Aducanumab, gantenerumab, BAN2401, and ALZ-801-the first wave of amyloid-targeting drugs for Alzheimer's disease with potential for near term approval

Martin Tolar, Susan Abushakra, John A Hey, Anton Porsteinsson, Marwan Sabbagh, Martin Tolar, Susan Abushakra, John A Hey, Anton Porsteinsson, Marwan Sabbagh

Abstract

The body of evidence suggesting a causative, initiating role of beta amyloid (Aβ) in the pathogenesis of Alzheimer's disease (AD) is substantial. Yet, only a few anti-amyloid agents have shown meaningful efficacy in clinical trials. We evaluated the unifying characteristics of anti-amyloid agents with positive clinical or biomarker effects in long-duration trials and analyzed how pharmacological characteristics determine their clinical product profiles. Four agents with the potential for near term approval fulfill these criteria: the injectable antibodies, aducanumab, gantenerumab, and BAN2401, and a small molecule oral agent, ALZ-801. Aducanumab and BAN2401 showed significant efficacy on both clinical and biomarker outcomes; gantenerumab showed significant biomarker effects, with no clinical efficacy reported to date; and ALZ-801 showed significant clinical effects in the high-risk population of patients homozygous for the ε4 allele of apolipoprotein E gene (APOE4) and a dose-dependent preservation of hippocampal volume. We explored how the pharmacological properties of these agents, namely selectivity for Aβ oligomers, plasma half-life, brain penetration, and time to peak brain exposure, determine their clinical profiles. A crucial characteristic shared by these agents is their ability to engage neurotoxic soluble Aβ oligomers, albeit to various degrees. Aducanumab and gantenerumab partially target oligomers, while mostly clearing insoluble amyloid plaques; BAN2401 preferentially targets soluble protofibrils (large oligomers) over plaques; and ALZ-801 blocks the formation of oligomers without binding to plaques. The degree of selectivity for Aβ oligomers and brain exposure drive the magnitude and onset of clinical efficacy, while the clearance of plaques is associated with vasogenic brain edema. Only the highest doses of aducanumab and BAN2401 show modest efficacy, and higher dosing is limited by increased risk of vasogenic edema, especially in APOE4 carriers. These limitations can be avoided, and efficacy improved by small molecule agents that selectively inhibit the formation or block the toxicity of Aβ oligomers without clearing amyloid plaques. The most advanced selective anti-oligomer agent is ALZ-801, an optimized oral prodrug of tramiprosate, which demonstrated efficacy in homozygous APOE4/4 AD subjects. ALZ-801 selectively and fully inhibits the formation of Aβ42 oligomers at the clinical dose, without evidence of vasogenic edema, and will be evaluated in a phase 3 trial in homozygous APOE4/4 patients with early AD. In addition to clinical measures, the phase 3 trial will include cerebrospinal fluid, plasma, and imaging biomarkers to gain further insights into the role of soluble Aβ oligomers in the pathogenesis of AD and their impact on disease progression.

Keywords: ALZ-801; APOE4 genotype; Aducanumab; Alzheimer’s disease; Anti-amyloid antibodies; Anti-oligomer agents; BAN2401; Beta amyloid oligomers; Gantenerumab.

Conflict of interest statement

Dr. Martin Tolar serves as the Founder, President, and Chief Executive Officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc.

Dr. Susan Abushakra serves as the Chief Medical Officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc.

Dr. John A. Hey serves as the Chief Scientific Officer of Alzheon, Inc. and holds stock and stock options of Alzheon, Inc.

Dr. Anton Porsteinsson receives research support from the National Institutes of Health and U.S. Department of Defense. He also receives grants from AstraZeneca, Avanir, Biogen, Biohaven, Eisai, Eli Lilly, Genentech/Roche, Janssen, Novartis, Merck, and Toyama. He receives personal fees from Acadia Pharmaceuticals, Avanir, BioXcel, Eisai, Functional Neuromodulation, Grifols, Lundbeck, Merck, Neurim Pharmaceuticals, Pfizer, Tetra Discovery Partners, and Toyama.

Dr. Marwan Sabbagh receives research support from the NIH and the Keep Memory Alive Foundation. He has consulting agreements with Allergan, Biogen, Bracket, Cortexyme, Grifols, Sanofi, Neurotrope, and Roche-Genentech. He has ownership interest in Brain Health Inc., Versanum Inc., Neurotrope Inc., and uMethod Health.

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