Annual report pursuant to Section 13 and 15(d)

Subsequent Events - Additional Information (Details)

v3.20.1
Subsequent Events - Additional Information (Details)
1 Months Ended 12 Months Ended
Feb. 28, 2020
USD ($)
Installment
$ / shares
shares
Mar. 20, 2020
USD ($)
Dec. 31, 2019
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Subsequent Event      
Subsequent Event [Line Items]      
Warrant to purchase stock | shares 81,257    
Exercise price per share | $ / shares $ 9.23    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term A Loan | Subsequent Event      
Subsequent Event [Line Items]      
Term loan maximum borrowing capacity $ 25,000,000.0    
Borrowed amount 25,000,000.0    
Repayment of outstanding principal amount $ 9,600,000    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term Loans      
Subsequent Event [Line Items]      
Payment terms, description     The Term Loans mature on March 1, 2024 (the “Maturity Date”) and will be interest-only through March 1, 2022, followed by 24 equal monthly payments of principal and interest.
Description of interest charges on loan     The Term Loans will bear interest at a floating per annum rate equal to the greater of (i) 8.07% or (ii) the sum of (a) the greater of (1) the thirty (30) day U.S. LIBOR rate reported in the Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue or (2) 1.67%, plus (b) 6.40%
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term Loans | Subsequent Event      
Subsequent Event [Line Items]      
Debt instrument, maturity date Mar. 01, 2024    
Number of monthly installments | Installment 24    
Interest-only payments, maturity date Mar. 01, 2022    
Floor percent of 30 days LIBOR 1.67%    
Final payment fee percentage 3.83%    
Principal amount Prepayment amount percentage to be paid before first anniversary 3.00%    
Principal amount Prepayment amount percentage to be paid between first and second anniversary 2.00%    
Principal amount Prepayment amount percentage to be paid to be paid thereafter and prior to maturity 1.00%    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term Loans | Subsequent Event | Floating Rate      
Subsequent Event [Line Items]      
Interest charges on loan 8.07%    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term Loans | Subsequent Event | LIBOR      
Subsequent Event [Line Items]      
Interest charges on loan 6.40%    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term Loans | Subsequent Event | Maximum      
Subsequent Event [Line Items]      
Additional borrowing amount $ 5,000,000.0    
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | Term B Loan | Subsequent Event | Minimum      
Subsequent Event [Line Items]      
Upfront payment received $ 50,000,000.0    
First Cytokine-Derivative Program | 2018 Merck Agreement | Scenario Forecast      
Subsequent Event [Line Items]      
Upfront payment received   $ 5,000,000.0  
Extended research term   1 year