STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 0	$ 0
Operating expenses:
Research and development	25,385,000	25,508,000
General and administrative	11,812,000	9,357,000
Impairment loss	0	511,000
Total operating expenses	37,197,000	35,376,000
Loss from operations	(37,197,000)	(35,376,000)
Other income (expense):
Interest income	207,000	381,000
Interest expense	(523,000)	(379,000)
Other income (expense), net	(76,000)	16,000
Loss before provision for income taxes	(37,589,000)	(35,358,000)
Provision for income taxes	0	0
Net loss	(37,589,000)	(35,358,000)
Unrealized gain (loss) on marketable securities, net of tax	5,000	(5,000)
Comprehensive loss	$ (37,584,000)	$ (35,363,000)
Net loss per common share – basic and diluted (in USD per share)	$ (2.29)	$ (3.74)
Weighted-average common shares used in computing net loss per common share – basic and diluted (in shares)	16,383,730	9,452,491