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Monday June 7, 2004 4:24 PM GMT


There had previously been no approved therapies for MDS. Vidaza is the first FDA approved drug for MDS.


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Myelodysplastic syndrome


The FDA announced on May 20, 2004, the approval of Vidaza injection, the first effective treatment for a rare and difficult-to-treat bone marrow disease.

Vidaza will be used to treat patients with myelodysplastic syndrome. The product was given "fast track" status and a priority review. Priority Review status of the application reduces the standard agency response time to six months.

By restoring normal growth and differentiation of bone marrow cells, this new treatment will offer a much-needed option for patients suffering from this incurable illness that, in some cases, has been found to progress to leukemia.

Myelodysplastic syndrome

Myelodysplastic syndrome is a collection of conditions in which the bone marrow does not function normally. These conditions show abnormalities in the production of one or more of the cellular components of blood (red cells, white cells (other than lymphocytes) and platelets (or their progenitor cells, megakaryocytes).

Myelodysplastic syndrome patients have an increased risk of developing acute leukaemia, which is notoriously resistant to treatment ("secondary leukaemia"). In RA and RARS the risk is relatively low and the condition may persist for many years (e.g. 10 years). In RAEB and CMML the time course is typically quicker. 


It is estimated that 7,000 to 12,000 new cases of myelodysplastic syndrome are diagnosed each year in the U.S. These are mostly conditions of the elderly. However, there is an increased risk in those people who have had chemotherapy for other tumors.


  • Anaemia - chronic tiredness (in this condition blood transfusion is the only effective treatment, which can carry on for years)

  • Neutropenia (low white cell count) - increased susceptibility to infection

  • Thrombocytopenia (low platelet count) - increased susceptibility to bleeding

Because the cellular function is impaired the effects of low cell counts may be greater than in other conditions with a similar cell count be less impairment of normal function.

Vidaza the first approved treatment of MDS

There are currently no approved therapies for MDS. Vidaza (azacitidine for injectable suspension) manufactured by Pharmion is the first FDA approved drug for MDS. Azacitidine is a pyrimidine nucleoside analog of cytidine. Besides its cytotoxic effects, azacitidine is a member of a class of drugs in development known as "hypomethylating" or "demethylating" agents. Methylation of DNA is a major mechanism regulating gene expression. Researchers have found that an increase in methylation of DNA can result in blockage of the activity of genes that regulate cell division and differentiation, known as "suppressor genes." With suppressor gene expression blocked, cell division becomes unregulated, allowing or promoting cancer. In in-vitro studies, researchers have found that azacitidine can reverse the methylation of DNA, leading to reexpression of suppressor genes and a resulting differentiation and maturation of cells. Vidaza is thought to work by restoring normal growth and development of bone marrow cells.

The three trials

The safety and effectiveness of Vidaza, in the treatment of all subtypes of myelodysplastic syndrome, were established in studies involving a total of 268 patients. About 15% of patients in the three trials had complete or partial responses to Vidaza. Responses consisted of complete or partial normalization of blood in the bone marrow and normal levels of blood cells. In responders the need for blood transfusions was eliminated.

The most common side effects reported in clinical trials included nausea, anemia, low platelets in blood, diarrhea, fatigue, irritation at the injection site, and constipation.

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