In my last blog I talked about the new drug Vemurafenib that treats advanced skin cancer by targeting mutations found in roughly 50% of cancer patients with this disease. There is also a new drug that is likely to get FDA approval for the same cancer. New data came out for this drug a few days ago from phase three clinical trials.
This is a different kind of drug altogether than the very specific inhibitor of the mutated BRAF mutation. This new drug called Ipilimumab is an antibody. That means it is a protein that binds to other proteins and is made by B cells. Antibodies are natural, but this one is man-made. It targets the immune system in the patient. T cells in your body are usually helpful in killing cells that are infected and cells that become cancerous. However, as cancer cells are part of us, T cells are not very efficient at killing them. Even if they do, cancer cells can evade killing by shedding the target that the T cell needs to kill it or by suppressing the killing T cell when it tries to attack the cancer cell. This new drug is an antibody that binds to something on the T cell called CTLA4. CTLA4 is a natural inhibitor that the immune system uses to shut down T cell activity. This new antibody blocks this protein on the surface of the T cell and helps to keep the T cell active so that it can kill the cancer cell.
This drug given in combination with the chemotherapy agent Dacarbazine improves 3 year survival from 12% (with the chemo drug alone) to 20%. Overall survival went from 9 to 11 months; an added two month advantage. However, if you look at the data in the journal that reported the trial the number of patients who were living at 48 months was about 10% of the total who were enrolled into this trial. That 10% is exactly the same for the chemo alone group as it is for the chemo plus new antibody therapy group. So, patients do get to live an additional two months, but don’t do any better in the long-term.
This is a huge problem. Do we encourage patients to take this VERY expensive drug and get there hopes up even if it does no good in the long run? There are no cures here. There are no long-term benefits here. There is an additional few months (for only some of the patients). I don’t know the answer here, but I do know that after millions of dollars this clinical trial and drug will not help that many patients. The phase four clinical trials will start soon and the FDA will most likely approve this drug as they will the Vemurafenib, but for patients metastatic melanoma is still a killer.
Antibody therapies that boost the immune system are a nice way to look to the future. Immunotherapy has never worked well (high dose IL-2, a cytokine that boosts T cells has shown some limited but impressive results in a few cancers) and is usually highly toxic or has many undesired and often lethal side effects. In this study, the side effects of the anti-CTLA4 therapy is quite high…liver toxicity was observed at a high rate. The cost for immunotherapies is exceedingly high. In clinical trials it is provided free to the patients, but when the drug is approved by the FDA patients will now have to pay tens of thousands of dollars for this.
I don’t mean to sound so ‘all doom and gloom’, but this is what we are up against. Cancer therapy is making baby steps for these aggressive cancers. Despite spending hundreds of millions of dollars, these ‘so called’ blockbuster drugs are lackluster at best. I sure do hope research will prevail and we are able to significantly prolong the life of cancer patients.
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- New hope for melanoma patients (cnn.com)
- Three New Promising Treatments for Treating Lethal Melanoma | 80beats (blogs.discovermagazine.com)
- New skin cancer treatments emerge (bbc.co.uk)