Acumen halts Alzheimer’s drug development after 35 and 50 mg/kg doses fail in Phase 2 trial
Key Facts
Acumen Pharmaceuticals announced on October 30 that its Phase 2 trial of experimental drug sabirnetug failed to meet its primary endpoint after 18 months at either the 35 or 50 mg/kg dose compared with placebo. The company said it plans to halt development of the drug, including the ALTITUDE-AD open-label extension, and assess its strategic options. The result marked a shift for the company, which had expected days earlier to announce topline results in November 2026. The company also linked its next steps to preserving cash and assessing its alternative brain-delivery program. ABOS shares closed at $2.29 on October 29, while coverage published on October 30 showed a 3.78% decline.
The result extended beyond the primary measure: Acumen said key secondary endpoints, including the CDR-SB measure of dementia severity, did not achieve statistical significance. It added that the results showed no meaningful difference between the treatment and placebo groups. The effect observed on amyloid plaques therefore did not translate into demonstrated improvement in the cognitive and functional outcomes measured by the trial. This gap between a biomarker and patient outcomes is the most notable finding in the topline data. The company did not describe the decision as a judgment on the clinical viability of development, but announced its plan to halt the program based on the results.
By contrast, PET imaging showed a statistically significant reduction in amyloid plaques at both doses at weeks 36 and 76. The company said sabirnetug was generally well tolerated, with amyloid-related imaging abnormalities with edema, or ARIA-E, observed in about 10% of participants who received treatment. However, this effect on plaques did not coincide with meeting the primary or secondary clinical efficacy goals. The drug targets soluble amyloid beta aggregates and had received Fast Track designation from the U.S. Food and Drug Administration for the treatment of early Alzheimer’s disease. The study results thus came despite its reliance on a specific targeting mechanism and its regulatory designation.
ALTITUDE-AD included about 542 participants and was designed as a multicenter, randomized, double-blind, placebo-controlled trial. Participants received an infusion once every four weeks, while follow-up for the primary endpoint lasted 18 months. Acumen plans to discontinue the trial’s open-label extension alongside halting sabirnetug development. It also said it would assess its strategic options, including its Enhanced Brain Delivery program for delivering drugs to the brain. The alternative program had targeted filing an IND application in mid-2027, according to company expectations before the ALTITUDE-AD results were announced.
Acumen had $78.6 million in cash, cash equivalents and marketable securities on September 30, 2026, compared with $110.2 million on June 30. The company had expected that liquidity to fund its current clinical and operating activities through early 2027. It now says it will take steps to preserve cash while reviewing its strategic options. The halt to its lead program comes as the company seeks to determine the role its brain-delivery program could play in its next plan. The previous target for filing an IND application for that program was mid-2027.
The company expects to receive and analyze additional ALTITUDE-AD data over the coming weeks, but does not expect those data to change its efficacy conclusions. Acumen announced on October 26 that it was targeting a November release of topline results, before releasing them on October 30. The next steps will therefore focus on analyzing the additional data, preserving cash and assessing options for the alternative program. The company did not set a deadline for its strategic decision in its results announcement. Its stated plan to analyze the data also did not change its current conclusion on efficacy results.