Third Rock- and Atlas-backed Magenta launches

Backed by $48.5 million in funding from Third Rock Ventures and Atlas Venture, Magenta Therapeutics has launched to try to make stem cell transplants safer, more effective, and potentially applicable to a broader range of patients.

By replacing sick cells with healthy ones, stem cell transplants can cure certain types of blood cancer. But they are also risky and are usually only attempted after other therapeutic options have failed.

Magenta CEO Jason Gardner breaks down the current weaknesses of stem cell transplantation into three categories: patient preparation for the procedure, stem cell harvesting, and failure of transplanted cells to grow and produce healthy cells. Magenta, with a long list of prominent stem cell biology and transplantation experts as cofounders, will go after all three areas in parallel.

For decades, patients undergoing a transplant have first endured intensive chemotherapy or total body radiation to suppress production of sick stem cells. “Instead of subjecting patients to a sledgehammer,” Gardner says, Magenta is developing targeted antibodies against some of the more than 400 antigens expressed on stem cells, allowing the cells to be selectively removed.

Magenta, which has a team of 20 that should double by late next year, is working on new approaches for quickly harvesting large amounts of healthy stem cells. It’s also exploring how new technologies can be applied to improve the properties of harvested stem cells.

Ultimately, Gardner hopes that modernizing stem cell transplant tools will broaden the number of people eligible for the procedure. In addition to the late-stage blood cancers now treated with stem cells, earlier-stage cancers, autoimmune diseases such as multiple sclerosis, and genetic blood disorders such as sickle cell anemia could also be addressed.