Researchers at City of Hope and collaborators have pioneered a new approach to preventing dangerous bloodstream infections in patients receiving donor stem cell transplants for blood cancers. The first-of-its-kind therapy delivers 16 carefully selected beneficial bacteria designed to restore the microbiome and fight harmful pathogens.

In the multicenter phase 1 clinical trial, scientists from City of Hope, Memorial Sloan Kettering Cancer Center and Seres Therapeutics found that the new therapy, called SER-155, was well tolerated with no treatment-related side effects. Patients who received the therapy also had fewer bloodstream infections and lower levels of harmful bacteria linked to infection.

The Seres Therapeutics–sponsored study, published in Nature Medicine, provides early evidence that live biotherapeutics—medicines made from beneficial bacteria—can be safely delivered to highly vulnerable patients and may help prevent serious infections, said senior author Marcel van den Brink, M.D., Ph.D., City of Hope chief physician executive and the Morgan and Helen Chu Presidential Chair of City of Hope National Medical Center.