The drug, PLX4032, is designed to block a protein produced by the faulty BRAF gene, which is overactive in more than half of all melanoma skin cancers.
Early stages of clinical testing, published in the New England Journal of Medicine, suggest that it may help to shrink advanced melanoma tumours with BRAF faults.
A new treatment for advanced melanoma would be an important advance, as it can be hard to treat once the original cancer has spread to other parts of the body.
Scientists at Massachusetts General Hospital (MGH) Cancer Centre and the Memorial Sloan-Kettering Cancer Centre in New York, along with colleagues in Australia, enrolled 55 patients for the first stage of their study.
Patients received doses of PLX4032 which were gradually increased until side effects became a problem, thus helping to determine an acceptable dose.
Of the 55 patients involved in this stage of the research, 16 had faulty BRAF genes and the tumours of 11 of these patients shrank.
In the second stage of the research, 32 patients with BRAF-mutated melanoma were given 960mg of PLX4032, twice a day for the duration of the trial.
In 26 out of 32 patients, tumours shrank by more than 30 per cent, and two of the patients saw their tumours completely disappear.
Lead study author Dr Keith Flaherty, director of developmental therapeutics at the MGH Cancer Centre, commented: “Until now, available therapies [for advanced melanoma] were few and unreliable.
“One of the things that makes these results truly remarkable is that this drug works so reliably.”
However, the researchers observed that, after initially responding to treatment with PLX4032, patients did develop resistance to the drug after a time and their tumours started to grow again.
Dr Flaherty added: “Although we don’t know how long response may last, the ability to beat this disease down in the short term will buy us time to strategise second-line therapies and design the next generation of trials.”
Senior author Dr Paul Chapman, from the Melanoma and Sarcoma Service at Memorial Sloan-Kettering Cancer Centre, said, “We have seen many tumours shrink rapidly and, in some patients, quality of life improved dramatically.
“In the future, we hope to combine PLX4032 with other anti-melanoma drugs currently being developed.”
Professor Richard Marais, Cancer Research UK’s melanoma expert at The Institute of Cancer Research, said: “These results are extremely exciting. This is the first time in over 30 years that this level of response has been seen in melanoma patients in any clinical trial.
“While these results are very promising, there is still work to be done. Although patients initially respond they can often relapse during treatment, so now we need to learn how to get longer-lasting responses in these patients.”
Source: Cancer Research UK