Accounting for Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2016

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

Summary of Key Assumptions for Options Awarded

The Black-Scholes option pricing model employs the following key assumptions for employee and director options awarded during the nine months ended September 30, 2016 and 2015 based on the assumptions noted in the following table:

	Nine Months Ended   September 30,
	2016	2015
Expected life (years) - employees	6	6
Expected life (years) – officers and directors	7	7
Risk-free interest rate	1.4-1.8%	1.5-1.9%
Volatility	63-70%	68-70%
Dividends	None	None

Schedule of Recorded Stock-Based Compensation Expense

For the three and nine months ended September 30, 2016 and 2015, the Company recorded stock-based compensation expense to the following line items in its costs and expenses section of the condensed consolidated statements of operations and comprehensive loss, including expense related to its ESPP:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2016		2015		2016		2015
Research and development expenses	$	205	$	170	$	531	$	771
General and administrative expenses	1,425		731		2,780		2,104
Total stock-based compensation expense	$	1,630	$	901	$	3,311	$	2,875