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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Nov. 07, 2016
Document and Entity Information
Entity Registrant Name	Mirna Therapeutics, Inc.
Entity Central Index Key	0001527599
Document Type	10-Q
Document Period End Date	Sep. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		20,835,868
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 26,958	$ 89,713
Short-term marketable securities	39,300	0
Prepaid expenses and other current assets	818	829
Total current assets	67,076	90,542
Property and equipment, net	1,834	375
Long-term marketable securities	400	0
Restricted cash	2,431	0
Total assets	71,741	90,917
Current Liabilities:
Accounts payable	1,153	3,687
Accrued expenses	1,943	2,214
Total liabilities	3,096	5,901
Stockholders’ Equity (Deficit):
Preferred stock, $0.001 par value, 5,000,000 shares authorized at September 30, 2016 and December 31, 2015; 0 shares outstanding at September 30, 2016 and December 31, 2015	0	0
Common stock, $0.001 par value; 250,000,000 shares authorized at September 30, 2016 and December 31, 2015; 20,835,868 and 20,830,555 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	21	21
Additional paid in capital	162,729	161,518
Accumulated other comprehensive loss	(8)	0
Accumulated deficit	(94,097)	(76,523)
Total stockholders’ equity	68,645	85,016
Total liabilities and stockholders’ equity	$ 71,741	$ 90,917

Condensed Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	20,835,868	20,830,555
Common stock, shares outstanding (in shares)	20,835,868	20,830,555

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development	$ 3,384	$ 4,683	$ 11,589	$ 12,584
General and administrative	1,940	1,556	6,119	3,618
Total operating expenses	5,324	6,239	17,708	16,202
Other income (expense):
Interest income	97	8	272	8
Loss on disposal of assets	(138)	0	(138)	0
Total other income (expense)	(41)	8	134	8
Net loss	(5,365)	(6,231)	(17,574)	(16,194)
Less: Accretion and dividends on convertible preferred stock	0	(1,554)	0	(4,217)
Net loss attributable to common stockholders—basic and diluted	(5,365)	(7,785)	(17,574)	(20,411)
Other comprehensive loss:
Unrealized loss on available for sale securities, net of tax	(14)	0	(8)	0
Total other comprehensive loss	$ (5,379)	$ (7,785)	$ (17,582)	$ (20,411)
Net loss per share attributable to common stockholders—basic and diluted (in USD per share)	$ (0.26)	$ (82.16)	$ (0.84)	$ (222.70)
Common shares used to compute basic and diluted net loss per share attributable to common stockholders (in shares)	20,835,868	94,753	20,832,727	91,650

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities
Net loss	$ (17,574)	$ (16,194)
Adjustment to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	105	37
Stock-based compensation	1,202	561
Net amortization of premium/ discounts on marketable securities	178	0
Changes in operating assets and liabilities:
Grant reimbursement and other receivables	(123)	61
Prepaid expenses and other assets	134	(217)
Accounts payable	(2,883)	1,290
Accrued expenses	(271)	(57)
Net cash used in operating activities	(19,232)	(14,519)
Investing activities
Purchases of marketable securities	(79,786)	0
Maturities of marketable securities	39,900	0
Restricted cash	(2,431)	0
Purchases of property and equipment	(1,215)	(187)
Net cash used in investing activities	(43,532)	(187)
Financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	41,023
Proceeds from the exercise of stock options	9	67
Cash provided by financing activities	9	41,090
Net increase (decrease) in cash and cash equivalents	(62,755)	26,384
Cash and cash equivalents at beginning of period	89,713	9,319
Cash and cash equivalents at end of period	26,958	35,703
Supplemental disclosures for non- cash investing activities:
Property & equipment purchased in accounts payable	$ 412	$ 0

Nature of Business and Basis of Presentation	9 Months Ended
Nature of Business and Basis of Presentation	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Nature of Business and Basis of Presentation Nature of business Mirna Therapeutics, Inc. (“Mirna” or “the Company”) is a biopharmaceutical company focused on microRNA-based oncology therapeutics. The Company was incorporated in Delaware in December 2007 as a wholly‑owned subsidiary of Asuragen, Inc. (“Asuragen”) and was spun out to existing Asuragen stockholders in December 2009. Following the close of the Company's Phase 1 clinical trial of MRX34 in September 2016, the Company is evaluating its strategic alternatives focusing on enhancing stockholder value, including the possibility of a merger or sale of the Company, and has suspended further research and development activities to reduce operating expenses while it evaluates these opportunities (see Note 13 for additional discussion.) The Company is located in Austin, Texas. In October 2015, the Company sold 6,250,000 shares of common stock, $0.001 par value per share, in an underwritten public offering (the “IPO”) and 2,395,010 shares of common stock in a concurrent private placement, with both offerings at a price of $7.00 per share. The underwriters of the IPO purchased an additional 704,962 shares of common stock pursuant to their option to purchase additional shares. The Company’s aggregate net proceeds from the IPO were $43.7 million, after deducting the transaction offering costs and the underwriting discounts incurred. The Company also received net proceeds of $16.7 million after deducting the offering transaction costs from the concurrent private placement. The Company continues to be subject to a number of risks common to companies in similar stages of development. Principal among these risks are uncertainties of technological innovations, dependence on key individuals, development of the same or similar technological innovations by the Company’s competitors and protection of proprietary technology. The Company believes that its cash, cash equivalents and marketable securities of $66.7 million at September 30, 2016 will enable the Company to maintain its current and planned operations for at least the next twelve months. Basis of presentation The accompanying interim condensed financial statements as of September 30, 2016 and for the three and nine months ended September 30, 2016 and 2015, and the related interim information contained within the notes to the financial statements, are unaudited. The unaudited interim condensed financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and on the same basis as the audited financial statements. In the opinion of management, the accompanying unaudited interim condensed financial statements contain all adjustments which include only normal recurring adjustments necessary to state fairly the Company’s financial position as of September 30, 2016, and the results of its operations and cash flows for the interim periods ended September 30, 2016 and 2015. Such adjustments are of a normal and recurring nature. The interim financial data as of September 30, 2016 is not necessarily indicative of the results to be expected for the year ending December 31, 2016, or for any future period. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and related notes thereto for the year ended December 31, 2015 included in the Company’s Form 10-K, most recently filed with the Securities and Exchange Commission on March 30, 2016.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2016

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Use of estimates

The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires the Company’s management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Research and development costs

Research and development costs are expensed as incurred. Research and development costs include salaries and personnel‑related costs, consulting fees, fees paid for contract research services, the costs of laboratory equipment and facilities, development of intellectual property, license fees and other external costs. The Company accounts for government grants as a reduction of research and development expenses. Government grants are recorded at the time the related research and development costs have been incurred by the Company and, accordingly, become eligible for reimbursement. The Company accrues for government grants that have been earned but not yet received.

Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed.

Clinical Trial and Pre-Clinical Study Accruals

The Company estimates pre-clinical study and clinical trial expenses pursuant to contracts with research institutions and contract research organizations that conduct and manage pre-clinical studies and clinical trials on the Company’s behalf. These estimates are based on the level of service performed and the underlying agreement. Further, the Company accrues expenses related to clinical trials based on the level of patient enrollment and other activities according to the related agreements. The Company monitors patient enrollment levels and other activities to the extent reasonably possible and adjusts estimates accordingly. If actual costs incurred or the timing of services vary from our estimate, we adjust the accrual accordingly.

Stock‑based compensation

The Company accounts for its stock‑based compensation awards in accordance with ASC Topic 718, Compensation—Stock Compensation (“ASC 718”). ASC 718 requires all stock‑based payments to employees, including grants of employee stock options, to be recognized in the statements of operations based on their grant date fair values. For stock options granted to employees and to members of the board of directors for their services on the board of directors, the Company estimates the grant date fair value of each option award using the Black‑Scholes option‑pricing model. The use of the Black‑Scholes option‑pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk‑free interest rates and expected dividend yields of the common stock. For awards subject to service‑based vesting conditions, the Company recognizes stock‑based compensation expense, net of estimated forfeitures, equal to the grant date fair value of stock options on a straight‑line basis over the requisite service period.

Fair value measurements

The Company records money market funds at fair value. ASC Topic 820, Fair Value Measurements and Disclosures, establishes a fair value hierarchy for those instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). The hierarchy consists of three levels:


•	Level 1 – Unadjusted prices in active markets for identical assets or liabilities.


•	Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability.


•	Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date.

The carrying amounts reflected in the balance sheets for cash, prepaid expenses and other current assets, accounts payable, and accrued expenses approximate their fair values at September 30, 2016 and December 31, 2015, due to their short‑term nature.

The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1, Level 2 or Level 3 during the three or nine months ended September 30, 2016 or 2015.

Restricted Cash

Restricted cash consists of cash amounts held for specific or limited purposes and, therefore, not available for general operating activities. In June 2016, the Company secured a standby letter of credit of $2.4 million for the benefit of the landlord in the event of default. The restricted cash consists of cash providing security under the terms of the lease described in Note 11.

Marketable Securities

The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Marketable securities with a remaining maturity date greater than one year are classified as non-current. Available-for-sale securities are maintained by an investment manager and may consist of U.S. Treasury securities and government agency securities and corporate debt securities. Available-for-sale securities are carried at fair value with the unrealized gains and losses included in other comprehensive loss as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included in other income.

If any adjustment to fair value reflects a decline in value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other-than-temporary” and, if so, mark the investment to market through a charge to the Company’s statement of operations and comprehensive loss.

Comprehensive loss

Comprehensive loss is composed of net loss and other comprehensive income or loss. Other comprehensive loss consists of unrealized gains and losses on marketable securities.

Recently Issued Accounting Pronouncements

In March 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share Based Payment Accounting ("ASU 2016-09") as part of the FASB simplification initiative. The new standard provides for changes to accounting for stock compensation including 1) excess tax benefits and tax deficiencies related to share-based payment awards will be recognized as income tax expense in the reporting period in which they occur; 2) excess tax benefits will be classified as an operating activity in the statement of cash flow; 3) the option to elect to estimate forfeitures or account for them when they occur; and 4) increase tax withholding requirements threshold to qualify for equity classification. The ASU is effective for public companies for annual periods, and interim periods within those annual periods, beginning after December 15, 2016, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2016-09 will have on the financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The new standard requires the recognition of assets and liabilities arising from lease transactions on the balance sheet and the disclosure of key information about leasing arrangements. Accordingly, a lessee will recognize a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. Both the asset and liability will initially be measured at the present value of the future minimum lease payments over the lease term. Subsequent measurement, including the presentation of expenses and cash flows, will depend on the classification of the lease as either a finance or an operating lease. Initial costs directly attributable to negotiating and arranging the lease will be included in the asset. For leases with a term of twelve months or less, a lessee can make an accounting policy election by class of underlying asset to not recognize an asset and corresponding liability. Lessees will also be required to provide additional qualitative and quantitative disclosures regarding the amount, timing and uncertainty of cash flows arising from leases. These disclosures are intended to supplement the amounts recorded in the financial statements and provide additional information about the nature of an organization’s leasing activities. The new standard is effective for fiscal years beginning after December 15, 2018, and interim periods within those years, with early adoption permitted. In transition, lessees are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The transition guidance also provides specific guidance for sale and leaseback transactions, build-to-suit leases and amounts previously recognized in accordance with the business combinations guidance for leases. We are currently evaluating our expected adoption method and the impact of this new standard on the financial statements.

Marketable Securities

9 Months Ended

Sep. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

The following table summarizes the available-for-sale securities held at September 30, 2016 (in thousands):



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
September 30, 2016
U.S. government agency securities and treasuries	$	25,013	$	7	$	(3	)	$	25,017
Corporate debt securities	14,695		—		(12		)	14,683
Total available-for-sale securities	$	39,708	$	7	$	(15	)	$	39,700

The Company did not have available for sale securities at December 31, 2015. Approximately $400,000 in available- for- sale securities held as of September 30, 2016 had remaining maturities greater than one year.

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Fair Value Measurements

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following table sets forth the Company’s assets that are measured at fair value on a recurring basis as of September 30, 2016 and December 31, 2015 (in thousands):



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
September 30, 2016
Assets:
Cash and Cash Equivalents
Money market funds	$	23,805	$	23,805	$	—	$	—
US government agency securities and treasuries	$	1,353	—		1,353
Corporate debt securities	1,800		—		1,800		—
Total cash and cash equivalents	26,958		23,805		3,153		—
Marketable securities
U.S. government agency securities and treasuries	24,617		—		24,617		—
Corporate debt securities	14,683		—		14,683		—
Total marketable securities	39,300		—		39,300		—
U.S. government agency securities and treasuries, long-term	400		—		400		—
Restricted cash	2,431		2,431		—		—
Total assets	$	69,089	$	26,236	$	42,853	$	—

December 31, 2015
Assets:
Money Market Funds	89,713		89,713		—		—
Total Assets	$	89,713	$	89,713	$	—	$	—

Cash and cash equivalents

The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. As of September 30, 2016 and December 31, 2015, cash and cash equivalents are comprised of money market accounts, U.S. government agency securities and corporate debt securities.

Marketable securities

The cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At September 30, 2016 and December 31, 2015, the balance in the Company’s accumulated other comprehensive loss was composed solely of activity related to the Company’s available-for-sale marketable securities. The Company has not realized material gains or losses on sales of available-for-sale investment securities during any of the periods presented.

As of September 30, 2016, available for sale securities of approximately $22.9 million were in an unrealized loss position of $15,000. The Company has the intent and ability to hold such securities until recovery. The Company determined that there were no material changes in the credit risk of the above investments. The Company did not hold any investments with an other-than-temporary impairment as of September 30, 2016 and December 31, 2015.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment

9 Months Ended

Sep. 30, 2016

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment consisted of the following (in thousands):



	September 30, 2016			December 31, 2015
Construction in Progress	$	598		$	—
Furniture, computers and equipment	1,540			687
Leasehold improvements	36			18
Accumulated depreciation	(340		)	(330		)
	$	1,834		$	375

Depreciation expense was approximately $60,000 and $12,000 for the three months ended September 30, 2016 and 2015, respectively. Depreciation expense was approximately $105,000 and $37,000 for the nine months ended September 30, 2016 and 2015, respectively.

Common Stock

9 Months Ended

Sep. 30, 2016

Stockholders' Equity Note [Abstract]

Common Stock

The Company’s common stock has the following characteristics:


•	The holders of shares of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders.


•	The holders of shares of common stock are entitled to receive dividends, if and when declared by the Company’s board of directors. Since inception, no cash dividends have been declared.

Offerings

In September 2015, the Company entered into a new grant contract with Cancer Prevention and Research Institute of Texas (“CPRIT”), in connection with an award of approximately $16.8 million. The 2015 award was in the form of an agreement by CPRIT to purchase $16.8 million of shares of common stock of the Company in a private placement concurrent with the initial public offering of the Company’s common stock. On October 5, 2015, CPRIT purchased 2,395,010 shares of the Company’s common stock at $7.00 per share. Net proceeds from the private placement, after related transaction offering costs, were approximately $16.6 million.

In October 2015, the Company issued 6.25 million shares of common stock in an underwritten public offering, with a price of $7.00 per share. The underwriters purchased an additional 704,962 shares of common stock pursuant to their option to purchase additional shares. The Company received aggregate net proceeds of approximately $43.7 million in the public offering, after deducting the underwriting discounts and commissions and estimated offering expenses payable by the Company.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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+ Details

Stock Option Plans

9 Months Ended

Sep. 30, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Option Plans

2008 Long Term Incentive Plan

During 2008, the Company adopted the 2008 Long Term Incentive Plan, which allows for incentive stock options for its employees and nonqualified stock options (inclusive of restricted stock units and stock appreciation rights) (the “2008 Plan”) for employees and nonemployees under which an aggregate of 330,582 stock options and stock purchase rights may be granted. In December 2013, the total amount available for grant under the 2008 Plan was increased by 224,200 to 554,782. In March 2014, the Company’s board of directors approved an increase of 115,153 shares available for grant pursuant to the 2008 Plan to 669,935. In March 2015, the total amount of available to grant under the 2008 Plan was increased in conjunction with the Company’s offering of Series D preferred stock by 391,650 shares to 1,061,585. Options under the 2008 Plan have a maximum life of 10 years from the date of grant. Options vest at various intervals, as determined by the Company’s board of directors at the date of grant.

2015 Equity Incentive Plan

In August 2015, the Company’s board of directors approved the 2015 Equity Incentive Award Plan (the “2015 Plan”), which was effective in connection with the pricing of the IPO on September 30, 2015. The 2015 Plan provides for the granting of a variety of stock‑based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, deferred stock awards, dividend equivalent awards, stock payment awards, performance awards and other stock‑based awards. The 2015 Plan is the successor to the 2008 Plan and the 764,928 options outstanding in the 2008 Plan at September 30, 2016 may be transferred to the 2015 Plan if awards thereunder terminate, expire or lapse for any reason without the delivery of shares to the holder thereof. Under the 2015 Plan, 1,671,800 shares of the Company’s common stock were initially authorized and reserved for issuance. In March 2016, the Company’s board of directors approved an increase of 1,041,527 shares available for grant pursuant to the 2015 Plan. A combined total of 3,508,492 shares have been authorized and reserved for issuance under the 2008 Plan and 2015 Plan at September 30, 2016.

2015 Employee Stock Purchase Plan

In August 2015, the Company’s board of directors approved the 2015 Employee Stock Purchase Plan (the “ESPP”), which was effective in connection with the pricing of the IPO on September 30, 2015. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP generally provides for set offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. There were no sales under the ESPP as of September 30, 2016. Shares available for future purchase under the ESPP were 375,485 at September 30, 2016.

Stock Option Activity

The Company’s stock option activity for the nine months ended September 30, 2016 was as follows:



			Weighted‑
			Average		Weighted‑Average
	Number		Exercise		Contractual
	of Shares		Price		Life (years)
Outstanding at December 31, 2015	1,529,459		6.29		9.00
Granted	928,250		4.41
Exercised	(5,313	)	1.65
Forfeited/canceled	(350,432	)	6.85
Outstanding at September 30, 2016	2,101,964		$	5.37	8.65
Options exercisable at September 30, 2016	646,142		$	5.33	7.40

Stock Compensation Expense

Total stock-based compensation expense for the three and nine months ended September 30, 2016 was recognized as follows in the statements of comprehensive loss (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development expense	$	155	$	57	$	261	$	137
General and administrative expense	358		153		941		424
Total stock based compensation	$	513	$	210	$	1,202	$	561

As of September 30, 2016, there was approximately $5.1 million of unrecognized compensation cost related to the stock options granted under the 2015 Plan, which is expected to be amortized over a weighted-average period of 2.9 years. There were no restricted stock units or stock appreciation rights granted under the 2015 Plan as of September 30, 2016.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company has not recorded a provision for income taxes as of September 30, 2016 due to reported net losses since inception. During the three and nine months ended September 30, 2016 and 2015, the Company had no interest and penalties related to income taxes. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company has established a valuation allowance due to uncertainties regarding the realization of deferred tax assets based upon the Company’s lack of earnings history. The Company files income tax returns in the U.S. federal and Texas jurisdictions. The statute of limitations for assessment by the Internal Revenue Service (“IRS”) is open for tax years ending December 31, 2015, 2014, and 2013, although carryforward attributes that were generated for tax years prior to 2013 may still be adjusted upon examination by the IRS if they either have been, or will be, used in a future period. The 2010 and subsequent tax years remain open and subject to examination by the State of Texas. There are currently no federal or state income tax audits in progress.

Agreements with Asuragen	9 Months Ended
Agreements with Asuragen	Sep. 30, 2016
Related Party Transactions [Abstract]
Agreements with Asuragen	Agreements with Asuragen On November 3, 2009, the Company entered into an agreement with Asuragen under which Asuragen shares space with and provides services to the Company in support of the Company’s business. Such services have included human resources, finance and accounting, information technology, purchasing, shipping and receiving, equipment use, and various facility expenses. The Company paid Asuragen a monthly service fee for the services provided by Asuragen to the Company, which does not include direct charges incurred by Asuragen on behalf of the Company. Total expenses under the Shared Services Agreement with Asuragen totaled approximately $79,000 and $100,000 for the three months ended September 30, 2016 and 2015, respectively and $316,000 and $295,000 for the nine months ended September 30, 2016 and 2015. On October 31, 2014, the Company entered into a sublease agreement with Asuragen for use of office, laboratory and shared space. Total rent expense was approximately $15,000 and $59,000 for the three and nine months ended September 30, 2016. Both the lease and the shared service agreements expired on August 31, 2016. The Company has entered into a new lease for additional space, as discussed in Note 11.

License Agreements	9 Months Ended
License Agreements	Sep. 30, 2016
License Agreements
License agreements	License agreements Rosetta Genomics Ltd. In December 2015, the Company entered into a Patent License Agreement (the “License Agreement”) with Rosetta Genomics Ltd. (“Rosetta”), licensing to the Company certain patents owned or controlled by Rosetta as specified in the License Agreement. Under the License Agreement, Rosetta granted the Company a non-assignable, non- transferable, worldwide license for certain patents in connection with the development and commercialization of products that relate to the tumor suppressor microRNA MIR-34 (“Products”). This license is exclusive with respect to Products that relate to MRX34, which has been placed on full clinical hold by the Food and Drug Administration ("FDA"), and non-exclusive for products that are not related to MRX34. Under the License Agreement, the Company paid Rosetta an up-front, non-refundable payment of $1.6 million, which was accrued as an expense within research and development at December 31, 2015 and subsequently paid in January 2016. The Company is obligated to pay low single- digit royalties on net sales of Products, as well as royalties on sublicense revenues. Certain development and regulatory milestone payments totaling $3 million may also be payable in connection with specified types of Products, upon the achievement of certain development and/ or regulatory milestone events. Marina Biotech, Inc. In December 2011, the Company entered into a licensing agreement with Marina Biotech, Inc. (“Marina”), pursuant to which Marina granted to the Company a license to liposomal delivery technology, NOV340, known under the brand name “SMARTICLES,” to develop and commercialize drug products incorporating Marina’s delivery system exclusively in combination with the Company’s first therapeutic product, MRX34, which has been placed on full clinical hold by the FDA. In December 2013, the license agreement was amended to include three additional specific microRNA mimics selected by the Company to use with SMARTICLES on an exclusive basis, and in May 2015, the license agreement was further amended to reduce the amount of a specific milestone payment and to provide for the prepayment of such milestone payment. In August 2015, the Company also entered into a side letter to the license agreement, under which it exercised its right to select an additional specific microRNA as a licensed product, in exchange for the payment of a specified selection fee payment. The Company has cumulatively paid Marina approximately $2.1 million through September 30, 2016 in up‑front and milestone payments and as consideration for the inclusion within the license of four additional microRNA compounds. As the Company progresses with respect to development and commercialization of its products, the Company will be required to make payments to Marina based upon the achievement of certain development and regulatory milestones, totaling up to $6 million in the aggregate for each licensed product. The Company has agreed to pay up to an additional $4 million per licensed product upon the achievement of certain regulatory milestones for a specified number of additional indications, leading to a maximum cap on all milestone payments of $10 million per product. The exception to this is for the Company’s first therapeutic product candidate, MRX34, where the aggregate of all remaining development and regulatory milestone payments due to Marina, including for all additional indications, is $4.0 million. In addition to milestone payments, the Company will be required to pay low single digit royalties on net sales of licensed products other than MRX34, subject to customary reductions and offsets. As a result of the Company’s 2013 amendment to the agreement with Marina, the Company is no longer required to pay a royalty to Marina with respect to sales of the Company’s first therapeutic product candidate, MRX34. If the Company sublicenses its rights under the license from Marina, for each optioned microRNA compound covered by such sublicense the Company is required to pay a specified lump‑sum payment representing the remainder of the selection fee for the inclusion of such microRNA compound within the scope of the license agreement, as well as a portion of any revenue the Company receives from such sublicensees at a tiered percentage between the very low single digits and the mid‑teens, depending on the circumstances in which the sublicense is entered into. Yale University In 2006, Asuragen entered into an exclusive license agreement with Yale University (“Yale”) under certain patent rights relating to microRNAs. This agreement was assigned to the Company by Asuragen in connection with the Company’s acquisition of certain assets, including patent rights, in 2009. In February 2014, the Company as successor‑in‑interest to Asuragen, amended and restated the exclusive license agreement. Some of the patent filings in the Company’s intellectual property portfolio that are licensed to the Company by Asuragen are also included in the patents licensed under the agreement with Yale. The Company will be required to pay royalties to Yale on net sales of licensed products that contain specified microRNAs, at a percentage ranging from the very low to the low single digits, subject to customary reductions and offsets. The Company will also be required to pay to Yale a portion of specified gross revenue that the Company receives from the Company’s sublicensees at a percentage in the mid‑single digits. The Company will be required to make payments for achievement of certain development and regulatory milestones by products containing one specified microRNA and covered by the licensed patents, of up to $600,000 in the aggregate for each such product, subject to reduction in certain circumstances. In addition, the Company is required to pay an annual license maintenance fee and minimum annual royalties under certain circumstances. As of September 2016, the Company has suspended all research and development activities.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2016

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Lease

In June 2016, the Company entered into a lease for its corporate headquarters and research facility in Austin, Texas (the “Headquarters”) under an operating lease agreement (the “Lease”). The agreement provides that the lease will commence on the earlier of (i) the date on which the Company first conducts any business in the new Headquarters, (ii) substantial completion of the improvements made to the new Headquarters as defined in the Lease, or (iii) January 1, 2017 (collectively, the “Commencement Date”). The initial term of the lease is for a 123 month period, with the option to extend the lease for up to two consecutive 60 month terms. Rent expense under the Lease for the three and nine months ended September 30, 2016 was approximately $55,000.

The lease provides annual base rent of approximately $600,000 in the first year after a three-month rent free period following the Commencement Date, with subsequent annual increases of approximately 3% in the annual base rent. In connection with the lease, the landlord has provided a tenant improvement allowance of approximately $1.9 million to be used by the Company to build-out certain improvements to the Headquarters. The Lease also provides for an additional improvement allowance of up to $1.3 million. The additional allowance, if exercised, will amortize over 120 months on a straight line basis. There have been no draws on the additional improvement allowance as of September 30, 2016.

Mirna has obtained a standby letter of credit for the initial amount of approximately $2.4 million, which may be drawn down by the landlord in the event of default. If Mirna meets certain requirements, the amount due under the Letter of Credit may be reduced to approximately $800,000.

Under the Lease agreement, future minimum payments payable are approximately as follows:



		Operating
Period ending December 31,		Lease
2016	(three months)	—
2017		$	450,929
2018		614,855
2019		633,364
2020	and thereafter	5,218,227
Total		$	6,917,375

Net Loss Per Share Attributable to Common Stockholders

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except share and per share data):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Net loss	$	(5,365	)	$	(6,231	)	$	(17,574	)	$	(16,194	)
Accretion of convertible preferred stock to redemption value	—			—			—			(448		)
Accrued dividends on convertible preferred stock	—			(1,554		)	—			(3,769		)
Net loss attributable to common stockholders—basic and diluted	(5,365		)	(7,785		)	(17,574		)	(20,411		)
Weighted-average number of common shares—basic and diluted	20,835,868			94,753			20,832,727			91,650
Net loss per share attributable to common stockholders—basic and diluted	$	(0.26	)	$	(82.16	)	$	(0.84	)	$	(222.70	)

The following potentially dilutive securities outstanding, prior to the use of the treasury stock method or if‑converted method, have been excluded from the computation of diluted weighted‑average common shares outstanding, because including them would have had an anti‑dilutive effect due to the losses reported.



	September 30,
	2016	2015
Convertible preferred stock	—	10,159,614
Stock options	2,101,964	1,528,475
	2,101,964	11,688,089

As the Company incurred a net loss for the three and nine months ended September 30, 2016 there is no income allocation required under the two‑class method or dilution attributed to weighted‑average shares outstanding in the computation of diluted loss per share attributable to common stockholders.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Following the Company’s decision to close its Phase 1 study of MRX34, in November 2016 the Company intends to reduce the total number of full-time employees from 36 to 12 to reduce operating expenses and streamline its operations. The Company expects the majority of the employees included in the reduction will be separated from the Company during the fourth quarter of 2016 and expects the remainder will discontinue employment with the Company during the first quarter of 2017. In addition, the Company has entered into retention agreements with certain employees necessary to close the Phase 1 trial of MRX34 and maintain the operations of the Company. The Company estimates that it will incur aggregate cash expenses of approximately $1.6 million under the workforce reduction, of which $1.3 million is attributed to one-time severance and benefits payments and $0.3 million relates to retention payments. In addition, depending on the outcome of the Company's evaluation of strategic alternatives, the Company may recognize an impairment to the carrying value of its fixed assets, additional costs associated with contract terminations, or a combination of both.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2016

Accounting Policies [Abstract]

Use of estimates

Research and development costs

Clinical Trial and Pre-Clinical Study Accruals

Stock-based compensation

Stock‑based compensation

Fair value measurements


•	Level 1 – Unadjusted prices in active markets for identical assets or liabilities.


•	Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability.


•	Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date.

Restricted Cash

Marketable Securities

Comprehensive loss

Comprehensive loss is composed of net loss and other comprehensive income or loss. Other comprehensive loss consists of unrealized gains and losses on marketable securities.

Recently Issued Accounting Pronouncements

Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Summary of Available-for-sale Securities Held

The following table summarizes the available-for-sale securities held at September 30, 2016 (in thousands):



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
September 30, 2016
U.S. government agency securities and treasuries	$	25,013	$	7	$	(3	)	$	25,017
Corporate debt securities	14,695		—		(12		)	14,683
Total available-for-sale securities	$	39,708	$	7	$	(15	)	$	39,700

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Schedule of Company's Assets that are Measured at Fair Value on a Recurring Basis

The following table sets forth the Company’s assets that are measured at fair value on a recurring basis as of September 30, 2016 and December 31, 2015 (in thousands):



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
September 30, 2016
Assets:
Cash and Cash Equivalents
Money market funds	$	23,805	$	23,805	$	—	$	—
US government agency securities and treasuries	$	1,353	—		1,353
Corporate debt securities	1,800		—		1,800		—
Total cash and cash equivalents	26,958		23,805		3,153		—
Marketable securities
U.S. government agency securities and treasuries	24,617		—		24,617		—
Corporate debt securities	14,683		—		14,683		—
Total marketable securities	39,300		—		39,300		—
U.S. government agency securities and treasuries, long-term	400		—		400		—
Restricted cash	2,431		2,431		—		—
Total assets	$	69,089	$	26,236	$	42,853	$	—

December 31, 2015
Assets:
Money Market Funds	89,713		89,713		—		—
Total Assets	$	89,713	$	89,713	$	—	$	—

Property and Equipment (Tables)

9 Months Ended

Sep. 30, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consisted of the following (in thousands):



	September 30, 2016			December 31, 2015
Construction in Progress	$	598		$	—
Furniture, computers and equipment	1,540			687
Leasehold improvements	36			18
Accumulated depreciation	(340		)	(330		)
	$	1,834		$	375

Stock Option Plans (Tables)

9 Months Ended

Sep. 30, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock Option Activity

The Company’s stock option activity for the nine months ended September 30, 2016 was as follows:



			Weighted‑
			Average		Weighted‑Average
	Number		Exercise		Contractual
	of Shares		Price		Life (years)
Outstanding at December 31, 2015	1,529,459		6.29		9.00
Granted	928,250		4.41
Exercised	(5,313	)	1.65
Forfeited/canceled	(350,432	)	6.85
Outstanding at September 30, 2016	2,101,964		$	5.37	8.65
Options exercisable at September 30, 2016	646,142		$	5.33	7.40

Schedule of Stock Compensation Expense

Total stock-based compensation expense for the three and nine months ended September 30, 2016 was recognized as follows in the statements of comprehensive loss (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development expense	$	155	$	57	$	261	$	137
General and administrative expense	358		153		941		424
Total stock based compensation	$	513	$	210	$	1,202	$	561

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2016

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments Payable

Under the Lease agreement, future minimum payments payable are approximately as follows:



		Operating
Period ending December 31,		Lease
2016	(three months)	—
2017		$	450,929
2018		614,855
2019		633,364
2020	and thereafter	5,218,227
Total		$	6,917,375

Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss per Share

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except share and per share data):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Net loss	$	(5,365	)	$	(6,231	)	$	(17,574	)	$	(16,194	)
Accretion of convertible preferred stock to redemption value	—			—			—			(448		)
Accrued dividends on convertible preferred stock	—			(1,554		)	—			(3,769		)
Net loss attributable to common stockholders—basic and diluted	(5,365		)	(7,785		)	(17,574		)	(20,411		)
Weighted-average number of common shares—basic and diluted	20,835,868			94,753			20,832,727			91,650
Net loss per share attributable to common stockholders—basic and diluted	$	(0.26	)	$	(82.16	)	$	(0.84	)	$	(222.70	)

Schedule of Potentially Dilutive Securities Excluded from the Computation of Weighted Average Common Shares Outstanding



	September 30,
	2016	2015
Convertible preferred stock	—	10,159,614
Stock options	2,101,964	1,528,475
	2,101,964	11,688,089

Nature of Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Oct. 31, 2015	Sep. 30, 2016	Dec. 31, 2015
Equity transactions
Par value (in USD per share)		$ 0.001	$ 0.001
Cash , cash equivalents and marketable securities		$ 66.7
Minimum
Equity transactions
Period over which cash resources will be sufficient to maintain the company's current and planned operations		12 months
Initial Public Offering \| Common Stock
Equity transactions
Shares issued (in shares)	6,250,000
Par value (in USD per share)	$ 0.001
Share price (in USD per share)	$ 7.00
Proceeds from issuance of common stock in initial public offering	$ 43.7
Private Placement \| Common Stock
Equity transactions
Shares issued (in shares)	2,395,010
Proceeds from issuance of common stock in private placement	$ 16.7
Shares Purchased by Underwriters of the IPO \| Common Stock
Equity transactions
Shares issued (in shares)	704,962

Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016
Fair value of assets measured at fair value on a recurring basis
Transfers of assets and liabilities between Level 1, Level 2, or Level 3	$ 0	$ 0	$ 0	$ 0
Standby Letters of Credit
Standby Letter of Credit
Standby letter of credit					$ 2,400,000

Marketable Securities (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale securities held
Amortized Cost	$ 39,708,000
Unrealized Gains	7,000
Unrealized Losses	(15,000)
Fair Value	39,700,000
Maturities
Available-for-sale securities with remaining maturities greater than one year	400,000	$ 0
U.S. government agency securities and treasuries
Available-for-sale securities held
Amortized Cost	25,013,000
Unrealized Gains	7,000
Unrealized Losses	(3,000)
Fair Value	25,017,000
Corporate debt securities
Available-for-sale securities held
Amortized Cost	14,695,000
Unrealized Gains	0
Unrealized Losses	(12,000)
Fair Value	$ 14,683,000

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	$ 39,300	$ 0
Marketable securities, noncurrent	400	0
Marketable securities
Available for sale securities in an unrealized loss position	22,900
Available for sale securities, unrealized loss	15
Recurring
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	26,958
Marketable securities, current	39,300
Total assets	69,089	89,713
Recurring \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	23,805
Marketable securities, current	0
Total assets	26,236	89,713
Recurring \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	3,153
Marketable securities, current	39,300
Total assets	42,853	0
Recurring \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0
Marketable securities, current	0
Total assets	0	0
Recurring \| U.S. government agency securities and treasuries
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	24,617
Marketable securities, noncurrent	400
Recurring \| U.S. government agency securities and treasuries \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	0
Marketable securities, noncurrent	0
Recurring \| U.S. government agency securities and treasuries \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	24,617
Marketable securities, noncurrent	400
Recurring \| U.S. government agency securities and treasuries \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	0
Marketable securities, noncurrent	0
Recurring \| Corporate debt securities
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	14,683
Recurring \| Corporate debt securities \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	0
Recurring \| Corporate debt securities \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	14,683
Recurring \| Corporate debt securities \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Marketable securities, current	0
Money market funds \| Recurring
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	23,805	89,713
Money market funds \| Recurring \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	23,805	89,713
Money market funds \| Recurring \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0	0
Money market funds \| Recurring \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0	$ 0
U.S. government agency securities and treasuries \| Recurring
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	1,353
U.S. government agency securities and treasuries \| Recurring \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0
U.S. government agency securities and treasuries \| Recurring \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	1,353
U.S. government agency securities and treasuries \| Recurring \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents
Corporate debt securities \| Recurring
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	1,800
Corporate debt securities \| Recurring \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0
Corporate debt securities \| Recurring \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	1,800
Corporate debt securities \| Recurring \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0
Restricted cash \| Recurring
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	2,431
Restricted cash \| Recurring \| Quoted prices in active markets (Level 1)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	2,431
Restricted cash \| Recurring \| Significant other observable inputs (Level 2)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	0
Restricted cash \| Recurring \| Significant unobservable inputs (Level 3)
Fair value of assets measured at fair value on a recurring basis
Cash and Cash Equivalents	$ 0

Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Property and equipment
Accumulated depreciation	$ (340)		$ (340)		$ (330)
Property and equipment, net	1,834		1,834		375
Depreciation expense	60	$ 12	105	$ 37
Construction in Progress
Property and equipment
Property and equipment, gross	598		598
Furniture, computers and equipment
Property and equipment
Property and equipment, gross	1,540		1,540		687
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 36		$ 36		$ 18

Common Stock - Voting and Dividends (Details)	9 Months Ended	106 Months Ended
Common Stock - Voting and Dividends (Details)	Sep. 30, 2016 vote	Sep. 30, 2016 USD ($)
Stockholders' Equity Note [Abstract]
Number of votes per common stock \| vote	1
Cash dividends \| $		$ 0

Common Stock - Offerings (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Oct. 05, 2015	Oct. 31, 2015	Sep. 30, 2015
Common Stock \| Private Placement
Class of Stock [Line Items]
Shares issued (in shares)		2,395,010
Proceeds from issuance of common stock in private placement		$ 16.7
Common Stock \| Initial Public Offering
Class of Stock [Line Items]
Shares issued (in shares)		6,250,000
Share price (in USD per share)		$ 7.00
Proceeds from issuance of common stock in initial public offering		$ 43.7
Common Stock \| Over-Allotment Option
Class of Stock [Line Items]
Shares issued (in shares)		704,962
CPRIT
Class of Stock [Line Items]
Grant contract			$ 16.8
Purchase agreement			$ 16.8
CPRIT \| Common Stock \| Private Placement
Class of Stock [Line Items]
Shares issued (in shares)	2,395,010
Share price (in USD per share)	$ 7.00
Proceeds from issuance of common stock in private placement	$ 16.6

Stock Option Plans - Plan Information (Details) - $ / shares	1 Months Ended				9 Months Ended	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2016	Dec. 31, 2015	Aug. 31, 2015	Dec. 31, 2008
Number of Shares
Outstanding at beginning of period (in shares)					1,529,459
Granted (in shares)					928,250
Exercised (in shares)					(5,313)
Forfeited/canceled (in shares)					(350,432)
Outstanding at end of period (in shares)					2,101,964	1,529,459
Exercisable at end of period (in shares)					646,142
Weighted Average Exercise Price
Outstanding at beginning of period (in USD per share)					$ 6.29
Granted (in USD per share)					4.41
Exercised (in USD per share)					1.65
Forfeited/canceled (in USD per share)					6.85
Outstanding at end of period (in USD per share)					5.37	$ 6.29
Exercisable at end of period (in USD per share)					$ 5.33
Additional disclosures
Weighted Average Remaining Contractual Life (years)					8 years 7 months 24 days	9 years
Weighted Average Remaining Contractual Life (years), Options exercisable					7 years 4 months 24 days
ESPP
Stock Option Plans
Number of stock options and stock purchase rights available for grant (in shares)					375,485
Percentage of discount for employees under ESPP					15.00%
Purchase price as a percentage of fair value under ESPP					85.00%
Shares issued during the period under ESPP (in shares)					0
2008 Plan
Stock Option Plans
Number of stock options and stock purchase rights available for grant (in shares)		1,061,585	669,935	554,782				330,582
Expiration period					10 years
Increase in number of stock options and stock purchase rights available for grant (in shares)		391,650	115,153	224,200
Number of Shares
Outstanding at end of period (in shares)					764,928
2015 Plan
Stock Option Plans
Number of stock options and stock purchase rights available for grant (in shares)							1,671,800
Increase in number of stock options and stock purchase rights available for grant (in shares)	1,041,527
2008 Plan and 2015 Plan
Stock Option Plans
Number of stock options and stock purchase rights available for grant (in shares)					3,508,492

Stock Option Plans - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stock-based compensation expense allocation
Stock based compensation	$ 513	$ 210	$ 1,202	$ 561
Stock Appreciation Rights
Stock-based compensation expense allocation
Awards granted (in shares)			0
2015 Plan \| Stock Options
Stock-based compensation expense allocation
Unrecognized compensation cost	5,100		$ 5,100
Unrecognized compensation cost, period of recognition			2 years 10 months 24 days
2015 Plan \| Restricted Stock Units
Stock-based compensation expense allocation
Awards granted (in shares)			0
Research and development expense
Stock-based compensation expense allocation
Stock based compensation	155	57	$ 261	137
General and administrative expense
Stock-based compensation expense allocation
Stock based compensation	$ 358	$ 153	$ 941	$ 424

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($)	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Interest and penalties related to income taxes	$ 0	$ 0	$ 0	$ 0

Agreements with Asuragen (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Agreements with Asuragen (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Shared Services Agreement with Asuragen
Shared Services Agreement
Expenses	$ 79	$ 100	$ 316	$ 295
Sublease Agreement with Asuragen
Shared Services Agreement
Expenses	$ 15		$ 59

License Agreements (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
License Agreements (Details) - USD ($)	Jan. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
License Agreements
Research and development expense		$ 3,384,000	$ 4,683,000	$ 11,589,000	$ 12,584,000
Rosetta Genomics Ltd.
License Agreements
Research and development expense						$ 1,600,000
Up front and milestone payments	$ 1,600,000
Aggregate payments to be made for each licensed product upon achievement of certain development and regulatory milestones		3,000,000		3,000,000
Marina Biotech Inc.
License Agreements
Aggregate payments to be made for each licensed product upon achievement of certain development and regulatory milestones		6,000,000		6,000,000
Cumulative up-front and milestone payments		2,100,000		2,100,000
Additional payments to be made for each licensed product upon achievement of certain development and regulatory milestones for a specified number of additional indications		4,000,000		4,000,000
Maximum cap on all milestone payments per product		10,000,000		10,000,000
Aggregate of all remaining development and regulatory milestone payments upon additional indications				4,000,000.0
Yale University
License Agreements
Maximum cap on all milestone payments per product		$ 600,000		$ 600,000

Commitments and Contingencies (Detail)	3 Months Ended	9 Months Ended
Commitments and Contingencies (Detail)	Sep. 30, 2016 USD ($) draw term	Sep. 30, 2016 USD ($) draw term	Jun. 30, 2016 USD ($)
Operating Lease
Initial term of lease		123 months
Number of terms lease can be extended \| term	2	2
Renewal term option of lease		60 months
Rent expense	$ 55,000	$ 55,000
Annual base rent		$ 600,000
Rent free term		3 months
Yearly increases in base rent		3.00%
Tenant improvement allowance		$ 1,900,000
Additional tenant improvement allowance available		$ 1,300,000
Amortization period of additional improvement allowance		120 months
Number of draws taken on the additional improvement allowance \| draw	0	0
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016 (three months)	$ 0	$ 0
2017	450,929	450,929
2018	614,855	614,855
2019	633,364	633,364
2020 and thereafter	5,218,227	5,218,227
Total	6,917,375	6,917,375
Standby Letters of Credit
Standby Letter of Credit
Initial amount of standby letter of credit			$ 2,400,000
Reduced amount of standby letter of credit if certain conditions are met	$ 800,000	$ 800,000

Net Loss Per Share Attributable to Common Stockholders - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net loss	$ (5,365)	$ (6,231)	$ (17,574)	$ (16,194)
Accretion of convertible preferred stock to redemption value	0	0	0	(448)
Accrued dividends on convertible preferred stock	0	(1,554)	0	(3,769)
Net loss attributable to common stockholders—basic and diluted	$ (5,365)	$ (7,785)	$ (17,574)	$ (20,411)
Weighted-average number of common shares—basic and diluted (in shares)	20,835,868	94,753	20,832,727	91,650
Net loss per share attributable to common stockholders—basic and diluted (in USD per share)	$ (0.26)	$ (82.16)	$ (0.84)	$ (222.70)

Net Loss Per Share Attributable to Common Stockholders - Dilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Potentially dilutive securities
Potentially dilutive securities excluded from the computation of diluted weighted average common shares outstanding	2,101,964	11,688,089
Convertible preferred stock
Potentially dilutive securities
Potentially dilutive securities excluded from the computation of diluted weighted average common shares outstanding	0	10,159,614
Stock options
Potentially dilutive securities
Potentially dilutive securities excluded from the computation of diluted weighted average common shares outstanding	2,101,964	1,528,475

Subsequent Events (Details) - Subsequent Event $ in Millions	5 Months Ended
	Mar. 31, 2017 USD ($) employee	Nov. 10, 2016 employee
Subsequent Event [Line Items]
Number of employees \| employee		36
Forecast
Subsequent Event [Line Items]
Number of employees \| employee	12
Cash expenses for reduction of employees	$ 1.6
Forecast \| One-time Severance and Benefit Payments
Subsequent Event [Line Items]
Cash expenses for reduction of employees	1.3
Forecast \| Retention Payments
Subsequent Event [Line Items]
Cash expenses for reduction of employees	$ 0.3