25 September 2026

Thalia Therapeutics plc

("Thalia" or the "Company")

RNA gene-silencing cardiovascular programme advances

Pre-clinical studies initiated towards FDA filing

Thalia Therapeutics plc (AIM: THAT), a clinical-stage biotechnology company developing innovative RNA-based therapeutics and delivery technologies in oncology and cardiovascular disease, announces it has completed the initial chemistry synthesis of the siRNA gene-silencing medicines for its cardiovascular programme, THAT-002.

THAT-002 is being developed as a potentially long-duration, dual-acting siRNA therapeutic targeting PCSK9 and lipoprotein(a) (“Lp(a)”), two factors of cardiovascular disease risk. Thalia’s objective is to develop a single therapeutic that addresses both targets to reduce global cardiovascular risk.

Thalia began preclinical work on THAT-002 in September 2026 with WuXi AppTec (Hong Kong) Limited (“WuXi”), a global provider of biology services and solutions. Completion of the chemistry and synthesis work marks the conclusion of the first step in this programme, allowing the commencement of in vitro studies ahead of in vivo work scheduled for later in the fourth quarter.

Data from the in vitro study and subsequent in vivo studies will inform further preclinical development of THAT-002 as it progresses toward IND-enabling studies and initiation of clinical studies in humans. It will also support the Company’s work to strengthen the programme’s intellectual property and patent application.

Dr David Solomon, Chief Executive Officer of Thalia, commented:

“Completing the initial chemistry synthesis allows us to move THAT-002 into cell-based tests. This is an early but important step in assessing our approach to targeting PCSK9 and Lp(a) with a single therapeutic, and it is pleasing that it has been met on time and on budget.

“We look forward to reviewing the data at each stage of the pending work programmes, providing updates as and when appropriate and, in doing so, determining the next investment and development steps.  Following preclinical studies, the Company’s objective is to file with the FDA for human clinical studies.

“This gene-silencing programme has the promise of reducing global cardiovascular risk of heart attack and stroke by lowering key factors that have been identified as contributing to cardiovascular disease.”

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About Thalia Therapeutics plc

Thalia Therapeutics is a clinical-stage biotechnology company developing innovative RNA-based therapeutics and delivery technologies across oncology and cardiovascular disease. With a growing, differentiated pipeline, de-risked by validated therapeutic targets, we aim to treat disease at its source by silencing or modifying the genes that cause or contribute to it.

Our clinical-stage programme miRisten (THAT-001) is a microRNA therapeutic in development for Acute Myeloid Leukaemia (AML). Alongside this, our preclinical bispecific siRNA (THAT-002) is being developed as a potential long-acting treatment for atherosclerotic cardiovascular disease by addressing two independent drivers of cardiovascular risk. Our proprietary delivery technology, Nuvec® (THAT-003), offers the potential to overcome the fundamental challenges of RNA delivery, enabling targeted, scalable RNA therapeutics.

For further information visit www.thaliatx.com