License Agreements - Additional Information (Details) - Novartis International Pharmaceutical Ltd. - License Agreement - USD ($)	1 Months Ended	9 Months Ended
	May 31, 2017	Sep. 30, 2018	Mar. 23, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement termination description		The agreement may be terminated by either party upon a material breach by the other party that is not cured within 60 days after written notice. The Company may terminate the agreement in its entirety or on a product-by-product or country-by-country basis with or without cause with 60 days’ prior written notice.
Milestone payment	$ 300,000
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount payable upon satisfaction of clinical milestones			$ 4,300,000
Aggregate amount payable upon satisfaction of regulatory milestones for first indication approved			24,000,000
Aggregate amount payable upon satisfaction of regulatory milestones for second indication approved			18,000,000
Aggregate amount payable upon satisfaction of commercial milestones			$ 125,000,000
Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued			2,587,992
Fair value of license agreement			$ 3,200,000
Fair value of shares issued			$ 1.22