Real-World Tisagenlecleucel Outcomes in Richter-Transformed Chronic Lymphocytic Leukemia: A Center for International Blood & Marrow Transplant Research (CIBMTR) Analysis

Background: Richter transformation (RT) is a rare but serious transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma, most commonly large B-cell lymphoma (LBCL). There is currently no standard therapy for RT lymphoma and median overall survival (OS) is estimated to be only 8-12 months. Tisagenlecleucel is an autologous CD19-directed chimeric antigen receptor (CAR)-T cell therapy approved for the treatment of r/r LBCL in patients who have received ≥2 lines of prior therapy. Here, we describe the efficacy and safety of tisagenlecleucel in patients with RT in a real-world setting with a median follow-up (infusion to data cutoff) of 31 months.

Methods: Data were collected as part of a noninterventional, prospective, longitudinal study using the CIBMTR registry. All patients were treated in the United States, Canada, or Israel. Efficacy outcomes analyzed included overall response rate (ORR), progression-free survival (PFS), and OS. Safety outcomes included the incidence and severity of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS).

Results: As of May 4, 2023, 48 patients with RT received a single tisagenlecleucel infusion. The median age at infusion was 68 years (range, 39-83). Fifty-eight percent of patients were ≥65 years old. The median number of all prior lines of therapy was 3 (range, 1-8); 42% of patients received ibrutinib as a prior therapy. No information confirming clonal relation of LBCL to CLL in evaluated patients was available. Fifty percent of patients had primary refractory disease. Prior to infusion, 46% of patients were reported to have elevated lactate dehydrogenase (LDH). Two patients who received tisagenlecleucel infusion, and were alive at data cutoff, had not yet reached 100 days post-infusion and were therefore not evaluable for efficacy and safety. Among the 46 patients evaluated for efficacy and safety, the ORR (complete response [CR] + partial response) was 63% (95% CI, 47.5-76.8) and CR rate was 50% (n=23). In total, 23 patients (23/46, 50%) experienced disease relapse, 17 within 6 months of infusion (Figure). Twelve- and 24-month PFS were 43% and 39%, respectively; 12- and 24-month OS rates were 51% and 44%, respectively. Among 23 patients with a best overall response of CR, 57% remained in remission at data cutoff. The most common adverse events of any grade were CRS (78%), hypogammaglobinemia (46%), and ICANS (35%). Grade 3/4 CRS was reported in 11% of patients. No patient experienced grade 5 CRS. CRS was managed with tocilizumab in 81% of cases. Grade 3 ICANS was reported in 9% of patients. No grade 4/5 ICANS events were observed. Two patients went on to receive a stem cell transplant following tisagenlecleucel infusion. In total, 25 deaths were reported. The most common cause of death was progressive disease (13/48, 27%). Twelve patients (12/48, 25%) died in the absence of disease progression. Causes of non-relapse-related mortality included infection (including COVID-19, n=5), respiratory failure (n=2), malignant neoplasm (n=2), prior malignancy (n=1), multiorgan dysfunction (n=1), and severe veno-occlusive disease (n=1).

Conclusions: In the largest cohort of patients with RT receiving treatment in a real-world setting, tisagenlecleucel resulted in a high overall response rate and durable survival. The incidences of CRS and ICANS were similar to other real-world reports of tisagenlecleucel for patients with LBCL. Overall, these findings demonstrate that tisagenlecleucel could be considered a potential treatment option for patients with RT who have a high unmet medical need.