Common Stock (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule of shares reserved for future issuance

The Company has reserved the following shares of common stock:

	As of December 31,
	2017	2016
Unvested restricted stock	4,430	22,150
Restricted stock units	—	3,333
Options to purchase common stock	3,879,535	3,112,771
Warrants to purchase common stock	10,055,000	926,840
Employee stock purchase plan	59,461	68,609
	13,998,426	4,133,703