# SpliceBio **Source:** https://geo.sig.ai/brands/splicebio **Vertical:** BioTech **Subcategory:** Gene Therapy (Protein Trans-Splicing) **Tier:** Emerging **Website:** splice.bio **Last Updated:** 2026-04-14 ## Summary Raised $135M Series B led by Sanofi Ventures and EQT (Jun 2025). First patient dosed in Phase 1/2 for Stargardt disease (Jan 2026). Overcomes 4.7kb AAV cargo limit. ## Company Overview SpliceBio is a gene therapy company whose protein trans-splicing platform overcomes the 4.7-kilobase cargo limit of adeno-associated viral (AAV) vectors — the primary delivery vehicle for gene therapy — unlocking treatments for large-gene diseases previously untreatable. The company raised $135 million in Series B financing co-led by Sanofi Ventures and EQT Life Sciences in June 2025, and dosed its first patient in Phase 1/2 Part B for SB-007 in Stargardt disease in January 2026. The AAV cargo limit has been a fundamental constraint in gene therapy since the field's inception: genes larger than 4.7 kilobases cannot fit inside a standard AAV capsid, excluding conditions like Stargardt disease (ABCA4, 6.8kb), Usher syndrome (USH2A, 15.6kb), and many rare neurological diseases from gene therapy treatment. SpliceBio's trans-splicing approach splits the gene across two AAV vectors and uses engineered intein proteins to stitch the protein back together inside the cell — effectively doubling the gene therapy cargo capacity. Sanofi's direct Ventures arm investment is strategically significant: Sanofi has one of the world's largest rare disease and gene therapy portfolios, and co-leading the SpliceBio Series B signals active interest in trans-splicing for programs in its pipeline. The Stargardt Phase 1/2 data from 2026 will be the first clinical validation of protein trans-splicing technology in humans. ## Frequently Asked Questions ### What does SpliceBio do? Gene therapy using protein trans-splicing — splits large genes across two AAV vectors and reassembles the protein inside cells, overcoming the 4.7kb AAV cargo limit for large-gene diseases. ### How much has SpliceBio raised? $135M Series B co-led by Sanofi Ventures and EQT Life Sciences (June 2025). First patient dosed in Phase 1/2 for Stargardt disease January 2026. ### What diseases does SpliceBio's platform unlock? Stargardt disease (ABCA4, 6.8kb), Usher syndrome (USH2A, 15.6kb), and large-gene neurological diseases — conditions previously excluded from gene therapy due to AAV cargo limits. ### Why is Sanofi's investment strategic? Sanofi has a large rare disease and gene therapy pipeline. Co-leading the Series B signals active interest in using trans-splicing for existing Sanofi programs with large-gene targets. ### What is protein trans-splicing and how does SpliceBio use it? Protein trans-splicing uses intein sequences (naturally occurring protein fragments that self-splice) to reconstitute a large protein from two smaller pieces delivered separately. SpliceBio applies this to gene therapy: splitting large therapeutic genes (too big for a single AAV vector) into two pieces, delivering each in separate AAVs, and allowing intein-mediated reconstitution inside target cells. This doubles the effective gene payload capacity of AAV vectors — unlocking gene therapy for diseases with large causative genes that were previously untreatable. ### What diseases does SpliceBio's platform enable? SpliceBio targets genetic diseases caused by large genes that exceed AAV capacity (~4.7kb): COL7A1 (recessive dystrophic epidermolysis bullosa — a devastating skin disease), ABCA4 (Stargardt disease — inherited macular degeneration), CEP290 (Leber congenital amaurosis), and others. These conditions represent significant orphan disease populations with premium pricing potential and FDA-designated pathways (Breakthrough Therapy, Orphan Drug), and have been waiting for a gene therapy delivery solution. ### What is the Sanofi strategic investment and collaboration? Sanofi invested in SpliceBio's Series B and established a research collaboration, gaining rights to explore protein trans-splicing for Sanofi's gene therapy programs including rare disease and potentially ophthalmology indications. Sanofi's gene therapy ambitions (following its acquisition of Ablynx, investment in Translate Bio) make SpliceBio's platform strategically relevant for Sanofi's pipeline programs involving large genes currently constrained by AAV capacity. The collaboration structure likely includes option rights on SpliceBio's lead programs. ### How much has SpliceBio raised and what is the clinical timeline? SpliceBio has raised over $100 million from Sanofi, Sofinnova Partners, and other European biotech investors to advance its ophthalmology and skin disease programs. The company is advancing ABCA4 (Stargardt disease) and COL7A1 (RDEB) as lead clinical programs, targeting IND filing in 2025-2026. Stargardt disease specifically has seen significant investment (Meiragtx, Eyevensys also pursuing) with clear clinical endpoints (visual acuity, retinal thickness) and established regulatory precedent from other inherited retinal disease approvals. ## Tags healthtech, b2b --- *Data from geo.sig.ai Brand Intelligence Database. Updated 2026-04-14.*