Circio Holding has presented new in vivo data showing its AAV-circVec platform achieved a 40-fold increase in protein expression in heart tissue compared with conventional mRNA-based adeno-associated virus (AAV) gene delivery. The data were presented at the European Society of Cell and Gene Therapy (ESGCT) annual meeting 2025 in Seville, Spain.

According to Circio, the circVec 3.2 construct demonstrated significantly higher and more localised expression levels in cardiac tissue, confirmed through both longitudinal live imaging and post-mortem tissue analysis. The findings were described as statistically robust and reproducible across multiple test models.

The company is now applying the AAV-circVec platform to the development of a potential therapy for Danon disease, a rare inherited cardiac disorder with no approved treatment options.

Dr Thomas B Hansen, chief technology officer at Circio, said: “Circio has worked systematically to optimise the circVec design for AAV gene delivery over the past two years. The latest circVec 3.2 generation incorporates a novel genetic feature that drives up AAV protein expression to levels that substantially exceed conventional mRNA-based AAVs. We are now advancing rapidly to validate these findings in relevant genetic disease models.”

In addition to its cardiac data, Circio reported similar improvements in expression efficiency across several other tissues and AAV variants, suggesting wider applicability of the technology as a gene expression platform. Earlier versions of the construct (circVec 2.0) also showed progressive signal accumulation following ocular delivery, and testing of the new circVec 3.2 and next-generation 4.0 constructs is underway in eye and other tissue models.

Dr Erik Wiklund, chief executive officer of Circio, said: “ESGCT provides an excellent forum to showcase the circVec platform to a wide academic and industry audience as a potential solution to address the key issue preventing broad adoption and success of AAV gene therapy.”

The company said the results support circVec as a potential strategy to improve AAV delivery efficiency, reduce vector doses, and enhance the safety profile of gene therapy approaches across multiple disease areas.