"Approval of this drug is extremely significant because the treatments we have had up until this year were well known to have no effect on overall survival," said Dr. Kelly McMasters, chairwoman of the department of surgery at the University of Louisville Hospital. "It is gratifying to see a well-tolerated new targeted therapy that is effective."

The study, funded by the drug's pharmaceutical developer, Hoffman-La Roche, followed 675 patients randomized to receive either Zelboraf or a standard chemotherapy drug. Seventy-seven percent of those who received Zelboraf were still living after eight months, compared to only 64 percent of those who received the standard chemotherapy drug.

The drug specifically targets tumors with the genetic mutation known as BRAF V600E. The agency also approved a diagnostic test that will determine whether someone has the mutation.

"Today's approval of Zelboraf and the cobas test is a great example of how companion diagnostics can be developed and used to ensure patients are exposed to highly effective, more personalized therapies in a safe manner," Alberto Gutierrez, director of the FDA's Office of In Vitro Diagnostic Device Evaluation and Safety, said in a statement.

BRAF protein mutation is found in nearly half of all patients with late-stage melanoma.

"We now have the capability to analyze a patient's melanoma tumor for the genetic mutation BRAF and use the targeted treatment Zelboraf to attack the tumor, shrink it and stop the progression of this deadly disease," said Dr. Anna Pavlick, director of the NYU Melanoma Program at the NYU Cancer Institute, who has been involved in clinical trials for Zelboraf.

Unlike chemotherapy, which only stops mutated cells from dividing, Zelboraf shuts down the abnormal signals of the tumor cells that are caused by the genetic mutation and stops the cells from dividing, without affecting healthy cells.

While the study focused on patients who had not undergone any treatment for their melanoma prior to Zelboraf, earlier trials showed the drug was still effective even for patients who previously received chemotherapy for their condition.

"Patients who failed previous therapy whose tumor harbors BRAF V600E mutation should be considered for this treatment," said Dr. Sekwon Jang, a medical oncologist at Washington Hospital Center in Washington, D.C., who specializes in melanoma.

Although Zelboraf is only approved for late-stage melanoma, some experts believe it is worth researching whether the drug could also help patients with non-metastatic melanoma.

"I anticipate a clinical trial testing this drug in those patients who have high risk of recurrence after surgery to answer whether this drug can reduce melanoma recurrence," said Jang.

Skin cancer is the most common form of cancer, affecting more than 1 million new people each year, according to the National Cancer Institute. Melanoma, one of the most deadly of these cancers, accounts for approximately 70,000 of these new cases. It also kills an estimated 9,000 people.

Since the same genetic mutation is found in tumors that develop into other forms of cancer, some experts say the drug could be a possibility for other types of cancers beyond skin cancer.

The drug is now being tested in patients with thyroid cancer with the BRAF V600E mutation, Jang said.

In March 2011, the FDA approved Yervoy, another drug that trials showed extended life for many patients with late-stage melanoma.