A combination of two targeted, orally administered drug therapies – trametinib and dabrafenib – has been approved by the Food and Drug Administration for treating patients with unresectable melanoma or metastatic melanoma with BRAF V600E or V600K mutations, manufacturer GlaxoSmithKline announced on Jan. 9.
An FDA-approved test is used to detect the mutations, according to the company statement.
Trametinib, marketed as Mekinist, and dabrafenib, marketed as Tafinlar, were each approved in May 2013 as separate treatments for metastatic or unresectable melanomas that express the mutations – along with a companion test to detect the mutations. Both are kinase inhibitors.
The GSK statement noted that the accelerated approval of the combination therapy is based on the response rate and median duration of response results in a phase I/II study of 108 patients, which compared the combination (150 mg of dabrafenib twice a day and 2 mg of trametinib once a day) to treatment with dabrafenib alone. The overall response rates, as assessed by the investigators, were 76% among those on the combination and 54% for those on dabrafenib alone. The median duration of response was 10.5 months among those on the combination, vs. 5.6 months among those on dabrafenib alone.
The most common adverse events associated with the combination treatment included fever in 71% of patients, chills in 58%, fatigue in 52%, rash in 45%, nausea in 44%, vomiting in 40%, and diarrhea in 36%. Renal failure, pyrexia, back pain, and hemorrhage were among the most common grade-3 or -4 adverse events among those on the combination.
Serious adverse effects associated with treatment, including some potentially fatal effects, are new primary cutaneous skin cancers, tumor promotion in wild-type BRAF melanoma, and hemorrhagic events, according to GSK.
The FDA approval occurred through an accelerated process based on clinical evidence that the treatment has an effect on a surrogate endpoint that is reasonably likely to predict a clinical benefit to patients. As a condition of accelerated approval, manufacturers are required to provide more clinical data confirming benefit, and if the follow-up studies fail to confirm benefit, the FDA can withdraw approval.
Full approval is dependent on the results of an ongoing phase III study, GSK said.
The updated trametinib label states that "improvement in disease-related symptoms or overall survival has not been demonstrated" for the combination treatment.
The prescribing information for Mekinist is available at http://us.gsk.com/products/assets/us_mekinist.pdf. The prescribing information for Tafinlar (which does not yet include the updated information on the combination therapy approval) is available at http://us.gsk.com/products/assets/us_tafinlar.pdf.