San Francisco-based Graphite Bio has launched after raising $45m in a Series A round. Graphite centres around its next-generation gene editing platform that achieves “a chief aim of gene editing for decades, which is fixing or inserting genes by targeted integration”, explains CEO Josh Lehrer. “This involves inserting genetic sequences into a location that you define in the genome which cannot be done with conventional gene therapy or CRISPR alone.”

The Series A round was led by Samsara BioCapital and Versant Ventures. As a result of this financing Samsara BioCapital’s vice-president Abe Bassan and Versant partner Carlo Rizzuto will both join Graphite’s board.

The $45m funding will be used to support Graphite’s rapidly maturing pipeline, and particularly its lead programme in sickle cell disease (SCD), “an area with much attention in the gene editing and therapy space”, Lehrer explains. Graphite hopes to commence Phase I studies of this lead candidate in early 2021.

“We are also building a new company where we anticipate [to have] about 20 employees by the end of year, building out our office and lab space, and running our experiments,” notes Lehrer.

Improving on CRISPR/Cas9 and gene therapy

Graphite’s next-generation gene editing platform aims to overcome some of the challenges that have faced CRISPR/Cas9 approaches, as well as gene therapies.

Most of these methods involve knocking out genes and struggle to insert new genetic cargo with high efficiency and precision. Instead Graphite aims to use its site-specific integration approach to precisely repair a damaged portion of the gene, complete replace a malfunctioning gene or insert a range of therapeutic genetic cargoes precisely into genomic regions. This would allow Graphite’s platform to correct the underlying cause of many severe genetic diseases, as well as other disease areas.

Importantly, this approach allows for both durable expression and minimises toxicity from off-target insertions, a problem associated with other gene editing methods.

In SCD, Graphite’s lead candidate will repair the defective gene; Lehrer notes: “The ultimate goal of treatment for SCD has always been a cure by correcting the single mutant base pair”. Using its technology, Graphite will correct the single nucleotide point mutation in the sickle b globin gene, thereby restoring the healthy haemoglobin protein and eliminating sickle cell haemoglobin.

This approach builds on the work of two professors at Stanford University – Dr Danny Dever and Dr Matt Porteus. Porteus was an academic founder of CRISPR Therapeutics, which Versant Ventures has previously invested in. Porteus is now also acting as one of Graphite’s two scientific founders.

In a statement, Porteus noted: “It is gratifying to see our work on new gene editing approaches being translated into novel therapies.

“I’m very excited to be working with Versant again on a start-up and I look forward to collaborating with Samsara and the Graphite Bio team to bring a new generation of genetic treatments to patients.”



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