The U.S. Food and Drug Administration today approved Synribo (omacetaxine mepesuccinate) to treat adults with chronic myelogenous leukemia (CML), a blood and bone marrow disease.
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 progressed after treatment with at least two drugs from a class called tyrosine kinase inhibitors (TKIs), also used to treat CML.
Synribo blocks certain proteins that promote the development of cancerous cells. It is injected just under the skin (subcutaneously) twice daily for 14 consecutive days over a 28-day cycle until white blood cell counts normalize (hematologic response). Synribo is then administered twice daily for seven consecutive days over a 28-day cycle as long as patients continue to clinically benefit from therapy.
"Today's approval provides a new treatment option for patients who are resistant to or cannot tolerate other FDA-approved drugs for chronic or accelerated phases of CML," said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in FDA's Center for Drug Evaluation and Research. "Synribo is the second drug approved to treat CML in the past two months."
On Sept. 4, 2012, the FDA approved Bosulif (bosutinib) to treat patients with chronic, accelerated or blast phase Philadelphia chromosome positive CML who are resistant to or who cannot tolerate other therapies.
Synribo is 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. This program provides earlier patient access to promising new drugs while the company conducts additional clinical studies to confirm the drug's clinical benefit and safe use. Synribo also received orphan-product 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 out of 76 patients (18.4 percent) achieved a reduction in an average time of 3.5 months. The median length of the reduction was 12.5 months.
In accelerated phase CML, Synribo's effectiveness was determined by the number of patients who experienced a normalization of white blood cell counts or had no evidence of leukemia (major hematologic response, or MaHR). Results showed five out of 35 patients (14.3 percent) achieved MaHR in an average time 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 include a low level of platelets in the blood (thrombocytopenia), low red blood cell count (anemia), a decrease in infection-fighting white blood cells (neutropenia) which may lead to infection and fever (febrile neutropenia), diarrhea, nausea, weakness and fatigue, injection site reaction, and a decrease in the number of lymphocytes in the blood (lymphopenia).
Synribo is marketed by Frazer, Pa.-based Teva Pharmaceuticals. Bosulif is marketed by New York City-based Pfizer.