27 February 2012
ByAppeared in BioNews 646
The European approval of a new gene-specific drug for an aggressive form of skin cancer marks another step towards an era of personalised medicine. A recent trial showed promising results, with the drug shrinking tumour size and extending life span.
The drug, which works by targeting a genetic mutation present in the tumours of approximately half of all melanoma patients, comes with its own diagnostic genetic test in order to identify which patients could benefit.
Vemurafenib (Zelboraf) was developed by Roche and according to Hal Barron, chief medical officer and head of product development at the company it 'exemplifies the benefits that [a] personalised approach to medicine can provide for patients, physicians and society'.
Dr Antoni Ribas, a professor of haematology and oncology at the Jonsson Cancer Center at the University of California, Los Angeles, who led the most recent drug trial, agrees. He says the results 'tell us that this drug is having a very big impact, and this changes the way we treat metastatic melanoma'.
Vemurafenib works by switching off the activity of a gene called BRAF, which is normally involved in regulating when a cell divides. When BRAF is mutated, as in some metastatic melanomas, it becomes permanently switched on, leading to excessive cell division and the formation of a tumour.
The trial run by Dr Ribas looked at 132 patients whose tumours all contained this BRAF mutation. The results, published in The New England Journal of Medicine, showed that vemurafenib treatment, while not curing the cancer, shrunk the melanomas 'better than chemotherapy' and extended the median lifespan of patients to 16 months, compared with nine months when using conventional treatment.
This is the first new drug developed for this disease in over a decade, which Roche is taking as a sign that their approach of designing personalised medicines along with diagnostic tests to identify suitable patients is the way forward. But while the drug is promising, there are some concerns.
In the latest trial only 53 percent of patients responded to the drug, despite all carrying the mutation, which has important implications when calculating costs. If this is the case in the general population, this would mean that only around 25 percent of metastatic melanoma patients would benefit. However, according to the authors, this still compares quite favourably to the typical response rate of less than 10 percent for the few alternative treatment options currently available.
In addition, the cancer will eventually become resistant to the drug, and start to grow again. This is currently the major limiting factor associated with many of the cancer drugs targeted at specific mutations.
'We're getting somewhere with these targeted drugs but we have a whole raft of research still to do to address the issue of resistance', says Kate Law, director of clinical and population research at Cancer Research UK.