Subcutaneous Omacetaxine Mepesuccinate in Patients With Chronic-Phase Chronic Myeloid Leukemia Previously Treated With 2 or More Tyrosine Kinase Inhibitors Including Imatinib

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Abstract

This analysis evaluated the protein synthesis inhibitor omacetaxine mepesuccinate (“omacetaxine”) in previously treated patients with chronic myeloid leukemia (CML). Patients with chronic-phase CML who had resistance or intolerance to 2 or more tyrosine kinase inhibitors were included (n = 81). Omacetaxine produced clinically meaningful responses with acceptable tolerability. These results support omacetaxine as a treatment option in this patient population.

Introduction

Omacetaxine mepesuccinate (omacetaxine) is a first-in-class cephalotaxine that has demonstrated efficacy in CML. In this analysis we evaluated omacetaxine in CML patients with resistance or intolerance to 2 or more tyrosine kinase inhibitors (TKIs).

Patients and Methods

Data were pooled from 2 phase II trials of subcutaneous omacetaxine, administered at 1.25 mg/m2 twice daily for 14 consecutive days every 28 days until response, then for 7 days every 28 days as maintenance. Patients with resistance or intolerance to imatinib and at least 1 other approved TKI (dasatinib and/or nilotinib) were included; results for patients in chronic phase (CP) are reported here. Major cytogenetic response (MCyR) was the primary end point.

Results

Eighty-one patients with CML-CP (median age, 59 years; range, 26-83 years) were included in the analysis. All patients previously received imatinib, 69 (85%) previously received dasatinib, and 48 (59%) previously received nilotinib. Median omacetaxine exposure was 7.5 months (range, 0.03-38.6 months), with 13 patients ongoing. MCyR was reported in 16 patients (20%; one-sided 95% lower confidence limit, 12.8%), including 8 complete responses; median duration was 17.7 months (95% confidence interval, 4.1 months – not reached). Fifty-six patients (69%) achieved and/or maintained hematologic response for at least 8 weeks; median duration was 12.2 months (range, 8.4-26.2 months). Median failure-free and overall survival were 9.6 months and 34 months, respectively. Toxicity was mainly hematologic: the most common grade 3/4 adverse events were thrombocytopenia (67%), neutropenia (47%), and anemia (37%).

Conclusion

Omacetaxine produced clinically meaningful responses with acceptable tolerability in patients with CML-CP previously treated with 2 or more TKIs.

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