TOL101 is a murine IgM mAb targeting the αβ TCR. Unlike other T cell targets, the αβ TCR has no known intracellular signaling domains and may provide a nonmitogenic target for T cell inactivation. We report the 6-month Phase 2 trial data testing TOL101 in kidney transplantation. The study was designed to identify a dose that resulted in significant CD3 T cell modulation (<25 T cell/mm3), to examine the safety and tolerability of TOL101 and to obtain preliminary efficacy information. Thirty-six patients were enrolled and given 5–10 daily doses of TOL101; 33 patients completed dosing, while three discontinued after two doses due to a self-limiting urticarial rash. Infusion adjustments, antihistamines, steroids and dose escalation of TOL101 reduced the incidence of the rash. Doses of TOL101 above 28 mg resulted in prolonged CD3 modulation, with rapid recovery observed 7 days after therapy cessation. There were no cases of patient or graft loss. Few significant adverse events were reported, with one nosocomial pneumonia. There were five biopsy-confirmed acute cellular rejections (13.9%); however, no donor-specific antibodies were detected. Overall TOL101 was well-tolerated, supporting continued clinical development using the dose escalating 21–28–42–42–42 mg regimen.
This report of a 6-month Phase 2 study documents the initial safety and efficacy of the IgM T cell receptor-specific monoclonal antibody TOL 101 used as an induction agent for primary kidney transplant recipients.