The U.S. Food and Drug Administration (FDA) has granted full approval to omacetaxine mepesuccinate (Synribo) for injection. The full approval was based on the final analysis of two phase II trials that evaluated the efficacy and tolerability data of omacetaxine. The agent received an accelerated approval in October 2012 for adult patients with chronic-phase or accelerated-phase chronic myeloid leukemia (CML) with resistance or intolerance to two or more tyrosine kinase inhibitors.

Phase II Studies

The original approval of omacetaxine mepesuccinate was based on an analysis of combined data subsets from two phase II, open-label, multicenter studies. The pooled analysis included patients who had received two or more approved tyrosine kinase inhibitors and, at a minimum, had evidence of resistance or intolerance to dasatinib (Sprycel) and/or nilotinib (Tasigna). Treatment with imatinib (Gleevec), dasatinib, and nilotinib had failed in 47% of chronic-phase patients and 63% of accelerated-phase patients; the majority of patients had also received other treatments including hydroxyurea, interferon, and cytarabine.

For chronic-phase CML, 18% of patients achieved a major cytogenetic response with a mean time to major cytogenetic response onset of 3.5 months. The median duration of response for these patients was 12.5 months. For accelerated-phase CML, 14% of patients achieved a major hematologic response, with a mean time to response onset of 2.3 months. The median duration of major hematologic response for these patients was 4.7 months.

The most common adverse reactions in chronic- and accelerated-phase patients were thrombocytopenia, anemia, neutropenia, diarrhea, nausea, fatigue, asthenia, injection site reaction, pyrexia, infection, and lymphopenia. ■