Annual report pursuant to Section 13 and 15(d)

Research and Development Agreements - Additional Information (Detail)

v3.20.1
Research and Development Agreements - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended 107 Months Ended
Nov. 30, 2019
Jul. 31, 2019
Sep. 30, 2018
Jul. 31, 2018
Jun. 30, 2018
Apr. 30, 2018
Mar. 31, 2020
Jun. 30, 2020
Dec. 31, 2019
Dec. 31, 2018
Nov. 30, 2019
Jun. 23, 2017
Research And Development Collaboration Agreements [Line Items]                        
Deferred revenue                 $ 36,700,000 $ 28,900,000    
Research and development revenues from collaboration agreements                 19,499,000 7,283,000    
Deferred revenue, current                 17,291,000 26,231,000    
Deferred revenue, long-term                 $ 19,385,000 $ 2,670,000    
Common stock, shares issued                 45,589,157 36,736,012    
Common stock, par value                 $ 0.001 $ 0.001    
Grant                        
Research And Development Collaboration Agreements [Line Items]                        
Revenue from grant                 $ 2,700,000 $ 6,000,000    
Takeda Pharmaceuticals Inc                        
Research And Development Collaboration Agreements [Line Items]                        
Deferred revenue                 9,221,000 28,901,000    
Research and development revenues from collaboration agreements                 19,499,000 7,087,000    
Purchase price per share                       $ 6.8423
CPRIT Agreement | Cancer Prevention and Research Institute of Texas                        
Research And Development Collaboration Agreements [Line Items]                        
Product development grant awarded     $ 15,200,000                  
CPRIT Agreement | Cancer Prevention and Research Institute of Texas | ETB MT-3724                        
Research And Development Collaboration Agreements [Line Items]                        
Aggregate proceeds received from award granted                     $ 10,600,000  
Revenue from grant                 9,600,000      
CPRIT Agreement | Scenario Forecast | Cancer Prevention and Research Institute of Texas | ETB MT-3724                        
Research And Development Collaboration Agreements [Line Items]                        
Revenue from grant               $ 1,000,000        
Grant Agreements | Grants Revenue Receivable                        
Research And Development Collaboration Agreements [Line Items]                        
Reimbursement amounts submitted in excess of amounts received are recorded as receivables                 7,100,000 4,300,000    
Takeda Development Agreement                        
Research And Development Collaboration Agreements [Line Items]                        
Deferred revenue                 6,100,000 24,800,000    
Total transaction price                 29,800,000      
Upfront payment                 30,000,000      
Expected co-share payments payable                 10,200,000      
Takeda Development Agreement | Takeda Pharmaceuticals Inc                        
Research And Development Collaboration Agreements [Line Items]                        
Research and development revenues from collaboration agreements                 18,468,000 3,903,000    
Takeda Development Agreement | Scenario Forecast                        
Research And Development Collaboration Agreements [Line Items]                        
Development milestone payment that is achievable             $ 10,000,000          
Takeda Development Agreement | Clinical Development and Regulatory Milestones                        
Research And Development Collaboration Agreements [Line Items]                        
Milestone payments receivable if option is exercised   $ 307,500,000                    
Takeda Development Agreement | Sales Milestone                        
Research And Development Collaboration Agreements [Line Items]                        
Milestone payments receivable if option is exercised   $ 325,000,000                    
Takeda Multi Target Agreement | Takeda Pharmaceuticals Inc                        
Research And Development Collaboration Agreements [Line Items]                        
Deferred revenue                 3,100,000 4,100,000    
Cumulative payments received           $ 5,000,000            
Aggregate milestone payments upon exercise of option to license ETBS                 25,000,000      
Additional preclinical, clinical development and commercialization milestone payment                 397,000,000      
Research and development revenues from collaboration agreements                 983,000 901,000    
Takeda Multi Target Agreement | Takeda Pharmaceuticals Inc | Maximum                        
Research And Development Collaboration Agreements [Line Items]                        
Contractual contingency fees                 10,000,000      
Commercial milestone payment                 150,000,000      
Takeda Individual Project Agreement | Takeda Pharmaceuticals Inc                        
Research And Development Collaboration Agreements [Line Items]                        
Additional research and development revenue         $ 2,200,000              
Increase in transaction consideration related to research services       $ 1,100,000                
Research and development revenues from collaboration agreements                 48,000 2,191,000    
Takeda Individual Project Agreement | Takeda Pharmaceuticals Inc | Maximum                        
Research And Development Collaboration Agreements [Line Items]                        
Research and development revenues from collaboration agreements                 100,000      
Vertex Collaboration Agreement                        
Research And Development Collaboration Agreements [Line Items]                        
Deferred revenue                   0    
Milestone payments receivable if option is exercised $ 180,000,000                      
Upfront payment 38,000,000                      
Upfront payment, cash 23,000,000                      
Upfront payment, equity method investments $ 15,000,000                   $ 15,000,000  
Deferred revenue, current                 8,500,000      
Deferred revenue, long-term                 19,000,000      
Common stock, shares issued 1,666,666                   1,666,666  
Common stock, par value $ 0.001                   $ 0.001  
Vertex Collaboration Agreement | Common Stock                        
Research And Development Collaboration Agreements [Line Items]                        
Purchase price per share $ 9.00                   $ 9.00  
Fair value of allocated consideration $ 4,500,000                      
Vertex Collaboration Agreement | ETBs                        
Research And Development Collaboration Agreements [Line Items]                        
Aggregate milestone payments upon exercise of option to license ETBS 22,000,000                   $ 22,000,000  
Vertex Collaboration Agreement | Sales Milestone                        
Research And Development Collaboration Agreements [Line Items]                        
Milestone payments receivable if option is exercised $ 70,000,000                      
Other Collaboration Agreements                        
Research And Development Collaboration Agreements [Line Items]                        
Research and development revenues from collaboration agreements                 $ 0 $ 200,000