BRAF and MEK inhibition for the treatment of advanced BRAF mutant melanoma

Introduction: BRAF inhibition alone has achieved unprecedented efficacy results in patients affected by BRAF-mutated advanced melanoma. Since these findings, it was postulated that dual inhibition of BRAF and other components of the RAS/RAF/MEK/ERK MAPK pathway (such as MEK) would be superior to BRAF inhibition as monotherapy. A series of recent clinical trials have confirmed this hypothesis.

Areas covered: In this article, the biological rationale for both single and concomitant inhibitions of the MAPK pathway in BRAF mutant melanoma is provided. Moreover, available clinical data on the efficacy and toxicity of BRAF and MEK inhibition as single agents and in combination are extensively reviewed.

Expert opinion: Dual BRAF and MEK inhibition in advanced BRAF-mutated melanoma is superior to single inhibition in terms of efficacy without significant increase in toxicity. Therefore, BRAF plus MEK inhibition is expected to supersede single-agent BRAF inhibition in these patients in the near future.     

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.     

Encorafenib in combination with binimetinib for unresectable or metastatic melanoma with BRAF mutations

Introduction: Combination treatment with a BRAF inhibitor and MEK inhibitor is the standard of care for patients with advanced BRAF^V600 mutation-positive melanoma. With the currently available combinations of dabrafenib plus trametinib and vemurafenib plus cobimetinib, median progression-free survival (PFS) of over 12 months has been achieved. However, treatment resistance and disease recurrence remain a clinical challenge.

Areas covered: Encorafenib in combination with bimetinib offers a new approach that may offer benefits over existing BRAF/MEK inhibitor combinations.

Expert opinion: While other BRAF/MEK inhibitor combinations have achieved a median overall survival (OS) of 22 months, patients with advanced BRAF mutation-positive melanoma treated with encorafenib plus binimetinib achieved a median OS of 33.6 months in the phase III COLUMBUS trial. PFS also appears to be improved with encorafenib plus binimetinib. This improved efficacy may be related to the distinct pharmacokinetics of encorafenib, with prolonged binding to the target molecule providing greater BRAF inhibition and increased potency compared with other drugs in the same class. Increased specificity of encorafenib may also result in better tolerability with less off-target effects, including reduced occurrence of pyrexia and photosensitivity. Encorafenib plus binimetinib seems likely to emerge as a valuable therapeutic alternative to established BRAF/MEK inhibitor combinations.     

Future of combination therapy with dabrafenib and trametinib in metastatic melanoma

Introduction: Combination therapy with BRAF and MEK inhibitors is a recommended treatment strategy for metastatic melanoma patients with BRAF^V600 mutations. This treatment provides significant response rates and little added toxicity, with relatively improved survival outcomes compared to RAF/MEK inhibitor monotherapy and chemotherapy.

Areas covered: This review covers the pharmacology, efficacy, and toxicity data derived from clinical studies of dabrafenib, trametinib, and the combination thereof. The major downfall of combiDT is the limited durability of response, which is largely due to acquired resistance in the MAPK pathway.

Expert opinion: Future directions of combiDT concentrate on further combinations with immunotherapy or other targeted inhibitors, referred to triple-agent therapy, which may be essential to improving durability of responses and overcoming resistance.     

The safety and efficacy of dabrafenib and trametinib for the treatment of melanoma

Introduction: The introduction of BRAF and MEK inhibitors into clinical practice improved the prognosis of metastatic melanoma patients. The combination of BRAF inhibitor dabrafenib with MEK inhibitor trametinib has shown its superiority to single agent therapy and is characterized by a tolerable spectrum of adverse events which shows a decrease in incidence over time on treatment.

Areas covered: The current scientific literature on safety and adverse events (AEs) related to BRAF and MEK-inhibition has been investigated with special focus on the large phase 3 studies (COMBI-v, COMBI-d and CoBRIM) as well as recent updates presented at oncology and melanoma meetings. Additionally, published case series/case reports were screened for information on AEs.

Expert opinion: Even though almost every patient (98%) under combination therapy with dabrafenib and trametinib experiences at least one adverse event, these are generally mild to moderate, reversible and can be managed with dose reductions or interruptions. However, due to an increased life expectancy, there is a substantial need to prevent and treat also mild adverse events, as they play a central role for the quality of life of patients. Ongoing clinical trials will have to demonstrate the efficacy as well as safety of triple combination with anti-PD-1/anti-PD-L1 antibodies.     

Dabrafenib for the treatment of melanoma

Introduction: Approximately 50% of patients with cutaneous melanoma have an activating mutation in BRAF kinase, leading to constitutive activation of the mitogen-activated protein kinase pathway and unregulated cell growth. Selective inhibitors of the mutated BRAF kinase produce response rates of approximately 50% with median progression-free survival of 6 – 7 months. BRAF-blocking therapies work rapidly, with responses seen within 2 weeks after therapy initiation, and they are associated with generally mild toxicities. The BRAF inhibitor dabrafenib recently was approved for use in patients with BRAF V600-mutated metastatic melanoma.

Areas covered: This article discusses the mechanisms of action and pharmacokinetic and pharmacodynamic changes as well as clinical efficacy and safety of dabrafenib for treatment of patients with advanced melanoma including unresectable stage IIIc and stage IV patients who harbor a BRAF V600 mutation. Clinical trial data are reviewed, and efficacy of dabrafenib in patients with brain metastases and in combination with the MEK inhibitor trametinib is discussed.

Expert opinion: Despite rapid and significant tumor reduction in a majority of patients with BRAF-mutant metastatic melanoma who are treated with dabrafenib, this drug’s use as a single agent is limited because of its relatively short duration of response. Various combinations with drug(s) inhibiting other target kinases and/or with immunomodulating agent(s) will likely be the standard in the near future.     

曲美替尼联合达拉非尼对比维莫非尼治疗伴有BRAF V600突变的转移性黑色素瘤的成本-效用分析

目的: 对曲美替尼联合达拉非尼对比维莫非尼一线治疗伴有BRAF V600突变的不可切除或转移性黑色素瘤进行药物经济学评价,为我国医疗卫生决策提供参考。方法: 从卫生体系角度出发,结合Combi-v研究和针对东亚人群进行的临床试验中的患者生存数据,建立马尔可夫模型模拟伴有BRAF V600突变的不可切除或转移性黑色素瘤患者10年的疾病进展情况,模型循环周期为1个月,贴现率为5%,收集成本为直接医疗成本。采用单因素敏感性分析和概率敏感性分析对基础分析结果的稳健性进行验证。结果: 达拉非尼和曲美替尼联合疗法与维莫非尼单药疗法的增量-成本效用比(ICUR)为22 117.06元/质量调整生命年(QALY)。敏感性分析表明基础分析结果可靠。结论: 在意愿支付阈值(WTP)为1倍中国人均GDP时,达拉非尼联合曲美替尼治疗伴有BRAF V600突变的转移性黑色素瘤患者十分具有经济性。     

The risk of dermatological toxicities of combined BRAF and MEK inhibition versus BRAF inhibition alone in melanoma patients: a systematic review and meta-analysis

Background: This meta-analysis was conducted to assess the risk of dermatological toxicities of combined BRAF and MEK inhibition versus BRAF inhibition alone in melanoma patients.

Methods: We considered relevant prospective randomized phase I, II, and III trials of melanoma patients on the combined BRAF and MEK inhibition versus BRAF inhibition, describing events of rash, photosensitivity reaction (PR), hyperkeratosis (HK), alopecia, cutaneous squamous-cell carcinom(cSCC), skin papilloma(SP), pruritus, and hand-foot syndrome(HFS), as eligible for inclusion.

Results: Eight trials comprising 3163 patients were included in the meta-analysis. The relative risks(RRs) of developing all-grade rash with combined BRAF and MEK inhibition versus BRAF inhibition was 1.59 (95%CI, 1.35–1.86, p?p?=?0.002), SP 0.09(95%CI, 0.04–0.24, p?p?p?p?p?p?=?0.21), HK 0.18(95%CI, 0.06–0.53, p?=?0.002), SP 0.14(95%CI, 0.02–1.16, p?=?0.07), alopecia 0.72(95%CI, 0.14–3.62, p?=?0.69), cSCC 0.23(95%CI, 0.17–0.33, p?<?0.00001), HFS 0.40(95%CI, 0.08–2.06, p?=?0.27), and PR 0.14(95%CI, 0.04–0.51, p?=?0.003), respectly.

Conclusion: Our analysis of data has demonstrated that combined BRAF and MEK inhibitor-based treatment is associated with an increased risk of all-grade rash and a decreased risk of all-grade and high-grade HK, SP, alopecia, cSCC, HFS, and PR compared with single BRAF inhibitor alone in melanoma patients. Appropriate prevention and management are recommended.     

Emerging targeted therapies for melanoma

Introduction: Melanoma is an aggressive cutaneous malignancy associated with poor response to traditional therapies. Recent regulatory approval for immune checkpoint inhibitors and agents targeting mutated BRAF has led to a tremendous expansion of effective treatment options for patients with advanced melanoma. Unfortunately, primary or acquired resistance develops in most patients, highlighting the need for additional therapies. Numerous genetic and other molecular features of this disease may provide effective targets for therapy development.

Areas covered: This article reviews available melanoma treatments, including immune and molecularly-targeted therapies. We then discuss agents in development, with a focus on targeted (rather than immune) therapies. In particular, we discuss agents that block mitogen-activated protein kinase (MAPK) signaling, as well as other emerging approaches such as antibody-drug conjugates, cell-cycle targeting, and novel genetically-informed clinical trials.

Expert opinion: Despite the incredible advances in melanoma therapeutics over the last several years, a clear need to develop more effective therapies remains. Molecularly-targeted therapy approaches will likely remain a cornerstone of melanoma treatment in parallel to immune therapy strategies.     

Acquired and intrinsic BRAF inhibitor resistance in BRAF V600E mutant melanoma

The discovery of activating BRAF V600E mutations in 50% of all cutaneous melanomas has revolutionized the understanding of melanoma biology and provided new strategies for the therapeutic management of this deadly disease. Highly potent small molecule inhibitors of BRAF are now showing great promise as a novel therapeutic strategy for melanomas harboring activating BRAF V600E mutations and are associated with high levels of response. This commentary article discusses the latest data on the role of mutated BRAF in the development and progression of melanoma as the basis for understanding the mechanism of action of BRAF inhibitors in the preclinical and clinical settings. We further address the issue of BRAF inhibitor resistance and outline the latest insights into the mechanisms of therapeutic escape as well as describing approaches to prevent and abrogate the onset of both intrinsic and acquired drug resistance. It is likely that our evolving understanding of melanoma genetics and signaling will allow for the further personalization of melanoma therapy with the goal of improving clinical responses.     

Current and emerging systemic therapies for cutaneous metastatic melanoma

Introduction: Melanoma therapies have evolved rapidly, and initial successes have translated into survival gains for patients with advanced melanoma. Both targeted and immune-therapy now have evidence in earlier stage disease. There are many new agents and combinations of treatments in development as potential future treatment options. This highlights the need for a reflection on current treatment practice trends that are guiding the development of potential new therapies.

Areas covered: In this review, the authors discuss the evidence for currently approved therapies for cutaneous melanoma, including adjuvant therapy, potential new biomarkers, and emerging treatments with early phase clinical trial data. The authors have searched both the PubMed and clinicaltrials.gov databases for published clinical trials and discuss selected landmark trials of current therapies and of investigational treatment strategies with early evidence for the treatment of melanoma.

Expert opinion: Significant efficacy has been demonstrated with both immune checkpoint inhibitors and targeted therapies in treating advanced melanoma. A multitude of novel therapies are in development and there is need for instructive biomarker assessment to identify patients likely to respond or be refractory to current therapies, to identify mechanisms of resistance and to direct further treatment options to patients based on individual disease biology.     

BRAF kinase inhibitors for treatment of melanoma: developments from early-stage animal studies to Phase II clinical trials

Introduction: Approximately, 30.4–66.0% of cutaneous melanomas possess a mutation in the BRAF gene that activates downstream signaling through the mitogen-activated protein (MAP) kinase pathway; this provides an attractive target for the treatment of advanced melanoma. Although BRAF inhibitors rapidly suppress melanoma growth, median progression-free survival remains unsatisfactory. Recent clinical trials have investigated drugs that can optimally enhance and prolong the anti-melanoma effects of BRAF inhibitors.

Area covered: This review discusses the development of BRAF inhibitor-based combination therapies for BRAF-mutant advanced melanoma.

Expert opinion: Future strategies for the treatment of advanced melanoma include novel combination therapies using BRAF/MEK inhibitors and immune checkpoints inhibitors or histone deacetylase inhibitors. These combination therapies might enhance antitumor responses against melanoma, prolonging survival in advanced melanoma patients. Further clinical studies are needed to optimize these novel combination therapies.     

MEK inhibitors under development for treatment of non-small-cell lung cancer

Introduction: The mitogen-activated protein kinase (MAPK) pathway is intimately implicated in the molecular pathogenesis of non-small-cell lung cancer (NSCLC). Aberrant MAPK signaling resulting from the upstream activating mutations converges on mitogen-activated protein kinase kinase 1/2 (MEK1/2), making MEK inhibition an attractive strategy for the treatment of NSCLC. Several MEK inhibitors have demonstrated anticancer activity in patients with NSCLC.

Areas covered: In this article, we discuss the biological rationale for the use of MEK inhibitors and summarize the clinical experience with MEK1/2 inhibitors for the treatment of NSCLC, from initial phase I studies to phase II/III studies, both as monotherapy or in combination with other anticancer agents.

Expert opinion: Trametinib in combination with the BRAF inhibitor dabrafenib represents the first MEK1/2 inhibitor containing regimen that is approved for advanced BRAF^V600E-mutant NSCLC. Other MEK1/2 inhibitors that are also in advanced stages of clinical development include selumetinib, cobimetinib, and binimetinib. Several studies of MEK inhibitor combination therapies are underway, including trials using combined MEK inhibition and immune checkpoint blockade. Further research aimed at discovering biomarkers of response and resistance to MEK1/2 inhibitors will be needed to develop rational combination strategies for the treatment of NSCLC driven by aberrant MAPK signaling.     

Combination dabrafenib and trametinib in the management of advanced melanoma with BRAFV600 mutations

Introduction: In the 40–50% of advanced melanoma patients with tumors harboring BRAF V600E and V600 K mutations, BRAF inhibitors such as dabrafenib are a highly effective treatment. However, most patients develop resistance after several months on treatment. The addition of a MEK inhibitor, such as trametinib, to BRAF inhibition mitigates one key pathway of resistance, further increasing response rates and improving survival.

Areas covered: This article summarizes the mechanism of action of the combination of dabrafenib and trametinib, its evolution through Phase I, II and III clinical trials and discusses its current use in the management of patients with advanced melanoma.

Expert opinion: Combination therapy with dabrafenib and trametinib improves response rate, progression-free survival and overall survival when compared to dabrafenib or vemurafenib alone. The addition of trametinib to dabrafenib changes the adverse event profile, making hyperkeratosis and cutaneous squamous cell carcinomas less common but side effects such as fever and nausea more common. How dabrafenib/trametinib is best sequenced with other effective treatments such as immune checkpoint blockade remains uncertain.     

An overview of binimetinib for the treatment of melanoma

ABSTRACT

Introduction

Approximately 50% of patients with metastatic melanoma have mutations in BRAF. Based on the results of prior phase III trials, the combination of a BRAF inhibitor (BRAFi) and a MEK inhibitor (MEKi) is the standard of care in patients with BRAF-mutant metastatic melanoma.     

BRAF and MEK inhibitors in pediatric glioma: new therapeutic strategies,new toxicities

Introduction: BRAF mutation was initially reported in metastatic melanomas, and more recently in a variety of human cancers. BRAF acts as a down-stream effector of growth factor signaling leading to cell cycle progression, proliferation and survival. Development of selective inhibitors of BRAF has improved the survival of patients with melanoma and offers potential new therapeutic strategy in children with BRAF-mutant glioma.

Areas covered: Mechanisms of resistance to BRAF inhibitors have recently been described as due to the paradoxical activation of the MAPK pathway. Combination therapy with BRAF and MEK inhibition has proved capable of overcoming the resistance with effective results in patients with melanoma. Prospective studies in pediatric glioma are warranted. Combination therapy has a different toxicity profile compared to BRAF inhibitor alone. Herein we review the state-of-the-art of toxicities associated with these agents, with a special focus on children.

Expert opinion: Some toxicities appear more specific to adults, due to a combination of factors, such as patient age and predisposing risk factors. Moreover, it is recommended that the co-administration of BRAF inhibitors and drugs metabolized by the cytochrome P450 system in the liver be avoided, as this can lead to significant complications secondary to pharmacological interactions.     

Cobimetinib and vemurafenib for the treatment of melanoma

Introduction: Cobimetinib combined with vemurafenib is a new approved MEK inhibitor for first line treatment of metastatic melanoma patients with BRAF V600 mutations. It improves tumor response rates and progression free survival compared to vemurafenib alone, while decreasing toxicities due to the paradoxical activation of the MAPK signaling pathway.

Areas covered: This review covers the pharmacology, efficacy, and toxicity data derived from clinical and preclinical studies on cobimetinib. It also reports ongoing trials evaluating cobimetinib to better understand future developments for this drug.

Expert opinion: The combination of cobimetinib and vemurafenib seems to be more toxic than the combination therapy dabrafenib and trametinib even if these four drugs have never been compared in a randomized trial. The future of this combination depends on its capacity to be combined simultaneously or sequentially with immune based therapies to improve the durability of responses.     

The discovery of vemurafenib for the treatment of BRAF-mutated metastatic melanoma

ABSTRACT

Introduction: In the era of precision medicine and sophisticated modern genetics, the discovery of the BRAF^V600 inhibitor, vemurafenib, quickly became the model for targeted therapy in melanomas. As early as 2002, the majority of metastatic melanomas were described to harbor the BRAF^V600 mutation, setting the stage for an explosion of interest for targeting this protein as a novel therapeutic strategy. The highly selective BRAF^V600 inhibitor, vemurafenib, was identified initially through a large-scale drug screen.

Areas covered: Here we examine vemurafenib’s journey from discovery to clinical use in metastatic melanoma. Topics covered include preclinical data, single agent Phase 1,2 and 3 clinical trials, resistance issues and mechanisms, adverse effects including the development of squamous cell cancers, and combination trials.

Expert opinion: Due to its tolerance, low toxicity profile, rapid tumor response, and improved outcomes in melanoma patients with BRAF^V600 mutations, vemurafenib was advanced rapidly through clinical trials to receive FDA approval in 2011. While its efficacy is well documented, durability has become an issue for most patients who experience therapeutic resistance in approximately 6–8 months. In addition, a concerning toxicity observed in patients taking the drug include development of localized cutaneous squamous cell carcinomas (SCCs). It is hypothesized that drug resistance and SCC development result from a similar paradoxical activation of protein signaling pathways, specifically MAPK. Identification of these mechanisms has led to additional treatment strategies involving new combination therapies.     

MicroRNA expression in BRAF-mutated and wild-type metastatic melanoma and its correlation with response duration to BRAF inhibitors

Objective: Currently, the treatment of BRAF V600-mutated metastatic melanoma with BRAF inhibitors gives a response rate of ～ 50% with a progression-free survival of ～ 6 – 7 months. In order to identify predictive biomarkers capable of stratifying BRAF-mutated patients at high risk of shorter response duration to anti-BRAF therapy, the authors analyzed the expression of 15 microRNAs (miRNAs) targeting crucial genes involved in melanoma biology and drug response.

Research design and methods: A total of 15 miRNAs and target gene expression were investigated in 43 patients (30 BRAF-mutated, and 13 BRAF wild-type). Moreover, 20 BRAF-mutated patients treated with vemurafenib were analyzed for miRNA expression in respect to time-to-progression.

Results: All miRNAs except miR-192 showed low expression in BRAF-mutated as compared with BRAF wild-type patients. In particular, miR-101, miR-221, miR-21, miR-338-3p and miR-191 resulted in significant downregulation in BRAF-mutated patients. Moreover, high expression of miR-192 and miR-193b* and low expression of miR-132 resulted in significant association with shorter progression.

Conclusion: Three miRNAs were significantly associated with clinical outcome in metastatic melanoma patients. An increased understanding of the molecular assessment of BRAF-mutated melanomas could allow development of specific molecular tests able to predict response duration.     

Dabrafenib for the treatment of BRAF V600-positive melanoma: a safety evaluation

Introduction: V-raf murine sarcoma viral oncogene homolog B1 (BRAF) inhibitors are emerging as the standard of care for treating advanced melanomas harboring the BRAF V600 oncogenic mutation. Dabrafenib is the second approved selective BRAF inhibitor (after vemurafenib) for the treatment of unresectable or metastatic BRAF V600-positive melanoma.

Areas covered: This review covers the current data on the efficacy and safety of the selective BRAF inhibitor dabrafenib in patients with metastatic BRAF V600 positive melanoma. The pharmacological, safety and efficacy data are discussed from Phase I, II, and III studies of dabrafenib monotherapy as well as in combination with the MEK inhibitor trametinib.

Expert opinion: Dabrafenib has demonstrated comparable efficacy to vemurafenib in BRAF V600E mutant melanoma patients. Dabrafenib is well tolerated in patients with metastatic melanoma, including patients with brain metastases. Nevertheless side effects are common, but usually manageable. In the Phase III study testing dabrafenib, 53% of patients reported grade 2 or higher adverse events (AEs). Toxicities were similar to those seen in the early-phase trials, with the most common being cutaneous manifestations (hyperkeratosis, papillomas, palmar-plantar erythrodysesthesia), pyrexia, fatigue, headache, and arthralgia. Combining a BRAF inhibitor with a MEK inhibitor, which may block paradoxical MAPK activation in BRAF wild type (skin) cells, may lower the incidence of squamoproliferative eruptions.