Prescribing guide
Pasatru (garetosmab-grts)Pregnancy verification, weight-based IV dosing, infusion preparation, safety counseling and prior authorization for fibrodysplasia ossificans progressivaFor prescribers and their offices treating fibrodysplasia ossificans progressiva (FOP): what the pharmacy needs before it ships, what the prior authorization wants documented, the titration and the monitoring the label requires.
Dispensing gate
No REMS and no boxed warning; verify that females of reproductive potential are not pregnant before initiating, advise effective contraception through 6 months after the last dose, confirm a current weight for mg/kg dosing, obtain prior authorization, and arrange a site of care with an infusion pump.
Example PA threshold
BCBS Michigan example, P&T October 8, 2026: FDA-approved indication and age, FOP confirmed by genetic testing showing an ACVR1 mutation, no combination with other targeted FOP therapy such as Sohonos, trial, contraindication or intolerance to the plan's preferred drugs, chart notes; one-year authorizations.
Monitoring
No scheduled laboratory test in the label; pregnancy status before initiation, counseling on signs of skin and soft tissue infection and on epistaxis that is severe, prolonged (for example over 20 minutes) and not resolved by first aid, and immediate discontinuation if pregnancy occurs.
Support line
myRARE for Pasatru, 1-877-372-7287 (1-877-3PASATRU) option 1, Monday to Friday 9 AM to 9 PM Eastern; insurance navigation, treatment logistics and financial support options; copay terms are not published on the Pasatru pages read.
Give your patient their plan
A one-page handout for starting Pasatru, in plain language: what the first fill waits on, the first dates, who will call and the symptoms to report, with blank lines for the start date and your office's number. The link opens the patient's full first 90 days page, where their dates become calendar entries.
trialfriend.com/p/pasatruBefore the first fill: REMS, labs and enrollment
The steps that the pharmacy, the REMS or the drugmaker's program will wait on, in the order they usually need to happen. A first fill of a specialty drug most often stalls on one of these rather than on the plan.
| Step | What it requires | Source |
|---|---|---|
| Confirm the indication | To reduce formation of new heterotopic ossification lesions and clinician-assessed flare-ups in adults with FOP. Pediatric safety and effectiveness are not established; too few patients 65 and older were studied to tell whether they respond differently. | FDA label |
| Verify pregnancy status | Verify that females of reproductive potential are not pregnant before initiating (section 2.1). Pasatru is contraindicated during pregnancy. | FDA label |
| Counsel on contraception and lactation | Effective contraception during treatment and for 6 months after the last dose. Breastfeeding is not recommended during treatment and for 6 months after the last dose. | FDA label |
| Medication Guide | The carton reads: ATTENTION: Dispense the enclosed Medication Guide to each patient. Section 17 covers embryo-fetal toxicity, skin and soft tissue infections, epistaxis and lactation. | FDA label |
| Prior authorization | BCBS Michigan requires PA for BCBS, BCN, MAPPO and BCNA lines and bills under HCPCS J3590. Chart notes and patient-specific documentation must accompany the request. | BCBS Michigan policy |
| Plans without criteria | Blue Shield of California requires authorization before administration for claim payment, lists C9399 and J3590, and reviews requests for medical necessity while criteria are pending P&T approval. | Blue Shield of California policy |
| Arrange the site of care | Regeneron's brochure lists an infusion center, standalone or hospital-based, or home, with a trained healthcare provider giving the infusion. It says not all hospitals or infusion centers offer Pasatru and that Regeneron does not recommend any particular site. | Regeneron patient brochure |
| Home infusion | Regeneron's approval announcement says Pasatru can be administered across a range of care settings, including home infusion where appropriate. | Regeneron press release |
| Enroll in myRARE | The myRARE Pasatru page has an Enroll link and an upload link for supporting documentation after an enrollment form is submitted. Phone 1-877-372-7287, option 1, Monday to Friday, 9 AM to 9 PM Eastern. | myRARE for Pasatru |
| REMS and postmarketing | The approval letter pages read contain no REMS or postmarketing requirement section. The application was not referred to an advisory committee, and PREA does not apply because of orphan designation. | FDA letter |
Prior authorization criteria and what to document
One public policy as the example: Blue Cross Blue Shield of Michigan, October 8, 2026. Approval one year at a time, with quantity limits that follow FDA-recommended dosing. Renewal needs clinical documentation that the criteria are still met and that the medicine is providing clinical benefit.. This is one plan's medical drug policy, and other plans differ. It was written after the August 2026 label, which it cites. The policy says coverage and approval length may differ for Medicare Part B members. It does not name the preferred drugs in its fourth criterion.
| Element | What the policy asks | In the chart | Source |
|---|---|---|---|
| Indication and age | FDA approved indication and FDA approved age; the label indication is adults with FOP | Diagnosis and date of birth on the request | BCBS Michigan policy |
| Genetic confirmation | Diagnosis of FOP confirmed by genetic testing showing an ACVR1 mutation | ACVR1 genetic report | BCBS Michigan policy |
| No combination | Not to be used in combination with other targeted therapies for FOP such as Sohonos (palovarotene) | Medication list with start and stop dates of any FOP therapy | BCBS Michigan policy |
| Preferred drugs | Trial and failure, contraindication or intolerance to the preferred drugs on the BCBSM/BCN utilization management medical drug list; the policy document does not name them | Prior therapy history with outcomes | BCBS Michigan policy |
| Supporting records | Requests must be supported by chart notes and patient specific documentation | Chart notes | BCBS Michigan policy |
| Quantity and duration | Quantity limits align with FDA recommended dosing; authorization one year at a time | Current weight with date and the mg/kg dose | BCBS Michigan policy |
| Renewal | Clinical documentation that current criteria are met and that the medication is providing clinical benefit | Follow-up notes and any imaging | BCBS Michigan policy |
| Medicare Part B | Coverage and approval duration may differ under applicable LCDs or NCDs | Check the member's line of business | BCBS Michigan policy |
| Pending criteria | Blue Shield of California commercial, effective November 1, 2026: criteria pending P&T approval, medical necessity review in the interim | Office chart notes, lab results or other clinical information | Blue Shield of California policy |
| Trial population | OPTIMA (NCT05394116): clinical FOP diagnosis, documented ACVR1 FOP-causing mutation, FOP disease activity within 1 year of screening; CAJIS above 19 excluded | Flare-up or HO progression history and CAJIS, for a letter of medical necessity | ClinicalTrials.gov, OPTIMA |
| Published trial | OPTIMA was published in The Lancet, 2026;408(10564):1583-1592, online September 28, 2026 (Papa R, et al.) | Peer-reviewed citation for an appeal | Lancet paper |
| Pediatric requests | Not labeled under 18. OPTIMA-2 (NCT07559513), Phase 3 in ages 4 to under 18 at US sites (2 to under 18 outside the US), is listed as not yet recruiting with a planned start of February 2, 2027 | Date of birth; trial referral where relevant | ClinicalTrials.gov, OPTIMA-2 |
Pasatru dosing and titration
| When | Label | Source |
|---|---|---|
| Start | 10mg/kg IV over 60 minutes once every 4 weeks. | FDA label |
| Reduce | 3mg/kg IV over 60 minutes once every 4 weeks if 10mg/kg is not tolerated. | FDA label |
| Missed dose | Administer as soon as possible, then schedule once every 4 weeks from the date of the last dose. | FDA label |
| Preparation | Inspect; discard the vial if cloudy, discolored or particulate. Do not shake. Withdraw the required volume into a PVC, PO or EVA bag holding 50 to 100mL of 5% Dextrose Injection, USP, for a final 0.9 to 25mg/mL; mix by gentle inversion; discard any unused portion. | FDA label |
| Diluted solution | Use immediately, or store at 2 to 8°C (36 to 46°F) for no more than 24 hours, or at room temperature up to 25°C (77°F) for no more than 16 hours, from preparation to the start of infusion. Do not freeze. If refrigerated, allow to come to room temperature first. | FDA label |
| Administration | Infusion set of PVC, PE-lined PVC or PU; a sterile in-line or add-on 0.2 to 5 micron PES or PA filter is recommended; infusion pump to control the rate; flush the line with 5% Dextrose Injection, USP at the end. Do not mix other drugs with Pasatru or give them through the same line. | FDA label |
| Vials | 300mg/5mL (60mg/mL) single-dose vial, one per carton, NDC 61755-012-01. Arithmetic example: 60kg at 10mg/kg is 600mg, 2 vials. | FDA label |
| Storage | Unopened vials refrigerated at 2 to 8°C (36 to 46°F) in the original carton to protect from light. Do not freeze. Do not shake. | FDA label |
| Renal and hepatic | No dose adjustment is stated. No clinically meaningful exposure differences in mild to moderate renal or hepatic impairment; severe impairment is unstudied, and changes in renal or hepatic function are not expected to affect pharmacokinetics. | FDA label |
Monitoring the Pasatru label requires
| When | What | What the label says to do with it | Source |
|---|---|---|---|
| Before day 1 | Pregnancy status in females of reproductive potential | Required by section 2.1; contraindicated during pregnancy | FDA label |
| During and after treatment | Repeat pregnancy testing | Not in the prescribing information. Regeneron's myRARE safety information says the provider may ask for pregnancy tests periodically, as needed, throughout treatment and for at least 6 months after stopping | myRARE for Pasatru |
| Any time | Skin and soft tissue infection: erythema, pain, swelling or fever | Abscesses and cellulitis requiring treatment and/or hospitalization occurred in trials; advise patients to report signs and seek medical attention | FDA label |
| Any time | Spontaneous epistaxis | Advise medical attention if severe, prolonged (for example more than 20 minutes) and not resolved by standard first aid; 1 serious case in FOP trials required hospitalization for nasal packing and a clotting agent | FDA label |
| Counseling | Fetal risk and in utero exposure | Advise of the potential risk to a fetus (Highlights; section 5.1). Section 8.1: Pasatru may be present in infants exposed in utero, and the potential clinical impact of that exposure should be considered | FDA label |
| If pregnancy occurs | Discontinue immediately | Advise the patient to contact their healthcare provider; monkey ePPND study showed post-natal malformations, neurobehavioral deficits and infant mortality at clinical exposures | FDA label |
| Through week 56 | Abscess 35% on 10mg/kg, 11% on 3mg/kg, 10% placebo; acne 30%, 16%, 10%; increased hair growth 26%, 42%, 0; madarosis 26%, 16%, 19%; oral ulcers 26%, 5%, 5%; epistaxis 17%, 53%, 24% | Also folliculitis 9%, 16%, 10%; paronychia 4%, 11%, 0; rash 4%, 26%, 0; cellulitis in 1 patient (4%) on 10mg/kg (n = 23, 19 and 21) | FDA label |
| Steady state | Reached by about 12 weeks, accumulation about 1.7-fold; mean trough 99mg/L on 10mg/kg and 27mg/L on 3mg/kg | No pharmacodynamic studies have been conducted | FDA label |
| After stopping | Median time to non-detectable concentration about 24 weeks after 10mg/kg and 17 weeks after 3mg/kg | Contraception and no breastfeeding for 6 months after the last dose | FDA label |
| Immunogenicity | Anti-garetosmab-grts antibodies in 1.3% (1/76) over up to 76 weeks | Insufficient data to assess clinical effect | FDA label |
| Efficacy reference | New HO lesions at week 56 on low-dose whole-body CT: 19 on placebo, 2 on 10mg/kg, 1 on 3mg/kg; rate ratios 0.10 (95% CI 0.01 to 0.76) and 0.06 (0 to 0.73) | Clinician-assessed flare-ups 9, 53 and 66; rate ratio 0.12 (0.03 to 0.42) for 10mg/kg and 0.85 (0.26 to 2.73) for 3mg/kg. New HO volume difference was not statistically significant | FDA label |
| FDA summary | Second drug approved for FOP; Breakthrough Therapy, Fast Track, Orphan Drug and Priority Review designations | FDA lists nosebleeds, increased hair growth, abscess and acne as the most common adverse reactions | FDA announcement |
Pasatru drug interactions and contraindications
| Label category | Agents and what the label says | Source |
|---|---|---|
| Drug interactions | No drug-drug interaction studies have been conducted; the label has no section 7 | FDA label |
| Same IV line | Do not mix other drugs with Pasatru or administer other drugs concomitantly via the same infusion line | FDA label |
| Other targeted FOP therapy | BCBS Michigan's policy says Pasatru is not to be used in combination with other targeted therapies for FOP such as Sohonos (palovarotene) | BCBS Michigan policy |
| Lactation | Breastfeeding not recommended during treatment and for 6 months after the last dose | FDA label |
| Male fertility | May impair male fertility based on animal studies: reversible seminiferous tubule degeneration in monkeys, and male reproductive tract findings with decreased sperm motility in rats at exposures below clinical | FDA label |
| Geriatric | Too few patients 65 and older were studied to determine whether they respond differently | FDA label |
Why a first fill stalls, and the fix
- The patient is under 18The label covers adults with FOP and says safety and effectiveness in children have not been established. The FOP specialist can explain what that means for a younger patient.
- A pregnancy has not been ruled outThe label asks the prescriber to verify that a patient who can become pregnant is not pregnant before starting Pasatru. The Medication Guide says the healthcare provider will ask for a pregnancy test.
- No genetic test result with the requestBlue Cross Blue Shield of Michigan's policy asks for FOP confirmed by genetic testing that shows an ACVR1 mutation. The specialist's office sends that report, along with chart notes, when it asks the plan for approval.
- Another FOP medicine is on fileBlue Cross Blue Shield of Michigan's policy says Pasatru is not to be used with other targeted FOP therapies, such as Sohonos (palovarotene). The specialist's office can tell the plan which FOP medicines are being taken now.
- The plan wants its preferred drugs firstBlue Cross Blue Shield of Michigan's policy asks for trial and failure of, a contraindication to, or intolerance of its preferred drugs. The policy document does not name those drugs, so the specialist's office checks the plan's medical drug list.
- The plan has not set its rules yetBlue Shield of California's commercial policy, effective November 1, 2026, says its coverage criteria are pending committee approval. Until then it reviews every request for medical necessity and asks for chart notes, lab results or other clinical information.
- No infusion site is set up yetRegeneron's brochure says insurance coverage varies and that not all hospitals or infusion centers offer Pasatru. It suggests talking to your care team about which options are available to you.
- A cost you cannot payRegeneron's brochure says a Patient Navigator can tell you if you qualify for myRARE support programs or point to other financial assistance resources. The Pasatru pages we read did not publish copay amounts, income limits or rules for Medicare and Medicaid.
myRARE for Pasatru (Regeneron)
- The Pasatru line is also written 1-877-3PASATRU, and option 1 reaches myRARE
- Help navigating your insurance coverage
- Help with logistical challenges related to your treatment
- Connection to financial support options
- Help understanding your infusion coverage
- A Patient Navigator who helps explain your health insurance benefits and gives updates throughout the insurance approval process Regeneron patient brochure
- Treatment confirmations and updates by text message, and check-ins from the Patient Navigator about your treatment Regeneron patient brochure
- The Patient Navigator can let you know if you qualify for myRARE support programs or identify other financial assistance resources Regeneron patient brochure
- Regeneron's approval announcement also gives a general myRARE line, 1-833-469-7273 (1-833-4my-RARE) Regeneron press release
Questions prescribers' offices ask about Pasatru
What is the Pasatru dose?
10mg/kg as a 60-minute IV infusion once every 4 weeks, per the August 2026 label, decreased to 3mg/kg once every 4 weeks if 10mg/kg is not tolerated. Each single-dose vial holds 300mg/5mL (60mg/mL), and the label says to use an infusion pump to control the rate.
What has to happen before the first Pasatru infusion?
Section 2.1 of the August 2026 label requires 1 step, verifying that females of reproductive potential are not pregnant, because Pasatru is contraindicated during pregnancy. Advise effective contraception during treatment and for 6 months after the last dose. The label specifies no laboratory test, and there is no REMS.
How is Pasatru prepared and infused?
Dilute in 50 to 100mL of 5% Dextrose Injection to a final 0.9 to 25mg/mL, per section 2.3 of the August 2026 label, and mix by gentle inversion. Infuse over 60 minutes through a PVC, PE-lined PVC or PU set, with a 0.2 to 5 micron PES or PA filter recommended, then flush with 5% dextrose. Use immediately, or store up to 24 hours refrigerated or 16 hours at room temperature before the start of infusion.
What safety issues does the Pasatru label warn about?
The August 2026 label carries 3 warnings and no boxed warning: embryo-fetal toxicity, skin and soft tissue infections including abscess and cellulitis, and epistaxis. One serious case of spontaneous epistaxis in the FOP trials required hospitalization for nasal packing and a clotting agent. Pregnancy is the only contraindication.
What do insurers ask for to approve Pasatru?
Blue Cross Blue Shield of Michigan's policy, P&T date October 8, 2026, lists 5 criteria against the August 2026 label: FDA-approved indication, FDA-approved age, FOP confirmed by genetic testing showing an ACVR1 mutation, no combination with other targeted FOP therapy such as Sohonos, and trial, contraindication or intolerance to the plan's preferred drugs. Authorization runs one year at a time. Blue Shield of California's commercial policy, effective November 1, 2026, says criteria are pending and reviews requests for medical necessity.
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Sources
- PASATRU (garetosmab-grts) injection, for intravenous use, prescribing information and Medication Guide, Revised 8/2026, Regeneron Pharmaceuticals, via DailyMed, 2026-08-14.
- BLA 761508 approval letter, Pasatru (garetosmab-grts), FDA, 2026-08-19.
- FDA Approves Second Treatment for Fibrodysplasia Ossificans Progressiva, FDA, 2026-08-19.
- Pasatru™ (garetosmab-grts) First and Only FDA-approved Treatment Demonstrating Reduction in New Heterotopic Ossification (HO) Lesions and Clinician-Assessed Flare-ups in a Placebo-controlled Trial in Adults with Fibrodysplasia Ossificans Progressiva (FOP), Regeneron Pharmaceuticals, 2026-08-19.
- Pasatru, myRARE patient support program page, Regeneron Pharmaceuticals, 2026-11-11.
- PASATRU consumer brochure, US.GAR.26.05.0001, September 2026 version, Regeneron Pharmaceuticals, 2026-11-11.
- Pasatru (garetosmab-grts) medical benefit drug policy, P&T date 10/08/2026, Blue Cross Blue Shield of Michigan and Blue Care Network, 2026-10-08.
- garetosmab-grts (Pasatru) Commercial Medical Benefit Drug Policy, effective 11/01/2026, Blue Shield of California, 2026-11-01.
- A Study to Assess Safety, Tolerability and Efficacy of Garetosmab Versus Placebo Administered Intravenously (IV) in Adult Participants With Fibrodysplasia Ossificans Progressiva (FOP), NCT05394116, ClinicalTrials.gov, record updated July 17, 2026, 2026-07-17.
- A Study to Investigate the Safety, Pharmacokinetics (PK), and Efficacy of Garetosmab in Children and Adolescents With Fibrodysplasia Ossificans Progressiva (FOP), NCT07559513, ClinicalTrials.gov, record updated October 20, 2026, 2026-10-20.
- Efficacy and safety of garetosmab, an activin A-blocking antibody, in fibrodysplasia ossificans progressiva (OPTIMA): a randomised, double-blind, placebo-controlled, phase 3 trial, The Lancet, via PubMed, 2026-09-28.
A reference drawn from the August 14, 2026 label, the drugmaker's published program and one public insurer policy shown as an example, checked on November 11, 2026. Labels and policies change; the label on DailyMed and the plan's current policy govern. Trial Friend is not a medical provider. It reports what these documents say and does not judge whether a drug is safe or right for any patient; that is the prescriber's decision. Not a substitute for the prescribing information.