SpliceBio breaks gene therapy packaging barriers with US$135 million Series B funding
SpliceBio has secured US$135 million in Series B funding to tackle one of gene therapy’s most persistent technical barriers: the packaging capacity limitations that have rendered many genetic diseases untreatable. The Barcelona-based company’s breakthrough protein splicing technology promises to unlock therapeutic potential for conditions caused by genes too large for conventional delivery systems.
Co-led by EQT Life Sciences and Sanofi Ventures, with participation from Roche Venture Fund, the financing will propel clinical development of SB-007 for Stargardt disease – the first dual AAV gene therapy to receive regulatory clearance for this inherited form of blindness.
Engineering solutions for genetic medicine’s size problem
The breakthrough lies in SpliceBio’s elegant solution to a fundamental constraint in gene therapy. Traditional AAV vectors – the workhorses of genetic medicine – can only package genes up to 4.7 kilobases, effectively excluding treatments for diseases caused by larger genetic sequences. This limitation has left countless patients with inherited disorders beyond therapeutic reach.
SpliceBio’s protein splicing platform harnesses engineered proteins called inteins, originally developed through two decades of research at Princeton University’s Muir Laboratory. The technology splits oversized therapeutic genes into manageable fragments, delivers them via dual AAV vectors, then precisely reassembles the complete protein within target cells.
“We are building a company positioned to lead the next wave of genetic medicines,” said Miquel Vila-Perelló, Chief Executive Officer and Co-Founder of SpliceBio. The approach represents a paradigm shift that could expand gene therapy’s therapeutic scope dramatically.
First-in-class therapy targets inherited blindness
SB-007 exemplifies this platform’s potential, targeting Stargardt disease – an inherited retinal disorder that progressively destroys vision in children and adults. Caused by mutations in the ABCA4 gene, the condition has remained beyond therapeutic intervention, with no approved treatments available.
The dual AAV approach enables SB-007 to restore full-length ABCA4 protein expression regardless of a patient’s specific mutation – a universal strategy that could benefit all Stargardt patients. Following FDA clearance in December 2024, the therapy became the first dual AAV gene therapy authorised for clinical development in this indication, with the UK’s MHRA providing parallel approval.
Clinical momentum is building rapidly. The Phase 1/2 ASTRA study dosed its first patient in March 2025, whilst the observational POLARIS natural history study continues recruiting participants to establish disease progression baselines.
For more information or to enquire about participation in the studies, visit
https://splice.bio/clinical/ .
Strategic partnerships signal confidence in platform potential
The financing brings heavyweight pharmaceutical investors to SpliceBio’s board, with Daniela Begolo from EQT Life Sciences, Laia Crespo from Sanofi Ventures, and Carole Nuechterlein from Roche Venture Fund joining as directors. Their involvement reflects growing industry confidence in protein splicing’s transformative potential.
“With compelling data for its lead program, SB-007, and a highly differentiated platform, we are excited to support SpliceBio as it tackles a fundamental challenge for genetic medicines,” remarked Laia Crespo from Sanofi Ventures. “By enabling the delivery of large and complex genes through its novel AAV vector Protein Splicing technology, SpliceBio has the potential to make a significant impact on the field of gene therapy.”
The platform’s applications extend far beyond ophthalmology, with programmes advancing in neurology and undisclosed therapeutic areas. This breadth suggests SpliceBio’s technology could unlock treatments for numerous genetic disorders previously considered intractable, potentially reshaping genetic medicine by addressing diseases that have long remained beyond therapeutic reach.
