Pasatru (garetosmab-grts): FDA approval, pivotal trial and safety
Approved
Type
Therapeutic biologic · Intravenous
FDA-approved use
To reduce new heterotopic ossification and clinician-assessed disease flare-ups in adults with fibrodysplasia ossificans progressivaWording from FDA's list of novel approvals.
FDA review
Priority reviewOrphan drug
Company
Regeneron
Application
BLA 761508
Specialty
Genetics
At a glance
Pasatru (garetosmab-grts) is an activin A-blocking antibody approved for adults with fibrodysplasia ossificans progressiva (FOP) to reduce new heterotopic ossification lesions and clinician-assessed flare-ups. In the phase 3 OPTIMA trial, new lesions at week 56 fell by 90% and 94% with the two doses versus placebo. Skin and soft tissue infections, epistaxis, and fetal harm are the main safety points.
What it is and how it works
FOP is caused by gain-of-function mutations in the ACVR1 (ALK2) receptor. In these patients, activin A activates the mutant receptor and drives heterotopic bone formation. Garetosmab-grts is a human IgG4 monoclonal antibody that binds activin A and blocks its signaling, so the mutant receptor is not activated. It acts on the ligand rather than the receptor.
Randomized, double-blind, placebo-controlled, phase 3 trial at 18 sites in 16 countries and regions. Patients received intravenous treatment monthly for 56 weeks, followed by a double-blind extension.
Patients
63 adults with FOP confirmed by an ACVR1 mutation. Median age was 25 years in the label. 60% were female. 95% had the R206H mutation.
Compared with
Placebo (n=21), compared with two garetosmab doses: lower dose (n=19) and higher dose (n=23).
Primary endpoint
Total number of new heterotopic bone lesions at week 56 on low-dose whole-body CT. The publication also listed adverse events of special interest through week 56 as a primary safety end point.
Result
There were 19 new lesions with placebo, 1 with the lower dose, and 2 with the higher dose. Rate ratio versus placebo was 0.06 (95% CI 0.00 to 0.73; P=0.027) for the lower dose and 0.10 (95% CI 0.01 to 0.76; P=0.026) for the higher dose. The label describes reductions of 94% and 90%.
Other results
New lesions occurred in 5 of 21 (24%) with placebo, 1 of 19 (5%) with the lower dose, and 2 of 23 (9%) with the higher dose. Clinician-assessed flare-ups through week 56 numbered 66 with placebo, 53 with the lower dose, and 9 with the higher dose. The rate ratio was 0.12 (95% CI 0.03 to 0.42) for the higher dose and 0.85 (95% CI 0.26 to 2.73) for the lower dose. Patient-reported flare-ups did not differ significantly. Reduction in new lesion volume was not statistically significant on the prespecified test.
Safety in the trial
Adverse reactions in at least 10% included abscess (35% higher dose, 11% lower dose, 10% placebo), acne, increased hair growth, madarosis, oral ulcers, and epistaxis (53% lower dose, 17% higher dose, 24% placebo). Adverse events of special interest occurred in 1 of 21 with placebo, none with the lower dose, and 4 of 23 (17%) with the higher dose. No deaths occurred. 62 participants completed 56 weeks.
How does Pasatru (garetosmab-grts) compare with the alternatives (Palovarotene, Short-course high-dose corticosteroids, NSAIDs and other analgesics) for its approved use (to reduce new heterotopic ossification and clinician-assessed disease flare-ups in adults with fibrodysplasia ossificans progressiva)? Summarize head-to-head and indirect evidence, efficacy, safety and where each fits, with citations.
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Safety signals
There is no boxed warning. Pasatru is contraindicated in pregnancy because it can cause fetal harm. Pregnancy status should be verified before treatment, and effective contraception is advised during treatment and for 6 months after the last dose. Skin and soft tissue infections needing treatment or hospitalization, including abscess and cellulitis, have occurred. Serious spontaneous epistaxis has been reported. The most common adverse reactions were abscess, acne, increased hair growth, madarosis, oral ulcers, and epistaxis.
What it competes with
Care for FOP is largely supportive and aimed at symptoms, with a focus on avoiding trauma that can trigger new bone formation. A retinoid approved for FOP is also used to reduce new heterotopic ossification.
PalovaroteneOral retinoid (RARγ agonist) approved to reduce new heterotopic ossification in FOP. Has important safety concerns, including effects on skeletal growth in children and embryo-fetal toxicity.
Short-course high-dose corticosteroidsUsed at the onset of flare-ups, especially those affecting major joints, to reduce swelling and pain. Does not prevent heterotopic bone formation.
NSAIDs and other analgesicsUsed for pain and inflammation during flare-ups as symptomatic care.
Supportive and surgical-avoidance careIncludes injury prevention, avoiding intramuscular injections and invasive dental procedures, and physical and occupational support. Surgery to remove heterotopic bone is generally avoided because it…
Bottom line for clinicians
Pasatru is for adults with genetically confirmed FOP who need a disease-modifying option to limit new heterotopic bone. Weigh the large reduction in new lesions against the infection, bleeding, and fetal risks, and note that the lower dose did not reduce clinician-assessed flare-ups. Counsel females of reproductive potential on pregnancy testing and contraception.
Dosing, contraindications and full warnings are in the prescribing information.
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Last updated October 28, 2026 by 2 Minute Medicine.
For healthcare professionals. A summary of public FDA documents and published trials, not medical advice. Check the full prescribing information before prescribing.
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