Trial in Progress: A Multicenter, Open-Label, Phase Ib/II Study to Determine the Dose and Safety of Asciminib in Pediatric Patients with Philadelphia Chromosome-Positive Chronic Myeloid Leukemia in Chronic Phase Treated with ≥1 Prior Tyrosine Kinase Inhibitor

BACKGROUND: Tyrosine kinase inhibitors (TKIs) are the standard of care for adult and pediatric patients (pts) with chronic myeloid leukemia in chronic phase (CML-CP). In adults, 5 TKIs are approved: imatinib, dasatinib, nilotinib, bosutinib and ponatinib. In the pediatric population, however, only imatinib, dasatinib and nilotinib are approved. Pediatric pts have similar cytogenetic and molecular response rates to first-line (1L) imatinib and 1L second-generation TKIs nilotinib and dasatinib as adults. While the safety profiles for TKIs are similar in adult and pediatric pts, growth retardation has been reported specifically in the pediatric population. Therefore, safer and more efficacious options are needed for pediatric pts. Asciminib is an investigational drug that inhibits BCR-ABL1 by specifically targeting the ABL myristoyl pocket (STAMP inhibitor). Asciminib has shown promising efficacy and safety in adults with CML-CP in phase I-III trials, given without food for 1 hour prior and 2 hours after taking asciminib (fasted). In the phase I asciminib monotherapy trial in heavily pretreated adult pts, 48% and 28% without and with T315I mutations, respectively, achieved or maintained major molecular response (MMR) by 12 months. In the phase III ASCEMBL trial for adults with CML-CP who are resistant to or intolerant of ≥2 TKIs, 25.5% of pts on asciminib vs 13.2% of pts on bosutinib achieved MMR at 24 weeks. Here we present the phase Ib/II trial evaluating asciminib monotherapy in pediatric pts.