Jazz Pharmaceuticals (JAZZ) has made its mark as the provider of Xyrem, a drug for the sleep disorder narcolepsy. Jazz may be less known for being among the companies fighting cancer. Its Erwinaze is a treatment for acute lymphoblastic leukemia, which affects more than 5,000 Americans and is the leading cause of cancer in children. Erwinaze sales in Q4 reached $53 million, an increase of 21% from the year-earlier period.