Anti-amyloid beta monoclonal antibody

Leqembi (lecanemab-irmb) Letter of Medical Necessity

Leqembi (lecanemab-irmb) is the first anti-amyloid Alzheimer's therapy with full FDA approval demonstrating slowed cognitive decline. Prior authorization is complex due to amyloid confirmation requirements, MRI safety monitoring, and Medicare CED enrollment requirements — and is one of the fastest-growing PA categories in neurology.

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FDA-Approved Indications

● Alzheimer's disease — mild cognitive impairment (MCI) or mild dementia stage with confirmed amyloid pathology

Why Leqembi Prior Authorization Gets Denied

The most common denial reasons across major payers:

1. Amyloid pathology not confirmed by PET scan or CSF biomarkers (Aβ42/40 ratio, p-tau)
2. Cognitive staging outside covered range (MCI or mild dementia only — not moderate or severe)
3. APOE ε4 genotype not documented (high-risk for ARIA)
4. Baseline MRI without gadolinium not performed within 1 year
5. Prescriber not a neurologist or geriatrician
6. Traditional Medicare CED (Coverage with Evidence Development) registry enrollment not completed for MA plans

What to Include in a Leqembi Letter of Medical Necessity

Document confirmed MCI or mild AD diagnosis with MMSE or MoCA scores, confirmed amyloid pathology by PET or CSF biomarkers (specify test, laboratory, and result), APOE ε4 genotyping with result, baseline MRI dated within 12 months showing no evidence of ARIA, neurologist or geriatrician prescriber, and for Medicare patients, enrollment in the LexArts or appropriate CED registry. Note any prior anti-amyloid therapy (aducanumab) history.

Key clinical evidence to cite:

✓ CLARITY AD Phase 3 trial — 27% slowing of cognitive decline on CDR-SB vs placebo at 18 months
✓ AHEAD 3-45 prevention trial (ongoing — for future label expansion)
✓ Amyloid clearance confirmed by PET: >60% of participants achieved amyloid-negative status by week 52

Relevant guidelines:

📖 Alzheimer's Association 2024 Appropriate Use Criteria for Anti-Amyloid Therapy
📖 CMS NCD 20.4 (Medicare National Coverage Determination for Leqembi)
📖 AAN Position Statement on Anti-Amyloid Immunotherapy

Leqembi Prior Authorization Criteria

Standard criteria across major US payers for Leqembi. Specific criteria vary by plan — RxCheckUp tailors each LMN to your patient's exact payer policy.

Typical step therapy requirements:

→ Documented failure or contraindication to formulary alternatives

Required documentation:

✓ ICD-10 diagnosis code with specificity
✓ Prior therapy history with dates, doses, and discontinuation reasons
✓ Specialist evaluation (where applicable)
✓ Baseline disease activity or biomarker results
✓ Clinical rationale citing FDA labeling or guidelines

Approval details:

Initial approval: typically 6 months. Renewal: 12 months with documented clinical response.

Payers Covering Leqembi

RxCheckUp tailors each LMN to the specific payer's medical policy and step therapy requirements:

UnitedHealthcareAetnaCignaBCBSMedicare Part B (traditional Medicare covers with conditions of coverage)Medicare Advantage

Leqembi Prior Authorization FAQ

Why was my Leqembi prior authorization denied?

The most common denial reasons for Leqembi are: Amyloid pathology not confirmed by PET scan or CSF biomarkers (Aβ42/40 ratio, p-tau); Cognitive staging outside covered range (MCI or mild dementia only — not moderate or severe); APOE ε4 genotype not documented (high-risk for ARIA); Baseline MRI without gadolinium not performed within 1 year; Prescriber not a neurologist or geriatrician; Traditional Medicare CED (Coverage with Evidence Development) registry enrollment not completed for MA plans.

What should a Leqembi Letter of Medical Necessity include?

Which payers cover Leqembi?

Leqembi is covered by major US payers including UnitedHealthcare, Aetna, Cigna, BCBS, Medicare Part B (traditional Medicare covers with conditions of coverage), Medicare Advantage, though formulary tier and prior authorization criteria vary.