To the best of our knowledge, this is the first study to apply Lecanemab eligibility criteria – based on both the Clarity-AD trial and real-world recommendations from the American and French AUR - to a real-world cohort of pre-frail and frail individuals with objective cognitive impairment and confirmed brain amyloid pathology. Our findings show that while less than one in five participants from the Cogfrail cohort would have been eligible for inclusion in the Clarity-AD trial, approximately half the cohort would be potentially treatable with Lecanemab according to real-world recommendations. Moreover, while fewer than 10% of frail individuals would have been eligible for inclusion in the Clarity-AD trial, approximately 50% would potentially meet eligibility criteria for treatment based on real-world recommendations. In other words, nearly 80% of frail patients who could be potentially treated in clinical practice would not have been enrolled in the trial population, underscoring a potential gap between clinical trials and real-world practice, with interesting implications for the generalizability of Lecanemab’s efficacy and safety.
Previous studies applicating the phase III Clarity-AD trial to community-dwelling older adults with MCI or early dementia reported an eligibility rate ranging from 1.5% to approximately 30%(14–17). The substantial variability across investigations primarily arises from differences in population selection criteria, making it difficult to compare eligibility rates across studies. For instance, some studies estimated eligibility rates exclusively among amyloid-positive individuals(14), while others initially included amyloid-negative subjects(15–17), only to exclude them later based on Clarity-AD eligibility criteria. A similar issue arose with AD dementia severity, as some studies initially included individuals with more advanced dementia (CDR > 1) (14, 16), only to exclude them later based on the trial's eligibility requirements. Considering that we estimated eligibility rates only among amyloid-positive individuals and that our cohort was preselected for the Cogfrail study - requiring participants to have a CDR score of 0.5 or 1 - the eligibility rate observed in our sample may have been expected to be higher than that observed in previous studies. However, applying Clarity-AD criteria this was not the case, most likely due to the characteristics of our population (pre-frail and frail individuals), which may have influenced the eligibility rate.
The discrepancy in eligibility rates between the Clarity-AD trial and real-world recommendations primarily reflects differences in inclusion criteria, which allowed for the potential inclusion of approximately one-fourth of participants who would have been excluded from the trial based solely on age, BMI, or MMSE scores. Moreover, the application of clinical history and medication-related exclusion criteria appears to rely more on clinical judgment within the context of real-world recommendations, except for anticoagulation. This may allow for the inclusion - following appropriate management - of individuals who would have been excluded from the Clarity-AD trial due to factors such as uncontrolled diabetes or recent initiation of antidepressant therapy. In both the trial and the real-world recommendations, nearly one third of participants would have ultimately been excluded due to MRI contraindications, making this the leading cause of ineligibility for Lecanemab treatment in our sample. Although ApoE genotype data were missing for eight participants, our findings suggest that the ε4/ε4 genotype would have had minimal impact on eligibility decisions among pre-frail and frail older adults. The American and French recommendations demonstrated substantial concordance, with discrepancies in eligibility observed in only four cases.
Our findings suggest that frail individuals could represent a substantial proportion of the patients potentially eligible for treatment in real-life clinical practice. This proportion may be even higher when applying drug label recommendations instead of the AUR (~ 60% of our population eligible under the EMA label criteria). However, although Clarity-AD did not assess frailty status, the relatively low proportion of frail individuals meeting the trial’s inclusion criteria in our cohort indirectly suggest that frailty may have been underrepresented in the trial, raising concerns about the generalizability of the outcomes in this population. From a safety perspective, frailty is well recognized as a risk factor for increased susceptibility to adverse drug reactions (ADRs)(21). Given that frailty reflects a state of heightened vulnerability to stressors, the response to pharmacological treatments may be different in this population(21). Consequently, frail individuals may face a higher risk of experiencing ADRs, including infusion-related reactions, ARIAs, headaches, and falls. From an efficacy perspective, as highlighted by Wallace et al.(22), frail people may present a weaker relationship between AD pathology and Alzheimer’s dementia. In other words, frailty may diminish an individual's ability to tolerate AD pathology, potentially leading to cognitive decline even at low amyloid burdens that might have remained asymptomatic in non-frail individuals. It is indeed possible that without a more comprehensive and personalized approach, amyloid reduction alone may not yield meaningful clinical benefits. Frailty has long been used as a reason for treatment exclusion(23), but a more effective strategy should provide access to personalized treatment according to frailty status. This approach could involve combining pharmacological therapy (i.e., Lecanemab) with tailored interventions designed to enhance resilience, potentially increasing tolerability to residual brain pathology and reducing ADRs. Prehabilitation, a rehabilitation program designed to optimize function and improve tolerability to intensive medical interventions (i.e. surgery or chemotherapy), has become the standard of care in several medical and surgical fields(24). In this context, a multidomain intervention aimed at improving frailty before and alongside anti-amyloid treatment may enhance treatment tolerability and potentially increase individuals' ability to cope with the residual AD-related brain pathology. Future research is needed to assess whether combining anti-amyloid treatment with multidomain interventions yields better outcomes than anti-amyloid therapy alone, particularly in frail individuals.
Limitations:
The study has several strengths. The Cogfrail study includes neuroimaging and a comprehensive geriatric assessment for all participants, thereby enabling an accurate application of the eligibility criteria. Additionally, patients were recruited from outpatient visits at Frailty or Memory Clinics as part of their routine assessments, making the sample representative of real-world populations. The study also has some limitations. First, it is a secondary analysis of data originally collected for the Cogfrail study, whose primary objective differed from the current research question. Second, eligibility was determined through retrospective chart review. Third, although the sample is highly representative of a real-world population with objectively measured cognitive impairment, inevitably, there is also an overlap between Lecanemab and Cogfrail eligibility criteria, which may have contributed to overestimate the proportion of eligible individuals.