Common Stock (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Schedule of shares reserved for future issuance

The Company has reserved the following shares of common stock:

	As of December 31,
	2018	2017
Unvested restricted stock	—	4,430
Options to purchase common stock	5,942,884	3,879,535
Warrants to purchase common stock	9,257,632	10,055,000
Employee stock purchase plan	38,469	59,461
	15,238,985	13,998,426