Acumen's sabirnetug fails Phase 2 Alzheimer's trial, company halts development

Acumen Pharmaceuticals announced on October 30, 2026 that its Phase 2 ALTITUDE-AD trial of sabirnetug (ACU193) in early Alzheimer's disease did not meet its primary goal. The trial failed to show a difference from placebo in cognitive and functional decline, as measured by the Integrated Alzheimer's Disease Rating Scale (iADRS) at 18 months, at either the 35 mg/kg or 50 mg/kg dose.¹ Key secondary measures, including the Clinical Dementia Rating-Sum of Boxes (CDR-SB), also failed to reach statistical significance, with no meaningful separation between either dose arm and placebo.¹

On safety, sabirnetug was generally well tolerated, with amyloid-related imaging abnormalities-edema (ARIA-E) seen in about 10% of treated participants.¹ On a biological marker, PET-based measures of amyloid plaque showed statistically significant reductions at both doses by week 36 and week 76.¹

Acumen said it expects more data from the trial in the coming weeks, including fluid biomarker and additional imaging results, but does not anticipate that data will change the trial's efficacy conclusions.¹ Based on the initial results, the company plans to stop developing sabirnetug, including the trial's open-label extension, and will evaluate strategic options including its Enhanced Brain Delivery (EBD) program, while taking cash conservation steps.¹

ALTITUDE-AD began in 2024 as a Phase 2, multi-center, randomized, double-blind, placebo-controlled study of sabirnetug infusions given every four weeks, enrolling 542 participants with mild cognitive impairment or mild dementia due to Alzheimer's disease across sites in the United States, Canada, the European Union and the United Kingdom.¹ Acumen is also developing a subcutaneous version of sabirnetug using Halozyme's ENHANZE technology, and is collaborating with JCR Pharmaceuticals on a separate EBD therapy platform for Alzheimer's disease.¹