Zero New Lesions, and a Rising Infection Count
At 84 weeks, Pasatru showed no new heterotopic bone lesions in adults with FOP, against nine on placebo. Skin infections rose to 78 percent at the higher dose.
Fibrodysplasia ossificans progressiva turns muscle, tendon and ligament into bone. A flare is not a bruise. It can be the start of a joint that will not bend again. Richard Keen, at the Royal National Orthopaedic Hospital in London, is the global primary investigator on the trial of the antibody built to interrupt that.
Clinical Trials Arena, on 13 October 2026, reported Regeneron's 84-week readout from OPTIMA. Between week 56 and week 84, CT scans found no new heterotopic ossification lesions in the Pasatru groups, and nine new lesions on placebo. One lesion that had been there at week 56, in the 3 mg/kg group, was no longer detectable at week 84. Clinician-assessed flare-ups in that same window: one on 10 mg/kg, 14 on 3 mg/kg, 17 on placebo. The zero is a company figure from a late-breaking session at the American Society for Bone and Mineral Research. It is not a second Lancet paper.
The 56-week paper is. The Lancet published it online on 28 September 2026, and it sits in the 17 October issue. Sixty-three adults, mean age 26.6. Placebo 21, 3 mg/kg 19, 10 mg/kg 23. New lesions at 56 weeks: 19 on placebo, 1 on 3 mg/kg, 2 on 10 mg/kg. No deaths. Fifty-eight participants completed the double-blind extension to at least 84 weeks.
The FDA approved garetosmab-grts, brand name Pasatru, on 19 August 2026, to reduce new lesions and clinician-assessed flare-ups in adults. A write-up of that approval noted that patient-reported flare-ups through week 56 did not differ significantly between the groups. The doctor saw fewer flares at the high dose. The patient diary did not move in a way the trial could call significant.
Skin and soft tissue infections, printed by Pharmacally on 13 October from the same company readout: 33 percent on placebo, 53 percent on 3 mg/kg, 78 percent on 10 mg/kg. All resolved with treatment. None made a participant stop the drug. The antibody blocks activin A. It is not a cure, and the trial was adults.
Key Facts
- Pasatru (garetosmab-grts) was approved by the FDA on 19 August 2026 for adults with FOP.
- At 56 weeks, in The Lancet: 19 new bone lesions on placebo, 1 on 3 mg/kg, 2 on 10 mg/kg. No deaths.
- Company readout, weeks 56 to 84: no new lesions on Pasatru, nine on placebo.
- Skin and soft tissue infections: 33 percent placebo, 53 percent at 3 mg/kg, 78 percent at 10 mg/kg. All resolved.
- Patient-reported flare-ups through week 56 did not differ significantly.
Why This Matters
A large drop in new bone is the kind of result this disease has not had. The extension's zero is encouraging and it is still the company's slide. The infection gradient has to sit beside the zero, because the dose that produced one flare-up is the dose that produced infections in about four patients in five.
What We Don't Know Yet
Whether the 84-week zero will be published in a journal. Why patient-reported flares did not move at 56 weeks. How the infections behave over years. Any result in children. This licence is for adults.