The U.S. Food and Drug Administration (FDA) has approved Mekinist® (trametinib) in combination with Tafinlar® (dabrafenib) to treat patients with advanced melanoma.
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.
In 2013, both Mekinist and Tafinlar were approved as single agents to treat patients with unresectable (cannot be removed by surgery) or metastatic (late stage with cancer spread) melanoma. Both are targeted agents that interfere with the BRAF pathway.
The BRAF gene is known to play a part in cell growth, and mutations in BRAF are common in several types of cancer. Approximately half of all melanomas carry a specific BRAF mutation known as V600E. This mutation produces an abnormal version of the BRAF protein that stimulates cancer growth. Some melanomas carry another BRAF mutation known as V600K.
The approval of the drug combination was based on a study that included 162 patients with unresectable or metastatic melanoma with the BRAF V600E or V600K mutation, most of whom had not received prior therapy. Participants received either Mekinist in combination with Tafinlar or Tafinlar as a single agent until their melanoma progressed or side effects became intolerable.
The results indicated that 76 percent of patients treated with Mekinist/Tafinlar experienced an objective response (meaning their cancer shrank or disappeared). This response lasted an average of 10.5 months. In contrast, only 54 percent of participants treated with single-agent Tafinlar experienced an objective response—and the response lasted an average of 5.6 months.
The most common side effects reported in patients who received Mekinist/Tafinlar included fever, chills, fatigue, rash, nausea, vomiting, diarrhea, abdominal pain, peripheral edema, cough, headache, joint pain, night sweats, decreased appetite, constipation and muscle pain. The incidence and severity of fever increased when the two drugs were used together.
There were serious side effects, including bleeding, clot formation, heart failure, skin problems and eye problems. One serious side effect of Tafinlar (the development of a new squamous cell carcinoma of the skin) appeared to be mitigated by using the drug in combination with Mekinist. The incidence of squamous cell carcinoma of the skin in this trial was 7 percent with the combination compared to 19 percent with single agent Tafinlar.
Other clinically significant side effects include kidney injury. In addition, women of childbearing potential are advised that Mekinist and Tafinlar can cause birth defects in a developing fetus. What’s more, both Mekinist and Tafinlar treatment may cause infertility in men and women.
The combination of Mekinist and Tafinlar was approved as part of the FDA’s priority review program, which allows an expedited six-month review of drugs that may offer major advances in treatment. What’s more, the combination was also approved as part of the FDA’s accelerated approval program, which provides earlier access to promising new drugs while the company conducts confirmatory clinical trials.
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