Roche Holding and Daiichi Sankyo Co. have won clearance from the Food and Drug Administration to sell a medication in the U.S. that treats patients with late-stage melanoma, the most deadly form of skin cancer.

The medication, Zelboraf, has been approved as therapy for patients whose tumors have spread or who have a form of melanoma that cannot be removed surgically. The drug belongs to an emerging class of treatments that target the genetic mutations that may lead to cancer. Zelboraf was engineered to attack tumors that express a gene mutation called BRAF V600E, according to an FDA statement, which said it has not been studied in patients whose melanoma tests negative for that mutation.

Although the BRAF protein is normally involved in regulating cell growth, it is mutated in about half of the patients with late-stage melanomas. Zelboraf acts as a BRAF inhibitor and is able to block the function of the mutated BRAF protein.

The FDA also approved of first-of-its-kind test called the cobas 4800 BRAF V6 Mutation test, a companion diagnostic that can help determine whether a patient's melanoma cells have the BRAF mutation.

"This has been an important year for patients with late-stage melanoma. Zelboraf is the second new cancer drug approved that demonstrates an improvement in overall survival," said Richard Pazdur, M.D., director of the Office of Oncology Drug Products in the FDA's Center for Drug Evaluation and Research.

In March, the FDA approved the sale of Yervoy, another treatment for late-stage melanoma that has been proved to help patients live longer.

In clinical trials, Zelboraf decreased the risk of death among melanoma patients with the BRAF mutation by 64 percent compared with people using standard chemotherapy. In addition, almost half of the patients saw their tumors shrink, compared with 5.5 percent of those treated with chemotherapy.

The most common side effects reported in Zelboraf users included joint pain, hair loss, fatigue, nausea and skin sensitivity when exposed to the sun.  About 26 percent of patients developed a skin-related cancer called cutaneous squamous cell carcinoma that is manageable with surgery, leading the FDA to warn Zelboraf patients to avoid sun exposure.

The new medication is expected to be extremely profitable. Although Roche is promoting Zelboraf in the U.S. with Daiichi Sankyo, The Wall Street Journal reports that the company owns the world-wide commercial rights to the drug.

Roche already distributes an arsenal of cancer drugs - such as Avastin, Herceptin and Rituxan - which accounts for 35 percent of the pharmaceutical giant's $74.8 billion total revenue.

The National Cancer Institute estimates that more than 70,000 new cases of melanoma will be diagnosed in the U.S. during 2011, leading to approximately 8,790 fatalities. The organization said that while heredity plays a major role in melanoma, individuals with fair skin, a history of blistering childhood sunburns and those with compromised immune systems may be more likely to develop the ailment.