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.