Condensed Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues
Total revenues	$ 936	$ 943	$ 2,751	$ 5,535
Operating expenses:
Research and development	11,761	11,950	33,732	37,860
General and administrative	4,523	3,782	14,419	7,853
Total operating expenses	16,284	15,732	48,151	45,713
Loss from operations	(15,348)	(14,789)	(45,400)	(40,178)
Other income	558	608	1,768	990
Net loss and comprehensive loss	$ (14,790)	$ (14,181)	$ (43,632)	$ (39,188)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.44)	$ (0.43)	$ (1.30)	$ (2.48)
Weighted-average number of common shares outstanding, basic and diluted (in shares)	33,646	33,191	33,510	15,789
Collaboration revenue
Revenues
Total revenues	$ 936	$ 943	$ 2,751	$ 3,893
Grant revenue
Revenues
Total revenues				$ 1,642

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