Synribo Approved for CML

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 that usually affects older adults.

Each year in the United States, approximately 5,000 people are diagnosed with CML. Most cases of CML are characterized by a chromosomal abnormality—the Philadelphia chromosome—in which genetic material is exchanged between chromosome 9 and chromosome 22. This exchange brings together two genes: BCRand ABL. The combination of these two genes into the single BCR-ABL gene results in the production of a protein that contributes to uncontrolled cell growth.

Synribo is a targeted agent designed to block or inhibit certain proteins that contribute to uncontrolled cell growth. It is injected under the skin twice daily for 14 consecutive days over a 28-day cycle until white blood cell counts normalize. After that, it is administered twice daily for seven consecutive days over a 28-day cycle as long as it provides clinical benefit.

Synribo is approved for use in patients whose cancer has progressed after treatment with at least two tyrosine kinase inhibitors, a type of targeted agent used to treat CML. The approval was based on a study of a combined cohort of patients whose cancer progressed after treatment with two or more tyrosine kinase inhibitors. For chronic phase CML, the drug’s effectiveness was based on a reduction of a percentage of cells expressing the Philadelphia chromosome. The results indicated that 14 out of 76 patients (18.4 percent) achieved a reduction in an average time of 3.5 months and the median length of the reduction was 12.5 months.

For accelerated phase CML, the drug’s effectiveness was based on the number of patients who experienced a normalization of white blood cell counts or achieved a major hematologic response (no evidence of leukemia). The results indicated that five out of 35 patients (14.3 percent) achieved a major hematologic response in an average time of 2.3 months. The median duration of response in these patients was 4.7 months.

Synribo was approved under the FDA’s accelerated approval program, which allows patients earlier access to promising drugs while the manufacturer conducts ongoing studies regarding benefit and safety. Synribo also received the FDA’s orphan drug status because it is intended to treat a rare disease or condition. It is the second drug in two months to be approved to treat CML and provides a new treatment option for patients who are resistant or intolerant to other drugs for CML.


FDA approves Synribo for chronic myelogenous leukemia [FDA News Release]. U.S. Food and Drug Administration website. Available at:

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