Stockholders’ Equity Common Stock (Tables)

3 Months Ended

Mar. 31, 2016

The following table summarizes the Company’s stock option activity since December 31, 2015:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2015		5,026,246		$	8.01		8.70	$	136,945
Granted		992,625			27.52
Exercised		(136,685	)		1.15
Forfeited		—			—
Outstanding as of March 31, 2016		5,882,186		$	11.46		8.68	$	93,314
Options exercisable as of March 31, 2016		1,892,915		$	2.66		8.05	$	45,250
Options vested and expected to vest as of March 31, 2016		5,756,568		$	11.34		8.67	$	91,974

Summary of Stock Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options and restricted common stock in the following expense categories of its consolidated statements of operations and comprehensive loss:

	Three Months Ended March 31,
	2016		2015
Research and development expenses	$	2,186	$	623
General and administrative expenses		1,718		704
	$	3,904	$	1,327