CurrentCareSourcePolicy N/A

Mepsevii (vestronidase alfa-vjbk) Coverage Criteria

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Medical prior authorization coverage for Mepsevii for CareSource Arkansas PASSE members with mucopolysaccharidosis type VII (MPS VII, Sly Syndrome), including authorization criteria, reauthorization, dosing, duration, and medical-necessity requirements.

Policy Summary

PayerCareSource

PolicyMepsevii (vestronidase alfa-vjbk) Coverage Criteria

Policy CodePolicy N/A

Change TypeAnnual review — no updates

Effective DateOctober 1, 2026

Last ReviewMay 13, 2026

Next Review DateNot specified

Key ActionMedical prior authorization is required for Mepsevii (vestronidase alfa-vjbk).

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

MepseviiDrug requiring medical prior authorization

MPS VIICovered disease indication

4 mg/kgAllowed dose per administration

Every 2 weeksIntravenous infusion frequency

6 months

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CurrentCareSourcePolicy N/A

Mepsevii (vestronidase alfa-vjbk) Coverage Criteria

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Know when CareSource releases new policies or updates existing guidance.

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Policy Summary

PayerCareSource

PolicyMepsevii (vestronidase alfa-vjbk) Coverage Criteria

Policy CodePolicy N/A

Change TypeAnnual review — no updates

Effective DateOctober 1, 2026

Last ReviewMay 13, 2026

Next Review DateNot specified

Key ActionMedical prior authorization is required for Mepsevii (vestronidase alfa-vjbk).

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

MepseviiDrug requiring medical prior authorization

MPS VIICovered disease indication

4 mg/kgAllowed dose per administration

Every 2 weeksIntravenous infusion frequency

6 months

Initial authorization duration

12 monthsReauthorization duration

Coverage Criteria

Initial Therapy

Covered for initial authorization when ALL of the following requirements are met. If approved, authorization is for 6 months.

ALL of the following

Medication is prescribed by or in consultation with a geneticist, metabolic specialist, or pediatrician experienced with managing mucopolysaccharidoses.
ONE of the following confirms MPS VII diagnosis
- Low beta-glucuronidase (GUS) enzyme activity.
- Molecular genetic testing reveals a pathogenic mutation of the GUSB gene.
Member has elevated urinary glycosaminoglycan (uGAG) excretion.
Dosage is 4 mg/kg administered by intravenous infusion every two weeks.
Quantity limit/dosing allowance.

Continuation Therapy

Covered for continuation therapy when ALL of the following requirements are met. If approved, authorization is for an additional 12 months.

ALL of the following

Chart notes show reduced urinary glycosaminoglycan (uGAG) excretion level.
Improvement or stabilization from baseline in at least ONE of the following
- Six-minute walk test (6MWT).
- Forced vital capacity (FVC).
- Motor function.
- Visual acuity.

CareSource considers Mepsevii (vestronidase alfa-vjbk) not medically necessary for the treatment of conditions that are not listed in this policy. For any other indication, refer to the Off-Label policy.

Dosing and Administration

Mepsevii dosage

Dose4 mg/kg

RouteIntravenous infusion

FrequencyEvery two weeks

Authorization and Documentation

Prior Authorization

Medical Prior Authorization Required

Medical prior authorization is required for Mepsevii (vestronidase alfa-vjbk) under the CareSource Arkansas PASSE medical benefit.

Documentation Required

Initial Authorization Documentation

For initial authorization, submit documentation showing that Mepsevii is prescribed by or used in consultation with an appropriate specialist and that the member meets the diagnostic and laboratory requirements for MPS VII.

Prescriber or consultant is a geneticist, metabolic specialist, or pediatrician experienced in managing mucopolysaccharidoses.
MPS VII diagnosis is confirmed by low beta-glucuronidase (GUS) enzyme activity or molecular genetic testing showing a pathogenic GUSB mutation.
Member has elevated urinary glycosaminoglycan (uGAG) excretion.
Requested dosing is 4 mg/kg by intravenous infusion every two weeks; initial approval is for 6 months when all requirements are met.

Clinical Background

Mepsevii (vestronidase alfa-vjbk) is an enzyme replacement therapy approved for the treatment of mucopolysaccharidosis type VII (MPS VII), also known as Sly Syndrome. MPS VII is a rare lysosomal storage disorder caused by GUSB gene mutations and deficient beta-glucuronidase activity, leading to accumulation of glycosaminoglycans such as heparan sulfate, dermatan sulfate, and chondroitin sulfate. Severe phenotypes may include hydrops fetalis.

Key Definitions

MPS VII / Sly Syndrome

Full nameMucopolysaccharidosis type VII

Also known asSly Syndrome

Disease typeRare lysosomal storage disorder

Underlying deficiencyDeficient beta-glucuronidase activity associated with GUSB gene mutations

ERT

TermEnzyme replacement therapy (ERT)

PurposeReplaces deficient lysosomal enzyme activity

Initial Authorization Criteria

Initial Authorization

For initial authorization, all requirements must be met:

Initial authorization

Accepted diagnostic confirmation: Low beta-glucuronidase (GUS) enzyme activity.
Accepted diagnostic confirmation: Molecular genetic testing reveals a pathogenic mutation of the GUSB gene.

Reauthorization Criteria

Reauthorization

For reauthorization, all requirements must be met:

Continuation criteria: Chart notes must show reduced urinary glycosaminoglycan (uGAG) excretion level; and improvement or stabilization compared with baseline in at least one of the following: six-minute walk test (6MWT), forced vital capacity (FVC), motor function, visual acuity, hepatosplenomegaly, or fatigue.

If all requirements are met, approve for an additional 12 months.

Quantity and Frequency Limits

Quantity limits

DrugMepsevii (vestronidase alfa-vjbk)

Allowed dose4 mg/kg per infusion

Infusion frequencyAdministered by intravenous infusion every two weeks

Policy Summary

PayerCareSource

PolicyMepsevii (vestronidase alfa-vjbk) Coverage Criteria

Policy CodePolicy N/A

Change TypeAnnual review — no updates

Effective DateOctober 1, 2026

Last ReviewMay 13, 2026

Next Review DateNot specified

Key ActionMedical prior authorization is required for Mepsevii (vestronidase alfa-vjbk).

SourceLink

On This Page

Documentation Required

Reauthorization Documentation

For reauthorization, submit chart notes documenting the required treatment response and clinical status compared with baseline.

Reduced uGAG excretion level.
Improvement or stabilization in at least one of the following: six-minute walk test (6MWT), forced vital capacity (FVC), motor function, visual acuity, hepatosplenomegaly, or fatigue.
Approval may be extended for an additional 12 months when all reauthorization requirements are met.

Denial Risk

Unlisted or Off-Label Indication

Mepsevii is not medically necessary for conditions or indications not listed in this policy. Requests for another indication may be denied unless they meet the applicable requirements of CareSource’s Off-Label policy.

Review the Off-Label policy before submitting a request for an unlisted or off-label indication.

Denial Risk

Initial Clinical Criteria Not Met

Initial authorization may be denied when any required authorization element is not documented.

No prescription by or consultation with a geneticist, metabolic specialist, or experienced pediatrician managing mucopolysaccharidoses.
MPS VII is not confirmed by low GUS enzyme activity or pathogenic GUSB mutation on molecular genetic testing.
Elevated urinary glycosaminoglycan (uGAG) excretion is not documented.
Requested dosing exceeds 4 mg/kg by intravenous infusion every two weeks.

Denial Risk

Continuation Response Criteria Not Met

Reauthorization may be denied when the required treatment response or stabilization is not documented.

Chart notes do not show reduced uGAG excretion.
No improvement or stabilization from baseline is documented in at least one required clinical measure: 6MWT, FVC, motor function, visual acuity, hepatosplenomegaly, or fatigue.

Policy applicationMepsevii is an enzyme replacement therapy for MPS VII

GAGs

Full nameGlycosaminoglycans (GAGs)

Heparan sulfateAccumulates in MPS VII

Dermatan sulfateAccumulates in MPS VII

Chondroitin sulfateAccumulates in MPS VII