Isatuximab in Combination with Chemotherapy in Pediatric Patients with Relapsed/Refractory Acute Lymphoblastic Leukemia or Acute Myeloid Leukemia (ISAKIDS): Interim Analysis

Introduction: Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, representing ~25% of cancer diagnoses in children. Approximately 20% of childhood leukemias are of myeloid origin with the majority being acute. Isatuximab (Isa) is a monoclonal antibody that binds to a specific epitope of CD38 and exerts anti-multiple myeloma (MM) effects through several modes of action. Isa is approved for use in MM in adults. CD38 expression is high in some acute leukemia subsets in pediatric patients, making CD38 a potential target for acute leukemia treatment in children. Methods: ISAKIDS (NCT03860844) is a Phase 2, single-arm, multicenter, open-label study evaluating the antitumor activity, safety, and pharmacokinetics (PK) of Isa in combination with standard salvage chemotherapies in children with relapsed or refractory (R/R) leukemia in first or second relapse; including both T-ALL and B-ALL and acute myeloid leukemia (AML), conducted in 3 separate cohorts. Children from 2 years (yrs) to Results: 24 pts were enrolled (10, B-ALL; 7, T-ALL; 7, AML) and treated. Baseline characteristics were comparable between cohorts; median age (range) B-ALL 6.5 (3-14) yrs; T-ALL 10.0 (7-16) yrs; AML 7.0 (2-17) yrs. Males (4/10 B-ALL; 6/7 T-ALL; 3/7 AML). Evaluable Lansky scores of 90 - 100 (9/10 B-ALL; 3/4 T-ALL; 4/6 AML). Mean (standard deviation) time from initial diagnosis to first dose of investigational medicinal product (IMP) was 2.6 (1.0) yrs, 1.2 (0.6) yrs, and 1.0 (0.3) yrs for the B-ALL, T-ALL, and AML groups, respectively. Number of prior regimens, median (range) was 6 (1-≥8), 3 (1-≥8), 4 (1-≥8) for the B-ALL, T-ALL, and AML groups, respectively, corresponding to inclusion of pts with very advanced disease. Three pts presented with hyperleukocytosis >20 x 10 9/L. Among 23 pts assessed for CD38 expression, all except 2 (1 B-ALL and 1 AML) were CD38 positive. There were 17 evaluable pts with valid response data collected up to the cutoff date (May 11, 2021). Of the evaluable participants, CR+CRi were observed for: 3/7 (42.9%) in the B-ALL cohort, 2/6 (33.3%) in the T-ALL cohort, and 2/4 (50.0%) in the AML cohort (Table). Safety data showed that Grade ≥3 TEAEs occurred in 17 pts (Table). Infusion reactions (majority Grade 1 or 2) occurred in 9/24 pts (2/10 B-ALL; 4/7 T-ALL; 3/7 AML). Three pts had Grade 5 TEAEs (deaths: 1 B-ALL and 2 AML). One subject in the AML cohort had cytokine-release syndrome (CRS) related to IMP with progressive disease as a confounding factor. The other 2 deaths were not treatment related. One subject in the AML cohort had cellulitis Grade 5 and 1 subject in the B-ALL cohort had septic shock Grade 5 as cause of death. Preliminary PK analysis on 18 pts (>2 yrs) showed that Isa PK parameters including exposure PK parameters in children with ALL or AML are consistent with those observed in adult ALL pts. PK modeling approaches predict a slightly lower exposure ( Conclusions: In a poor prognostic relapsed population, 7/17 (41.2%) pts achieved CR+CRi. Safety profile and exposure is consistent with the available data for adults. Enrollment will be opened for pts Figure 1 Figure 1. Disclosures Baruchel: Kite/Gilead: Other: Investigator; Novartis, Servier, Celgene, Jazz, Janssen, Sanofi, Amgen,Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees, Other: Satellite symposium; Shire Servier: Research Funding. Abrahamsson: wedish Children´s Cancer Foundation. Research grants and 50% senior research position for clinical research on pediatric leukemia: Research Funding. Nysom: Bayer, Y-mAbs, EUSA Pharma: Consultancy, Honoraria. Rizzari: Sobi: Other: personal fees; Jazz Pharmaceuticals: Other: Personal fees; Amgen: Other: Personal fees; Medac: Other: Grants and personal fees; Shire: Other: Grants and personal fees. Cesaro: Sobi: Membership on an entity's Board of Directors or advisory committees; Gilead: Speakers Bureau. Duarte: Amgen: Consultancy, Other: Advisory Board; Novartis: Consultancy; Jazz Pharma: Research Funding. Kang: Amgen Korea: Membership on an entity's Board of Directors or advisory committees, Research Funding; Cartexell: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Korea: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kattamis: Agios Pharmaceuticals: Consultancy; IONIS: Consultancy; VIFOR: Consultancy; CRISPR/Vertex: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria, Research Funding; Chiesi: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy. Tøndel: Sanofi: Research Funding. Ivanina: Sanofi: Current Employment. Brillac: Sanofi: Current Employment. Wang: Sanofi: Current Employment. Oprea: Sanofi: Current Employment, Other: may have stock options . Abbadessa: Sanofi: Current Employment. Zwaan: Sanofi: Consultancy.