Exsilio Therapeutics, a Boston-based biotech startup, has secured $82 million in funding and hopes to target genetic conditions with a new approach to gene therapy. Tal Zaks, the company’s CEO, was the chief medical officer at Moderna while that company was developing its messenger RNA vaccine for COVID-19. Exsilio’s goal is to use mRNA to overcome some of the current limitations in gene therapy.
A Redosable Approach to Gene Therapy
Exsilio, which means “leap” in Latin, intends to design medicines that can insert entire genes into cells and be administered repeatedly. Unlike current viral delivery systems, Exsilio’s approach uses genetic elements encoded in mRNA, which are delivered into the body via lipid nanoparticles.
The repeated dosing paradigm is particularly important for patients whose immune systems might destroy the viral vector before it can deliver its therapeutic payload. As demonstrated by mRNA-based COVID-19 vaccines, repeated dosing could overcome this hurdle. Safety remains a primary concern in genomic medicine, and Exsilio is addressing this by targeting “safe harbor sites” within the genome for gene insertion, reducing the risk of unintended consequences.
“Exsilio’s approach leverages the advantages of mRNA and goes a step further by encoding genes that integrate permanently, offering the possibility of curative rather than transient effect,” said Zaks in a statement. “This financing will help us advance our genomic medicines and select promising lead candidates so that we can bring much-needed new options to patients,” he added.
Expanding Potential
One of the significant advantages of Exsilio’s technology is its potential to treat a wide range of conditions, including genetic diseases, cancer and autoimmune disorders. This flexibility is crucial, especially for inherited conditions linked to multiple mutations. By avoiding the use of viral vectors, which can trigger immune responses and have limitations in gene size, Exsilio’s method aims to avoid many of the common challenges associated with traditional gene therapies. “We should be able to dose patients regardless of their pre-existing immunity as well as repeatedly until the desired therapeutic gene dosage is obtained,” Zaks explained to Biopharma Dive.
Competitive Edge and Future Prospects
Exsilio sets itself apart from existing gene therapy approaches. One model inserts singular genes using viral vectors, as seen in treatments like Novartis’ Zolgensma® for spinal muscular atrophy. Another model uses precision DNA editing with technologies like CRISPR, which is limited to small changes. Exsilio’s technology aims to combine the best of both worlds, enabling large-gene integration with enhanced safety and repeated dosing.
The mRNA approach offers cost efficiencies, potentially lowering the cost of gene therapies, which can run into millions of dollars. “The process can be done in pretty small containers or vats, and it takes a much shorter timeframe than typical biologics. That’s why mRNA is so cost-efficient,” Zaks said. “That has implications throughout the development life cycle, not just when you talk about being cost-effective for the patient at the end. But actually to discover and develop these medicines because it means that it’s cheaper to make and test early.”
A Strong Start
Exsilio’s Series A funding round, led by Novartis Venture Fund and Delos Capital, reflects strong confidence in the company’s technology. “We were captivated by Exsilio’s genomic medicines approach that stands to enable large-gene integration in a safe and redosable manner,” said Aaron Nelson, a managing director at Novartis Venture Fund and Exsilio board member.
Exsilio Therapeutics is still in the early stages of its journey. Still, with a solid financial foundation and a groundbreaking approach to genetic medicine, it is well-positioned to make significant strides. As the company moves forward, the biotech world will watch closely to see if Exsilio can deliver on its promise to leap forward in genetic medicine.
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