No advantage of Imatinib in combination with hydroxyurea over Imatinib monotherapy: a study of the East German Study Group (OSHO) and the German CML study group.

ABSTRACT

INTRODUCTION: The combination of Imatinib (IM) and hydroxyurea (HU) was explored for the treatment of chronic myelogenous leukemia (CML). METHOD: After in vitro testing and a phase I study (n = 20), 59 patients were randomized in the IM/HU and 29 in the IM arm. According to protocol, 49 propensity-score matched IM patients were included from the CML-IV study. RESULTS: Additive specific inhibition of CML cells by IM/HU was detected in vitro. HU 500 mg qd in combination with IM 400 mg qd proved feasible in the phase I study. Overall, no significant difference with respect to major molecular response (MMR) at 18 months (IM/HU and IM 66%; primary endpoint) was observed. Significant differences were noted for MMR at 6 months (p = 0.04) and for cumulative incidences of adverse events (p = 0.03) in favor of IM monotherapy (secondary endpoints). CONCLUSION: IM/HU combination was more potent in selectively inhibiting CML cells in vitro, but not superior to IM in vivo. (NCT02480608).