PMN310 demonstrated dose-dependent reduction of amyloid-beta oligomers in human cerebrospinal fluid following a single dose in healthy volunteers

Represents one of the first quantitative measures of treatment-related effects on oligomer levels in a clinical trial

Company on track to present six-month blinded interim data from its Phase 1b trial in the coming weeks

Poster to be presented today, July 14, at the 2026 Alzheimer’s Association International Conference® (AAIC)

Cambridge, Massachusetts, July 14, 2026 (GLOBE NEWSWIRE) -- ProMIS Neurosciences Inc. (NASDAQ:PMN), a clinical-stage biotechnology company developing antibody therapeutics and vaccines targeting toxic misfolded proteins in neurodegenerative diseases, today announced the first human evidence of dose-dependent amyloid-beta oligomer (AβO) reduction by its lead Alzheimer’s drug candidate, PMN310, presented at AAIC 2026.

The findings, drawn from analysis of samples collected during the Company's Phase 1a trial in healthy volunteers (NCT06105528), showed that individuals receiving PMN310 exhibited a dose-dependent reduction in detectable AβO in cerebrospinal fluid (CSF) at both three and 29 days after dosing. While healthy individuals carry lower oligomer burdens than Alzheimer's patients, amyloid-beta oligomers are detectable in CSF even in cognitively normal adults, making this a meaningful measure of target engagement. This represents one of the first quantitative demonstrations of treatment-related oligomer reduction in humans.

"These data represent an important milestone for PMN310 and offer evidence supporting our precision medicine approach in treating Alzheimer's disease," said Neil Warma, Chief Executive Officer of ProMIS Neurosciences. "Using CSF samples from our Phase 1a study, subjects receiving PMN310 showed a clear dose-dependent reduction in oligomer particles, which, we believe, represents direct evidence that PMN310 was able to reach the brain and engage its intended target. We are grateful to our partner, attyloid, for their contribution to the assay development that made this possible, and we intend to deploy this assay in our ongoing PRECISE-AD Phase 1b trial to directly measure oligomer burden in Alzheimer's patients before and after treatment."

Dr. Johanne Kaplan, Chief Development Officer, ProMIS Neurosciences said, "A large body of evidence in Alzheimer's disease research indicates that disease pathogenesis is not directly driven by plaque burden, but rather by soluble toxic amyloid-beta oligomers. Selectively targeting oligomers while avoiding plaque could have a meaningful impact on both the efficacy and safety of treatment, reducing off-target binding that limits effective dosing and potentially limiting the ARIA side effects associated with plaque-binding antibodies. We believe the data presented today provide pharmacodynamic evidence supportive of PMN310's differentiated mechanism of action."

Mr. Warma added, "Building on this evidence of target engagement, we look forward to sharing blinded six-month interim data from the PRECISE-AD Phase 1b trial in the coming weeks. This interim analysis will focus on blinded aggregate safety data and overall trends in selected biomarkers across study participants. Top line unblinded results are expected in early Q1 2027."

Key Results Presented at AAIC

Amyloid-beta oligomers in CSF were measured using surface-based fluorescence intensity distribution analysis (sFIDA) developed by attyloid GmbH, an assay which enables direct quantification of oligomer particles with unprecedented sensitivity. While the assay is currently exploratory, it provides pharmacodynamic evidence of target engagement by PMN310.

Oligomer reduction: Placebo-treated healthy volunteers (N=40) in the Phase 1a trial exhibited low levels of AβO in CSF. PMN310 administration resulted in a dose-dependent reduction in detectable AβO particles in CSF.

Strict oligomer selectivity: PMN310 demonstrated strong binding to AβO with no interaction with monomers by surface plasmon resonance (SPR), and no detectable reactivity with plaques or vascular deposits of Aβ in AD brain tissue sections, representing the potential for a differentiated clinical profile.

Favorable pharmacokinetics and tolerability: PMN310 was generally well-tolerated, with CSF concentrations linearly dose-dependent, reaching 100–600 times the estimated molar concentration of AβO, and a CSF half-life of approximately 27 days.

Preclinical memory preservation: In a transgenic AD mouse model, PMN310 preserved memory and learning performance in the Morris Water Maze task.

AAIC Presentation details

Title:	Activity and clinical progress of PMN310 designed to selectively target toxic Aβ oligomers for greater potency in Alzheimer’s disease
Date/Location:	July 14, 2026, Poster presentation, AAIC Exhibit Hall, 7:30 am-4:15pm
Presenter:	Dr. Johanne Kaplan, CDO, ProMIS Neurosciences

About PMN310 and the PRECISE-AD Trial for Alzheimer’s Disease (AD)

PMN310, ProMIS’ lead product candidate for the treatment of AD, is a humanized IgG1 monoclonal antibody designed to selectively target only the toxic oligomers of amyloid-beta (AβOs), believed to be among the earliest and most damaging drivers of Alzheimer's disease, while avoiding binding to amyloid plaques and vascular deposits. This selectivity may reduce or eliminate the risk of amyloid-related imaging abnormalities (ARIA), including brain swelling (ARIA-E) and microhemorrhages (ARIA-H), which are commonly associated with plaque-binding antibodies. PMN310 was granted Fast Track Designation by the U.S. Food and Drug Administration in July 2025.

Based on encouraging results from a Phase 1a trial (NCT06105528) in healthy volunteers, ProMIS initiated the PRECISE-AD Phase 1b trial to evaluate PMN310 in patients with mild cognitive impairment due to AD or mild AD. PRECISE-AD (NCT06750432) is a randomized, double-blind, placebo-controlled study evaluating the safety, tolerability, and pharmacokinetics of multiple ascending doses (5, 10, and 20 mg/kg) of intravenous PMN310. The study has completed enrollment of 144 participants across the three dosing cohorts who are being treated for twelve months. It is designed to provide meaningful insight into the effects of PMN310 on biomarkers and clinical outcomes.

About ProMIS Neurosciences Inc.

ProMIS Neurosciences is a clinical-stage biotechnology company committed to the discovery and development of therapeutic antibodies and vaccines selective for toxic oligomers associated with the development and progression of neurodegenerative and other misfolded protein diseases. The Company’s proprietary target discovery engine, EpiSelect™, has been shown to predict novel targets known as Disease Specific Epitopes (DSEs) on the molecular surface of misfolded proteins that cause neurodegenerative diseases, including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), multiple system atrophy (MSA), and Parkinson’s disease (PD). ProMIS has offices in Cambridge, Massachusetts (USA) and Toronto, Ontario (CAN).

Forward-Looking Statements

This press release contains forward-looking statements that are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Certain information in this news release constitutes forward-looking statements and forward-looking information (collectively, "forward-looking information") within the meaning of applicable securities laws. Statements that refer to expectations, projections or other characterizations of future events or circumstances contain forward-looking information. Specifically, this news release contains forward-looking information relating to the Company’s Phase 1a clinical trial, results of the use of the assay discussed in this release and intent to deploy such assay in the future, the PRECISE-AD Phase 1b clinical trial, target engagement and biomarker findings, the expected timing and nature of blinded interim and topline clinical data of PMN310, its mechanism of action and potential benefits and the Company’s development plans. Statements containing forward-looking information are not historical facts but instead represent management’s current expectations, estimates and projections regarding the future of our business, future plans, strategies, projections, anticipated events and trends, the economy and other future conditions. Forward-looking information is necessarily based on a number of opinions, assumptions and estimates that, while considered reasonable by the Company as of the date of this news release, are subject to known and unknown risks, uncertainties and assumptions and other factors that may cause the actual results, level of activity, performance or achievements to be materially different from those expressed or implied by such forward-looking information, including, but not limited to, the risk that preclinical results or early results may not be indicative of future results. Important factors that could cause actual results to differ materially from those indicated in the forward-looking information include, among others, the factors discussed throughout the "Risk Factors" section of the Company’s most recently filed Annual Report on Form 10-K for the year ended December 31, 2025 and in its subsequent filings filed with the United States Securities and Exchange Commission. Except as required by applicable securities laws, the Company undertakes no obligation to publicly update any forward-looking information, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise.

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