Scientists in lab with DNA on the computer screen
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In addition to the 10 publicly owned companies shown in this A-List’s main text, there are 5 privately held companies listed here. The privately held companies have been ranked by total capital raised as confirmed by the companies, or as reported by PitchBook (for companies that had not replied to GEN queries at deadline).

It’s a testament to the confidence in gene editing therapy developers shared by venture capital investors that the next five private companies below the top five raised nearly $1 billion in combined capital ($874 million, to be precise). Ranked 6th to 10th were Tome Biosciences ($213 million); Aera Therapeutics ($193 million); EdiGene (RMB 1.182 billion [$164 million]); Tune Therapeutics ($160 million); and SparingVision (€135 million [$144 million]).

1. Tessera Therapeutics
Tessera Therapeutics, a Flagship Pioneering company, has raised approximately $600 million toward developing genetic medicines. Tessera’s Gene Writing technology uses mobile elements called non–long nonterminal repeat retrotransposons, which write genes into the genome through a method that entails binding RNA, binding DNA, nicking DNA, and then priming reverse transcription. “We were surprised to discover that almost no one had thought about how they could be adapted as tools for genome engineering,” Tessera’s co-founder and chief innovation officer Jacob (Jake) Rubens, PhD, told GEN in 2022. Last October, the Galien Foundation awarded its Prix Galien USA 2023 to Somerville,
MA-based Tessera in the Best Startup category.

2. Mammoth Biosciences
Mammoth Biosciences’ CRISPR-based ultracompact gene editing platform has helped it raise $465 million—about $365 million in venture capital and $100 million-plus in equity and nondilutive capital—as well as interest from biopharma partners such as Bayer and Vertex Pharmaceuticals. Regeneron Pharmaceuticals joined them in April, agreeing to combine its delivery antibodies with Mammoth’s platform to develop CRISPR-based gene edited therapies. Regeneron is paying Brisbane,
CA-based Mammoth a $95 million equity investment and a $5 million upfront payment, plus up to $370 million in milestone payments per target developed. Mammoth’s co-founders include CRISPR pioneer and Nobel laureate Jennifer Doudna, PhD.

3. Arbor Biotechnologies
Arbor Biotechnologies expanded its toolbox of novel, next-generation editors on May 8 by acquiring Serendipity Biosciences. Arbor, which has raised $335 million, said the deal expands its potential therapeutic applications in reverse transcriptase–based editing and insertion of large DNA regions. Serendipity’s editing technologies were discovered in the laboratory of Arbor co-founder and CRISPR pioneer Feng Zhang, PhD. Cambridge, MA-based Arbor’s pipeline includes five wholly owned preclinical treatments for liver and central nervous system disorders. On May 9, at the American Society of Gene and Cell Therapy annual meeting, Arbor presented data supporting clinical development of its lead candidate, ABO-101, a therapy for primary hyperoxaluria type 1.

4. Scribe Therapeutics
Scribe Therapeutics has attracted $120 million in venture capital and $140 million in upfront payments from biopharma partners that include Prevail Therapeutics (an Eli Lilly and Company subsidiary), Biogen, and Sanofi. Headquartered in Alameda, CA, Scribe develops CRISPR-based treatments through genetic modification platforms designed to build and apply the company’s suite of CRISPR technologies in hematopoietic disorders and other therapeutic areas, including neurodegenerative diseases; ophthalmological diseases; and multisystem, muscle, and metabolic disorders. Scribe’s co-founders include CRISPR pioneer and Nobel laureate Jennifer
Doudna, PhD.

5. Chroma Medicine
Chroma Medicine has raised $257 million in capital toward developing programmable epigenetic editors that precisely turn genes on or off, or that can alter the expression of several genes at once. By seamlessly silencing, activating, and multiplexing genes in a single platform intended to mimic the cell’s innate mechanisms for controlling gene expression, Boston-based Chroma’s epigenetic technology can become a leading approach for gene regulation. A Chroma co-sponsored study (Cappelluti et al. Nature 2024; 627:416–423) showed that lipid nanoparticle delivery of the company’s engineered transcriptional repressors (editor-encoding mRNAs) to the liver of mice led to epigenetic silencing of the Pcsk9 gene for nearly one year.

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