The Alzheimer's disease therapeutic landscape is evolving, with a growing number of Phase III trials investigating novel targets beyond the traditional focus on amyloid plaques and tau tangles. While anti-amyloid antibodies like Eisai and Biogen’s Leqembi and Eli Lilly’s Kisunla have been approved to slow cognitive decline, their limited efficacy and potential side effects have spurred the development of alternative approaches. These emerging therapies aim to address the complex biology of Alzheimer's disease through diverse mechanisms, potentially paving the way for more effective combination treatments.
Diversifying Therapeutic Targets
According to a recent paper by neuroscientist Jeffrey Cummings, there are currently 32 Alzheimer’s therapeutics in 48 Phase III trials. While six of these target amyloid-β and one targets tau, the majority aim to modulate neuroprotection, growth factors, neurotransmitters, neurogenesis, inflammation, and proteinopathies. Rebecca Edelmayer, vice president of scientific engagement for the Alzheimer’s Association, emphasized the increasing understanding of the disease's complexity, stating, "We're moving to a point where we have better understanding of the disease and what contributes to its symptomology, so those biological underpinnings become targets."
Current Anti-Amyloid Therapies: Benefits and Limitations
Leqembi and Kisunla represent significant advancements as disease-modifying treatments for Alzheimer’s. Leqembi reduced clinical decline by 27% as measured by the Clinical Dementia Rating Sum of Boxes (CDR-SB), while Kisunla reduced clinical decline by 29%. However, these drugs are associated with amyloid-related imaging abnormalities (ARIA), indicating potential brain bleeds or swelling, as well as increases in lateral ventricular volume and loss of whole brain volume. Andrew Tsai, senior vice president of equity research for Jefferies, noted, "There’s debate about whether the two already approved therapeutics are that compelling, so the bar is low."
Novel Phase III Candidates
Several promising candidates in Phase III trials are exploring alternative mechanisms of action:
Athira's Fosgonimeton
Athira Pharma's fosgonimeton is a small-molecule therapeutic administered via daily injection at home. Although a Phase II/III trial involving 315 patients with mild-to-moderate Alzheimer’s disease did not meet its primary endpoints, pre-specified subgroups showed stabilization or improvement in cognition and function. The drug enhances signaling by neurotrophic hepatocyte growth factor (HGF) and has shown promise in preclinical models by reducing inflammation, improving mitochondrial and synaptic function, and reducing amyloid toxicity and p-tau aggregation.
Anavex's ANAVEX 2-73 (Blarcamesine)
Anavex Life Sciences Corp. is developing blarcamesine, an oral, once-daily therapeutic that targets neuronal homeostasis through SIGMAR1 activation and autophagy. In a Phase IIb/III trial, blarcamesine slowed clinical progression of Alzheimer’s by 38.5% at 48 weeks compared to placebo. Notably, the trial showed no associated neuroimaging adverse events, and routine MRI monitoring is not expected. The company anticipates submitting a regulatory package to the European Medicines Agency by the end of the year.
Novo Nordisk's Semaglutide
Novo Nordisk is evaluating semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, in patients with early Alzheimer’s. Completion of the Phase III study is expected in October 2026. Early studies suggest that semaglutide reduces neuroinflammation and may improve vascularization, addressing key pathological features of the disease.
Other Approaches
Neurim Pharmaceuticals is investigating piromelatine, which aims to improve cognition and function by enhancing sleep quality through activation of melatonin and serotonin receptor agonists. Cassava Sciences is developing simufilam, which seeks to restore brain shape and function by stabilizing filamin A (FLNA). However, Cassava's conduct around simufilam has spurred an investigation by the U.S. Department of Justice.
The Future of Alzheimer's Treatment: Combination Therapies and Lifestyle Interventions
Given the heterogeneity of Alzheimer’s disease, experts believe that combination therapies targeting multiple mechanisms may be necessary for effective treatment. Tsai suggested, "There may be a case for teaming up and using certain therapeutics in combination." Edelmayer added that treatment may require a combination of powerful, FDA-approved therapies in conjunction with brain-healthy lifestyles.
