Seres Therapeutics (MCRB) said Wednesday that top-line results from a phase 1 clinical trial of SER-155 to treat patients with immune checkpoint inhibitor-related enterocolitis met its primary endpoint.

The primary endpoint was defined as at least a 1-grade improvement in diarrhea symptoms without immunosuppressive therapy, such as a corticosteroid and/or a biologic immunomodulator drug.

Inhibitor-related enterocolitis, or irEC, is a frequent side effect of immune checkpoint inhibitors that often causes patients to halt cancer treatment.

"Patients receiving ICI treatment who develop irEC face significant challenges, as current management often necessitates interruption or discontinuation of checkpoint inhibitor therapy and treatment with systemic immunosuppressives, which are associated with clinically significant side effects," Principal Investigator David Faleck said in a statement.

Shares of Seres Therapeutics were up more than 6% pre-bell.