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Gene Therapy

Exsilio launches for messenger RNA genomic medicine

The company’s CEO says its technology avoids problems with viral vectors

by Sarah Braner
June 28, 2024


Exsilio Therapeutics launched on Wednesday with an $82 million series A fundraising round co-led by Novartis Venture Fund and Delos Capital.

A headshot of Exsilio Therapeutics' current interim CEO, Tal Zaks.
Credit: OrbiMed
Exsilio Therapeutics' interim CEO, Tal Zaks, was formerly the chief medical officer of Moderna.

The company’s interim CEO, Tal Zaks, says that while genomic medicine still has potential, the field has hit a roadblock. With currently available techniques, it takes a long strand of DNA to correct an entire gene, but delivery currently requires a viral vector, which Zaks says poses problems for safety and redosing. Alternatively, he says, one could use a lipid nanoparticle and RNA to make small changes in the genome but not insert a long strand of DNA.

Zaks says Exsilio “marries the best of both worlds” of these two techniques. Exsilio says it will use lipid nanoparticles and messenger RNA (mRNA) to integrate whole genes into “safe harbors” in the genome, building off of mobile genetic elements, or genetic material that can change locations within the genome. But Zaks declined to share the details of how the technology works.

Prior to running Exsilio, Zaks was the chief medical officer of Moderna, one of the first companies to shepherd a different RNA-based technology, mRNA vaccines, into the limelight. RNA editing is also a growing area: biotech firms such as Prime Medicine and Amber Bio launched before Exsilio, and recently two papers in the journal Nature showed the potential of bridge RNA in editing larger segments of genes.

Exsilio’s approach has been driven not only by advances in scientific understanding but also by guidance issued by the US Food and Drug Administration on what information should be included in an application for a new gene therapy to be given the green light. “Companies like ours now have a much clearer roadmap to what it takes to demonstrate safety and efficacy of a genomic medicine,” Zaks says.

The firm will use the funding to further develop the platform and to establish a presence in Boston. The company is also searching for a permanent CEO to take the wheel from Zaks.



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