"PLX4032 is different because it attacks the genetic program that is causing the cells to divide uncontrollably, and we think the BRAF mutation is driving that program. The drug is blocking the genetics of the tumor, rather than trying to interfere with the proliferation of the cells and, as a result, there are fewer side effects, although there are some. We are seeing some pretty dramatic and rapid responses, and they are occurring in sites where we rarely see responses to chemotherapy, such as in the bone."
Chapman noted that "we don't know yet how long these responses will last, and we have had patients whose cancer has progressed after initially responding; so we are putting a lot of effort into studying the patients who do relapse, trying to understand how their tumors have become resistant.
"In addition, one of the main side effects we've seen is that some patients develop early, non-melanoma skin cancers, such as squamous cell skin cancer. We are very vigilant about this, and although they are very easy to cut out, it's something we are keeping a close eye on."
A phase II trial involving 90 patients will start at the end of this year, and a phase III trial involving several hundred patients is scheduled to begin at the end of this year or early next year.
In related news from the cancer meeting in Berlin, researchers said they've shown that ultrasound can be used to identify whether cancer has started to spread in melanoma patients, and to what extent. This information can help doctors decide how much surgery, if any, a patient requires and predict the patient's likelihood of survival.
"We have identified two ultrasound patterns of lymph node metastasis in melanoma patients which can identify correctly any amount of tumor cells in the senti
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