Improved overall survival in melanoma with combined dabrafenib and trametinib

Medical management of malignant melanoma

The treatment and outcomes for people with metastatic melanoma have changed considerably in the past few years with the introduction of targeted anticancer drugs. About half of the patients with metastatic melanoma will have activating mutations in the BRAF gene. These people may benefit from a BRAF inhibitor (vemurafenib or dabrafenib) or a MEK inhibitor (trametinib). Addition of a MEK inhibitor to a BRAF inhibitor improves progression-free survival and alters the adverse effect profile. Ipilimumab is another drug indicated for metastatic melanoma. It works by altering the patient's own immune response to the tumour. Toxicities are common with these drugs and include arthralgias, fatigue, photosensitivity, squamous cell carcinomas, fever, diarrhoea, pruritus and immune-related adverse effects.

Combination therapy of melanoma using kinase inhibitors

PURPOSE OF REVIEW

Treatment options for metastatic melanoma depend on the clinical course of the disease and the molecular profile such as mutations of the BRAF gene. In this article, we review the current state of targeted therapy with kinase inhibitors.

RECENT FINDINGS

Despite major advancements in targeted therapy of metastatic melanoma, most patients relapse and show progressive disease after 5-7 months with single inhibition of BRAF or MEK. Acquired resistance is virtually universal and mediated by diverse mitogen-activated protein kinase-dependent or independent mechanisms. Recent evidence favours concurrent targeting of BRAF and MEK in patients with BRAFV600-mutated melanoma instead of BRAF inhibitor monotherapy. The combination delays the onset of acquired resistance, resulting in increased progression-free and overall survival. A growing number of early trials evaluate the efficacy of inhibitors targeting additional pathways such as phospho-inositide 3-kinase/AKT in conjunction with BRAF or MEK. Even though consistent and mature phase III study results are not yet available for these combinations, the repertoire of targeted therapy in metastatic melanoma is wide and promising.

SUMMARY

The short era of single BRAF inhibition in BRAF-mutated melanoma is soon taken over by dual concurrent inhibition of MEK and BRAF.

A periodic table for cancer

ABSTRACT 

Cancers exhibit differences in metastatic behavior and drug sensitivity that correlate with certain tumor-specific variables such as differentiation grade, growth rate/extent and molecular regulatory aberrations. In practice, patient management is based on the past results of clinical trials adjusted for these biomarkers. Here, it is proposed that treatment strategies could be fine-tuned upfront simply by quantifying tumorigenic spatial (cell growth) and temporal (genetic stability) control losses, as predicted by genetic defects of cell-cycle-regulatory gatekeeper and genome-stabilizing caretaker tumor suppressor genes, respectively. These differential quantifications of tumor dysfunction may in turn be used to create a tumor-specific ‘periodic table’ that guides rational formulation of survival-enhancing anticancer treatment strategies.

BRAF and MEK inhibition in melanoma

INTRODUCTION

Selective inhibition of the MAPK pathway with either BRAF or MEK inhibition has emerged as a key component for the treatment of BRAF-mutant metastatic melanoma. New evidence suggests that the combination of BRAF and MEK inhibitors improves tumor response rate and progression-free survival, while potentially attenuating some of the serious adverse events observed with monotherapy.

AREAS COVERED

This review covers the current data on the efficacy and safety of the selective BRAF (vemurafenib and dabrafenib) and MEK (trametinib) inhibitors as well as the available data on BRAF inhibitor + MEK inhibitor combination therapy (dabrafenib + trametinib and vemurafenib + cobimetinib). The efficacy, safety and toxicity data are discussed from Phase I, Phase II and Phase III trials of these drugs.

EXPERT OPINION

Combination therapy with the BRAF and MEK inhibitors improves response rates and progression-free survival in patients with BRAF-mutant metastatic melanoma. Some of the serious adverse events, in particular, the incidence of cutaneous squamous cell carcinoma, are attenuated with combination therapy, whereas milder side effects such as pyrexia can be more common with combination therapy. Although dose reductions and dose interruptions are slightly more common with combination therapy, overall data supports the notion that combination therapy is safe and improves the outcomes for patients compared to single agent BRAF inhibitors.

Preliminary results from a prospective trial of preoperative combined BRAF and MEK-targeted therapy in advanced BRAF mutation-positive melanoma

BACKGROUND

We conducted a prospective trial of BRAF and mitogen-activated protein kinase kinase (MEK) targeted therapy in advanced, operable BRAF mutation-positive melanoma to determine feasibility, tumor response rates, and biomarkers of response and resistance.

STUDY DESIGN

Thirteen patients with locally or regionally advanced BRAF mutation-positive melanoma received dabrafenib 150 mg po bid for 14 days, followed by dabrafenib plus trametinib 2 mg po daily for 14 days before operation. Biopsies and tumor measurements were obtained at baseline and days 14 and 28. Formalin-fixed paraffin embedded specimens were analyzed with hematoxylin and eosin, Ki-67, cleaved caspase-3, CD8, phosphorylated extracellular signal-regulated kinase (ERK), and phosphorylated MEK immunostains.

RESULTS

Therapy was tolerated well, with toxicity ≥ grade 3 in 2 of 13 (15%) patients. All 12 patients receiving >14 days of therapy had substantial reduction in tumor volume (65% at day 14 and 78% at day 28) and underwent resection. After 14 days of dabrafenib therapy, there was a marked reduction in viable melanoma cells and a CD8 T-cell--rich infiltrate. Proliferation of the residual melanoma cells was reduced and apoptosis was increased. The cells continued to express phosphorylated ERK and phosphorylated MEK consistent with incomplete mitogen-activated protein kinase pathway inhibition.

CONCLUSIONS

Preoperative targeted therapy of advanced BRAF-mutant melanoma is feasible, well tolerated, induces brisk tumor responses, and facilitates correlative science. A CD8 T-cell-rich infiltrate indicates a potential immune-mediated mechanism of action. Both proliferation and apoptosis were inhibited, but the mitogen-activated protein kinase pathway remained activated, suggesting intrinsic resistance in a subset of tumor cells. Additional investigation of the anti-tumor immune response during targeted therapy and the mechanisms of intrinsic resistance can yield novel therapeutic strategies.

BRAF-mutant melanoma: treatment approaches, resistance mechanisms, and diagnostic strategies

BRAF inhibitors vemurafenib and dabrafenib achieved improved overall survival over chemotherapy and have been approved for the treatment of BRAF-mutated metastatic melanoma. More recently, the combination of BRAF inhibitor dabrafenib with MEK inhibitor trametinib has shown improved progression-free survival, compared to dabrafenib monotherapy, in a Phase II study and has received approval by the US Food and Drug Administration. However, even when treated with the combination, most patients develop mechanisms of acquired resistance, and some of them do not achieve tumor regression at all, because of intrinsic resistance to therapy. Along with the development of BRAF inhibitors, immunotherapy made an important step forward: ipilimumab, an anti-CTLA-4 monoclonal antibody, was approved for the treatment of metastatic melanoma; anti-PD-1 agents achieved promising results in Phase I/II trials, and data from Phase III studies will be ready soon. The availability of such drugs, which are effective regardless of BRAF status, has made the therapeutic approach more complex, as first-line treatment with BRAF inhibitors may not be the best choice for all BRAF-mutated patients. The aim of this paper is to review the systemic therapeutic options available today for patients affected by BRAF V600-mutated metastatic melanoma, as well as to summarize the mechanisms of resistance to BRAF inhibitors and discuss the possible strategies to overcome them. Moreover, since the molecular analysis of tumor specimens is now a pivotal and decisional factor in the treatment strategy of metastatic melanoma patients, the advances in the molecular detection techniques for the BRAF V600 mutation will be reported.

Converting biology into clinical benefit: lessons learned from BRAF inhibitors

The identification and pharmacological targeting of activating BRAF mutations in melanoma has led to significant improvements in patient outcomes. This perspective paper illustrates the lessons learned from the study of BRAF mutations and the development of BRAF inhibitors. The relevance of these lessons to the development of future targeted therapies is highlighted.

Society for melanoma research and american heart association scientific sessions

Among the featured topics: oncolytic immunotherapy, BRAF/MEK inhibition, and a programmed death-1 inhibitor at the Society for Melanoma Research; and anticoagulation therapy, an alternative to statins, and endocarditis in the absence of dental antibiotic prophylaxis at the American Heart Association Scientific Sessions.

Targeting mTOR signaling pathways and related negative feedback loops for the treatment of acute myeloid leukemia

An accumulating understanding of the complex pathogenesis of acute myeloid leukemia (AML) continues to lead to promising therapeutic approaches. Among the key aberrant intracellular signaling pathways involved in AML, the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) axis is of major interest. This axis modulates a wide array of critical cellular functions, including proliferation, metabolism, and survival. Pharmacologic inhibitors of components of this pathway have been developed over the past decade, but none has an established role in the treatment of AML. This review will discuss the preclinical data and clinical results driving ongoing attempts to exploit the PI3K/AKT/mTOR pathway in patients with AML and address issues related to negative feedback loops that account for leukemic cell survival. Targeting the PI3K/AKT/mTOR pathway is of high interest for the treatment of AML, but combination therapies with other targeted agents may be needed to block negative feedback loops in leukemia cells.

Achievements and challenges of molecular targeted therapy in melanoma

The treatment of melanoma has been revolutionized over the past decade with the development of effective molecular and immune targeted therapies. The great majority of patients with melanoma have mutations in oncogenes that predominantly drive signaling through the mitogen activated protein kinase (MAPK) pathway. Analytic tools have been developed that can effectively stratify patients into molecular subsets based on the identification of mutations in oncogenes and/or tumor suppressor genes that drive the MAPK pathway. At the same time, potent and selective inhibitors of mediators of the MAPK pathway such as RAF, MEK, and ERK have become available. The most dramatic example is the development of single-agent inhibitors of BRAF (vemurafenib, dabrafenib, encorafenib) and MEK (trametinib, cobimetinib, binimetinib) for patients with metastatic BRAFV600-mutant melanoma, a subset that represents 40% to 50% of patients with metastatic melanoma. More recently, the elucidation of mechanisms underlying resistance to single-agent BRAF inhibitor therapy led to a second generation of trials that demonstrated the superiority of BRAF inhibitor/MEK inhibitor combinations (dabrafenib/trametinib; vemurafenib/cobimetinib) compared to single-agent BRAF inhibitors. Moving beyond BRAFV600 targeting, a number of other molecular subsets--such as mutations in MEK, NRAS, and non-V600 BRAF and loss of function of the tumor suppressor neurofibromatosis 1 (NF1)--are predicted to respond to MAPK pathway targeting by single-agent pan-RAF, MEK, or ERK inhibitors. As these strategies are being tested in clinical trials, preclinical and early clinical trial data are now emerging about which combinatorial approaches might be best for these patients.

The role of chemotherapy in the modern management of melanoma

The last 4 years have seen dramatic changes in the treatment of advanced melanoma, largely based on advances in targeted therapy and immunotherapy. This article examines the role of chemotherapy in the modern management of melanoma. We examine the evidence for promising new agents and discuss their position in the sequencing of treatment options for patients with advanced disease. In addition, we discuss the combination of chemotherapy with targeted treatments and immune therapies. Finally, we discuss future areas of research for ensuring that we maximize the potential of all agents available to us and identify new, effective treatments.