Prime Medicine, the developer of a “search and replace” gene editing platform, has launched an upsized initial public offering (IPO) that raised $175 million in gross proceeds—about $24 million more than projected just last week.

Prime finished its first day of trading at $15.37—nearly 10% below its IPO price of $17 a share, the midpoint of its price range. The company originally planned to sell 8.9 million shares last week, but boosted that to 10,294,118 shares on Wednesday.

The closing price was 19% below Prime’s high price for the day of $19 a share. Prime’s shares began the day at $18.97.

Prime trades its shares on the Nasdaq Global Market under the symbol PRME.

Gross proceeds for Prime could reach $201.25 million—just over the $200 million estimate offered earlier this month by Renaissance Capital, which tracks the IPO market. Prime is among the year’s three largest initial public offerings for a biotech company, following vision care drug/device developer Bausch + Lomb ($630 million gross proceeds) and vaccine developer HilleVax (also $200 million).

Prime has granted the underwriters of its IPO a 30-day option to purchase up to an additional 1,544,117 shares of common stock at the initial public offering price, less the underwriting discounts and commissions.

Prime previously projected it would generate between $136.2 million and $160.2 million in net proceeds—based on selling 8.9 million shares at between $16 and $18 a share.

At $17 a share, Prime said, the largest share of net proceeds—approximately $90 million—would fund continued research and development of its Prime Editing portfolio, including preclinical studies and advancement through potential preclinical proof-of-concept.

Prime projected using approximately $65 million of net proceeds for Investigational New Drug (IND)-enabling studies and potential initiation of clinical studies for some of its current therapeutic programs; and another approximately $65 million for continued advancement of its Prime Editing platform and discovery-stage research for other potential programs.

The company also projected using approximately $50 million in net proceeds to develop its early-stage manufacturing processes and build out a dedicated facility for its medicinal chemistry, process development, and analytical chemistry groups. The facility would include a non-GMP piloting lab for making guide RNA, mRNA, and synthesizing lipids.

The remainder of the net proceeds would fund general corporate purposes.

Prime disclosed its IPO plans last month. In its most recent Registration Statement, filed October 13, Prime disclosed its pipeline of 18 programs, all in discovery phases. Half are within its “immediate” strategic category, and include programs targeting blood, liver, eye, and ear disorders.

The rest of Prime’s pipeline includes programs targeting Duchenne muscular dystrophy, cystic fibrosis, and seven repeat expansion disease-targeting programs.

Prime Medicine was co-founded by gene editing pioneer David Liu, PhD, and Andrew Anzalone, MD, PhD, who conceived of and developed the company’s technology while he was a Jane Coffin Childs Memorial Fund postdoctoral fellow in Liu’s laboratory, and is now head of the prime editing platform.

The technology behind Prime Medicine was first disclosed publicly in October 2019, when Liu and colleagues at the Broad Institute of MIT and Harvard published a paper in Nature that laid out a new mechanism for genome editing called “prime editing” that did not make double-strand breaks in the target sequence or use a donor DNA template.

“This is the beginning of an aspiration to make any DNA change in any position of a living cell or organism,” Liu told GEN at the time. Liu is the Richard Merkin professor, director of the Merkin Institute of Transformative Technologies in Healthcare, core institute member, and vice chair of the faculty at the Broad Institute, as well as the Thomas Dudley Cabot professor of the natural sciences at Harvard University, and a Howard Hughes Medical Institute investigator.

J.P. Morgan, Goldman Sachs, Morgan Stanley, and Jefferies are acting as joint book-running managers for the IPO.

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