Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (49,077)	$ (45,520)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	141	123
Stock-based compensation expense	3,311	2,875
Amortization of debt issuance costs	36	44
Gain on disposal of assets	0	(17)
Non-cash interest expense on investments	83	119
Issuance of common stock in consideration for rights granted under collaboration agreement	17,989	23,968
Changes in operating assets and liabilities:
Accounts receivable	249	(357)
Prepaid expenses and other assets	(265)	(339)
Accounts payable and accrued and other liabilities	1,109	76
Total adjustments	22,653	26,492
Net cash used in operating activities	(26,424)	(19,028)
Cash flows from investing activities:
Purchase of investments	(50,485)	(95,595)
Sale of investments	66,816	73,521
Purchases of property and equipment	(269)	(48)
Decrease in restricted cash	0	14
Proceeds from sale of equipment	0	19
Net cash provided by/(used in) investing activities	16,062	(22,089)
Cash flows from financing activities:
Proceeds from issuance of common stock associated with offerings, net of issuance costs	0	64,619
Proceeds from issuance of common stock under the Company’s share-based compensation plans	1,161	203
Payments on Curis Royalty’s debt	(3,219)	(2,793)
Net cash (used in)/provided by financing activities	(2,058)	62,029
Net (decrease)/increase in cash and cash equivalents	(12,420)	20,912
Cash and cash equivalents, beginning of period	33,091	7,747
Cash and cash equivalents, end of period	$ 20,671	$ 28,659