A Matching-Adjusted Indirect Comparison of Single-Arm Trials in Patients with Relapsed or Refractory Follicular Lymphoma Who Received at Least Two Prior Systemic Treatments: Tazemetostat was Associated with a Lower Risk for Safety Outcomes Versus the PI3-Kinase Inhibitors Idelalisib, Duvelisib, Copanlisib, and Umbralisib.

INTRODUCTION: Tazemetostat is an enhancer of zeste homolog 2 (EZH2) inhibitor recommended for patients with relapsed/refractory (R/R) follicular lymphoma (FL) after demonstrating single-agent, antitumor activity in patients with wild-type or mutant EZH2. The phosphoinositide 3-kinase (PI3K) inhibitors idelalisib, copanlisib, umbralisib and (formerly) duvelisib are indicated for third-line, fourth-line, and later (3L/4L+) treatment of R/R FL. The objective of this analysis was to provide an indirect treatment comparison of tazemetostat with each PI3K inhibitor for 3L/4L+ R/R FL treatment. METHODS: A systematic literature review was conducted to identify trials for idelalisib (DELTA), duvelisib (DYNAMO), copanlisib (CHRONOS-1 Part B), and umbralisib (UNITY-NHL) in 3L+ R/R FL. Matching-adjusted indirect comparisons were conducted by weighting tazemetostat individual patient data with available baseline characteristics from each comparator trial: age, Eastern Cooperative Oncology Group performance status, disease stage, histology, prior treatment lines, prior stem cell therapy, progression within 24 months, and refractory status to last therapy. Only the tazemetostat trial included patients with grade 3b or transformed FL, or recorded EZH2 mutation status. Primary safety outcomes included risk of grade ≥ 3 treatment-emergent adverse events (TEAEs); primary efficacy outcomes included objective response rate (ORR). RESULTS: Matched patients treated with tazemetostat had lower relative risk (RR) for all grouped safety outcomes, including any grade ≥ 3 TEAEs, compared with idelalisib (RR = 0.45), duvelisib (RR = 0.35), copanlisib (RR = 0.37), and umbralisib (RR = 0.65; all, p < 0.01), any serious TEAE, and any TEAE leading to dose reduction, drug discontinuation, or interruption. The ORR was not significantly different for tazemetostat versus other treatments (idelalisib 43% vs 56%, p = 0.16; duvelisib 48% vs 47%, p = 0.91; copanlisib 49% vs 61%, p = 0.11; and umbralisib 57% vs 47%, p = 0.10). CONCLUSIONS: In this statistically adjusted comparison, tazemetostat was associated with lower RR for safety outcomes versus idelalisib, duvelisib, copanlisib, and umbralisib, while achieving similar efficacy outcomes.

Tazemetostat for patients with relapsed or refractory follicular lymphoma: an open-label, single-arm, multicentre, phase 2 trial.

BACKGROUND: Activating mutations of EZH2, an epigenetic regulator, are present in approximately 20% of patients with follicular lymphoma. We investigated the activity and safety of tazemetostat, a first-in-class, oral EZH2 inhibitor, in patients with follicular lymphoma. METHODS: This study was an open-label, single-arm, phase 2 trial done at 38 clinics or hospitals in France, the UK, Australia, Canada, Poland, Italy, Ukraine, Germany, and the USA. Eligible patients were adults (≥18 years) with histologically confirmed follicular lymphoma (grade 1, 2, 3a, or 3b) that had relapsed or was refractory to two or more systemic therapies, had an Eastern Cooperative Oncology Group performance status of 0-2, and had sufficient tumour tissue for central testing of EZH2 mutation status. Patients were categorised by EZH2 status: mutant (EZH2mut) or wild-type (EZH2WT). Patients received 800 mg of tazemetostat orally twice per day in continuous 28-day cycles. The primary endpoint was objective response rate based on the 2007 International Working Group criteria for non-Hodgkin lymphoma, assessed by an independent radiology committee. Activity and safety analyses were done in patients who received one dose or more of tazemetostat. This study is registered with ClinicalTrials.gov, NCT01897571, and follow-up is ongoing. FINDINGS: Between July 9, 2015, and May 24, 2019, 99 patients (45 in the EZH2mut cohort and 54 in the EZH2WT cohort) were enrolled in the study. At data cutoff for the analysis (Aug 9, 2019), the median follow-up was 22·0 months (IQR 12·0-26·7) for the EZH2mut cohort and 35·9 months (24·9-40·5) for the EZH2WT cohort. The objective response rate was 69% (95% CI 53-82; 31 of 45 patients) in the EZH2mut cohort and 35% (23-49; 19 of 54 patients) in the EZH2WT cohort. Median duration of response was 10·9 months (95% CI 7·2-not estimable [NE]) in the EZH2mut cohort and 13·0 months (5·6-NE) in the EZH2WT cohort; median progression-free survival was 13·8 months (10·7-22·0) and 11·1 months (3·7-14·6). Among all 99 patients, treatment-related grade 3 or worse adverse events included thrombocytopenia (three [3%]), neutropenia (three [3%]), and anaemia (two [2%]). Serious treatment-related adverse events were reported in four (4%) of 99 patients. There were no treatment-related deaths. INTERPRETATION: Tazemetostat monotherapy showed clinically meaningful, durable responses and was generally well tolerated in heavily pretreated patients with relapsed or refractory follicular lymphoma. Tazemetostat is a novel treatment for patients with follicular lymphoma. FUNDING: Epizyme.