Two targeted treatments that are U.S. Food and Drug Administration (FDA)-approved for melanoma may be even more effective together. The drugs are dabrafenib, a BRAF inhibitor, and trametinib, a MEK inhibitor. In a phase II clinical trial with 160 people, the median survival was nearly 2 years with the combination treatment compared to 20 months with dabrafenib alone. These findings were presented at the 10th International Congress of the Society for Melanoma Research in Philadelphia, Pennsylvania. Now, the dabrafenib/trametinib combo has advanced to phase III trials.
“Inhibitors of BRAF protein kinase, such as Vemurafenib and Dabrafenib, have shown remarkable antitumor activity in patients with BRAF mutant melanoma. However, most of the patients developed drug resistance during the course of treatment, leading to resumed tumor growth. This drug resistance challenge underscores the need to improve on current BRAF-targeted therapy. In this study, we have shown that phenformin, a biguanide used for treating type 2 diabetes, enhances the antitumor activities of BRAF inhibitors in both cultured melanoma cells and a genetically engineered BRAFV600E-driven mouse model of melanoma. Our preclinical findings suggest that combining phenformin with a BRAF inhibitor may be a more effective treatment than a single-agent BRAF inhibitor for treating patients with melanoma whose tumor harbor BRAF mutations.”
“Although BRAF and MEK inhibitors have proven clinical benefits in melanoma, most patients develop resistance. We report a de novo MEK2-Q60P mutation and BRAF gain in a melanoma from a patient who progressed on the MEK inhibitor trametinib and did not respond to the BRAF inhibitor dabrafenib. We also identified the same MEK2-Q60P mutation along with BRAF amplification in a xenograft tumor derived from a second melanoma patient resistant to the combination of dabrafenib and trametinib. Melanoma cells chronically exposed to trametinib acquired concurrent MEK2-Q60P mutation and BRAF-V600E amplification, which conferred resistance to MEK and BRAF inhibitors. The resistant cells had sustained MAPK activation and persistent phosphorylation of S6K. A triple combination of dabrafenib, trametinib, and the PI3K/mTOR inhibitor GSK2126458 led to sustained tumor growth inhibition. Hence, concurrent genetic events that sustain MAPK signaling can underlie resistance to both BRAF and MEK inhibitors, requiring novel therapeutic strategies to overcome it.”
The U.S. Food and Drug Administration (FDA) has granted a priority review of whether two melanoma drugs work better together. The drugs are a BRAF inhibitor called Tafinlar (dabrafenib) and a MEK inhibitor called Mekinist (trametinib); both are already FDA-approved for use separately. Tumors, however, often become resistant to BRAF inhibitors, growing back after an initial period of shrinking. The hope is that adding a MEK inhibitor will prevent this resistance. The FDA’s ruling on this combination targeted treatment is expected in January 2014.
A new study suggests there may be a way to predict how well a targeted treatment will work against melanomas with BRAF mutations. This finding is from a phase II clinical trial that included 76 people with BRAF V600E mutated melanomas who were treated with dabrafenib, a BRAF inhibitor. Besides confirming the efficacy of dabrafenib, the study showed that the higher the initial level of tumor DNA in the blood, the better dabrafenib worked. That said, the researchers caution that this correlation must be confirmed in a larger study.
“Purpose: Dabrafenib (GSK2118436) is a potent inhibitor of mutated BRAF kinase. Our multicenter, single-arm, phase II study assessed the safety and clinical activity of dabrafenib in BRAFV600E/K mutation–positive metastatic melanoma (mut+ MM). Patients and Methods: Histologically confirmed patients with stage IV BRAFV600E/Kmut+ MM received oral dabrafenib 150 mg twice daily until disease progression, death, or unacceptable adverse events (AEs). The primary end point was investigator-assessed overall response rate in BRAFV600E mut+ MM patients. Secondary end points included progression-free survival (PFS) and overall survival (OS). Exploratory objectives included the comparison of BRAF mutation status between tumor-specific circulating cell-free DNA (cfDNA) and tumor tissue, and the evaluation of cfDNA as a predictor of clinical outcome…Conclusion: Dabrafenib was well tolerated and clinically active in patients withBRAFV600E/K mut+ MM. cfDNA may be a useful prognostic and response marker in future studies.”
Two new drugs that target melanomas were approved by the US Food and Drug Administration in May, and the drug developer has already filed for approval to use them in combination. The drugs are dabrafenib (Tafinlar), a BRAF inhibitor, and trametinib (Mekinist), a MEK inhibitor, and both are made by GlaxoSmithKline. The combination treatment request is based on promising results of a Phase I/II trial, which showed that the two drugs work better together than dabrafenib does alone. Results of a Phase III trial of the combination therapy are expected later this year.