CurrentSecurity Health Plan of Wisconsin, Inc.Policy SHP-0346

Mepsevii (vestronidase alfa-vjbk) for MPS VII

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This policy governs prior authorization, initial approval, renewal, dosing, administration, and billing requirements for intravenous Mepsevii used to treat mucopolysaccharidosis VII (MPS VII, Sly syndrome). It applies to members seeking coverage for this specialty enzyme replacement therapy.

Policy Summary

PayerSecurity Health Plan of Wisconsin, Inc.

PolicyMepsevii (vestronidase alfa-vjbk) for MPS VII

Policy CodePolicy SHP-0346

Change TypeNo material clinical or coverage changes

Effective DateN/A

Last ReviewApr 1, 2026

Next Review DateN/A

Key ActionSubmit supporting clinical documentation with every prior authorization request.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

12 moInitial authorization

12 moRenewal interval

460 mg/14 daysMaximum dose

4 mg/kg q2wkDosing regimen

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CurrentSecurity Health Plan of Wisconsin, Inc.Policy SHP-0346

Mepsevii (vestronidase alfa-vjbk) for MPS VII

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Policy Summary

PayerSecurity Health Plan of Wisconsin, Inc.

PolicyMepsevii (vestronidase alfa-vjbk) for MPS VII

Policy CodePolicy SHP-0346

Change TypeNo material clinical or coverage changes

Effective DateN/A

Last ReviewApr 1, 2026

Next Review DateN/A

Key ActionSubmit supporting clinical documentation with every prior authorization request.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

12 moInitial authorization

12 moRenewal interval

460 mg/14 daysMaximum dose

4 mg/kg q2wkDosing regimen

E76.29Diagnosis code

Coverage Criteria

Initial Therapy

Initial approval requires all criteria below.

Eligibility and baseline: Member is at least 5 months of age and documented age-appropriate baseline values have been obtained for one or more specified clinical measures.Age ≥ 5 months; one or more baseline measures documented

For very young members for whom forced vital capacity or the 6-minute walk test is unsuitable, requests are reviewed case by case.

Universal criteria: Therapy is being used to treat non-central nervous system manifestations of the disease, and the member does not have severe, irreversible cognitive impairment.

Requests for continued therapy in members with severe, irreversible cognitive impairment are reviewed case by case.

Definitive MPS VII diagnosis: MPS VII is confirmed by both beta-glucuronidase enzyme deficiency testing and molecular genetic detection of pathogenic or likely pathogenic GUSB variants.Both diagnostic components required

Enzyme deficiency may be demonstrated in peripheral blood leukocytes, fibroblasts, or dried blood spots.

Renewal Therapy

Renewal requires all criteria below.

Continued eligibility: Member continues to meet the universal and other relevant indication-specific criteria identified for initial approval, including applicable concomitant therapy requirements and performance status requirements.

Safety: There is an absence of unacceptable toxicity from the drug.

Examples of unacceptable toxicity include anaphylaxis and severe allergic reactions.

Beneficial response

Functional or organ response: Stability or improvement in the 6-minute walk test, shoulder flexion, pulmonary function tests, visual acuity, or motor functions such as BOT-2.Stable or improved from baseline

Initial therapy is not approved when Mepsevii is being used to treat central nervous system manifestations or when the member has severe, irreversible cognitive impairment. Requests for continued therapy in members with severe, irreversible cognitive impairment are reviewed on a case-by-case basis.

Coding and Billing

Covered HCPCS CodesHCPCSCovered

J3397

Injection, vestronidase alfa-vjbk, 1 mg

Covered NDC CodesNDCCovered

69794-0001-xx

Mepsevii 10 mg/5 mL single-dose vial

Covered Diagnosis CodesICD-10Covered

E76.29

Other mucopolysaccharidoses

Maximum HCPCS Units

Maximum quantity460 billable units

Equivalent amount460 mg

FrequencyEvery 14 days

Minimum Member Age

Minimum ageAt least 5 months of age

Approval requirementThe member must meet the minimum age requirement for initial approval

Age-related exception

Provider Requirements and Decision Points

Prior Authorization

12-Month Prior Authorization Required

Prior authorization is required for Mepsevii® therapy. Authorization is issued for an initial 12-month period and may be renewed in additional 12-month periods.

Initial authorization: 12 months (365 days).
Renewal authorization: every 12 months (365 days).

Documentation Required

Submit Medical Necessity Documentation

Submit supporting clinical documentation with every authorization request so medical necessity can be evaluated. Records should support the diagnosis, treatment rationale, step-therapy considerations, and clinical markers when applicable.

Medical records and chart notes.
Laboratory results and confirmatory diagnostics.
Genetic or mutational testing and other clinical markers, when applicable.

Therapy Background

Mepsevii (vestronidase alfa-vjbk) is an intravenous enzyme replacement therapy used to treat mucopolysaccharidosis VII, also known as MPS VII or Sly syndrome. The policy addresses treatment of non-central nervous system manifestations of this disease and requires definitive biochemical and molecular confirmation of MPS VII.

Definitions

Mucopolysaccharidosis VII (MPS VII; Sly Syndrome)

DiseaseMucopolysaccharidosis VII

Alternate nameSly syndrome

Policy indicationThe disease indication addressed for Mepsevii coverage

GUSB Gene

GeneGUSB

Diagnostic roleMolecular genetic testing must detect pathogenic or likely pathogenic variants in the GUSB gene

Required confirmationGUSB variant detection is required together with beta-glucuronidase enzyme deficiency testing to confirm MPS VII

Mepsevii Initial Therapy

Initial Mepsevii therapy is covered when all criteria below are met.

Age and baseline eligibility: Member is at least 5 months of age and has documented age-appropriate baseline values for one or more disease measures.Age ≥ 5 months; one or more baseline measures documented

Measures may include the 6-minute walk test, motor function testing such as BOT-2, liver and/or spleen volume, urinary glycosaminoglycan excretion, skeletal involvement or Z-score, pulmonary function tests, shoulder flexion, or visual acuity. For very young members in whom forced vital capacity or the 6-minute walk test is unsuitable, requests are reviewed case by case.

Universal clinical criteria: Therapy is being used to treat non-central nervous system manifestations of MPS VII, and the member does not have severe, irreversible cognitive impairment.

Requests for continued therapy in members with severe, irreversible cognitive impairment are reviewed case by case.

Mepsevii Continuation Therapy

Continuation of Mepsevii requires all criteria below.

Acceptable safety: There is an absence of unacceptable toxicity from Mepsevii.

Examples of unacceptable toxicity include anaphylaxis and severe allergic reactions.

Beneficial response

Functional response: Stability or improvement in the 6-minute walk test, shoulder flexion, pulmonary function tests, visual acuity, or motor functions such as BOT-2.Stable or improved from baseline

Quantity Limits

Mepsevii Quantity Limit

DrugMepsevii

Maximum quantity460 billable units, corresponding to 460 mg

Quantity intervalEvery 14 days

Administration Site and Schedule

Note

Administer in an infusion center

Administer Mepsevii as an intravenous infusion every 2 weeks in an infusion center.

The policy dose is 4 mg/kg administered by intravenous infusion every 2 weeks.

Policy Summary

PayerSecurity Health Plan of Wisconsin, Inc.

PolicyMepsevii (vestronidase alfa-vjbk) for MPS VII

Policy CodePolicy SHP-0346

Change TypeNo material clinical or coverage changes

Effective DateN/A

Last ReviewApr 1, 2026

Next Review DateN/A

Key ActionSubmit supporting clinical documentation with every prior authorization request.

SourceLink

On This Page

Organ-volume response: Reduction in liver and/or spleen volume.Reduction from baseline

Biochemical response: Reduction in urinary excretion of glycosaminoglycans.Reduction from baseline

Skeletal response: Stability of skeletal disease, including improvement in Z-score.Stable disease or improved Z-score

Very young members whose forced vital capacity or 6-minute walk test is unsuitable are reviewed case by case

Baseline Clinical Measurements

Documentation requirementOne or more age-appropriate baseline values must be documented

Examples of measures6-minute walk test, motor function, liver or spleen volume, urinary glycosaminoglycan excretion, skeletal involvement, pulmonary function, shoulder flexion, or visual acuity

Young-member considerationWhen forced vital capacity or the 6-minute walk test is unsuitable, the request is reviewed case by case

Dose

Dose4 mg/kg

RouteIntravenous infusion

FrequencyEvery 2 weeks

Upload records through the PA web portal or submit them by fax.

Documentation Required

Document Baseline Clinical Measurements

Document age-appropriate baseline measurements before initiating therapy. At least one qualifying disease measure must be submitted with the request.

6-minute walk test (6-MWT).
Motor function, such as the Bruininks-Oseretsky Test of Motor Proficiency (BOT-2).
Liver and/or spleen volume.
Urinary glycosaminoglycan (GAG) excretion, including chondroitin sulfate and dermatan sulfate.
Skeletal involvement, such as Z-score.
Pulmonary function tests.
Shoulder flexion or visual acuity.
For very young members for whom FVC or 6-MWT is unsuitable, submit the request for case-by-case review.

Documentation Required

Confirm MPS VII Diagnosis

Confirm MPS VII (Sly Syndrome) with both required diagnostic components before requesting therapy. The diagnosis must be supported by enzyme deficiency testing and molecular genetic testing.

Beta-glucuronidase enzyme deficiency in peripheral blood leukocytes, fibroblasts, or dried blood spots.
Pathogenic or likely pathogenic variants in the GUSB gene detected by molecular genetic testing.

Documentation Required

Document Response for Renewal

For renewal, submit evidence that the member remains eligible, is tolerating therapy, and has experienced a beneficial response compared with pretreatment age-appropriate baseline values.

Continued fulfillment of universal and indication-specific criteria, including applicable concomitant-therapy and performance-status requirements.
Documented stability or improvement in 6-MWT, shoulder flexion, pulmonary function, visual acuity, or motor function such as BOT-2.
Reduction in liver and/or spleen volume or urinary GAG excretion.
Stable skeletal disease or improvement in Z-score.

Denial Risk

Missing Clinical Documentation Can Result in Denial

Failure to submit the required clinical records may result in denial because the plan cannot establish medical necessity under the policy.

Ensure all records supporting diagnosis, treatment purpose, baseline measures, and confirmatory testing are included with the request.
Incomplete submissions may be denied for insufficient documentation.

Denial Risk

Initial Criteria Not Met

Initial authorization may be denied when the member does not satisfy the required age, baseline measurement, treatment-purpose, diagnostic, or other initial-approval conditions.

Member is younger than 5 months.
No documented age-appropriate baseline value is submitted for at least one qualifying disease measure.
Therapy is not being used for non-central nervous system manifestations, or the member has severe, irreversible cognitive impairment; continued-therapy requests in such cases are reviewed case by case.
MPS VII is not definitively confirmed by both beta-glucuronidase enzyme deficiency testing and GUSB molecular genetic testing.
Other applicable initial criteria, including required supporting documentation, are not met.

Denial Risk

Renewal Criteria Not Met

Renewal may be denied when the member no longer meets applicable eligibility criteria, develops unacceptable toxicity, or lacks evidence of beneficial response compared with pretreatment baseline values.

Universal or indication-specific renewal criteria are no longer met.
Unacceptable toxicity is present, including anaphylaxis or severe allergic reactions.
No demonstrated stability or improvement in functional, pulmonary, visual, skeletal, organ-volume, or urinary GAG measures.

Definitive MPS VII diagnosis:

Member has a definitive diagnosis of MPS VII confirmed by both beta-glucuronidase enzyme deficiency and molecular genetic detection of pathogenic or likely pathogenic variants in the GUSB gene.

Both diagnostic components required

Enzyme deficiency testing may be performed in peripheral blood leukocytes, fibroblasts, or dried blood spots.

Organ-volume response: Reduction in liver and/or spleen volume.Reduction from baseline

Biochemical response: Reduction in urinary excretion of glycosaminoglycans.Reduction from baseline

Skeletal response: Stability of skeletal disease, including improvement in Z-score.Stable disease or improved Z-score