Common Stock (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Common Stock for future issuance
Proceeds from issuance of common stock, net		$ 4,958,000	$ 25,079,000
Total common stock for future issuance		3,310,616
License Agreement and Option Agreement
Common Stock for future issuance
Proceeds from sale of restricted common stock and upfront payment		$ 22,500,000
Deferred revenue		19,600,000
Deferred revenue based on upfront payments		15,000,000
Deferred revenue from equity allocation		4,600,000
Capitalized contract costs		2,100,000
Issuance costs from equity allocation		441,000
Direct costs related to license agreement		1,700,000
Fair value of net proceeds		5,000,000
Fair value of gross proceeds		$ 5,400,000
Maximum
Common Stock for future issuance
Valuation (term of years)			9 years 8 months 12 days
Options
Common Stock for future issuance
Valuation (term of years)		6 years 3 months
Dividend yield (in percent)		0.00%	0.00%
Shares reserved for issuance of future options		196,982
Total common stock for future issuance		1,380,312
Serum International B.V. ("SIBV")
Common Stock for future issuance
Issuance of common stock (in shares)	801,820
Issuance of common stock	$ 10,000,000
Serum International B.V. ("SIBV") | Restricted common stock
Common Stock for future issuance
Issuance of common stock (in shares)	801,820
Issuance of common stock	$ 10,000,000
Commission payment	816,000
Proceeds from issuance of common stock, net	$ 9,200,000
Expected volatility		84.00%
Risk-free interest-rate		1.94%
Dividend yield (in percent)		0.00%
ATM Agreement
Common Stock for future issuance
Maximum aggregate offering price				$ 25,000,000
Maximum value of shares under prospectus supplement covering				$ 100,000,000
Warrants
Common Stock for future issuance
Total common stock for future issuance		1,733,322