Blinatumomab in Children with Relapsed or Refractory B-Precursor Acute Lymphoblastic Leukemia (R/R-ALL): Final Results of 110 Patients Treated in an Expanded Access Study (RIALTO)

Introduction: The open-label, expanded access study (RIALTO) demonstrated that blinatumomab is efficacious with a manageable safety profile in children with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (R/R BCP-ALL). Blinatumomab is a BiTE® (bispecific T-cell engager) immuno-oncology therapy that activates cytotoxic T cells to kill target B cells. Here, findings from the final analysis of RIALTO are presented (NCT02187354). Methods: Enrolled in the study were children >28 days and Results: As of the data cutoff date (January 10, 2020) for the final analysis, demographics and baseline characteristics of 110 patients enrolled (median age, 8.5 years [95% CI 0.4-17.0]), 61% had For best treatment response within the first 2 cycles, results are comparable to that of the primary analysis. Among 110 patients, overall CR rate was 62.7% (n= 69). Of 98 patients with ≥5% blasts at baseline, 59% (n=58) achieved CR; of them, 79% (n=46) achieved an MRD response and 62% (n=39) proceeded to HSCT. The 2 patients with t(17;19) achieved CR with an MRD response. Of the 4 patients with germline trisomy 21 (Down syndrome), 3 achieved CR with an MRD response Among the 12 patients with Of 110 patients treated with blinatumomab, median OS (95% CI) was 14.6 (11-24.5) months with median follow-up time of 18.2 months, which increased by 1.5 months compared with that reported in the primary analysis, with 29.9% of patients still surviving at month 24. Median RFS (95% CI) remains unchanged at 8.5 months (4.7-14.0), with a median follow-up time of 11.5 months in patients who achieved CR; 38% of patients relapsed and 9% died. RFS was more favorable for patients who received HSCT post blinatumomab (70%) than for those who did not (30%) at month 12, respectively, which is consistent with the results from primary analysis. Among patients who had HSCT prior to blinatumomab (n= 45), median OS (95%) was 16.6 (7.1-NE) months vs 14.6 (10.9-24.5) months in patients without HSCT prior to blinatumomab (n= 65). Compared with the primary analysis, 5 additional patients received HSCT after achieving CR in the final analysis. Median OS among patients in CR after HSCT by MRD responders vs MRD non-responders was NE at 15-month analysis (Figure). Safety results in the final analysis were consistent with those reported in the primary analysis. Of 110 patients, 99% experienced TEAEs, with 65% being grade ≥3 (see Table 3 for details). TRAEs were reported in 74% of patients; 26% were grade ≥3 and 19% were deemed serious. Details on grade ≥3 TRAEs are shown in Table 3. The 9 fatal AEs, unrelated to blinatumomab, occurred due to relapse and progressive nature of the disease (Table 3). Conclusions: Overall, the safety and efficacy results from the final analysis are consistent with those reported in the primary analysis as no new safety signals were observed. These findings strengthen the observation that blinatumomab demonstrates durable efficacy and is a suitable treatment option in children with R/R BCP-ALL. Download : Download high-res image (544KB) Download : Download full-size image Table 1 . Disclosures Locatelli: Novartis: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Medac: Speakers Bureau; Miltenyi: Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity’s Board of Directors or advisory committees; Jazz Pharmaceeutical: Speakers Bureau; Amgen: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Zugmaier: Amgen: Current Employment, Other: Personal Fees ; 20190300609: Patents & Royalties: Licensed patient . Mergen: Amgen: Current Employment, Current equity holder in publicly-traded company. Bader: Medac: Patents & Royalties, Research Funding; Amgen: Consultancy, Speakers Bureau; Neovii: Research Funding; Celgene: Consultancy; Novartis: Consultancy, Speakers Bureau; Riemser: Research Funding. Schlegel: bluebird bio: Honoraria. Bourquin: Servier: Other: Travel Support. Handgretinger: Amgen: Honoraria. Brethon: Amgen: Other: invitation to meetings, remunerations for oral presentations, advices for the record of Blinatumomab in pediatrics in France. Rossig: Roche: Honoraria, Membership on an entity’s Board of Directors or advisory committees; BMS: Honoraria; Pfizer: Honoraria; Celgene: Membership on an entity’s Board of Directors or advisory committees; EUSA Pharma: Membership on an entity’s Board of Directors or advisory committees; Genetech: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees; Amgen: Membership on an entity’s Board of Directors or advisory committees. Kormany: Amgen: Current Employment, Current equity holder in publicly-traded company. Viswagnachar: IQVIA: Current Employment.