Population-Based Study Reveals Low Eligibility Rates for Alzheimer Therapy Lecanemab

Silke Kern, MD, PhD

Using a sample of participants from the Gothenburg H70 Birth Cohort Study (H70-BCS), findings revealed that 6.2% of the 70-year-olds included were eligible for lecanemab (Leqembi; Eisai), a recently approved novel treatment for early-stage Alzheimer disease (AD). Assuming a similar proportion, and a similar ratio of individuals with AD without complicating factors in other parts of Europe and the United States, this estimate extrapolates to an approximation that around 5.9 million Europeans and 2.2 million US residents could be eligible.¹

Lecanemab, approved by the FDA in 2023, is an antibody directed against aggregated forms of amyloid-ß. The therapy is indicated for the treatment of AD with mild cognitive impairment or mild dementia, with patients needing a positive PET scan to prove their diagnosis. In the analysis, published in Neurology, investigators took 290 participants from the cohort study who had clinical data, cerebrospinal fluid-amyloid-ß, and brain MRI analysis.

In the study, all citizens of Gothenberg born on specific birth dates in 1944 were invited, with no exclusion criteria. Led by senior investigator Silke Kern, MD, PhD, head of the department of psychiatry and neurochemistry at the University of Gothenberg, 30 of the 290 patients were amyloid-positive and had MCI or mild dementia. Of these, 12 presented with 1 or several items requiring special consideration before treatment. Taken together, 18 of the 290 participants (6.2%) were eligible for lecanemab treatment without any factor indicating risk of adverse events (AEs).

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Based on the proportion of individuals in the H70-BCS eligible for lecanemab, without factors requiring special consideration, an estimate of magnitude was extrapolated in Europe and the United States. Investigators based this analysis on several assumptions, including that the sample with complete data in this study is representative of the full H70-BCS, participants in the H70-BCS were representative of 70-year-olds in Sweden, Swedish residents are equally affected by AD as other residents in Europe and the United States, and that the proportion of individuals who are eligible is similar in 70-year-olds and older individuals because factors requiring special considerations regarding risk of AEs increase with age to a similar magnitude as the prevalence of AD.

Using public data from “Our world in data,” the European Union currently has 95 million citizens between 70 and 89 years and the United States has 35 million. Based on this, investigators estimated that the total number of individuals eligible for lecanemab treatment in the EU and US would account for approximately 5.9 million and 2.2 million individuals, respectively.

"The presented estimates of eligibility in EU and the United States are crude and should not be used for future policy making or direction of funds for future care,” Kern et al wrote. “However, our study contributes to data based on the current FDA-approved prescribing information. Furthermore, we analyzed Aβ42 in CSF, which can be influenced by other diseases in the CNS, and may differ slightly from using PET."

The sample used in the study was further compared with the 913 individuals from the full birth cohort to assess representativity of the sample. Overall, the sample had an overrepresentation of men (52% vs 45%) while there was no difference in other characteristics, including Clinical Dementia Rating and apolipoprotein ε4 homozygosity. In addition, the authors noted that, "Owing to a contraindication of some anticoagulant medications to perform LP, individuals with anticoagulant treatment or a medical history of cerebral stroke were overrepresented among those with missing data."

REFERENCE
1. Dittrich A, Westman E, Shams S, et al. Proportion of community-dwelling individuals older than 70 years eligible for lecanemab inititation: the Gothenburg H70 Birth Cohort Study. Neurology. 2024;102(9). doi:10.1212/WNL.0000000000209402