BioPharma, Pharma

Solution to big gene therapy obstacle leads to Spain’s largest biotech Series A round

SpliceBio will use its €50 million in financing to advance development of a gene therapy for Stargardt disease, a rare eye disorder. The biotech’s technology enables the delivery of genes that are too large for the capacity of the adeno-associated viruses widely used in the delivery of genetic medicines.


Gene therapy has a capacity problem. The engineered viruses used to deliver these therapies have limited room to carry genetic cargo. SpliceBio is developing technology that could allow for the delivery of larger genes, and it has raised €50 million to support its research that includes its first target: a gene therapy for a rare, inherited eye disorder.

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A Deep-dive Into Specialty Pharma

A specialty drug is a class of prescription medications used to treat complex, chronic or rare medical conditions. Although this classification was originally intended to define the treatment of rare, also termed “orphan” diseases, affecting fewer than 200,000 people in the US, more recently, specialty drugs have emerged as the cornerstone of treatment for chronic and complex diseases such as cancer, autoimmune conditions, diabetes, hepatitis C, and HIV/AIDS.

The Series A round of financing announced Wednesday was co-led by UCB Ventures and Ysios Capital.

Gene therapies typically reach their cellular destinations via adeno-associated viruses (AAV). While these viral vectors continue to be the delivery vehicle of choice, their capacity limitations place certain diseases out of reach. Barcelona-based SpliceBio aims to enable the delivery of larger genetic cargos by splitting up the load. The biotech accomplishes this with a family of proteins called inteins. These proteins are responsible for protein splicing, a biochemical process that involves cleaving and forming peptide bonds.

Inteins as they are found in nature are not suitable for applications in human therapies. SpliceBio engineers inteins to carry out protein splicing. According to the company, these engineered inteins enable splicing of a protein, which is then reconstituted to its full-length inside the body. The startup’s technology is based on research from the Muir Lab at Princeton University.

SpliceBio’s lead program is for Stargardt disease, a rare eye disorder that leads to degeneration of the macula, a part of the retina. It’s caused by a mutation to the ABCA4 gene, a gene that’s too large to be carried by a single AAV vector. SpliceBio said it will use the Series A cash to advance its Stargardt disease gene therapy to tests in humans. While ophthalmological applications are the first focus of the startup, the company said that its technology has been validated in “several other organs beyond the retina.”

The Princeton spinout was initially named ProteoDesign, and its initial focus was cancer. In 2020, the startup rebranded as Splice Bio after raising seed financing from Ysios and Asabys Partners. (The revision of company name to a single word appears to have happened this year.) Asabys also invested in the latest financing announced Wednesday, which SpliceBio says is the largest Series A round for a Spanish biotech company. Other new investors in the round include New Enterprise Associates, Gilde Healthcare, and Novartis Venture Fund.

“We are proud to have been involved with the company since its early days and are very impressed with the progress achieved to date,” Ysios Managing Partner Joël Jean-Mairet said in a prepared statement. “SpliceBio’s platform represents an unprecedented opportunity to expand the universe of diseases that can be addressed with gene therapy. This financing is also a testament to the growing potential of the biotech hub in Barcelona.”

Photo by Flickr user Jorge Franganillo via a Creative Commons license