On May 19, 2004, the FDA approved azacitidine for injectable suspension (Vidaza™, made by Pharmion Corporation) for use in patients with all subtypes of myelodysplastic syndromes. Approval was based on response rates supported by reduction or elimination of transfusion dependence.

Safety and efficacy were demonstrated in one multicenter, randomized trial in 191 patients with all five French, American and British subtypes of myelodysplastic syndromes comparing azacitidine treatment to observation only, and in two multicenter single-arm azacitidine trials in 120 patients.

Azacitidine was administered at a dose of 75 mg/m2/day for 7 days every 28 days subcutaneously in the randomized trial and in one of the single-arm trials. Patients in the "observation only" arm of the randomized trial were permitted to cross over to Vidaza treatment. Greater than 50 percent of observation only patients crossed over to Vidaza treatment at the time of disease progression. Patients with an adjudicated diagnosis of AML at baseline were excluded from the efficacy analysis of response rate.

Clinical response (complete and partial) was observed in approximately 16 percent of the azacitidine patients. The response rates were similar in patients randomized to Vidaza treatment (15.7 percent), in patients who crossed over from the observation arm to Vidaza treatment (12.8 percent), and in patients in the two single arm trials (12.7 percent and 19.1 percent). None of the patients in the observation only arm had clinical response. The difference in response rates between Vidaza treated patients and "observation only" patients was statistically significant (p<0.0001).

Median response duration was greater than 330 days in the randomized trial. The response duration could not be accurately estimated, because most patients remained in response status at the time of study completion. In addition to complete and partial responses, approximately 24 percent of Vidaza-treated patients had either reduction of the need for transfusions and/or ≤50 percent normalization of blood cell counts and/or bone marrow blast percentages.

The major toxicity of azacitidine was myelosuppression, as manifested by thrombocytopenia (and bleeding), neutropenia (and infections), and anemia. Myelosuppression decreased with the onset of a response.

Other common adverse events were gastrointestinal (nausea, vomiting, diarrhea, constipation, anorexia), constitutional (fatigue, weakness, fever, rigors), musculoskeletal (arthralgia, pain in limb), pulmonary (cough, dyspnea), and skin and soft tissue (ecchymoses, rash, erythema).

Full prescribing information is available, including clinical trial information, safety, dosing, drug-drug interactions and contraindications. There is also an FDA press release.

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