A LYSA Phase lb Study of Tazemetostat (EPZ-6438) plus R-CHOP in Patients with Newly Diagnosed Diffuse Large B-Cell Lymphoma (DLBCL) with Poor Prognosis Features

Purpose: The histone-methyl transferase EZH2, catalytic subunit of the PRC2 complex involved in transcriptional regulation, is mutated in approximately 25% of germinal center B-cell lymphomas. Aberrant proliferative dependency on EZH2 activity can be targeted by the orally available EZH2 inhibitor tazemetostat (EPZ-6438). We report the results of the phase lb tazemetostat plus R-CHOP combination (NCT02889523), in patients 60 to 80 years of age with newly diagnosed diffuse large B-cell lymphoma. Patients and Methods: The primary objective of this dose-escalation study was to evaluate the safety of the combination and to determine the recommended phase II dose (RP2D) of tazemetostat. Results: A total of 17 patients were enrolled. During C1 and C2, two dose-limiting toxicities were observed: one grade 3 constipation at 400 mg and one grade 5 pulmonary infection at 800 mg. Grade 3 or more toxicities observed in more than 10% of the patients were constipation (24%), nausea (12%), and hypokalemia (12%). Grade 3 to 4 hematologic adverse events were recorded in 8 patients (47%): neutropenia (47%), leukopenia (29%), anemia (18%), and thrombocytopenia (12%). The tazemetostat RP2D was 800 mg. No organ-oriented toxicity increased with tazemetostat dosage escalation (severity and incidence). At 800 mg, AUC and C-max of tazemetostat were similar compared with the single-agent study (E7438-G000-101). Conclusions: The RP2D of tazemetostat combined with R-CHOP is 800 mg twice a day. The association presents safety and PK comparable with R-CHOP alone. Preliminary efficacy data are encouraging and further investigations in phase II trial are warranted.