic Alliance and Collaboration with Servier - Narrative (Details) € in Millions	Mar. 16, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2016EUR (€)	Dec. 31, 2016USD ($)	Sep. 30, 2018EUR (€)	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			$ 944,000	$ 1,631,000	$ 7,910,000	$ 2,811,000
Amounts incurred but not yet billed										$ 800,000	$ 1,100,000
Accounts receivable										1,382,000	1,456,000
Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential commercialization milestone payments									€ 175	203,000,000
Milestone payment earned	$ 3,700,000	$ 3,000,000
Minimum | Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential development milestone payments									5.8	6,700,000
Potential regulatory milestone payments									10	11,600,000
Maximum | Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential development milestone payments									13.8	16,000,000
Potential regulatory milestone payments									€ 40	46,400,000
Reimbursed payments
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue					3,248,000
License revenue | Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue					0		€ 9	$ 12,400,000
Collaboration revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			$ 814,000	$ 1,493,000	$ 6,938,000	$ 1,991,000
Servier
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable										$ 1,400,000	$ 1,400,000

Strategic Alliance and Collab_4

Strategic Alliance and Collaboration with Servier - Collaboration Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 944	$ 1,631	$ 7,910	$ 2,811
Total collaboration revenue
Disaggregation of Revenue [Line Items]
Total revenue	814	1,493	6,938	1,991
Milestone payments
Disaggregation of Revenue [Line Items]
Total revenue	$ 0	$ 0	3,690	$ 0
Reimbursed payments
Disaggregation of Revenue [Line Items]
Total revenue			$ 3,248

Reverse Merger - Narrative (Det

Reverse Merger - Narrative (Details) $ / shares in Units, $ in Thousands	Sep. 30, 2018$ / sharesshares	Dec. 31, 2017$ / sharesshares	Feb. 13, 2017USD ($)shares	Feb. 12, 2017USD ($)shares
Business Acquisition [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock, shares outstanding (in shares) | shares	30,833,367	22,568,006
Preferred stock
Business Acquisition [Line Items]
Exchange rate of common stock				1
Signal
Business Acquisition [Line Items]
Common stock, shares outstanding (in shares) | shares			21,309,440	1,024,960
Market capitalization | $				$ 12,600
Net acquired tangible assets | $			$ 204
Signal | Signal Shares issued to Miragen Common Shareholders
Business Acquisition [Line Items]
Exchange rate of common stock			0.7031
Signal | Pre-Merger MIragen Stockholders, Warrantholders, and Optionholders
Business Acquisition [Line Items]
Ownership percentage			95.20%
Signal | Signal Shareholders
Business Acquisition [Line Items]
Ownership interest prior to merger			95.90%
Signal | Miragen Shareholders
Business Acquisition [Line Items]
Ownership interest prior to merger			4.10%

Reverse Merger - Summary of Ass

Reverse Merger - Summary of Assets Acquired and Liabilities Assumed (Details) - Signal $ in Thousands	Feb. 13, 2017USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 1,280
Prepaid and other assets	248
Accrued liabilities	(1,324)
Net acquired tangible assets	$ 204

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,766	$ 3,398
Less: accumulated depreciation and amortization	(3,015)	(2,835)
Property and equipment, net	751	563
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,490	2,229
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	741	737
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment	409	355
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	$ 126	$ 77

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 100	$ 100	$ 206	$ 227

Accrued Liabilities - Component

Accrued Liabilities - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued outsourced clinical and preclinical studies	$ 2,005	$ 581
Accrued employee compensation and related taxes	1,259	1,538
Accrued legal fees and expenses	358	185
Accrued equipment and lab materials	284	197
Accrued other professional service fees	101	232
Deferred and accrued facility lease obligations	83	74
Value of liability-classified stock purchase warrants	82	82
Other accrued liabilities	164	102
Total accrued liabilities	$ 4,336	$ 2,991

Notes Payable - Narrative (Deta

Notes Payable - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Nov. 30, 2017	Apr. 30, 2015
Notes Payable to Banks | Prime Rate
Debt Instrument [Line Items]
Interest rate at period end	5.25%
2017 SVB Loan Agreement | Notes Payable to Banks
Debt Instrument [Line Items]
Face amount		$ 10
Repayment period	30 months
Interest-only period	18 months
Final payment fee	$ 0.9
2015 SVB Loan Agreement
Debt Instrument [Line Items]
Interest margin in event of default	5.00%
2015 SVB Loan Agreement | Notes Payable to Banks
Debt Instrument [Line Items]
Face amount			$ 5
Repayment period	30 months
Interest-only period	18 months
Final payment fee percent			5.50%
Loss on debt extinguishment	$ 0.1
2015 SVB Loan Agreement | Notes Payable to Banks | Prime Rate
Debt Instrument [Line Items]
Variable rate	(0.25%)

Notes Payable - Composition of

Notes Payable - Composition of Notes Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Principal amount outstanding	$ 10,000	$ 10,000
Unamortized debt discount	(80)	(119)
Accreted final payment fee	285	41
Total note payable	$ 10,205	$ 9,922

Notes Payable - Future Annual M

Notes Payable - Future Annual Minimum Principal Payments (Details) $ in Thousands	Sep. 30, 2018USD ($)
Debt Disclosure [Abstract]
2,018	$ 0
2,019	2,333
2,020	4,000
2,021	3,667
Total	$ 10,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) € in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		42 Months Ended
	Oct. 31, 2010EUR (€)	Oct. 31, 2010USD ($)	Sep. 30, 2018USD ($)arrangement	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)arrangement	Sep. 30, 2017USD ($)	Mar. 31, 2018USD ($)
Commitments and Contingencies [Line Items]
License fee expense					$ 700,000
Rent expense			$ 100,000	$ 100,000	300,000	$ 200,000
Operating expenses of leases			$ 100,000	$ 100,000	$ 200,000	200,000
Yale University
Commitments and Contingencies [Line Items]
Term of agreement					5 years
Proceeds from collaboration							$ 800,000
University of Texas
Commitments and Contingencies [Line Items]
Number of arrangements | arrangement			2		2
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
University of Texas | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			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
RICC
Commitments and Contingencies [Line Items]
Potential future milestone payments per licensed product			5,200,000		5,200,000
Payments for raw materials					500,000	$ 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
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
t2cure | European Union or Japan
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			$ 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, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 99
2,019	404
2,020	277
Total	$ 780

Capital Stock - Narrative (Deta

Capital Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 31, 2017	Feb. 13, 2017	Aug. 31, 2018	Feb. 28, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017
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
Payments of stock issuance costs		$ 1,500
Underwriter Option
Class of Stock [Line Items]
Proceeds from the sale of common stock				$ 37,900
Shares sold (in shares)				7,414,996
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					$ 2,747	$ 2,711
Payments of stock issuance costs					82	$ 172
Commission fee percent	3.00%
Maximum | ATM Agreement
Class of Stock [Line Items]
Aggregate offering					50,000
Pre-Merger
Class of Stock [Line Items]
Issuance of common stock in public offering, net of issuance cost (in shares)		9,045,126
Sale price (in usd per share)		$ 4.50
Proceeds from the sale of common stock		$ 39,200
Post-Merger
Class of Stock [Line Items]
Issuance of common stock in public offering, net of issuance cost (in shares)		6,359,628
Sale price (in usd per share)		$ 6.40
LLS
Class of Stock [Line Items]
Transaction value			$ 5,000
Sale price (in usd per share)			$ 6.62
Proceeds from the sale of common stock			$ 900
Shares sold (in shares)			150,987
Common stock
Class of Stock [Line Items]
Proceeds from the sale of common stock					$ 2,700		$ 10,200
Shares sold (in shares)					372,852		1,213,386
Weighted-average share price (in usd per share)					$ 7.37		$ 8.74

Warrants - Stock Warrants Outst

Warrants - Stock Warrants Outstanding (Details)	Sep. 30, 2018$ / sharesshares
Common Stock Warrants
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares) | shares	49,349
Exercise price (in usd per share) | $ / shares	$ 27.65
Expiration Date 2019 and 2020
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares) | shares	13,534
Exercise price (in usd per share) | $ / shares	$ 80.70
Expiration Date 2025
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares) | shares	11,718
Exercise price (in usd per share) | $ / shares	$ 8.53
Expiration Date 2024
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares) | shares	24,097
Exercise price (in usd per share) | $ / shares	$ 7.15

Warrants - Narrative (Details)

Warrants - Narrative (Details) - Common Stock Warrants	Sep. 30, 2018$ / sharesshares
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares) | shares	49,349
Warrant exercise price (in usd per share) | $ / shares	$ 27.65

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended		27 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance (in shares)	4,182,404
Additional shares authorized for plan (in shares)	902,720
Outstanding, exercisable equity awards	1,840,317
Remaining equity awards available for future issuances	722,269
Expiration period	10 years
Percent of common stock authorized under plan	4.00%
Unrecognized employee stock-based compensation costs	$ 9.3
Remaining weighted-average period for RSUs	2 years 9 months 1 day
Options to purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	3,517,000			2,863,000
Expiration period	10 years
Weighted average fair value per option (in usd per share)	$ 5.51	$ 8.32
Shares issued in period (in shares)	1,069,000
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
2008 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	1,645,892
2016 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Basis for equity incentive plan (in shares)	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)	400,000
Issuance of common stock for cash under employee stock purchase plan (in shares)	52,444		66,000

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - Options to purchase Common Stock - $ / shares shares in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Number of Options (in thousands)
Beginning balance (in shares)	2,863
Granted (in shares)	1,069
Exercised (in shares)	(274)
Forfeited or canceled (in shares)	(141)
Ending balance (in shares)	3,517
Weighted Average Exercise Price
Beginning balance (in usd per share)	$ 4.85
Granted (in usd per share)	7.48	$ 11.48
Exercised (in usd per share)	0.66
Forfeited or canceled (in usd per share)	(9.80)
Ending balance (in usd per share)	$ 5.78

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, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term, in years	6 years 4 months	6 years 5 months 9 days
Expected volatility	84.90%	83.80%
Risk-free interest rate	2.60%	2.10%
Expected dividend yield	0.00%	0.00%
Weighted-average exercise price (in usd per share)	$ 7.48	$ 11.48

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, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 2,742	$ 1,693
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	933	643
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 1,809	$ 1,050

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, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	3,566	2,994
Options to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	3,517	2,969
Warrants to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	49	25

Net Loss Per Share - Narrative

Net Loss Per Share - Narrative (Details)	Feb. 13, 2017	Feb. 12, 2017
Preferred stock
Conversion of Stock [Line Items]
Exchange rate of common stock		1
Signal Shares issued to Miragen Common Shareholders | Signal
Conversion of Stock [Line Items]
Exchange rate of common stock	0.7031