The U.S. Food & Drug Administration (FDA) has granted approval to Merck’s new immunotherapy drug, Keytruda (pembrolizumab), for treating metastatic melanoma.   It is the first anti-PD-1 drug, aimed at re-energizing a patient’s protective immune response to cancer to have received FDA approval in the U.S.

Of the more than one million new diagnoses of skin cancer each year, roughly 76,000 involve melanoma. More than 9,000 people die of melanoma each year in the United States. Melanoma is dangerous because it is more likely than other types of skin cancer to spread (metastasize) to other parts of the body.

The anti-PD-1 antibody pembrolizumab demonstrated promising survival rates among patients with advanced melanoma. Data from an ongoing trial of the drug were presented at the 50th Annual Meeting of the American Society of Clinical Oncology (ASCO 2014) in Chicago this June.

PD-1 is a protein that inhibits certain types of immune responses. Drugs that block PD-1, such as pembrolizumab, may enhance the ability of the immune system to fight cancer. In earlier studies pembrolizumab has demonstrated anticancer activity in advanced melanoma, including disease that has progressed on other therapy.

The findings for pembrolizumab presented at ASCO 2014 represent the largest study to date of the drug in patients with advanced melanoma. A total of 411 participants with varying stages of disease and different types of previous treatment were included. Of these patients, 221 had received the immunologic therapy Yervoy® (ipilimumab), while 190 had not.

Three different dosing schedules of pembrolizumab were evaluated in both patients who had been previously treated with Yervoy and those who had not: 10 mg/kg or 2 mg/kg, both every three weeks, or 10 mg/kg every two weeks (192, 162, and 57 patients, respectively).

  • Among 365 patients with measureable disease when they enrolled in the study, the following patients had a response (a decrease in the amount of cancer) to pembrolizumab at a follow-up of six months or more: 28% of those who had previously received Yervoy and 40% of those who had not received Yervoy.
  • Anticancer responses were still holding in 88% of the patients at the most recent analysis (May 2014).
  • Median progression-free survival was 23 weeks for those previously treated with Yervoy and 24 weeks for those not treated with Yervoy.
  • Though media overall survival had not yet been reached, 71% of all patients were alive at one year.
  • All three dosing schedules appeared to have an anticancer effect.
  • Overall, 12% of patients experienced side effects, and only 4% discontinued treatment due to side effects.

These findings included two important treatment groups of patients with advanced melanoma: those who had previously received Yervoy and those who had not. As well, it assessed different dosing scheduleds. With these factors combined, these and other data demonstrated that pembrolizumab is safe and effective for patients with advanced melanoma.

Reference: Ribas A, Hodi FS, Kefford R, et al. Efficacy and safety of the anti-PD-1 monoclonal antibody MK-3475 in 411 patients (pts) with melanoma (MEL). J Clin Oncol 32:5s, 2014


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