Generalizability of trial criteria on amyloid-lowering therapy against Alzheimer’s disease to individuals with mild cognitive impairment or early Alzheimer’s disease in the general population

On august 14th 2023, we searched the literature for published phase 3 trials of monoclonal antibodies against β-amyloid that met their primary outcome for reducing cognitive and functional decline. Trials included were EMERGE (the high-dose arm of aducanumab), CLARITY-AD (lecanemab), and TRAILBLAZER-ALZ2 (donanemab). Details of included trials are presented in Supplementary Table 1. Trial inclusion and exclusion criteria were obtained from ClinicalTrials.gov and the original trial publications [3‐5]. In case of discrepancy between ClinicalTrials.gov and the published report, we selected criteria from the latter.

The Rotterdam Study is an ongoing population-based cohort study investigating determinants and occurrence of disease in persons aged 40 years and older. The study started in 1990 and now comprises 17,931 individuals living in the Ommoord suburb of Rotterdam, the Netherlands. The design of the Rotterdam Study has been described in detail previously [18]. In brief, participants are invited for interview and extensive in-person examination at a dedicated research centre every 3–6 years. Routine examinations as part of the Rotterdam Study protocol include standardised questionnaires (e.g., social support, mental health, medication use), cognitive assessment, cardiovascular exams (e.g., blood pressure measurement, electrocardiogram and cardiac ultrasound), psychiatric assessment, venepuncture, and genotyping. From 2005 onward, brain MRI became part of the core study protocol of the Rotterdam Study. The fourth examination cycle of the study (2002–2005) included 6,052 participants and the fifth cycle (2009–2013) included 7,162 participants (Supplementary Fig. 1). For the current study, we included all 968 participants who were diagnosed with MCI (n = 779) or early dementia due to clinical manifestation of AD (n = 189)(Supplementary Fig. 1). To ensure that the study population aligned with the severity criteria of MCI or dementia used in clinical trials, we applied the MMSE-based inclusion criteria for each drug. Based on these criteria 751 participants met the inclusion criteria for aducanumab (MMSE score ≥ 24), 832 for lecanemab (MMSE score ≥ 22), and 762 for donanemab (MMSE score 22–28)(Supplementary Fig. 1). Participants with dementia had to have a dementia diagnosis within 1 year from their study centre visit. From 2005 onwards MRI of the brain was implemented into the core protocol of the Rotterdam Study. In total, 255/454 participants with MCI or early dementia due to AD from the fifth examination round had brain MRI scan available. Based on the MMSE criteria for each trial, 221 participants with brain MRI were included for aducanumab, 239 for lecanemab, and 209 for donanemab.

The Rotterdam Study has been approved by the Medical Ethics Committee of the Erasmus Medical Centre and by the Ministry of Health, Welfare and Sport of the Netherlands, implementing the Population Studies Act for the Rotterdam Study. All participants provided written informed consent for participation in the study, including permission to obtain information from their treating physicians.

Participants were screened for dementia at baseline and every 3–6 years during follow-up examinations using the Mini-Mental State Examination (MMSE) and the Geriatric Mental Schedule (GMS) organic level. Those with a MMSE score of < 26 or a GMS organic level score of > 0 were further examined using the Cambridge Examination for Mental Disorders of the Elderly. Additionally, participants were continuously under surveillance for incident dementia through the electronic linkage between the study database and medical records from general practitioners and the Regional Institute of Outpatients Mental Health Care. The general practitioner functions as a gatekeeper within the Dutch healthcare system, receiving written information of any medical specialists’ consultations of their patients. The final diagnosis of dementia and its most common subtypes was made by a consensus panel led by a neurologist based on the standard criteria for all-cause dementia (DSM-III-R) and clinical Alzheimer’s disease (NINCDS-ADRDA). Follow-up for dementia was completed until January 1, 2020.

Criteria for MCI were based on the Petersen criteria, and included the presence of subjective cognitive complaints and objective cognitive impairment, in the absence of dementia [19]. A detailed description of our MCI assessment has been published previously [20]. Subjective cognitive complaints were evaluated by interview, including questions on memory and everyday functioning. We assessed objective cognitive impairment using a cognitive test battery comprising the letter-digit substitution task, Stroop test, verbal fluency test (animal categories), and 15-word verbal learning test based on Rey’s recall of words [21]. Compound scores were constructed for various cognitive domains, including memory function, information-processing speed, and executive function [21, 22]. We classified participants from the Rotterdam Study as objectively cognitively impaired if in any of the cognitive domains, the compound score was at least 1.5 standard deviation lower than expected based on age and education adjusted means, derived from the study population.

For each of the trial inclusion and exclusion criteria, we defined an operationalization in the Rotterdam Study. This was done through consensus discussion between two authors (JJC and FJW). A detailed description of the eligibility criteria for each of the three trials, and their operationalization, is provided in Supplementary Tables 2, 3 and 4. For example, history of cardiovascular disease was based on a combination in-person assessment and continuous linkage with medical records for various comorbidities, use of medication was assessed based on pharmacy dispensary data (ATC-codes), and we had in-person questionnaires for social support and screening for anxiety and depression.

Participants underwent scanning on a 1.5-T MRI scanner (GE Healthcare) using a multisequence protocol consisting of T1-weighted, proton density-weighted, fluid-attenuated inversion recovery, and T2-weighted sequences. For brain volumetry, T1-weighted (voxel size 0.49 × 0.49 × 1.6 mm³), proton density–weighted (voxel size 0.6 × 0.98 × 1.6 mm³), and the fluid-attenuated inversion recovery (FLAIR) (voxel size 0.78 × 1.12 × 2.5 mm³) scans were used for automated segmentation of brain tissues, including white matter hyperintensities [23, 24]. In short, a k-nearest neighbor tissue classification algorithm was implemented for quantification of white matter hyperintensities (WMH) [24]. All segmentations were visually inspected, and manually corrected if needed. Severe WMH were defined as a volume of 16.1 milliliter or more, corresponding to a Fazekas score of 3 [25, 26]. All scans were appraised by trained research physicians for the presence of cerebral microbleeds (i.e., small round to ovoid hypointense areas on T2*-weighted images), lacunes (i.e., focal cavitating lesions ≥ 3 and < 15 mm), and cortical infarcts [27]. These ratings were done blinded to clinical data. Furthermore, abnormalities including superficial siderosis, intracranial aneurysms, meningioma, suspected gliomas, cavernous angioma, arachnoid cysts, arteriovenous malformations and dural fistulas were rated by research physicians, and subsequently evaluated by a consultant neuroradiologist.

To assess amyloid positivity, we used a prediction model based on age and APOE ε4 allele count [28]. This model was developed within the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s trial population (A4 Study), and previously showed high discriminative ability to differentiate people with and without brain amyloid as measured by ¹⁸F-florbetaben PET in the Rotterdam Study population (area under the curve: 0.84 [0.79–0.88]) [28].

Missing data, most notably for social support (17.9%), Parkinson’s disease (due to incomplete assessment of the Unified Parkinson Disease Rating Scale, 7.0%) and anxiety disorder (9.1%), were imputed using 5-fold multiple imputations (“mice” package in R). Details of all missing and imputed variables are described in supplementary Table 7.

For each trial, we determined the number of participants who met the eligibility criteria, both overall and per criterion separately. We compared the subset of trial eligible individuals to all individuals with MCI and early AD dementia in the population on several key demographics and participant characteristics, including, age, sex, educational attainment, MMSE, APOE ε4 carrier status, MCI or dementia status, cardiovascular disease and antithrombotic medication use. We repeated all analyses in the subsample (n = 255) with brain MRI.

Finally, among all individuals with MCI in the primary analyses, we determined 5-year progression to dementia stratified by trial eligibility, by computing hazard ratios (HR) using Cox proportional hazard models.

All analyses were performed in R (version 4.2.1). This study is reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines [29].

The funding sources that contributed to the Rotterdam Study or to authors had no role in study design, data collection, data analysis, data interpretation, writing of the report, and in the decision to submit the paper for publication.

Overall, 968 participants were diagnosed with MCI or early dementia (mean age 75.1 years, 55.2% women), of whom 779 (80.5%) had MCI and 189 (19.5%) clinical AD dementia. Of these, trial-specific entry scores on the MMSE were met by 751 (77.6%) participants for aducanumab (MMSE ≥ 24), 856 (88.4%) for lecanemab (MMSE ≥ 22) and 762 (78.7%) for donanemab (MMSE 22–28). Mean (± SD) age of MMSE-eligible participants was similar across trials, varying from 74.0 (± 8.0) years for aducanumab, to 74.5 (± 8.1) years for lecanemab and 75.3 (± 8.1) years for donanemab. Little over half of participants were women for all three trials (51.6–55.6%).

Trial eligibility criteria for EMERGE (aducanumab), CLARITY-AD (lecanemab), and TRAILBLAZER-ALZ2 (donanemab) are listed in supplementary Tables 2, 3 and 4. Overall, TRAILBLAZER-ALZ2 listed the fewest exclusion criteria. EMERGE was the only trial to exclude persons using platelet inhibiting or anticoagulant medication. CLARITY-AD only included patients with objective impairment in episodic memory, whereas the other two trials did not specify the affected cognitive domain among their inclusion criteria. All trials excluded patients with severe small vessel disease on brain MRI (i.e., severe white matter hyperintensities or > 4 microbleeds). EMERGE and CLARITY-AD additionally excluded patients with lacunes or cortical infarct. CLARITY-AD further excluded individuals with intracranial aneurysms, meningioma, cavernous angioma, and arachnoid cysts. A potentially eligible participant has to go through eight different modalities, including cognitive testing, assessment of prior medical history and comedication, BMI measurement, venepuncture, blood pressure measurement, electrocardiogram, brain MRI scan and amyloid-PET scan or lumbar puncture, as well as have an informant/care partner present for the duration of the study.

Around two-thirds of participants met at least one clinical exclusion criterion, somewhat higher for aducanumab (76.3%; 95% CI 73.3–79.3) and lecanemab (75.8%; 73.0-78.7) than for donanemab (59.8%; 56.4–63.3) (Fig. 1, Supplementary Table 5). Compared to all individuals with MCI and early AD dementia in the Rotterdam Study, eligible participants were similar with respect to age, sex, educational attainment, APOE ε4 carrier status (Table 1). MMSE scores at diagnosis were also similar between groups, although eligible participants were slightly more often at the MCI stage rather than having early dementia. Those eligible for donanemab had more cardiovascular disease (18.3%) compared to those eligible for donanemab (16.4%) and aducanumab (10.1%).

Overall, exclusion criteria related to cardiovascular comorbidity had the largest effect on trial eligibility, but its impact differed between trials (Table 1; Fig. 1). For aducanumab, 264/751 (35.2%) participants were excluded because of cardiovascular disease, and 234/751 (31.2%, mostly overlapping) due to use of anticoagulant medication. Cardiovascular disease amounted to 10.7% exclusion of participants for lecanemab and 9.7% for donanemab. Neurological comorbidity and lack of social support were common reasons for ineligibility across trials, affecting 13.2 to 15.6% of potential participants. In trials of lecanemab and donanemab, 16% of people were ineligible based on indication of presence of mental health disorders, due chiefly to positive screening for depression or anxiety disorder. Psychotropic or immunological medication use frequently led to exclusions for aducanumab (20.4%), while for lecanemab only 0.8% met trial-specific exclusions for immunological medication, and donanemab had no such exclusions.

Figure 2 shows the overlap between the different exclusion criteria within participants. Around one third of exclusion criteria across trials occurred in isolation (34% aducanumab, 41% lecanemab, 38% donanemab), as illustrated by the single, unconnected dots in Fig. 2. Two thirds of participants who were ineligible due to cardiovascular disease also met one or multiple other exclusion criteria, similar across trials (Fig. 2). A notable exception is the presence of non-amnestic MCI (in the absence of memory impairment), which was a common exclusion criterion for lecanemab (391/856, 45.2%), and occurred in isolation in over half of participants meeting this criterion (202/391; 51.7%) (Fig. 2).

Amyloid status was predicted negative in around 40% of all participants with MCI and early clinical AD dementia, similar across trials (aducanumab 42.3%, lecanemab 40.4%, donanemab 37.9%). When adding amyloid negativity to the aforementioned clinical eligibility criteria, the percentage of persons who were ineligible increased from 76.3 to 88.4% for aducanumab, from 75.8 to 86.0% for lecanemab, and from 62.3 to 76.4% for donanemab. Conversely, among all age and MMSE eligible Rotterdam Study participants with positive predicted amyloid status, application of clinical exclusion criteria left 73.8% of participants ineligible for aducanumab, 78.2% for lecanemab, and 49.5% ineligible for donanemab (Fig. 3 and Supplementary Table 6).

Of all 968 included participants, 255 had an available brain MRI scan close to MCI/early AD diagnosis (mean interval: 2.3 years). The most common imaging abnormalities were of presumed vascular nature, with severe white matter hyperintensities in 24.6%, cortical infarcts in 10.6%, ≥ 2 lacunes in 7.5%, and > 4 microbleeds in 3.1% of participants. Around one third of participants would be ineligible for trial participation on the basis of imaging criteria alone, which was similar across trials (Fig. 4).

Eligibility based on clinical criteria was similar in the MRI subsample compared to the overall sample. Compared to the entire sample, participants who were eligible based on clinical and MRI criteria were slightly younger, less educated and more often carrier of the APOE ε4 allele (Table 2). A combination of all clinical criteria, MRI criteria, and predicted amyloid negativity resulted in trial ineligibility of 91.1% (95% CI, 88.9–93.0) for aducanumab, 91.6% (90.1–93.8) for lecanemab and 85.2% (82.5–87.6) for donanemab.

During 5-year follow-up, progression to dementia was observed in 91 Rotterdam Study participants with MCI. Participants with MCI who were ineligible based on clinical criteria tended to have higher risk of progressing to dementia than eligible participants for lecanemab (HR: 1.64, 95% CI: 0.92–2.91), aducanumab (HR: 1.17, 95% CI: 0.65–2.12) and only marginally for donanemab (HR: 1.03, 95% CI: 0.67–1.59).