Organization and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

Fair Value Hierarchy of Warrant Liabilities

The following table presents the Company’s fair value hierarchy for its warrant liabilities measured at fair value on a recurring basis (in thousands) as of September 30, 2017 and December 31, 2016:

	Quoted  Market  Prices for Identical Assets (Level 1)		Significant  Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Total
Warrant liabilities
Balance as of September 30, 2017	$	—	$	—	$	636	$	636
Balance as of December 31, 2016	$	—	$	—	$	846	$	846

Assumptions Used in Determining the Fair Value of Warrant Liabilities

The following assumptions were used in determining the fair value of the common stock warrant liabilities valued using the Black-Scholes option pricing model as of September 30, 2017 and December 31, 2016:

	September 30, 2017			December 31, 2016
Risk-free interest rate	1.93%-1.94%			1.64%-1.99%
Volatility	87.72%-88.33%			77.25%-81.03%
Dividend yield	—		%	—		%
Expected term	5.29-5.42			4.75-6.17
Weighted average fair value	$	0.73		$	0.49

Reconciliation of Liabilities Measured at Fair Value using Level 3 Unobservable Inputs

The following table is a reconciliation for all liabilities measured at fair value using Level 3 unobservable inputs (in thousands):

	Warrant liabilities
Balance as of December 31, 2016	$	846
Change in fair value measurement of warrant liability	588
Warrant liability reclassified to stockholders' equity	(798		)
Balance as of September 30, 2017	$	636

Anti-Dilutive Securities Excluded in the Determination of Diluted Income (Loss) Per Share

The following securities that could potentially decrease net income (loss) per share in the future are not included in the determination of diluted income (loss) per share as their effect is anti-dilutive (in thousands):

	As of September 30,
	2017	2016
Outstanding stock options	391	490
Outstanding warrants	7,270	2,318
Restricted stock	721	116

Assumptions Used to Estimate the Fair Value of Stock Option Grants

The table below presents the weighted average assumptions used by the Company to estimate the fair value of stock option grants using the Black-Scholes option-pricing model, as well as the resulting weighted average fair values at their issuance dates during the nine months ended September 30, 2016. No stock options were granted during the first nine months of 2017.

	September 30, 2016
Risk-free interest rate	1.36%-1.78%
Volatility	72.35%-80.02%
Dividend yield	—		%
Expected term	5.25-6.08 years
Forfeiture rate	11.33		%
Weighted average grant date fair value	$	7.23

Summary of Stock Option Activity

A summary of the Company’s stock option activity under its stock option plans during the nine months ended September 30, 2017 is as follows (share amounts in thousands):

	Number of Shares		Weighted Average Exercise Price
Outstanding as of December 31, 2016	415		$	17.23
Cancelled	(24	)	$	15.32
Outstanding as of September 30, 2017	391		$	17.34

Summary of Restricted Stock Unit Activity

A summary of the Company’s restricted stock unit activity under its stock option plans during the nine months ended September 30, 2017 is as follows (share amounts in thousands):

	Number of Shares		Weighted Average Grant Date Fair Value
Unvested as of December 31, 2016	115		$	5.11
Granted	873		$	1.13
Vested	(211	)	$	1.70
Forfeited	(56	)	$	1.45
Unvested as of September 30, 2017	721		$	1.57

Summary of Stock-Based Compensation Expense from Share-Based Awards

The following table summarizes the total stock-based compensation expense resulting from share-based awards recorded in the Company’s condensed consolidated statements of operations (in thousands):

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2017		2016		2017		2016
Research and development	$	57	$	54	$	193	$	479
General and administrative	275		279		710		948
Total	$	332	$	333	$	903	$	1,427