Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2017

Equity [Abstract]

Summary of Stock Based Compensation Expense

Stock compensation expense (in thousands) was allocated between departments as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research & Development	$	61	$	41	$	97	$	74
Sales & Marketing	—		43		6		11
General & Administrative	382		134		525		269
Total	$	443	$	218	$	628	$	354

Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model

The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions for the three and six months ended June 30, 2017 and 2016:

	Three Months Ended June 30,		Six Months Ended June 30,
	2017	2016	2017	2016
Expected life (years)	5.78-6.08	5.5-10	5.5-6.08	5.5-6.08
Risk-free interest rate	1.9%-2.1%	1.3%-1.7%	1.9%-2.2%	1.3%-1.8%
Volatility	69%	65% - 73%	61%-69%	65% - 76%
Dividend rate	—%	—%	—%	—%

Summary of Stock Option Transactions

The following table summarizes stock option transactions for the six months ended June 30, 2017 as issued under the Plans:

	Shares Available for Grant		Number of Options Outstanding		Weighted-Average Exercise Price per Share		Weighted Average Remaining Contractual Term
							(in years)
Balance at January 1, 2017	958,856		2,908,430		$	3.42	8.48
Additional shares authorized	671,478		—
Amendment to plan to authorize additional shares	8,929,188		—
Options granted	(3,113,777	)	3,113,777		0.61
Options exercised	—		—
Options canceled/forfeited	108,191		(108,191	)	3.49
Balance at June 30, 2017	7,553,936		5,914,016		1.94		8.98
Options vested at June 30, 2017			2,503,001		$	2.91	8.37
Options vested and expected to vest at June 30, 2017			5,914,016		$	1.94	8.98