Alzheimer's disease and peptides — what the trial record actually supports

Why this dossier exists

Alzheimer's disease is the most-studied neurodegenerative dementia and the indication where the peptide field's clinical-trial record is most uniformly disappointing on prespecified primary endpoints. The 2024-to-2026 standard of care is set by the FDA-approved anti-amyloid antibodies — lecanemab (Leqembi), granted full approval in July 2023, and donanemab (Kisunla), approved July 2 2024 — layered on top of the older symptomatic options: the cholinesterase inhibitors donepezil, rivastigmine and galantamine, and the NMDA-receptor antagonist memantine. The anti-amyloid antibodies produce statistically significant slowing of clinical decline on regulatory-grade endpoints, with the trade-off of ARIA (amyloid-related imaging abnormalities), particularly in ApoE ε4 carriers. None of the peptides surveyed here are currently competitive with that benchmark on primary outcome.

What brings peptides into the Alzheimer's conversation in 2026 is not a comparable efficacy claim but three converging developments. The first is the GLP-1 receptor agonist class: liraglutide produced a primary-negative / secondaries-positive Phase 2b (Edison P et al., Nat Med 2026, 32:353–361) and semaglutide produced a primary-negative Phase 3 pair (Novo Nordisk topline release, 24 November 2025). The second is Cerebrolysin, with the largest randomized-controlled-trial body of any product in this corpus and a Cochrane synthesis that pushes against the manufacturer-aligned meta-analytic case. The third is Dihexa and its clinical-development descendant fosgonimeton, whose September 2024 Phase 2/3 LIFT-AD failure (Athira Pharma release, 3 September 2024) terminated the most-developed HGF/MET modulator program in Alzheimer's disease while the academic-research lineage remains under research-integrity pressure (JPET retraction landscape 2025).

This dossier walks each peptide against the actual Alzheimer's literature, separates direct interventional evidence from mechanism extrapolation, and frames where the peptide field sits relative to the current standard of care. The honest one-line read is that the peptide section of the Alzheimer's literature is an archive of interesting failures, contested signals, and mechanism-extrapolation candidates without clinical evidence — not a parallel pharmacopeia competing with the anti-amyloid antibodies. The failed-peptide-trials archive carries the cross-indication framing for how primary-endpoint failures end commercial development; this page applies the same frame inside one indication.