The evolution of combined molecular targeted therapies to advance the therapeutic efficacy in melanoma: a highlight of vemurafenib and cobimetinib

Metastatic melanoma is an aggressive, rapidly progressive disease which historically had very few effective treatment options. However, since 2011, the therapeutic landscape of melanoma has undergone a dramatic transformation with two distinct approaches and has catalyzed the successful advancement in the clinical field of immuno-oncology. In addition, the recognition of a key oncogenic driver mutation in melanoma, BRAF, stimulated the development of multiple potent kinase inhibitors which has also influenced the expansion and use of targeted agents in the practice of oncology. Vemurafenib, the initial BRAF inhibitor approved for the treatment of melanoma, was the first agent to demonstrate rapid clinical responses and significantly improved survival which was a clinical breakthrough in the treatment of melanoma. Although exciting and practice changing, the unparalleled responses with vemurafenib are usually not sustained. Further investigations delineated several mechanisms of acquired resistance which are most often mediated by the upregulation of the MAPK pathway. MEK inhibitors, another class of small-molecule inhibitors, were developed as an alternative agent to suppress the MAPK pathway downstream, independent from BRAF activation. Multiple studies have demonstrated the improvement in antitumor activity when MEK inhibitors are used in combination with BRAF inhibitors in the treatment of metastatic melanoma. This is a review of the investigations that led to the US Food and Drug Administration approval in 2015 of the combination of vemurafenib and cobimetinib, adding to the quickly growing armament for the treatment of advanced or metastatic melanoma with a BRAF V600 mutation.