Stock award plan (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of stock option activity

A summary of stock option activity is as follows:

	Number of options		Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value
						(in thousands)
Outstanding at December 31, 2016	5,854,316		$	34.71
Granted	1,809,873		$	12.12
Exercised	(132,795	)	$	10.82
Forfeited/Cancelled	(918,629	)	$	33.20
Outstanding at September 30, 2017	6,612,765		$	29.21	7.43 years	$	22,786
Vested or Expected to vest at September 30, 2017	2,719,750		$	24.50	8.59 years	$	11,858
Exercisable at September 30, 2017	3,718,713		$	33.07	6.51 years	$	10,014

Schedule of assumptions used to estimate fair values of grants made on the date of grant

The fair value of grants made in the nine months ended September 30, 2017 was contemporaneously estimated on the date of grant using the following assumptions:

	Nine months ended September 30, 2017
Risk-free interest rate	1.84% — 2.45%
Expected volatility	76%—81%
Expected term	5.04– 10.00 years

Summary of information on the Company's restricted stock

The following table summarizes information on the Company’s restricted stock awards and units:

	Restricted Stock Awards and Units
	Number of Shares		Weighted Average Grant Date Fair Value
January 1, 2017	271,651		$	19.76
Granted	363,194		$	11.64
Vested	(180,861	)	$	14.19
Forfeited	(51,131	)	$	13.90
Unvested at September 30, 2017	402,853		$	15.62

Schedule of share-based compensation expense recorded in the statement of operations

The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units and the ESPP as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	3,624	$	4,319	$	11,986	$	12,734
Selling, general and administrative	3,544		4,640		12,096		13,876
Total	$	7,168	$	8,959	$	24,082	$	26,610