Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Additional Information (Details)

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Commitments and Contingencies - Additional Information (Details)
 1 Months Ended 3 Months Ended 9 Months Ended
May 31, 2020
USD ($)
Sep. 30, 2020
USD ($)
Faculty
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
Faculty
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Commitments and Contingencies [Line Items]            
Rent expense   $ 67,000 $ 67,000   $ 110,000  
Research and development expense   5,650,000 3,220,000 $ 15,601,000 8,645,000  
Manufacturing agreements, maximum amount committed   537,000   $ 537,000    
Operating Lease Agreement            
Commitments and Contingencies [Line Items]            
Operating lease, description       The lease term commenced in May 2019 and will expire in July 2022.    
Lease commencement period       2019-05    
Lease expiration period       2022-07    
Initial annual base rent       $ 261,000    
Percentage of annual increase of base rent       2.00%    
Rent expense       $ 200,000    
Research Service Agreement | Children's Hospital of Philadelphia            
Commitments and Contingencies [Line Items]            
Research and development expense   0 0 0 201,000  
Amounts due to agreement   0   0    
Penn Agreement            
Commitments and Contingencies [Line Items]            
Amounts due to agreement   0   0    
Obligation to be paid   2,000,000   $ 2,000,000    
Payment term       3 years    
Payment commencement date       2018-08    
License maintenance fee $ 33,000     $ 10,000    
Other amounts paid to agreement       0    
Total milestone payments       20,000,000    
Sponsored Research Agreements | Penn            
Commitments and Contingencies [Line Items]            
Research and development expense   624,000 710,000 1,960,000 2,131,000  
Obligation to be paid   $ 11,781,000   $ 11,781,000    
Number of faculty member | Faculty   2   2    
Funding term end date       2023-02    
Sponsored Research Agreements | Penn | Prepaid Expenses and Other Current Assets            
Commitments and Contingencies [Line Items]            
Advance payments   $ 1,232,000   $ 1,232,000   $ 1,588,000
Sponsored Research Agreements | Penn | Accrued and Other Current Liabilities            
Commitments and Contingencies [Line Items]            
Obligation to be paid   183,000   183,000    
Master Translational Research Services Agreement            
Commitments and Contingencies [Line Items]            
Research and development expense   259,000 286,000 1,997,000 1,970,000  
Maximum research and development expense incurred       1,435,000    
Subscription and Technology Transfer Agreement            
Commitments and Contingencies [Line Items]            
Expense related to agreement   $ 0 $ 250,000 $ 0 $ 250,000