Gene-editing firm Prime Medicine files $140m public offer

Gene-editing biotech Prime Medicine has priced a follow-on public offering, hoping to raise $140 million to advance its pipeline of one-shot therapies for severe genetic disorders.

The Cambridge, Massachusetts-based company is offering 19.2 million shares at $6.25 each and has scaled up its earlier expectations for the proceeds from $125 million.

Prime Medicine is working on a pipeline of 18 programmes aimed at correcting pathogenic mutations and has shown proof of principle for its ‘search-and-replace’ Prime Editing platform in non-human primate studies.

The company was set up by gene-editing pioneers David Liu, who co-founded Editas Medicine and Beam Therapeutics, and Andrew Anzalone of the Broad Institute of MIT and Harvard University.

Prime Editing is the result of work in their labs and aims to improve on the CRISPR/Cas9 technology by allowing changes to be made to DNA without breaking the double helix or using donor DNA. It is more broadly applicable than CRISPR/Cas9, according to the company, and could be used to target more than 90% of known disease-causing mutations.

Prime Medicine’s lead candidates are PM359 for chronic granulomatous disease (CGD), which was recently awarded rare paediatric disease designation (RPDD) by the FDA, along with candidates for glycogen storage disease 1b (GSD1b) and retinitis pigmentosa.

Data reported at the European Society of Gene and Cell Therapy Congress last October showed that it was possible to achieve editing of up to 83% of target cells in the liver with a lipid nanoparticle-delivered editor designed to correct one of the most prevalent disease-causing mutations of GSD1b, with no safety concerns.

The latest offering comes after Prime Medicine raised $115 million in a Series A and $200 million in a Series B in 2021, and $175 million in an initial public offering in 2022. Earlier this year, the company also received $15 million in funding from the Cystic Fibrosis Foundation (CFF) to start up a gene-editing programme in the disease.