US-based clinical-stage biopharmaceutical company Acumen Pharmaceuticals, Inc. (NASDAQ: ABOS), which is developing a therapeutic targeting soluble amyloid beta oligomers for Alzheimer's disease, said on Monday that the first participant has been dosed in the open-label extension of its Phase 2 ALTITUDE-AD trial of sabirnetug.

The extension allows all individuals who completed the 18-month placebo-controlled phase to receive sabirnetug at 35 mg/kg intravenously every four weeks for 52 weeks.

Study assessments and safety monitoring will mirror those used in the original blinded portion of the trial.

Chief Medical Officer Eric Siemers said the extension reinforces the company's commitment to participants and is expected to generate long-term safety and efficacy data.

Sabirnetug is described as the first humanised monoclonal antibody to show selective engagement of soluble amyloid beta oligomers in Alzheimer's patients, and previously demonstrated a favourable safety profile and biomarker improvements in the Phase 1 INTERCEPT-AD trial.

Acumen plans to report topline data from ALTITUDE-AD in late 2026.