Results of Phase I trial published in The Lancet medical journal showed substantial shrinking of tumors in patients treated with the drug, dabrafenib, and showed promise against secondary melanoma tumors, or metastases, in the brain.

Dabrafenib blocks the activity of a cancer-causing mutated form of a gene known as BRAF, which is found in about half of melanoma cases.

Results released on Wednesday from a separate trial looking at dabrafenib in combination with another GSK drug, trametinib, were also positive.

Researchers said the results of the dabrafenib-only trial, although early-stage, represented an important step forward in the treatment of this deadly cancer.

Melanoma is diagnosed in nearly 160,000 people worldwide each year. It can spread quickly to internal organs and average survival is six to nine months.

Georgina Long of the Melanoma Institute Australia and Westmead Hospital in Sydney, and Gerald Falchook from the University of Texas in the United States, treated 184 patients with dabrafenib in a Phase I trial -- the earliest step of the drug development process in humans.

They said some of the most exciting results came from a subset of 10 patients whose tumors had spread to their brains.

None of these had previously received treatment for their brain tumors. However, the brain metastases disappeared in four of the patients when they were treated with 150 milligrams of dabrafenib twice daily.

Five patients saw their brain metastases shrink, and one had stable disease, where the tumors remained the same size.

"The results in the brain were remarkable," Long said. "I don't think there is a single other systemic agent that is as active in the brain."

Experts not involved in the trial also said the drug showed promise.

In a commentary piece in The Lancet, Geoffrey Gibney and Vernon Sondak from the H Lee Moffit Cancer Center and Research Institute in the U.S. described the results as "impressive" and "encouraging".

Long and Falchook said it was not clear why the drug was so effective in the brain where other drugs have failed, but further trials are under way to try to clarify the mechanism.

"The big message is that the brain, with this drug, is just like another organ," Long said. "If you are going to respond in your lung and liver, you tend to respond in your brain as well."

Unfortunately, for most of the patients with brain metastases, the response to the drug was limited to several months.

Long said, however, these few months of extension of life were very rare in patients with melanoma that has spread to the brain. Normally, such patients can only expect to survive for four months from the point of diagnosis, she said.

"With this drug, these patients had no progression of their disease for a median of 4.2 months. Without treatment, many of them might already have died at that point," she said.

Two of the 10 brain metastasis patients who received the drug survived for more than 12 months. One was still alive and receiving the drug at 19 months.

(Editing by David Hulmes)

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