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A fixed dose regimen for tyrosine kinase inhibitors (TKIs) is postulated to be responsible for variable safety outcomes in the treatment of chronic myelogenous leukemia (CML). The objective of this study was to explore an optimal dosing regimen for a TKI, radotinib, to improve its safety profile. Clinical data were obtained from a Phase 2 study of fixed-dose radotinib in 77 Asian patients with CML. The magnitude of radotinib dose adjusted for patient’s body weight (Dose/BW) and the probability of dose-limiting toxicity (DLT) demonstrated a positive association (Logit[P] = 0.86*[Dose/BW]-4.45,p = 0.001). There was a significant difference in the Kaplan-Meier curves for time to first DLT between the patient subgroups of Dose/BW <6 and ≥6 mg/kg (259versus83 days). Consequently, a two-tier weight-based dosing regimen may improve the safety of radotinib: 300 mg or 400 mg twice daily for patients weighing ≤65 or >65 kg, respectively. [ABSTRACT FROM AUTHOR]

Radotinib (IY5511HCL), a novel and selective BCR-ABL1 tyrosine kinase inhibitor, has shown pre-clinical and phase I activity and safety in chronic myeloid leukemia. This phase II study investigated the efficacy and safety of radotinib in Philadelphia chromosome-positive chronic phase-chronic myeloid leukemia patients with resistance and/or intolerance to BCR-ABL1 tyrosine kinase inhibitors. Patients received radotinib 400 mg twice daily for 12 cycles based on results from the phase I trial. The primary end point was rate of major cytogenetic response by 12 months. A total of 77 patients were enrolled. Major cytogenetic response was achieved in 50 (65%; cumulative 75%) patients, including 36 (47%) patients with complete cytogenetic response by 12 months. Median time to major cytogenetic response and complete cytogenetic response were 85 days and 256 days, respectively. Major cytogenetic response and complete cytogenetic response rates were similar between imatinib-resistant and imatinib-intolerant patients, but were higher in patients without BCR-ABL1 mutations. Overall and progression-free survival rates at 12 months were 96.1% and 86.3%, respectively. All newly-occurring or worsening grade 3/4 hematologic abnormalities included thrombocytopenia (24.7%) and anemia (5.2%); grade 3/4 drug-related non-hematologic adverse events included fatigue (3.9%), asthenia (3.9%), and nausea (2.6%). The most common biochemistry abnormality was hyperbilirubinemia (grade 3/4 23.4%), and 12 of 18 cases were managed with dose modification. Study findings suggest radotinib is effective and well tolerated in chronic phase-chronic myeloid leukemia patients with resistance and/or intolerance to BCR-ABL1 tyrosine kinase inhibitors and may represent a promising alternative for these patients. (clinicaltrials.gov identifier: 01602952)., (Copyright© Ferrata Storti Foundation.)