Prescribing guide
Fayuvi (rebisufligene etisparvovec-hopf)Anti-AAV9 screening, corticosteroid regimen, post-infusion liver and platelet monitoring, and prior authorization criteria for Sanfilippo syndrome type AFor prescribers and their offices treating sanfilippo syndrome type A: 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; administration at an Ultragenyx Qualified Treatment Center after anti-AAV9 total binding antibody titer below 1:100, baseline ALT, AST, GGT, bilirubin, platelets, PT and aPTT, infection control, no vaccines in the prior 30 days, a negative serum pregnancy test where applicable, and prednisone or prednisolone started the day before.
Example PA threshold
Cigna IP0849 example: no prior Fayuvi, MPS IIIA by SGSH variants or deficient sulfamidase, anti-AAV9 below 1:100, neurologist, medical geneticist or metabolic disease specialist, weight within 30 days, one lifetime dose with a 90-day approval.
Monitoring
LFTs weekly for 2 weeks then every 2 weeks until 2 weeks after the steroid taper; platelets weekly for 4 weeks then monthly for 6 months; TMA, infusion reaction and malignancy vigilance; vector shedding precautions for 3 months.
Support line
UltraCare, 1-888-756-8657, Gene Therapy Guides Monday to Friday 9 AM to 8 PM Eastern for benefits investigation, PA and appeal status, commercial Copay Assistance for drug and administration costs, and information on 501(c)(3) foundations.
Give your patient their plan
A one-page handout for starting Fayuvi, 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/fayuviBefore 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 | MPS IIIA with preserved neurodevelopmental function. The efficacy population was 2 years or younger at treatment, or older than 2 with a Bayley-III or Mullen cognitive DQ of 60 or higher; mean age at treatment 21.8 months, range 3.0 to 32.9 months. | FDA label |
| Test anti-AAV9 antibodies | Not recommended at a total binding titer of 1:100 or higher. No FDA-authorized assay exists and available tests vary; contact Ultragenyx at 1-888-756-8657 for testing information. | FDA label |
| Companion diagnostic | Ultragenyx committed to validate an FDA-authorized companion diagnostic for anti-AAV9 below 1:100; study completion December 31, 2028, final report June 30, 2029. | FDA letter |
| Baseline workup | ALT, AST, GGT, total bilirubin and liver history; platelets, PT and aPTT; conditions that raise corticosteroid risk. Delay until clinically significant infections are controlled. | FDA label |
| Vaccines | Review vaccination status; avoid vaccines for 30 days before treatment and while on corticosteroids. The schedule may need adjustment. | FDA label |
| Pregnancy test | A negative serum pregnancy test must be confirmed before administration in females of childbearing potential. | FDA label |
| Refer to a QTC | Fayuvi is available through Ultragenyx's network of Qualified Treatment Centers, U.S. institutions with gene therapy expertise and training. | Ultragenyx press release |
| Enroll in UltraCare | An assigned UltraCare Guide runs the benefits investigation, determines whether PA is required, tracks appeal status and searches for alternate coverage. | UltraCare |
| Order by weight | Each kit is one patient dose, NDC 69794-301-05 (5 vials, 2.5 to 3.0kg) through 69794-331-05 (105 vials, 66.1 to 70.0kg). Dose volume uses the upper limit of the weight band, rounded up to the nearest 2mL. | FDA label |
| REMS | None. FDA's review found no safety signal requiring a REMS or a required postmarketing safety study. | FDA review summary |
Prior authorization criteria and what to document
One public policy as the example: Cigna, October 16, 2026. Approval one dose per lifetime, with the approval open for 90 days to give it. This is Cigna's first policy for Fayuvi, effective October 16, 2026, and it cites the September 2026 label. It treats Fayuvi after any earlier gene therapy as not medically necessary. Its criteria do not spell out how to show preserved neurodevelopmental function, which is part of the label's approved use. It is here as an example of what a plan asks for, not as a rule.
| Element | What the policy asks | In the chart | Source |
|---|---|---|---|
| No prior Fayuvi | Verified in claims history, or the prescriber confirms the patient has not received it | Attestation in the request | Cigna policy |
| Diagnosis | MPS IIIA confirmed by molecular testing showing SGSH variants, or enzyme testing showing deficient or absent sulfamidase | Genetic or enzyme report [documentation required] | Cigna policy |
| Anti-AAV9 | Baseline anti-AAV9 titer less than 1:100 | Lab report with titer and date [documentation required] | Cigna policy |
| Prescriber | Neurologist, medical geneticist or metabolic disease specialist | Specialty on the request | Cigna policy |
| Weight | Current body weight obtained within the past 30 days | Dated weight [documentation required] | Cigna policy |
| Dose | One-time single dose of 3.0 × 10¹³ genome copies/kg; a Medical Director verifies weight-based dosing against the kit NDC table | Kit NDC matched to the weight band | Cigna policy |
| Not covered | Prior receipt of any gene therapy | History of prior gene therapy in the note | Cigna policy |
| Product | STN 125845, Ultragenyx Pharmaceutical Inc | The FDA product page links the package insert, approval letter and review documents | FDA product page |
| Coding | HCPCS C9399 or J3590 (unclassified drugs or biologicals) | Kit NDC on the claim | Cigna policy |
Fayuvi dosing and titration
| When | Label | Source |
|---|---|---|
| Day before | Prednisone or prednisolone 1.0mg/kg/day orally, continued for 8 weeks. | FDA label |
| Day 1 | 3.0 × 10¹³ vg/kg as a slow IV infusion over about 1 hour by syringe pump through a peripheral IV catheter with a 0.2µm in-line filter. No push or bolus, no other products in the line, no central line or port. A second IV catheter is recommended for reactions. Flush with Lactated Ringer's, Hartmann's or 0.9% sodium chloride at the last rate. | FDA label |
| Infusion reaction | Pause, give supportive care; restart at a slower rate after resolution at the provider's discretion. | FDA label |
| Week 8 onward | Taper slowly over at least 4 weeks if liver enzymes are at or below baseline; increase or prolong if rising or elevated; consult pediatric GI, hepatology or immunology if elevations persist. | FDA label |
| Preparation | Thaw at 20 to 25°C for at least 30 minutes, no water bath, no shaking, no overnight thaw. Drawn syringes are stable up to 24 hours at room temperature including infusion; an intact thawed vial may be refrigerated up to 12 days. Do not refreeze. | FDA label |
| Storage | Shipped and stored frozen at -60°C or colder, upright, in the original carton. | FDA label |
| Dating period | 24 months from date of manufacture when stored at -60°C or colder. | FDA letter |
| Over 70kg | Dosed at the 70kg weight. | FDA package insert |
Monitoring the Fayuvi label requires
| When | What | What the label says to do with it | Source |
|---|---|---|---|
| Weeks 1 and 2 | ALT, AST, GGT, total bilirubin weekly | Then every 2 weeks until 2 weeks after the taper ends; continue until baseline in anyone with elevations. Liver enzyme increases in 85% (23/27), first onset most often within 14 days, none with bilirubin elevation | FDA label |
| Weeks 1 to 4 | Platelets weekly | Then monthly for 6 months after infusion. Platelet count decreased in 19%; counsel that thrombocytopenia generally occurs within the first 2 weeks | FDA label |
| First 4 weeks and beyond | TMA: thrombocytopenia, hemolytic anemia, easy bruising, hypertension, seizures, decreased urine output, renal dysfunction | No TMA cases with Fayuvi in studies; reported with other AAV gene therapies. If suspected, consult pediatric hematology or nephrology immediately | FDA label |
| During and after infusion | Vital signs; hypotension, pyrexia, palpitation, nausea, vomiting, chills, headache, anaphylaxis | Pause and treat; restart slower once resolved | FDA label |
| Any time | Neutropenia | 22% (6/27), 1 grade 3 | FDA label |
| 3 months | Vector shedding in urine, saliva and stool | Median clearance 15, 30 and 84 days; counsel diaper sealing and hand hygiene for 3 months | FDA label |
| Long term | Malignancy | Possible from vector integration; report to Ultragenyx at 1-888-756-8657 | FDA label |
| Postmarketing | Expedited reporting | Ultragenyx files 15-day expedited reports of liver failure, TMA and malignancy for 3 years after licensure | FDA letter |
Fayuvi drug interactions and contraindications
| Label category | Agents and what the label says | Source |
|---|---|---|
| Vaccines | Avoid for 30 days before treatment and while on corticosteroids; adjust the schedule as needed | FDA label |
| Hepatotoxic agents | Counsel caregivers not to start medicines, herbals or supplements without confirming they are not hepatotoxic; if one seems unavoidable, they contact the prescriber to discuss alternatives | FDA label |
| Corticosteroids | Monitor and manage corticosteroid adverse reactions per their own labeling; adrenal insufficiency 7% and Cushingoid features 30% were reported | FDA label |
| Pregnancy | No data; women who are pregnant or wish to become pregnant should not be treated. No recommendation on contraception duration | FDA label |
| Fertility and carcinogenicity | No fertility studies in animals or humans; no animal carcinogenicity or mutagenicity studies | FDA label |
Why a first fill stalls, and the fix
- The AAV9 antibody level is 1:100 or higherThe label does not recommend Fayuvi at this level, and Cigna requires a baseline result below 1:100. This is a medical limit, not a paperwork problem, and the specialist can explain what it means for your child.
- The diagnosis is not documented as type ACigna asks for a genetic test showing SGSH variants or an enzyme test showing missing sulfamidase. The specialist's office sends the genetic or enzyme report to the plan.
- The prescriber is not the right kind of specialistCigna requires a neurologist, medical geneticist or metabolic disease specialist to prescribe Fayuvi. A referral to one of these specialists, or a consult note, fixes this.
- The weight on file is too oldCigna needs a body weight from the past 30 days, since the kit is built for that weight. The office weighs your child again and sends the new weight to Cigna.
- The approval ran out before the infusionCigna's approval covers one dose and stays open for 90 days. If scheduling slips past that window, the office asks Cigna for a new approval.
- Your child had another gene therapy beforeCigna does not cover Fayuvi after any earlier gene therapy, because Fayuvi was not studied in that group.
- Out-of-pocket costs you cannot payUltraCare's Copay Assistance program may cover out-of-pocket costs for the medicine and its administration for families with commercial insurance who meet Ultragenyx criteria. With government or commercial insurance, 501(c)(3) foundations may help with incidental medical costs related to the disease, and families apply to them directly.
UltraCare
- An UltraCare Guide assigned after you enroll, who helps you understand your insurance coverage
- Specially trained Gene Therapy Guides, now part of UltraCare, who also help arrange treatment support and answer questions about the treatment process Ultragenyx press release
- A full benefits investigation, a check on prior authorization, the status of any appeal and a search for other coverage
- Copay Assistance for commercial insurance that may cover out-of-pocket costs for the medicine and its administration, for patients who meet Ultragenyx criteria
- Information on 501(c)(3) foundations that may help with incidental medical costs related to the disease, for government or commercial insurance
- Patient Assistance programs whose details UltraCare explains by phone
Questions prescribers' offices ask about Fayuvi
What is the Fayuvi dose?
3.0 × 10¹³ vg/kg as a single IV infusion over approximately 1 hour, per the October 2026 label. Kits hold 5 to 105 vials of 2mL at 1.0 × 10¹³ vg/mL, sized by weight; patients over 70kg are dosed at 70kg.
What anti-AAV9 antibody result is needed before Fayuvi?
Below 1:100 total binding antibody titer; the October 2026 label does not recommend Fayuvi at 1:100 or higher, a group not evaluated. No FDA-authorized test is available; Ultragenyx (1-888-756-8657) gives testing information, and a companion diagnostic study is committed for completion by December 31, 2028.
What corticosteroid regimen goes with Fayuvi?
Prednisone or prednisolone 1.0mg/kg/day orally from 1 day before infusion for 8 weeks, then a slow taper over at least 4 weeks, per the October 2026 label. Taper after 8 weeks only if liver enzymes are at or below baseline; increase or prolong if rising, and consult pediatric GI, hepatology or immunology if elevations persist.
What monitoring does the Fayuvi label require after infusion?
ALT, AST, GGT and total bilirubin weekly for 2 weeks, then every 2 weeks until 2 weeks after the taper ends, per the October 2026 label. Platelets weekly for 4 weeks, then monthly for 6 months; continue LFTs in anyone with elevations until baseline.
What do insurers ask for to approve Fayuvi?
Cigna IP0849, effective October 16, 2026, asks for no prior Fayuvi, SGSH molecular or sulfamidase enzyme confirmation, baseline anti-AAV9 below 1:100, and a neurologist, medical geneticist or metabolic disease specialist. It also needs weight within 30 days and labeled weight-based dosing; approval is one lifetime dose with a 90-day window.
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Sources
- DailyMed - FAYUVI- rebisufligene etisparvovec-hopf kit (prescribing information, revised October 2026, SPL version 1), Ultragenyx, via DailyMed, 2026-10-01.
- Package Insert - FAYUVI, FDA, 2026-09-17.
- FAYUVI, FDA, Center for Biologics Evaluation and Research, 2026-10-15.
- September 17, 2026 Approval Letter - FAYUVI, FDA, 2026-09-17.
- September 17, 2026 Summary Basis for Regulatory Action - FAYUVI, FDA, 2026-09-17.
- Ultragenyx Announces Approval of FAYUVI™ Gene Therapy, the First-Ever FDA-Approved Treatment for Sanfilippo Syndrome Type A (MPS IIIA), Ultragenyx, 2026-09-17.
- Patient Services - UltraCare, Ultragenyx, 2026-11-09.
- Mucopolysaccharidosis – Gene Therapy – Fayuvi, Drug Coverage Policy IP0849, Cigna, 2026-10-16.
A reference drawn from the October 1, 2026 label, the drugmaker's published program and one public insurer policy shown as an example, checked on November 9, 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.