Selected quarterly financial data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

	2016
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter		Total
	(in thousands, except per share data)
Collaboration revenue	$	4,830	$	3,720	$	3,308	$	2,362	$	14,220
Total operating expenses		12,297		13,338		13,679		16,205		55,519
Loss from operations		(7,467)		(9,618)		(10,371)		(13,843)		(41,299)
Net loss attributable to common shareholders		(7,188)		(9,335)		(8,996)		(14,674)		(40,193)
Net loss per share applicable to common stockholders – basic and diluted	$	(0.29)	$	(0.37)	$	(0.35)	$	(0.57)	$	(1.59)

	2015
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter		Total
	(in thousands, except per share data)
Collaboration revenue	$	2,576	$	4,884	$	4,937	$	4,937	$	17,334
Total operating expenses		7,404		8,851		8,956		12,377		37,588
Loss from operations		(4,828)		(3,967)		(4,019)		(7,440)		(20,254)
Net loss attributable to common shareholders		(15,813)		(6,746)		(6,914)		(8,817)		(38,290)
Net loss per share applicable to common stockholders – basic and diluted	$	(15.81)	$	(5.80)	$	(5.25)	$	(0.67)	$	(9.14)