Gro Biosciences raises $25 million to make protein therapies from genetically recoded organisms

Humans, like most living organisms, rely on just 20 amino acids to make the thousands of different proteins found in our bodies. Scientists at Gro Biosciences find that number of building blocks limiting. The Boston-based startup has raised $25 million in series A financing to develop protein therapies by expanding the palette to 21 amino acids, and maybe more.

Gro was founded in 2016 based on work from George Church’s lab at Harvard Medical School, where scientists have created novel strains of bacteria dubbed genetically recoded organisms.

The bacteria are rewired so that a particular codon—a trio of nucleotides in DNA or RNA—directs the cell’s protein-making machinery to add a synthetic amino acid to a protein, rather than one of the standard 20 amino acids.

After several years of quietly ironing out the kinks in the engineered microbes, Gro has attracted a group of investors, including Leaps by Bayer and Redmile Group, that are interested in the startup’s unique strategy for making proteins with structures and functions not found in nature.

Gro has two applications of its genetically recoded organisms. The first one, called DuraLogic, uses a non-standard amino acid to bolster a therapeutic protein’s stability and help it last longer in the body, CEO and cofounder Daniel Mandell says.

The second application, called ProGly for “programmable glycosylation,” creates proteins decorated with sugars at precise locations, something that current protein production systems can’t do, Mandell says. The immune system recognizes sugar patterns on protein surfaces to determine if a protein is foreign, so controlling this pattern could help make protein therapies safer, he adds.

Gro also says its ProGly program could lead to a new approach for treating autoimmune diseases, which arise when our immune systems mistakenly categorize a human protein as foreign. Mandell says Gro is creating proteins with specific sugar patterns that can “reeducate the immune system” by switching immune cells to a “tolerogenic state” that will stop the autoimmune reactions.

Although the start-up isn’t disclosing specific diseases or proteins that its working on, Mandell says Gro already has protein therapies in preclinical testing, and he hopes to have a candidate ready for clinical testing in 2024.