Regeneron Pharmaceuticals has reported 84-week findings from the Phase III OPTIMA trial assessing Pasatru (garetosmab-grts) in adults with fibrodysplasia ossificans progressiva (FOP).
The trial showed that the therapy prevented the formation of new heterotopic ossification (HO) lesions between weeks 56 and 84, compared to nine new lesions detected via computed tomography scans in the placebo cohort.
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It also recorded lower frequencies of clinician-assessed flare-ups over the extended period. Participants receiving Pasatru at a 10mg/kg dose experienced one flare-up, while those on 3mg/kg had 14, compared with 17 in the placebo group.
In addition, one HO lesion identified at week 56 in the 3mg/kg cohort was no longer detectable at week 84.
These observations follow previously reported 56-week outcomes published in The Lancet, in which Pasatru achieved a reduction of 90% or greater in new HO lesions.
Royal National Orthopaedic Hospital, London, Metabolic Bone Disease Centre director and OPTIMA trial global primary investigator professor Richard Keen said: “FOP is a devastating, relentless condition in which every flare-up can bring anxiety around potential new, abnormal bone growth and resulting loss of mobility.
“What patients urgently need is long-term control over new HO lesions and flare-ups to help bring peace of mind.
“The 84-week data from the Phase III OPTIMA trial demonstrate sustained disease-modifying control alongside a generally well-tolerated safety profile, which is important for the adult FOP community.”
Safety observations through 84 weeks remained consistent with earlier trial phases, with no deaths reported.
The most frequent treatment-emergent adverse events at 84 weeks were acne in the 10mg/kg group and non-severe nosebleeds in the 3mg/kg group.
Skin and soft tissue infections occurred in 33% of placebo participants, 53% of the 3mg/kg group, and 78% of the 10mg/kg cohort, though all resolved with medical management and none led to treatment discontinuation.
Bleeding events were lower in the 10mg/kg arm than among participants receiving 3mg/kg or placebo.
The multi-centre trial randomised 63 adults across 56 weeks of intravenous dosing before 58 completed the extension period.
Pasatru is a VelocImmune-derived, fully human monoclonal antibody designed to inhibit Activin A protein signalling, which drives abnormal bone formation in FOP.
Regulatory submissions are planned in countries including Japan, following approval in the US by the Food and Drug Administration (FDA) and an ongoing review by the European Medicines Agency (EMA) in the European Union (EU).
In May this year, Regeneron reported that its Phase III trial assessing fianlimab (a LAG-3 inhibitor) and cemiplimab (a PD-1 inhibitor) for metastatic melanoma failed to reach statistical significance for the primary endpoint.
