CONDENSED STATEMENT OF STOCKHOLDERS' EQUITY - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2017	$ 24	$ 712,165	$ (604,494)	$ 107,695
Beginning balance, shares at Dec. 31, 2017	24,453			24,453
Issuance of common stock under employee stock purchase plan		205		$ 205
Issuance of common stock under employee stock purchase plan, shares	18
Issuance of common stock upon exercise of common stock options and warrants	$ 3	10,163		10,166
Issuance of common stock upon exercise of common stock options and warrants, shares	2,702
Issuance of common stock for services rendered		77		77
Issuance of common stock for services rendered, shares	6
Stock-based compensation		4,454		4,454
Net loss			(47,731)	(47,731)
Ending balance at Sep. 30, 2018	$ 27	$ 727,064	$ (652,225)	$ 74,866
Ending balance, shares at Sep. 30, 2018	27,179			27,179