Asset Acquisition - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 31, 2019	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
In-process research and development expenses			$ 25,591,000
GSK Agreement
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
Specified clinical and regulatory milestones phase two clinical trial			2,500,000
Direct expenses related to the transaction			100,000
Specified clinical and regulatory milestones phase two clinical trial achieved	$ 2,500,000
GSK Agreement | Research and Development
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
Clinical and regulatory milestone payables upon phase two clinical trial achieved		$ 2,500,000	2,500,000
GSK Agreement | Maximum
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
Specified clinical and regulatory milestones			37,500,000
Specified sales milestone			$ 60,000,000
Series B Convertible Preferred Stock
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
Shares issued, price per share				$ 2.00
Series B Convertible Preferred Stock | GSK Agreement
Research And Development Assets Acquired Other Than Through Business Combination [Line Items]
Shares issued for asset acquisition			12,500,000
Shares issued for asset acquisition, estimated fair value			$ 25,500,000
Shares issued, price per share		$ 2.04	$ 2.04