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

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 Ib tazemetostat plus R-CHOP combination (NCT02889523), in patients 60 to 80 years of age with newly diagnosed diffuse large B-cell lymphoma.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.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 Cmax of tazemetostat were similar compared with the single-agent study (E7438-G000-101).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.