Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating Activities
Net loss	$ (26,944)	$ (26,282)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and other expense	83	94
Gain on sale of property and equipment	(150)	0
Deferred income taxes	0	233
Share-based compensation	4,677	5,744
Changes in operating assets and liabilities:
Income tax receivable	(1)	1,387
Prepaid expense and other current assets	299	1,227
Other assets	3	(7)
Accrued research and development expenses	308	153
Accounts payable and accrued expenses	(2,628)	(3,557)
Net cash used in operating activities	(24,353)	(21,008)
Investing Activities
Net cash provided by (used in) investing activities	0	0
Financing Activities
Proceeds from employee stock plan purchases	41	27
Net cash provided by financing activities	41	27
Net change in cash and cash equivalents	(24,312)	(20,981)
Cash and cash equivalents
Beginning of period	131,201	166,972
End of period	106,889	145,991
Supplemental disclosure of cash paid
Income tax refunds received	$ 0	$ 2,467