CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (39,478)	$ (19,717)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	35	45
Accretion and amortization on investments, net	(1,283)	(521)
Change in fair value of equity investment, including foreign currency translation	212	338
Stock-based compensation for services by non-employees	50	155
Stock-based compensation for employees and directors	4,429	4,774
Amortization related to 401(k) contributions	9	10
Operating lease expense	504
Changes in assets and liabilities:
Current and noncurrent assets	(1,399)	(1,034)
Current liabilities	3,458	(2,049)
Net cash used in operating activities	(33,463)	(17,999)
Cash flows from investing activities:
Purchases of property and equipment	(324)	(9)
Purchases of marketable securities	(102,276)	(149,720)
Proceeds from maturities of marketable securities	137,013	71,163
Net cash provided by (used in) investing activities	34,413	(78,566)
Cash flows from financing activities:
Proceeds from issuances of common stock, net of issuance costs	9,227	92,960
Net cash provided by financing activities	9,227	92,960
Net increase (decrease) in cash, cash equivalents and restricted cash	10,177	(3,605)
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	$ 21,021	$ 12,998