v3.26.1
Balance Sheet Components - Additional Information (Details)
 3 Months Ended 6 Months Ended 12 Months Ended
May 12, 2025
Apr. 26, 2024
USD ($)
patient
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
property
Dec. 31, 2025
USD ($)
Apr. 28, 2025
USD ($)
Restructuring Cost and Reserve [Line Items]                  
Operating lease right-of-use asset     $ 37,739,000   $ 37,739,000     $ 39,888,000  
Impairment of long-lived assets     0 $ 2,382,000 0 $ 2,382,000      
Impairment of leasehold       100,000          
Proceeds from CIRM award (Note 5)         0 6,908,000      
Interest expense     343,000 268,000 643,000 418,000      
California Institute For Regenerative Medicine (CIRM)                  
Restructuring Cost and Reserve [Line Items]                  
Grant award, amount   $ 15,000,000.0             $ 9,200,000
Number of patients treated | patient   20              
Grant award, grantee maximum expected contribution   $ 15,700,000              
Grant award, royalty fee, amount due to other party, multiplier   9              
Grant award, loan conversion period deadline, anniversary of award   10 years              
Basis spread on variable rate   10.00%              
Proceeds from CIRM award (Note 5)         9,200,000        
Interest expense     300,000 300,000 600,000 400,000      
Accrued interest     1,900,000   1,900,000        
California Institute For Regenerative Medicine (CIRM) | Minimum                  
Restructuring Cost and Reserve [Line Items]                  
Converted to loan, repayment percentage   0.80              
California Institute For Regenerative Medicine (CIRM) | Maximum                  
Restructuring Cost and Reserve [Line Items]                  
Converted to loan, repayment percentage   1              
Workforce Reduction                  
Restructuring Cost and Reserve [Line Items]                  
Impairment of long-lived assets       1,300,000   1,300,000      
Positions eliminated, percent 28.00%                
Restructuring costs     0   0        
Restructuring reserve     0   0        
Workforce Reduction | Income Statement Location: us-gaap:GeneralAndAdministrativeExpense                  
Restructuring Cost and Reserve [Line Items]                  
Restructuring costs       300,000   300,000      
Workforce Reduction | Income Statement Location: us-gaap:ImpairmentOfLongLivedAssetsHeldForUse                  
Restructuring Cost and Reserve [Line Items]                  
Restructuring costs       1,300,000   1,300,000      
Workforce Reduction | Income Statement Location: us-gaap:ResearchAndDevelopmentExpense                  
Restructuring Cost and Reserve [Line Items]                  
Restructuring costs       3,100,000   3,100,000      
South San Francisco Building One                  
Restructuring Cost and Reserve [Line Items]                  
Number of properties to be subleased | property             1    
Expected sublease income       700,000   700,000 $ 1,900,000    
Operating lease, right-of-use asset, fair value disclosure       0   0 1,200,000    
Operating lease right-of-use asset             7,500,000    
Impairment of long-lived assets             $ 6,200,000    
Operating lease, impairment loss     0 $ 900,000 0 900,000      
Impairment of leasehold     $ 0   $ 0 $ 100,000      
South San Francisco Building One | Measurement Input, Discount Rate | Valuation Technique, Discounted Cash Flow                  
Restructuring Cost and Reserve [Line Items]                  
Measurement input       0.0925   0.0925 0.0950