The U.S. Food and Drug Administration on Thursday announced that it has approved Cometriq, or cabozantinib, to treat medullary thyroid cancer that has metastasized or spread to other parts of the body.

"Cometriq is the second drug approved to treat medullary thyroid cancer in the past two years and reflects FDA's commitment to the development and approval of drugs for treating rare diseases. Prior to today's approval and the approval of Caprelsa in April 2011, patients with this rare and difficult to treat disease had limited therapeutic treatment options," said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research.

The cancer develops in cells in the thyroid that make the hormone calcitonin that helps with calcium levels maintenance in the blood.

The efficacy of the new drug was assessed during a clinical study that involved 330 patients with medullary thyroid cancer. The drug increased the length of time a person stayed without cancer and also reduced the size of the tumor, FDA said.

The side-effects of the drug include diarrhea; inflammation or sores of the mouth; redness, pain, or swelling of the digits, weight loss and loss of appetite.