Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net loss	$ (20,027)	$ (10,438)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	545	823
Non-cash interest expense	63	96
Stock-based compensation	1,180	1,436
Acquired in-process research and development	3,000	0
Provision for doubtful accounts	30	4
Gain on expiration of derivative liability	(5,520)	0
Loss on equity investments	499	0
Deferred tax provision	0	(178)
Changes in operating assets and liabilities:
Grants and other receivables	(273)	(56)
Prepaid expenses and other	140	90
Accounts payable	1,787	95
Deferred revenue	(12)	0
Accrued expenses and other liabilities	(1,598)	(719)
Net cash used for operating activities	(20,186)	(8,847)
Investing activities
Purchases of property and equipment	(596)	(343)
Investments in common stock	0	(1,500)
Net cash used in investing activities	(596)	(1,843)
Financing activities
Net principal payments under loan and security agreement	(1,204)	0
Net payments of deferred compensation	0	(1,000)
Proceeds from issuance of common stock	3,486	0
Proceeds from exercise of stock options	275	289
Net cash provided by (used in) financing activities	2,557	(711)
Net change in cash and cash equivalents	(18,225)	(11,401)
Cash and cash equivalents at beginning of period	39,038	71,902
Cash and cash equivalents at end of period	20,813	60,501
Cash paid during the period for:
Income taxes	1	0
Interest paid	307	248
Supplemental disclosures of non-cash investing and financing activities:
Change in unrealized gains or (losses) on marketable securities	(51,183)	0
Property and equipment costs incurred but not paid	$ 12	$ 135