18 March 2026

Aptamer Group plc

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

Launch of targeted radiopharmaceutical programme

Optimer® radiopharmaceutical programme initiated with Radiopharmium Ltd

Three therapeutic targets selected across high‑value clinical indications

Pipeline planned for four radiotherapy assets with in vivo data expected by end of 2026

Aptamer Group plc (AIM: APTA), the developer of next‑generation synthetic binders for the life sciences industry, is pleased to announce the launch of a new programme to develop targeted radiopharmaceuticals, in collaboration with Radiopharmium Ltd, a UK-based consultancy providing specialist expertise, contacts and access to facilities in radiopharmaceutical development, from early research to manufacturing.

Building a proprietary radiopharmaceutical pipeline

In parallel to the project with a top 3 pharma partner developing radioligand delivery vehicles (RNS dated 8 October 2025), Aptamer has identified three strategic therapeutic targets, representing high‑value clinical conditions, for which Optimer® radioconjugates will be developed. The targeted radiopharmaceuticals market is valued at approximately US$7.5 billion in 2025 and is a high‑growth high priority sector, with current targeting technologies presenting well-recognised limitations.

Radiopharmaceuticals deliver a radioactive payload directly to diseased tissue, but the payload can degrade the delivery molecule over time, shortening shelf life, increasing waste, and complicating distribution. The industry standard is to add protective additives, such as ascorbic acid. Based on recent studies, Aptamer believes that the properties of its Optimer® platform, including enhanced tissue penetration, reduced immunogenicity, and ease of chemical optimisation, position it well to address these limitations and potentially provide differentiated therapeutic candidates.

Demonstrating differentiated radioligand stability

Aptamer has previously developed fully integrated radioligand conjugates, including proprietary chemistry, linkers, and chelation systems (the part that holds the radioactive particle), and evaluated their stability under clinically relevant conditions using both Ga-68 (Gallium-68) and Lu-177 (Lutetium-177), radioactive isotopes widely used in cancer imaging and targeted treatments.

In comparative testing at 24 hours, Lu-177 Optimer®-based radioligands were stable in the presence of ascorbic acid, a known antioxidant, showing only 8% degradation in its absence. This compares with 34-83% degradation of leading peptide comparators under the same conditions, in the absence of ascorbic acid.

The observed improvement in intrinsic stability, both with and without protective additives, may support extended shelf life, reduced waste, and simplified handling and logistics. This offers a potentially differentiated profile for Optimer®-radioligands relative to existing approaches and may support ongoing and future collaborations in radioligand imaging and therapy. 

Programme development and milestones

Optimers will be developed to targets initially and validated through in vitro laboratory-based experiments. They will then be optimised and prepared for radiopharmaceutical incorporation before further in vitro and in vivo studies to assess targeting and therapeutic performance.

Combined with the Company's existing partnered radiotherapy development programme with a top‑3 global pharmaceutical company, this new initiative is expected to expand Aptamer's radiotherapy pipeline to four assets, with in vivo data targeted for delivery by the end of 2026.

World‑class expertise and preclinical access

The programme will be overseen by Dr Louis Allott, a member of Aptamer's Scientific Advisory Board and a recognised expert in the development and production of radiopharmaceuticals, with direct experience spanning laboratory discovery through to clinical translation.

Through his consultancy, Radiopharmium Ltd, Dr Allott will take a fractional role as Director of Radioligand Development for Aptamer, overseeing the radiochemical conjugation of Optimer® binders and their biological evaluation in established preclinical models. This work will involve the design, synthesis, and evaluation of radiolabelled Optimer®‑based ligands in validated animal models to assess safety, targeting performance, and therapeutic potential prior to clinical trials.

Dr Arron Tolley, Chief Executive Officer of Aptamer Group, commented:

"We are excited to launch this programme in a high‑growth field where the limitations of existing targeting technologies create a compelling opportunity for our Optimer® platform.

A key challenge in radiopharmaceuticals is maintaining the stability of the targeting molecule once it is carrying a radioactive payload. Our data indicates that Optimer®-based radioligands may offer improved stability compared to existing approaches, which could translate into practical advantages in manufacturing, distribution, and clinical use, subject to further validation.

With Louis leading this programme and access to world-class preclinical models through Radiopharmium, we are well-positioned to advance multiple assets towards in vivo validation and further demonstrate the potential of our platform in this rapidly growing therapeutic field."

Dr Louis Allott, Chief Executive Officer of Radiopharmium Ltd, commented:

"I am delighted to be working with Aptamer, a recognised leader in the field of aptamer technology with a strong track record of success. The combination of Aptamer's innovative Optimer® platform and Radiopharmium's expertise in radiopharmaceutical development makes this collaboration well‑positioned to demonstrate the potential of aptamer‑based targeting in next‑generation radiopharmaceuticals."

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About Aptamer Group

Aptamer Group is a leading developer of next-generation synthetic binders delivering innovation to the life sciences industry. The Group develops Optimer® binders, advanced molecules that work like antibodies by attaching to specific targets in the body. These binders are used in medicine, diagnostic tests, and research tools, offering benefits like high stability, reliable performance, and lower costs compared to traditional antibodies.

Aptamer operates a fee-for-service business in the US$210 billion market for antibody alternatives, working with all top 10 global pharmaceutical companies. It is also building valuable Optimer® assets with partners, aiming for future licensing revenue.

Founded in 2008, the Group listed on the London Stock Exchange AIM market in December 2021 and is headquartered in York, UK.

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