Efficacy and safety of garetosmab, an activin A-blocking antibody, in fibrodysplasia ossificans progressiva (OPTIMA): a randomised, double-blind, placebo-controlled, phase 3 trial
Authors' conclusion
Garetosmab substantially reduced the number of new heterotopic bone lesions, providing robust evidence of its potential to be an efficacious and generally well tolerated disease-modifying therapy for FOP.
Study context
- Population
- Adults aged ≥18 years with fibrodysplasia ossificans progressiva (FOP); mean age 26.6 years, 60% female62 completed 56 weeks
- Participants
- 63 adults
- Comparison
- Monthly IV garetosmab 3 mg/kg or 10 mg/kg vs placebo
- Placebon = 21reference
- Garetosmab 3 mg/kgn = 19
- Garetosmab 10 mg/kgn = 23
- Primary endpoint
- Total number of new heterotopic bone lesions (efficacy); treatment-emergent adverse events of special interest (safety)
- Follow-up
- Week 56
Methodological detailsdouble-blind, placebo-controlled, phase 3, 18 sites in 16 countries and regions, stratified randomisation
- Double-blind
- Placebo-controlled
- Phase 3
- 18 sites in 16 countries and regions
- Stratified randomisation
Primary result
As reported in the abstract
Total number of new heterotopic bone lesions
Placebo
19
events
Garetosmab 3 mg/kg
1
events
Garetosmab 10 mg/kg
2
events
Each group vs placeboRate ratio (95% CI)P value
Garetosmab 10 mg/kg
0.10(0.01–0.76)
P = 0.026- Garetosmab 3 mg/kg
- rate ratio 0.06 (95% CI 0.00–0.73); P = 0.027
Safety
| Outcome | Placebo | Garetosmab 3 mg/kg | Garetosmab 10 mg/kg |
|---|---|---|---|
| Treatment-emergent AESIs (primary safety endpoint) · through week 56 | 5% | 0 events | 17% |
- Treatment-emergent adverse events of special interest (AESIs) (primary safety endpoint) — Deaths
- 0
Treatment-emergent AESIs (primary safety endpoint) · through week 56
- All AESIs considered treatment-related
Original publication
Efficacy and safety of garetosmab, an activin A-blocking antibody, in fibrodysplasia ossificans progressiva (OPTIMA): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet. Published 28 September 2026. doi:10.
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