CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (10,059)	$ (7,186)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	15	16
Accretion and amortization on investments, net	(482)	24
Change in fair value of equity investment, including foreign currency translation	(103)	125
Stock-based compensation for services by non-employees	22	71
Stock-based compensation for employees and directors	1,426	1,614
Amortization related to 401(k) contributions	9	10
Changes in assets and liabilities:
Current and noncurrent assets	(1,532)	89
Current liabilities	(2,034)	(2,131)
Net cash used in operating activities	(12,738)	(7,368)
Cash flows from investing activities:
Purchases of property and equipment	(45)
Purchases of marketable securities	(44,092)	(19,768)
Proceeds from maturities of marketable securities	53,101	17,160
Net cash provided by (used in) investing activities	8,964	(2,608)
Cash flows from financing activities:
Proceeds from issuances of common stock, net of issuance costs		1,553
Net cash provided by financing activities		1,553
Net decrease in cash, cash equivalents and restricted cash	(3,774)	(8,423)
Cash, cash equivalents and restricted cash at the beginning of the period	10,844	16,603
Cash, cash equivalents and restricted cash at the end of the period	$ 7,070	$ 8,180