How do Medicare Advantage prior authorization rules affect access to Leqembi and donanemab?
Executive summary
Medicare’s national coverage determinations mean FDA‑approved amyloid‑targeting drugs such as Leqembi (lecanemab) and donanemab are eligible for Medicare payment, but Medicare Advantage plans frequently layer prior‑authorization requirements, registries and monitoring rules that can delay or complicate real-world access and change out‑of‑pocket obligations for patients [1] [2] [3]. Ongoing prior‑authorization reform that takes effect in 2026 may speed and standardize decisions, but until then the combination of plan‑level PA, clinical documentation demands and cost‑sharing differences creates uneven access across beneficiaries [4] [5] [6].
1. Medicare approval opened the door, but plan rules set the tempo
Traditional FDA approvals for Leqembi and donanemab triggered Medicare coverage under CMS rules, but coverage is conditioned on clinicians participating in CMS’s registry and meeting monitoring requirements; CMS directed that FDA‑approved monoclonal antibodies be covered when clinicians enter data into the registry, which creates a paperwork and participation threshold even for beneficiaries with Medicare coverage [3] [2]. CMS also notes Original Medicare beneficiaries face the standard 20% Part B coinsurance after deductible, while costs “may be different” for those in Medicare Advantage plans, signaling that MA design can materially affect access and affordability [1].
2. Prior authorization is a practical gatekeeper in Medicare Advantage
Many Medicare Advantage carriers place Leqembi and donanemab on their Part B prior‑authorization lists, meaning a treating clinician must obtain plan approval before infusion; Devoted Health’s 2026 PA list explicitly includes codes for both lecanemab and donanemab, showing this is common practice among MA plans [5]. These PA protocols typically require submission of clinical documentation that mirrors CMS criteria but can add plan‑specific forms, attestations and timelines, making authorization a potentially time‑consuming administrative hurdle [7] [8].
3. Registry and safety monitoring requirements add administrative and clinical barriers
CMS’s coverage links payment to clinician participation in a monoclonal‑antibody registry and to safety monitoring such as baseline and periodic brain MRIs; commercial policies and prior‑authorization forms likewise demand attestations that clinicians are in the CMS registry and will follow MRI monitoring schedules, which increases the number of visits, tests and documentation steps before and during therapy [7] [8]. For frail or rural patients, the logistical burden of repeated imaging and specialist visits—combined with authorization waits—can be a substantive barrier not captured by simple “coverage” statements.
4. Cost sharing and plan variability change patient calculus
Original Medicare’s 20% coinsurance after the Part B deductible applies to Leqembi under CMS guidance, but Medicare Advantage plans can structure cost sharing and supplemental benefits differently, and some MA designs may impose higher cost‑sharing or separate utilization rules; CMS itself flags that costs “may be different” for those in Medicare Advantage [1]. Independent reporting and payor documents note list prices are high and beneficiaries without Medigap could face substantial out‑of‑pocket exposure, so PA plus cost‑sharing policies together influence who will accept or be able to afford treatment [9] [1].
5. Reform promises to streamline, but implementation timing matters
CMS’s Interoperability and Prior Authorization Final Rule and related 2026 reforms require certain payers to implement electronic prior‑authorization systems and reporting by January 1, 2026, and CMS is piloting programs aimed at reducing inappropriate utilization; proponents say these changes will speed decisions and increase transparency, which could lessen delays for MA beneficiaries seeking Leqembi or donanemab [4] [6]. Critics and provider groups warn that implementation complexity and the persistence of plan‑specific clinical criteria mean disparities in access may persist until systems and practices fully adapt [10] [6].
6. Alternative paths and limits of current reporting
Some payers and state Medicaid programs may cover Leqembi without the federal registry demands that CMS set for Medicare, creating geographic and programmatic variation in access; reporting notes Medicaid “might cover Leqembi in some cases—without requiring the prescribing doctor to enter patient data into a federal registry,” underscoring that payer type matters [11]. Available sources document policy, lists and requirements but do not measure how long authorizations take in practice, how many MA plans deny or delay these drugs, or the ultimate impact on patient uptake—those implementation outcomes are outside the provided reporting and thus not asserted here.