Viridian Therapeutics (VRDN) 10-Q 11 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 05, 2017
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	Mar. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		21,401,828

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 54,273	$ 22,104
Accounts receivable	277	20
Prepaid expenses and other current assets	2,389	1,753
Total current assets	56,939	23,877
Property and equipment, net	597	625
Other assets	258	258
Total assets	57,794	24,760
Current liabilities:
Accounts payable	1,125	1,007
Accrued liabilities	4,180	3,909
Current portion of notes payable	1,974	1,969
Total current liabilities	7,279	6,885
Notes payable, less current portion	2,347	2,820
Other liabilities	174	0
Total liabilities	9,800	9,705
Commitments and contingencies
Stockholders’ equity (deficit):
Common stock, $0.01 par value; 100,000,000 shares authorized; 21,401,828 and 833,744 shares issued and outstanding at March 31, 2017 and December 31, 2016, respectively	214	8
Additional paid-in capital	121,841	5,147
Accumulated deficit	(74,061)	(67,076)
Total stockholders’ equity (deficit)	47,994	(61,921)
Total liabilities, preferred stock, and stockholders’ equity (deficit)	57,794	24,760
Series A
Current liabilities:
Redeemable convertible preferred stock	0	23,124
Series B
Current liabilities:
Redeemable convertible preferred stock	0	12,975
Series C
Current liabilities:
Redeemable convertible preferred stock	$ 0	$ 40,877

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
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)	21,401,828	833,744
Common stock, shares outstanding (in shares)	21,401,828	833,744
Series A
Redeemable convertible preferred stock, par value (in dollars per share)		$ 0.001
Redeemable convertible preferred stock, shares authorized (in shares)		7,169,176
Redeemable convertible preferred stock, shares issued (in shares)		7,149,176
Redeemable convertible preferred stock, shares outstanding (in shares)	0	7,149,176
Redeemable convertible preferred stock, liquidation preference		$ 21,448
Series B
Redeemable convertible preferred stock, par value (in dollars per share)		$ 0.001
Redeemable convertible preferred stock, shares authorized (in shares)		2,183,318
Redeemable convertible preferred stock, shares issued (in shares)		2,166,651
Redeemable convertible preferred stock, shares outstanding (in shares)	0	2,166,651
Redeemable convertible preferred stock, liquidation preference		$ 13,000
Series C
Redeemable convertible preferred stock, par value (in dollars per share)		$ 0.001
Redeemable convertible preferred stock, shares authorized (in shares)		9,303,000
Redeemable convertible preferred stock, shares issued (in shares)		9,268,563
Redeemable convertible preferred stock, shares outstanding (in shares)	0	9,268,563
Redeemable convertible preferred stock, liquidation preference		$ 41,060

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue:
Revenue under strategic alliance and collaboration	$ 10	$ 917
Grant revenue	452	0
Total revenue	462	917
Operating expenses:
Research and development	4,120	3,466
General and administrative	3,281	992
Total operating expenses	7,401	4,458
Loss from operations	(6,939)	(3,541)
Other income (expense):
Interest and other income	30	7
Interest and other related expense	(71)	(89)
Net loss	(6,980)	(3,623)
Accretion of redeemable convertible preferred stock to redemption value	(5)	(12)
Net loss available to common stockholders	$ (6,985)	$ (3,635)
Net loss per share, basic and diluted (in dollars per share)	$ (0.60)	$ (5.58)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	11,555,286	651,041

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Preferred Stock and Stockholders' Equity (Deficit) - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Series A	Series B	Series C
Beginning balance (in shares) at Dec. 31, 2016					7,149,176	2,166,651	9,268,563
Beginning balance at Dec. 31, 2016					$ 23,124	$ 12,975	$ 40,877
Redeemable Convertible Preferred Stock
Accretion of preferred stock to current redemption value					$ 1	$ 1	$ 3
Ending balance (in shares) at Mar. 31, 2017					0	0	0
Ending balance at Mar. 31, 2017					$ 0	$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2016	833,744	833,744
Beginning balance at Dec. 31, 2016	$ (61,921)	$ 8	$ 5,147	$ (67,076)
Stockholders’ deficit
Sale of common stock to investors (in shares)		6,359,628
Issuance of common stock to investors, net of issuance cost	39,156	$ 64	39,092
Accretion of preferred stock to current redemption value	(5)			(5)
Conversion of preferred stock into common stock (in shares)		13,066,666			(7,149,176)	(2,166,651)	(9,268,563)
Conversion of preferred stock into common stock	76,981	$ 131	76,850		$ (23,125)	$ (12,976)	$ (40,880)
Issuance of common stock upon reverse merger (in shares)		1,024,960
Issuance of common stock upon reverse merger	204	$ 10	194
Reclassification of preferred stock warrant to common stock warrant	51		51
Issuance of common stock upon exercise of warrants (in shares)		16,387
Exercises of stock options and issuance of restricted stock awards (in shares)		100,443
Exercises of stock options	89	$ 1	88
Share-based compensation expense	419		419
Net loss	$ (6,980)			(6,980)
Ending balance (in shares) at Mar. 31, 2017	21,401,828	21,401,828
Ending balance at Mar. 31, 2017	$ 47,994	$ 214	$ 121,841	$ (74,061)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (6,980)	$ (3,623)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	73	81
Share-based compensation	419	42
Non-cash interest expense	32	42
Changes in operating assets and liabilities:
Accounts receivable	(257)	60
Prepaid expenses and other assets	(534)	(63)
Deferred revenue	0	(173)
Accounts payable	118	235
Accrued liabilities	(1,054)	(771)
Net cash used in operating activities	(8,183)	(4,170)
Cash flows from investing activities:
Cash acquired in reverse merger	1,280	0
Purchases of property and equipment	(44)	(105)
Net cash provided by (used in) investing activities	1,236	(105)
Cash flows from financing activities:
Proceeds from the sale of common stock	40,703	0
Payment of issuance costs associated with the sale of common stock	(1,176)	0
Payment of principal of notes payable	(500)	0
Proceeds from the exercise of stock options	89	0
Net cash provided by financing activities	39,116	0
Net increase (decrease) in cash and cash equivalents	32,169	(4,275)
Cash and cash equivalents at beginning of period	22,104	21,235
Cash and cash equivalents at end of period	54,273	16,960
Supplemental disclosure of cash flow information
Interest paid	38	41
Supplemental disclosure of non-cash investing and financing activities
Conversion of preferred stock to common stock	76,981	0
Liabilities assumed, net of non-cash assets received in reverse merger	1,076	0
Transfer of common stock issuance costs from prepaid expenses and other current assets to equity	331	0
Unpaid financing costs included in prepaid expenses and other current assets and accrued liabilities	184	0
Unpaid common stock issuance costs included in accrued liabilities	40	0
Reclassification of preferred stock warrant to common stock warrant	51	0
Accretion of offering costs	$ 5	$ 12

Description of Business

Description of Business	3 Months Ended
	Mar. 31, 2017
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 therapeutics with a specific focus on microRNAs and their roles in diseases where there is a high unmet medical need. microRNAs are short RNA molecules, or oligonucleotides, that regulate gene expression or activity and play a vital role in influencing the pathways responsible for many disease processes. Miragen believes its experience in microRNA biology and chemistry, drug discovery, bioinformatics, and translational medicine provides it with a potential competitive advantage to identify and develop microRNA-targeted drugs designed to regulate gene pathways to result in disease modification. Miragen uses its expertise in systems biology and oligonucleotide chemistry to discover and develop a pipeline of product candidates. Miragen’s two lead product candidates, MRG-106 and MRG-201, are currently in Phase 1 clinical trials. Miragen’s clinical product candidate for the treatment of certain cancers, MRG-106, is an inhibitor of microRNA-155, which is found at abnormally high levels in several blood cancers. Miragen’s clinical product candidate for the treatment of pathological fibrosis, MRG-201, is a replacement for microRNA-29 (“miR-29”), which is found at abnormally low levels in a number of pathological fibrotic conditions, including cutaneous, cardiac, renal, hepatic, and pulmonary fibrosis, as well as in systemic sclerosis. In addition to Miragen’s clinical programs, it continues to discover and develop a pipeline of preclinical product candidates. The goal of Miragen’s translational medicine strategy is to progress rapidly to first-in-human studies once it has established the pharmacokinetics (the movement of drug into, through, and out of the body), pharmacodynamics (the effect and mechanism of action of a drug), safety, and manufacturability of the product candidate in preclinical studies. In January 2011, the Company formed its sole, wholly-owned subsidiary, Miragen Therapeutics Europe Limited (“Miragen Europe”), for the sole purpose of submitting regulatory filings in Europe. Miragen Europe has no employees or operations. On February 13, 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.” The holders of shares of Private Miragen common stock outstanding immediately prior to the Merger received approximately 0.7031 shares of the Company’s common stock in exchange for each share of Private Miragen common stock in the Merger. Following the Merger on February 13, 2017, the combined company had 21,309,440 shares of common stock outstanding at a par value of $0.01 per share (the “Common Stock”) as compared to the par value of Private Miragen’s common stock of $0.001 per share. 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. Liquidity The Company has incurred annual net operating losses since its inception. As of March 31, 2017 , the Company had an accumulated deficit of $74.1 million and expects to continue to incur losses for the next several years. On February 13, 2017, the date of the Merger, Private Miragen received $40.7 million in cash, before offering expenses, from the issuance of common stock to investors. Management believes that the $54.3 million of cash and cash equivalents on hand at March 31, 2017 will be sufficient to fund its operations in the normal course of business and allow the Company to meet its liquidity needs through 2018.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
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 Europe, and 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, 2017, or for any other interim period, or for any other future year. The balance sheet as of December 31, 2016 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 8-K/A for the year ended December 31, 2016, filed with the SEC on March 31, 2017. 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, other than as disclosed. Use of Estimates Miragen’s consolidated financial statements are prepared in accordance with U.S. GAAP, which requires Miragen 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 Miragen’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 Miragen recognizes revenue principally from upfront payments for licenses or options to obtain licenses in the future and milestone payments that are generated from defined research or development events, as well as from amounts for other research and development services under strategic alliance and collaboration agreements. Miragen 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 Company’s License and Collaboration Agreement (the “Servier Collaboration Agreement”) with Les Laboratoires Servier and Institut de Rechereches Servier (collectively, “Servier”), 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. Miragen recognizes revenue from non-refundable upfront license fees over the term of performance under the Servier Collaboration Agreement. When the performance period is not specified, Miragen 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 Miragen’s estimates. Share-Based Compensation Miragen 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. Miragen recognizes share-based compensation expense on a straight-line basis over the vesting term. Miragen accounts for stock options issued to non-employees 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 and include compensation and related benefits, share-based compensation, license fees, laboratory supplies, facilities, and overhead costs. Miragen occasionally makes non-refundable advance payments for goods and services that will be used in future research and development activities. These payments are capitalized and recorded as expense in the period in which Miragen receives the goods or when the services are performed. Miragen records upfront and milestone payments to acquire contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in Miragen receiving future economic benefit from the acquired contractual rights. Miragen 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 Miragen 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. Miragen’s accrued expenses for preclinical studies and clinical trials are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and for other trial-related activities. Payments under Miragen’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, Miragen obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to Miragen’s research and development expenses may be necessary in future periods as its estimates change. Cash and Cash Equivalents Miragen classifies all highly-liquid investments that have maturities of 90 days or less at the date of purchase as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments. Fair Value of Financial Instruments The carrying amounts of financial instruments, including cash and cash equivalents, accrued compensation, preclinical study accruals, and accounts payable, approximate fair value due to their short-term maturities. The carrying amount of Miragen’s note payable approximates its fair value as its terms are comparable to what would be included in similar debt instruments. The Company accounts for its warrants to purchase common and preferred stock pursuant to ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for redeemable preferred stock and certain warrants for common stock as liabilities. The warrants are reported at their estimated fair value and any changes in fair value are reflected in interest expense and other related expenses. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Inputs used to measure fair value are classified into the following hierarchy: • Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities • Level 2—Unadjusted quoted prices in active markets for similar assets or liabilities; unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active; or inputs other than quoted prices that are observable for the asset or liability • Level 3—Unobservable inputs for the asset or liability Assets and liabilities measured at fair value on a recurring basis consisted of the following: March 31, 2017 December 31, 2016 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 53,898 $ — $ 22,189 $ — Liabilities: Preferred and common stock warrants (included in accrued and other liabilities) $ — $ 82 $ — $ 133 A reconciliation of the beginning and ending balances of Miragen’s liabilities measured at fair value using significant unobservable, or Level 3, inputs are as follows for the three months ended March 31, 2017 (in thousands): Balance of liability as of December 31, 2016 $ 133 Reclassification of preferred stock warrant to common stock warrant (51 ) Balance of liability as of March 31, 2017 $ 82 Concentrations of Credit Risk Financial instruments that potentially subject Miragen to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. Miragen maintains deposits in federally insured financial institutions in excess of federally insured limits. Miragen has not experienced any losses in such accounts. Miragen invests its excess cash primarily in deposits and money market funds held with two financial institutions. Property and Equipment Miragen 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 Miragen 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 months ended March 31, 2017 and 2016 . 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 Miragen 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 defined as the change in equity during a period from transactions and other events and/or circumstances from non-owner sources. If the Company had comprehensive gains (losses), they would be reflected in the statement of operations and comprehensive loss and as a separate component in the statement of stockholders’ equity (deficit). There were no elements of comprehensive loss during the three months ended March 31, 2017 and 2016 . Income Taxes Miragen 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. Miragen’s significant deferred tax assets are for net operating loss carryforwards, tax credits, and capitalized start-up costs. Miragen has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, Miragen has concluded that it is more likely than not that its deferred tax assets will not be realized. Miragen has no unrecognized tax benefits. Miragen classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations as general and administrative expenses. No such expenses have been recognized during the three months ended March 31, 2017 and 2016 . Segment Information Miragen operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All of Miragen’s equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with its 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 (Topic 606) , which outlines 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. In March 2016, the FASB issued ASU No. 2016-08 , Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations . The purpose of this standard is to clarify the implementation of guidance on principal versus agent considerations related to ASU 2014-09. The standard has the same effective date as ASU 2014-09 described above. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customer, which provides clarity related to ASU 2014-09 regarding identifying performance obligations and licensing implementation. The standard has the same effective date as ASU 2014-09 described above. In May 2016, the FASB issued ASU 2016-12: Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which provides narrow scope improvements and practical expedients related to ASU 2014-09. The purpose of this standard is to clarify certain narrow aspects of ASU 2014-09, such as assessing the collectability criterion, presentation of sales taxes, and other similar taxes collected from customers, noncash consideration, contract modifications at transition, completed contracts at transition, and technical correction. The standard has the same effective date as ASU 2014-09 described above. In December 2016, the FASB issued ASU 2016-20: Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . The amendments in this standard affect narrow aspects of guidance issued in ASU 2014-09. The standard has the same effective date as ASU 2014-09 described above. The Company plans to adopt these new standards in the first quarter of 2019 and does not anticipate the adoption of these pronouncements to have a material impact with regard to its current contracts on its condensed consolidated financial statements. As of March 31, 2017 , there were no contracts that will be in effect (actively) as of the transition date and, accordingly, the Company has not yet determined the effect of the standard on its condensed consolidated financial statements. The Company’s selected implementation transition method will be dependent upon contracts that are in place closer to the transition date. Deferred Taxes In November 2015, the FASB issued ASU No. 2015-17 , Balance Sheet Classification of Deferred Taxes . ASU No. 2015-17 requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This standard is effective for the Company for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods thereafter. The Company does not believe the adoption of this standard will have a material impact on its condensed consolidated financial statements due to the full valuation allowance on all net deferred tax assets. Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842), which supersedes FASB ASC Topic 840, Leases (Topic 840), which provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The standard is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods thereafter, with early adoption permitted. At adoption, this update will be applied using a modified retrospective approach. The Company currently has one lease for its primary business location that will be affected by the new standard. The Company is currently evaluating the impact of this standard on its condensed consolidated financial statements. Share-based Compensation In March 2016, the FASB issued ASU No. 2016-09 , Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which is intended to simplify accounting for equity share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. This standard is effective for the Company for annual periods beginning after December 15, 2017, and interim periods thereafter. Amendments related to the timing of when excess tax benefits are recognized, minimum statutory withholding requirements, forfeitures, and intrinsic value should be applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is adopted. Amendments related to the presentation of employee taxes paid on the statement of cash flows when an employer withholds shares to meet the minimum statutory withholding requirement should be applied retrospectively. Amendments requiring recognition of excess tax benefits and tax deficiencies in the income statement and the practical expedient for estimating the expected term should be applied prospectively. An entity may elect to apply the amendments related to the presentation of excess tax benefits on the statement of cash flows using either a prospective transition method or a retrospective transition method. The Company is currently evaluating the impact of this standard on its condensed consolidated financial statements. Other new pronouncements issued but not effective as of March 31, 2017 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	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Strategic Alliance and Collaboration with Servier	STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER In October 2011, Miragen entered into the Servier Collaboration Agreement with Servier for the research, development, and commercialization of RNA-targeting therapeutics in cardiovascular disease, which was subsequently amended in May 2013, May 2014, May 2015, September 2016, and May 2017. Under the Servier Collaboration Agreement, Miragen granted Servier an exclusive license to research, develop, and commercialize RNA-targeting therapeutics for three targets in the cardiovascular field. As of March 31, 2017 , three named targets existed under the Servier Collaboration Agreement. In May 2017, Miragen and Servier agreed to amend the Servier Collaboration Agreement to remove three existing targets, add one named target, and provide Servier with the right to add one additional target through September 2019. Servier also agreed to pay Miragen a one-time milestone at a specified amount upon the earlier of the completion of a specified development goal or November 15, 2017. Under the terms of the amendment, the term of the Research Collaboration has been extended from October 2017 through September 2019. Servier’s rights to each named target is limited to therapeutics in the cardiovascular field in their territory, which is worldwide except for the United States and Japan. Miragen retains all rights in the United States and Japan. In connection with entering into the Servier Collaboration Agreement with Servier, Miragen received a nonrefundable upfront payment of $8.4 million ( €6.0 million ) in 2011 and an additional $4.0 million ( €3.0 million ) in 2013 when Servier exercised its right to name a third target under the Servier Collaboration Agreement. Miragen is also eligible to receive development milestone payments of €5.8 million to €13.8 million ( $6.2 million to $14.7 million as of March 31, 2017 ) and regulatory milestone payments of €10.0 million to €40.0 million ( $10.7 million to $42.7 million as of March 31, 2017 ) for each target. Additionally, Miragen may receive up to €175 million ( $186.9 million as of March 31, 2017 ) 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. As part of the Servier Collaboration Agreement, Miragen established a multiple-year research collaboration, under which Miragen jointly performs agreed upon research activities directed to the identification and characterization of named targets and oligonucleotides in the cardiovascular field, which Miragen refers to as the Research Collaboration. The current term of the Research Collaboration extends through September 2019. Servier is responsible for funding the costs of the Research Collaboration, as defined under the Servier Collaboration Agreement. During the three months ended March 31, 2017 and 2016 , Miragen recognized as revenue amounts reimbursable to Miragen under the Servier Collaboration Agreement primarily for research and development activities of $10 thousand and $0.7 million , respectively. 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 Miragen for a specified portion of such costs Miragen 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 Miragen 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 Miragen subsequently enters into a U.S. partner agreement, or if Miragen 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. Miragen is responsible, by itself or through a third-party manufacturer, for the manufacture and supply of all licensed oligonucleotides during the preclinical phase of development under the Sevier Collaboration Agreement while Servier is primarily responsible for manufacture and supply of all licensed oligonucleotides and product during the clinical phase of development under the Servier Collaboration Agreement. Each party is responsible for the commercial supply of any licensed product to be sold in its respective territory under the Servier Collaboration Agreement. Under the Servier Collaboration Agreement, Miragen also granted Servier a royalty-free, non-exclusive license to develop a companion diagnostic in Miragen’s territory for any therapeutic product that may be developed by Servier under the Servier Collaboration Agreement. Miragen also granted Servier an exclusive, royalty-free license to commercialize such a companion diagnostic in Miragen’s 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 Miragen or (ii) upon determination of a safety issue relating to development under the agreement upon a specified number of days’ prior notice to Miragen. Either party may terminate the Servier Collaboration Agreement upon a material breach by the other party which is not cured within a specified number of days. Miragen may also terminate the agreement if Servier challenges any of the patents licensed by Miragen to Servier. Miragen 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, Miragen 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. Miragen measures its progress under the proportional performance method based on actual and estimated full-time equivalents. Miragen 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 revenue during the three months ended March 31, 2017 . During the three months ended March 31, 2016 , the Company recognized license revenue of $0.2 million . In total, for the three months ended March 31, 2017 and 2016 , Miragen recognized $10 thousand and $0.9 million respectively, as revenue under the Servier Collaboration Agreement. Amounts incurred but not billed to Servier for research activities performed totaled zero and $0.3 million as of March 31, 2017 and December 31, 2016 . These amounts are included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheets.

Reverse Merger

Reverse Merger	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Reverse Merger	REVERSE MERGER On February 13, 2017, Private Miragen completed the Merger as discussed in Note 1. For accounting purposes, Private Miragen is considered to be acquiring 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 own approximately 95.2% of the combined company’s outstanding common stock immediately following the closing of the Merger, (ii) former Private Miragen directors hold all of the board seats in the combined company, and (iii) Private Miragen management holds 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 as of February 13, 2017, 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 Signal 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 of 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 on February 13, 2017, 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). On February 13, 2017, prior to the effectiveness of the Merger, the Company 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 estimated preliminary purchase consideration. The following table summarizes the net assets acquired based on their estimated fair values as of February 13, 2017, 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	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	PROPERTY AND EQUIPMENT Property and equipment, net consisted of the following: March 31, December 31, (in thousands) Lab equipment $ 2,182 $ 2,163 Furniture and fixtures 51 51 Computer hardware and software 303 281 Leasehold improvements 688 688 Property and equipment, gross 3,224 3,183 Less: accumulated depreciation and amortization (2,627 ) (2,558 ) Property and equipment, net $ 597 $ 625 Depreciation and amortization expense was $0.1 million for the three months ended March 31, 2017 and 2016 .

Accrued Liabilities

Accrued Liabilities	3 Months Ended
	Mar. 31, 2017
Payables and Accruals [Abstract]
Accrued Liabilities	ACCRUED LIABILITIES Accrued liabilities consisted of the following: March 31, December 31, (in thousands) Accrued outsourced clinical and preclinical studies $ 1,869 $ 1,684 Accrued employee compensation and related taxes 749 928 Accrued legal fees and expenses 636 759 Accrued professional service fees 496 124 Accrued equipment and lab materials 184 — Value of liability-classified stock purchase warrants 82 133 Deferred and accrued facility lease obligations 50 221 Accrued property and franchise taxes 37 38 Other accrued liabilities 77 22 Total accrued liabilities $ 4,180 $ 3,909

Notes Payable

Notes Payable	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Notes Payable	NOTES PAYABLE 2015 Silicon Valley Bank Loan Agreement In April 2015, Private Miragen entered into a loan and security agreement with Silicon Valley Bank (the “2015 SVB Loan Agreement”) to borrow up to $10.0 million in two separate tranches. The first tranche of $5.0 million was funded in May 2015 and is being repaid over a 30 -month period following an 18 -month interest only payment period that ended in November 2016. Amounts outstanding bear interest at the prime rate minus 0.25% ( 3.75% at March 31, 2017 ), with a final payment fee equal to 5.50% of amounts borrowed. Borrowings are secured by a priority security interest, right, and title in all business assets, excluding the Company’s intellectual property, which is subject to a negative pledge. In connection with the first tranche, in April 2015, Private Miragen issued detachable warrants to purchase up to 11,718 shares of Private Miragen preferred stock at an adjusted exercise price of $8.53 per share. At issuance, Private Miragen determined that the warrants should be classified as a liability subject to remeasurment at each balance sheet date. Immediately prior to the Merger, these warrants became exercisable for Private Miragen common stock, which was immediately exchanged for the right to purchase the Company’s Common Stock. The Company determined that, although the warrants were no longer exercisable for redeemable preferred stock, the warrants continued to be classified as a liability after the Merger due to the right of the holder to require Miragen to repurchase the warrants for $0.1 million under certain circumstances. As of March 31, 2017, the Company estimated the fair value of the warrants to be $0.1 million using a probability adjusted present value method with the following assumptions: term of two years, discount rate of 5.0% , and probability of 90.0% . In December 2016, the 2015 SVB Loan Agreement was amended to extend the end of the draw period from December 31, 2016 to July 31, 2017. The second tranche of up to $5.0 million is available under the amended agreement at any time during the draw period. If the second tranche is requested and funded, the Company will be required to issue additional warrants to purchase its Common Stock. If issued, the warrants to purchase Common Stock would include a put right under which Miragen may be required to repurchase the outstanding warrants for a purchase price of $0.1 million . Amounts outstanding under notes payable are as follows: March 31, December 31, (in thousands) Principal amount outstanding $ 4,167 $ 4,667 Unamortized debt discount (11 ) (14 ) Unamortized debt issuance costs (25 ) (31 ) Accretion of final payment fee 190 167 Total notes payable 4,321 4,789 Less: current maturities (1,974 ) (1,969 ) Long-term notes payable, net of current portion $ 2,347 $ 2,820 Future annual minimum principal payments of notes payable are as follows: March 31, (in thousands) 2017 (remainder of year) $ 1,500 2018 2,000 2019 667 Total $ 4,167

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
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 as 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, 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 as 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 as 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 March 31, 2017 , Miragen had five 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 Miragen 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, Miragen 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 three months ended March 31, 2017 , Miragen did not incur upfront or maintenance fees under the UT License Agreements. During the three months ended March 31, 2016 , Miragen 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, Miragen 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 Miragen or its sublicensees successfully commercializes any product candidate subject to the UT License Agreements, Miragen 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. 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, Miragen will have a fully paid license in such country. Miragen 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 Miragen 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 Miragen’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 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, Miragen 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. As consideration for the grant of the license and option, Private Miragen previously paid RICC $2.3 million and issued RICC 856,806 shares of Private Miragen’s Series A convertible preferred stock, which subsequently converted to 602,420 shares of Common Stock. These shares are now owned by Roche Finance Ltd, an affiliate of Roche. 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. Miragen is obligated to make future 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 Miragen undergoes a change in control during the term of the RICC License Agreement. If Miragen grants a third party a sublicense to the RICC Technology, Miragen is required to remit to Roche up to a specified percentage of the upfront and milestone and other specified payments Miragen receives under its sublicense, and if such sublicense covers use of the RICC Technology in the United States or the entire European Union, Miragen will not have any further obligation to pay the fixed milestone payments noted above. If Miragen 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 Miragen by such sublicensee, subject to specified restrictions. Miragen 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. Miragen 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. For the three months ended March 31, 2017 , Miragen paid $0.4 million to Roche for raw materials to be used in our drug manufacturing process. For the three months ended March 31, 2016 , we made no payments to Roche. Subcontract Agreement with Yale University In October 2014, Private Miragen and Yale University (“Yale”) entered into a subcontract agreement and into a subaward agreement in March 2015 (the “Yale Agreements”). The subaward agreement was subsequently amended in February 2016, November 2016, and January 2017. 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 a miR-29 mimicry as a potential therapy for pulmonary fibrosis. In consideration of Miragen’s services under the Yale Agreements, Yale has agreed to pay Miragen up to $1.1 million over five years , subject to the availably of funds under the grant and continued eligibility. Through March 31, 2017 , Miragen has received $33 thousand from Yale pursuant to the Yale Agreements. Under the terms of the Yale Agreements, Miragen retains all rights to any and all intellectual property developed solely by Miragen in connection with the Yale Agreements. Yale has also agreed to provide Miragen 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. 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 in July 2014. Under the t2cure Agreement, the Company has 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 March 31, 2017 ), 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, Miragen is obligated to make the following future milestone payments for each licensed product: (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 Miragen or its sublicensees successfully commercialize any product candidate subject to the t2cure Agreement, Miragen is responsible for royalty payments equal to percentages in the low-single digits upon net sales of licensed products and sublicense fees equal to a percentage in the low-twenties of sublicense income received by Miragen. Miragen 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. Miragen 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, Miragen will have a fully paid license in such country. Miragen 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 Miragen’s bankruptcy or insolvency or upon notice of an uncured material breach. Miragen 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, Miragen has an exclusive, worldwide license, including a right to sublicense, to specified patent rights of BWH and a non-exclusive, worldwide license, including a right to sublicense, to specified technology of BWH. As consideration for this license, Miragen 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 Miragen’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. Miragen 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 Miragen’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 in February 2015 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. Rent expense during the three months ended March 31, 2017 and 2016 , was $0.1 million . Miragen is also required to pay for operating expenses. During the three months ended March 31, 2017 and 2016 , Miragen recorded $0.1 million related to operating expenses of the leased space. Future annual minimum payments under the lease are as follows: March 31, 2017 (in thousands) 2017 (remainder of year) $ 285 2018 391 2019 404 2020 277 Total $ 1,357

Capital Stock

Capital Stock	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Capital Stock	CAPITAL STOCK Common Stock Miragen 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 Miragen’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. At the effective date of the Merger, each outstanding share of Private Miragen common stock was converted into the right to receive approximately 0.7031 shares of the Company’s Common Stock. On February 13, 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, for aggregate consideration of $40.7 million , offset by associated financing fees of $1.5 million . Series Preferred In February 2017, in conjunction with the Merger, all of the outstanding redeemable convertible preferred stock of Private Miragen converted into Private Miragen common stock at a ratio of 1 :1 and was immediately exchanged for the Company’s Common Stock at an exchange ratio of 0.7031 as a result of the Merger. As of March 31, 2017 , 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. Although, the Company’s board of directors has the authority to, at its discretion, issue preferred stock 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 right, 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. ATM Agreement On March 31, 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, and 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. As of March 31, 2017 , no shares had been sold under the ATM Agreement. WARRANTS Stock purchase warrant activity is as follows for the three months ended March 31, 2017 : Common Stock Warrants Preferred Stock Warrants Number Weighted Average Exercise Price Number Weighted Average Exercise Price Outstanding at December 31, 2016 7,031 $ 0.57 25,779 $ 6.21 Warrants acquired in Merger 13,534 $ 80.70 — $ — Preferred stock warrants converted into Common Stock warrants 25,779 $ 6.21 (25,779 ) $ 6.21 Cashless exercise (21,092 ) $ 3.04 — $ — Outstanding at March 31, 2017 25,252 $ 47.21 — $ — A summary of outstanding Common Stock purchase warrants as of March 31, 2017 is as follows: Common Stock Warrants Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 25,252 In connection with the Merger, Private Miragen assumed 13,534 outstanding warrants to purchase shares of the Company’s Common Stock at a weighted average exercise price of $80.70 per share. The warrants expire on various dates in 2019 and 2020.

Warrants

Warrants	3 Months Ended
	Mar. 31, 2017
Other Liabilities Disclosure [Abstract]
Warrants	CAPITAL STOCK Common Stock Miragen 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 Miragen’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. At the effective date of the Merger, each outstanding share of Private Miragen common stock was converted into the right to receive approximately 0.7031 shares of the Company’s Common Stock. On February 13, 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, for aggregate consideration of $40.7 million , offset by associated financing fees of $1.5 million . Series Preferred In February 2017, in conjunction with the Merger, all of the outstanding redeemable convertible preferred stock of Private Miragen converted into Private Miragen common stock at a ratio of 1 :1 and was immediately exchanged for the Company’s Common Stock at an exchange ratio of 0.7031 as a result of the Merger. As of March 31, 2017 , 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. Although, the Company’s board of directors has the authority to, at its discretion, issue preferred stock 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 right, 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. ATM Agreement On March 31, 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, and 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. As of March 31, 2017 , no shares had been sold under the ATM Agreement. WARRANTS Stock purchase warrant activity is as follows for the three months ended March 31, 2017 : Common Stock Warrants Preferred Stock Warrants Number Weighted Average Exercise Price Number Weighted Average Exercise Price Outstanding at December 31, 2016 7,031 $ 0.57 25,779 $ 6.21 Warrants acquired in Merger 13,534 $ 80.70 — $ — Preferred stock warrants converted into Common Stock warrants 25,779 $ 6.21 (25,779 ) $ 6.21 Cashless exercise (21,092 ) $ 3.04 — $ — Outstanding at March 31, 2017 25,252 $ 47.21 — $ — A summary of outstanding Common Stock purchase warrants as of March 31, 2017 is as follows: Common Stock Warrants Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 25,252 In connection with the Merger, Private Miragen assumed 13,534 outstanding warrants to purchase shares of the Company’s Common Stock at a weighted average exercise price of $80.70 per share. The warrants expire on various dates in 2019 and 2020.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION Equity Incentive Plans In February 2017, the Company’s 2014 Stock Incentive Plan (the “2014 Plan”) was terminated as a result of the Merger. There are no awards outstanding under the 2014 Plan and no future awards will be issued under the 2014 Plan. As of March 31, 2017, there were 2,235,779 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. 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 10 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 . Miragen has also granted options that vest in equal monthly or quarterly amounts over periods ranging from 9 to 48 months . A summary of Common Stock option activity is as follows: Number of Options Weighted Average Exercise Price Outstanding at December 31, 2016 2,321 $ 1.44 Granted 732 $ 11.37 Exercised (100 ) $ (0.88 ) Outstanding at March 31, 2017 2,953 $ 3.92 A summary of restricted stock award (“RSA”) activity is as follows: Number of Restricted Stock Awards (in thousands) Weighted Average Grant Date Fair Value Unvested at December 31, 2016 — $ — Granted 1 $ 12.00 Unvested at March 31, 2017 1 $ 12.00 During the three months ended March 31, 2017 , the Company issued RSAs with a zero exercise price; therefore, the fair value of the RSAs was equal to their intrinsic value at the date of grant. During the three months ended March 31, 2017 , the total grant date fair value of RSAs vested was zero . No RSAs were issued during the three months ended March 31, 2016 . Fair Value Assumptions The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options granted. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility, and expected lives of the options. Because Miragen has a limited history of stock purchase and sale activity, expected volatility is based on historical data from public companies similar to Miragen in size and nature of operations. Miragen will continue to use similar entity volatility information until its historical volatility is relevant to measure expected volatility for option grants. Miragen has not applied a forfeiture rate to its assumptions as the impact would not be material to the consolidated financial statements. 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 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 fair value per options granted during the three months ended March 31, 2017 and 2016 was $8.30 and $0.70 , respectively. The fair value was determined by the Black-Scholes option pricing model using the following assumptions: Three Months Ended 2017 2016 Expected term, in years 6.35 5.00 Expected volatility 84.2 % 84.0 % Risk-free interest rate 2.1 % 1.2 % Expected dividend yield — % — % Weighted average fair value of underlying Common Stock $ 11.37 $ 1.05 Stock Options Granted to Non-Employees Miragen 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 three months ended March 31, 2017 and 2016 . Share-Based Compensation Expense Share-based compensation related to employee stock options and RSAs is included in the condensed consolidated statements of operations as follows: Three Months Ended 2017 2016 (in thousands) Research and development $ 123 $ 12 General and administrative 145 26 Total share-based compensation expense $ 268 $ 38 As of March 31, 2017 , Miragen had $7.0 million of total unrecognized employee share-based compensation costs, which Miragen expects to recognize over a weighted-average remaining period of 3.76 years. The total grant-date fair value of RSAs granted during the three months ended March 31, 2017 was $9 thousand . As of March 31, 2017 , the unvested RSAs are expected to be amortized over the remaining weighted-average period of 0.5 years . Miragen recognized $151 thousand and $4 thousand of share-based compensation related to non-employee stock options during the three months ended March 31, 2017 and 2016 , respectively. The amounts are included in general and administrative expenses in the condensed consolidated statements of operations. As of March 31, 2017 , based on the current estimate of fair value, Miragen estimates that the remaining unrecognized share-based compensation expense related to non-employees of $0.1 million will be recorded to expense over a weighted-average remaining period of 1.45 years.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2017
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, since the effects of potentially dilutive securities are antidilutive. Potentially dilutive securities include the following: March 31, 2017 March 31, 2016 (in thousands) Options to purchase Common Stock 2,953 2,222 Warrants to purchase Common Stock 25 7 Redeemable convertible preferred stock — 10,513 Warrants to purchase redeemable convertible preferred stock — 26 Total 2,978 12,768

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
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 Europe, and 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, 2017, or for any other interim period, or for any other future year. The balance sheet as of December 31, 2016 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 8-K/A for the year ended December 31, 2016, filed with the SEC on March 31, 2017.
Use of Estimates	Use of Estimates Miragen’s consolidated financial statements are prepared in accordance with U.S. GAAP, which requires Miragen 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 Miragen’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 Miragen recognizes revenue principally from upfront payments for licenses or options to obtain licenses in the future and milestone payments that are generated from defined research or development events, as well as from amounts for other research and development services under strategic alliance and collaboration agreements. Miragen 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 Company’s License and Collaboration Agreement (the “Servier Collaboration Agreement”) with Les Laboratoires Servier and Institut de Rechereches Servier (collectively, “Servier”), 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. Miragen recognizes revenue from non-refundable upfront license fees over the term of performance under the Servier Collaboration Agreement. When the performance period is not specified, Miragen 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 Miragen’s estimates.
Stock-Based Compensation	Share-Based Compensation Miragen 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. Miragen recognizes share-based compensation expense on a straight-line basis over the vesting term. Miragen accounts for stock options issued to non-employees 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 and include compensation and related benefits, share-based compensation, license fees, laboratory supplies, facilities, and overhead costs. Miragen occasionally makes non-refundable advance payments for goods and services that will be used in future research and development activities. These payments are capitalized and recorded as expense in the period in which Miragen receives the goods or when the services are performed. Miragen records upfront and milestone payments to acquire contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in Miragen receiving future economic benefit from the acquired contractual rights. Miragen 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 Miragen 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. Miragen’s accrued expenses for preclinical studies and clinical trials are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and for other trial-related activities. Payments under Miragen’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, Miragen obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to Miragen’s research and development expenses may be necessary in future periods as its estimates change.
Cash and Cash Equivalents	Cash and Cash Equivalents Miragen classifies all highly-liquid investments that have maturities of 90 days or less at the date of purchase as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of financial instruments, including cash and cash equivalents, accrued compensation, preclinical study accruals, and accounts payable, approximate fair value due to their short-term maturities. The carrying amount of Miragen’s note payable approximates its fair value as its terms are comparable to what would be included in similar debt instruments. The Company accounts for its warrants to purchase common and preferred stock pursuant to ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for redeemable preferred stock and certain warrants for common stock as liabilities. The warrants are reported at their estimated fair value and any changes in fair value are reflected in interest expense and other related expenses. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Inputs used to measure fair value are classified into the following hierarchy: • Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities • Level 2—Unadjusted quoted prices in active markets for similar assets or liabilities; unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active; or inputs other than quoted prices that are observable for the asset or liability • Level 3—Unobservable inputs for the asset or liability
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject Miragen to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. Miragen maintains deposits in federally insured financial institutions in excess of federally insured limits. Miragen has not experienced any losses in such accounts. Miragen invests its excess cash primarily in deposits and money market funds held with two financial institutions.
Property and Equipment	Property and Equipment Miragen 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 Miragen 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 Miragen 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 defined as the change in equity during a period from transactions and other events and/or circumstances from non-owner sources. If the Company had comprehensive gains (losses), they would be reflected in the statement of operations and comprehensive loss and as a separate component in the statement of stockholders’ equity (deficit).
Income Taxes	Income Taxes Miragen 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. Miragen’s significant deferred tax assets are for net operating loss carryforwards, tax credits, and capitalized start-up costs. Miragen has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, Miragen has concluded that it is more likely than not that its deferred tax assets will not be realized. Miragen has no unrecognized tax benefits. Miragen classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations as general and administrative expenses.
Segment Information	Segment Information Miragen operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All of Miragen’s equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with its partners are denominated in U.S. dollars, except where noted.
Recent Accounting Pronouncements - Adopted and 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 (Topic 606) , which outlines 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. In March 2016, the FASB issued ASU No. 2016-08 , Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations . The purpose of this standard is to clarify the implementation of guidance on principal versus agent considerations related to ASU 2014-09. The standard has the same effective date as ASU 2014-09 described above. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customer, which provides clarity related to ASU 2014-09 regarding identifying performance obligations and licensing implementation. The standard has the same effective date as ASU 2014-09 described above. In May 2016, the FASB issued ASU 2016-12: Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which provides narrow scope improvements and practical expedients related to ASU 2014-09. The purpose of this standard is to clarify certain narrow aspects of ASU 2014-09, such as assessing the collectability criterion, presentation of sales taxes, and other similar taxes collected from customers, noncash consideration, contract modifications at transition, completed contracts at transition, and technical correction. The standard has the same effective date as ASU 2014-09 described above. In December 2016, the FASB issued ASU 2016-20: Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . The amendments in this standard affect narrow aspects of guidance issued in ASU 2014-09. The standard has the same effective date as ASU 2014-09 described above. The Company plans to adopt these new standards in the first quarter of 2019 and does not anticipate the adoption of these pronouncements to have a material impact with regard to its current contracts on its condensed consolidated financial statements. As of March 31, 2017 , there were no contracts that will be in effect (actively) as of the transition date and, accordingly, the Company has not yet determined the effect of the standard on its condensed consolidated financial statements. The Company’s selected implementation transition method will be dependent upon contracts that are in place closer to the transition date. Deferred Taxes In November 2015, the FASB issued ASU No. 2015-17 , Balance Sheet Classification of Deferred Taxes . ASU No. 2015-17 requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. This standard is effective for the Company for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods thereafter. The Company does not believe the adoption of this standard will have a material impact on its condensed consolidated financial statements due to the full valuation allowance on all net deferred tax assets. Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842), which supersedes FASB ASC Topic 840, Leases (Topic 840), which provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The standard is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods thereafter, with early adoption permitted. At adoption, this update will be applied using a modified retrospective approach. The Company currently has one lease for its primary business location that will be affected by the new standard. The Company is currently evaluating the impact of this standard on its condensed consolidated financial statements. Share-based Compensation In March 2016, the FASB issued ASU No. 2016-09 , Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which is intended to simplify accounting for equity share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. This standard is effective for the Company for annual periods beginning after December 15, 2017, and interim periods thereafter. Amendments related to the timing of when excess tax benefits are recognized, minimum statutory withholding requirements, forfeitures, and intrinsic value should be applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is adopted. Amendments related to the presentation of employee taxes paid on the statement of cash flows when an employer withholds shares to meet the minimum statutory withholding requirement should be applied retrospectively. Amendments requiring recognition of excess tax benefits and tax deficiencies in the income statement and the practical expedient for estimating the expected term should be applied prospectively. An entity may elect to apply the amendments related to the presentation of excess tax benefits on the statement of cash flows using either a prospective transition method or a retrospective transition method. The Company is currently evaluating the impact of this standard on its condensed consolidated financial statements. Other new pronouncements issued but not effective as of March 31, 2017 are not expected to have a material impact on the Company’s condensed consolidated financial statements.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis consisted of the following: March 31, 2017 December 31, 2016 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 53,898 $ — $ 22,189 $ — Liabilities: Preferred and common stock warrants (included in accrued and other liabilities) $ — $ 82 $ — $ 133
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	A reconciliation of the beginning and ending balances of Miragen’s liabilities measured at fair value using significant unobservable, or Level 3, inputs are as follows for the three months ended March 31, 2017 (in thousands): Balance of liability as of December 31, 2016 $ 133 Reclassification of preferred stock warrant to common stock warrant (51 ) Balance of liability as of March 31, 2017 $ 82

Reverse Merger (Tables)

Reverse Merger (Tables)	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	The following table summarizes the net assets acquired based on their estimated fair values as of February 13, 2017, 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)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment, net consisted of the following: March 31, December 31, (in thousands) Lab equipment $ 2,182 $ 2,163 Furniture and fixtures 51 51 Computer hardware and software 303 281 Leasehold improvements 688 688 Property and equipment, gross 3,224 3,183 Less: accumulated depreciation and amortization (2,627 ) (2,558 ) Property and equipment, net $ 597 $ 625

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2017
Payables and Accruals [Abstract]
Components of Accrued Liabilities	Accrued liabilities consisted of the following: March 31, December 31, (in thousands) Accrued outsourced clinical and preclinical studies $ 1,869 $ 1,684 Accrued employee compensation and related taxes 749 928 Accrued legal fees and expenses 636 759 Accrued professional service fees 496 124 Accrued equipment and lab materials 184 — Value of liability-classified stock purchase warrants 82 133 Deferred and accrued facility lease obligations 50 221 Accrued property and franchise taxes 37 38 Other accrued liabilities 77 22 Total accrued liabilities $ 4,180 $ 3,909

Notes Payable (Tables)

Notes Payable (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Composition of Notes Payable	Amounts outstanding under notes payable are as follows: March 31, December 31, (in thousands) Principal amount outstanding $ 4,167 $ 4,667 Unamortized debt discount (11 ) (14 ) Unamortized debt issuance costs (25 ) (31 ) Accretion of final payment fee 190 167 Total notes payable 4,321 4,789 Less: current maturities (1,974 ) (1,969 ) Long-term notes payable, net of current portion $ 2,347 $ 2,820
Future Annual Minimum Principal Payments of Notes Payable	Future annual minimum principal payments of notes payable are as follows: March 31, (in thousands) 2017 (remainder of year) $ 1,500 2018 2,000 2019 667 Total $ 4,167

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future annual minimum payments under the lease are as follows: March 31, 2017 (in thousands) 2017 (remainder of year) $ 285 2018 391 2019 404 2020 277 Total $ 1,357

Warrants (Tables)

Warrants (Tables)	3 Months Ended
	Mar. 31, 2017
Other Liabilities Disclosure [Abstract]
Summary of Warrants	Stock purchase warrant activity is as follows for the three months ended March 31, 2017 : Common Stock Warrants Preferred Stock Warrants Number Weighted Average Exercise Price Number Weighted Average Exercise Price Outstanding at December 31, 2016 7,031 $ 0.57 25,779 $ 6.21 Warrants acquired in Merger 13,534 $ 80.70 — $ — Preferred stock warrants converted into Common Stock warrants 25,779 $ 6.21 (25,779 ) $ 6.21 Cashless exercise (21,092 ) $ 3.04 — $ — Outstanding at March 31, 2017 25,252 $ 47.21 — $ — A summary of outstanding Common Stock purchase warrants as of March 31, 2017 is as follows: Common Stock Warrants Number of Underlying Shares Exercise Price Expiration Date 13,534 $80.70 2019 & 2020 11,718 $8.53 2025 25,252

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2016 2,321 $ 1.44 Granted 732 $ 11.37 Exercised (100 ) $ (0.88 ) Outstanding at March 31, 2017 2,953 $ 3.92
Restricted Stock Activity	A summary of restricted stock award (“RSA”) activity is as follows: Number of Restricted Stock Awards (in thousands) Weighted Average Grant Date Fair Value Unvested at December 31, 2016 — $ — Granted 1 $ 12.00 Unvested at March 31, 2017 1 $ 12.00
Fair Value Assumptions for Stock Options	The fair value was determined by the Black-Scholes option pricing model using the following assumptions: Three Months Ended 2017 2016 Expected term, in years 6.35 5.00 Expected volatility 84.2 % 84.0 % Risk-free interest rate 2.1 % 1.2 % Expected dividend yield — % — % Weighted average fair value of underlying Common Stock $ 11.37 $ 1.05
Allocation of Share-based Compensation Expense	Share-based compensation related to employee stock options and RSAs is included in the condensed consolidated statements of operations as follows: Three Months Ended 2017 2016 (in thousands) Research and development $ 123 $ 12 General and administrative 145 26 Total share-based compensation expense $ 268 $ 38

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Potentially dilutive securities include the following: March 31, 2017 March 31, 2016 (in thousands) Options to purchase Common Stock 2,953 2,222 Warrants to purchase Common Stock 25 7 Redeemable convertible preferred stock — 10,513 Warrants to purchase redeemable convertible preferred stock — 26 Total 2,978 12,768

Description of Business - Narra

Description of Business - Narrative (Details) $ / shares in Units, $ in Thousands	Feb. 13, 2017USD ($)$ / sharesshares	Mar. 31, 2017USD ($)$ / sharesshares	Mar. 31, 2016USD ($)	Feb. 12, 2017$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)
Description of Business [Line Items]
Common stock, shares outstanding (in shares) | shares		21,401,828			833,744
Accumulated deficit		$ (74,061)			$ (67,076)
Proceeds from the sale of common stock	$ 40,700	$ 40,703	$ 0
Common stock, par value (in dollars per share) | $ / shares		$ 0.01			$ 0.01
Cash and cash equivalents		$ 54,273	$ 16,960		$ 22,104	$ 21,235
Signal
Description of Business [Line Items]
Common stock, shares outstanding (in shares) | shares	21,309,440			1,024,960
Common stock, par value (in dollars per share) | $ / shares	$ 0.01			$ 0.001
Signal Shares issued to Miragen Common Shareholders | Signal
Description of Business [Line Items]
Exchange rate of common stock	0.7031

Summary of Significant Accoun30

Summary of Significant Accounting Policies - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Level 1
Assets:
Assets, fair value disclosure	$ 53,898	$ 22,189
Liabilities:
Liabilities, fair value disclosure	0	0
Level 3
Assets:
Assets, fair value disclosure	0	0
Liabilities:
Liabilities, fair value disclosure	$ 82	$ 133

Summary of Significant Accoun31

Summary of Significant Accounting Policies - Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 133
Reclassification of preferred stock warrant to common stock warrant	51
Ending balance	$ 82

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2017segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounting Policies [Abstract]
Impairment charges		$ 0	$ 0
Income tax penalties and interest expense		$ 0	$ 0
Number of operating segments | segment	1
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years

Strategic Alliance and Collab33

Strategic Alliance and Collaboration with Servier - Narrative (Details) € in Millions	3 Months Ended		12 Months Ended				63 Months Ended
	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2013EUR (€)	Dec. 31, 2013USD ($)	Dec. 31, 2011EUR (€)	Dec. 31, 2011USD ($)	Dec. 31, 2016EUR (€)	Dec. 31, 2016USD ($)	Mar. 31, 2017EUR (€)	Mar. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue under strategic alliance and collaboration	$ 10,000	$ 917,000
Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Nonrefundable upfront payment			€ 3	$ 4,000,000	€ 6	$ 8,400,000
Potential commercialization milestone payments									€ 175	$ 186,900,000
Revenue from research and development activities	10,000	700,000
Licenses revenue	0	200,000					€ 9	$ 12,400,000
Revenue under strategic alliance and collaboration	$ 10,000	$ 900,000
Amounts incurred but not yet billed								$ 300,000		0
Minimum | Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential development milestone payments									5.8	6,200,000
Potential regulatory milestone payments									10	10,700,000
Maximum | Servier Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential development milestone payments									13.8	14,700,000
Potential regulatory milestone payments									€ 40	$ 42,700,000

Reverse Merger - Narrative (Det

Reverse Merger - Narrative (Details) $ in Thousands	Mar. 31, 2017shares	Feb. 28, 2017	Feb. 13, 2017USD ($)shares	Feb. 12, 2017USD ($)shares	Dec. 31, 2016shares
Business Acquisition [Line Items]
Common stock, shares outstanding (in shares) | shares	21,401,828				833,744
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 Shares issued to Miragen Common Shareholders | Signal
Business Acquisition [Line Items]
Exchange rate of common stock			0.7031
Pre-Merger MIragen Stockholders, Warrantholders, and Optionholders | Signal
Business Acquisition [Line Items]
Ownership percentage			95.20%
Signal Shareholders | Signal
Business Acquisition [Line Items]
Ownership interest prior to merger			95.90%
Miragen Shareholders | Signal
Business Acquisition [Line Items]
Ownership interest prior to merger			4.10%
Preferred stock
Business Acquisition [Line Items]
Exchange rate of common stock		1		1

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	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,224	$ 3,183
Less: accumulated depreciation and amortization	(2,627)	(2,558)
Property and equipment, net	597	625
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,182	2,163
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	51	51
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment	303	281
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 688	$ 688

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 73	$ 81

Accrued Liabilities - Component

Accrued Liabilities - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued outsourced clinical and preclinical studies	$ 1,869	$ 1,684
Accrued employee compensation and related taxes	749	928
Accrued legal fees and expenses	636	759
Accrued professional service fees	496	124
Accrued equipment and lab materials	184	0
Value of liability-classified stock purchase warrants	82	133
Deferred and accrued facility lease obligations	50	221
Accrued property and franchise taxes	37	38
Other accrued liabilities	77	22
Total accrued liabilities	$ 4,180	$ 3,909

Notes Payable - Narrative (Deta

Notes Payable - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2015USD ($)	Apr. 30, 2015USD ($)tranche$ / sharesshares	Mar. 31, 2017USD ($)	Dec. 31, 2016
Detachable Warrants - Series B Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Potential repurchase of outstanding warrants			$ 0.1
2015 Notes Payable to Silicon Valley Bank - Tranche One | Detachable Warrants - Series B Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Shares eligible for purchase under warrants (in shares) | shares		11,718
Warrant exercise price (in usd per share) | $ / shares		$ 8.53
Fair value of warrants		$ 0.1
Warrants Not Settleable in Cash | Income Approach Valuation Technique | Detachable Warrants - Series B Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Expected term		2 years
Discount rate		5.00%
Probability of exercise		90.00%
Notes Payable to Banks | Silicon Valley Bank Agreement
Debt Instrument [Line Items]
Face amount		$ 10
Number of tranches | tranche		2
Notes Payable to Banks | 2015 Notes Payable to Silicon Valley Bank - Tranche One
Debt Instrument [Line Items]
Face amount	$ 5
Repayment period	30 months
Interest-only period	18 months
Notes Payable to Banks | 2015 Notes Payable to Silicon Valley Bank - Tranche Two
Debt Instrument [Line Items]
Face amount	$ 5
Notes Payable to Banks | Prime Rate | 2015 Notes Payable to Silicon Valley Bank - Tranche One
Debt Instrument [Line Items]
Variable rate		0.25%
Interest rate at period end				3.75%
Final payment fee percent				5.50%

Notes Payable - Composition of

Notes Payable - Composition of Notes Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Principal amount outstanding	$ 4,167	$ 4,667
Unamortized debt discount	(11)	(14)
Unamortized debt issuance costs	(25)	(31)
Accretion of final payment fee	190	167
Total	4,321	4,789
Less: current maturities	(1,974)	(1,969)
Long-term notes payable, net of current portion	$ 2,347	$ 2,820

Notes Payable - Future Annual M

Notes Payable - Future Annual Minimum Principal Payments (Details) $ in Thousands	Mar. 31, 2017USD ($)
Debt Disclosure [Abstract]
2017 (remainder of year)	$ 1,500
2,018	2,000
2,019	667
Total	$ 4,167

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) € in Thousands	1 Months Ended		3 Months Ended		30 Months Ended
	Oct. 31, 2010EUR (€)	Oct. 31, 2010USD ($)	Mar. 31, 2017USD ($)arrangementshares	Mar. 31, 2016USD ($)	Mar. 31, 2017USD ($)arrangement
Commitments and Contingencies [Line Items]
Rent expense			$ 100,000	$ 100,000
Operating expenses of leases			$ 100,000	100,000
University of Texas
Commitments and Contingencies [Line Items]
Number of arrangements | arrangement			5		5
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
RICC
Commitments and Contingencies [Line Items]
Payments for the grant of license and option			2,300,000
Potential future milestone payments per licensed product			5,200,000		5,200,000
Payments for raw materials			400,000	$ 0
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
BWH
Commitments and Contingencies [Line Items]
Potential milestone payments			$ 2,600,000
One-time sales milestone payment			300,000
United States | University of Texas
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			2,000,000		2,000,000
United States | t2cure
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			2,500,000		2,500,000
Other Regions | University of Texas
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			500,000		500,000
European Union or Japan
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			$ 1,500,000		1,500,000
Series A | RICC
Commitments and Contingencies [Line Items]
Shares issued in agreement (in shares) | shares			856,806
Shares issued in conversion (in shares) | shares			602,420
Yale University
Commitments and Contingencies [Line Items]
Potential cash proceeds from agreement			$ 1,100,000		1,100,000
Term of agreement			5 years
Proceeds from arrangement					$ 33,000

Commitments and Contingencies43

Commitments and Contingencies - Future Minimum Rental Payments (Details) $ in Thousands	Mar. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,017	$ 285
2,018	391
2,019	404
2,020	277
Total	$ 1,357

Capital Stock - Narrative (Deta

Capital Stock - Narrative (Details) $ / shares in Units, $ in Thousands	Feb. 13, 2017USD ($)$ / sharesshares	Mar. 31, 2017USD ($)$ / sharesshares	Mar. 31, 2016USD ($)	Feb. 28, 2017	Feb. 12, 2017$ / shares	Dec. 31, 2016$ / sharesshares
Class of Stock [Line Items]
Shares authorized (in shares) | shares		105,000,000
Common stock, shares authorized (in shares) | shares		100,000,000				100,000,000
Preferred stock, shares authorized (in shares) | shares		5,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.01				$ 0.01
Preferred stock, par value (in usd per share) | $ / shares		$ 0.01
Proceeds from the sale of common stock | $	$ 40,700	$ 40,703	$ 0
Payments of stock issuance costs | $	$ 1,500	1,176	$ 0
Preferred stock
Class of Stock [Line Items]
Exchange rate of common stock				1	1
Signal
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.01				$ 0.001
Signal Shares issued to Miragen Common Shareholders | Signal
Class of Stock [Line Items]
Exchange rate of common stock	0.7031
Pre-Merger
Class of Stock [Line Items]
Sale of common stock to investors (in shares) | shares	9,045,126
Sale of Stock, Price Per Share | $ / shares	$ 4.50
Post-Merger
Class of Stock [Line Items]
Sale of common stock to investors (in shares) | shares	6,359,628
Sale of Stock, Price Per Share | $ / shares	$ 6.40
ATM Agreement
Class of Stock [Line Items]
Aggregate offering | $		$ 50,000
Commission fee percent		3.00%

Warrants - Stock Warrant Activi

Warrants - Stock Warrant Activity (Details)	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Common Stock Warrants
Number
Beginning balance (in shares) | shares	7,031
Warrants acquired in Merger (in shares) | shares	13,534
Preferred stock warrants converted into common stock warrants (in shares) | shares	25,779
Cashless exercise (in shares) | shares	(21,092)
Ending balance (in shares) | shares	25,252
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 0.57
Warrants acquired in Merger (in usd per share) | $ / shares	80.70
Preferred stock warrants converted into common stock warrants (in usd per share) | $ / shares	6.21
Cashless exercise (in usd per share) | $ / shares	3.04
Ending balance (in usd per share) | $ / shares	$ 47.21
Preferred Stock Warrants
Number
Beginning balance (in shares) | shares	25,779
Warrants acquired in Merger (in shares) | shares	0
Preferred stock warrants converted into common stock warrants (in shares) | shares	(25,779)
Cashless exercise (in shares) | shares	0
Ending balance (in shares) | shares	0
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 6.21
Warrants acquired in Merger (in usd per share) | $ / shares	0
Preferred stock warrants converted into common stock warrants (in usd per share) | $ / shares	6.21
Cashless exercise (in usd per share) | $ / shares	0
Ending balance (in usd per share) | $ / shares	$ 0

Warrants - Stock Warrants Outst

Warrants - Stock Warrants Outstanding (Details) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Common Stock Warrants
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	25,252
Exercise price (in usd per share)	$ 47.21	$ 0.57
Expiration Date 2019 and 2020
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	13,534
Exercise price (in usd per share)	$ 80.70
Expiration Date 2025
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	11,718
Exercise price (in usd per share)	$ 8.53

Warrants - Narrative (Details)

Warrants - Narrative (Details) - Common Stock Warrants	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Class of Warrant or Right [Line Items]
Warrants acquired in Merger (in shares) | shares	13,534
Warrants acquired in Merger (in usd per share) | $ / shares	$ 80.70

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized employee stock-based compensation costs	$ 7,000,000
Remaining weighted-average period for RSUs	3 years 8 months 33 days
Stock-based compensation expense	$ 268,000	$ 38,000
Options to purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	2,953,000		2,321,000
Expiration period	10 years
Weighted average fair value per option (in usd per share)	$ 8.30	$ 0.70
Shares issued in period (in shares)	732,000
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 | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	9 months
Options to purchase Common Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	48 months
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of RSAs (in usd per share)	$ 0
Total grant date fair value of RSAs	$ 0
Granted (in shares)	1,000	0
Remaining weighted average period for RSAs	6 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	$ 9,000
Non-employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense for non-employees	$ 100,000
Weighted-average remaining period for recognition of non-employee stock-based compensation expense	1 year 5 months 13 days
Non-employees | Non-employee Stock Option
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)	2,235,779
2016 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance (in shares)	4,182,404
Basis for equity incentive plan (in shares)	1,681,294
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 145,000	$ 26,000
General and administrative | Non-employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 151,000	$ 4,000

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - Options to purchase Common Stock - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Number of Options (in thousands)
Beginning balance (in shares)	2,321
Granted (in shares)	732
Exercised (in shares)	(100)
Ending balance (in shares)	2,953
Weighted Average Exercise Price
Beginning balance (in usd per share)	$ 1.44
Granted (in usd per share)	11.37	$ 1.05
Exercised (in usd per share)	(0.88)
Ending balance (in usd per share)	$ 3.92

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Number of Restricted Stock Awards (in thousands)
Beginning balance (in shares)	0
Granted (in shares)	1,000	0
Ending balance (in shares)	1,000
Weighted Average Grant Date Fair Value
Beginning balance (in usd per share)	$ 0
Granted (in usd per share)	12
Ending balance (in usd per share)	$ 12

Share-Based Compensation - Fair

Share-Based Compensation - Fair Value Assumption for Stock Options (Details) - Options to purchase Common Stock - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term, in years	6 years 4 months 6 days	5 years
Expected volatility	84.20%	84.00%
Risk-free interest rate	2.10%	1.20%
Expected dividend yield	0.00%	0.00%
Weighted average fair value of underlying common stock (in usd per share)	$ 11.37	$ 1.05

Share-Based Compensation - Allo

Share-Based Compensation - Allocation of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 268	$ 38
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	123	12
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 145	$ 26

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)		2,978	12,768
Options to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)		2,953	2,222
Warrants to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)		25	7
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	10,513	0
Warrants to purchase redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)		0	26