Acumen Pharmaceuticals (NASDAQ:ABOS) outlined progress across its lead Alzheimer’s disease program and an emerging “enhanced brain delivery” (EBD) platform during its fourth-quarter and full-year 2025 update, while management reiterated expectations for a key Phase 2 readout later in 2026 and provided details on cash runway and a recent financing.
ALTITUDE-AD remains on track for late-2026 readout
Chief Executive Officer Daniel O’Connell said 2025 was a “year of execution and expansion,” highlighting clinical progress for sabirnetug in the Phase 2 ALTITUDE-AD study. The trial is designed to test Acumen’s hypothesis that synaptotoxic amyloid beta (Aβ) oligomers play a pivotal role in Alzheimer’s disease. O’Connell described ALTITUDE-AD as a “well-powered” Phase 2 study evaluating sabirnetug, a monoclonal antibody intended to be highly selective for Aβ oligomers.
On the Q&A, President and Chief Development Officer Jim Doherty and Chief Medical Officer Eric Siemers said patient retention and rollover into the OLE have been “in line” with other major Alzheimer’s trials, though they emphasized the study remains blinded and that they are cautious about drawing conclusions from retention metrics. Siemers added that the study has “run remarkably smoothly,” noting the protocol has not required dosing alterations to date.
Phase 1 biomarker data cited as supportive
O’Connell pointed to imaging and fluid biomarker findings from the Phase 1b INTERCEPT-AD study as a reason for optimism ahead of the ALTITUDE-AD readout. He said that after three doses at the three-month time point, sabirnetug showed positive effects on cerebrospinal fluid (CSF) measures including phospho-tau-181 and neurogranin, which he said are gaining acceptance as diagnostic and clinical markers.
During Q&A, Siemers also discussed plaque imaging observations from Phase 1, stating that at the highest two doses (60 mg/kg and 25 mg/kg every two weeks), sabirnetug produced plaque reduction at three months that was “about the same amount” as lecanemab showed over a similar period. However, he stressed the company does not yet know whether plaque reduction will continue over 18 months or plateau, and noted that because sabirnetug targets oligomers rather than plaque, plaque reduction is “not necessarily needed” for the program’s mechanism.
Regarding the open-label extension, Siemers said OLEs typically measure the same endpoints as the parent study but “less frequently” to reduce patient burden. He said the OLE will allow assessment of longer-term outcomes for those originally on active drug and will also provide data for the roughly one-third of participants who initially received placebo once they transition to active treatment.
EBD program: preclinical brain exposure gains and mid-2027 IND target
Acumen’s second major focus was its EBD collaboration with JCR Pharmaceuticals, which combines Acumen’s Aβ oligomer-targeting antibody “cargo” with JCR’s transferrin receptor-based blood-brain barrier carrier technology. O’Connell described the strategy as “supercharging” antibodies to increase brain penetration and distribution, potentially reduce safety risks, and enable subcutaneous dosing. He also said the approach could be suitable for future evaluation in preclinical or presymptomatic Alzheimer’s populations, although that is not part of the company’s immediate clinical plans.
Doherty provided additional detail on the screening approach used to develop EBD candidates, citing evaluation of transferrin receptor affinity, architecture (including single-chain/VHH formats), valency, stability, and whether oligomer selectivity is maintained after attachment of the carrier. He said a non-human primate study showed EBD constructs achieving 14- to 40-fold higher brain levels versus a native antibody control at 24 hours post-dose.
On safety-related observations, Doherty said hematology data in non-human primates suggested “potential for anemia,” but he also reported no observed changes in red blood cell count, hematocrit, hemoglobin, or reticulocyte counts at 24 hours after subcutaneous dosing. He added that stability was favorable and supportive of subcutaneous administration with low-volume devices.
In response to analyst questions about variability in the 14x–40x exposure range, Doherty said the summary reflects measures across multiple brain regions and multiple candidates, and that variability was more between candidates than between regions for a given candidate. He also said several candidates met the company’s target profile, giving flexibility in selecting an IND candidate. The company is targeting an IND filing in mid-2027.
When asked about how EBD could improve upon sabirnetug’s existing oligomer selectivity, Doherty emphasized that the benefit is not only higher brain exposure but also potentially broader distribution because transferrin receptors are located on capillaries throughout the brain, which could influence where antibodies enter brain tissue relative to non-carrier antibodies.
Siemers added that JCR’s technology has been used in a Japan-approved therapy (IZCARGO) and said JCR observed little anemia in its clinical experience, which he suggested may relate to the specific transferrin receptor epitope being targeted. He noted Acumen’s 24-hour primate findings were consistent with that pattern.
Financial results and recent private placement
Chief Financial Officer Matt Zuga said Acumen ended 2025 with $116.9 million in cash and marketable securities, which management expects will fund current clinical and operational activities into early 2027. Full-year 2025 R&D expense was $104.9 million, rising from the prior year mainly due to increased manufacturing and materials for ALTITUDE-AD as well as personnel costs and EBD research expenses. G&A expense was $18.9 million, decreasing primarily due to reductions in recruiting, corporate insurance, and consulting costs.
The company reported a loss from operations and a net loss of $121.3 million for 2025.
Zuga also highlighted a financing completed after year-end. On March 16, 2026, Acumen closed a private placement that grossed $35.75 million before minimal offering expenses. Management said proceeds are expected to primarily support the EBD program, including preclinical development work toward nominating a lead clinical candidate, as well as working capital and general corporate purposes.
Phase 3 thinking and safety differentiation themes
In discussing potential next steps if ALTITUDE-AD is positive, Doherty said Acumen’s “base case” is that one additional Phase 3 study with a design similar to ALTITUDE-AD, but in a larger population, could be sufficient to support a biologics license application for early Alzheimer’s disease. He said the company has had interactions with the FDA that inform that view, while noting that decisions will ultimately be data-driven.
Siemers also discussed safety considerations in the broader amyloid-targeting field, focusing on ARIA and the distinction between asymptomatic radiographic findings and rare serious events. He noted sabirnetug is an IgG2 antibody, while certain approved drugs are IgG1 antibodies, and said the company will assess at readout whether that difference affects outcomes.
Acumen reiterated that it expects ALTITUDE-AD results late in 2026 and said it plans to continue presenting elements of its growing EBD preclinical dataset at future scientific meetings as development progresses.
About Acumen Pharmaceuticals (NASDAQ:ABOS)
Acumen Pharmaceuticals, Inc is a clinical-stage biopharmaceutical company focused on the discovery and development of oral small molecule therapies for neurodegenerative diseases. Leveraging a proprietary drug discovery platform that integrates chemoproteomics, high-throughput screening and computational chemistry, the company seeks to identify and optimize compounds that selectively modulate pathological protein aggregation. Its approach is designed to address the underlying biology of conditions such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and related proteinopathies.
The company’s pipeline comprises multiple lead candidates at various stages of preclinical and early clinical development.
