v3.26.1
Intangible assets - Disclosure of Detailed Information about Intangible Assets (Details) - EUR (€)
 12 Months Ended 89 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2025
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Intangible assets other than goodwill at beginning of period € 0 € 416,000 € 1,553,000    
Acquisitions 0 0 0    
Additions considerations 0 0 2,000,000    
Disposals (41,000,000) 0 0    
Depreciation 0 (416,000) (3,140,000)    
Impairment 0 0 0    
Impairment 41,000,000        
Transfers 0 0 0    
Intangible assets other than goodwill at end of period 0 0 416,000 € 1,553,000 € 0
Monalizumab Agreement          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Depreciation   (416,000) (1,138,000)    
Sanofi options          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Depreciation     (2,000,000)    
PH5401 (anti-C5aR) rights acquired from Novo Nordisk A/S          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Impairment       (41,000,000) 0
Impairment       41,000,000  
Purchased licenses          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Intangible assets other than goodwill at beginning of period 0 416,000 1,553,000    
Acquisitions 0 0 0    
Additions considerations 0 0 2,000,000    
Disposals 0 0 0    
Depreciation (416,000) (3,140,000)    
Impairment   0 0    
Impairment 0        
Transfers 0 0 0    
Intangible assets other than goodwill at end of period 0 0 416,000 1,553,000 0
Other intangible assets          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Intangible assets other than goodwill at beginning of period 0 0 0    
Acquisitions 0 0 0    
Additions considerations 0 0 0    
Disposals 0 0 0    
Depreciation 0 0 0    
Impairment   0 0    
Impairment 0        
Transfers 0 0 0    
Intangible assets other than goodwill at end of period 0 0 0 0 0
In progress          
Reconciliation of changes in intangible assets other than goodwill [abstract]          
Intangible assets other than goodwill at beginning of period 0 0 0    
Acquisitions 0 0 0    
Additions considerations 0 0 0    
Disposals (41,000,000) 0 0    
Depreciation 0 0 0    
Impairment   0 0    
Impairment 41,000,000        
Transfers 0 0 0    
Intangible assets other than goodwill at end of period € 0 € 0 € 0 € 0 € 0