Pfizer Withdraws Mylotarg Used for Rare Bone Marrow Cancer

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The US Food and Drug Administration announced today that Pfizer Inc is withdrawing the cancer drug Mylotarg from the US market after a clinical study found that the drug failed to demonstrate clinical benefits and had safety concerns.

Mylotarg (gemtuzumab ozogamicin for Injection) was approved in 2000 for patients age 60 and older with relapsed CD33-positive acute myeloid leukemia, a type of bone marrow cancer. Acute myeloid leukemia affects about 13,000 patients in the US, and less than 2,500 are treated with the drug each year.

Mylotarg was part of the FDA’s accelerated approval program which grants speedy access to drugs that show early promise. The drug, then marketed by Wyeth, was approved based on three studies of 142 patients showing a 26% overall remission rate and an average of almost 6 months extended survival when given as a single agent. The drug is given in two doses about 14 days apart.

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The withdrawal of the medication comes after a required follow-up study (SWOG S0106) was halted last August after the researchers found the fatality rate among patients given a combination treatment of Mylotarg plus chemotherapy to be 5.7%, compared to 1.4% for chemotherapy alone.

The medication also carries a warning label about a potentially fatal condition called veno-occlusive disease (VOD). At the time of approval, about 1% of patients experienced the liver complication, but the FDA reports that the rate has since increased.

Pfizer is delaying the drug withdrawal until October 15, 2010 to allow patients currently being treated with the product to stay on the medication if necessary, but the company will not market the drug for new patients.

"We are disappointed that the study did not confirm the clinical benefit of Mylotarg," Dr. Mace Rothenberg, senior vice president of clinical development and medical affairs for the Pfizer Oncology Business Unit, said in a statement. “Our primary concern is for patients who suffer from AML, which remains a very serious and difficult-to-treat disease with limited treatment options.”

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