Common Stock Reserved for Issuance (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

The common stock reserved for future issuance at December 31, 2017 and 2016 was as follows:

	December 31,
	2017		2016
Shares underlying outstanding stock options		8,592,747		6,127,291
Shares available for future stock option grants		969,783		2,168,391
Shares issuable upon settlement of restricted    stock units outstanding		149,636		151,240
ESPP shares available for issuance		1,103,481		667,670
Warrant to purchase common stock		3,393,755		1,707,736
Total shares of common stock reserved		14,209,402		10,822,328