Seres Therapeutics' SER-155 Received Breakthrough Designation for Bloodstream Infections in Stem Cell Transplant Patients
Seres Therapeutics has announced that US FDA has granted Breakthrough Therapy designation to its lead investigational product, SER-155. This designation is for reducing bloodstream infections (BSIs) in adults undergoing allogeneic hematopoietic stem cell transplants (allo-HSCT) for the treatment of blood cancers.
The Breakthrough Therapy designation is granted to drugs that show early evidence of substantial improvement in treating serious conditions. This status allows for more direct communication with the FDA, speeding up the development process. SER-155 is Seres’ second product to receive this designation, following its earlier Fast Track designation for reducing the risk of infections and graft-versus-host disease (GvHD) in allo-HSCT patients.
The FDA’s designation is supported by the Phase 1b clinical trial data, which showed that patients receiving SER-155 had significantly fewer BSIs (10% versus 42.9% in the placebo group), a shorter duration of antibiotic use (9.2 days compared to 21.1 days), and a lower incidence of febrile neutropenia. Additionally, the drug was well tolerated, with no serious adverse events and expected engraftment in the gastrointestinal tract.
BSIs are a major concern for allo-HSCT patients, as infections are a leading cause of death in the first 100 days post-transplant. Antibiotics are commonly used to manage these infections, but they do not address the underlying causes. SER-155, on the other hand, is designed to target and decolonise harmful pathogens in the gut, reducing infection risks and the need for antibiotics.
Beyond allo-HSCT, BSIs also pose a serious threat to other vulnerable patient groups, including those undergoing autologous-HSCT, cancer patients with neutropenia, CAR-T therapy recipients, individuals with chronic liver disease, solid organ transplant recipients, and patients in intensive care.
SER-155 is an investigational, oral live biotherapeutic designed to prevent bacterial bloodstream and antimicrobial-resistant (AMR) infections by decolonising harmful gut pathogens, improving gut barrier function, and promoting immune tolerance in patients undergoing allo-HSCT for blood cancer treatment. The Phase 1b study showed that SER-155 significantly reduced BSIs and antibiotic use, and reduced the incidence of febrile neutropenia. The product has received both Breakthrough Therapy and Fast Track designations from the FDA.
