Genexine, Inc. and NeoImmuneTech, Inc. announced the release of data for the dose escalation (DE) phase (Ph1b) of their Ph1b/2 study of GX-I7/NT-I7 (efineptakin alfa), a novel T cell amplifier, in combination with KEYTRUDA® (pembrolizumab), a leading checkpoint inhibitor (CPI), for the treatment of heavily pretreated patients with relapsed or refractory triple-negative breast cancer (TNBC). These data were shared in a poster presentation at the Society for Immunotherapy of Cancer (SITC) conference on November 9, 2020. The primary objectives of the DE phase of this study are to evaluate safety and tolerability of GX-I7/NT-I7 in combination with pembrolizumab and to determine the recommended phase 2 dose (RP2D).

Two combination schedules of GX-I7/NT-I7 and pembrolizumab were evaluated: 1. Sequential administration of pembrolizumab + GX-I7/NT-I7, after cyclophosphamide (CPA) chemotherapy pre-treatment, and 2. Concurrent administration of pembrolizumab + GX-I7/NT-I7, without CPA chemotherapy pre-treatment. As of September 30, 2020, a total of 60 patients have been enrolled and treated in the DE phase of the study. Based on the encouraging efficacy and safety data, the standard dose of pembrolizumab plus 1,200 ug/kg GX-I7/NT-I7 concurrent administration without CPA chemotherapy pre-treatment has been selected as the RP2D.

At this level, an objective response rate (ORR) of 28% has been observed. Both combination schedules were well tolerated, and the most common treatment-related AEs were injection site reaction (n=44, 73.4%), rash (n=26, 43.4%), pyrexia (n=21, 35.0%), ALT/AST increase (n=19, 31.7%), GGT increase (n=12, 20.0%), myalgia (n=12, 20.0%) and nausea (n=11, 18.4%). GX-I7/NT-I7 was dosed up to 1,440ug/kg, however this level was not selected due to one dose-limiting toxicity observed with no additional clinical benefit noted.