v3.26.1
Segment Reporting - Schedule of Segment Profit or Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting Information [Line Items]            
Research and development expenses $ 11,908   $ 2,968   $ 21,884 $ 6,604
General and administrative expenses 4,137   2,483   10,482 6,503
Other segment expenses 3,408   1,840   4,301 3,720
Total operating expenses 19,453   7,291   36,667 16,827
Loss from operations (19,453)   (7,291)   (36,667) (16,827)
Other income, net 446   325   1,032 718
Sermonix pre-funded warrant change in fair value 0       (16,320)  
Net loss (19,007) $ (32,948) (6,966) $ (9,143) (51,955) (16,109)
Sermonix Pre-funded Warrants            
Segment Reporting Information [Line Items]            
Sermonix pre-funded warrant change in fair value     0   (16,320) 0
Lasofoxifene            
Segment Reporting Information [Line Items]            
Research and development expenses 9,109   0   17,738 0
Fosgonimeton (ATH-1017)            
Segment Reporting Information [Line Items]            
Research and development expenses 6   555   189 1,862
Brelgometon (ATH-1105)            
Segment Reporting Information [Line Items]            
Research and development expenses 294   1,237   537 2,161
ATH-1020            
Segment Reporting Information [Line Items]            
Research and development expenses 0   0   0 5
Preclinical Programs and Other Costs            
Segment Reporting Information [Line Items]            
Research and development expenses 465   258   820 660
Milestone liability            
Segment Reporting Information [Line Items]            
Research and development expenses 175   0   (754) 0
Personnel-Related Costs, Excluding Stock- Based Compensation            
Segment Reporting Information [Line Items]            
Research and development expenses $ 1,859   $ 918   $ 3,354 $ 1,916