The highest clinical trial failure rate for any disease in modern medicine: How both amyloid- and non-amyloid-targeting therapies failed to alter disease course in Alzheimer's disease

Abstract

Background: Alzheimer's disease drug development has produced a 99.6 percent failure rate for disease-modifying compounds (244 compounds tested 2002–2012, one regulatory approval; Cummings et al., 2014; Cummings, 2018)—the most sustained and costly therapeutic failure in the history of modern medicine. The field's standard explanation is that the biology is intractable. The present analysis offers a different and more instructive diagnosis: the failure was not primarily scientific. It was institutional.

Objective: To characterize the structural and institutional forces that sustained investment in repeatedly ineffective mechanisms of action across 567 Phase 2 and Phase 3 Alzheimer's trials from 2010 to 2026, and to determine whether peer-reviewed alternative pathogenic frameworks were available at the time each major Go/No Go decision was made.

Methods: Trials were identified from ClinicalTrials.gov using the following criteria: primary diagnosis of Alzheimer's disease or mild cognitive impairment attributed to Alzheimer's disease; Phase 2 or Phase 3; status of terminated or completed; primary completion date between January 1, 2010 and May 4, 2026. After exclusion of 70 trials not classifiable by mechanism of action, a final analytic dataset of 497 trials was classified by primary mechanism using the Common Alzheimer's Disease Research Ontology (CADRO). A temporal alignment analysis was conducted for the 12 largest trials by enrollment (N ≥ 1,300), mapping each trial's initiation date against the publication dates of peer-reviewed alternative mechanistic frameworks available at the time of trial launch.

Results: Amyloid-targeting approaches accounted for approximately 31 percent of the 497 classified trials, nearly all of which failed to demonstrate clinical efficacy. Among the 12 largest trials, 11 targeted amyloid pathology and 10 were terminated for futility or lack of efficacy. All 12 trials were initiated after the publication in high-impact journals of peer-reviewed alternative frameworks, including the TREM2 neuroinflammation pathway, the antimicrobial protection hypothesis, the periodontitis-associated bacterial pathogenesis hypothesis, and the GLP-1 metabolic pathways. The post-2022 period revealed that genuinely novel non-amyloid mechanisms—TREM2 agonism, GLP-1 receptor stimulation, filamin A modulation, and progranulin/sortilin restoration—also failed to produce clinical benefit at scale despite confirmed target engagement. Three establishment forces are identified as operative causes: regulatory path dependency, institutional entrenchment within grant and editorial review panels, and shareholder-driven sunk-cost pressures.

Conclusion: The 567-trial record constitutes a structural verdict on a model of drug development that was never designed to solve a problem of this complexity. The uniformity of negative results across all mechanism categories—amyloid, tau, neuroinflammation, metabolic, and synaptic—points toward deeper problems of disease definition, intervention timing, and endpoint validity that institutional and financial pressures have prevented the field from confronting. The Dominantly Inherited Alzheimer Network (DIAN) biomarker data demonstrates that pathology precedes symptoms by 15–25 years; the 2025 DIAN Trials Unit (DIAN-TU) extension provides the first evidence that treatment before symptom onset may delay dementia. Prevention trials in asymptomatic at-risk populations represent the only strategy the accumulated trial record has not yet refuted.