LUGANO—The EZH2 inhibitor tazemetostat (EPZ-6438) has shown “meaningful clinical activity” as monotherapy in patients with advanced non-Hodgkin lymphoma (NHL), according to researchers.
In a phase 1 trial, 9 of the 15 evaluable NHL patients achieved an objective response to tazemetostat.
This included 2 ongoing complete responses (CRs), 1 in a patient with diffuse large B-cell lymphoma (DLBCL) and 1 in a patient with follicular lymphoma (FL).
It also included a partial response (PR) in the first treated patient with an EZH2 mutation.
And researchers said the drug was largely well-tolerated, as most adverse events were grade 1 or 2.
“The breadth, depth, and durability of responses seen in NHL patients among multiple histologies continue to impress, as does the safety and tolerability of tazemetostat in this phase 1 study,” said Vincent Ribrag, MD, of Institut Gustave Roussy in Villejuif, France.
“Among the patients in the dose-escalation cohorts, we have seen a noteworthy deepening of responses over time, and, in the first treated patient with an EZH2 tumor mutation, we have seen a partial response, which is very encouraging.”
Dr Ribrag presented these results at the 13th International Conference on Malignant Lymphoma (abstract 145*). The study, which was previously presented at the 26th EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics, was sponsored by Epizyme, Inc., the company developing tazemetostat.
The phase 1 trial has enrolled 19 patients with relapsed or refractory B-cell NHL and 26 patients with advanced solid tumors.
Researchers have evaluated 5 cohorts of patients in the dose-escalation portion of the study—100 mg, 200 mg, 400 mg, 800 mg, and 1600 mg—and 2 cohorts—800 mg and 1600 mg—in the dose-expansion phase. All doses of tazemetostat were given twice daily.
The 19 NHL patients had a median age of 61 (range, 24-84) and were heavily pretreated. Eighty-five percent had received 3 or more prior therapies, and 37% had received 5 or more prior therapies.
Thirty-seven percent of patients were refractory to their last prior regimen, and 26% had received a prior autologous hematopoietic stem cell transplant.
Dosing and efficacy
As of June 8, 2015, 15 NHL patients were evaluable for efficacy. Nine had achieved an objective response, including 2 patients with an ongoing CR. All responses were observed between 2 and 10 months on therapy.
Five of the 9 evaluable patients with DLBCL achieved an objective response. One DLBCL patient with a CR remains on study at 18 months of treatment.
Three of 5 evaluable patients with follicular lymphoma (FL) achieved an objective response. One FL patient with a CR remains on study at 13 months, and 1 FL patient with a PR remains on study at 13 months.
The only patient with marginal zone lymphoma achieved a PR and continues on study at 11 months.
One of the 14 patients evaluated for EZH2 status has a specific EZH2 tumor mutation (Y646H). This patient, who had DLBCL that relapsed or was refractory to 6 previous treatment regimens, achieved a PR after 16 weeks of therapy and remains on study.
The recommended phase 2 dose of tazemetostat is 800 mg twice daily.
Adverse events and next steps
All of the 45 enrolled patients were evaluable for safety. Treatment-related adverse events included asthenia (n=10), nausea (n=6), dyspepsia (n=5), thrombocytopenia (n=4), anorexia (n=4), anemia (n=4), vomiting (n=3), constipation (n=2), muscle spasm (n=2), hypertension (n=2), neutropenia (n=2), and elevated transaminase (n=1).
There were 5 grade 3 or higher adverse events related to treatment, including grade 3 anorexia, grade 3 hypertension, grade 3 transaminase elevation, grade 4 thrombocytopenia, and grade 4 neutropenia.
Epizyme plans to report a further update from this trial by the end of this year. The company is now enrolling patients in a phase 2 study of tazemetostat monotherapy in patients with relapsed or refractory NHL, stratified by cell of origin and EZH2 mutation status.
Epizyme is also planning a phase 2 trial of tazemetostat in adults with INI1-deficient solid tumors, a phase 1 study of pediatric patients with INI1-deficient solid tumors, a combination study of tazemetostat with R-CHOP in patients with DLBCL, and a combination study of tazemetostat with a B-cell signaling agent or other emerging targeted therapies for B-cell lymphomas.
*Information in the abstract differs from that presented at the meeting.