Description of Business and Basis of Presentation - Reverse Stock Split and Going Concern (Details)				1 Months Ended		12 Months Ended
	Aug. 30, 2018 USD ($) $ / shares shares	Aug. 16, 2018 USD ($) $ / shares shares	Aug. 03, 2018 shares	Sep. 30, 2019 USD ($)	Jul. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Description of Business and Basis of Presentation
Cash and cash equivalents						$ 20,897,000	$ 24,237,000
Accumulated deficit						100,769,000	71,088,000
Proceeds from issuance of common stock, net						4,958,000	$ 25,079,000
License Agreement with SIBV
Description of Business and Basis of Presentation
Upfront payment received					$ 5,000,000
License Agreement with SAMR
Description of Business and Basis of Presentation
Upfront payment received				$ 15,000,000	$ 5,000,000	$ 42,500,000
Common Stock
Description of Business and Basis of Presentation
Ratio of reverse stock split			0.155814
Conversion of Series A convertible preferred stock into common stock upon initial public offering (in shares) | shares			5,744,586
IPO
Description of Business and Basis of Presentation
other offering expenses		$ 1,400,000
Proceeds from issuance of common stock, gross	$ 2,500,000	26,000,000
Proceeds from issuance of common stock, net	$ 2,300,000	$ 22,800,000
IPO | Common Stock
Description of Business and Basis of Presentation
Issuance of common stock (in shares) | shares	192,824	2,000,000
Share Price | $ / shares	$ 13.00	$ 13.00
IPO | IPO
Description of Business and Basis of Presentation
underwriting discounts and commissions	$ 175,000	$ 1,800,000