Beam Therapeutics Closes Series B Financing Worth $135 Million

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Cambridge, Mass.-based Beam Therapeutics completed a $135 million Series B financing. The participants included new investors Redmile Group, Cormorant Asset Management, GV, Altitude Life Science Ventures, and undisclosed investors. Existing investors participating including F-Prime Capital, ARCH Venture Partners, Eight Roads Ventures, and Omega Funds.

Beam Therapeutics is one of BioSpace’s NextGen Bio “Class of 2019” Life Science Startups to Watch in 2019. Launched in 2018 with $87 million in cumulative Series A funding, the company focuses on multiple DNA base editor platforms. They were developed in the laboratory of David Liu and the RNA base editor platform was developed by Feng Zhang at the Broad Institute of MIT and Harvard.

This technology is essentially a more precise form of CRISPR gene editing. CRISPR-Cas9 cuts DNA at specific locations, which allows researchers to insert or remove a chunk of DNA. But many diseases are caused by point mutations, changes in a single base. CRISPR-Cas9 is not precise enough to do this.

But the base editing technology of Beam Therapeutics is. It is made up of two key enzymes, one that zeroes in on a specific site in the gnome and an editing enzyme that changes a base, for example, from an “A” to a “G.”

“Since the launch of Beam last year, we have made significant progress toward our goal of developing base editors as a new class of precision genetic medicines,” stated John Evans, Beam’s chief executive officer. “We now have 10 active programs underway and have expanded our team to more than 70 employees. We are thrilled to have the support and partnership from this group of world-class investors to help us achieve our mission.”

Proceeds from the financing will be used to expand its development of CRISPR tech, expand its pipeline and “further extend its scientific and technical leadership,” which sounds like it plans to hire some scientists.

At the moment, all of the company’s programs are in the preclinical stage and have not yet begun testing the technology in laboratory animals. Evans told Xconomy that this year Beam plans to move beyond just cell-based studies of base editors “to making these things into medicines.”

Just last week, two studies were published describing concerns over off-target edits in base editing platforms. This is an area of much concern in standard CRISPR-Cas9. Point mutations are found all throughout the genome, and as such, it is difficult to evaluate whether base editors made only the changes they were intended to.

Both research studies, one in mice and another in rice, found that an adenine base editor, which transforms AT nucleotide pairs into GC nucleotide pairs, had almost no off-target edits. But the cytosine base editor, which changes CG pairs into TA pairs, changed about one nucleotide in 20 million off target. That amounts to about 150 off-target edits in the mouse genome, which has about the same number of nucleotides as humans.

Although that is of concern, it’s not clear how much. DNA mutates constantly as the result of background radiation, environmental factors and random mistakes. The natural rate of mutation can be as high as 1 in 1 million. The body has repair mechanisms, and many errors don’t have major effects. But when they do, they can lead to cancer or any number of other diseases.

Liu recently told STAT, “One in 20 million is in that range.” So it’s possible it might “have little or no impact” on patients who might undergo base editing procedures.

Evans told Xconomy the articles were mostly good news, because about half of point mutations associated with disease can be fixed by the adenine base editor, which is a major part of Beam’s pipeline, and in the studies showed few if any off-target edits. He also said the research provided the company with clues on how to improve the cytosine base editor.

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