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To have maximal benefit, Alzheimer's disease-modifying treatments might need to be started before the onset of clinical symptoms. Mutations of the PSEN1 gene are inherited as fully penetrant, autosomal-dominant traits, which almost always result in the clinical onset of Alzheimer's disease before the age of 65 years. We aimed to evaluate the efficacy, including possible delayed emergence of cognitive impairment, and safety of crenezumab, an anti-amyloid monoclonal antibody, in cognitively unimpaired carriers of the PSEN1 mutation at high imminent risk of developing symptoms due to Alzheimer's disease. This 5-8-year common-close, double-blind, placebo-controlled, single-centre trial screened kindred members aged 30-60 years from the main health-care site in Medellín, Colombia. Participants who were cognitively unimpaired and carried the PSEN1 autosomal-dominant mutation were randomly assigned 1:1 to receive placebo or subcutaneous crenezumab (investigators and participants were masked to treatment allocation), with an initial 300 mg dose every 2 weeks that increased to 720 mg every 2 weeks, and a later optional increase to 60 mg/kg intravenously every 4 weeks. Randomisation was stratified by age, education, APOE ɛ4 carrier status, and baseline Clinical Dementia Rating. Mutation non-carriers received placebo and were included in a 1:2 ratio of non-carriers to carriers to maintain genotype masking and include a genetic kindred control. Dual primary outcomes were the annualised rates of change in the Alzheimer's Prevention Initiative (API) preclinical autosomal-dominant Alzheimer's disease (ADAD) composite test total score and Free and Cued Selective Reminding Test-Cueing Index (FCSRT-CI) assessed in randomised participants who received at least one dose of the study drug, according to treatment assignment. Primary endpoints were assessed with a random coefficient regression model with a missing-at-random assumption adjusting for randomisation factors. Safety endpoints for mutation carriers were assessed in randomised participants who received at least one dose of the study drug. This trial is registered with ClinicalTrials.gov (NCT01998841) and is completed. 619 Colombian API registrants were prescreened, 315 were assessed for eligibility, and 252 were enrolled (crenezumab-carrier, n=85; placebo-carrier, n=84; placebo-non-carrier, n=83; 160 [63%] women and 92 [37%] men) between Dec 20, 2013, and Feb 27, 2017. 237 (94%) completed the trial, with final data collection on March 22, 2022. The annualised rate of change in the API ADAD composite was -1·10 (SE 0·29) in the crenezumab group and -1·43 (0·29) in the placebo group (between-group difference 0·33 [95% CI -0·48 to 1·13]; p=0·43). The annualised rate of change in FCSRT-CI was -0·03 (0·00) in the crenezumab group and -0·04 (0·00) in the placebo group (between-group difference 0·01 [0·00 to 0·02]; p=0·16). All participants had at least one adverse event; serious adverse events occurred in 23 (27%) of 84 in the crenezumab group and 21 (25%) of 84 in the placebo group. No fatalities occurred. Crenezumab therapy administered for 5-8 years did not result in significant benefits on our primary clinical outcomes in cognitively unimpaired participants predisposed to developing ADAD dementia; secondary and exploratory outcomes also showed no significant effect on removal of amyloid plaques or other clinical or biomarker outcomes. Together with the results of other anti-amyloid β trials, robust fibrillar amyloid removal appears necessary for clinical efficacy in people with elevated brain amyloid. This study will further inform the biomarker, cognitive, and clinical trajectory of preclinical ADAD, the risk of clinical progression in amyloid-positive and amyloid-negative mutation carriers, and the size and design of future secondary and primary prevention trials. US National Institute on Aging (NIA), Banner Alzheimer's Institute, Genentech, F Hoffmann-La Roche.

Background This study evaluates a tailored genetic counseling and testing (GTC) protocol for families at risk of Autosomal Dominant Alzheimer ´s Disease (ADAD) in Latin America, focusing on the essential cultural and regional adaptations. Several factors may influence the decision of whether family members decide to learn genetic status. Although the main drivers influencing the decisions to seek genetic testing have been widely studied in High‐Income Counties (HIC), these questions remain relatively unknown in Low and Middle‐Income countries (LMICs) such as those in Latin America (LatAm). Method The primary aim of this study was to investigate the psychosocial impact of genetic testing in asymptomatic individuals from families with ADAD. We conducted a non randomized, controlled trial among ADAD families in Colombia and Argentina. The primary outcome included change from baseline in depression and general anxiety in the test group relative to the control group. Participants were categorized based on their decision to learn their genetic status, with further comparisons between mutation‐positive versus mutation‐negative individuals within those informed. Psychological impacts were measuring using validated scales for depression and anxiety in the group relative to the control group. Result Of the 122 eligible participants, 97 completed the GTC protocol; 87 opted to learn their genetic status. There were no clinically significant differences in psychological distress between those who learned their status and those who did not, nor between mutation‐positive and mutation‐negative individuals. Mutation‐positive carriers who learned their genetic status experienced a statistically significant increase in depression scores but remained below the cut‐off point considered indicative of clinically significant depression. Conclusion Our primary finding is showed no clinically meaningful differences in distress‐related outcomes between individuals learning their genetic status relative to those who didn’t. Our findings confirm that genetic testing is well‐tolerated when using a protocol that provides screening, education, counseling, and follow‐up sessions. In addition, we provide preliminary insights into the psychological impact associated with learning one's genetic status in familial AD, contributing significantly to the field of medical genetics in the region.

This study evaluates a tailored genetic counseling and testing (GTC) protocol for families at risk of Autosomal Dominant Alzheimer ´s Disease (ADAD) in Latin America, focusing on the essential cultural and regional adaptations. Several factors may influence the decision of whether family members decide to learn genetic status. Although the main drivers influencing the decisions to seek genetic testing have been widely studied in High-Income Counties (HIC), these questions remain relatively unknown in Low and Middle-Income countries (LMICs) such as those in Latin America (LatAm). The primary aim of this study was to investigate the psychosocial impact of genetic testing in asymptomatic individuals from families with ADAD. We conducted a non randomized, controlled trial among ADAD families in Colombia and Argentina. The primary outcome included change from baseline in depression and general anxiety in the test group relative to the control group. Participants were categorized based on their decision to learn their genetic status, with further comparisons between mutation-positive versus mutation-negative individuals within those informed. Psychological impacts were measuring using validated scales for depression and anxiety in the group relative to the control group. Of the 122 eligible participants, 97 completed the GTC protocol; 87 opted to learn their genetic status. There were no clinically significant differences in psychological distress between those who learned their status and those who did not, nor between mutation-positive and mutation-negative individuals. Mutation-positive carriers who learned their genetic status experienced a statistically significant increase in depression scores but remained below the cut-off point considered indicative of clinically significant depression. Our primary finding is showed no clinically meaningful differences in distress-related outcomes between individuals learning their genetic status relative to those who didn't. Our findings confirm that genetic testing is well-tolerated when using a protocol that provides screening, education, counseling, and follow-up sessions. In addition, we provide preliminary insights into the psychological impact associated with learning one's genetic status in familial AD, contributing significantly to the field of medical genetics in the region.

To have maximal benefit, Alzheimer's disease-modifying treatments might need to be started before the onset of clinical symptoms. Mutations of the PSEN1 gene are inherited as fully penetrant, autosomal-dominant traits, which almost always result in the clinical onset of Alzheimer's disease before the age of 65 years. We aimed to evaluate the efficacy, including possible delayed emergence of cognitive impairment, and safety of crenezumab, an anti-amyloid monoclonal antibody, in cognitively unimpaired carriers of the PSEN1Glu280Ala mutation at high imminent risk of developing symptoms due to Alzheimer's disease. This 5–8-year common-close, double-blind, placebo-controlled, single-centre trial screened kindred members aged 30–60 years from the main health-care site in Medellín, Colombia. Participants who were cognitively unimpaired and carried the PSEN1Glu280Ala autosomal-dominant mutation were randomly assigned 1:1 to receive placebo or subcutaneous crenezumab (investigators and participants were masked to treatment allocation), with an initial 300 mg dose every 2 weeks that increased to 720 mg every 2 weeks, and a later optional increase to 60 mg/kg intravenously every 4 weeks. Randomisation was stratified by age, education, APOE ɛ4 carrier status, and baseline Clinical Dementia Rating. Mutation non-carriers received placebo and were included in a 1:2 ratio of non-carriers to carriers to maintain genotype masking and include a genetic kindred control. Dual primary outcomes were the annualised rates of change in the Alzheimer's Prevention Initiative (API) preclinical autosomal-dominant Alzheimer's disease (ADAD) composite test total score and Free and Cued Selective Reminding Test–Cueing Index (FCSRT–CI) assessed in randomised participants who received at least one dose of the study drug, according to treatment assignment. Primary endpoints were assessed with a random coefficient regression model with a missing-at-random assumption adjusting for randomisation factors. Safety endpoints for mutation carriers were assessed in randomised participants who received at least one dose of the study drug. This trial is registered with ClinicalTrials.gov (NCT01998841) and is completed. 619 Colombian API registrants were prescreened, 315 were assessed for eligibility, and 252 were enrolled (crenezumab–carrier, n=85; placebo–carrier, n=84; placebo–non-carrier, n=83; 160 [63%] women and 92 [37%] men) between Dec 20, 2013, and Feb 27, 2017. 237 (94%) completed the trial, with final data collection on March 22, 2022. The annualised rate of change in the API ADAD composite was –1·10 (SE 0·29) in the crenezumab group and –1·43 (0·29) in the placebo group (between-group difference 0·33 [95% CI –0·48 to 1·13]; p=0·43). The annualised rate of change in FCSRT–CI was –0·03 (0·00) in the crenezumab group and –0·04 (0·00) in the placebo group (between-group difference 0·01 [0·00 to 0·02]; p=0·16). All participants had at least one adverse event; serious adverse events occurred in 23 (27%) of 84 in the crenezumab group and 21 (25%) of 84 in the placebo group. No fatalities occurred. Crenezumab therapy administered for 5–8 years did not result in significant benefits on our primary clinical outcomes in cognitively unimpaired participants predisposed to developing ADAD dementia; secondary and exploratory outcomes also showed no significant effect on removal of amyloid plaques or other clinical or biomarker outcomes. Together with the results of other anti-amyloid β trials, robust fibrillar amyloid removal appears necessary for clinical efficacy in people with elevated brain amyloid. This study will further inform the biomarker, cognitive, and clinical trajectory of preclinical ADAD, the risk of clinical progression in amyloid-positive and amyloid-negative mutation carriers, and the size and design of future secondary and primary prevention trials. US National Institute on Aging (NIA), Banner Alzheimer's Institute, Genentech, F Hoffmann-La Roche.

Background We previously estimated the age of amyloid plaque onset at 28.2 years using florbetapir PET measurements of cerebral amyloid deposition in a cross‐sectional study of a convenience sample of PSEN1 E280A carriers and non‐carriers, ages 20‐56, recruited from the world's largest autosomal dominant Alzheimer’s disease (ADAD) cohort. Here we capitalized on longitudinal data from a different sample than used previously, to estimate the age of amyloid onset (EOA) in carriers who were cognitively unimpaired at baseline and examine differences associated with apolipoprotein ε4 (APOE4) status and between men and women. Method We analyzed baseline, 2‐year, and 5‐year florbetapir PET scans from 161 initially cognitively unimpairedPSEN1 E280A carriers (ages 30–56) enrolled in the Alzheimer’s Prevention Initiative (API) ADAD Colombia Trial of crenezumab vs placebo, in which crenezumab did not lower brain amyloid (NCT01998841). We included PSEN1 E280A carriers with at least 1 amyloid‐positive (A+) PET scan, using cortical‐to‐pontine standard‐uptake value ratios converted to centiloids (CL). Out of the 169 PSEN1 E280A carriers in the trial, 12 were A‐ and 149 were A+ at baseline, we excluded 1 PSEN1 E280A carrier who did not have A+ longitudinal data and 7 who did not have A+ scans at baseline or follow‐up. The Sample Iterative Local Approximation (SILA) model was applied to estimate EOA using a 20 CL threshold for positivity. We estimated amyloid chronicity and compared EOAs, adjusted for baseline age, between A+ male (n =68) and female (n =98) PSEN1 E280A carriers and between A+ PSEN1 E280A APOE4‐carriers (n =35) and non‐carriers (n =126). Result Median EOA was 26.1 years (SD ±7.89, range 1‐54) and estimates were normally distributed. PSEN1 E280A females had a mean EOA of 25.8 years which was not significantly different than the estimates in males (M=27.8 years). PSEN1 E280A APOE4 carriers had an EOA about 3 years younger (M=24.1) than APOE4 non‐carriers (M=27.3, p =0.03). Conclusion This study illustrates the ability to use longitudinal biomarker data to characterize the onset of biomarker changes and impact of putative disease modifiers like APOE4 in ADAD mutation carriers.

We previously estimated the age of amyloid plaque onset at 28.2 years using florbetapir PET measurements of cerebral amyloid deposition in a cross-sectional study of a convenience sample of PSEN1 E280A carriers and non-carriers, ages 20-56, recruited from the world's largest autosomal dominant Alzheimer's disease (ADAD) cohort. Here we capitalized on longitudinal data from a different sample than used previously, to estimate the age of amyloid onset (EOA) in carriers who were cognitively unimpaired at baseline and examine differences associated with apolipoprotein ε4 (APOE4) status and between men and women. We analyzed baseline, 2-year, and 5-year florbetapir PET scans from 161 initially cognitively unimpairedPSEN1 E280A carriers (ages 30-56) enrolled in the Alzheimer's Prevention Initiative (API) ADAD Colombia Trial of crenezumab vs placebo, in which crenezumab did not lower brain amyloid (NCT01998841). We included PSEN1 E280A carriers with at least 1 amyloid-positive (A+) PET scan, using cortical-to-pontine standard-uptake value ratios converted to centiloids (CL). Out of the 169 PSEN1 E280A carriers in the trial, 12 were A- and 149 were A+ at baseline, we excluded 1 PSEN1 E280A carrier who did not have A+ longitudinal data and 7 who did not have A+ scans at baseline or follow-up. The Sample Iterative Local Approximation (SILA) model was applied to estimate EOA using a 20 CL threshold for positivity. We estimated amyloid chronicity and compared EOAs, adjusted for baseline age, between A+ male (n =68) and female (n =98) PSEN1 E280A carriers and between A+ PSEN1 E280A APOE4-carriers (n =35) and non-carriers (n =126). Median EOA was 26.1 years (SD ±7.89, range 1-54) and estimates were normally distributed. PSEN1 E280A females had a mean EOA of 25.8 years which was not significantly different than the estimates in males (M=27.8 years). PSEN1 E280A APOE4 carriers had an EOA about 3 years younger (M=24.1) than APOE4 non-carriers (M=27.3, p =0.03). This study illustrates the ability to use longitudinal biomarker data to characterize the onset of biomarker changes and impact of putative disease modifiers like APOE4 in ADAD mutation carriers.

Background Genetic testing for individuals with dominantly inherited Alzheimer’s disease (DIAD) is now of greater relevance due to the existence of therapeutic trials available to this population. However, the impact and main drivers influencing the decision to seek genetic testing are relatively unknown in Latin America (LatAm). Here we present results from a regional genetic counseling and testing protocol implemented in LatAm. Method Our aim was to investigate the psychosocial impact of genetic testing in asymptomatic individuals from families with DIAD. A non‐randomized, controlled, prospective observational trial was conducted. Asymptomatic, first‐degree relatives of patients with DIAD from families with a presenilin 1, pathogenic variant (p.I416T or p.M146L) were interviewed before and after genetic testing. Group allocation was done according to participants’ choice (non‐randomized). Participants who received their genetic status (GS) were allocated to the test group, while those who opted out were allocated to the observational group. The primary outcome included change from baseline in depression, general anxiety, and health‐related anxiety in the test group relative to the observational group, using linear mixed effects models and chi‐squared tests. Result Forty‐five participants from Colombia and Argentina were invited and enrolled in the study. Thirty‐six individuals completed the genetic counseling sessions, and 25/36 (69.4%) learned their GS. Compared to families in Colombia, participants from Argentina were more likely to seek counseling and learn their GS (8/23, 34.9% vs, 17/20, 85.0%, respectively). Following genetic counseling, we found no significant differences between the group that learned their GS and those who did not learn their GS in anxiety (mean = 13.5, SD = 3.2 vs. 15.1, SD = 2.5, p = 0.2) or depression (mean = 5.4, SD = 2.3 vs. mean = 8.0, SD = 6.5, p = 0.6) scores. For both groups, anxiety and depression scores remained below cutoffs for clinical concern and without significant changes relative to baseline value levels. Conclusion Our pilot study shows that a structured genetic counseling and testing protocol for individuals at‐risk of DIAD is safe. We found relevant cross‐country differences in willingness to learn genetic status, which may reflect differences in religion, educational level, and urban vs rural areas, among others. Future studies should include larger cohorts and expand to other countries in LatAm.

Autosomal dominant Alzheimer's disease (ADAD) represents a small but impactful subset of Alzheimer's cases. Asymptomatic individuals at genetic risk face substantial personal and family implications when considering predictive testing for known familial variants. Genetic counseling and testing (GCT) frameworks remain limited in Latin America (LatAm). Recommendations for GCT in LatAm were developed through an iterative, multidisciplinary consensus process. Evidence inputs included a structured literature review, site‐level recommendations from participating LatAm centers, and a qualitative synthesis of focus groups with experienced investigators. The resulting model includes pre‐test evaluation, sample collection, result disclosure, and structured follow‐up. Core elements comprise mental health assessment, psychoeducation, exploration of expectations and decision‐making needs, guided disclosure with emotional support, and a suggested 3‐month post‐disclosure reassessment using validated psychological measures. Our framework provides structured guidance for the safe and ethical delivery of GCT for ADAD through a multidisciplinary, culturally informed, and patient‐centered approach in LatAm. Highlights We examined the available recommendations for genetic counseling and testing (GCT) for individuals at risk for autosomal dominant Alzheimer's disease (ADAD). Unique challenges in predictive genetic testing for ADAD demand a person‐centered and culturally sensitive approach. Here we propose the first recommendations for GCT adapted to Latin American families. The recommendations are supported by a group of experts in ADAD from the PRograma de Asesoramiento Genético para América Latina (PRAGA) working group. Future research will enrich these guidelines and broaden the scope to other forms of dementia.

INTRODUCTION This study involved evaluating a tailored genetic counseling and testing (GCT) protocol for families at risk of autosomal dominant Alzheimer's disease (ADAD) in Latin America (LatAm), focusing on essential cultural and regional adaptations. METHODS We conducted a non‐randomized controlled trial among ADAD families in Colombia and Argentina. Participants were categorized based on their decision to learn their genetic status (GS), with further comparisons between mutation‐positive versus mutation‐negative participants who learned their status. Psychological impacts were measured using validated scales for anxiety and depression. RESULTS Of the 122 eligible participants, 97 completed the GCT protocol, and 87 opted to learn their GS. There were no clinically significant differences in psychological distress between those who learned their status and those who did not, nor between mutation‐positive and mutation‐negative individuals. DISCUSSION The GCT protocol effectively managed psychological impacts in ADAD families and was positively received, demonstrating the importance of culturally adapted GCT protocols. Highlights We examined the adaptation and efficacy of a GCT protocol in LatAm for families at risk of ADAD. The GCT protocol mitigated psychological distress among at‐risk ADAD families. The study confirms the protocol's cultural appropriateness and psychological safety. Future studies should explore the long‐term psychological and public health impacts of GCT and use of GCT for treatment options.