Common stock (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Restricted common stock activity

The following is a summary of restricted common stock activity:

	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2014	3,218,590		$	0.10
Issued	—
Vested	(1,016,328	)	0.10
Forfeited	—		—
Non-vested at December 31, 2015	2,202,262		$	0.10

Shares reserved for future issuance

The Company has reserved the following number of shares of common stock for future issuance:

	As of December 31,
	2015	2014
Vesting of restricted common stock	2,202,262	3,218,590
Stock-based compensation awards	2,031,528	1,189,314
Employee stock purchase plan	175,131	—
Conversion of Series A Preferred Stock	—	3,683,637
Conversion of Series B Preferred Stock	—	3,287,471
Total	4,408,921	11,379,012