WASHINGTON - Drugmaker Pfizer Inc is pulling a decade-old leukemia medicine off the U.S. market after a study found a higher death rate and no benefit for patients.

Mylotarg won approval under an abbreviated process to help bring treatments for serious diseases to patients more quickly. Medicines cleared in that way must pass follow-up tests to confirm they work.

The Food and Drug Administration said on Monday it asked Pfizer to withdraw the drug after a recent clinical trial raised new concerns about the product's safety and the drug "failed to demonstrate clinical benefit to patients enrolled in trials."

Mylotarg's first-quarter sales were $8.8 million, making it a small product for the world's largest drugmaker. The company reported first quarter revenue of $16.8 billion. Pfizer acquired Mylotarg when it bought Wyeth in October 2009.

Pfizer said it was voluntarily withdrawing the drug after a study showed adding Mylotarg to chemotherapy did not extend survival for patients with previously untreated acute myeloid leukemia (AML), an aggressive bone marrow cancer.

"We are disappointed that the study did not confirm the clinical benefit of Mylotarg," Dr. Mace Rothenberg, a Pfizer senior vice president, said in a statement.

The trial also showed more deaths in the first couple months of treatment. The fatality rate was 5.7 percent for Mylotarg patients, compared with 1.4 percent without the drug, Pfizer said.

Mylotarg is the first drug approved under the FDA's abbreviated process to be withdrawn for failing to show effectiveness, agency officials said.

The injectable drug was approved for treating certain patients age 60 and older with recurrent AML who were not candidates for other chemotherapy. Patients with AML have few treatment options and may die within months of a diagnosis.

The FDA cleared Mylotarg for sale in 2000 on the basis of trials involving 142 AML patients. About one-quarter of patients saw their disease go into remission.

The agency required a follow-up study to confirm Mylotarg helped patients live longer. The trial started in 2004 and was stopped ahead of schedule last year when researchers saw no benefit and the higher death rate.

AML affects about 13,000 new patients in the United States each year. Fewer than 2,500 are treated with Mylotarg annually, Pfizer estimated.

The drug will be withdrawn October 15, but Pfizer recommends that no new patients be prescribed it in the meantime.

People already taking Mylotarg may continue their course of therapy after consulting with their doctors, the company said. Mylotarg is given in two doses typically two weeks apart.

After the withdrawal, new patients can only be treated under an FDA process for testing of experimental drugs.

Mylotarg is sold in nine other countries. Pfizer will work with authorities there "to determine the best action forward," Rothenberg said in an interview.

The drug was designed to be less toxic than other drugs by delivering cancer-killing effects straight to tumors, thereby minimizing damage to other cells and tissues.

There are no other medicines approved for treating relapsed AML. "The number one option for people with relapsed disease is a clinical trial" of an experimental medicine or a drug already sold for treating another disease, said Dr. Alison Walker, a hematologist and oncologist at The Ohio State University.

Mylotarg's withdrawal "is an example of the need to support the scientifically-rigorous post-marketing capability of the FDA for long-term study" of risks and benefits from medicines, said Ryan Hohman, a spokesman for Friends of Cancer Research.

Pfizer shares fell 0.7 percent to close at $15.10 Monday on the New York Stock Exchange.