New Infusion When Soft Tissue Turns to Bone (Adult FOP)

Pasatru (garetosmab-grts; pronounced PA-SAH-TROO) is an activin signaling inhibitor — a fully human IgG4 monoclonal antibody that binds activin A and blocks activation of FOP-mutant ACVR1 (ALK2). In FOP, mutant ACVR1 is turned on by activin A, driving heterotopic ossification (extra bone in muscle, tendon, ligament, and other connective tissue). Pasatru is given by intravenous infusion. It is not an oral retinoid, not surgery, and not a cure that removes bone already formed.

The FDA approved BLA 761508 on 19 August 2026 (Novel Drug Approvals for 2026, row 33). Approval letter signed Hylton V. Joffe, MD, MMSc, Director, Office of Cardiology, Hematology, Endocrinology, and Nephrology, CDER (electronic signature 19 Aug 2026 11:25:47). Licence holder / manufactured by: Regeneron Pharmaceuticals, Inc., Tarrytown, NY; U.S. License No. 1760. The application received Breakthrough Therapy, Fast Track, Orphan Drug, and Priority Review designations from the FDA (FDA announcement). It was not referred to an FDA advisory committee (approval letter). Dating period on the letter: 60 months from manufacture when stored at 2–8 °C.

Distinct from Sohonos (palovarotene): Sohonos is an oral RARγ-selective retinoid (Ipsen) with its own labels and age bands in countries where it is authorised. Pasatru is an IV Activin A monoclonal antibody, adults only on the US label, with a different mechanism, dose, and safety story (pregnancy contraindication; skin/soft-tissue infection; epistaxis). Compare labels with the clinic; they are not interchangeable.

Where this is taking place

Commercial labelled door today: United States — FDA full approval for adults with FOP to reduce new HO lesions and clinician-assessed flare-ups. Infusions are weight-based, diluted into 5% dextrose, run over 60 minutes with an infusion pump. Regeneron company materials say Pasatru can be given across a range of care settings, including home infusion where appropriate — that is a company framing; the USPI describes how to prepare and give the IV infusion and does not itself create a DIY home kit. The prescribing clinician and infusion team decide the setting. This is not a subcutaneous self-injection and not an IV push or bolus.

Outside the United States: As of this draft, no confirmed Health Canada Notice of Compliance, European Commission marketing authorisation, MHRA licence, TGA ARTG listing, Swissmedic authorisation, NMPA decision, or PMDA/MHLW licence for Pasatru / garetosmab-grts. Company and IFOPA materials: EMA review accepted / under review. MAA under review ≠ EC licence. IFOPA’s community note (19 Aug 2026): Pasatru is described as available for FOP treatment in the United States at approval. A US carton is not another country’s label. Do not import on your own.

OPTIMA — NCT05394116 (USPI Study 1) — Phase 3, multicenter, randomized, double-blind, placebo-controlled. Sponsor: Regeneron Pharmaceuticals. CT.gov status: ACTIVE, NOT RECRUITING (primary efficacy period completed; extension ongoing). Actual enrolment 63. Start 21 Nov 2022; primary completion 17 Jul 2025; estimated study completion 27 Feb 2029. Countries with listed sites include the United States, Australia, Brazil, Chile, China, Colombia, Finland, France, Hong Kong, Italy, Japan, Malaysia, Netherlands, Poland, South Africa, South Korea, Spain, and the United Kingdom. No Canadian sites on the CT.gov location list retrieved for this draft. US sites named on the record include UCLA Medical Center (Los Angeles) and Vanderbilt University Medical Center (Nashville). Not a new-enrolment path for newly labelled commercial use — the pivotal double-blind period is done; open extension is for people already in the trial.

OPTIMA-2 — NCT07559513 — Phase 3 pediatric / adolescent programme. CT.gov status: NOT YET RECRUITING (IFOPA and CT.gov). Estimated start 2 Feb 2027. Not adult commercial supply and not an open paediatric door today. The US adult label says safety and effectiveness in children have not been established.

LUMINA-1 — NCT03188666 — completed Phase 2 adult programme (Nature Medicine 2023). Supportive science history — not the USPI Study 1 pivotal efficacy table used for the August 2026 adult label conversation.

The practical door in the US is an FOP-experienced clinician (often metabolic bone / endocrinology / rare-disease centre) who can confirm ACVR1-related FOP, order the infusions, manage pregnancy testing / contraception where needed, and watch infection and nosebleed risk — not a mail-order vial.

Approval matrix

Access by country

• United States: Ask an FOP / metabolic bone / rare-disease clinic about FDA-labelled Pasatru. Labelled 19 August 2026 for adults to reduce new HO lesions and clinician-assessed flare-ups. Starting dose: 10 mg/kg IV over 60 minutes every 4 weeks; may decrease to 3 mg/kg every 4 weeks if 10 mg/kg is not tolerated. Missed dose: give as soon as possible, then reschedule every 4 weeks from that dose. Prior authorisation and specialty / buy-and-bill / home-infusion logistics still apply when the clinic chooses a care setting. No list price or copay dollars in this article. Regeneron rare-disease support programme named in the company approval press: myRARE™ — myRARE.com or 1-833-4my-RARE (1-833-469-7273) for product information, benefit verification, and information about potential financial support (company press — not a formulary guarantee). Adverse reactions / more information on the USPI / Medication Guide: Regeneron 1-877-372-7287 or www.PASATRU.com; FDA MedWatch 1-800-FDA-1088. Prescribing Information: FDA label PDF / DailyMed / Regeneron FPI. This is US commercial labelled supply, not Special Access and not a DIY import.

• Canada: Pasatru authorisation not confirmed. No Canadian sites on OPTIMA (NCT05394116) as retrieved here. Sohonos (palovarotene) is a separate authorised Canadian FOP conversation where that Product Monograph applies — it is not Pasatru. Do not assume SAP, named-patient, or cross-border mail-order for Pasatru is available or appropriate. Ask the Canadian FOP clinic what legal paths exist in Canada when a Pasatru Canadian label does not yet exist.

• European Union: EC marketing authorisation not confirmed. Company / IFOPA describe an EMA filing as accepted / under review. That is a review, not a licence. Member-state reimbursement questions do not arise until there is an MA — and even then, authorised ≠ funded.

• United Kingdom: MHRA authorisation not confirmed. UK trial site (for example Royal National Orthopaedic Hospital on OPTIMA) is not a marketing authorisation.

• Australia / Japan / China / other countries with OPTIMA sites: Trial participation or a completed primary period is not a commercial Pasatru label. Regulator authorisation not confirmed in this draft. Company materials mention planned additional submissions (including Japan) — planned ≠ authorised.

• If your regulator has not authorised it: do not import on your own. Ask the local FOP clinician about documented special-access / named-patient rules, referral to a centre in a labelled country, or open trial doors (for example paediatric OPTIMA-2 when it actually opens) — without treating a US vial as a foreign carton.

Who is eligible (from the US label)

This is an adult FOP conversation on the USPI — not a paediatric label.

United States (USPI / Medication Guide, revised / issued August 2026):

• Indication: Reduce formation of new heterotopic ossification (HO) lesions and clinician-assessed flare-ups in adults with fibrodysplasia ossificans progressiva (FOP).
• Dose: Start 10 mg/kg IV over 60 minutes once every 4 weeks. May decrease to 3 mg/kg IV over 60 minutes once every 4 weeks if 10 mg/kg is not tolerated.
• Dilute into 5% Dextrose Injection, USP (bag volume 50–100 mL; final concentration 0.9–25 mg/mL); use an infusion pump; recommended in-line / add-on filter 0.2–5 micron PES or PA; flush with 5% dextrose after infusion. Do not mix other drugs in the same line. Do not shake the vial.
• Pregnancy testing before starting for females of reproductive potential.
• Contraindication: Pregnancy (can cause fetal harm).
• Contraception: Effective contraception during treatment and for 6 months after the last dose. Stop immediately and contact the clinician if pregnancy occurs.
• Lactation: Breastfeeding not recommended during treatment and for 6 months after the last dose.
• Males: Based on animal data, may impair male fertility — discuss with the clinician if that matters for family planning.
• Pediatrics: Safety and effectiveness not established.
• Geriatrics: Clinical studies did not include enough patients ≥65 to know if they respond differently.
• OPTIMA enrolled adults with ACVR1 FOP-causing mutation confirmation on the label’s Study 1 description; median age 25 (range 18–42); 95% had the R206H mutation; mean baseline CAJIS 13 (range 0–19).

Not labelled on sources confirmed for this draft:

• Children / adolescents (OPTIMA-2 NCT07559513 is not yet recruiting — not a commercial paediatric door).
• EU, UK, Canadian, Japanese, Australian, Swiss, or Chinese Pasatru marketing authorisations (not confirmed here).
• Replacing Sohonos by self-switching without a clinician reading both labels.
• A claim that patient-reported flare-ups were significantly reduced on the USPI (they were not significantly different from placebo through Week 56).

What the pivotal study showed (OPTIMA / USPI Study 1)

Use the USPI for a US prescription conversation. Journals and conference abstracts are supportive reading.

Study 1 — NCT05394116 (OPTIMA):

• Randomized, double-blind, parallel-group, multicenter, placebo-controlled; 63 adults with FOP and an ACVR1 FOP-causing mutation.
• Arms: Pasatru 10 mg/kg (N=23), Pasatru 3 mg/kg (N=19), or placebo (N=21), IV every 4 weeks for 56 weeks; 61 continued original assignment in a double-blind extension.
• Primary: number of new HO lesions at Week 56 by low-dose whole-body CT.
• Key secondaries included number of clinician-assessed flare-ups through Week 56; proportion with new HO lesions; total volume of new HO lesions.

USPI Table 2 (new HO lesions at Week 56):

Both Pasatru doses met the primary endpoint (multiplicity-adjusted p < 0.05 on the label).

Clinician-assessed flare-ups through Week 56 (USPI narrative): 9 (10 mg/kg), 53 (3 mg/kg), 66 (placebo). Rate ratio vs placebo: 0.12 (0.03, 0.42) for 10 mg/kg; 0.85 (0.26, 2.73) for 3 mg/kg. Company materials describe an ~88% reduction in clinician-assessed flare-ups at the 10 mg/kg dose — align the clinic conversation with the USPI rate-ratio numbers. Patient-reported flare-up proportions were not significantly different from placebo through Week 56.

Mean new HO volume was much smaller numerically on both Pasatru doses than placebo, but that volume comparison was not statistically significant on the pre-specified Wilcoxon test on the label.

Trial status honesty: OPTIMA’s primary period supports the US label. CT.gov remains ACTIVE, NOT RECRUITING because of the extension — it is not a door for new commercial starters outside labelled US distribution.

How it is given (on-label)

Company materials: care settings may include home infusion where appropriate when the clinic and infusion team arrange it — still a prescribed, prepared IV infusion, not a self-mixed home experiment.

Safety (what the label puts first)

Embryo-fetal toxicity / pregnancy contraindication: Can cause fetal harm. Pregnancy test before starting when applicable. Effective contraception during treatment and for 6 months after the last dose. Stop immediately if pregnancy occurs.

Skin and soft tissue infections: Abscesses and cellulitis requiring treatment and/or hospitalisation occurred in trials. Report redness, pain, swelling, warmth, fever, or feeling generally unwell.

Epistaxis (nosebleeds): Including serious cases needing medical intervention (one serious trial case needed hospital nasal packing and a clotting agent). Seek care if a nosebleed is severe, lasts more than about 20 minutes, or does not stop with standard first-aid pressure.

Most common adverse reactions (≥10% on Pasatru and more than placebo through Week 56) — USPI Table 1:

Cellulitis: 4% on 10 mg/kg (1 patient) in the labelled set.

Lactation: not recommended during treatment and for 6 months after.

Immunogenicity: Anti-drug antibodies in 1.3% (1/76) in the labelled clinical-trial summary; insufficient data to judge clinical impact.

Report suspected adverse reactions to Regeneron 1-877-372-7287 or FDA MedWatch 1-800-FDA-1088.

How to talk to a doctor

Bring the brand, the INN, the BLA / NCT numbers, and the US Prescribing Information if you are in a US clinic. Outside the US, bring honesty that a local Pasatru label may not exist yet.

1. "I am an adult with FOP. The FDA labelled Pasatru (garetosmab-grts) on 19 August 2026 to reduce new HO lesions and clinician-assessed flare-ups. Is that labelled for me in this country?"
2. "This is an Activin A monoclonal antibody, not Sohonos (palovarotene). Can we compare the Pasatru and Sohonos labels if both are relevant — they are different products?"
3. "The starting dose is 10 mg/kg IV over 60 minutes every 4 weeks, with a possible decrease to 3 mg/kg. Who at this centre orders FOP biologic infusions, and can the setting be clinic or home infusion when appropriate?"
4. "OPTIMA (NCT05394116) showed about a 90–94% reduction in new HO lesions at Week 56 versus placebo. Clinician-assessed flares fell sharply at 10 mg/kg; patient-reported flares did not differ significantly from placebo on the label."
5. "Please plan pregnancy testing and contraception during treatment and for 6 months after if I can become pregnant — pregnancy is a contraindication."
6. "I will watch for skin infections / abscesses and for nosebleeds that are heavy or last more than about 20 minutes."
7. "Is prior authorisation started? Who coordinates the NDC 61755-012-01 vial and infusion scheduling / myRARE benefit check?"
8. "EU, Canadian, and other ex-US Pasatru authorisations are not confirmed on the sources we are using — I will not import a foreign carton."
9. "If we are outside the US, what legal options exist while an EMA review is only described as under review — local special-access rules, referral, or waiting for OPTIMA-2 (NCT07559513) if paediatric — without DIY import?"
10. "Children: the US label says paediatric use is not established. Is OPTIMA-2 open yet, or only listed as not yet recruiting?"

Research and regulatory team (from sources only — no invented contacts)

Names and roles as they appear on primary sources — not a clinic directory.

• Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591-6707 — BLA 761508 licence holder; U.S. License No. 1760; OPTIMA / OPTIMA-2 sponsor; USPI manufacturer.
• Shazia Ali, PharmD — Senior Director, Regulatory Affairs, Regeneron; addressee on the BLA approval letter (corporate regulatory contact, not a treating clinic).
• Hylton V. Joffe, MD, MMSc — Director, Office of Cardiology, Hematology, Endocrinology, and Nephrology, OND/CDER — signed the 19 Aug 2026 approval letter.
• Meghna M. Jairath, Pharm.D. — FDA Senior Regulatory Project Manager named on the approval letter (agency contact, not a patient hotline).
• Clinical Trial Management, Regeneron Pharmaceuticals — Study Director role on the NCT05394116 CT.gov record (title-level; not a named personal PI on the API record retrieved here).
• Michelle Davis — Executive Director, International FOP Association (IFOPA); quoted on the Regeneron 19 Aug 2026 approval press (patient-community voice, not a prescribing contact).
• myRARE™ — Regeneron rare-disease support programme named in the approval press: 1-833-469-7273 / myRARE.com.
• USPI / Medication Guide contact: 1-877-372-7287; www.PASATRU.com; MedWatch 1-800-FDA-1088.
• Regeneron clinical-trials contact on the approval press (for trial information framing): clinicaltrials@regeneron.com or +1 844-734-6643 — not a prescription desk.
• LUMINA-1 Nature Medicine byline (Phase 2 history; selected): Maja Di Rocco; Eduardo Forleo-Neto; Robert J. Pignolo; and co-authors including George D. Yancopoulos — journal authors, not a call centre.
• Site-level hospital phone numbers are not listed here — ask your own FOP clinician. CT.gov overall named personal PIs: not listed on the NCT05394116 API record retrieved for this draft (facilities only).

Canada zoom: Pasatru not confirmed

There is no retrieved Health Canada Notice of Compliance or DIN for Pasatru / garetosmab-grts on the sources used for this draft. US FDA approval does not create a Canadian Product Monograph for Pasatru. OPTIMA did not list Canadian sites on the CT.gov record retrieved here. Sohonos (palovarotene) remains a different product with its own Canadian authorisation history — keep that conversation separate. Do not treat cross-border mail-order of a US Pasatru vial as the care plan. Ask a Canadian FOP / rare-bone clinician what legal options exist while waiting for any future Canadian Pasatru decision.

Bottom line

Pasatru (garetosmab-grts) is an FDA-approved Activin A monoclonal antibody for adults with FOP, labelled 19 August 2026 (BLA 761508) to reduce new HO lesions and clinician-assessed flare-ups. Starting dose: 10 mg/kg IV over 60 minutes every 4 weeks (may decrease to 3 mg/kg). OPTIMA (NCT05394116) showed about a 90–94% reduction in new HO lesions at Week 56 versus placebo, with a clear clinician-assessed flare reduction at 10 mg/kg; patient-reported flares did not differ significantly from placebo on the label. Watch pregnancy (contraindicated), skin/soft-tissue infection, and nosebleeds. US labelled; other regulators not confirmed. An EMA review under way is not a European licence. Not Sohonos. The door is an FOP-capable clinic writing the US label — OPTIMA extension and not-yet-recruiting OPTIMA-2 are not new adult commercial enrolment paths.

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Primary sources

1. FDA Novel Drug Approvals for 2026 — Pasatru / garetosmab-grts, approval date 8/19/2026, row 33 — https://www.fda.gov/drugs/novel-drug-approvals-fda/novel-drug-approvals-2026
2. FDA Prescribing Information PDF, BLA 761508, label 761508Orig1s000lbl.pdf, Revised 8/2026 — https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/761508Orig1s000lbl.pdf
3. FDA BLA approval letter, BLA 761508, signed Hylton V. Joffe, MD, MMSc, 19 Aug 2026 — https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2026/761508Orig1s000ltr.pdf
4. DailyMed PASATRU (garetosmab-grts), setid 0d5cec96-b02b-4f1d-bc66-51e62ce04e3c — https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=0d5cec96-b02b-4f1d-bc66-51e62ce04e3c
5. Regeneron Pharmaceuticals press — Pasatru (garetosmab-grts) FDA approval, 19 Aug 2026 — https://newsroom.regeneron.com/news-releases/news-release-details/pasatrutm-garetosmab-grts-first-and-only-fda-approved-treatment
6. Regeneron Full Prescribing Information host (company FPI PDF) — https://www.regeneron.com/downloads/pasatru_fpi.pdf
7. ClinicalTrials.gov NCT05394116 — OPTIMA (adult Phase 3) — https://clinicaltrials.gov/study/NCT05394116
8. ClinicalTrials.gov NCT07559513 — OPTIMA-2 (paediatric / adolescent Phase 3; not yet recruiting) — https://clinicaltrials.gov/study/NCT07559513
9. ClinicalTrials.gov NCT03188666 — LUMINA-1 (Phase 2) — https://clinicaltrials.gov/study/NCT03188666
10. Di Rocco M, Forleo-Neto E, Pignolo RJ, et al. Garetosmab in fibrodysplasia ossificans progressiva: a randomized, double-blind, placebo-controlled phase 2 trial. Nature Medicine. 2023;29:2615–2624. doi:10.1038/s41591-023-02561-8 — https://www.nature.com/articles/s41591-023-02561-8
11. IFOPA community note — U.S. FDA Approves Regeneron Pharmaceuticals’ garetosmab as a Treatment for FOP, 19 Aug 2026 (community / access framing; not a regulator decision page) — https://www.ifopa.org/us-fda-approves-regeneron-pharmaceuticals-garetosmab-treatment-fop
12. Health Canada Summary Basis of Decision for Sohonos (palovarotene) — different product, cited only to keep Canada conversations from collapsing Pasatru into Sohonos — https://dhpp.hpfb-dgpsa.ca/review-documents/resource/SBD00593