Quarterly Results (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Results

	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
	2017			2017			2017			2017
	(in thousands, except per share data)
	(unaudited)
Collaboration revenue	$	20,865		$	28,520		$	41,283		$	87,316
Operating expenses	$	65,837		$	50,656		$	65,459		$	75,949
Loss from operations	$	(44,972	)	$	(22,136	)	$	(24,176	)	$	11,367
Other income, net	$	429		$	618		$	1,042		$	914
Net (loss)/income	$	(44,543	)	$	(21,518	)	$	(23,134	)	$	12,281
Net (loss)/income per share:
basic	$	(1.15	)	$	(0.53	)	$	(0.49	)	$	0.26
diluted	$	(1.15	)	$	(0.53	)	$	(0.49	)	$	0.25
Weighted-average number of common shares:
basic		38,759,221			40,819,957			46,938,618			47,353,166
diluted		38,759,221			40,819,957			46,938,618			49,719,548
	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
	2016			2016			2016			2016
	(in thousands, except per share data)
	(unaudited)
Collaboration revenue	$	—		$	—		$	—		$	1,535
Operating expenses	$	26,046		$	36,188		$	36,182		$	39,579
Loss from operations	$	(26,046	)	$	(36,188	)	$	(36,182	)	$	(38,044	)
Other income (expense), net	$	248		$	409		$	(126	)	$	182
Net loss	$	(25,798	)	$	(35,779	)	$	(36,308	)	$	(37,862	)
Net loss per share —basic and diluted	$	(0.70	)	$	(0.95	)	$	(0.96	)	$	(0.99	)