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FDA Approves Synribo (Omacetaxine) for CML

Drug blocks proteins that promote development of cancerous cells (Oct. 26)

The FDA has approved Synribo (omacetaxine mepesuccinate, Teva Pharmaceuticals) for the treatment of adults with chronic myelogenous leukemia (CML).

An estimated 5,430 people will be diagnosed with CML in 2012, according to the National Institutes of Health. Synribo is intended to be used in patients whose cancer has progressed after treatment with at least two tyrosine kinase inhibitors (TKIs), also used to treat CML.

Synribo blocks proteins that promote the development of cancerous cells. It is injected subcutaneously twice daily for 14 consecutive days over a 28-day cycle until white blood cell (WBC) counts normalize. Synribo is then administered twice daily for 7 consecutive days over a 28-day cycle as long as patients continue to clinically benefit from therapy.

Synribo is the second drug approved to treat CML in the past 2 months. On September 4, the FDA approved Bosulif (bosutinib, Pfizer) to treat patients with chronic, accelerated, or blast-phase Philadelphia chromosome-positive CML who are resistant to or cannot tolerate other therapies.

Synribo was approved under the FDA’s accelerated approval program, which allows the agency to approve a drug to treat a serious disease based on clinical data showing that the drug has an effect on a surrogate endpoint that is reasonably likely to predict a clinical benefit to patients. Synribo also received orphan-drug designation by the FDA because it is intended to treat a rare disease or condition.

The effectiveness of Synribo was evaluated using a combined cohort of patients whose cancer progressed after previous treatment with two or more TKIs. All participants were treated with Synribo.

The drug’s effectiveness in chronic-phase CML was demonstrated by a reduction in the percentage of cells expressing the Philadelphia chromosome genetic mutation found in most CML patients. Fourteen of 76 patients (18.4%) achieved a reduction in mutation-expressing cells in an average period of 3.5 months. The median length of the reduction was 12.5 months.

In accelerated-phase CML, the effectiveness of Synribo was determined by the number of patients who experienced a major hematologic response (MaHR), defined as normalization of WBC counts or no evidence of leukemia. Results showed that five of 35 patients (14.3%) achieved MaHR in an average period of 2.3 months. The median duration of MaHR in these patients was 4.7 months.

The most common side effects reported during clinical studies included thrombocytopenia, anemia, neutropenia, diarrhea, nausea, weakness, fatigue, injection-site reactions, and lymphopenia.

Source: FDA, October 26, 2012.

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