Thalia Therapeutics plc (AIM: THAT), a clinical-stage biotechnology company focused on RNA-based therapeutics in oncology and cardiovascular disease, has announced the successful completion of an in vitro study for its cardiovascular gene silencing programme, now branded Lipisiran™. The study, conducted in human liver cells, demonstrated that all four bispecific siRNA constructs tested achieved positive gene silencing of both PCSK9 and lipoprotein(a), two independent drivers of cardiovascular risk. The company has now commenced in vivo studies, marking a material step forward in Lipisiran™'s development as a potential long-duration cardiovascular therapeutic.

Key Points

  • Thalia Therapeutics plc (AIM: THAT) is a clinical-stage RNA therapeutics company listed on AIM
  • The company's THAT-002 programme has been rebranded Lipisiran™ following successful completion of a cardiovascular in vitro study
  • All four bispecific siRNA constructs tested showed positive engagement with both PCSK9 and Lp(a) targets in human liver cells
  • Investors should watch for updates as in vivo studies progress and the company determines its next investment and development steps

Lipisiran™ Targets Both PCSK9 and Lp(a) With a Single Dual-Acting siRNA Therapeutic

Lipisiran™ is being developed as a long-duration, dual-acting small interfering RNA (siRNA) therapeutic designed to simultaneously target PCSK9 and lipoprotein(a), both recognised as independent risk factors for atherosclerotic cardiovascular disease. Thalia's stated objective is to create a single therapeutic agent addressing both targets, with the aim of reducing a patient's global risk of heart attack and stroke. The long-duration approach is intended to improve patient compliance and therapeutic efficacy, differentiating Lipisiran™ from existing mono-target approaches currently in development elsewhere in the sector.

All Four Bispecific Constructs Showed Positive Gene Silencing in Human Liver Cell Study

The in vitro study was designed to determine whether Thalia's bispecific siRNA constructs could lower levels of both PCSK9 and Lp(a) simultaneously in human liver cells. The announcement states that all four constructs tested achieved this objective, demonstrating positive engagement with both therapeutic targets. Notably, the study also showed that the bispecific constructs lowered PCSK9 and Lp(a) as effectively as when individual siRNA sequences were applied separately, which the company describes as a significant validation of the dual-acting approach underpinning Lipisiran™'s development thesis.

Thalia References Merck KGaA's Approximately US$1.3 Billion Bid for Silence Therapeutics as Sector Context

Chief Executive Dr David Solomon referenced the proposed acquisition of Silence Therapeutics — a former AIM-listed company with a mono Lp(a) gene silencing medicine — by Merck KGaA for an equity value of approximately US$1.3 billion, citing it as evidence of significant commercial interest in next-generation siRNA medicines targeting similar pathways. The announcement states this figure was raised to highlight sector-wide validation rather than to draw a direct valuation comparison with Thalia. Investors may note that Lipisiran™ targets both Lp(a) and PCSK9, potentially broadening its addressable therapeutic scope relative to mono-target approaches.

In Vivo Studies Now Under Way as Thalia Assesses Next Development and Funding Steps

Following the in vitro results, Thalia has confirmed it has commenced a series of in vivo studies for Lipisiran™ to establish efficacy and durability. The company did not disclose timelines, cost estimates, or specific milestones for the in vivo phase in this announcement. Dr Solomon stated the company will provide updates as appropriate and will use the in vivo data to determine its next investment and development steps. As a clinical-stage biotechnology company, Thalia remains subject to the risks inherent in early-stage drug development, where in vitro success does not guarantee comparable outcomes in in vivo or clinical settings.