Lecanemab-irmb (Leqembi)

Number: 1026

Table Of Contents

Policy
Applicable CPT / HCPCS / ICD-10 Codes
Background
References

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Policy

Scope of Policy

This Clinical Policy Bulletin addresses lecanemab-irmb (Leqembi) for commercial medical plans. For Medicare criteria, see Medicare Part B Criteria.

Note: Requires Precertification: 

Precertification of lecanemab-irmb (Leqembi) is required of all Aetna participating providers and members in applicable plan designs. For precertification of lecanemab-irmb (Leqembi), call (866) 752-7021 or fax (888) 267-3277. For Statement of Medical Necessity (SMN) precertification forms, see Specialty Pharmacy Precertification. 

Note: Site of Care Utilization Management Policy applies. For information on site of service for lecanemab-irmb (Leqembi), see Utilization Management Policy on Site of Care for Specialty Drug Infusions. 

1. Exclusions

   Aetna considers members with any of the following conditions as an exclusion and not eligible for Leqembi:

   1. Suspected neurodegenerative etiology of cognitive impairment other than Alzheimer’s disease (AD), including but not limited to frontotemporal lobar degeneration (FTLD) or Lewy body disease (i.e., meeting consensus criteria for possible or probable dementia with Lewy bodies that lack AD biomarkers of a positive amyloid positron emission tomography (PET) or cerebrospinal fluid (CSF) profile);
   2. Greater than 4 cerebral microbleeds, cortical superficial siderosis, or a major vascular contribution to cognitive impairment confirmed via magnetic resonance imaging (MRI);
   3. Cerebral contusion, encephalomalacia, brain aneurysm or other vascular malformation, central nervous system (CNS) infection, or brain tumor;
   4. History of transient ischemic attacks (TIA), stroke, uncontrolled hypertension, or seizures within the past 12 months;
   5. Bleeding disorder that is not under adequate control (including a platelet count less than 50,000 or international normalized ratio [INR] greater than 1.5);
   6. Immunologic disorder requiring therapy with immunoglobulins, monoclonal antibodies, immunosuppressants, or plasmapheresis.

   Leqembi will not be used in combination with any other amyloid beta-directed antibodies (e.g., aducanumab, donanemab).

2. Prescriber Specialties

   This medication must be prescribed by or in consultation with a geriatrician, neurologist, psychiatrist, or neuropsychiatrist.

3. Criteria for Initial Approval

   Aetna considers lecanemab-irmb (Leqembi) medically necessary for the treatment of Alzheimer’s Disease (AD) [except as outlined in Section I for exclusions] when all of the following criteria are met:

   1. Member must meet one of the following criteria:

      1. Member is 50 years of age or older; or
      2. If less than 50 years of age, member has a genetic mutation in amyloid precursor protein (APP), presenilin-1 (PSEN1), or presenilin-2 (PSEN2), or other clinical documentation to support early onset AD; and
   2. Member must have Clinical Stage 3 (cognitive impairment with early functional impact) or Clinical Stage 4 (dementia with mild functional impact) AD (see Appendix A); and
   3. Member must have objective evidence of cognitive impairment at baseline; and
   4. Member must have one of the following scores at baseline on any of the following assessment tools:
      
      
      1. Clinical Dementia Rating-Global Score (CDR-GS) of 0.5 or 1 (see Appendix B); or
      2. Mini-Mental Status Examination (MMSE) score of 21 - 30 (see Appendix C); or 
      3. Montreal Cognitive Assessment (MoCA) score of greater than or equal to 16 (see Appendix D); and

   5. Member must meet one of the following criteria:

      1. Have a positron emission tomography (PET) scan confirming the presence of amyloid pathology; or
      2. Have results from a lumbar puncture confirming at least one of the following detected in cerebrospinal fluid (CSF) as determined by the lab assay:
         
         
         1. Low AB42/AB40 ratio; or
         2. Elevated P-tau/AB42 ratio; or
         3. Elevated T-tau/AB42 ratio; and
   6. Member must have a recent brain magnetic resonance imaging (MRI) within one year prior to initiating treatment to evaluate for pre-existing Amyloid Related Imaging Abnormalities (ARIA); and
   7. Member will not use the requested medication in combination with anticoagulants including warfarin, heparin, and direct oral anticoagulants (e.g., dabigatran, rivaroxaban, edoxavan, apiximab, betrixaban); and
   8. If there is concurrent use of antiplatelet agents (e.g., aspirin up to 325 mg/day, clopidogrel, prasugrel, ticagrelor), member will use antiplatelet agent as monotherapy at a standard therapeutic dose (i.e., not using as dual agent antiplatelet therapy); and
   9. Member has undergone genotype testing to determine apolipoprotein E ε4 (ApoE ε4) status prior to initiation of the requested medication to inform member of the risk of developing ARIA; and 
   10. Member and/or provider must currently be participating in a provider-enrolled patient registry that collects information on treatments for Alzheimer’s disease (e.g., Alzheimer’s Network for Treatment and Diagnostics (ALZ-NET)).

   Aetna considers all other indications as experimental, investigational, or unproven.

4. Continuation of Therapy

   Aetna considers continuation of lecanemab-irmb (Leqembi) therapy medically necessary for treatment of Alzheimer’s Disease (AD) [except as outlined in Section I for exclusions] when the criteria outlined below are met.

   1. Continuation of therapy for 12 months (first reauthorization after the initial 7-month approval period) when all of the following criteria are met: 

      1. Member has met all initial authorization criteria at the time of initial approval; and
      2. Member has been evaluated for evidence of amyloid-related imaging abnormalities (ARIA) on MRI within approximately one week prior to the 3rd, 5th dose, 7th dose, and 14th dose (see Appendix E)
         
         

         1. For members with radiographic evidence of amyloid related imaging abnormalities-edema (ARIA-E):

            1. Dosing may continue based on clinical judgment, if applicable, for members that meet the following criteria:

               Member has mild ARIA-E on MRI and is asymptomatic or has mild clinical symptoms; or 

            2. Dosing should be suspended until MRI demonstrates radiographic resolution and symptoms resolve for members that meet any of the following criteria:

               1. Member has mild ARIA-E on MRI and has moderate or severe clinical symptoms; or
               2. Member has moderate ARIA-E on MRI and is asymptomatic or has mild, moderate, or severe clinical symptoms; or
               3. Member has severe ARIA-E on MRI and is asymptomatic or has mild, moderate, or severe clinical symptoms; or

         2. For members with radiographic evidence of amyloid related imaging abnormalities-hemosiderin deposition (ARIA-H):

            1. Dosing may continue for members that meet the following criteria:

               Member has mild ARIA-H on MRI and is asymptomatic; or

            2. Dosing should be suspended until MRI demonstrates radiographic stabilization and symptoms resolve for members that meet any of the following criteria:

               1. Member has mild ARIA-H on MRI and is symptomatic; or
               2. Member has moderate ARIA-H on MRI and is asymptomatic or symptomatic; or
               3. Member has severe ARIA-H on MRI and is asymptomatic or symptomatic; and

      3. Member and/or provider continues to participate in a provider-enrolled patient registry that collects information on treatments for Alzheimer’s disease (e.g., Alzheimer’s Network for Treatment and Diagnostics (ALZ-NET)).

   2. Continuation of therapy for 12 months (reauthorizations beyond initial 19 months of therapy) when all of the following criteria are met:

      1. Member has met all initial authorization criteria at the time of initial approval; and
      2. Member has a positive clinical response as evidenced by stabilization or slowing of disease progression as documented by any of the following (Note: Repeat assessment tool(s) must be the same tool that was submitted upon initial request):
         
         
         1. CDR-Global Score (i.e., score of 0.5 or 1); or
         2. MMSE (i.e., decline of 3 points or less per year); or
         3. MoCA (i.e., score of greater than or equal to 16); and

         Note: Continuation requests for members with assessment scores outside of the provided ranges (i.e. mild dementia) or who have progressed greater than the provided rate of decline may be reviewed on a case-by-case basis.

      3. Member and/or provider continues to participate in a provider-enrolled patient registry that collects information on treatments for Alzheimer’s disease (e.g., Alzheimer’s Network for Treatment and Diagnostics (ALZ-NET)).

5. Related CMS Coverage Guidance

   This Clinical Policy Bulletin (CPB) supplements but does not replace, modify, or supersede existing Medicare Regulations or applicable National Coverage Determinations (NCDs) or Local Coverage Determinations (LCDs). The supplemental medical necessity criteria in this CPB further define those indications for services that are proven safe and effective where those indications are not fully established in applicable NCDs and LCDs. These supplemental medical necessity criteria are based upon evidence-based guidelines and clinical studies in the peer-reviewed published medical literature. The background section of this CPB includes an explanation of the rationale that supports adoption of the medical necessity criteria and a summary of evidence that was considered during the development of the CPB; the reference section includes a list of the sources of such evidence. While there is a possible risk of reduced or delayed care with any coverage criteria, Aetna believes that the benefits of these criteria – ensuring patients receive services that are appropriate, safe, and effective – substantially outweigh any clinical harms.

   Code of Federal Regulations (CFR):

   42 CFR 417; 42 CFR 422; 42 CFR 423.

   
   
   

   Internet-Only Manual (IOM) Citations:

   CMS IOM Publication 100-02, Medicare Benefit Policy Manual; CMS IOM Publication 100-03 Medicare National Coverage Determination Manual.

   
   
   

   Medicare Coverage Determinations:

   Centers for Medicare & Medicaid Services (CMS), Medicare Coverage Database [Internet]. Baltimore, MD: CMS; updated periodically. Available at: Medicare Coverage Center. Accessed November 7, 2023.

6. Related Policies

   For subcutaneous lecanemab (Leqembi IQLIK), see pharmacy benefit plan.

   See also:

   1. CPB 0071 - Positron Emission Tomography (PET)
   2. CPB 0140 - Genetic Testing
   3. CPB 0349 - Alzheimer's Disease Tests
   4. CPB 0788 - Alzheimer's Disease: Experimental Treatments
   5. CPB 0996 - Aducanumab-avwa (Aduhelm)
   6. CPB 1066 - Donanemab-azbt (Kisunla).

Dosage and Administration

Lecanemab-irmb is available as Leqembi (for intravenous infusion) and Leqembi IQLIK (for subcutaneous injection). The dosage and strengths include the following:

• Leqembi intravenous (IV) infusion administered by a healthcare professional 

  • 500 mg/5 mL (100 mg/mL) solution in a single-dose vial
  • 200 mg/2 mL (100 mg/mL) solution in a single-dose vial;

• Leqembi IQLIK subcutaneous (SC) injection for self-administration, may be administered by a caregiver

  • 360 mg/1.8 mL (200 mg/mL) in a single-dose prefilled IQLIK autoinjector.

Labeled administration instructions include the following:

• Confirm the presence of amyloid beta pathology prior to initiating treatment
• Obtain a recent baseline brain MRI prior to initiating treatment
• Obtain an MRI within approximately one week prior to the 3rd, 5th, 7th, and 14th infusions. If radiographically observed ARIA occurs, treatment recommendations are based on type, severity, and presence of symptoms
• Recommended starting dosage is 10 mg/kg once every 2 weeks administered after dilution as an IV infusion over approximately one hour.
• After 18 months, continue treatment once every 2 weeks or transition to an IV or SC maintenance dosing. If transitioning from starting dosage to a maintenance dosage regimen, the first maintenance dose is administered 2 weeks after the last starting dose.
• During maintenance dosage regimen, individuals may switch the route of administration (IV or SC). This transition should be initiated at 1 week following the last maintenance dose of either the IV or SC dosing regimen.
• Recommended maintenance dosage:
  
  
  • IV infusion is 10 mg/kg once every 4 weeks; or
  • SC injection is 360 mg administered once a week using the Leqembi IQLIK autoinjector.

See Table 1 and 2 for labeled recommendations for dosing interruptions in persons with amyloid related imaging abnormalities (ARIA). See Appendix E for ARIA MRI Classification Criteria.

Table 1: Dosing Recommendations for Persons with Amyloid Related Imaging Abnormalities-Edema (ARIA-E)

Clinical Symptom SeverityFootnote1*	ARIA-E Severity on MRIFootnote2**
	Mild	Moderate	Severe
Asymptomatic	May continue dosing	Suspend dosingFootnote3***	Suspend dosingFootnote3***
Mild	May continue dosing based on clinical judgment	Suspend dosingFootnote3***
Moderate or Severe	Suspend dosingFootnote3***

Footnote1* Mild: discomfort noticed, but no disruption of normal daily activity. Moderate: discomfort sufficient to reduce or affect normal daily activity. Severe: incapacitating, with inability to work or to perform normal daily activity.

Footnote2** See Appendix E for MRI radiographic severity

Footnote3*** Suspend until MRI demonstrates radiographic resolution and symptoms, if present, resolve; consider a follow-up MRI to assess for resolution 2 to 4 months after initial identification. Resumption of dosing should be guided by clinical judgment.

Table 2: Dosing Recommendations for Persons with Amyloid Related Imaging Abnormalities-Hemosiderin Deposition (ARIA-H)

Clinical Symptom Severity	ARIA-H Severity on MRIFootnote4†
	Mild	Moderate	Severe
Asymptomatic	May continue dosing	Suspend dosingFootnote5††	Suspend dosingFootnote6†††
Symptomatic	Suspend dosingFootnote5††	Suspend dosingFootnote5††

Footnote4† See Appendix E for MRI radiographic severity.

Footnote5†† Suspend until MRI demonstrates radiographic stabilization and symptoms, if present, resolve; resumption of dosing should be guided by clinical judgment; consider a follow-up MRI to assess for stabilization 2 to 4 months after initial identification.

Footnote6††† Suspend until MRI demonstrates radiographic stabilization and symptoms, if present, resolve; use clinical judgment in considering whether to continue treatment or permanently discontinue Leqembi.

In persons who develop intracerebral hemorrhage greater than 1 cm in diameter during treatment with Leqembi, suspend dosing until MRI demonstrates radiographic stabilization and symptoms, if present, resolve. Per the label, use clinical judgment in considering whether to continue treatment after radiographic stabilization and resolution of symptoms or permanently discontinue Leqembi.

Source: Eisai, 2025

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Table:

CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
Other CPT codes related to the CPB:
0445U	B-amyloid (Abeta42) and phospho tau (181P) (pTau181), electro chemiluminescent immunoassay (ECLIA), cerebral spinal fluid, ratio reported as positive or negative for amyloid pathology
62270	Spinal puncture, lumbar, diagnostic
70551	Magnetic resonance (eg, proton) imaging, brain (including brain stem); without contrast material
70552	with contrast material(s)
70553	without contrast material, followed by contrast material(s) and further sequences
78608	Brain imaging, positron emission tomography (PET); metabolic evaluation
81401	Molecular pathology procedure, Level 2 common variants (eg, R3500Q, R3500W) APOE (apolipoprotein E) (eg, hyperlipoproteinemia type III, cardiovascular disease, Alzheimer disease)
81405	Molecular pathology procedure, Level 6 full gene sequence PSEN1 (presenilin 1) (eg, Alzheimer disease)
81406	Molecular pathology procedure, Level 7 full gene sequence APP (amyloid beta [A4] precursor protein) (eg, Alzheimer disease), full gene sequence PSEN2 (presenilin 2 [Alzheimer disease 4]) (eg, Alzheimer disease)
96365 – 96368	Intravenous infusion administration
96413 - 96417	Chemotherapy administration
HCPCS codes covered if selection criteria are met:
J0174	Injection, lecanemab-irmb, 1 mg
HCPCS codes not covered for indications listed in the CPB:
Oral anticoagulants (e.g., dabigatran, rivaroxaban, edoxavan, apiximab, betrixaban) -no specific code
J1642	Injection, heparin sodium, (Heparin Lock Flush), per 10 units
J1643	Injection, heparin sodium (pfizer), not therapeutically equivalent to J1644, per 1000 units
J1644	Injection, heparin sodium, per 1,000 units
Other HCPCS codes related to the CPB:
A9586	Florbetapir f18, diagnostic, per study dose, up to 10 millicuries
A9598	Positron emission tomography radiopharmaceutical, diagnostic, for non-tumor identification, not otherwise classified
Q9982	Flutemetamol F18, diagnostic, per study dose, up to 5 millicuries
S3852	DNA analysis for APOE epsilon 4 allele for susceptibility to Alzheimer's disease
ICD-10 codes covered if selection criteria are met:
G30.0 – G30.9	Alzheimer's disease
G31.84	Mild cognitive impairment of uncertain or unknown etiology [due to AD or mild AD dementia]
ICD-10 codes not covered for indications listed in the CPB:
C70.0	Malignant neoplasm of cerebral meninges
C71.0 - C71.9	Malignant neoplasm of brain
C79.31 – C79.32	Secondary malignant neoplasm of brain and cerebral meninges
D33.0 - D33.2	Benign neoplasm of brain
D43.0 – D43.2	Neoplasm of uncertain behavior of brain
D49.6	Neoplasm of unspecified behavior of brain
D69.0 – D69.9	Purpura and other hemorrhagic conditions
G23.0 – G23.9	Other degenerative diseases of basal ganglia
G31.01 – G31.83, G31.85 – G31.9	Other degenerative diseases of nervous system, not elsewhere classified
G32.0 – G32.89	Other degenerative disorders of nervous system in diseases classified elsewhere
G93.89	Other specified disorders of brain [Cortical superficial siderosis][ encephalomalacia]
I10	Essential (primary) hypertension
I60.7	Nontraumatic subarachnoid hemorrhage from unspecified intracranial artery, Ruptured (congenital) berry aneurysm.
I67.1	Cerebral aneurysm, nonruptured
R90.89	Other abnormal findings on diagnostic imaging of central nervous system [Cerebral microbleeds]
S06.310A - S06.33AS	Contusion and laceration of cerebrum
Z86.69	Personal history of other diseases of the nervous system and sense organs [seizures]
Z86.73	Personal history of transient ischemic attack (TIA), and cerebral infarction without residual deficits
Numerous Options	Immunological disorders

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Background

U.S. Food and Drug Administration (FDA)-Approved Indications 

• Leqembi is indicated for the treatment of Alzheimer’s disease. Treatment with Leqembi should be initiated in patients with mild cognitive impairment or mild dementia stage of disease, the population in which treatment was initiated in clinical trials.

Lecanemab-irmb, branded as Leqembi (Eisai Inc.), is a humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril) and insoluble forms of amyloid beta (Aβ). In Alzheimer's disease (AD), it is believed that abnormal accumulation of proteins, such as amyloid beta (which form plaques in the extracellular spaces between the neurons of the brain), and tau (which are twisted fibers that form neurofibrillary tangles inside the neurons -- intracellular), leads to loss of synapses and neurons resulting in gross atrophy of the affected areas of the brain, manifesting into progressive memory and cognitive decline (Huang, 2021). Amyloid plaques typically appear earlier in the disease process, whereas tau tangles tend to appear later in the disease. "The Amyloid Theory largely states that if you were able to prevent the accumulation of beta amyloid, or clear existing amyloid, the progress of the cognitive and memory problems associated with Alzheimer’s would be slowed or prevented" (Terry, 2021). Lecanemab is administered as an intravenous infusion aimed to reduce the number of amyloid plaques present in the brain, potentially slowing neurodegeneration and disease progression.

The prescribing information includes a boxed warning for amyloid-related imaging abnormalities (ARIA). Monoclonal antibodies directed against aggregated forms of beta amyloid, including lecanemab-irmb, can cause ARIA, characterized as ARIA with edema (ARIA-E) and ARIA with hemosiderin deposition (ARIA-H). Incidence and timing of ARIA vary among treatments. ARIA usually occurs early in treatment and is usually asymptomatic, although serious and life-threatening events can occur. ARIA can be fatal. Serious intracerebral hemorrhages greater than 1 cm, some of which have been fatal, have been observed in patients treated with this class of medications. Because ARIA-E can cause focal neurologic deficits that can mimic an ischemic stroke, treating clinicians should consider whether such symptoms could be due to ARIA-E before giving thrombolytic therapy to a patient being treated with lecanemab-irmb. 

The label also notes that patients who are apolipoprotein E ε4 (ApoE ε4) homozygotes, which is approximately 15% of patients with Alzheimer’s disease, treated with this class of medications have a higher incidence of ARIA, including symptomatic, serious, and severe radiographic ARIA, compared to heterozygotes and noncarriers. Testing for ApoE ε4 status should be performed prior to initiation of treatment to inform the risk of developing ARIA. Prior to testing, prescribers should discuss with patients the risk of ARIA across genotypes and the implications of genetic testing results. Prescribers should inform patients that if genotype testing is not performed they can still be treated with lecanemab-irmb; however, it cannot be determined if they are ApoE ε4 homozygotes and at higher risk for ARIA. Patients and their healthcare provider should consider treatment benefits and potential risks when deciding to initiate treatment with this medication. 

Enhanced clinical vigilance for ARIA is recommended during the first 14 weeks of treatment with this medication. The risk of ARIA-E and ARIA-H is increased in patients with pretreatment microhemorrhages and/or superficial siderosis. If a patient experiences symptoms suggestive of ARIA, clinical evaluation should be performed, including magnetic resonance imaging (MRI) scanning if indicated. 

The most common adverse reactions (at approximately 10% and higher incidence compared to placebo) include infusion-related reactions, amyloid related imaging abnormality- microhemorrhages, amyloid related imaging abnormality-edema/effusion, and headache.

In January 2023, the FDA, under the Accelerated Approval Pathway, approved Leqembi for treatment of AD. Leqembi treatment is to be initiated in patients with mild cognitive impairment or mild dementia stage of disease, the population in which treatment was initiated in clinical trials. There are no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied. The accelerated approval is based on reduction in amyloid beta plaques observed in patients treated with lecanemab (NCT01767311). Per the FDA, continued approval for this indication may be contingent upon verification of clinical benefit in a confirmatory trial.

Swanson et al (2021) conducted an 18-month, multicenter, double-blind, placebo-controlled Bayesian design, dose finding study (Study 201; ClinicalTrials.gov number NCT01767311) employing response adaptive randomization across placebo and 5 lecanemab arms to assess safety and efficacy in subjects with early AD. Participants were comprised of 2 subgroups: mild cognitive impairment due to AD or mild AD dementia. All subjects were confirmed to be amyloid positive via amyloid positron emission tomography (PET) or cerebrospinal fluid (CSF) Aβ_1–42. Key inclusion criteria included objective impairment in episodic memory (on Wechsler Memory Scale-IV Logical Memory II [WMS-IV LMII]), Mini Mental State Examination (MMSE) score equal to or greater than 22 at screening and baseline (amended to MMSE 22–28 in EU, except Italy), and naïve to or on stable dose (12 weeks) of approved AD medications. Subjects were enrolled who had a Clinical Dementia Rating (CDR) global score of 0.5 or 1.0 and a Memory Box score of 0.5 or greater. The study had a 79-week double-blind, placebo-controlled period, followed by an open-label extension period for up to 260 weeks, which was initiated after a gap period (range 9 to 59 months; mean 24 months) off treatment. To maintain the blind, all subjects received biweekly infusions of either placebo or lecanemab. The study aimed to establish the effective dose 90% (ED90), defined as the simplest dose that achieves 90% or more of the maximum treatment effect. The primary endpoint was change from baseline at 12 months on the Alzheimer’s Disease Composite Score (ADCOMS) for the ED90 dose, which required an 80% probability of 25% or more clinical reduction in decline versus placebo. Key secondary endpoints were change from baseline at 18 months in brain amyloid by PET Standard Uptake Value ratio (SUVr) in an optional sub-study of consenting participants, ADCOMS, Clinical Dementia Rating-Sum-of-Boxes (CDR-SB), Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-Cog14), CSF biomarkers (optional sub-study), and total hippocampal volume using volumetric MRI. In the study, 856 subjects were randomized to receive one of 5 doses (161 of which were randomized to the recommended dosing regimen of 10 mg/kg every two weeks) of lecanemab or placebo (n=247). Of the total number of subjects randomized, 71.4% were ApoE ε4 carriers and 28.6% were ApoE ε4 non-carriers. During the study, the protocol was amended to no longer randomize ApoE ε4 carriers to the 10 mg/kg every two weeks dose arm. ApoE ε4 carriers who had been receiving lecanemab 10 mg/kg every two weeks for 6 months or less were discontinued from study drug. As a result, in the lecanemab 10 mg/kg every two weeks arm, 30.3% of patients were ApoE ε4 carriers and 69.7% were ApoE ε4 non-carriers. The authors found that at 12 months, the 10-mg/kg biweekly ED90 dose showed a 64% probability to be better than placebo by 25% on ADCOMS, which missed the 80% threshold for the primary outcome. At 18 months, 10-mg/kg biweekly lecanemab reduced brain amyloid (−0.306 SUVr units) while showing a drug-placebo difference in favor of active treatment by 27% and 30% on ADCOMS, 56% and 47% on ADAS-Cog14, and 33% and 26% on CDR-SB versus placebo according to Bayesian and frequentist analyses, respectively. CSF biomarkers were supportive of a treatment effect. The authors state that intravenous administration of lecanemab 10 mg/kg every 2 weeks was well-tolerated with 9.9% incidence of ARIA-E at 10 mg/kg biweekly. The authors concluded that Study 201 did not meet the 12-month primary endpoint; however, the prespecified 18-month Bayesian and frquentist analyses demonstrated reduction in brain amyloid accompanied by a consistent reduction of clinical decline across several clinical and biomarker endpoints. The authors note that a phase 3 study (Clarity AD) in early AD is underway.

Swanson and colleagues (2021) acknowledged limitations in Study 201. "Most notably, a small number of symptomatic ARIA-E cases at 10 mg/kg biweekly prompted one Regulatory Authority to request that subsequent ApoE4+ subjects (approximately 70% of the overall study population) not be randomized to the 10 mg/kg biweekly dose. An additional component to the request required that all ApoE4+ subjects on 10 mg/kg biweekly who were on study but who had not yet reached 6 months of treatment be immediately discontinued (N = 25 subjects). Implementation of these actions led to early (initiated between 300 and 350 randomized participants) and significant changes to the study design that resulted in a marked imbalance in the number of ApoE4+ subjects on 10 mg/kg biweekly (30% ApoE4+ subjects). The Bayesian algorithm identified 10 mg/kg biweekly as the ED90 dose despite this imposed design limitation. The constraints in this analysis were specifically associated with the ED90 dose and therefore could have had an impact on the ability to interpret the results. The safety and efficacy of 10 mg/kg biweekly lecanemab is currently being evaluated in an open label extension to this study, and in the phase 3 lecanemab Clarity AD study, where there are no dosing restrictions based on ApoE status in either study."

van Dyck and colleagues (2023) conducted an 18-month, multicenter, double-blind, placebo-controlled, parallel-group, phase 3 trial evaluating lecanemab in persons with early AD. The study (Clarity AD; NCT03887455) includes persons 50 to 90 years of age with mild cognitive impairment or mild dementia due to AD with evidence of amyloid on PET or by CSF testing. Participants were randomly assigned in a 1:1 ratio to receive intravenous lecanemab (10 mg per kilogram of body weight every 2 weeks) or placebo. The primary end point was the change from baseline at 18 months in the score on the Clinical Dementia Rating-Sum of Boxes (CDR-SB; range, 0 to 18, with higher scores indicating greater impairment). Key secondary end points were the change in amyloid burden on PET, the score on the 14-item cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog14; range, 0 to 90; higher scores indicate greater impairment), the Alzheimer's Disease Composite Score (ADCOMS; range, 0 to 1.97; higher scores indicate greater impairment), and the score on the Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment (ADCS-MCI-ADL; range, 0 to 53; lower scores indicate greater impairment). A total of 1795 participants were enrolled, with 898 assigned to receive lecanemab and 897 to receive placebo. The authors found that the mean CDR-SB score at baseline was approximately 3.2 in both groups. The adjusted least-squares mean change from baseline at 18 months was 1.21 with lecanemab and 1.66 with placebo (difference, -0.45; 95% confidence interval [CI], -0.67 to -0.23; p<0.001). In a substudy involving 698 participants, there were greater reductions in brain amyloid burden with lecanemab than with placebo (difference, -59.1 centiloids; 95% CI, -62.6 to -55.6). Other mean differences between the two groups in the change from baseline favoring lecanemab were as follows: for the ADAS-cog14 score, -1.44 (95% CI, -2.27 to -0.61; p<0.001); for the ADCOMS, -0.050 (95% CI, -0.074 to -0.027; p<0.001); and for the ADCS-MCI-ADL score, 2.0 (95% CI, 1.2 to 2.8; p<0.001). Lecanemab resulted in infusion-related reactions in 26.4% of the participants and ARIA-E in 12.6%. The incidence of amyloid related imaging abnormalities-hemosiderin deposition (ARIA-H) was 17.3%. The incidence of ARIA, including symptomatic ARIA, was numerically lower than in similar clinical trials, but differences in the drugs used and in trial design do not allow direct comparisons. ARIA-E generally occurred in the first 3 months, was mild and asymptomatic, did not lead to discontinuation of lecanemab or placebo if mild, and resolved within 4 months. The authors note that the incidences of both overall and symptomatic ARIA-E were highest among ApoE ε4 homozygotes. The authors concluded that lecanemab reduced markers of amyloid in early AD and resulted in moderately less decline on measures of cognition and function than placebo at 18 months but was associated with adverse events. The authors acknowledge study limitations which includes data for only 18 months of treatment. The authors state that longer trials are warranted to determine the efficacy and safety of lecanemab in early AD. Additional trials of lecanemab include a 5-year phase 2 long-term extension trial (NCT01767311) and a 4-year phase 3 long-term extension trial (NCT03887455) in early AD, the 4-year AHEAD 3-45 trial (NCT04468659) in preclinical AD, and the 4-year DIAN-TU (Dominantly Inherited Alzheimer Network Trials Unit) Next Generation trial (NCT05269394) in dominantly inherited AD.

On July 6, 2023, the FDA granted traditional approval for Leqembi for the treatment of Alzheimer's disease based on results from the phase 3 Clarity AD trial, which met its primary and key secondary endpoints showing statistically significant results for use of Leqembi in patients with MCI or mild dementia stage of disease. Leqembi was found to reduce clinical decline on CDR-SB by 27% at 18 months compared to placebo. Additionally, Leqembi slowed decline of activities of daily living by 37% on ADCS MCI-ADL at 18 months. "Leqembi demonstrated clinically meaningful slowing of cognitive and functional decline in a patient group generalizable to U.S. Medicare beneficiaries, which included a mix of racial and ethnic groups, patients with common comorbid conditions, concomitant medications and patients with mild cognitive impairment (MCI) due to AD or mild AD". There are no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied (Biogen, 2023).

The label includes an updated black box warning regarding apolipoprotein (ApoE4) genotype status. Patients treated with Leqembi who are ApoE ε4 homozygotes have a higher incidence of ARIA, including symptomatic and serious ARIA, compared to heterozygotes and noncarriers. Testing for ApoE ε4 status should be performed prior to initiation of treatment to inform the risk of developing ARIA. Prior to testing, prescribers should discuss with patients the risk of ARIA across genotypes and the implications of genetic testing results. The most common adverse reactions (at approximately 10% and higher incidence compared to placebo) include infusion-related reactions, amyloid related imaging abnormality-microhemorrhages, amyloid related imaging abnormality edema/effusion, and headache (Eisai, 2023).

In December 2022, the FDA granted premarket notification for Roche Diagnostics' Elecsys β-Amyloid (1-42) CSF II and Elecsys phospho-tau (181P) CSF. These in vitro electrochemiluminescence immunoassays are indicated for the measurement of the β-amyloid (1-42) (Abeta42) and phospho-tau (181P) (pTau181) protein concentrations in cerebrospinal fluid (CSF) from adult patients aged 55 years and older being evaluated for Alzheimer's disease (AD) and other causes of cognitive impairment to generate a pTau181/Abeta42 ratio value. A negative result, defined as pTau181/Abeta42 ratio value below cut-off or an Abeta42 value above the measuring range, is consistent with a negative amyloid positron emission tomography (PET) scan result. A negative result reduces the likelihood that a patient’s cognitive impairment is due to AD. A positive result, defined as pTau181/Abeta42 ratio value above cut-off, is consistent with a positive amyloid PET scan result. A positive result does not establish a diagnosis of AD or other cognitive disorder. The pTau181/Abeta42 ratio result is used as an adjunct to other clinical diagnostic evaluations. There are limitations for use. The performance of the pTau181/Abeta42 ratio has not been established for predicting development of dementia or other neurologic conditions, and monitoring responses to therapies.

In a systematic review and meta-analysis, Ebell and colleagues (2024) evaluated clinically meaningful benefits and harms of monoclonal antibodies targeting amyloid for the treatment of Alzheimer disease. These investigators carried out a literature search using PubMed, Cochrane CENTRAL, and 5 trial registries, as well as the reference lists of identified studies related to monoclonal antibodies. Randomized controlled trials comparing a monoclonal antibody with placebo at a dose consistent with that used in phase 3 trials or for U.S. FDA approval were included. Studies had to report at least 1 clinically relevant benefit or harm. Data were extracted independently by at least 2 researchers for random effects meta-analysis. Changes in cognitive and functional scales were compared between groups, and each difference was assessed to determine if it met the minimal clinically important difference (MCID), defined as the smallest change in a scale measuring cognition or function that is noticeable by the patient or their caregiver. The investigators identified 87 studies from PubMed and 71 from other sources, of which 16 were duplicates. A total of 142 records were screened and 41 underwent full text review. Exclusions included some studies that used subtherapeutic doses, studied an anti-Tau antibody, or were phase 1 studies. A total of 19 publications with 23,202 total participants that evaluated 8 anti-amyloid antibodies were used for final analysis. Most were 18 to 19 months in duration, and enrolled patients with mild cognitive impairment or with mild or moderate Alzheimer disease. Their analysis revealed small improvements over placebo in the Alzheimer's Disease Assessment Scale (ADAS)-Cog-11 to -14 score (standardized mean difference = -0.07; 95% CI, -0.10 to -0.04), Mini Mental State Examination score (0.32 points; 95% CI, 0.13 to 0.50), and Clinical Dementia Rating-Sum of Boxes scale score (mean difference =-0.18 points; 95% CI, -0.34 to -0.03), and the combined functional scores (standardized mean difference = 0.09; 95% CI, 0.05 to 0.13). None of the changes, including those for lecanemab, aducanumab, and donanemab, exceeded the MCID. Harms included significantly increased risks of amyloid-related imaging abnormalities (ARIA)-edema (relative risk [RR] = 10.29; number needed to harm [NNH] = 9), ARIA-hemorrhage (RR = 1.74; NNH = 13), and symptomatic ARIA-edema (RR = 24.3; NNH = 86). The investigators acknowledged limitations to their analysis. "All studies enrolled participants who underwent positron emission tomography scanning and/or cerebrospinal fluid analyses for amyloid, studies that are not typically done in current routine clinical practice. The included studies reported average changes on standard cognitive and functional scales, but did not report the percentage of participants achieving clinically meaningful differences in cognition or function from baseline. Such data would be more interpretable for clinicians and patients. Finally, studies had different inclusion criteria for severity of disease at baseline, which is a source of potential heterogeneity." The investigators concluded that although monoclonal antibodies targeting amyloid provide small benefits on cognitive and functional scales in patients with Alzheimer dementia, these improvements are far below the MCID for each outcome and are associated with significant harms.

In a narrative review, Park et al (2024) synthesized data from clinical trials, primarily the phase 3 Clarity AD randomized controlled trial, to evaluate lecanemab’s pharmacology, efficacy, and safety in early Alzheimer’s disease. The primary endpoint discussed is the change from baseline in the Clinical Dementia Rating–Sum of Boxes (CDR-SB) at 18 months, where lecanemab 10 mg/kg IV every two weeks resulted in a mean change of 1.21 versus 1.66 with placebo, a statistically significant difference of -0.45 (95% CI, -0.67 to -0.23; P < 0.001). Key secondary endpoints included reductions in brain amyloid burden (mean difference: -59.1 Centiloids), and favorable effects on the ADAS-cog14, ADCOMS, and ADCS-MCI-ADL scores. The most common adverse events were infusion-related reactions (26.4%) and amyloid-related imaging abnormalities (ARIA, 12.6%). The review highlights limitations such as the modest clinical effect size, the need for intravenous administration and frequent MRI monitoring, and concerns about cost and generalizability to broader patient populations. The authors note ongoing studies of alternative dosing and administration routes, but conclude that lecanemab offers moderate slowing of cognitive decline in early Alzheimer’s disease, with a safety profile requiring careful patient selection and monitoring.

In a systematic review and meta-analysis, Abdelazim et al (2024) evaluated the efficacy and safety of lecanemab 10 mg/kg biweekly versus placebo in patients with Alzheimer's disease, synthesizing data from randomized controlled trials. The key efficacy endpoints included changes in cognitive and functional measures such as ADCOMS, CDR-SB, and ADAS-cog14, with lecanemab demonstrating statistically significant reductions in clinical decline compared to placebo, and narrow confidence intervals with no significant heterogeneity across studies. Safety analysis revealed no significant difference in the incidence of treatment-emergent adverse events (TEAEs) between groups, but lecanemab was associated with increased risks of amyloid-related imaging abnormalities—both ARIA-E (edema) and ARIA-H (hemorrhage)—necessitating careful monitoring in clinical practice. Limitations of the analysis include potential publication bias, the relatively short duration of follow-up in available trials, and the need for further data to clarify the long-term clinical significance of the observed cognitive benefits and the risk profile in broader, real-world populations.

The 2024 revised criteria for the diagnosis and staging of Alzheimer's disease, developed by the Alzheimer's Association Workgroup, define Alzheimer's disease as a biological process that begins with the appearance of Alzheimer's disease neuropathologic change (ADNPC), detectable even in asymptomatic individuals. The criteria emphasize the use of early-changing Core 1 biomarkers—such as amyloid positron emission tomography (PET), validated cerebrospinal fluid (CSF) markers, and plasma phosphorylated tau 217—which, when abnormal, are sufficient to establish a diagnosis of Alzheimer's disease and guide clinical decision-making across the disease continuum. Later-changing Core 2 biomarkers, including biofluid and tau PET, provide additional prognostic information and increase diagnostic confidence when abnormal. The framework integrates biological and clinical staging, acknowledging that factors such as co-pathologies, cognitive reserve, and resistance can modify the relationship between clinical symptoms and biological stage, and is intended to bridge research and clinical care by reflecting current scientific understanding, rather than serving as a step-by-step clinical practice guideline or treatment protocol (Jack Jr et al, 2024).

On August 29, 2025, the FDA approved once-weekly subcutaneous maintenance dosage of lecanemab-irmb, branded as Leqembi IQLIK (Eisai Co., Ltd.), for treating patients with MCI or mild dementia stage of disease (collectively referred to as early AD). Leqembi IQLIK is intended for self-administration or may be administered by a caregiver after receiving proper training.

The FDA approval of the subcutaneous (SC) dosing of Leqembi IQLIK is supported by data from the Phase 3 Clarity AD open-label extension trial, which evaluated various SC doses in individuals with early AD. The study demonstrated that transitioning to a weekly 360 mg SC maintenance dose after 18 months of initial intravenous (IV) dosing (10 mg/kg every two weeks) maintained comparable clinical and biomarker benefits without significant injection-related adverse events. Safety data from over 600 patients indicated that systemic reactions were less than 1% with SC dosing, compared to approximately 26% with IV infusions, while mild-to-moderate local reactions occurred in about 11% of patients. Additionally, the rates of amyloid-related imaging abnormalities (ARIA) were similar between the SC and maintenance IV groups. Over 48 months, lecanemab showed a significant reduction in cognitive decline, with a mean change of -1.75 points on the Clinical Dementia Rating-Sum of Boxes (CDR-SB) compared to expected declines in control cohorts. The SC formulation offers patients the convenience of at-home administration, reduces the need for infusion center visits, and may optimize healthcare resources, thereby enhancing the overall treatment pathway for AD.

Leqembi IQLIK is projected to launch in the U.S. on October 6, 2025.

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Appendix

Appendix A: Diagnostic Criteria for Mild Cognitive Impairment (MCI) and Dementia with Mild Functional Impact

• Mild cognitive impairment (MCI) / Clinical Stage 3:
  

  • Cognitive concerns by the patient, knowledgeable informant, or the physician
  • Objective impairment in one or more cognitive domains including memory, executive function, attention, language, or visuospatial skills
  • Generally preserved activities of daily living (ADL) 
  • No dementia
    
    

• Dementia with mild functional impairment / Clinical Stage 4:

  • Cognitive concerns by the patient, knowledgeable informant, or the physician
  • Performance in the impaired/abnormal range on objective cognitive tests
  • Evidence of decline from baseline, documented by the individual’s report or by observer (e.g., study partner) report or by change on longitudinal cognitive testing or neurobehavioral assessments
  • Progressive cognitive and mild functional impairment on instrumental ADL with independence in basic ADL

Source: Albert et al (2011); Jack et al (2024); Rabinovici et al (2025)

Appendix B: Clinical Dementia Rating (CDR) Scale

The CDR is obtained through semi-structured interviews of patients and informants with cognitive functioning rated on a 5-point scale in the following domains: memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care. The score relates to the member’s level of dementia:

• 0 = Normal
• 0.5 = Very Mild Dementia
• 1 = Mild Dementia
• 2 = Moderate Dementia
• 3 = Severe Dementia

Source: Knight Alzheimer Disease Research Center; Morris (1993); O'Bryant et al (2008)

Appendix C: Mini-Mental Status Exam (MMSE)

The MMSE is scored on a 30-point scale, with items that assess orientation (temporal and spatial; 10 points), memory (registration and recall; 6 points), attention/concentration (5 points), language (verbal and written, 8 points), and visuospatial function (1 point). The score relates to the member’s level of dementia:

• 25 - 30 suggests normal cognition
• 20 - 24 suggests mild dementia
• 13 - 20 suggests moderate dementia
• Less than 12 suggests severe dementia

Source: Folstein, Folstein, and McHugh (1975)

Appendix D: Montreal Cognitive Assessment (MoCA)

Per MoCA assessment, average scores for the following ranges are:

• Mild Cognitive Impairment: 19 - 25
• Mild Dementia: 11 - 21
• Normal: 26 and above

Source: MoCA Test Inc, 2023; Nasreddine et al, 2019

Appendix E: ARIA MRI Classification Criteria

Table 3: ARIA MRI Classification Criteria

ARIA Type	Radiographic Severity
	Mild	Moderate	Severe
ARIA-E	FLAIR hyperintensity confined to sulcus and or cortex/subcortical white matter in one location less than 5 cm	FLAIR hyperintensity 5 to 10 cm in single greatest dimension, or more than 1 site of involvement, each measuring less than 10 cm	FLAIR hyperintensity greater than 10 cm with associated gyral swelling and sulcal effacement. One or more separate sites of involvement may be noted.
ARIA-H microhemorrhage	less than or equal to 4 new incident microhemorrhages	5 to 9 new incident microhemorrhages	10 or more new incident microhemorrhages
ARIA-H superficial siderosis	1 focal area of superficial siderosis	2 focal areas of superficial siderosis	greater than 2 focal areas of superficial siderosis

Source: Eisai, 2025

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References