ProMIS Neurosciences Announces Second Quarter 2025 Financial Results & Corporate Highlights U.S. FDA Grants Fast Track Designation for PMN310 in Alzheimer's Disease, enhancing program's potential for priority review PREC

ProMIS Neurosciences Announces Second Quarter 2025 Financial Results & Corporate Highlights

U.S. FDA Grants Fast Track Designation for PMN310 in Alzheimer's Disease, enhancing program's potential for priority review

PRECISE-AD Phase 1b Trial in Alzheimer's Disease Progressing on Schedule: Over 50% enrolled, no cases of ARIA and no patient dropouts to date

Strengthened Financial Position with $21.6 Million in Gross Proceeds Raised in July 2025

Cambridge, Massachusetts - August 13, 2025 ProMIS Neurosciences Inc. (Nasdaq: PMN), a clinical-stage biotechnology company focused on the generation and development of antibody therapeutics targeting toxic misfolded proteins in neurodegenerative diseases, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD), today announced financial results for the second quarter ended June 30, 2025.

"The team's exceptional focus and execution in the first half of 2025 culminated in what has been an extraordinary past month for ProMIS and its key stakeholders," said Neil Warma, Chief Executive Officer of ProMIS Neurosciences. "As of August 12, enrollment in the PRECISE-AD Phase 1b Alzheimer's disease trial has surpassed 50% of the planned 128 patients, marking strong recruitment progress. Importantly, no cases of amyloid-related imaging abnormalities (ARIA), including brain swelling or microhemorrhage, have been observed to date, and no patient dropouts have been reported, reinforcing PMN310's potential favorable safety profile. At this stage, we remain on track to deliver 6-month blinded interim results in 2Q 2026 and final topline results in 4Q 2026."

"In addition, our recent FDA Fast Track designation for PMN310 underscores the urgent need for safer, more effective Alzheimer's treatments. Building on this regulatory milestone and the positive clinical progress of PRECISE-AD, we secured approximately $21.6 million in gross proceeds to accelerate PMN310's advancement toward its next phase of development," added Mr. Warma.

Corporate Highlights

EpiSelectTM Drug Discovery Engine

In July 2025, ProMIS presented on its proprietary protein-misfolding platform, EpiSelectTM at AAIC 2025 in a presentation titled Protein misfolding-speci c epitope identi cation for passive and active immunotherapy of neurodegenerative diseases (Abstract Number: 98670)

The presentation highlighted the following:

Alzheimer's Disease Program (PMN310)

ProMIS' lead candidate, PMN310, is a humanized IgG1 antibody directed toward toxic A O that are believed to be a major driver of AD.

ProMIS continues to advance its PMN311 A vaccine program in AD based on its oligomer target epitope.

Key Pipeline Programs

Second Quarter 2025 Financial Highlights

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 and other misfolded protein 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).

PMN310, the Company's lead product candidate for the treatment of AD, is a potentially best-in-class, humanized monoclonal antibody that has been designed to selectively target only the toxic oligomers, avoiding plaque, thereby potentially reducing or eliminating ARIA liability and improving safety. In addition, because PMN310 may not to be limited by off-target binding or side effects, PMN310 could potentially offer an improved efficacy profile over other amyloid-directed antibody therapeutics. PMN310 was granted Fast Track designation by the U.S. Food and Drug Administration in July 2025.

Forward-looking Statements

Nasdaq has not reviewed and does not accept responsibility for the adequacy or accuracy of this release. 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. In some cases, but not necessarily in all cases, forward-looking information can be identified by the use of forward-looking terminology such as "plans", "targets", "expects" or "does not expect", "is expected",

"excited about", "an opportunity exists", "is positioned", "estimates", "intends", "assumes", "anticipates" or "does not anticipate" or "believes", or variations of such words and phrases or state that certain actions, events or results "may", "could", "would", "might", "will" or "will be taken", "occur" or "be achieved". In addition, any 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 1b study in AD patients and expectations of such study results, including interim results in the first half of 2026 and topline results by the end of 2026, statements relating to the Company's progress, including enrollment and dosing for its Phase 1b clinical trial, the potential for such studies to provide the first proof-of-concept data for PMN310, the potential that PMN310 has the potential to positively benefit patients with AD, the targeting of toxic misfolded proteins in neurodegenerative diseases that the Company believes may directly address fundamental AD pathology (including the belief and understanding that toxic oligomers of A are a major driver of AD) and have greater therapeutic potential due to reduction of off-target activity, a computationally-derived A vaccine for AD and the Company's PMN310 antibody and vaccine candidate, management's belief that its patented platform technology has created an antibody candidate specific to toxic misfolded oligomers known to be present in AD, therapeutic activity and preferential targeting of toxic soluble aggregates by A -directed antibodies and the potential implications thereof, the Company's pipeline, including its platform, including the capabilities thereof and the application of its platform to other diseases, statements regarding discovery candidates, timing of IND-enabling studies, preclinical data, recent presentations of such preclinical data and the takeaways therefrom, the ability to continue its growth and realize the anticipated contribution of the members of its board of directors and executives to its operation and progress, use of capital expenses, future accumulated deficit and other financial results in the future, ability to fund operations, the ability to maintain enough liquidity to execute its business plan and its ability to continue as a going concern. 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 clinical results may not be indicative of future results, the Company's ability to fund its operations and continue as a going concern, its accumulated deficit and the expectation for continued losses and future financial 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, 2024 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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