ModifiedUnitedHealthcarePolicy CS2025D0105L

Amondys 45 (casimersen) for Duchenne muscular dystrophy

Medical benefit drug policy governing coverage criteria, applicable codes, and authorization parameters for Amondys 45 (casimersen) for treatment of Duchenne muscular dystrophy (DMD) amenable to exon 45 skipping, excluding certain state-specific policies.

Policy Summary

PayerUnitedHealthcare

PolicyAmondys 45 (casimersen) for Duchenne muscular dystrophy

Policy CodePolicy CS2025D0105L

Change TypeRevised coverage criteria

Effective DateJul 1, 2025

Next Review Date

Key ActionSubmit medical records confirming diagnosis, exon 45 amenable mutation, functional/ambulatory measures (6MWT ≥300 m or ambulatory without assistive device plus NSAA >17 or TTR <7s), and prior gene therapy status; initial authorization limited to no more than 12 months.

POLICY UPDATE CHANGES

Revised coverage criteria for initial therapy to add requirement that one of the following be met regarding prior gene therapy: either patient has not previously received gene therapy or, if previously received, documentation of clinically meaningful functional decline since gene therapy.

1Drug indicated

3Functional eligibility thresholds referenced

12Initial authorization months (max)

Coverage Summary

Policy CS2025D0105L governs coverage of Amondys 45 (casimersen) for Duchenne muscular dystrophy (DMD) patients with mutations amenable to exon 45 skipping. The policy is a medical benefit drug policy that covers therapy with criteria and specifies documentation and prior authorization requirements, applicable codes (e.g., HCPCS J1426, ICD-10 G71.01), and limits initial authorization to no more than 12 months. This policy was made effective on July 1, 2025 and last reviewed on July 1, 2025.

Key clinical thresholds

6-Minute Walk Test (6MWT)>= 300 meters

North Star Ambulatory Assessment (NSAA)> 17

Time to Rise (TTR)< 7 seconds

Initial authorization duration<= 12 months

Initial Therapy Criteria

Initial Therapy

Covered when ALL of the following are met:

Diagnosis and genetic confirmation
- Diagnosis of DMD: Diagnosis of Duchenne muscular dystrophy by, or in consultation with, a neurologist with expertise in the diagnosis of DMD
- Exon 45 amenable mutation: Submission of medical records (e.g., chart notes, laboratory values) confirming the mutation of the DMD gene is amenable to exon 45 skipping
One of the following functional/ambulatory criteria
- 6MWT criterion: Submission of medical records confirming that the patient has a 6-Minute Walk Test (6MWT) ≥ 300 meters while walking independently (e.g., without side-by-side assist, cane, walker, wheelchair, etc.) prior to beginning Amondys 45 therapy6MWT >= 300 meters
- Ambulatory without assistive device plus NSAA or TTR
  - Ambulatory without assistive device: Submission of medical records confirming that the patient is ambulatory without needing an assistive device (e.g., without side-by-side assist, cane, walker, wheelchair, etc.)
  - AND one of
    NSAA > 17: Patient has achieved a score of greater than 17 on the North Star Ambulatory Assessment (NSAA)NSAA > 17
    TTR < 7 seconds: Patient has achieved a time to rise (TTR) of less than 7 secondsTTR < 7 seconds
One of the following prior gene therapy conditions
- No prior gene therapy: Patient has not previously received gene therapy (e.g., Elevidys [delandistrogene moxparvovec-rokl]) for the treatment of DMD
- Prior gene therapy with documented decline
  - Prior gene therapy received: Patient has previously received gene therapy (e.g., Elevidys [delandistrogene moxparvovec-rokl]) for the treatment of DMD
  - Documentation of clinically meaningful decline: Submission of medical records documenting a clinically meaningful functional decline resulting from loss of muscle strength/motor ability (e.g., loss of a motor milestone) since receiving gene replacement therapy
Concomitant therapy prohibition: Amondys 45 is not used concomitantly with other exon skipping therapies for DMD (e.g., Exondys 51 [eteplirsen], Viltepso [viltolarsen], Vyondys 53 [golodirsen])
Specialist prescribing requirement: Prescribed by, or in consultation with, a neurologist with expertise in the treatment of DMD
Dosing and authorization duration: Dosing is in accordance with the United States Food and Drug Administration approved labeling
Initial authorization duration: Initial authorization will be for no more than 12 monthsInitial authorization <= 12 months

Unproven / Not Medically Necessary

Not covered when:

Unproven / Not Medically Necessary: Treatment of other forms of muscular dystrophy (e.g., Becker muscular dystrophy)

Applicable Codes

Drug HCPCSHCPCS

J1426

Injection, casimersen, 10 mg

Diagnosis Codes (referenced)ICD-10

G71.01

Duchenne or Becker muscular dystrophy

Provider Actions & Authorization Requirements

Prior Authorization

Prior authorization required for initial therapy

Submit medical records confirming diagnosis, exon 45 amenable mutation, functional/ambulatory measures (6MWT ≥300 m or ambulatory without assistive device plus NSAA >17 or TTR <7 s), and prior gene therapy status; initial authorization limited to no more than 12 months.

Affected codes: J1426, G71.01
Initial authorization limited to 12 months

Documentation Required

Documentation of exon 45 amenability

Provide medical records confirming the DMD gene mutation is amenable to exon 45 skipping.

Examples of acceptable documentation: chart notes, laboratory values

Documentation Required

Documentation if prior gene therapy received

If the patient previously received gene therapy, submit medical records documenting a clinically meaningful functional decline since gene replacement therapy.

Document loss of muscle strength or motor ability (e.g., loss of a motor milestone) since gene therapy
Include chart notes and relevant laboratory values

Denial Risk

Concomitant exon skipping therapies prohibited

Amondys 45 must not be used concomitantly with other exon skipping therapies for DMD; claims may be denied if used together.

Drug code: J1426
Examples of prohibited concomitant exon skipping therapies: eteplirsen, viltolarsen, golodirsen
Therapy may be denied or considered not covered if used concomitantly

Step Therapy

Specialist prescribing requirement

Must be prescribed by, or in consultation with, a neurologist with expertise in the treatment of DMD.

Clinical Evidence

Key evidence includes the ongoing 96-week, phase III, double-blind, placebo-controlled ESSENCE trial that evaluated ambulatory DMD patients with out-of-frame deletion mutations amenable to exon 45 skipping; the trial enrolled male patients able to ambulate with a mean 6-minute walk test between ≥ 300 m and ≤ 450 m and assessed change in 6MWT at 96 weeks as the primary endpoint. The FDA prescribing information is cited as Amondys 45 package insert, July 2024.

Background & Definitions

Casimersen is an antisense oligonucleotide indicated to treat DMD in patients with mutations in the exon 45 region of the dystrophin gene; it induces exon 45 skipping to permit production of a functional, albeit truncated, dystrophin protein. Clinical trials (ESSENCE) evaluated ambulatory males (age 6–13) who could ambulate and had a 6MWT between ≥ 300 m and ≤ 450 m, with stable pulmonary function and corticosteroid use prior to enrollment.

Term	Definition
Ambulatory without assistive device	Able to walk without side-by-side assist, cane, walker, wheelchair, etc.
Clinically meaningful functional decline	Loss of muscle strength/motor ability (e.g., loss of a motor milestone) since receiving gene replacement therapy

Revision History

2025-07-01policy_revisionLatest