CurrentQualChoicePolicy CP.PHAR.587

Pegzilarginase-nbln (Loargys) coverage

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Defines medical necessity criteria, authorization requirements, dosing, and coverage limits for Loargys (pegzilarginase-nbln) for treatment of arginase 1 deficiency in members of QualChoice lines of business.

Policy Summary

PayerQualChoice

PolicyPegzilarginase-nbln (Loargys) coverage

Policy CodePolicy CP.PHAR.587

Change TypeMaterial clinical and operational updates

Effective DateFeb 23, 2026

Next Review DateAug 25, 2025

Key ActionSubmit prior authorization with supporting documentation including recent plasma arginine, genetic confirmation or reduced RBC arginase activity, current weight in kg, and provider attestation of diet adherence.

SourceLink

POLICY UPDATE CHANGES

Added criterion requiring documentation of member's current weight in kg for initial approval.

Extended initial approval duration for Medicaid/HIM/ICHRA to 12 months and revised Commercial approval durations to '6 months or to the member's renewal date, whichever is longer'.

Added HCPCS codes C9399 and J3590 to the policy for billing reference.

≥2 yrsMinimum age for coverage

0.2 mg/kg/wkMaximum allowable dosing

12 moApproval duration (Medicaid/HIM/ICHRA)

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CurrentQualChoicePolicy CP.PHAR.587

Pegzilarginase-nbln (Loargys) coverage

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Policy Summary

PayerQualChoice

PolicyPegzilarginase-nbln (Loargys) coverage

Policy CodePolicy CP.PHAR.587

Change TypeMaterial clinical and operational updates

Effective DateFeb 23, 2026

Next Review DateAug 25, 2025

SourceLink

POLICY UPDATE CHANGES

Added criterion requiring documentation of member's current weight in kg for initial approval.

Extended initial approval duration for Medicaid/HIM/ICHRA to 12 months and revised Commercial approval durations to '6 months or to the member's renewal date, whichever is longer'.

Added HCPCS codes C9399 and J3590 to the policy for billing reference.

≥2 yrsMinimum age for coverage

0.2 mg/kg/wkMaximum allowable dosing

12 moApproval duration (Medicaid/HIM/ICHRA)

Coverage Criteria

inv-01: Initial Therapy — covered when ALL criteria are met

Covered when ALL of the following are met

Initial Approval for ARG1-D: 1) Diagnosis of ARG1-D confirmed by genetic confirmation of an ARG1 pathogenic variant OR documentation of reduced arginase enzyme activity in red blood cells; 2) Prescribed by or in consultation with a neurologist or physician experienced in treating metabolic disorders; 3) Age ≥ 2 years; 4) Provider attestation that member is currently adherent to a protein-restricted diet and will continue this diet during treatment with Loargys; 5) Documentation of plasma arginine level from within the last 3 months; 6) Documentation of member's current weight in kg; 7) Dose does not exceed 0.2 mg/kg once weekly.max dose 0.2 mg/kg/week

All conditions must be met for approval

inv-02: Continuation Therapy — covered when ALL criteria are met

Covered when ALL of the following are met

Continuation Approval for ARG1-D: 1) Member meets one of the following: a) currently receiving medication via Centene benefit or previously met initial approval criteria; OR b) member is currently receiving medication and is enrolled in a state/product with continuity of care regulations; 2) Member is responding positively to therapy as evidenced by a reduction in plasma arginine levels since initiation of therapy; 3) Provider attestation that member has been adherent to a protein-restricted diet and will continue this diet during treatment with Loargys; 4) If request is for a dose increase, the new dose does not exceed 0.2 mg/kg once weekly.max dose 0.2 mg/kg/week

All conditions must be met for continued approval

Requests for use of this medication for non‑FDA approved indications that are not explicitly addressed in this policy should be routed per the policy's off‑label and formulary guidance. If the drug has had a recent label change within the last 6 months that is not reflected here, follow the applicable formulary/no‑coverage or non‑formulary policies listed; otherwise, refer to the off‑label use policy for the member's line of business (Commercial: CP.CPA.09; HIM/ICHRA: HIM.PA.154; Medicaid: CP.PMN.53) for consideration of coverage.

Use of this agent for diagnoses or indications that are not listed in this policy and for which sufficient evidence of efficacy and safety is not provided is not authorized. Such requests should be evaluated under the referenced off‑label or formulary/non‑formulary policies for the applicable line of business; absent adequate supporting evidence per those policies, the request may be considered not medically necessary.

Initial Therapy (ARG1-D)

inv-13: Initial Therapy (ARG1-D) — nested initial therapy requirements specific to ARG1-D

Covered when ALL of the following are met

Initial Therapy (ARG1-D): 1) Diagnosis of ARG1-D confirmed by genetic confirmation of an ARG1 pathogenic variant OR documentation of reduced arginase enzyme activity in red blood cells; 2) Prescribed by or in consultation with a neurologist or physician experienced in treating metabolic disorders; 3) Age ≥ 2 years; 4) Provider attestation that member is currently adherent to a protein-restricted diet and will continue this diet during treatment with Loargys; 5) Documentation of plasma arginine level from within the last 3 months; 6) Documentation of member's current weight in kg; 7) Dose does not exceed 0.2 mg/kg once weekly.max dose 0.2 mg/kg/week

All conditions must be met for approval

Continuation / Continued Therapy (ARG1-D)

inv-14: Continued Therapy (ARG1-D) — nested continuation criteria for ARG1-D

Covered when ALL of the following are met

Continued Therapy (ARG1-D): 1) Member meets one of the following: a) currently receiving medication via Centene benefit or previously met initial approval criteria; OR b) member is currently receiving medication and is enrolled in a state/product with continuity of care regulations; 2) Member is responding positively to therapy as evidenced by a reduction in plasma arginine levels since initiation of therapy; 3) Provider attestation that member has been adherent to a protein-restricted diet and will continue this diet during treatment with Loargys; 4) If request is for a dose increase, the new dose does not exceed 0.2 mg/kg once weekly.max dose 0.2 mg/kg/week

All conditions must be met for continued approval

Provider Actions and Requirements

Prior Authorization

Prior authorization required; bill with C9399 or J3590

Prior authorization is required for Loargys. For billing of unclassified drug/biologic services, reference HCPCS codes C9399 (Unclassified drugs or biologicals) and J3590 (Unclassified biologics).

Submit a completed prior authorization request before dispensing or administering Loargys.

Step Therapy

Off‑label or formulary/non‑formulary routing required

If the requested use is not listed among the indications in this policy, route the request per the referenced off-label or formulary/non‑formulary policies for the applicable line of business.

Commercial off‑label policy: CP.CPA.09 (see policy references).
HIM/ICHRA off‑label policy: HIM.PA.154.
Medicaid off‑label policy: CP.PMN.53.
If drug/formulary status has changed recently, follow the no coverage criteria or non‑formulary policies listed in chunk 6.

Coding and Laboratory Targets

HCPCS codes referencedHCPCS

C9399	Unclassified drugs or biologicals
J3590	Unclassified biologics

Pre-dose plasma arginine target range

Target rangeAim pre-dose plasma arginine near the upper limit of normal (normal range 40–115 μM)

Dose adjustment — low levelIf pre-dose plasma arginine is <50 μM, reduce the weekly dosage by 0.05 mg/kg

Dose adjustment — high levelIf pre-dose plasma arginine is >150 μM, increase the weekly dosage by 0.05 mg/kg

Monitoring timingMeasure pre-dose plasma arginine after 4 weeks (168 hours after prior dose) to assess need for dose adjustment; require two consecutive weekly pre-dose measurements outside target to prompt change

Site of Care and Administration

Note

Infusion center or home: start IV; may switch to SC after 8 weeks

Initiate therapy with IV dosing; after eight weeks of once‑weekly IV administration, patients may be switched to once‑weekly subcutaneous dosing at the same weekly dose.

Recommended starting IV dose: 0.1 mg/kg IV once weekly (per dosing section).
After 8 weeks of once‑weekly IV, switch to once‑weekly SC at the same dosage if appropriate.

Step Therapy / Routing

Step	Requirement / Routing
1	If the requested use is not listed under indications, follow the off‑label or formulary/non‑formulary routing per the referenced policies: refer to off‑label use policies (CP.CPA.09, HIM.PA.154, CP.PMN.53) or the appropriate no‑coverage/non‑formulary policy when a recent label change or formulary status applies (CP.CPA.190, HIM.PA.33, CP.PMN.255, HIM.PA.103, CP.PMN.16).
Not listed	When the requested use is 'not listed', route per the applicable off‑label or formulary/non‑formulary policy referenced above for the member's line of business.

Definitions

arginase 1 deficiency

TermArginase 1 deficiency (ARG1‑D)

PathophysiologyInherited deficiency of arginase 1 leading to hyperargininemia

Approved indicationIndication targeted by this policy: hyperargininemia due to arginase 1 deficiency in patients age ≥2 years (Loargys)

AbbreviationCommon abbreviation: ARG1‑D

Background

Arginase 1 deficiency (ARG1‑D) is an inherited metabolic disorder characterized by deficient arginase‑1 activity leading to hyperargininemia. Loargys (pegzilarginase‑nbln) is a recombinant human arginase 1 enzyme replacement therapy approved for treatment of ARG1‑D in patients aged ≥2 years under accelerated approval based on reduction in plasma arginine. Continued approval may require confirmatory trial evidence; clinicians should follow the policy's documentation and monitoring requirements when requesting authorization.

Revision History

2026-03-24criteria_updateLatest

Added requirement to document member's current weight in kg for initial approval and updated criteria per FDA labeling following drug approval.

2026-02-23effective_date

Policy effective date set to 2026-02-23 per brief metadata.

2025-04-15annual_review