Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Summary of Allocated Stock-based Compensation Expense

The Company’s stock-based compensation expense is allocated between research and development and selling, general and administrative as follows:

Stock-based compensation expense	2018		2017
Research and development	$	1,052	$	401
Selling, general and administrative	$	1,869	$	2,669

Key Assumptions Used in Determining Fair Value of Options Granted

The key assumptions used in determining the fair value of options granted during the three months ended March 31, 2018 follows:

Expected price volatility	60.41%-68.77%
Risk-free interest rate	2.05%-2.60%
Weighted average expected life in years	6 years
Dividend yield	—

Summary of Stock Option Activity

Option activity during the three months ended March 31, 2018 was as follows:

	Number of shares			Weighted average exercise price per share		Aggregate intrinsic value
Outstanding at January 1, 2018		2,712,954		$	2.98	$	1,190
Granted in 2018:
Employees		618,174			2.50
Exercised		(63,295	)		2.05
Forfeitures		(201,989	)		4.64
Outstanding at March 31, 2018		3,065,844		$	2.80	$	292

Summary of Restricted Stock Activity

Restricted stock activity during the three months ended March 31, 2018 was as follows:

	Number of restricted shares			Weighted average fair market value per RSU
Outstanding at January 1, 2018		4,706,895		$	5.20
Granted:
Executive officers		463,129			2.10
Directors		375,305			2.18
Employees		317,177			2.10
Vested		(1,038,957	)		2.35
Forfeitures		(235,110	)		2.52
Conversions		(1,640,198	)		2.68
Outstanding at March 31, 2018		2,948,241		$	3.02