After spending a couple of years in stealth mode, Cambridge, MA-based gene editing startup Prime Medicine has finally emerged on the scene. On July 13th, the company announced its launch on the back of a solid $315 million funding pumped in by some well-known investors who are betting on the potential of prime editing.
The total capital includes a Series A worth $115 million funded by ARCH Venture Partners, F-Prime Capital, GV, and Newpath Partners, who also participated in the Series B financing of $200 million in April 2021. Other Series B investors include Casdin Capital, Cormorant Asset Management, Moore Strategic Ventures, Public Sector Pension Investment Board (PSP Investments), Redmile Group, Samsara BioCapital, funds, and accounts advised by T. Rowe Price Associates, Inc., and several additional, unnamed life sciences investment funds.
Prime Editing: CRISPR 2.0
Prime editing is an improvement of the traditional CRISPR and the much more recent, base editing technologies. Developed by scientific founders David R. Liu and Andrew Anzalone at the Broad Institute of MIT and Harvard, Prime editing was soon recognized as a technological advance overcoming the limitations of existing gene editing approaches.
The prime editing toolbox consists of:
- A prime editor protein that harbors a Cas nickase domain and a reverse transcriptase domain, and
- A prime editing guide RNA (pegRNA) that carries both a targeting sequence and a template for a replacement sequence.
In principle, it functions as a ‘search and replace’ technique, locating the target sequence using a primer RNA sequence and then replacing a mutant sequence with a healthy copy by virtue of the reverse transcriptase property of editor protein. This way, the tech can be used to edit out disease-causing gene mutations at their precise location without leading to double-strand DNA breaks and the ensuing undesired changes.
“Prime Editing is a wonderful example of the revolution in genetic medicine that we are living through,” said Robert Nelsen, co-founder and Managing Director of ARCH Venture Partners. “When mature, gene editing technologies like this could totally change our conception of what’s possible in treating disease.”
The company aims to utilize the funds to enhance the promise of prime editing further and build infrastructure and workforce to rapidly advance products to the market. It is currently advancing multiple drug discovery programs targeting the liver, eye, ex-vivo hematopoietic stem cell, and neuro-muscular indications.
Potential “One and done” Treatment Approach
Acting as a DNA word processor, prime editing can repair more than 90 percent of known disease-causing mutations. It works in a variety of dividing and non-dividing primary human cells, as well as in animals. Since it doesn’t rely on non-homologous end joining or homology directed repair to fix the break, it is much more efficient than conventional CRISPR technology. Therefore, the tech minimizes off-target effects by editing at precise locations with minimal or no editing in other parts of the genome.
Additionally, it can edit four single-base transition mutations targeted by base editors along with all the eight possible single-base transversion mutations (purine to pyrimidine or vice versa), as well as precisely targeted insertions and deletions, thereby providing greater target flexibility.
“Prime Editing is a transformative technology that we believe will make a significant impact by addressing the fundamental causes of genetic disease,” said Keith Gottesdiener, MD, CEO of Prime Medicine. “Since Prime began operations in the summer of 2020, we have continued to make great progress in advancing the performance of Prime Editing, which allowed us to close our Series B financing nine months later. We are operating from a position of financial strength and look forward to further developing the technology and progressing our preclinical programs toward the clinic, with the hope that they may cure or halt the progression of genetic diseases for patients.”
Both Prime Medicine and Beam Therapeutics spun out from the lab of Dr. David R. Liu. Both companies have formed a strategic partnership to jointly develop therapies for genetic diseases by sharing research, expertise and intellectual property for assays.
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