Acumen Pharmaceuticals (NASDAQ:ABOS) said it expects to report top-line results in November from its Phase II ALTITUDE-AD trial of sabirnetug, an investigational antibody designed to target soluble amyloid-beta oligomers in patients with Alzheimer’s disease.
Chief Executive Officer Dan O’Connell said the company views the readout as a significant test of its central scientific hypothesis: that preventing harm from synaptotoxic amyloid-beta oligomers could provide a differentiated approach to treating Alzheimer’s disease. The ALTITUDE-AD study evaluates two doses of sabirnetug against placebo over 18 months and uses the integrated Alzheimer’s Disease Rating Scale, or iADRS, as its primary endpoint.
“We are confident that we are fully evaluating the A-beta oligomer hypothesis with this study,” O’Connell said, describing ALTITUDE-AD as a large, well-powered Phase II trial with clinically meaningful endpoints.
November readout to include clinical, safety and biomarker data
Acumen said its top-line data package is expected to include primary-endpoint results, secondary measures including the Clinical Dementia Rating-Sum of Boxes, or CDR-SB, safety information including adverse events and amyloid-related imaging abnormalities, known as ARIA, as well as fluid and imaging biomarkers.
The study is evaluating intravenous sabirnetug at doses of 35 milligrams per kilogram and 50 milligrams per kilogram every four weeks. O’Connell said the dose selections were informed by exposure, pharmacodynamic findings and modeling from the company’s Phase I study in Alzheimer’s patients.
He said Acumen believes both doses fall within a potentially efficacious range, though the higher dose could potentially produce greater effects on the amyloid PET signal. The company will assess those results when the data are available.
In response to an analyst question about the threshold for proceeding, O’Connell reiterated the company’s guidance that it is seeking “a clear clinical success” of 30% slowing on iADRS after 18 months versus placebo. He said the safety profile, including ARIA rates, infusion reactions and other adverse events, will also be important in determining whether sabirnetug advances.
Acumen anticipates low-double-digit ARIA-E rates overall, potentially consistent across genotypes, as part of a profile that could support moving the candidate into Phase III. O’Connell said the company has designed ALTITUDE-AD as part of a potential registration package, with one confirmatory Phase III trial anticipated after positive Phase II results.
Retention and open-label extension participation exceeded expectations
O’Connell said patient retention in the blinded, primary portion of ALTITUDE-AD exceeded the company’s expectations. More than 95% of eligible participants elected to enroll in the trial’s 12-month open-label extension, according to the company.
However, data from the open-label extension are expected to be generated over a longer period and likely will not be included in the November top-line announcement. Acumen said it expects the extension to produce evidence into 2027.
The company plans to report biomarker findings from the main study, including amyloid PET imaging and fluid-based measures in cerebrospinal fluid and plasma. O’Connell identified p-tau217 as one biomarker the company expects to evaluate as a measure of disease status and potential progression.
During the call, O’Connell also said a successful study could help inform whether the drug’s mechanism supports measuring treatment effects at earlier time points in future studies. He said the theory behind sabirnetug is that early neutralization of toxic amyloid-beta oligomers could potentially lead to disease slowing and other symptomatic benefits, though the company said the ALTITUDE-AD results will be needed to assess that possibility.
Company sees potential roles alongside plaque-clearing therapies
Asked about the evolving Alzheimer’s treatment landscape, O’Connell said Acumen has long supported chronic dosing while patients remain stable in earlier stages of the disease. He said an oligomer-selective antibody such as sabirnetug could be a logical option after plaque clearance, based on the company’s view that soluble aggregates persist and continue to contribute to disease pathology.
Acumen remains focused on the primary ALTITUDE-AD outcome, but O’Connell said the therapeutic rationale for a post-plaque-clearance treatment approach “would make sense” to the company.
He added that key opinion leaders have expressed interest in treatments that could offer a mechanism distinct from plaque-clearing agents. According to O’Connell, physicians and researchers are closely watching the ALTITUDE-AD study because its results could inform the relative role of oligomer-targeting therapies in Alzheimer’s care.
Enhanced brain-delivery program advances toward 2027 IND filing
Acumen also discussed its enhanced brain delivery, or EBD, program, which combines blood-brain barrier-penetrating technology with amyloid-beta oligomer-selective antibodies. The company is developing two candidates ahead of an investigational new drug filing expected in mid-2027.
- ACU301: A bispecific antibody incorporating sabirnetug.
- ACU401: A candidate incorporating ACU234, a novel amyloid-beta-selective antibody with differentiated properties.
O’Connell said data presented at the Alzheimer’s Association International Conference in July showed that tested EBD bispecific antibodies achieved multifold greater brain exposure than unmodified ACU234 after intravenous administration. ACU401 achieved up to 40-fold greater frontal-cortex exposure in non-human primates, he said, along with increased exposure in deep brain regions.
The company said it will use findings from ALTITUDE-AD to further refine dosing and biomarker strategies for its EBD candidates. Acumen has not yet finalized its early-stage clinical-development approach for those programs.
Third-quarter expenses declined as trial-related costs fell
Chief Financial Officer and Chief Business Officer Matt Zuga said Acumen ended the third quarter with approximately $79 million in cash and marketable securities, which the company expects will fund current clinical and operational activities into early 2027.
Research and development expense totaled $21.1 million in the third quarter, declining from the prior-year period primarily because of lower manufacturing, materials and contract research organization costs associated with ALTITUDE-AD. General and administrative expense was $4.7 million, roughly flat year over year.
Acumen reported a loss from operations of $25.8 million and a net loss of $25.4 million for the quarter ended Sept. 30, 2026.
About Acumen Pharmaceuticals (NASDAQ:ABOS)
Acumen Pharmaceuticals, Inc is a clinical-stage biopharmaceutical company focused on developing treatments for Alzheimer’s disease and other neurodegenerative disorders. The company’s research centers on amyloid beta oligomers, toxic protein assemblies that Acumen believes contribute to the development and progression of Alzheimer’s disease.
Acumen’s lead product candidate is sabirnetug, also known as ACU193, an investigational humanized monoclonal antibody designed to selectively target soluble amyloid beta oligomers.
