Lexington-based startup will target cystic fibrosis with a new twist on gene therapy

Carbon Biosciences launched with $38 million to develop gene therapies based on parvoviruses, which it hopes will be safer and more effective than existing technologies

Carbon Biosciences is developing gene therapies based on engineered parvoviruses, which cause infections in humans and animals, shown here in an illustration.Kateryna_Kon - stock.adobe.com

Gene therapy developers rely on hollowed-out viruses to shuttle DNA into the body, where it can treat or potentially even cure a genetic disease. But most of the dozens of companies in the field use just two kinds of viruses for their DNA delivery. Carbon Biosciences hopes to expand that toolbox.

The Lexington startup launched Tuesday with $38 million in series A financing to create a new class of gene therapies based on parvoviruses — a large family of viruses best known for infecting dogs, but comprised of many little-studied viruses that can infect humans and other animals, too.

Carbon president and chief executive Joel Schneider said that parvovirus-based gene therapies could lead to safer and more effective treatments than ones based on existing technologies. He also hopes that parvoviruses will be the key to making an effective gene therapy for cystic fibrosis, a longtime goal that has eluded the field for decades.

The vast majority of gene therapy firms work with adeno-associated viruses, or AAVs, which are the basis of two commercial gene therapies in the United States and hundreds of experimental treatments. But AAVs are just one small subset of the larger parvovirus family, and Carbon was founded on the belief that these other viruses have some untapped advantages.

“There are thousands of these parvoviruses, so we can begin to explore those and turn them into really promising therapeutic delivery vehicles,” Schneider said.

AAVs have a number of drawbacks, including a limited cargo capacity. Some genes are simply too big to stuff into the hollow shell of the virus, including the CFTR gene that is defective in people with cystic fibrosis and causes a dangerous buildup of mucus in the lungs. Carbon has found a parvovirus big enough to carry a healthy copy of the CFTR gene, once some of the virus’s own genes are carved out.

The company is still testing the concept in animals, but if it works in humans it could be a godsend for people with the disease. Cystic fibrosis is caused by many different mutations in CFTR. Existing pills for the condition only work for certain mutations, and there aren’t drugs for all of them. A therapy that gives lung cells a new working copy of the gene could provide a single treatment for all forms of cystic fibrosis.

Parvoviruses could help overcome some other limitations of AAV. Many people have pre-existing immunity to AAVs, precluding them from receiving gene therapies. And once a person gets a gene therapy, they will likely develop an immune response to the virus that prevents them from getting another therapy based on the same virus.

Lucy Liu, Carbon’s founding vice president of strategy and operations, said the firm is searching for parvoviruses that naturally evade the immune system, which means they could be given to a broader swath of patients initially and might even be suitable for redosing — which would help get the therapeutic gene into more cells of the lung.

Schneider said that Carbon has already successfully readministered its lead gene therapy to animals, which is based on a parvovirus found in human lungs. “We know that humans have been exposed to this virus before and can be exposed over and over again,” he said. The company isn’t disclosing how much more animal testing will be required before it’s ready to start testing the treatment in people.

Ring Therapeutics, a startup founded by Flagship Pioneering, is pursuing a similar idea in trying to develop gene therapies based on anelloviruses, a family of viruses that coexists peacefully in the human body. The startup has raised $167 million to date.

Carbon was founded and backed by Longwood Fund, a healthcare focused venture capital firm, and received funding from other investors including the Cystic Fibrosis Foundation in Lexington — which is temporarily sharing some of its lab space with Carbon until the startup moves into its own space in Waltham, hopefully before the end of the year, Schneider said.

The firm is based on the work of its scientific founders John F. Engelhardt, a cystic fibrosis and gene therapy expert from the University of Iowa, and Robert M. Kotin, a gene therapy scientist from the UMass Chan Medical School.