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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Mar. 07, 2019	Jun. 30, 2018
Document and Entity Information
Entity Registrant Name	CATABASIS PHARMACEUTICALS INC
Entity Central Index Key	0001454789
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Public Float			$ 63,319,764
Entity Common Stock, Shares Outstanding		11,495,742
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 15,294	$ 16,369
Short-term investments	22,276	0
Prepaid expenses and other current assets	1,345	1,094
Total current assets	38,915	17,463
Property and equipment, net	56	321
Restricted cash	113	113
Other assets	85
Total assets	39,169	17,897
Current liabilities:
Accounts payable	1,408	773
Accrued expenses	2,763	2,432
Current portion of notes payable, net of discount		2,479
Other liability		332
Total current liabilities	4,171	6,016
Deferred rent, net of current portion	9	89
Other liability	47
Total liabilities	4,227	6,105
Commitments (Note 9)
Stockholders' equity:
Preferred stock, $0.001 par value per share, 5,000,000 shares authorized and no shares issued and outstanding
Common stock, $0.001 par value per share, 150,000,000 shares authorized; 7,141,996 and 2,364,526 shares issued and outstanding at December 31, 2018 and 2017, respectively	7	2
Additional paid-in capital	232,243	183,224
Accumulated other comprehensive loss	(4)
Accumulated deficit	(197,304)	(171,434)
Total stockholders' equity	34,942	11,792
Total liabilities and stockholders' equity	$ 39,169	$ 17,897

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in Shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	7,141,996	2,364,526
Common stock, outstanding (in shares)	7,141,996	2,364,526

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements of Operations
Revenue	$ 0	$ 500
Operating expenses:
Research and development	17,042	18,682
General and administrative	9,329	8,912
Total operating expenses	26,371	27,594
Loss from operations	(26,371)	(27,094)
Other income (expense):
Interest expense	(100)	(462)
Interest and investment income	425	160
Other income, net	176	32
Total other income (expense), net	501	(270)
Net loss	$ (25,870)	$ (27,364)
Net loss per share - basic and diluted (in dollars per share)	$ (5.12)	$ (12.62)
Weighted-average common shares outstanding used in net loss per share - basic and diluted (in shares)	5,054,823	2,168,153

Consolidated Statements Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements Comprehensive Loss
Net loss	$ (25,870)	$ (27,364)
Other comprehensive (loss) income:
(Loss) gain on short-term investments	(4)	4
Total other comprehensive (loss) income:	(4)	4
Comprehensive loss	$ (25,874)	$ (27,360)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Gain	Total
Balance at Dec. 31, 2016	$ 2	$ 173,158	$ (144,070)	$ (4)	$ 29,086
Balance (in shares) at Dec. 31, 2016	1,881,758
Increase (Decrease) in Stockholders' Equity
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.4 million and $0.6 million for the years 2018 and 2017 respectively		8,036			8,036
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.4 million and $0.6 million for the years 2018 and 2017 respectively (in shares)	480,480
Proceeds from exercises of common stock options		23			23
Proceeds from exercises of common stock options (in shares)	2,288
Stock-based compensation expense		2,007			2,007
Unrealized losses on short-term investments					4
Realized gain on short-term investments				4	4
Net loss			(27,364)		(27,364)
Balance at Dec. 31, 2017	$ 2	183,224	(171,434)		$ 11,792
Balance (in shares) at Dec. 31, 2017	2,364,526				2,364,526
Increase (Decrease) in Stockholders' Equity
Issuance of common stock and warrants in public offerings, net of $3.1 million in issuance costs	$ 4	38,882			$ 38,886
Issuance of common stock and warrants in public offerings, net of $3.1 million in issuance costs (in shares)	4,200,000
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.4 million and $0.6 million for the years 2018 and 2017 respectively	$ 1	8,362			8,363
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.4 million and $0.6 million for the years 2018 and 2017 respectively (in shares)	577,195
Proceeds from exercises of common stock options		4			$ 4
Proceeds from exercises of common stock options (in shares)	291				291
Stock-based compensation expense		1,771			$ 1,771
Fractional shares eliminated pursuant to reverse stock split	(16)
Unrealized losses on short-term investments				(4)	(4)
Net loss			(25,870)		(25,870)
Balance at Dec. 31, 2018	$ 7	$ 232,243	$ (197,304)	$ (4)	$ 34,942
Balance (in shares) at Dec. 31, 2018	7,141,996				7,141,996

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Initial public offering
Stock issuance costs	$ 0.4	$ 0.6
Common stock warrants
Stock issuance costs	$ 3.1

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (25,870)	$ (27,364)
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization	119	304
Stock-based compensation expense	1,771	2,007
Accretion of discount/premium on investment securities	(6)	26
Non-cash interest expense	37	155
Gain on sale of fixed assets	(297)	(30)
Services received in non-monetary exchange	19
Changes in assets and liabilities:
Prepaid expenses and other current assets	(177)	(93)
Other assets	(85)
Accounts payable	662	(632)
Accrued expenses	396	(1,215)
Deferred rent	(81)	6
Other liabilities	47
Net cash used in operating activities	(23,465)	(26,836)
Investing activities
Purchases of short-term investments	(70,364)
Sales and maturities of short-term investments	48,090	14,910
Purchases of property and equipment		(57)
Sale of property and equipment	369	30
Net cash (used in) provided by investing activities	(21,905)	14,883
Financing activities
Proceeds from public offerings, net of issuance costs	38,886
Proceeds from at-the-market offering, net of issuance costs	8,253	8,036
Proceeds from exercise of common stock options and warrants	4	23
Payments on borrowing	(2,848)	(3,333)
Net cash provided by financing activities	44,295	4,726
Net decrease in cash, cash equivalents and restricted cash	(1,075)	(7,227)
Cash, cash equivalents and restricted cash, beginning of period	16,482	23,709
Cash, cash equivalents and restricted cash, end of period	15,407	16,482
Supplemental disclosure of cash flow information
Cash paid for interest	79	$ 327
Non-cash investing activities:
Fixed asset purchases included in accounts payable	18
Non-cash financing activities
At-the-market issuance costs included in accounts payable and accrued expenses	$ 110

Organization and Operations	12 Months Ended
Organization and Operations	Dec. 31, 2018
Organization and Operations
Organization and Operations	1. Organization and Operations The Company Catabasis Pharmaceuticals, Inc. (the "Company") is a clinical-stage biopharmaceutical company. The Company’s lead program is edasalonexent, formerly known as CAT-1004, an oral small molecule designed to inhibit NF- kB, or nuclear factor kappa-light-chain-enhancer of activated B cells, in development for the treatment of Duchenne muscular dystrophy (“DMD”). The Company believes edasalonexent has the potential to be a foundational therapy for all patients affected by DMD, regardless of the underlying dystrophin mutation. DMD is an ultimately fatal genetic disorder involving progressive muscle degeneration. The United States Food and Drug Administration has granted orphan drug, fast track and rare pediatric disease designations to edasalonexent for the treatment of DMD. The European Commission has granted orphan medicinal product designation to edasalonexent for the treatment of DMD. The Company was incorporated in the State of Delaware on June 26, 2008. Liquidity The Company has entered into various sales agreements with Cowen and Company LLC, (“Cowen”), pursuant to which the Company could issue and sell shares of common stock under at-the-market offering programs (the “ATM Programs”). Shares sold pursuant to these sales agreements were sold pursuant to a shelf registration statement, which became effective on July 19, 2016. The Company pays Cowen 3% of the gross proceeds from any common stock sold through these sales agreements. The Company has $22.6 million remaining available under its current sales agreement. During the year ended December 31, 2018, the Company sold an aggregate of 577,195 shares of common stock pursuant to the ATM Programs, at an average price of $15.27 per share, for gross proceeds of $8.8 million, resulting in net proceeds of $8.4 million after deducting sales commissions and offering expenses. On June 19, 2018, the Company entered into an underwriting agreement with Oppenheimer & Co. Inc. relating to an underwritten public offering (the “June 2018 Financing”) of 4,200,000 shares of the Company’s common stock, par value $0.001 per share, and accompanying warrants to purchase up to 4,200,000 shares of common stock, at a combined price to the public of $10.00 per unit, for gross proceeds of $42.0 million, and net proceeds of $38.9 million. As of December 31, 2018, the Company had an accumulated deficit of $197.3 million. The Company has been primarily involved with research and development activities and has incurred operating losses and negative cash flows from operations since its inception. The Company is subject to a number of risks similar to other life science companies, including, but not limited to, successful discovery and development of its drug candidates, raising additional capital, development by its competitors of new technological innovations, protection of proprietary technology and regulatory approval and market acceptance of the Company’s products. The Company anticipates that it will continue to incur significant operating losses for the next several years as it continues to develop its product candidates. As of December 31, 2018, the Company had available cash, cash equivalents and short-term investments of $37.6 million. Subsequent to year end, the Company raised net proceeds of $20.5 million through 2019 equity financings. Based on the Company’s current operating plan, the Company believes it has sufficient cash, cash equivalents and short-term investments to fund operations into the fourth quarter of 2020. The Company will require substantial additional capital to fund operations. The Company has not generated any product revenues and has financed its operations primarily through public offerings and private placements of its equity securities. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition. Reverse Stock Split On December 28, 2018, the Company effected a reverse stock split of its outstanding shares of common stock at a ratio of one-for-ten pursuant to a Certificate of Amendment to its Certificate of Incorporation filed with the Secretary of State of the State of Delaware. The reverse stock split was reflected on Nasdaq beginning with the opening of trading on December 31, 2018. The primary purpose of the reverse stock split, which was approved by the Company’s stockholders at the Company’s Special Meeting of Stockholders on December 12, 2018, was to enable the Company to regain compliance with the $1.00 minimum bid price requirement for continued listing on Nasdaq. Pursuant to the reverse stock split, every ten shares of the Company’s issued and outstanding shares of common stock were automatically combined into one issued and outstanding share of common stock, without any change in the par value per share of the common stock. All share and per share amounts of the common stock included in the accompanying consolidated financial statements have been retrospectively adjusted to give effect to the reverse stock split for all periods presented, including reclassifying an amount equal to the reduction in par value to additional paid-in capital. Amounts of common stock resulting from the reverse stock split were rounded down to the nearest whole share and any resulting fractional shares were cancelled for cash. The number of authorized shares of the Company’s common stock remained unchanged. The reverse stock split affected all issued and outstanding shares of the Company’s common stock, and the respective numbers of shares of common stock underlying outstanding stock options, outstanding warrants and the Company’s equity incentive plans were proportionately adjusted.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Catabasis Securities Corporation. All intercompany balances and transactions have been eliminated in consolidation. These consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented.

Use of Estimates

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

The Company utilizes certain estimates to record expenses relating to research and development contracts. These contract estimates, which are primarily related to the length of service of each contract and the amount of service provided as of each measurement date, are determined by the Company based on input from internal project management, as well as from third-party service providers.

Off-Balance Sheet Risk and Concentrations of Credit Risk

The Company has no off-balance sheet risk, such as foreign exchange contracts, option contracts or other foreign hedging arrangements. Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents, short-term investments and restricted cash. The primary objectives for the Company's investment portfolio are the preservation of capital and the maintenance of liquidity. The Company's investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk.

Cash and Cash Equivalents and Restricted Cash

The Company considers highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents, which consist of money market funds, corporate debt securities and reverse repurchase agreements are stated at fair value. Cash and cash equivalents consist of the following (in thousands):


	December 31,
	2018		2017
Cash	$	4,390	$	2,781
Money market fund		5,956		13,588
Corporate debt securities		1,948		—
Reverse repurchase agreements		3,000		—
Total	$	15,294	$	16,369

The reconciliation of cash, cash equivalents and restricted cash reported within the applicable balance sheet that sum to the total of the same such amount shown in the statement of cash flows is as follows:


	December 31,
	2018		2017
Cash and cash equivalents	$	15,294	$	16,369
Restricted cash		113		113
Total	$	15,407	$	16,482

Short-Term Investments

The Company classifies all corporate debt securities with a remaining maturity of greater than three months and reverse repurchase agreements with a remaining maturity of greater than one business day at the time of purchase as short-term investments. Short-term investments are recorded at fair value, with the unrealized gains and losses reported in other comprehensive loss. The amortized cost of debt securities is adjusted for the amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest and investment income. Realized gains and losses, interest, dividends and declines in value judged to be other-than-temporary are included in interest and investment income.

The cost of securities sold is based on the specific identification method for purposes of recording realized gains and losses. To determine whether an other-than-temporary impairment exists, the Company considers whether it has the ability and intent to hold the investment until a market price recovery, and whether evidence indicating the recoverability of the cost of the investment outweighs evidence to the contrary.

Fair Value of Financial Instruments

The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

The carrying amounts reflected in the balance sheets for cash equivalents, restricted cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values at December 31, 2018 and 2017, due to their short-term nature. There have been no changes to the valuation methods during the years ended December 31, 2018 and 2017. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between levels during the year ended December 31, 2018 and 2017.

The Company’s investment portfolio may include fixed income securities that do not always trade on a daily basis. As a result, the pricing services used by the Company apply other available information as applicable through processes such as benchmark yields, benchmarking of like securities, sector groupings and matrix pricing to prepare valuations. The Company validates the prices provided by its third party pricing services by obtaining market values from other pricing sources and analyzing pricing data in certain instances. The Company also invests in certain reverse repurchase agreements which are collateralized by deposits in the form of U.S. Government Securities and Obligations for an amount no less than 102% of their value. The Company does not record an asset or liability for the collateral as the Company is not permitted to sell or re-pledge the collateral. The collateral has at least the prevailing credit rating of U.S. Government Treasuries and Agencies. The Company utilizes a third party custodian to manage the exchange of funds and ensure that collateral received is maintained at 102% of the value of the reverse repurchase agreements on a daily basis.

Property and Equipment

Property and equipment consist of computer equipment, leasehold improvements and furniture and fixtures. Property and equipment is stated at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets. Costs of major additions and betterments are capitalized; maintenance and repairs, which do not improve or extend the life of the respective assets, are charged to expense as incurred. Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and the resulting gain or loss is recognized.

Impairment of Long-Lived Assets

The Company continually evaluates whether events or circumstances have occurred that indicate that the estimated remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets may be impaired. The Company has not recognized any significant impairment charges from inception through December 31, 2018.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development costs include salaries and personnel-related costs, stock-based compensation, consulting fees, fees paid for contract research services, the costs of laboratory equipment and facilities and other external costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred. The deferred amounts are expensed as the related goods are delivered or the services are performed.

Revenue Recognition

The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”), Revenue from Contracts with Customers, (“ASC 606”). This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under the agreement, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

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 share-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 term 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 equal to the grant date fair value of stock options on a straight-line basis over the requisite service period.

The Company expenses restricted stock awards based on the fair value of the award on a straight-line basis over the associated service period of the award.

During the years ended December 31, 2018 and 2017, the Company recorded stock-based compensation expense for employee and non-employee stock options and restricted stock, which was allocated as follows in the statements of operations (in thousands):


	Year Ended December 31,
	2018		2017
Research and development	$	673	$	784
General and administrative		1,098		1,223
Total	$	1,771	$	2,007

No related tax benefits were recognized for the years ended December 31, 2018 and 2017.

Grant Awards

In the year ended December 31, 2017, the Company received $124,000 in grants from the Muscular Dystrophy Association and Friedreich's Ataxia Research Alliance. No such grants were received in the year ended December 31, 2018. In the years ended December 31, 2018 and 2017, the Company utilized $8,000 and $205,000 of the grants received to offset related expenses incurred in the Company’s statements of operations.

Net Loss Per Share

Basic net loss per share is calculated by dividing net loss by the weighted average shares outstanding during the period, without consideration for Common Stock equivalents. Diluted net loss per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of Common Stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the Company’s dilutive net loss per share calculation, stock options and warrants to purchase Common Stock were considered to be Common Stock equivalents but were excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive; therefore, basic and diluted net loss per share were the same for all periods presented.

The following Common Stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2018	2017
Stock options	433,389	283,277
Common stock warrants	4,202,449	2,454
	4,635,838	285,731

Income Taxes

The Company provides deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the Company's financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC Topic 740, Expenses—Income Taxes. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company did not have any significant uncertain tax positions for any periods presented.

Segment Information

Operating segments are identified as components of an enterprise for which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision making group, in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business in one operating segment. The Company operates in one geographic segment.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. For the years ended December 31, 2018 and 2017 amounts in accumulated other comprehensive loss were comprised of unrealized gains and losses on short-term investments.

Recent Accounting Pronouncements-Adopted

In October 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows- Restricted Cash (Topic 230), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and restricted cash or restricted cash equivalents. Therefore, amounts described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The Company adopted ASU 2016-18 in the period beginning January 1, 2018. Upon adoption of ASU 2016-18 the Company revised the presentation as well as caption of certain items within the audited consolidated statements of cash flows to conform to the current period presentation. These revisions had no impact on the net cash used in operating activities or cash, cash equivalents and restricted cash at the end of the period.

In July 2018, the FASB issued ASU 2018-07, Compensation- Stock Compensation (Topic 718). This standard simplifies several areas of the accounting for non-employee share-based payment transactions. This amendment is effective for annual reporting periods beginning after December 15, 2018, and the Company early adopted this standard on October 1, 2018. The adoption did not have a material impact on the Company’s consolidated financial statements.

Recent Accounting Pronouncements-Not Yet Adopted

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

In February 2016, the FASB issued ASU 2016-02, Leases. This standard amends the existing guidance to require lessees to present most leases on their balance sheets but recognize corresponding expenses on their statements of operations. The FASB added a transition option to the new leases standard that allows entities to not apply the new guidance in the comparative periods they present in their financial statements in the year of adoption. The FASB also provided a practical expedient that gives lessors an option to combine non-lease and associated lease components when certain criteria are met and requires a lessor to account for the combined component in accordance with the new revenue standard if the associated non-lease components are the predominant component. This standard is effective for annual reporting periods beginning after December 15, 2018. The Company will adopt this standard as of January 1, 2019 using the modified retrospective approach recording any cumulative adjustment to retained earnings. The adoption of this standard is expected to have a material impact on lease assets and lease liabilities but will not materially impact consolidated net losses. The Company will elect a package of practical expedients permitted under the transition guidance within the new standard, which among other things, allows the Company to carryforward the historical lease classification.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820). This standard includes amendments regarding changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and disclosure requirements of measurement uncertainty. This amendment is effective for annual reporting periods beginning after December 15, 2019. The Company is currently evaluating the impact that this standard will have on its consolidated financial statements.

Financial Instruments

12 Months Ended

Dec. 31, 2018

Financial Instruments

Financial Instruments

3. Financial Instruments

The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value. Below is a summary of assets and liabilities measured at fair value on a recurring basis (in thousands):


	As of December 31, 2018
	Quoted Prices		Significant		Significant
	in Active		Observable		Unobservable
	Markets		Inputs		Inputs
	(Level 1)		(Level 2)		(Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	5,956	$	—	$	—	$	5,956
Corporate debt securities		—		1,948		—		1,948
Reverse repurchase agreements		—		3,000		—		3,000
Short-term investments:
Corporate debt securities		—		7,276		—		7,276
Reverse repurchase agreements		—		15,000		—		15,000
Total assets	$	5,956	$	27,224	$	—	$	33,180


	As of December 31, 2017
	Quoted Prices		Significant		Significant
	in Active		Observable		Unobservable
	Markets		Inputs		Inputs
	(Level 1)		(Level 2)		(Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	13,588	$	—	$	—	$	13,588
Total assets	$	13,588	$	—	$	—	$	13,588

As of December 31, 2018, the Company’s cash equivalents consisted of money market funds, corporate debt securities, and reverse repurchase agreements. As of December 31, 2017, the Company’s cash equivalents consisted of money market funds. All cash equivalents in both periods approximated their fair value due to their short-term nature.

- 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

Short-Term Investments

12 Months Ended

Dec. 31, 2018

Short-Term Investments

Short-Term Investments

4. Short-Term Investments

As of December 31, 2017, the Company held no short-term investments. The following table summarizes the short-term investments held at December 31, 2018 (in thousands):


			Gross Unrealized		Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
December 31, 2018
Corporate debt securities	$	7,280	$	—	$	(4)	$	7,276
Reverse repurchase agreements		15,000		—		—		15,000
Total	$	22,280	$	—	$	(4)	$	22,276

The contractual maturities of all short-term investments held at December 31, 2018 were one year or less. There were seven short-term investments in an unrealized loss position at December 31, 2018, none of which had been in an unrealized loss position for more than 12 months. The aggregate fair value of these securities at December 31, 2018 was approximately $7.3 million. The Company did not hold any securities with other-than-temporary impairments at December 31, 2018.

Gross realized gains and losses on the sales of short-term investments are included in other income, net. Unrealized holding gains or losses for the period that have been included in accumulated other comprehensive income, as well as gains and losses reclassified out of accumulated other comprehensive income into other income, net were not material to the Company’s consolidated results of operations. During the years ended December 31, 2018 and 2017 all proceeds related to maturities of underlying securities. The gains on proceeds of maturities of short-term investments were not material to the Company’s consolidated results of operations for the years ended December 31, 2018 and 2017.

Restricted Cash	12 Months Ended
Restricted Cash	Dec. 31, 2018
Restricted Cash
Restricted Cash	5. Restricted Cash At December 31, 2018 and 2017, the Company had an outstanding letter of credit for $0.1 million as a security deposit for its operating lease agreement for office space (Note 9). The Company is required to maintain this deposit for the duration of the lease agreement.

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property and Equipment

Property and Equipment

6. Property and Equipment

Property and equipment and related accumulated depreciation were as follows (in thousands):


		December 31,
	Estimated Useful Life (Years)	2018		2017
Lab equipment	3	$	—	$	1,470
Computer equipment	3		100		165
Furniture and fixtures	5		75		77
Leasehold improvements	Lesser of useful life or remaining lease term		202		264
			377		1,976
Less accumulated depreciation and amortization			(321)		(1,655)
Total property and equipment, net		$	56	$	321

Depreciation and amortization expense was $0.1 million and $0.3 million for the years ended December 31, 2018 and 2017, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2018

Accrued Expenses

Accrued Expenses

7. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2018		2017
Accrued compensation	$	1,241	$	632
Accrued contracted research costs		680		1,357
Accrued professional fees		393		298
Accrued severence		109		—
Accrued franchise fee		168		—
Accrued other		172		145
Total	$	2,763	$	2,432

Notes Payable	12 Months Ended
Notes Payable	Dec. 31, 2018
Notes Payable
Notes Payable	8. Notes Payable The Company had a credit facility with MidCap Financial Trust, Flexpoint MCLS SPV LLC and Square 1 Bank pursuant to which the Company received total proceeds of $10.0 million under term loans (the “Credit Facility”). All amounts outstanding under the Credit Facility were due on October 1, 2018 and were collateralized by substantially all of the Company’s personal property, other than its intellectual property. The Credit Facility has expired. The Company recognized $0.1 million and $0.5 million of interest expense related to the Credit Facility in the years ended December 31, 2018 and 2017, respectively.

Commitments

12 Months Ended

Dec. 31, 2018

Commitments

Commitments

9. Commitments

In November 2010, the Company entered into an operating lease for office and laboratory space, which has been amended multiple times. Based on the latest amendment, the lease agreement includes escalating rent payments and is effective through June 30, 2020. The Company is recognizing rent expense on a straight-line basis over the lease term.

Future minimum payments required under the non-cancelable operating lease as of December 31, 2018 are summarized as follows (in thousands):


Period Ending December 31,	Amount
2019		1,421
2020		721
Total minimum lease payments	$	2,142

Rent expense was $1.1 million and $1.3 million for the years ended December 31, 2018 and 2017, respectively.

On October 15, 2018, the Company entered into a short-term lease with Inzen Therapeutics (“Inzen”), to sublease a portion of the Company’s facility (the “Sublease”). The sublease term is from October 15, 2018 through June 30, 2020. Inzen is obligated to pay the Company approximately $1.1 million and $0.5 million in base rent during the years ended December 31, 2019 and 2020, respectively. The Company is still obligated to all payment terms pursuant to the lease agreement, as amended. During the year ended December 31, 2018, the Company received $0.3 million in payments from Inzen which was recorded as a deduction to rent expense in the accompanying consolidated statement of operations.

Revenue Recognition	12 Months Ended
Revenue Recognition	Dec. 31, 2018
Revenue Recognition
Revenue Recognition	10. Revenue Recognition In August 2017, the Company entered into an option agreement ("Option Agreement") with an unaffiliated party ("Recipient"), which is within the scope of ASC Topic 606: Revenue from Contracts with Customers. Under the terms of the Option Agreement, the Company agreed to provide compound material for certain of its product candidates and the right for the Recipient to use the material to perform research during the term of the Option Agreement in exchange for $500 thousand. In December 2017, the Recipient terminated the agreement and there are no remaining performance obligations. In the future, the Company will seek to generate additional revenue primarily from a combination of product sales and collaborations with strategic partners. During the year ended December 31, 2017, the Company recognized $0.5 million in revenue related to the Option Agreement. The Company did not recognize revenue in the year ended December 31, 2018.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Stockholders' Equity

Stockholders' Equity

11. Stockholders’ Equity

Preferred Stock

As of December 31, 2018, the Company had 5,000,000 shares of preferred stock authorized for issuance, $0.001 par value per share, with none issued or outstanding. Preferred stock may be issued from time to time in one or more series, each series to have such terms as stated or expressed in the resolutions providing for the issue of such series adopted by the board of directors of the Company. Preferred stock which may be redeemed, purchased or acquired by the Company may be reissued except as otherwise provided by law.

Common Stock Warrants

June 2018 Warrants

In the June 2018 financing, the Company issued warrants to purchase 4,200,000 shares of common stock with an exercise price of $12.00 per share, which were immediately exercisable upon issuance and will expire five years from the date of issuance.

The terms of the warrants include certain provisions related to fundamental transactions, a cashless exercise provision in the event registered shares are not available and do not include any mandatory redemption provisions. Therefore, the warrants have been classified in stockholders’ equity. Any changes to fair value of the warrants will not be recognized so long as the warrants continue to be equity classified.

As of December 31, 2018, all warrants related to this transaction were outstanding with a remaining contractual life of 4.47 years.

Warrants Associated with the Credit Facility

In conjunction with the credit facility (Note 8), the Company issued warrants to purchase 2,454 shares of Common Stock with an exercise price of $122.12 per share. As of December 31, 2018, all warrants related to this transaction were outstanding with a weighted average contractual life of 2.95 years.

Common Stock

As of December 31, 2018, the Company had 150,000,000 shares of Common Stock authorized for issuance, $0.001 par value per share, with 7,141,996 shares issued and outstanding. The voting, dividend and liquidation rights of holders of Common Stock are subject to and qualified by the rights, powers and preferences of the holders of any outstanding Preferred Stock. The Company's Common Stock has the following characteristics:

Voting

The holders of Common Stock are entitled to one vote for each share of Common Stock held at all meetings of stockholders and written actions in lieu of meetings.

Dividends

The holders of Common Stock are entitled to receive dividends, if and when declared by the board of directors. Cash dividends may not be declared or paid to holders of Common Stock until paid on each series of outstanding Preferred Stock in accordance with their respective terms. No dividends have been declared or paid from the Company's inception through December 31, 2018.

Liquidation

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, the holders of Common Stock are entitled to share ratably in the Company’s assets available for distribution to stockholders, subject to any preferential or other rights of any then-outstanding Preferred Stock.

Reserved for Future Issuance

The Company has reserved for future issuance the following shares of Common Stock:


	As of December 31,
	2018	2017
Warrants for the purchase of Common Stock	4,202,449	2,454
Options outstanding to purchase Common Stock	433,389	283,277
Options reserved to purchase Common Stock	877,917	83,739
Employee Stock Purchase Plan	76,011	52,365
Total	5,589,766	421,835

Stock Incentive Plans

12 Months Ended

Dec. 31, 2018

Stock Incentive Plans

Stock Incentive Plans

12. Stock Incentive Plans

Prior to the IPO, the Company granted awards to eligible participants under its 2008 Equity Incentive Plan (“2008 Plan”). In May 2015, the Company’s board of directors adopted and, in June 2015, the Company’s stockholders approved the 2015 Stock Incentive Plan (“2015 Plan”), which became effective immediately prior to the effectiveness of the IPO. Subsequent to the IPO, option grants are awarded to eligible participants only under the 2015 Plan.

The 2015 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2015 Plan.

As of December 31, 2018, the Company had reserved 65,587 shares of Common Stock under the 2008 Plan, of which none remained available for future issuance. As of December 31, 2018, the Company had reserved 1,245,719 shares of Common Stock under the 2015 Plan, of which 877,917 shares remained available for future issuance. Under the 2015 Plan, stock options may not be granted with exercise prices at less than fair value on the date of the grant.

Terms of stock option agreements, including vesting requirements, are determined by the Company's board of directors, subject to the provisions of the applicable stock incentive plan. Options granted by the Company generally vest ratably over four years, with a one-year cliff, and options are exercisable from the date of grant for a period of ten years. For options granted through December 31, 2018, the exercise price or purchase price, as applicable, equaled the estimated fair value of the Common Stock as determined by the Company's board of directors on the date of grant.

A summary of the Company’s stock option activity and related information for employees and non-employees follows:


				Weighted
				Average
		Weighted-		Remaining	Aggregate
		Average Exercise		Contractual		Instrinsic Value
	Shares	Price		Term (years)	(in thousands)
Outstanding at December 31, 2017	283,277	$	45.42	7.75	$	216
Granted	213,384	$	9.84
Exercised	(291)	$	12.40
Cancelled or forfeited	(62,981)	$	37.64
Outstanding at December 31, 2018	433,389	$	29.05	7.97	$	—
Vested and Exercisable at December 31, 2018	168,566	$	50.91	6.31	$	—

The total intrinsic value of options exercised for the years ended December 31, 2018 and 2017 was $1 thousand and $40 thousand, respectively. The total adjusted fair value of employee options vested for the years ended December 31, 2018 and 2017 was $1.7 million and $2.2 million, respectively. The weighted-average grant date fair value of options granted to employees and non-employees for the years ended December 31, 2018 and 2017 was $6.64 and $8.48, respectively.

At December 31, 2018, the total unrecognized compensation expense related to unvested stock option awards was $2.3 million. The Company expects to recognize that cost over a weighted-average period of approximately 1.7 years.

Stock-Based Compensation Expense

The fair value of stock options granted to employees and non-employees was estimated using the Black-Scholes option-pricing model based on the following assumptions:


	Year Ended December 31,
	2018				2017
Weighted-average expected volatility	73.7	-	76.9	%	76.1	-	81.9	%
Expected term (in years)	5.75	-	6.25		6.25	-	9.77
Risk-free interest rate	2.67	-	2.84	%	2.00	-	2.38	%
Expected dividend yield			0	%			0	%

Volatility

Due to the lack of company-specific historical and implied volatility data of its Common Stock, the Company does not have relevant historical data to support its expected volatility. As such, the Company has used a weighted average of expected volatility based on the volatilities of a representative group of publicly traded biopharmaceutical companies. For purposes of identifying representative companies, the Company considered characteristics such as number of product candidates in early stages of product development, area of therapeutic focus, and length of trading history. The expected volatility was determined using an average of the historical volatilities of the representative group of companies for a period equal to the expected term of the option grant. The Company intends to continue to consistently apply this process using the same representative companies until a sufficient amount of historical information regarding the volatility of the Company's own share price becomes available or until circumstances change, such that the identified entities are no longer representative companies. In the latter case, more suitable, similar entities whose share prices are publicly available would be utilized in the calculation.

Expected Term

The Company uses the “simplified method” to estimate the expected term of stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the contractual term (ten years) and the vesting term (generally four years) of the Company's stock options, taking into consideration multiple vesting tranches. The Company utilizes this method due to lack of historical exercise data and the plain-vanilla nature of the Company's share-based awards.

Risk-Free Rate

The risk-free rate was based on the yield curve of U.S. Treasury securities with periods commensurate with the expected term of the options being valued.

Employee Stock Purchase Plan

In June 2015, the Company’s board of directors adopted and the Company’s stockholders approved the 2015 Employee Stock Purchase Plan (the “2015 ESPP”) which became effective upon closing of the IPO. The 2015 ESPP initially authorized the issuance of up to a total of 18,235 shares of Common Stock to participating eligible employees. The number of authorized shares increases each January 1, commencing on January 1, 2016 and ending on December 31, 2026, by an amount equal to the lesser of one percent of the Company’s outstanding shares as of the first day of the applicable year, 36,470 shares and any lower amount determined by the Company’s board of directors. As of December 31, 2018, there had been no shares issued under the 2015 ESPP.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Taxes

Income Taxes

13. Income Taxes

For the years ended December 31, 2018 and 2017, the Company did not record a provision for federal or state income taxes as it has incurred cumulative net operating losses since inception.

On December 22, 2017, the Tax Cuts and Jobs Act (the “ Tax Act”) was enacted in the United States. The Tax Act reduces the U.S. federal corporate tax rate from a graduated rate of 35% to a flat rate of 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign sourced earnings. The Company does not currently have any foreign subsidiaries and the international aspects of the Tax Act are not applicable.

In connection with the Tax Act, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The remeasurement of the Company's deferred tax balance was primarily offset by application of its valuation allowance. As of December 31, 2018, the Company has completed its accounting for all of the tax effects of the enactment of the Tax Act, including the effects on its existing deferred tax balances. The Company has not recognized any material adjustment to the provisional estimate that was previously recorded related to the Tax Act.

A reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate is as follows for the years ended December 31, 2018 and 2017:


	Year Ended December 31,
	2018		2017
Federal income tax (benefit) at statutory rate	21.00	%	34.00	%
Permanent differences	(0.68)		(1.16)
Federal research and development credits and adjustments	4.25		2.36
State income tax, net of federal benefit	6.84		5.80
Tax reform deferred rate change	—		(72.21)
Other	(1.41)		(0.36)
Change in valuation allowance	(30.00)		31.57
Effective income tax rate	—	%	—	%

The Company's deferred tax assets consisted of the following (in thousands):



	Year Ended December 31,
	2018		2017
Deferred tax assets
Net operating loss carryforwards	$	48,107	$	41,436
Tax credit carryforwards		7,174		5,896
Capitalized research and development		1,394		1,879
Capitalized legal expenses		1,132		1,156
Other differences		1,370		1,048
Total deferred tax assets		59,177		51,415
Valuation allowance		(59,177)		(51,415)
Net deferred tax assets	$	—	$	—

The Company recorded an increase to the valuation allowance of $7.8 million during the year ended December 31, 2018 due primarily to the federal and state net operating losses and tax credits generated.The Company recorded a decrease to the valuation allowance of $8.4 million during the year ended December 31, 2017 primarily due to the federal rate reduction from 34% to 21% as a result of the Tax Act.

In assessing the realizability of deferred tax assets, the Company considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which the temporary differences representing net future deductible amounts become deductible. Due to the Company's history of losses and expectation of future losses, the deferred tax assets were fully offset by a valuation allowance at December 31, 2018 and 2017.

As of December 31, 2018, the Company had approximately $176.3 million of federal and $175.4 million of state net operating loss respectively, which may be available to offset future taxable income. Federal net operating loss carryforwards of $150.5 million and state net operating loss carryforwards of $175.4 million will expire at various dates from 2023 through 2037, $25.8 million of the federal net operating loss carryforward can be carried forward indefinitely. The Company had approximately $5.6 million of federal and $2.0 million of state tax credit carryforwards available to reduce future tax liabilities as of December 31, 2018, which will expire at varying times through the year 2038.

The Internal Revenue Code of 1986, as amended (the “Code”), provides for a limitation of the annual use of net operating losses and other tax attributes (such as research and development tax credit carryforwards) following certain ownership changes (as defined by the Code) that could limit the Company's ability to utilize these carryforwards. At this time, the Company has not completed a study to assess whether an ownership change under Section 382 of the Code has occurred, or whether there have been multiple ownership changes since the Company's formation, due to the costs and complexities associated with such a study. The Company may have experienced various ownership changes, as defined by the Code, as a result of past financing transactions. Accordingly, the Company's ability to utilize the aforementioned carryforwards may be limited. Additionally, U.S. tax laws limit the time during which these carryforwards may be applied against future taxes. Therefore, the Company may not be able to take full advantage of these carryforwards for federal or state income tax purposes.

As of December 31, 2018 and 2017, the Company did not have any significant unrecognized tax benefits. The Company had not accrued interest or penalties related to uncertain tax positions.

The federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2015 through December 31, 2018. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state taxing authorities to the extent utilized in a future period.

Defined Contribution Benefit Plan	12 Months Ended
Defined Contribution Benefit Plan	Dec. 31, 2018
Defined Contribution Benefit Plan
Defined Contribution Benefit Plan	14. Defined Contribution Benefit Plan The Company sponsors a 401(k) retirement plan, in which substantially all of its full-time employees are eligible to participate. Participants may contribute a percentage of their annual compensation to this plan, subject to statutory limitations. The Company did not provide any contributions to this plan during the years ended December 31, 2018 or 2017.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events
Subsequent Events	15. Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence for certain estimates and to identify matters that require additional disclosure. Subsequent events have been evaluated as required. Sales Agreement Subsequent to December 31, 2018, the Company sold an aggregate of 353,746 shares of common stock pursuant to its current ATM program, at an average price of $5.96 per share, for gross proceeds of $2.1 million, resulting in net proceeds of $2.0 million after deducting sales commissions and offering expenses. On February 6, 2019, the Company sold 4,000,000 shares of the Company’s common stock, par value $0.001 per share, and accompanying warrants with an exercise price of $6.25 to purchase up to 2,000,000 shares of common stock, at a combined price to the public of $5.00 per unit (each unit consisting of one share of common stock and 0.5 of a warrant to purchase one share of common stock), for gross proceeds of approximately $20.0 million, and net proceeds of $18.5 million after deducting sales commissions and offering expenses.

Quarterly Financial Information (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information (unaudited)

Quarterly Financial Information (unaudited)

16. Quarterly Financial Information (unaudited, in thousands, except share and per share data)


	Three Months Ended
	March 31,		June 30,		September 30,		December 31,
	2018		2018		2018		2018
Operating expenses	$	7,639	$	6,636	$	6,008	$	6,088
Net loss		(7,652)		(6,479)		(5,679)		(6,060)
Net loss per share:
Basic and Diluted	$	(2.88)	$	(1.98)	$	(0.80)	$	(0.85)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted		2,655,584		3,272,877		7,103,841		7,115,507


	Three Months Ended
	March 31,		June 30,		September 30,		December 31,
	2017		2017		2017		2017
Revenue	$	—	$	—	$	250	$	250
Operating expenses		7,761		6,919		7,202		5,712
Net loss		(7,876)		(6,974)		(7,017)		(5,497)
Net loss per share:
Basic and Diluted	$	(4.13)	$	(3.20)	$	(3.11)	$	(2.37)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted		1,909,327		2,179,619		2,256,317		2,321,847

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

Use of Estimates

Off-Balance Sheet Risk and Concentrations of Credit Risk

Cash and Cash Equivalents and Restricted Cash


	December 31,
	2018		2017
Cash	$	4,390	$	2,781
Money market fund		5,956		13,588
Corporate debt securities		1,948		—
Reverse repurchase agreements		3,000		—
Total	$	15,294	$	16,369


	December 31,
	2018		2017
Cash and cash equivalents	$	15,294	$	16,369
Restricted cash		113		113
Total	$	15,407	$	16,482

Short-Term Investments

Fair Value of Financial Instruments

Property and Equipment

Impairment of Long-Lived Assets

Research and Development Expenses

Revenue Recognition

Stock-Based Compensation

The Company expenses restricted stock awards based on the fair value of the award on a straight-line basis over the associated service period of the award.


	Year Ended December 31,
	2018		2017
Research and development	$	673	$	784
General and administrative		1,098		1,223
Total	$	1,771	$	2,007

No related tax benefits were recognized for the years ended December 31, 2018 and 2017.

Grant Awards

Net Loss Per Share

The following Common Stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2018	2017
Stock options	433,389	283,277
Common stock warrants	4,202,449	2,454
	4,635,838	285,731

Income Taxes

Segment Information

Comprehensive Loss

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Schedule of cash and cash equivalents

Cash and cash equivalents consist of the following (in thousands):


	December 31,
	2018		2017
Cash	$	4,390	$	2,781
Money market fund		5,956		13,588
Corporate debt securities		1,948		—
Reverse repurchase agreements		3,000		—
Total	$	15,294	$	16,369

Schedule of reconciliation of cash, cash equivalents and restricted cash


	December 31,
	2018		2017
Cash and cash equivalents	$	15,294	$	16,369
Restricted cash		113		113
Total	$	15,407	$	16,482

Schedule of stock-based compensation expense


	Year Ended December 31,
	2018		2017
Research and development	$	673	$	784
General and administrative		1,098		1,223
Total	$	1,771	$	2,007

Schedule of anti-dilutive common stock equivalents excluded from calculation of diluted net loss per share


	Year Ended December 31,
	2018	2017
Stock options	433,389	283,277
Common stock warrants	4,202,449	2,454
	4,635,838	285,731

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Financial Instruments

Schedule of assets and liabilities measures at fair value on a recurring basis

Below is a summary of assets and liabilities measured at fair value on a recurring basis (in thousands):


	As of December 31, 2018
	Quoted Prices		Significant		Significant
	in Active		Observable		Unobservable
	Markets		Inputs		Inputs
	(Level 1)		(Level 2)		(Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	5,956	$	—	$	—	$	5,956
Corporate debt securities		—		1,948		—		1,948
Reverse repurchase agreements		—		3,000		—		3,000
Short-term investments:
Corporate debt securities		—		7,276		—		7,276
Reverse repurchase agreements		—		15,000		—		15,000
Total assets	$	5,956	$	27,224	$	—	$	33,180


	As of December 31, 2017
	Quoted Prices		Significant		Significant
	in Active		Observable		Unobservable
	Markets		Inputs		Inputs
	(Level 1)		(Level 2)		(Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	13,588	$	—	$	—	$	13,588
Total assets	$	13,588	$	—	$	—	$	13,588

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2018

Short-Term Investments

Summary of short-term investments securities

The following table summarizes the short-term investments held at December 31, 2018 (in thousands):


			Gross Unrealized		Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
December 31, 2018
Corporate debt securities	$	7,280	$	—	$	(4)	$	7,276
Reverse repurchase agreements		15,000		—		—		15,000
Total	$	22,280	$	—	$	(4)	$	22,276

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property and Equipment

Summary of property and equipment and related accumulated depreciation

Property and equipment and related accumulated depreciation were as follows (in thousands):


		December 31,
	Estimated Useful Life (Years)	2018		2017
Lab equipment	3	$	—	$	1,470
Computer equipment	3		100		165
Furniture and fixtures	5		75		77
Leasehold improvements	Lesser of useful life or remaining lease term		202		264
			377		1,976
Less accumulated depreciation and amortization			(321)		(1,655)
Total property and equipment, net		$	56	$	321

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Accrued Expenses

Schedule of components of accrued expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2018		2017
Accrued compensation	$	1,241	$	632
Accrued contracted research costs		680		1,357
Accrued professional fees		393		298
Accrued severence		109		—
Accrued franchise fee		168		—
Accrued other		172		145
Total	$	2,763	$	2,432

Commitments (Tables)

12 Months Ended

Dec. 31, 2018

Commitments

Schedule of future minimum payments under non-cancelable operating lease

Future minimum payments required under the non-cancelable operating lease as of December 31, 2018 are summarized as follows (in thousands):


Period Ending December 31,	Amount
2019		1,421
2020		721
Total minimum lease payments	$	2,142

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Reserved for Future Issuance

Schedule of Common Stock reserved for future issuance


	As of December 31,
	2018	2017
Warrants for the purchase of Common Stock	4,202,449	2,454
Options outstanding to purchase Common Stock	433,389	283,277
Options reserved to purchase Common Stock	877,917	83,739
Employee Stock Purchase Plan	76,011	52,365
Total	5,589,766	421,835

Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2018

Stock Incentive Plans

Summary of stock option activity


				Weighted
				Average
		Weighted-		Remaining	Aggregate
		Average Exercise		Contractual		Instrinsic Value
	Shares	Price		Term (years)	(in thousands)
Outstanding at December 31, 2017	283,277	$	45.42	7.75	$	216
Granted	213,384	$	9.84
Exercised	(291)	$	12.40
Cancelled or forfeited	(62,981)	$	37.64
Outstanding at December 31, 2018	433,389	$	29.05	7.97	$	—
Vested and Exercisable at December 31, 2018	168,566	$	50.91	6.31	$	—

Schedule of assumptions made based on the Black-Scholes option pricing model


	Year Ended December 31,
	2018				2017
Weighted-average expected volatility	73.7	-	76.9	%	76.1	-	81.9	%
Expected term (in years)	5.75	-	6.25		6.25	-	9.77
Risk-free interest rate	2.67	-	2.84	%	2.00	-	2.38	%
Expected dividend yield			0	%			0	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Taxes

Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate


	Year Ended December 31,
	2018		2017
Federal income tax (benefit) at statutory rate	21.00	%	34.00	%
Permanent differences	(0.68)		(1.16)
Federal research and development credits and adjustments	4.25		2.36
State income tax, net of federal benefit	6.84		5.80
Tax reform deferred rate change	—		(72.21)
Other	(1.41)		(0.36)
Change in valuation allowance	(30.00)		31.57
Effective income tax rate	—	%	—	%

Schedule of components of deferred tax assets

The Company's deferred tax assets consisted of the following (in thousands):



	Year Ended December 31,
	2018		2017
Deferred tax assets
Net operating loss carryforwards	$	48,107	$	41,436
Tax credit carryforwards		7,174		5,896
Capitalized research and development		1,394		1,879
Capitalized legal expenses		1,132		1,156
Other differences		1,370		1,048
Total deferred tax assets		59,177		51,415
Valuation allowance		(59,177)		(51,415)
Net deferred tax assets	$	—	$	—

Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information (unaudited)

Summary of unaudited quarterly results of operations

Quarterly Financial Information (unaudited, in thousands, except share and per share data)


	Three Months Ended
	March 31,		June 30,		September 30,		December 31,
	2018		2018		2018		2018
Operating expenses	$	7,639	$	6,636	$	6,008	$	6,088
Net loss		(7,652)		(6,479)		(5,679)		(6,060)
Net loss per share:
Basic and Diluted	$	(2.88)	$	(1.98)	$	(0.80)	$	(0.85)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted		2,655,584		3,272,877		7,103,841		7,115,507


	Three Months Ended
	March 31,		June 30,		September 30,		December 31,
	2017		2017		2017		2017
Revenue	$	—	$	—	$	250	$	250
Operating expenses		7,761		6,919		7,202		5,712
Net loss		(7,876)		(6,974)		(7,017)		(5,497)
Net loss per share:
Basic and Diluted	$	(4.13)	$	(3.20)	$	(3.11)	$	(2.37)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted		1,909,327		2,179,619		2,256,317		2,321,847

Organization and Operations - Liquidity (Details) $ / shares in Units, $ in Thousands					2 Months Ended	12 Months Ended
	Feb. 06, 2019 USD ($) $ / shares shares	Dec. 28, 2018	Jun. 19, 2018 USD ($) $ / shares shares	Jul. 16, 2016 USD ($)	Feb. 28, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 12, 2018 $ / shares
Common Stock
Additional common stock issued						$ 8,363	$ 8,036
Reverse stock split ratio (as a percent)		0.1
Minimum bid price requirement for continued listing on NASDAQ \| $ / shares								$ 1.00
Accumulated deficit						(197,304)	$ (171,434)
Cash, cash equivalents and short-term investments						$ 37,600
Common Stock
Common Stock
Number of shares issued \| shares						577,195	480,480
Additional common stock issued						$ 1
Common Stock \| Subsequent Events
Common Stock
Number of shares issued \| shares	4,000,000
Additional common stock issued	$ 20,000
Number of warrants issued \| shares	2,000,000
Warrants price (in dollars per unit) \| $ / shares	$ 5.00
Proceeds from public offering, net of issuance costs	$ 18,500				$ 20,500
Common Stock \| Cowen
Common Stock
Percentage of commission paid to underwriter based on proceeds from common stock				3.00%
Common Stock \| ATM
Common Stock
Number of shares issued \| shares						577,195
Share price (in dollars per share) \| $ / shares						$ 15.27
Additional common stock issued						$ 8,800
Proceeds from public offering, net of issuance costs						$ 8,400
Common Stock \| ATM \| Cowen \| Subsequent Events
Common Stock
Number of shares issued \| shares					353,746
Share price (in dollars per share) \| $ / shares					$ 5.96
Additional common stock issued					$ 2,100
Proceeds from public offering, net of issuance costs					$ 2,000
Common Stock \| First ATM Program \| Cowen
Common Stock
Remaining current sales agreement				$ 22,600
Common Stock \| June 2018 Financing \| Oppenheimer & Co. Inc
Common Stock
Number of shares issued \| shares			4,200,000
Share price (in dollars per share) \| $ / shares			$ 0.001
Additional common stock issued			$ 42,000
Number of warrants issued \| shares			4,200,000
Warrants price (in dollars per unit) \| $ / shares			$ 10.00
Proceeds from public offering, net of issuance costs			$ 38,900

Summary of Significant Accounting Polices - Cash and Cash Equivalents and Restricted Cash and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 15,294	$ 16,369
Restricted cash	113	113
Total	15,407	16,482	$ 23,709
Fair Value of Financial Instruments
Transfers of assets or liabilities between levels	0	0
Money market funds
Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	5,956	13,588
Corporate debt securities
Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	1,948
Reverse repurchase agreements
Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	3,000
Cash
Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 4,390	$ 2,781
Minimum \| Government Securities and Obligations \| Repurchase agreements
Fair Value of Financial Instruments
Percentage of investment amount to collateralized deposits value	102.00%

Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Stock-based compensation expense	$ 1,771	$ 2,007
Tax benefits recognized from stock-based compensation expense	0	0
Research and development
Stock-Based Compensation
Stock-based compensation expense	673	784
General and administrative
Stock-Based Compensation
Stock-based compensation expense	$ 1,098	$ 1,223

Summary of Significant Accounting Polices - Grant Awards (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Grants revenue	$ 0	$ 124,000
Grants utilized to offset related expenses	$ 8,000	$ 205,000

Summary of Significant Accounting Policies - Net Loss Per Share and Segment Information (Details)	12 Months Ended
	Dec. 31, 2018 segment shares	Dec. 31, 2017 shares
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	4,635,838	285,731
Segment Information
Number of operating segments \| segment	1
Stock options
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	433,389	283,277
Common stock warrants
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	4,202,449	2,454

Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents:
Cash and cash equivalents	$ 15,294	$ 16,369
Short-term investments:
Short-term investments	22,276	0
Money market funds
Cash and cash equivalents:
Cash and cash equivalents	5,956	13,588
Corporate debt securities
Cash and cash equivalents:
Cash and cash equivalents	1,948
Short-term investments:
Short-term investments	7,276
Reverse repurchase agreements
Cash and cash equivalents:
Cash and cash equivalents	3,000
Short-term investments:
Short-term investments	15,000
Recurring
Assets:
Total assets	33,180	13,588
Recurring \| Money market funds
Cash and cash equivalents:
Cash and cash equivalents	5,956	13,588
Recurring \| Corporate debt securities
Cash and cash equivalents:
Cash and cash equivalents	1,948
Short-term investments:
Short-term investments	7,276
Recurring \| Reverse repurchase agreements
Cash and cash equivalents:
Cash and cash equivalents	3,000
Short-term investments:
Short-term investments	15,000
Recurring \| Level 1
Assets:
Total assets	5,956	13,588
Recurring \| Level 1 \| Money market funds
Cash and cash equivalents:
Cash and cash equivalents	5,956	$ 13,588
Recurring \| Level 2
Assets:
Total assets	27,224
Recurring \| Level 2 \| Corporate debt securities
Cash and cash equivalents:
Cash and cash equivalents	1,948
Short-term investments:
Short-term investments	7,276
Recurring \| Level 2 \| Reverse repurchase agreements
Cash and cash equivalents:
Cash and cash equivalents	3,000
Short-term investments:
Short-term investments	$ 15,000

Short-Term Investments (Details) $ in Thousands	12 Months Ended
Short-Term Investments (Details) $ in Thousands	Dec. 31, 2018 USD ($) instrument	Dec. 31, 2017 USD ($)
Short-Term Investments
Amortized Cost	$ 22,280
Gross Unrealized Losses	(4)
Fair Value	$ 22,276	$ 0
Number of short term investments in unrealized loss position \| instrument	7
Number of short term investments in an unrealized loss position more than 12 months \| instrument	0
Aggregate fair value of the investments in an unrealized loss position	$ 7,300
Corporate debt securities
Short-Term Investments
Amortized Cost	7,280
Gross Unrealized Losses	(4)
Fair Value	7,276
Reverse repurchase agreements
Short-Term Investments
Amortized Cost	15,000
Fair Value	$ 15,000

Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash
Security deposit held for operating lease agreement	$ 0.1	$ 0.1

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Property and equipment, gross	$ 377	$ 1,976
Less accumulated depreciation and amortization	(321)	(1,655)
Total property and equipment, net	56	321
Depreciation and amortization expense	$ 119	304
Lab equipment
Property and Equipment
Property and equipment, gross		$ 1,470
Estimated Useful Life	3 years	3 years
Computer equipment
Property and Equipment
Property and equipment, gross	$ 100	$ 165
Estimated Useful Life	3 years	3 years
Furniture and fixtures
Property and Equipment
Property and equipment, gross	$ 75	$ 77
Estimated Useful Life	5 years	5 years
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 202	$ 264

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Expenses
Accrued compensation	$ 1,241	$ 632
Accrued contracted research costs	680	1,357
Accrued professional fees	393	298
Accrued severance	109
Accrued franchise fee	168
Accrued other	172	145
Total	$ 2,763	$ 2,432

Notes Payable - (Details) - Credit Facility - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility
Total proceeds from issuance of promissory notes	$ 10.0
Interest expense	$ 0.1	$ 0.5

Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating leases
Rent expense			$ 1,100	$ 1,300
Future minimum payments required under the non-cancelable operating lease
2019				1,421
2020				721
Total minimum lease payments				$ 2,142
Amount of base rent from sub-lease	$ 500	$ 1,100
Sublease income			$ 300

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
Revenue Recognition (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2017
Revenue recognition
Quarterly payments					$ 500
Revenue recognized related to a Option agreement	$ 250	$ 250	$ 0	$ 500
Option agreement
Revenue recognition
Remaining performance obligation	$ 0			0
Revenue recognized related to a Option agreement				$ 500

Stockholders' Equity - Preferred Stock (Details)	12 Months Ended
Stockholders' Equity - Preferred Stock (Details)	Dec. 31, 2018 series $ / shares shares	Dec. 31, 2017 $ / shares shares
Preferred Stock
Preferred stock, authorized (in Shares)	5,000,000	5,000,000
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Preferred Stock, shares issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Minimum number of series used to issue preferred stock \| series	1

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	1 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018
Convertible Preferred Stock
Number of shares after conversion of issued warrants (in shares)		2,454
June 2018 common stock warrants
Convertible Preferred Stock
Number of warrants issued	4,200,000
Exercise price of warrants (in dollars per share)	$ 12.00
Warrants term	5 years
Weighted average remaining contractual life		4 years 5 months 19 days
Initial public offering \| Credit Facility
Convertible Preferred Stock
Number of shares after conversion of issued warrants (in shares)		122.12
Weighted average contractual life		2 years 11 months 12 days

Stockholders' Equity - Common Stock (Details)	12 Months Ended
Stockholders' Equity - Common Stock (Details)	Dec. 31, 2018 Vote $ / shares shares	Dec. 31, 2017 $ / shares shares
Common Stock
Common stock, authorized (in shares)	150,000,000	150,000,000
Par value of common stock (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Common stock, issued (in shares)	7,141,996	2,364,526
Common Stock, outstanding (in shares)	7,141,996	2,364,526
Number of votes entitled to each common stock share \| Vote	1
Common stock dividends, declared or paid (in dollars per share) \| $ / shares	$ 0
Shares reserved for future issuance (in shares)	5,589,766	421,835
Common stock warrants
Common Stock
Shares reserved for future issuance (in shares)	4,202,449	2,454
Common stock options outstanding
Common Stock
Shares reserved for future issuance (in shares)	433,389	283,277
Common stock options reserved
Common Stock
Shares reserved for future issuance (in shares)	877,917	83,739
Employee Stock Purchase Plan
Common Stock
Shares reserved for future issuance (in shares)	76,011	52,365

Stock Incentive Plans - Plan Information and Valuation Assumptions (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Shares reserved for future issuance (in shares)	5,589,766	421,835
2015 Plan
Stock-Based Compensation
Shares reserved for future issuance (in shares)	1,245,719
Shares available for future issuance (in shares)	877,917
2008 Plan
Stock-Based Compensation
Shares reserved for future issuance (in shares)	65,587
Shares available for future issuance (in shares)	0
Stock options
Stock-Based Compensation
Vesting period	4 years
Cliff period for vesting	1 year
Exercisable period	10 years

Stock Incentive Plans - Stock Option Plan Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Stock options
Outstanding at beginning of year (in shares)	283,277
Granted (in shares)	213,384
Exercised (in shares)	(291)
Cancelled or forfeited (in shares)	(62,981)
Outstanding at end of year (in shares)	433,389	283,277
Vested and Exercisable to vest at end of year (in shares)	168,566
Weighted-Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 45.42
Granted (in dollars per share)	9.84
Exercised (in dollars per share)	12.40
Cancelled or forfeited (in dollars per share)	37.64
Outstanding at end of year (in dollars per share)	29.05	$ 45.42
Vested and Exercisable at end of year (in dollars per share)	$ 50.91
Weighted Average Remaining Contractual Term (years)
Outstanding at end of year	7 years 11 months 19 days	7 years 9 months
Vested and Exercisable at end of year	6 years 3 months 22 days
Aggregate Intrinsic Value
Outstanding at the beginning of the year	$ 216
Outstanding at the end of the year		$ 216
Weighted average of the assumptions used to compute employee stock based compensation
Expected dividend yield (as a percent)	0.00%	0.00%
Stock options
Unrecognized stock-based compensation expense
Intrinsic value of options exercised	$ 1	$ 40
Adjusted fair value of options vested	$ 1,700	$ 2,200
Weighted average grant date fair value of options granted (in dollars per share)	$ 6.64	$ 8.48
Unrecognized compensation expense related to unvested stock option awards	$ 2,300
Weighted-average amortization period over which cost is expected to be recognized	1 year 8 months 12 days
Minimum
Weighted average of the assumptions used to compute employee stock based compensation
Weighted-average expected volatility (as a percent)	73.70%	76.10%
Expected term (in years)	5 years 9 months	6 years 3 months
Risk-free interest rate (as a percent)	2.67%	2.00%
Maximum
Weighted average of the assumptions used to compute employee stock based compensation
Weighted-average expected volatility (as a percent)	76.90%	81.90%
Expected term (in years)	6 years 3 months	9 years 9 months 7 days
Risk-free interest rate (as a percent)	2.84%	2.38%

Stock Incentive Plans - Employee Stock Purchase Plan (Details) - shares	1 Months Ended
	Jun. 30, 2015	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Common Stock, Issued, (in shares)		7,141,996	2,364,526
Common Stock \| 2015 ESPP
Stock-Based Compensation
Common Stock, Issued, (in shares)		0
Shares available for grant (in shares)	18,235
Common Stock \| 2015 ESPP \| Annual minimum increase
Stock-Based Compensation
Percentage of outstanding Common Stock available for issuance (as a percent)	1.00%
Potential increase in shares available for issuance as determined by the Board of Directors (in shares)	36,470

Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of the U.S. statutory income tax rate to the effective income tax rate
Federal income tax (benefit) at statutory rate	21.00%	34.00%
Permanent differences	(0.68%)	(1.16%)
Federal research and development credits and adjustments	4.25%	2.36%
State income tax benefit, net of federal benefit	6.84%	5.80%
Tax reform deferred rate change		(72.21)
Other (as a percent)	(1.41%)	(0.36%)
Change in valuation allowance	(30.00%)	31.57%
Deferred tax assets
Net operating loss carryforwards	$ 48,107	$ 41,436
Tax credit carryforwards	7,174	5,896
Capitalized research and development	1,394	1,879
Capitalized legal expenses	1,132	1,156
Other differences	1,370	1,048
Total deferred tax assets	59,177	51,415
Valuation allowance	(59,177)	(51,415)
Valuation allowance
Recorded increase (decrease) in valuation allowance	7,800	$ (8,400)
Federal
Valuation allowance
Net operating loss	176,300
Net operating loss carryforwards that will expire from 2023 through 2037	150,500
Net operating loss carryforwards, carried forward indefinitely	25,800
Tax credit carryforwards	5,600
State
Valuation allowance
Net operating loss	175,400
Net operating loss carryforwards that will expire from 2023 through 2037	175,400
Tax credit carryforwards	$ 2,000

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands		2 Months Ended	12 Months Ended
	Feb. 06, 2019	Feb. 28, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Events
Par value of common stock (in dollars per share)			$ 0.001	$ 0.001
Additional common stock issued			$ 8,363	$ 8,036
Subsequent Events
Subsequent Events
Common stock per unit	1
Warrants per common stock	0.5
Common Stock
Subsequent Events
Number of shares issued			577,195	480,480
Additional common stock issued			$ 1
Common Stock \| Subsequent Events
Subsequent Events
Number of shares issued	4,000,000
Proceeds from public offering, net of issuance costs	$ 18,500	$ 20,500
Par value of common stock (in dollars per share)	$ 0.001
Exercise price of warrants (in dollars per share)	$ 6.25
Number of warrants issued	2,000,000
Warrants price (in dollars per unit)	$ 5.00
Additional common stock issued	$ 20,000
ATM \| Common Stock
Subsequent Events
Number of shares issued			577,195
Share price (in dollars per share)			$ 15.27
Proceeds from public offering, net of issuance costs			$ 8,400
Additional common stock issued			$ 8,800
ATM \| Cowen \| Common Stock \| Subsequent Events
Subsequent Events
Number of shares issued		353,746
Share price (in dollars per share)		$ 5.96
Proceeds from public offering, net of issuance costs		$ 2,000
Additional common stock issued		$ 2,100

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information (Unaudited)
Revenue					$ 250	$ 250			$ 0	$ 500
Operating expenses	$ 6,088	$ 6,008	$ 6,636	$ 7,639	5,712	7,202	$ 6,919	$ 7,761	26,371	27,594
Net loss	$ (6,060)	$ (5,679)	$ (6,479)	$ (7,652)	$ (5,497)	$ (7,017)	$ (6,974)	$ (7,876)	$ (25,870)	$ (27,364)
Net loss per share:
Basic and Diluted (in dollars per share)	$ (0.85)	$ (0.80)	$ (1.98)	$ (2.88)	$ (2.37)	$ (3.11)	$ (3.20)	$ (4.13)	$ (5.12)	$ (12.62)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted (in shares)	7,115,507	7,103,841	3,272,877	2,655,584	2,321,847	2,256,317	2,179,619	1,909,327	5,054,823	2,168,153

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details