The FDA has approved Cometriq (cabozantinib) to treat medullary thyroid cancer that has spread to other parts of the body.

Cometriq, marketed by Exelixis and AstraZeneca, is a kinase inhibitor that blocks abnormal kinase proteins involved in the development and growth of medullary cancer cells.

“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,” said Richard Pazdur, M.D., director of the office of hematology and oncology products in the FDA’s Center for Drug Evaluation and Research. “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.”

The FDA completed review of Cometriq’s application in six months under the agency’s priority review program. This program provides for an expedited six-month review for drugs that may offer major advances in treatment or that provide a treatment when no adequate therapy exists. Cometriq also received orphan-product designation by the FDA because it is intended to treat a rare disease or condition.

The safety and effectiveness of Cometriq were established in a clinical study involving 330 patients with medullary thyroid cancer. Treatment with Cometriq increased the progression-free survival and, in some patients, reduced the size of tumors.

Patients who were given Cometriq lived an average of 11.2 months without tumor growth compared with an average of four months in patients receiving placebo. Results also showed that 27% of patients treated with Cometriq had reductions in tumor size lasting an average of nearly 15 months, while patients who received a placebo saw no reductions. Treatment with Cometriq did not extend patients’ lives.

The most common side effects were diarrhea, inflammation or sores of the mouth, hand-foot syndrome, weight loss, loss of appetite, nausea, fatigue, oral pain, graying or loss of hair color, bad taste, new or worsening high blood pressure, abdominal pain and constipation. The most common laboratory abnormalities included increases in liver enzymes, low calcium and phosphorus, decreased white blood cells and platelets.

Medullary thyroid cancer develops in cells in the thyroid gland that make a hormone called calcitonin, which helps maintain a healthy level of calcium in the blood. This type of cancer may occur spontaneously or in families with certain genetic mutations that result in one or more cancers of the endocrine system, including the thyroid gland.