25 June 2026

Aptamer Group plc

("Aptamer", the "Company" or the "Group")

Programme and technical development update

First AI-generated Optimer® candidates delivered for laboratory testing

Discovery and manufacturing capabilities expanded through automation investment

Radioligand therapy programme advances towards first in vivo data

Kidney-targeting siRNA delivery vehicles identified with promising selectivity profile

Aptamer Group plc (AIM: APTA), the developer of next-generation synthetic binders for the life sciences industry, is pleased to announce an update on the delivery of strategic initiatives across its platform technology and therapeutic development programmes, supported by the April 2026 fundraise.

The Group is making simultaneous progress across its AI platform, platform automation, and therapeutic pipeline, demonstrating strong operational momentum across multiple pillars of the business.

AI development programme

Aptamer has initiated its AI development programme, representing a significant step towards building an AI-enabled Optimer® discovery engine. As set out at the time of the fundraise, the Group is targeting the use of AI to accelerate and enhance the discovery of Optimer® binders against challenging targets, aiming to deliver faster, improved services, with insights into undruggable proteins, such as transcription factors and RNA-binding proteins.

Following the appointment of a senior machine learning expert in April 2026, the team has progressed rapidly. The AI model architecture has been built and trained on a preliminary in-house dataset of 450,000 sequences spanning 42 protein targets; a significantly broader target range than most published AI models. Aptamer's current model has already demonstrated the ability to screen candidates, speeding up the selection process. Initial Optimer® candidates have been identified from the AI model and are being manufactured for laboratory testing.

With over half of Aptamer's in-house dataset yet to be integrated into the model, the Group anticipates further improvements in accuracy and predictive power across a wider range of targets as training continues.

Platform automation

In line with the Group's fundraising objectives, capital expenditure has been deployed to purchase new automation equipment, enhancing Aptamer's parallel discovery capabilities across all three of its discovery processes; for small molecules, proteins, and cell-based targets. The equipment has been installed and integrated into existing workflows and is already increasing discovery across the laboratory, benefiting both fee-for-service programmes and the Group's internal therapeutic development.

Further expansion is planned for manufacturing, with additional automation equipment already ordered and currently undergoing quality control ahead of deployment.

Therapeutic pipeline

Aptamer has made significant progress across its internal therapeutic development pipeline:

Discovery Programmes: The first tranche of new therapeutic targets has entered the laboratory discovery phase, with the second tranche scheduled to follow. These programmes represent Aptamer's systematic approach to exploring a broad range of high-value targets using the Optimer® platform, including those considered undruggable or requiring targeted delivery to extrahepatic tissues. The goal is to identify proprietary assets suitable for partnering or out-licensing, with data generated across these programmes also feeding directly into the Group's AI modelling capabilities.

Radioligand Therapy (RLT): Optimer® material has been shipped to the Group's partners ahead of in vivo studies, with results targeted by the end of 2026. In preparation for these studies, methods have been developed to support a robust, repeatable process for attaching radioactive labels to Optimers, thereby producing RLT candidates.

This approach will be applied across all Aptamer's RLT programmes going forward, providing a reliable platform to accelerate development timelines. The team has achieved radiolabelling in greater than 99% radiochemical purity and has successfully scaled production to activity levels comparable to those used in clinical radiopharmaceutical applications. Additionally, further targets identified for RLT development have entered the discovery phase at Aptamer, expanding the Group's therapeutic pipeline and potentially delivering new licensable assets.

Aptamer continues to work with its top 3 pharmaceutical partners, as referenced in the RNS dated 8 October 2025: Top 3 global pharma contract wins and remains focused on advancing the programme.

siRNA Delivery: Aptamer has identified Optimer® delivery vehicles that target the kidney for siRNA delivery applications. In-house lab-based tests at Aptamer have shown excellent selectivity, with no off-target interactions across a range of other cell types from alternative tissues, suggesting limited off-target interactions for use as a drug.

Further in-house studies are planned to evaluate the potential of this binder for progression to preclinical studies. This represents a new addition to the Group's delivery vehicle portfolio, following the development of the fibrotic delivery vehicle, which is progressing to in vivo studies.

The ability to target tissues beyond the liver underscores the versatility of the Optimer® platform in addressing the challenge of targeted therapeutic delivery. Two areas of commercial interest are kidney-targeted siRNA delivery and blood-brain barrier (BBB) shuttling, which enables systemic delivery to the brain via injection.

Aptamer has identified kidney-targeted delivery vehicles, with BBB shuttling currently in development. Both represent high-value opportunities, with strong interest from pharmaceutical and biopharmaceutical partners developing RNA-based therapeutics.

Each of the key development programmes initiated at the fundraise is advancing in line with the objectives communicated to shareholders. Aptamer's focus remains on reaching the critical milestones across the therapeutic pipeline, notably in vivo data from both the radioligand therapy and siRNA delivery programmes, that will support the next stage of asset development and commercial partnering discussions, as well as continuing to build the AI models to support fee-for-service offerings and in-house discovery and development efforts.

Dr Arron Tolley, Chief Executive Officer of Aptamer Group, commented: "It is exciting to see the breadth of progress being made across the business since the fundraise. New automation is allowing us to move faster in supporting customers and advancing our own therapeutic pipeline, the AI programme has moved from initiation to generating real candidates with encouraging early performance data in a matter of weeks, and we are making tangible advances across our therapeutic assets, from the identification of new kidney-targeting delivery vehicles for siRNA to the completion of large-scale radiolabelling ahead of our first in vivo studies.

"All of these elements are interconnected. Faster discovery, better data, and a growing portfolio of proprietary assets all feed into the Group's ability to create value for shareholders. We remain focused on delivering against the strategy set out at the fundraise, and I look forward to providing a further update on our trading performance as part of the year-end results in the coming weeks."

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About Aptamer Group

Aptamer Group plc (AIM: APTA) develops Optimer® binders, next-generation synthetic alternatives to antibodies that offer high specificity, improved stability, lower cost and access to targets beyond the reach of conventional modalities.

The Group operates a dual-revenue model, generating near-term revenues through fee-for-service discovery programmes while building a portfolio of proprietary therapeutic assets designed to create long-term value through licensing, royalties and supply agreements.

Aptamer is strategically focused on two of the most significant challenges in modern drug development: targeting "undruggable" proteins and enabling delivery of therapeutics to tissues beyond the liver. Its proprietary Optimer® platform, supported by more than 15 years of discovery data and an expanding AI-enabled discovery engine, is designed to accelerate the identification of high-quality binders against challenging biological targets.

The Group's internal pipeline includes targeted delivery vehicles for oligonucleotide therapeutics and radioligand therapy programmes, with upcoming in vivo studies expected to support future partnering and licensing opportunities.

Founded in 2008 and headquartered in York, UK, Aptamer works with many of the world's leading pharmaceutical companies, combining platform expertise, proprietary data and therapeutic innovation to create shareholder value.