11 November 2026

Thalia Therapeutics plc

("Thalia" or the "Company")

Successful completion of Lipisiran™ cardiovascular in vitro study

Positive gene silencing results support progression into in vivo studies

Thalia Therapeutics plc (AIM: THAT), a clinical-stage biotechnology company developing innovative RNA-based therapeutics and delivery technologies in oncology and cardiovascular disease, announces that it has successfully completed an in vitro study for its gene silencing cardiovascular risk reduction programme, THAT-002, achieving the target objectives that enable it to advance to in vivo studies. The THAT-002 programme will now be known as Lipisiran™.

Lipisiran™is being developed as a potentially long-duration, dual-acting siRNA therapeutic targeting both PCSK9 and lipoprotein(a) (“Lp(a)”), two independent drivers of cardiovascular disease risk. Thalia’s objective is to develop a single therapeutic agent that addresses both targets to reduce global cardiovascular risk of heart attack and stroke. The long-duration impact is intended to improve patient compliance and therapeutic efficacy.

The in vitro study in human liver cells was designed to determine whether Thalia’s bispecific siRNA constructs could lower levels of both PCSK9 and Lp(a) in the target cells. All four constructs tested showed positive results, indicating engagement with the therapeutic targets.

The study also showed that Thalia’s bispecific siRNA constructs lowered both PCSK9 and Lp(a) as effectively as when the individual siRNA sequences were treated separately.

Following these successful in vitro outcomes, the Company has commenced a series of in vivo studies for Lipisiran™ to establish efficacy and durability.

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

“We are greatly encouraged by these in vitro results that see the evolution of the concept of THAT-002 to the beginnings of a potential product in Lipisiran™ with the goal of reducing the global risk of heart attack and stroke.

“Showing that our bispecific constructs can lower the targets PCSK9 and Lp(a) as effectively as the individual siRNA sequences is a significant step forward in validating our thesis as to the merits of a long-duration, dual-acting siRNA therapeutic to address the huge cardiovascular disease market. The proposed acquisition of Silence Therapeutics, a former AIM-listed company, by Merck KGaA for an equity value of approximately US$1.3 billion, which also has a mono Lp(a) gene silencing medicine, highlights the significant interest in effective next-generation siRNA medicines.

“We have now begun our in vivo studies, and I look forward to providing updates as and when appropriate and, in doing so, determining the next investment and development steps as we seek to advance Lipisiran™.”

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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 Lipisiran™ (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