STOCKHOLM—Interim trial results suggest the EZH2 inhibitor tazemetostat can produce durable responses in patients with relapsed or refractory follicular lymphoma (FL).
In patients with EZH2 mutations, the overall response rate (ORR) was 71%, and the median duration of response (DOR) was 32 weeks.
For patients with wild-type (WT) EZH2, the ORR was 33%, and the median DOR was 76 weeks.
Tazemetostat was considered generally well tolerated in this phase 2 trial, which is currently on partial clinical hold.
Gilles Salles, MD, PhD, of the University Hospital of Lyon France, presented results from the trial at the 23rd Congress of the European Hematology Association (EHA) as abstract S100.
The trial is sponsored by Epizyme, Inc.
In April, Epizyme announced that all US-based trials of tazemetostat had been placed on partial hold after a pediatric patient on a phase 1 trial developed secondary T-cell lymphoma.
Enrollment was stopped in all the trials, but patients could continue receiving tazemetostat if they had not progressed on the drug.
The phase 2 trial of tazemetostat in non-Hodgkin lymphoma has enrolled 89 adults with relapsed/refractory FL.
At EHA, Dr Salles presented results in 82 of these patients. There were 28 patients with EZH2-mutated FL and 54 with EZH2-WT FL.
The median age was 61 in both cohorts. Forty-three percent of EZH2-mutated and 63% of WT patients were male.
EZH2-mutated patients had a median of 3 prior therapies, and WT patients had a median of 4. Thirty-eight percent and 42%, respectively, were refractory to their last therapy. Eleven percent and 39%, respectively, had received prior transplant.
The median time from diagnosis was 5.1 years for EZH2-mutated patients and 6.4 years for WT patients. The median time from last prior therapy was 18.4 weeks and 28.1 weeks, respectively.
The patients received tazemetostat at 800 mg twice daily until disease progression or withdrawal.
In all 82 patients, the rate of treatment-emergent adverse events (AEs) was 95%, and the rate of treatment-related AEs was 78%. The rate of grade 3 or higher treatment-related AEs was 17%, and the rate of serious treatment-related AEs was 4%.
Six percent of patients discontinued treatment due to a related AE, 18% had a dose interruption, and 5% had a dose reduction due to a related AE.
Treatment-related AEs included nausea (20%), fatigue (13%), anemia (13%), diarrhea (11%), alopecia (11%), asthenia (10%), thrombocytopenia (10%), muscle spasms (6%), bronchitis (5%), vomiting (5%), headache (5%), abdominal pain (2%), pyrexia (1%), and cough (1%).
Grade 3 or higher treatment-related AEs included thrombocytopenia (4%), anemia (4%), fatigue (1%), and asthenia (1%).
In the EZH2-mutated cohort, the ORR was 71% (n=20). Eleven percent of patients (n=3) achieved a complete response, and 61% (n=17) had a partial response.
Twenty-nine percent (n=8) had stable disease as their best response. And 21% (n=6) of patients are still on study with stable disease.
All patients in this cohort experienced a reduction in tumor burden. None of the patients had progressive disease as their best response.
At the time of analysis (May 1, 2018), the median DOR was 32.3 weeks, and 55% of responders (n=11) had an ongoing response.
The median progression-free survival was 48.6 weeks.
In patients with WT EZH2 (n=54), the ORR was 33% (n=18). Six percent of patients (n=3) achieved a complete response, and 28% (n=15) had a partial response.
Thirty-one percent of patients (n=17) had stable disease as their best response, including 1 patient who is still receiving treatment.
Thirty-one percent of patients (n=17) progressed. For 4% (n=2), their response status was unknown.
At the time of analysis, the median DOR was 76 weeks, and 56% of responders (n=10) had an ongoing response.
The median progression-free survival was 29.9 weeks.
“I am impressed by the sustained clinical activity and the good tolerability of tazemetostat in this heavily pretreated patient population,” Dr Salles said. “This is important for patients with relapsed or refractory follicular lymphoma, as both the response rates and durations of response usually tend to decrease with each successive line of treatment.”
“I believe tazemetostat has the potential to fill a significant unmet need for these patients, and continued investigation of tazemetostat as a single agent or in combination with other agents is warranted.”
Epizyme’s president and chief executive officer, Robert Bazemore, said the company is still working to resolve the partial clinical hold on tazemetostat trials and is “making good progress.”