Dabrafenib in BRAF-mutated metastatic melanoma: a multicentre, open-label, phase 3 randomised controlled trial

Drug monographs: dabrafenib and trametinib

The complexity of cancer chemotherapy requires pharmacists be familiar with the complicated regimens and highly toxic agents used. This column reviews various issues related to preparation, dispensing, and administration of antineoplastic therapy, and the agents, both commercially available and investigational, used to treat malignant diseases. Questions or suggestions for topics should be addressed to Dominic A. Solimando, Jr, President, Oncology Pharmacy Services, Inc., 4201 Wilson Blvd #110-545, Arlington, VA 22203, e-mail: OncRxSvc@aol.comcast.net; or J. Aubrey Waddell, Professor, University of Tennessee College of Pharmacy; Oncology Pharmacist, Pharmacy Department, Blount Memorial Hospital, 907 E. Lamar Alexander Parkway, Maryville, TN 37804, e-mail: waddfour@charter.net.

Activating mutations cluster in the "molecular brake" regions of protein kinases and do not associate with conserved or catalytic residues

Mutations leading to activation of proto-oncogenic protein kinases (PKs) are a type of drivers crucial for understanding tumorogenesis and as targets for antitumor drugs. However, bioinformatics tools so far developed to differentiate driver mutations, typically based on conservation considerations, systematically fail to recognize activating mutations in PKs. Here, we present the first comprehensive analysis of the 407 activating mutations described in the literature, which affect 41 PKs. Unexpectedly, we found that these mutations do not associate with conserved positions and do not directly affect ATP binding or catalytic residues. Instead, they cluster around three segments that have been demonstrated to act, in some PKs, as "molecular brakes" of the kinase activity. This finding led us to hypothesize that an auto inhibitory mechanism mediated by such "brakes" is present in all PKs and that the majority of activating mutations act by releasing it. Our results also demonstrate that activating mutations of PKs constitute a distinct group of drivers and that specific bioinformatics tools are needed to identify them in the numerous cancer sequencing projects currently underway. The clustering in three segments should represent the starting point of such tools, a hypothesis that we tested by identifying two somatic mutations in EPHA7 that might be functionally relevant.

Inter- and intra-patient heterogeneity of response and progression to targeted therapy in metastatic melanoma

Background

MAPK inhibitors (MAPKi) are active in BRAF-mutant metastatic melanoma patients, but the extent of response and progression-free survival (PFS) is variable, and complete responses are rare. We sought to examine the patterns of response and progression in patients treated with targeted therapy.

Methods

MAPKi-naïve patients treated with combined dabrafenib and trametinib had all metastases ≥5 mm (lymph nodes ≥15 mm in short axis) visible on computed tomography measured at baseline and throughout treatment.

Results

24 patients had 135 measured metastases (median 4.5/patient, median diameter 16 mm). Time to best response (median 5.5 mo, range 1.7–20.1 mo), and the degree of best response (median −70%, range +9 to −100%) varied amongst patients. 17% of patients achieved complete response (CR), whereas 53% of metastases underwent CR, including 42% ≥10 mm. Metastases that underwent CR were smaller than non-CR metastases (median 11 vs 20 mm, P<0.001). PFS was variable among patients (median 8.2 mo, range 2.6–18.3 mo), and 50% of patients had disease progression in new metastases only. Only 1% (1/71) of CR-metastases subsequently progressed. Twelve-month overall survival was poorer in those with a more heterogeneous initial response to therapy than less heterogeneous (67% vs 93%, P = 0.009).

Conclusion

Melanoma response and progression with MAPKi displays marked inter- and intra-patient heterogeneity. Most metastases undergo complete response, yet only a small proportion of patients achieve an overall complete response. Similarly, disease progression often occurs only in a subset of the tumor burden, and often in new metastases alone. Clinical heterogeneity, likely reflecting molecular heterogeneity, remains a barrier to the effective treatment of melanoma patients.

Molecular profiling and commercial predication assays in ovarian cancer: still not ready for prime time?

Short of early detection to allow curative primary intervention, the other major barrier to further success in treatment of ovarian cancers is matching the best treatment to the proper ovarian cancer type and to the individual patient. There are several decades of experience applying in vitro chemoresponse testing for solid tumors including ovarian cancer. This concept, first described in 1979, has yet to receive level one evidence supporting its application, despite the testing of numerous assays commercially as well as in academic centers and its use for tens of thousands of patients at a significant cost. The approach-rather than undergoing rigorous scientific examination-is now being muddied by the development of commercial molecular profiling assays from which treatment suggestions are provided. Molecular profiling as a research tool has added value to our understanding and treatment of patients with ovarian cancer. Morphologic and histochemical characterizations coupled now with increasing knowledge of ovarian cancer type-specific molecular patterns is improving our ability to properly diagnosis ovarian cancer type and thus guide therapy. With the exception of the role of germ-line and possibly somatic BRCA1 and BRCA2 mutations and their true predictiveness for probable response to poly(ADP-ribose) polymerase inhibition, molecular typing and profiling has yet to identify druggable molecular targets in ovarian cancer. Its use should be continued as a research and learning tool, and its results should be subjected to clinical trial validation. For very different reasons, neither chemoresponse assays nor molecular profiling are ready for prime time, yet.

Frontline approach to metastatic BRAF-mutant melanoma diagnosis, molecular evaluation, and treatment choice

An estimated 76,100 patients will be diagnosed with invasive melanoma in the United States in 2014, and 9,710 patients will die from the disease. In almost all cases, the cause of death is related to the development of widespread metastatic disease. Although death rates from most types of cancer have steadily decreased in the United States--a 20% decrease during two decades from a peak of 215.1 deaths per 100,000 population in 1991 to 171.8 in 2010--death rates from melanoma have steadily increased during the same time, especially among males. The news regarding melanoma is far from all bad. Increases in our understanding of the human immune system have led to the development of new immunotherapeutic drugs such as ipilimumab, which has been shown to improve survival in phase III trials in metastatic melanoma, and anti-programmed death 1 (anti-PD1) antibodies, recently hailed by ASCO as one of the past year's most noteworthy clinical cancer advances. However, no discovery has influenced and, indeed, transformed the management of metastatic melanoma more than the identifıcation of activating mutations in the BRAF gene in the mitogen-activated protein kinase (MAPK) pathway, which occur in about half of cutaneous melanomas and can be targeted with small molecule inhibitors of the BRAF protein, the downstream MEK protein, or both. This article will address how patients with metastatic melanoma are evaluated for their mutation status and how the presence of a targetable mutation influences therapeutic decisions regarding systemic therapy and even surgery.

Marker utility for combination therapy

Melanoma is a heterogeneous disease for which monotherapies are likely to fail in the majority of patients due to genomic variations between individuals. Novel treatments, such as vemurafenib and ipilimumab, offer clinical promise in metastatic melanoma and the increased potential for combined therapeutic strategies, necessary given the differences in response between patients. Together with these new approaches, the development of clinically relevant biomarkers that predict treatment outcomes are required to ensure these new therapies are targeted at those patients most likely to benefit. Here we review the utility of some potential biomarkers of treatment response in patients with metastatic melanoma.

Targeted therapies in brain metastases

OPINION STATEMENT

Brain metastases are a major clinical problem in patients with advanced breast cancer, lung cancer, melanoma, and renal cell carcinoma. Initial treatment for patients with brain metastases typically includes radiotherapy, either whole brain radiotherapy (WBRT), stereotactic radiosurgery (SRS), or both. Surgical resection is generally reserved for good prognosis patients with limited/controlled extracranial metastases and a single brain lesion. Once patients progress through upfront treatment, the treatment approach is quite variable and there is no clearly defined standard-of-care. Over the past decade, the role of systemic therapies and in particular, targeted therapies has been increasingly explored in patients with brain metastases from solid tumors. For example, lapatinib has been studied as monotherapy, and in combination with capecitabine, in patients with HER2-positive breast cancer, and activity has been observed in both the upfront and refractory settings. In patients with nonsmall cell lung cancer (NSCLC), central nervous system (CNS) activity has been reported with gefinitib and erlotinib. Finally, in melanoma, the B-raf inhibitors vemurafenib and dabrafenib, and the immunomodulator, ipilumimab, have reported CNS activity. Moving forward, the challenge will be to understand how to optimize the activity of targeted agents in the CNS and how to best incorporate them into the current treatment paradigms in order to improve outcomes for this patient population.

Dabrafenib

Dabrafenib was developed as a highly specific reversible inhibitor of V600-mutant BRAF kinase, an oncogenic mutation driving proliferation in many different types of aggressive tumors. Metastatic melanoma has a high prevalence of V600-mutant BRAF, and clinical trials showed that dabrafenib improved response rates and median progression-free survival in patients with V600E BRAF mutations, including those with brain metastasis. Preliminary results suggest that dabrafenib may also have some role in non-melanoma V600-mutant solid tumors; however, more studies are needed. With a well-tolerated toxicity profile and few drug interactions, dabrafenib is effective as a monotherapy; however, resistance eventually develops in most patients after persistent exposure to the drug. Current research focuses on combination strategies with dabrafenib to not only improve response rates but also overcome resistance.

Advances in adjuvant therapy: potential for prognostic and predictive biomarkers

Melanoma is the third most common skin cancer but accounts for the majority of skin cancer-related mortality. The rapidly rising incidence and younger age at diagnosis has made melanoma a leading cause of lost productive years of life and has increased the urgency of finding improved adjuvant therapy for melanoma. Interferon-α was approved for the adjuvant treatment of resected high-risk melanoma following studies that demonstrated improvements in relapse-free survival and overall survival that were commenced nearly 30 years ago. The clinical benefits associated with this agent have been consistently observed across multiple studies and meta-analyses in terms of relapse rate, and to a smaller and less-consistent degree, mortality. However, significant toxicity and lack of prognostic and/or predictive biomarkers that would allow greater risk-benefit ratio have limited the more widespread adoption of this modality.Recent success with targeted agents directed against components of the MAP-kinase pathway and checkpoint inhibitors have transformed the treatment landscape in metastatic disease. Current research efforts are centered around discovering predictive/prognostic biomarkers and exploring the options for more effective regimens, either singly or in combination.

Integrating molecular biomarkers into current clinical management in melanoma

Personalized melanoma medicine has progressed from histopathologic features to serum markers to molecular profiles. Since the identification of activating BRAF mutations and subsequent development of drugs targeting the mutant BRAF protein, oncologists now need to incorporate prognostic and predictive biomarkers into treatment decisions for their melanoma patients. Examples include subgrouping patients by genotype profiles for targeted therapy and the development of serologic, immunohistochemical, and genotype profiles for the selection of patients for immunotherapies. In this chapter, we provide an overview of the current status of BRAF mutation testing, as well as promising serologic and molecular profiles that will impact patient care. As further research helps clarify the roles of these factors, the clinical outcomes of melanoma patients promise to be greatly improved.

Novel insights/translational implication from the emerging biology of melanoma

Melanoma is a main example of how applying advances in basic biology, pharmacology, and molecular diagnostics into the clinic results in unprecedented benefits to patients. After many years of lack of advances in the treatment of patients with metastatic melanoma, the advent of new therapies that block driver oncogenic signaling and modulate immune responses to cancer provided the first studies with a positive impact in overall survival (OS) of patients with advanced melanoma. The pace of progress in the treatment of this disease has been greatly accelerated by these initial breakthroughs, and it continues with new generation agents and combinatorial approaches.

Detecting mechanisms of acquired BRAF inhibitor resistance in melanoma

(V600)BRAF mutation was identified as an ideal target for clinical therapy due to its indispensable roles in supporting melanoma initiation and progression. Despite the fact that BRAF inhibitors (BRAFi) can elicit anti-tumor responses in the majority of treated patients and confer overall survival benefits, acquired drug resistance is a formidable obstacle to long-term management of the disease. Several aberrant events including RTK upregulation, NRAS mutation, mutant BRAF amplification or alternative splicing, and MEK mutation have been reported as acquired BRAFi resistance mechanisms. Clinially, detection of these resistance mechanisms help understand drug response patterns and help guide combinatorial therapeutic strategies. Therefore, quick and accurate diagnosis of the resistant mechanisms in tumor biopsies has become an important starting point for personalized therapy. In this chapter, we review the major acquired BRAFi resistance mechanisms, highlight their therapeutic implications, and provide the diagnostic methods from clinical samples.

Dabrafenib for treatment of BRAF-mutant melanoma

Melanoma has the highest mortality of all the skin cancer subtypes. Historically, chemotherapy and immunologic therapies have yielded only modest results in the treatment of metastatic melanoma. The discovery of prevalent V600 BRAF mutations driving proliferation makes this oncogenic protein an ideal target for therapy. Dabrafenib, a reversible inhibitor of mutant BRAF kinase, improved response rates and median progression-free survival in patients with V600E BRAF-mutant metastatic melanoma, including those with brain metastases. With a well-tolerated toxicity profile, dabrafenib is effective as a monotherapy; however, resistance eventually develops in almost all patients. As a result, current research is exploring the role of combination therapies with dabrafenib to overcome resistance.

[What’s new in dermato-oncology?]

During this year 2013, Onco-dermatology was the object of numerous publications, especially in the field of metastatic melanoma. Previous results concerning anti PD-1 have been consolidated. Studies concerning Mek inhibitors have been published with promising results in uveal melanoma. In metastatic melanoma two combinations showed great results: combination of ipilimumab and nivolumab and combination of B-RAF and MEK inhibitors. Some studies demonstrated efficacy of these new therapeutics (ipilimumab, vemurafenib and dabrafenib) in brain metastasis. Moreover, the year 2013 was marked by the increasing knowledge in the management of adverse events induced by these new treatments. In the field of basal cell carcinoma, after the publication of large scale studies, vismodegib, the inhibitor of the hedgehog signalling pathway, was approved by the European Medicines Agency.

Malignant Melanoma

Melanomas are a major cause of premature death from cancer. The gradual decrease in rates of morbidity and mortality has occurred as a result of public health campaigns and improved rates of early diagnosis. Survival of melanoma has increased to over 90%. Management of melanoma involves a number of components: excision, tumor staging, re-excision with negative margins, adjuvant therapies (chemo, radiation or surgery), treatment of stage IV disease, follow-up examination for metastasis, lifestyle modification and counseling. Sentinel lymph node status is an important prognostic factor for survival in patients with a melanoma >1 mm. However, sentinel lymph node biopsies have received partial support due to the limited data regarding the survival advantage of complete lymph node dissection when a micrometastasis is detected in the lymph nodes. Functional mutations in the mitogen-activated pathways are commonly detected in melanomas and these influence the growth control. Therapies that target these pathways are rapidly emerging, and are being shown to increase survival rates in patients. Access to these newer agents can be gained by participation in clinical trials after referral to a multidisciplinary team for staging and re-excision of the scar.

Interferon alpha for the adjuvant treatment of melanoma: review of international literature and practical recommendations from an expert panel on the use of interferon

The degree to which interferon (IFN) alpha-2b offers real clinical benefits in the adjuvant therapy of melanoma at high risk of recurrence is a subject of debate. This, together with questions over optimal treatment scheme and concerns over toxicity, has limited its clinical use. On the basis of a review of the literature, an Italian Expert Panel has made practical recommendations for a consistent approach in the use of IFN. Although it is clear that more research into predictive factors to identify patients most likely to benefit from adjuvant IFN therapy is required, IFN remains the only currently available adjuvant option for melanoma. Based on meta-analyses of clinical trials, there is clear evidence that treatment with IFN is beneficial with regard to overall and recurrence-free survival (RFS). As such, IFN should be offered to patients who are at high risk of recurrence. Specific recommendations with regard to disease stage are provided.

Molecular pathways: response and resistance to BRAF and MEK inhibitors in BRAF(V600E) tumors

The RAS-RAF-MEK (MAP-ERK kinase)-ERK (extracellular signal-regulated kinase) pathway plays a central role in driving proliferation, survival, and metastasis signals in tumor cells, and the prevalence of oncogenic mutations in RAS and BRAF and upstream nodes makes this pathway the focus of significant oncology drug development efforts. This focus has been justified by the recent success of BRAF and MEK inhibitors in prolonging the lives of patients with BRAF(V600E/K)-mutant melanoma. Although it is disappointing that cures are relatively rare, this should not detract from the value of these agents to patients with cancer and the opportunity they provide in allowing us to gain a deeper understanding of drug response and resistance. These insights have already provided the basis for the evaluation of alternative dosing regimens and combination therapies in patients with melanoma.

[Cellular and molecular mechanisms of carcinogenic side effects and resistance to BRAF inhibitors in metastatic melanoma with BRAFV600 mutation: state of the knowledge]

Cutaneous melanoma is a malignant tumor with a high metastatic potential. If an early treatment is associated with a favorable outcome, the prognosis of metastatic melanoma remains poor. Advances in molecular characterization of cancers, notably the discovery of BRAF gene mutations in metastatic melanoma, allowed to the recent development of targeted therapies against mutated BRAF protein. Despite high tumor response rates observed in clinical trials, these new drugs are associated with frequent secondary tumor resistance occurrence and paradoxical carcinogenic side effects. The cellular and molecular mechanisms of these carcinogenic side effects and secondary resistance are not yet fully elucidated and are actually intensely studied. This review of the literature focus on the mechanisms of these carcinogenic side effects and on the tumor resistance associated with anti-BRAF targeted therapies.

Clinicopathological relevance of BRAF mutations in human cancer

BRAF represents one of the most frequently mutated protein kinase genes in human tumours. The mutation is commonly tested in pathology practice. BRAF mutation is seen in melanoma, papillary thyroid carcinoma (including papillary thyroid carcinoma arising from ovarian teratoma), ovarian serous tumours, colorectal carcinoma, gliomas, hepatobiliary carcinomas and hairy cell leukaemia. In these cancers, various genetic aberrations of the BRAF proto-oncogene, such as different point mutations and chromosomal rearrangements, have been reported. The most common mutation, BRAF V600E, can be detected by DNA sequencing and immunohistochemistry on formalin fixed, paraffin embedded tumour tissue. Detection of BRAF V600E mutation has the potential for clinical use as a diagnostic and prognostic marker. In addition, a great deal of research effort has been spent in strategies inhibiting its activity. Indeed, recent clinical trials involving BRAF selective inhibitors exhibited promising response rates in metastatic melanoma patients. Clinical trials are underway for other cancers. However, cutaneous side effects of treatment have been reported and therapeutic response to cancer is short-lived due to the emergence of several resistance mechanisms. In this review, we give an update on the clinical pathological relevance of BRAF mutation in cancer. It is hoped that the review will enhance the direction of future research and assist in more effective use of the knowledge of BRAF mutation in clinical practice.

Melanoma: from melanocyte to genetic alterations and clinical options

Metastatic melanoma remained for decades without any effective treatment and was thus considered as a paradigm of cancer resistance. Recent progress with understanding of the molecular mechanisms underlying melanoma initiation and progression revealed that melanomas are genetically and phenotypically heterogeneous tumors. This recent progress has allowed for the development of treatment able to improve for the first time the overall disease-free survival of metastatic melanoma patients. However, clinical responses are still either too transient or limited to restricted patient subsets. The complete cure of metastatic melanoma therefore remains a challenge in the clinic. This review aims to present the recent knowledge and discoveries of the molecular mechanisms involved in melanoma pathogenesis and their exploitation into clinic that have recently facilitated bench to bedside advances.

Dermatological adverse events from BRAF inhibitors: a growing problem

The development of targeted therapies has ushered in a new era in the management of melanoma. Inhibitors of the RAS-RAF-MEK-ERK pathway have taken the center stage with development at a rapid pace. Vemurafenib was recently approved by regulatory agencies, and other agents (e.g. dabrafenib) are in various stages of clinical testing. These agents are producing remarkable results for patients, but are also presenting new challenges. Clinical toxicities and drug resistance are topmost issues. Some of the most common and vivid representations of adverse events to these agents are the dermatologic manifestations. Published trials and initial observations reflect a toxicity profile (e.g. squamous cell carcinomas/keratoacanthomas, maculopapular rashes, hyperkeratosis) that is distinct from cutaneous toxicities from EGFR and mTOR inhibitors (acneiform rash, paronychia, xerosis). Their management extends beyond conservative treatment and includes specific physical and surgical treatment modalities, skill sets unique to dermatologists. All these pose significant challenges to clinicians, and sound knowledge of such toxicities and their management will likely result in improved patient outcomes and quality of life. In this manuscript, we provide an overview of the emerging scientific literature on dermatological adverse events arising out of BRAF inhibition.

BRAF inhibitors in cancer therapy

Activating BRAF mutations, leading to constitutive activation of the MAPK signaling pathway, are common in a variety of human cancers. Several small molecule BRAF inhibitors have been developed during the last years and shown promising results in clinical trials, especially for metastatic melanoma, while they have been less effective in colon cancer. Two inhibitors, vemurafenib and dabrafenib, have been approved for treatment of melanoma. Unfortunately, in most patients who initially respond the tumors eventually develop acquired resistance to the BRAF inhibitors. So far, a number of resistance mechanisms have been identified, including secondary NRAS mutations and BRAF alternative splicing, leading to reactivation of the MAPK pathway. Other alterations, both upstream and downstream of BRAF can have the same effect, and activation of alternative pathways can also play a role in resistance to BRAF inhibitors. In addition, intra-tumor heterogeneity with the presence of clones of tumor cells lacking BRAF mutations needs to be considered, since wildtype BRAF can be activated by inhibitors designed to target mutated BRAF. Combination of the BRAF inhibitor dabrafenib with the MEK inhibitor trametinib has significantly prolonged progression free survival compared to dabrafenib alone in metastatic melanoma. Combination treatments of BRAF inhibitors with other agents may not only circumvent or delay resistance, but may also lead to fewer side effects, such as development of secondary squamous tumors. Several clinical trials are underway for many different BRAF mutation positive cancers with BRAF inhibitors alone or in combination with other small molecule inhibitors, immunotherapies or conventional chemotherapy.

Isolated malignant melanoma metastasis to the pancreas

Summary:

Malignant melanomas rarely develop isolated pancreatic metastases. We describe a unique patient who is still alive 22 years following an isolated pancreatic melanoma metastasis, and we review the sparse literature in the field.

Severe pan-uveitis in a patient treated with vemurafenib for metastatic melanoma

BACKGROUND

Vemurafenib, an inhibitor of genetically activated BRAF, is now commonly prescribed for metastatic melanoma harboring a BRAF mutation. Reports on side effects have focused on cutaneous complications. We here present a case of a severe pan-uveitis associated with vemurafenib use.

CASE PRESENTATION

A 63-year old female was treated with the BRAF inhibitor vemurafenib for metastatic melanoma. After seven weeks of treatment, she developed near-complete visual loss in the course of a few days, as a result of severe uveitis. Vemurafenib had to be discontinued and systemic and topical corticosteroids were initiated. The visual symptoms improved slowly, however the cerebral metastases progressed and the patient died from her disease.

CONCLUSION

Treatment with vemurafenib has become an important component of standard clinical care for patients with metastatic melanoma. In addition, it is one of the best examples of genotype-directed therapy. This case illustrates that vemurafenib-induced uveitis can develop fast and be slow to resolve. Awareness of this potentially severe side effect is of major importance to oncologists and aggressive treatment should be considered.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

Cutaneous adverse events to type I BRAF inhibitors: an analysis of effects associated with each inhibitor and therapeutic time interval to onset

The treatment of malignant melanoma with inhibitors targeting the BRAF V600E mutation has demonstrated dramatic clinical and radiographic response with improved progression-free and overall survival in the majority of patients receiving treatment. However, cutaneous adverse effects-from proliferative processes to more classic drug side effects-are increasingly being reported in patients on BRAF inhibitors. In this comprehensive literature review we provide (1) an all-inclusive list of cutaneous adverse effects associated with selective class I RAF inhibitors, (2) specific adverse effects associated with each inhibitor, and (3) the therapeutic time interval associated with the onset of all reported lesion types. Twenty-two studies reporting cutaneous adverse reactions with selective class I RAF inhibitor therapy were retrieved from PubMed and sourced from relevant articles referenced by other papers. We identified over 45 differently described lesion types, corresponding to close to 2,000 cases. The most commonly reported lesion types in order of decreasing frequency include inflammatory dermatoses, benign lesions, malignant lesions, and hair/nail-related abnormalities. For the most part, the terminologies used in the original studies were retained. Case totals and time-to-lesion onset are presented for every group, and where available, for individual lesion types, by associated BRAF inhibitor.

Sensitization of melanoma cells for TRAIL-induced apoptosis by activation of mitochondrial pathways via Bax

The death ligand TRAIL (TNF-related apoptosis-inducing ligand) represents a promising therapeutic strategy for metastatic melanoma, however prevalent and inducible resistance limits its applicability and therapeutic use. Recent work has revealed that combinations with survival pathway inhibitors could efficiently sensitize melanoma cells for TRAIL. Here, a particular role was attributed to the activation of Bax, which is regulated by phosphorylation. Thus, TRAIL resistance in melanoma is explained by three major steps, namely high levels of antiapoptotic Bcl-2 proteins, high levels of inhibitor of apoptosis proteins (cIAPs) and suppressed Bax activity. Importantly, Bid was activated in response to TRAIL alone also in resistant cells to antagonize Bcl-2, and Bax was activated in response to pathway inhibitors. However, only in combinations, mitochondrial apoptosis pathways were opened to result in release of Smac/DIABLO, which functions as antagonist of cIAPs. Opening the caspase cascade by Smac then allowed efficient induction of apoptosis. Thus, direct or indirect targeting of Bax represents a suitable strategy to overcome TRAIL resistance in melanoma and may allow the establishment of TRAIL-based therapeutic approaches.

Acquired resistance and clonal evolution in melanoma during BRAF inhibitor therapy

BRAF inhibitors elicit rapid antitumor responses in the majority of patients with BRAF(V600)-mutant melanoma, but acquired drug resistance is almost universal. We sought to identify the core resistance pathways and the extent of tumor heterogeneity during disease progression. We show that mitogen-activated protein kinase reactivation mechanisms were detected among 70% of disease-progressive tissues, with RAS mutations, mutant BRAF amplification, and alternative splicing being most common. We also detected PI3K-PTEN-AKT-upregulating genetic alterations among 22% of progressive melanomas. Distinct molecular lesions in both core drug escape pathways were commonly detected concurrently in the same tumor or among multiple tumors from the same patient. Beyond harboring extensively heterogeneous resistance mechanisms, melanoma regrowth emerging from BRAF inhibitor selection displayed branched evolution marked by altered mutational spectra/signatures and increased fitness. Thus, melanoma genomic heterogeneity contributes significantly to BRAF inhibitor treatment failure, implying upfront, cotargeting of two core pathways as an essential strategy for durable responses.

Therapeutic target database update 2014: a resource for targeted therapeutics

Here we describe an update of the Therapeutic Target Database (http://bidd.nus.edu.sg/group/ttd/ttd.asp) for better serving the bench-to-clinic communities and for enabling more convenient data access, processing and exchange. Extensive efforts from the research, industry, clinical, regulatory and management communities have been collectively directed at the discovery, investigation, application, monitoring and management of targeted therapeutics. Increasing efforts have been directed at the development of stratified and personalized medicines. These efforts may be facilitated by the knowledge of the efficacy targets and biomarkers of targeted therapeutics. Therefore, we added search tools for using the International Classification of Disease ICD-10-CM and ICD-9-CM codes to retrieve the target, biomarker and drug information (currently enabling the search of almost 900 targets, 1800 biomarkers and 6000 drugs related to 900 disease conditions). We added information of almost 1800 biomarkers for 300 disease conditions and 200 drug scaffolds for 700 drugs. We significantly expanded Therapeutic Target Database data contents to cover >2300 targets (388 successful and 461 clinical trial targets), 20 600 drugs (2003 approved and 3147 clinical trial drugs), 20 000 multitarget agents against almost 400 target-pairs and the activity data of 1400 agents against 300 cell lines.

The genetic landscape of clinical resistance to RAF inhibition in metastatic melanoma

Most patients with BRAF(V600)-mutant metastatic melanoma develop resistance to selective RAF kinase inhibitors. The spectrum of clinical genetic resistance mechanisms to RAF inhibitors and options for salvage therapy are incompletely understood. We performed whole-exome sequencing on formalin-fixed, paraffin-embedded tumors from 45 patients with BRAF(V600)-mutant metastatic melanoma who received vemurafenib or dabrafenib monotherapy. Genetic alterations in known or putative RAF inhibitor resistance genes were observed in 23 of 45 patients (51%). Besides previously characterized alterations, we discovered a "long tail" of new mitogen-activated protein kinase (MAPK) pathway alterations (MAP2K2, MITF) that confer RAF inhibitor resistance. In three cases, multiple resistance gene alterations were observed within the same tumor biopsy. Overall, RAF inhibitor therapy leads to diverse clinical genetic resistance mechanisms, mostly involving MAPK pathway reactivation. Novel therapeutic combinations may be needed to achieve durable clinical control of BRAF(V600)-mutant melanoma. Integrating clinical genomics with preclinical screens may model subsequent resistance studies.

Towards defining biomarkers indicating resistances to targeted therapies

An impressive, but often short objective response was obtained in many tumor patients treated with different targeted therapies, but most of the patients develop resistances against these drugs. So far, a number of distinct mechanisms leading to intrinsic as well as acquired resistances have been identified in tumors of distinct origin. These can arise from genetic alterations, like mutations, truncations, and amplifications or due to deregulated expression of various proteins and signal transduction pathways, but also from cellular heterogeneity within tumors after an initial response. Therefore, biomarkers are urgently needed for cancer prognosis and personalized cancer medicine. The application of "ome"-based technologies including cancer (epi)genomics, next generation sequencing, cDNA microarrays and proteomics might led to the predictive or prognostic stratification of patients to categorize resistance mechanisms and to postulate combinations of treatment strategies. This review discusses the implementation of proteome-based analysis to identify markers of pathway (in)activation in tumors and the resistance mechanisms, which represent major clinical problems as a tool to optimize individually tailored therapies based on targeted drugs. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.

DNA sequencing of cancer: what have we learned?

DNA sequencing has taught us much about the structure of cancer genomes and enabled the discovery of novel genes that drive and maintain tumorigenesis. With the advent and application of next-generation massively parallel sequencing technologies, one can rapidly generate and analyze data from the cellular "-omes": genomes, exomes, and transcriptomes. This review highlights recent genomic discoveries in signal transduction, metabolism, epigenetic modifications, cell cycle and genome maintenance, RNA processing, and transcription. Additionally, genomic sequencing has revealed the complexity of the cancer genome and has enabled the discovery of functional rearrangements with therapeutic and diagnostic potentials.

Dabrafenib therapy for advanced melanoma

OBJECTIVE

To summarize the clinical development of dabrafenib and to highlight the clinically relevant distinct characteristics of dabrafenib in contrast to vemurafenib.

DATA SOURCE

An English-language literature search of MEDLINE/PubMed (1966-June 2013), using the keywords GSK2118436, dabrafenib, vemurafenib, selective BRAF inhibitor, and advanced melanoma, was conducted. Data were also obtained from package inserts, meeting abstracts, and clinical registries.

STUDY SELECTION AND DATA EXTRACTION

All relevant published articles on dabrafenib and vemurafenib were reviewed. Clinical trial registries and meeting abstracts were used for information about ongoing studies.

DATA SYNTHESIS

BRAF(V600E) mutation confers constitutive BRAK kinase activation in melanoma cells, promoting tumor growth. This discovery led to the development of BRAF kinase inhibitors like vemurafenib and dabrafenib. Dabrafenib has been approved to treat patients with BRAF(V600E)-positive unresectable or metastatic melanoma based on its clinical benefit demonstrated in a randomized phase III study. It has also been shown to be safe and effective in patients with BRAF mutant advanced melanoma involving the brain. Dabrafenib is well tolerated, with the most common adverse effects being hyperkeratosis, headache, pyrexia, and arthralgia. Currently, there is no evidence to suggest that one BRAF inhibitor is superior to the other. With similar efficacy, therapy selection will likely be influenced by differential tolerability and cost.

CONCLUSIONS

Dabrafenib joins vemurafenib to confirm the superior clinical outcome of the BRAF inhibitors when compared with dacarbazine in patients with BRAF(V600E)-positive advanced melanoma. Active research is ongoing to expand its utility into the adjuvant setting and to circumvent rapid emergence of drug resistance.

Challenging resistance mechanisms to therapies for metastatic melanoma

Melanoma is the most aggressive form of skin cancer and, if spread outside the epidermis, has a dismal prognosis. Before the approval of the anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) monoclonal antibody ipilimumab and the BRAF inhibitors vemurafenib and dabrafenib, no other agents had demonstrated better results in terms of overall survival than the DNA-methylating compound dacarbazine (or its oral analog temozolomide). However, most patients with metastatic melanoma do not obtain long-lasting clinical benefit from ipilimumab and responses to BRAF inhibitors are short lived. Thus, combination therapies with inhibitors of DNA repair (e.g., poly(ADP-ribose) polymerase [PARP] inhibitors), novel immunomodulators (monoclonal antibodies against programmed death-1 [PD-1] or its ligand PD-L1), targeted therapies (mitogen-activated protein kinase [MAPK]/extracellular signal-regulated kinase [ERK] kinase [MEK] or phosphatidylinositol 3-kinase [PI3K]/AKT/mammalian target of rapamycin [mTOR] inhibitors) or antiangiogenic agents are currently being investigated to improve the efficacy of antimelanoma therapies. This review discusses the implications of simultaneously targeting key regulators of melanoma cell proliferation/survival and immune responses to counteract resistance.

AEBP1 upregulation confers acquired resistance to BRAF (V600E) inhibition in melanoma

An activating BRAF (V600E) kinase mutation occurs in approximately half of melanomas. Recent clinical studies have demonstrated that vemurafenib (PLX4032) and dabrafenib, potent and selective inhibitors of mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF), exhibit remarkable activities in patients with V600 BRAF mutant melanomas. However, acquired drug resistance invariably develops after the initial treatment. Identification of acquired resistance mechanisms may inform the development of new therapies that elicit long-term responses of melanomas to BRAF inhibitors. Here we report that increased expression of AEBP1 (adipocyte enhancer-binding protein 1) confers acquired resistance to BRAF inhibition in melanoma. AEBP1 is shown to be highly upregulated in PLX4032-resistant melanoma cells because of the hyperactivation of the PI3K/Akt-cAMP response element-binding protein (CREB) signaling pathway. This upregulates AEBP1 expression and thus leads to the activation of NF-κB via accelerating IκBa degradation. In addition, inhibition of the PI3K/Akt-CREB-AEBP1-NF-κB pathway greatly reverses the PLX4032-resistant phenotype of melanoma cells. Furthermore, increased expression of AEBP1 is validated in post-treatment tumors in patients with acquired resistance to BRAF inhibitor. Therefore, these results reveal a novel PI3K/Akt-CREB-AEBP1-NF-κB pathway whose activation contributes to acquired resistance to BRAF inhibition, and suggest that this pathway, particularly AEBP1, may represent a novel therapeutic target for treating BRAF inhibitor-resistant melanoma.

Mutation landscape in melanoma patients clinical implications of heterogeneity of BRAF mutations

BACKGROUND

The detection of V600E BRAF mutations has fundamental clinical consequences as the treatment option with BRAF inhibitors such as vemurafenib or dabrafenib yields response rates of ~48%. Heterogeneity with respect to BRAF mutation in different metastases has been described in single cases. As this has important implications for the determination of BRAF status and treatment of patients, it is essential to acquire more data.

METHODS

A total of 300 tumour samples from 187 melanoma patients were analysed for BRAF mutations by pyrosequencing. Equivocal results were confirmed by capillary sequencing. Clinical data with respect to melanoma type, tumour site and survival were summarised for 53 patients with multiple analysed tumour samples (2-13 per patient).

RESULTS

BRAF mutations were found in 84 patients (44.9%) and 144 tumour samples (48%) with BRAF mutations in 45.5% of primary tumours and 51.3% of metastases, respectively. In 10 out of 53 patients (18.9%) where multiple samples were analysed results were discordant with respect to mutation findings with wild-type and mutated tumours in the same patient. Mutations did not appear more frequently over the course of disease nor was its occurrence associated with a specific localisation of metastases.

CONCLUSION

As heterogeneity with respect to BRAF mutation status is detected in melanoma patients, subsequent testing of initially wild-type patients can yield different results and thus make BRAF inhibitor therapy accessible. The role of heterogeneity in testing and for clinical response to therapy with a BRAF inhibitor needs to be further investigated.

Patterns of response and progression in patients with BRAF-mutant melanoma metastatic to the brain who were treated with dabrafenib

BACKGROUND

Dabrafenib has activity in patients with brain metastases, but little is known of the relative efficacy of treatment within and outside the brain. This study sought to examine the intracranial (IC) and extracranial (EC) patterns of response and progression in patients with active melanoma brain metastases treated with dabrafenib.

METHODS

Clinicopathologic parameters were collected on patients with active brain metastases enrolled in the phase 1 and 2 studies of dabrafenib at a single institution. RECIST (Response Evaluation Criteria In Solid Tumors) response and progression-free survival (PFS) were prospectively assessed by disease site (IC versus EC). Treatments received after disease progression were also assessed.

RESULTS

A total of 23 patients were studied. Response rates were similar in IC (78%) and EC (90%) sites (P = .416). IC and EC response was concordant in 71% of patients. Median site-specific PFS was identical in both IC and EC sites (23.6 weeks, P = .465), and exceeded whole-body PFS determined by RECIST (16.3 weeks). Of 20 patients with progressive disease (PD), 6 had IC PD only, 6 had EC PD only, and 8 had PD in both sites. In those with isolated intracranial PD, 5 of 6 underwent local therapy to the brain and continued on dabrafenib longer than 30 days.

CONCLUSIONS

IC and EC melanoma metastases respond similarly to dabrafenib. There is no dominant site or pattern of disease progression in patients with brain metastases treated with dabrafenib. Salvage local therapy is possible in most patients after IC disease progression, with ongoing dabrafenib treatment possible in a subset of patients.

BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling

Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. DOI: http://dx.doi.org/10.7554/eLife.00969.001.

Melanomas of unknown primary have a mutation profile consistent with cutaneous sun-exposed melanoma

Melanoma of unknown primary (MUP) is an uncommon phenomenon whereby patients present with metastatic disease without an evident primary site. To determine their likely site of origin, we combined exome sequencing from 33 MUPs to assess the total rate of somatic mutations and degree of UV mutagenesis. An independent cohort of 91 archival MUPs was also screened for 46 hot spot mutations highly prevalent in melanoma including BRAF, NRAS, KIT, GNAQ, and GNA11. Results showed that the majority of MUPs exhibited high somatic mutation rates, high ratios of C>T/G>A transitions, and a high rate of BRAF (45 of 101, 45%) and NRAS (32 of 101, 32%) mutations, collectively indicating a mutation profile consistent with cutaneous sun-exposed melanomas. These data suggest that a significant proportion of MUPs arise from regressed or unrecognized primary cutaneous melanomas or arise de novo in lymph nodes from nevus cells that have migrated from the skin.

Skin toxicity of targeted cancer agents: mechanisms and intervention

In recent years, targeted agents have rapidly evolved as effective tools in the clinical management of a broad range of malignant diseases. These agents disrupt molecular mechanisms and signaling modules that drive the malignant phenotype in defined subsets of malignancies. Beyond the intended cellular targets crucial to tumor growth and progression, these agents also affect signal transduction in normal cells and tissues. The resulting adverse events and their clinical management continue to change, as newer agents with an ever-increasing target spectrum are developed. We provide a succinct overview of dermatologic toxicities arising from the targeting of receptor tyrosine kinases and downstream effectors. Emergent insights into the pathomechanisms involved and the use of this knowledge base to alleviate cutaneous adverse events are discussed.