Allos Therapeutics ( ALTH) said Wednesday that an approval application for the company's cancer drug pralatrexate was submitted to the Food and Drug Administration. The Westminster, Colo.-based company is seeking marketing approval for pralatrexate as a treatment for peripheral T-cell lymphoma (PTCL), a fast-growing cancer that affects white blood cells known as T-cells. There are no approved drugs to treat the disease. Allos' FDA filing for pralatrexate was submitted faster than many investors had expected. The FDA will probably take six months to review the drug, which means Allos could have the drug approved and launched this fall. In February, Allos reported that patients with PTCL responded to treatment with pralatrexate for more than nine months in a pivotal phase II study. The result signified that pralatrexate is having a durable and meaningful benefit for patients, Allos said, and supports the company's effort to get the drug approved in the U.S. Allos is likely to seek a partnership to help market pralatrexate, or perhaps, sell the company outright to a larger drug firm. Allos was able to submit pralatrexate for FDA approval based on a small phase II study because PTCL is diagnosed in only about 5,000 U.S. patients each year. The FDA didn't require Allos to compare the response rate of pralatrexate to another drug in the study because all the enrolled patients were previously treated, most multiple times, without success. Pralatrexate, or PDX, is a chemotherapy drug known as an "antifolate" that works by interfering with the ability of cancer cells to divide, resulting in cell death. Allos designed pralatrexate to be more potent than other antifolates, including the widely used drug methotrexate. Eli Lilly's ( LLY) cancer drug Alimta is another antifolate, approved for the treatment of lung cancer.