Acute lymphoblastic leukemia is a type of cancer in which the bone marrow makes too many lymphocytes, a type of white blood cell. White blood cells help the body fight infection and are formed in the bone marrow.

　　Erwinaze is injected directly into the muscle three times a week and works by breaking down one of the body's protein building blocks (the amino acid, asparagine) that is present in the blood, and is necessary for the growth of all cells. Leukemia cells cannot produce this protein building block. When a patient is treated with Erwinaze the leukemia cells die. Normal human cells are able to make enough asparagine for their own needs through biosynthesis and will not be affected by treatment with Erwinaze.

　　"The approval of Erwinaze underscores the FDA's commitment to the approval of drugs for conditions with limited patient populations with unmet medical needs using novel trial endpoints," said Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research.

　　Side effects associated with Erwinaze treatment include serious allergic reactions, inflammation of the pancreas, high blood levels of liver enzymes, blood clotting, bleeding, nausea, vomiting and high blood sugar.