Eligibility for Anti-Amyloid Therapies in Patients With Biomarker-Confirmed Atypical Alzheimer Disease Phenotypes

Clinical trials of anti-amyloid therapies (AATs) for Alzheimer disease (AD) primarily enrolled patients with mildly symptomatic, amnestic predominant presentations. The applicability of eligibility criteria to atypical AD phenotypes, including posterior cortical atrophy (PCA), logopenic variant primary progressive aphasia (lvPPA), dysexecutive AD (dAD), and corticobasal syndrome because of AD (CBS-AD), is unknown.

We conducted a retrospective eligibility analysis of patients with atypical AD evaluated at Mayo Clinic. Theoretical eligibility for AAT was assessed at initial clinical evaluation by applying inclusion and exclusion criteria from landmark clinical trials (Study to Confirm Safety and Efficacy of Lecanemab in Participants With Early Alzheimer's Disease [CLARITY-AD] and the Study of LY3002813 (Donanemab) in Participants With Early Symptomatic Alzheimer's Disease [TRAILBLAZER-ALZ2]) and appropriate use criteria for lecanemab and donanemab. Eligibility percentages and reasons for exclusion were compared across phenotypes.

The cohort included 184 patients (61.4% female) with biomarker-confirmed atypical AD: PCA (n = 98, 53.3%), lvPPA (n = 42, 22.8%), dAD (n = 37, 20.1%), and CBS-AD (n = 7, 3.8%). Age at onset (p = 0.039) and presentation (p < 0.001) differed, with patients with lvPPA oldest (median age at onset, presentation: 63.1, 66.9 years) and patients with dAD youngest (onset, presentation: 55.1, 57.3). Functional impairment differed by phenotype (p = 0.005), with lvPPA more often diagnosed at the mild cognitive impairment/very mild stage (Clinical Dementia Rating [CDR] 0.5; 71.4%), whereas PCA and dAD more frequently presented with mild dementia, although time from symptom onset to diagnosis did not differ (p = 0.634). Mini-Mental State Examination (MMSE) scores differed (p = 0.036), with lower scores in PCA and lvPPA (median 21 and 21, respectively) compared with CBS-AD (median 27). Depending on the eligibility framework applied, 70%-85% of patients would not meet treatment criteria. Bedside cognitive thresholds were the primary drivers of ineligibility (50%-67% of exclusions), despite most patients having early symptomatic disease (global CDR 0.5-1; 82%). Imaging-based exclusions (22%-27%) and severity thresholds (moderate or severe dementia, 19%-23%) were also frequent. Reasons for ineligibility were similar across phenotypes.

Most patients with atypical AD would not meet eligibility criteria for AAT, typically because of MMSE-based exclusion rather than measures of cognitive function. Eligibility rates are broadly similar across atypical phenotypes. These findings highlight the need for phenotype-sensitive staging and patient selection for treatment in atypical AD.