Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Schedule of weighted-average assumptions used to estimate grant date fair value of stock options

The weighted-average assumptions used to estimate grant date fair value of stock options using the Black-Scholes option pricing model were as follows for the three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,		Six Months Ended June 30,
	2018	2017	2018	2017
Expected common stock price volatility	85%	82%	83%	81%
Risk-free interest rate	2.83%-2.83%	1.82%-1.95%	2.39%-2.83%	1.82%-2.38%
Expected term of options (years)	5.3	5.7	5.6	6.1
Expected dividend yield	—	—	—	—

Schedule of share-based compensation expense

Share-based compensation expense includes expenses related to stock options and RSUs granted to employees, non-employee directors and consultants, as well as options granted to employees to purchase shares under the ESPP, all of which have been reported in the Company’s Statements of Operations as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development	$	1,106	$	2,897	$	2,546	$	7,047
General and administrative	1,556		2,091		3,198		4,005
Total	$	2,662	$	4,988	$	5,744	$	11,052