UPDATED: Exelixis grabs first FDA nod for blockbuster hopeful against thyroid cancer

Exelixis won a coveted approval from the FDA to market its multikinase inhibitor cabozantinib for treating a rare form of thyroid cancer. The South San Francisco-based biotech ($EXEL) has notched the approval amid efforts to develop the drug, which will be marketed under the brand name Cometriq, for combating other cancers.

Cometriq is the second new drug to gain U.S. approval for treating medullary thyroid cancer in recent years, following the FDA's green light for AstraZeneca's ($AZN) Caprelsa (vandetanib) last year. The cancer infiltrates the cells of the thyroid gland responsible for producing the hormone calcitonin that keeps levels of calcium in the blood under control.

Exelixis has banked heavily on cabozantinib and the hoped-for future use of the compound to treat aggressive cases of prostate cancer, which is far more common than thyroid cancer and accounts for many more deaths. The company has Phase III trials in the works to study cabo in patients with prostate cancer, aiming to compete in one of the busiest areas of antitumor drug development in the industry. Data from pivotal studies are due out in 2014.

Medullary thyroid cancer accounts for only about 4% of cases of thyroid tumors, which are expected to be diagnosed in 56,460 Americans in 2013, according to the National Cancer Institute. Thyroid tumors are expected to kill about 1,780 people in the U.S. this year.

"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," Dr. Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, said in a statement.

Analysts expect sales of less than $100 million for cabo in MTC in the U.S. According to Cory Kasimov of J.P. Morgan, Exelixis is anticipating a market of 500-700 patients per year for this use of its lead drug, which the company has priced at $9,900 per month. With treatment durations of 10 months, Exelixis is rubbing against the 6-figure mark for its therapy. Which is pricier than Kasimov and others expected, but right in the ball park for a number of new cancer meds on the market.

- here's the FDA's release
- get more from Bloomberg
- here's Reuters' take

Special Report: Cabozantinib – Top 10 Late-Stage Cancer Drugs – 2012

Editor's note: Updated with pricing and market figures from analysts.

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