CurrentBluecross IdahoPolicy MP 5.01.651

Vestronidase alfa-vjbk (Mepsevii) for Mucopolysaccharidosis

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Defines medical necessity and authorization criteria for coverage of vestronidase alfa-vjbk (Mepsevii) for treatment of mucopolysaccharidosis VII (MPS VII) under Blue Cross of Idaho benefit plans.

Policy Summary

PayerBluecross Idaho

PolicyVestronidase alfa-vjbk (Mepsevii) for Mucopolysaccharidosis

Policy CodePolicy MP 5.01.651

Change TypeNo material changes

Effective DateMay 28, 2026

Last ReviewMay 28, 2026

Next Review DateMay 28, 2026

Key ActionObtain prior authorization with documentation of definitive MPS VII diagnosis, patient age ≥5 months, and baseline clinical measures.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

4 mg/kgrecommended IV dose every 2 weeks

12 monthsapproval length

≥5 monthsminimum age

23development program

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CurrentBluecross IdahoPolicy MP 5.01.651

Vestronidase alfa-vjbk (Mepsevii) for Mucopolysaccharidosis

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Defines medical necessity and authorization criteria for coverage of vestronidase alfa-vjbk (Mepsevii) for treatment of mucopolysaccharidosis VII (MPS VII) under Blue Cross of Idaho benefit plans.

Policy Summary

PayerBluecross Idaho

PolicyVestronidase alfa-vjbk (Mepsevii) for Mucopolysaccharidosis

Policy CodePolicy MP 5.01.651

Change TypeNo material changes

Effective DateMay 28, 2026

Last ReviewMay 28, 2026

Next Review DateMay 28, 2026

Key ActionObtain prior authorization with documentation of definitive MPS VII diagnosis, patient age ≥5 months, and baseline clinical measures.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

4 mg/kgrecommended IV dose every 2 weeks

12 monthsapproval length

≥5 monthsminimum age

23development program

Coverage Criteria

Initial Therapy

Covered when ALL of the following are met for initial therapy

Initial Criteria: 1. Definitive diagnosis of MPS VII confirmed by BOTH beta-glucuronidase enzyme deficiency in peripheral blood leukocytes AND detection of pathogenic GUSB gene mutations by molecular genetic testing; AND 2. Patient aged 5 months or older; AND 3. Documented baseline value for one or more relevant clinical measures (e.g., six minute walk test [6MWT], motor function such as BOT-2, liver and/or spleen volume, urinary excretion of glycosaminoglycans [GAGs], skeletal involvement, pulmonary function tests).

Length of Approval: 12 months

Continuation / Renewal Therapy

Renewal covered when ALL of the following are met

Renewal Criteria: 1. Patient continues to meet the initial criteria; AND 2. Absence of unacceptable toxicity from the drug (examples include anaphylaxis or severe allergic reactions); AND 3. Patient has responded to therapy compared to pretreatment baseline in one or more clinical measures (e.g., stability or improvement in 6MWT and/or motor function, reduction in liver and/or spleen volume, reduction in urinary excretion of GAGs, stability of skeletal disease, stability or improvement in pulmonary function tests).

Length of Approval: 12 months

This medical policy does not necessarily apply to all lines of business. Specifically, the policy may be excluded from coverage rules for the Federal Employee Program (FEP), Medicare Supplement, Medicare Advantage, Medicaid, and certain self‑insured employer groups. Providers must confirm member eligibility and plan‑specific coverage terms before submitting prior authorization requests or claims, as authorization requirements and benefit determinations can vary by line of business.

Initial Therapy

Initial authorization criteria

Initial: 1) Definitive diagnosis of MPS VII confirmed by BOTH beta-glucuronidase enzyme deficiency in peripheral blood leukocytes AND detection of pathogenic GUSB gene mutations by molecular genetic testing; 2) Patient age ≥5 months; 3) Documented baseline value for one or more relevant clinical measures (e.g., 6MWT, BOT-2 motor function, liver/spleen volume, urinary GAGs, skeletal involvement, pulmonary function tests).

Approval: 12 months

Continuation / Renewal Therapy

Continuation Therapy

Renewal requirements for ongoing coverage

Renewal: Continuation requires: 1) patient continues to meet the initial criteria; 2) absence of unacceptable toxicity (e.g., anaphylaxis, severe allergic reactions); and 3) documented clinical response versus pretreatment baseline in one or more measures as defined in the policy (stability or improvement in 6MWT/motor function, reduction in liver/spleen volume, reduction in urinary GAGs, stability of skeletal disease, stability or improvement in pulmonary function tests).

Approval duration: 12 months

Coding

HCPCSHCPCS

J3590

Unclassified Biologics

ICD-10ICD-10

E76.29

Other mucopolysaccharidoses

inv-06: Minimum patient age

Minimum patient agePatient must be aged 5 months or older.

Approval durationLength of approval for initial and renewal authorizations: 12 months.

Age evidenceAge must be documented in the medical record at time of request.

Provider Actions & Authorization

Prior Authorization

Prior authorization required for initial and renewal therapy

Prior authorization is required for vestronidase alfa-vjbk. Initial approval is granted only when the diagnostic criteria (definitive MPS VII diagnosis), patient age (≥5 months), and required baseline clinical documentation are met; authorizations are issued for 12 months. Renewal requires continued fulfillment of initial criteria, evidence of clinical response versus pretreatment baseline, and absence of unacceptable toxicity.

Initial approval: definitive diagnosis (enzyme deficiency + pathogenic GUSB mutations), age ≥5 months, and documented baseline clinical measure(s) — Length of approval: 12 months.
Renewal: patient continues to meet initial criteria; absence of unacceptable toxicity (e.g., anaphylaxis, severe allergic reactions); documented response to therapy versus pretreatment baseline — Length of approval: 12 months.

Billing Rule

Definitions

inv-17: Definitive diagnosis of MPS VII

Required laboratory confirmationBeta-glucuronidase enzyme deficiency in peripheral blood leukocytes is required.

Genetic testingDetection of pathogenic mutations in the GUSB gene by molecular genetic testing is required.

Diagnostic ruleBoth enzyme deficiency AND pathogenic GUSB mutations must be documented to confirm definitive diagnosis of MPS VII.

inv-18: Vestronidase alfa-vjbk (Mepsevii)

Drug name and brandVestronidase alfa-vjbk (Mepsevii).

MechanismRecombinant human beta-glucuronidase (rhGUS) enzyme replacement therapy providing exogenous GUS for lysosomal uptake.

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by inherited deficiencies of specific lysosomal enzymes required to degrade glycosaminoglycans (GAGs). Enzyme deficiency leads to progressive accumulation of GAGs in tissues and organs with multisystem manifestations. Vestronidase alfa‑vjbk (Mepsevii) is a recombinant human beta‑glucuronidase enzyme replacement therapy intended to provide exogenous enzyme for cellular uptake (via mannose‑6‑phosphate pathways) to catabolize accumulated GAGs. For MPS VII, the policy requires a definitive diagnosis confirmed by both documented beta‑glucuronidase enzyme deficiency in peripheral blood leukocytes and detection of pathogenic GUSB gene mutations; patients must be at least 5 months of age to meet initial therapy criteria.

Site of Care

Note

Infusion center — premedication and site‑of‑care guidance

Infusions should follow the policy guideline to premedicate with non‑sedating antihistamines with or without antipyretics 30–60 minutes before infusion; site‑of‑care is not specifically restricted in this section.

Premedicate 30–60 minutes prior to infusion with non‑sedating antihistamine ± antipyretic.
No specific site‑of‑care restriction provided in this policy section.

Policy Summary

PayerBluecross Idaho

PolicyVestronidase alfa-vjbk (Mepsevii) for Mucopolysaccharidosis

Policy CodePolicy MP 5.01.651

Change TypeNo material changes

Effective DateMay 28, 2026

Last ReviewMay 28, 2026

Next Review DateMay 28, 2026

Key ActionObtain prior authorization with documentation of definitive MPS VII diagnosis, patient age ≥5 months, and baseline clinical measures.

SourceLink

On This Page

Plan-specific prior authorization and coding guidance

Coverage determinations and prior authorization requirements are subject to the member-specific benefit plan. Coding guidance (for reference) lists HCPCS J3590 and ICD-10 E76.29, but inclusion of codes is for general reference only and does not guarantee coverage or reimbursement.

Codes provided for reference: HCPCS J3590 (Unclassified Biologics) and ICD-10 E76.29 (Other mucopolysaccharidoses).
Follow member-specific benefit plan documentation and additional terms and conditions when submitting prior authorization and claims.

Note

Benefit exceptions may limit applicability

This medical policy may not apply to all lines of business; authorization requirements and applicability can vary by line of business such as the Federal Employee Program, Medicare Supplement, Medicare Advantage, Medicaid, and certain self‑insured groups.

Confirm authorization requirements with the member's specific line of business before submitting requests.

Note

Provider action: confirm diagnosis, document baselines, and verify benefits

Providers must confirm definitive diagnostic testing and document baseline measures when requesting authorization; inclusion of codes in policy guidance does not guarantee coverage and providers should follow member-specific plan rules.

Definitive diagnosis requires BOTH beta-glucuronidase enzyme deficiency in peripheral blood leukocytes and detection of pathogenic GUSB mutations.
Reference codes (J3590, E76.29) are provided for submission guidance only—verify member benefits and billing requirements.

Documentation Required

Required clinical documentation — baseline and response measures

Document a baseline value for at least one relevant clinical measure (e.g., 6MWT, BOT-2, liver/spleen volume, urinary GAGs, skeletal involvement, pulmonary function tests) as part of the initial authorization; renewal requires documented response versus pretreatment baseline.

At initial request, include documented baseline for one or more measures listed in policy.
For renewal, provide evidence of stability or improvement in one or more measures compared to pretreatment baseline.

Billing Rule

Coding and documentation guidance (J3590, E76.29)

When submitting claims and authorization requests, reference HCPCS J3590 (Unclassified Biologics) and ICD-10 E76.29 (Other mucopolysaccharidoses) as guidance; however, providers must follow member-specific benefit plan documentation and other applicable policies.

HCPCS: J3590 — Unclassified Biologics.
ICD-10: E76.29 — Other mucopolysaccharidoses.
The policy states codes are for general reference and may not be all‑inclusive; verify billing requirements per plan.

Prior Authorization

Diagnosis confirmation required for authorization

Authorization requires confirmation of MPS VII by BOTH beta‑glucuronidase enzyme deficiency in peripheral blood leukocytes and detection of pathogenic GUSB gene mutations; absence of these findings can trigger denial of the request.

Include laboratory evidence of enzyme deficiency and molecular genetic testing demonstrating pathogenic GUSB mutations with the authorization.

Denial Risk

Toxicity may exclude renewal

Unacceptable toxicity (for example, anaphylaxis or severe allergic reactions) may preclude renewal of authorization and can lead to denial of continued therapy.

Document absence of unacceptable toxicity at renewal; if such toxicity is present, renewal may be denied.

Denial Risk

Coverage coding disclaimer — codes do not guarantee payment

The inclusion of a code in the policy does not guarantee member coverage or provider reimbursement; all benefit coverage determinations remain subject to the member-specific benefit plan documentation, legal requirements, and other applicable policies.

Use codes as reference only and verify coverage and reimbursement with the member's benefit plan prior to billing.

Uptake mediated via mannose-6-phosphate (M6P) residues enabling binding to cell surface receptors and delivery to lysosomes.

inv-19: E76.29 — ICD-10 code definition referenced

ICD-10 codeE76.29

DescriptionOther mucopolysaccharidoses.

Usage guidanceCode provided for general reference in this policy and may be used for documentation of MPS-related diagnoses.