S112: Tisagenlecleucel in Pediatric and Young Adult Patients (Pts) With Relapsed/Refractory (R/R) B-Cell Acute Lymphoblastic Leukemia (B-All): Final Analyses From the Eliana Study

Background: Pediatric and young adult pts with R/R B-ALL experience a treatment journey characterized by diminishing likelihood of cure and increasing morbidity. Tisagenlecleucel is an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy approved for use in pediatric and young adults with B-ALL and adults with B-cell lymphomas. Tisagenlecleucel provided high rates of remission (>80%) in children and young adults with R/R B-ALL in ELIANA, with 62% of responders remaining relapse-free at 24 mo (Grupp et al, Blood, 2018). Aims: Here, we report the final efficacy and safety analyses in pts followed up to 5.9 years post-tisagenlecleucel infusion. Methods: ELIANA (NCT02435849) was a pivotal, Phase II, open-label, multicenter, global study of tisagenlecleucel in pediatric and young adult pts with R/R B-ALL. Pts received a single infusion of tisagenlecleucel at 0.2-5.0×106 CAR+ viable T cells/kg body weight for pts ≤50 kg and 0.1-2.5×108 CAR+ viable T cells for pts >50 kg. Endpoints included overall remission rate (ORR) within 3 mo, relapse-free survival (RFS), duration of remission (DOR), overall survival (OS), persistence of B-cell aplasia, and short- and long-term safety events. Results:Results: As of September 24, 2021, 97 pts were enrolled and 79 pts (81%) received tisagenlecleucel. Median time from infusion to data cutoff was 5.5 y; 64 pts had ≥5 y of follow-up. At study entry, the median age was 11 y (range, 3-24). Pts were heavily pretreated with a median of 3 prior lines of therapy (range, 1-8) and 61% had a history of prior stem cell transplant (SCT). ORR (complete remission CR or CR with incomplete hematologic recovery within 3 mo after infusion) was 82% (95% CI, 72-90). Among pts in remission (CR/CRi), the 5y RFS rate was 49% (95% CI, 34-62), and the median RFS was not reached (Figure, 46.8 mo when censoring for SCT; n=15). The median time to B-cell recovery was 38.6 mo (95% CI, 23-not reached) and the probability of B-cell aplasia at 6 mo and 12 mo was 83% (95% CI, 71-91) and 71% (95% CI, 57-82), respectively. Pts with B-cell recovery (12 mo, n=7) experienced a 2y cumulative incidence of relapse of 25.2% (with SCT treated as a competing risk). Among all pts, the 5y EFS and OS rates were 42% (95%CI, 29-54) and 55% (95% CI, 43-66), respectively. There were no significant differences in any efficacy endpoint between pediatric (1 y post-infusion were infection (20%) and cytopenias (6%). Ten (14%) pts in remission experienced long-term cytopenias persisting for >1 y; however, none of these pts experienced cytopenias persisting for >5 y (median 2 y; range, 1.1-5y). Eighty-two percent of pts received IVIG any time post-infusion. Image:Summary/Conclusion: This >5 y follow-up study demonstrates continued durable efficacy of tisagenlecleucel without late adverse effects in heavily pretreated pediatric and young adult pts with R/R B-ALL. Tisagenlecleucel continues to be a potentially curative treatment option for pediatric and young adult patients with R/R B-ALL.