Common Stock (Tables)

12 Months Ended

Dec. 31, 2017

Common Stock

Schedule of shares reserved for future issuance

	As of December 31,
	2017	2016
Shares reserved for outstanding stock option awards under the 2013 Stock Incentive Plan, as amended	1,220,567	1,595,082
Shares reserved for outstanding stock option awards under the 2015 Stock Incentive Plan	2,921,987	1,569,746
Shares reserved for outstanding inducement stock option award	225,000	—
Remaining shares reserved, but unissued, for future awards under the 2015 Stock Incentive Plan	2,502,338	2,760,472
Remaining shares reserved, but unissued, for future awards under the 2015 Employee Stock Purchase Plan	751,242	384,615
	7,621,134	6,309,915