BRAF V600 Metastatic Melanoma Research Articles

BRAFV600E Metastatic Melanoma Journey: A Perspective from a Patient and his Oncologist.

This article is co-authored by a patient with BRAFV600E metastatic melanoma and his treating oncologist. The patient describes how he coped with his diagnosis and treatment. He details the pathway of his melanoma treatment, which has spanned over 10 years, including surgical interventions, medical treatment, and participation in clinical trials. He relates his experience of living with the disease-and the adverse effects of treatment-in the long term. The clinical perspective of his treating oncologist reviews the diagnostic process and explains how the therapeutic options were selected for and with the patient. The oncologist also addresses the integration of the patient into clinical trials involving programmed death-1 (PD-1) inhibitors and BRAF/MEK inhibitors. Challenges related to the adverse effects that occurred and the personalised treatment of the patient are also discussed. Finally, the article evaluates current advances in treatment and future therapeutic approaches. This case highlights the challenges of identifying which therapeutic options are most appropriate for individual patients with BRAFV600E metastatic melanoma.

RICTOR/mTORC2 downregulation in BRAFV600E melanoma cells promotes resistance to BRAF/MEK inhibition.

The main drawback of BRAF/MEK inhibitors (BRAF/MEKi)-based targeted therapy in the management of BRAF-mutated cutaneous metastatic melanoma (MM) is the development of therapeutic resistance. We aimed to assess in this context the role of mTORC2, a signaling complex defined by the presence of the essential RICTOR subunit, regarded as an oncogenic driver in several tumor types, including MM. After analyzing The Cancer Genome Atlas MM patients' database to explore both overall survival and molecular signatures as a function of intra-tumor RICTOR levels, we investigated the effects of RICTOR downregulation in BRAFV600E MM cell lines on their response to BRAF/MEKi. We performed proteomic screening to identify proteins modulated by changes in RICTOR expression, and Seahorse analysis to evaluate the effects of RICTOR depletion on mitochondrial respiration. The combination of BRAFi with drugs targeting proteins and processes emerged in the proteomic screening was carried out on RICTOR-deficient cells in vitro and in a xenograft setting in vivo. Low RICTOR levels in BRAF-mutated MM correlate with a worse clinical outcome. Gene Set Enrichment Analysis of low-RICTOR tumors display gene signatures suggestive of activation of the mitochondrial Electron Transport Chain (ETC) energy production. RICTOR-deficient BRAFV600E cells are intrinsically tolerant to BRAF/MEKi and anticipate the onset of resistance to BRAFi upon prolonged drug exposure. Moreover, in drug-naïve cells we observed a decline in RICTOR expression shortly after BRAFi exposure. In RICTOR-depleted cells, both mitochondrial respiration and expression of nicotinamide phosphoribosyltransferase (NAMPT) are enhanced, and their pharmacological inhibition restores sensitivity to BRAFi. Our work unveils an unforeseen tumor-suppressing role for mTORC2 in the early adaptation phase of BRAFV600E melanoma cells to targeted therapy and identifies the NAMPT-ETC axis as a potential therapeutic vulnerability of low RICTOR tumors. Importantly, our findings indicate that the evaluation of intra-tumor RICTOR levels has a prognostic value in metastatic melanoma and may help to guide therapeutic strategies in a personalized manner.

M-CSF as a therapeutic target in BRAFV600E melanoma resistant to BRAF inhibitors.

Disseminated BRAFV600E melanoma responds to BRAF inhibitors (BRAFi) but easily develops resistance with poor prognosis. Secretome plays a pivotal role during tumour progression causing profound effects on therapeutic efficacy. Secreted M-CSF is involved in both cytotoxicity suppression and tumour progression in melanoma. We aimed to analyse the M-CSF contribution in resistant metastatic melanoma to BRAF-targeted therapies. Conditioned media from melanoma cells were analysed by citoarray. Viability and migration/invasion assays were performed with paired melanoma cells and tumour growth in xenografted SCID mice. We evaluated the impact of M-CSF plasma levels with clinical prognosis from 35 metastatic BRAFV600E-mutant melanoma patients. BRAFi-resistant melanoma cells secretome is rich in pro-tumour cytokines. M-CSF secretion is essential to induce a Vemurafenib-resistant phenotype in melanoma cells. Further, we demonstrated that M-CSF mAb in combination with Vemurafenib and autophagy blockers synergistically induce apoptosis, impair migration and reduce tumour growth in BRAFi-resistant melanoma cells. Interestingly, lower M-CSF plasma levels are associated with better prognosis in metastatic melanoma patients. Secreted M-CSF induces a BRAFi-resistant phenotype and means worse prognosis in BRAFV600E metastatic melanoma patients. These results identify secreted M-CSF as a promising therapeutic target toward BRAFi-resistant melanomas.

LBA40 SECOMBIT: The best sequential approach with combo immunotherapy [ipilimumab (I) /nivolumab (N)] and combo target therapy [encorafenib (E)/binimetinib (B)] in patients with BRAF mutated metastatic melanoma: A phase II randomized study

Treatment with targeted therapy (BRAF and MEK inhibitors) and immune-checkpoint inhibitors (anti-CTLA4, anti-PD-1) have improved the outcome of BRAF-V600 metastatic melanoma patients in first line. Targeted therapy demonstrated higher response rates, which may be limited over time; while the combination I+N is associated with lower but durable response rate. The best sequencing remains an open question. In addition, a short course of targeted therapy switched to I+N at best response is supported by models and may be clinically advantageous.

Abstract 1473: Nonclinical development of PF-07284890 (ARRY-461), a potent, brain-penetrant, small molecule inhibitor of BRAF V600-mutation-driven tumors in vitro and in vivo

Abstract Although approved BRAF inhibitors have transformed the treatment of patients with certain BRAF V600 mutant cancers, their long-term efficacy is thought to be limited by poor brain penetration. As a result, disease progression in the brain is a significant cause of morbidity and mortality. PF-07284890 (ARRY-461) is an orally bioavailable, brain penetrant, potent, small molecule inhibitor targeting BRAF V600 mutant tumors and is in clinical development in patients with BRAF V600 metastatic melanoma with progression to the brain. In biochemical in vitro studies, PF-07284890 inhibits BRAF and CRAF with IC50's of 5.8 and 4.1 nM, respectively. Additionally, PF-07284890 inhibits the clinically relevant kinase domain BRAF V600 mutants (V600E and V600K) (IC50 = 24-25 nM). In cell-based systems, PF-07284890 potently inhibits phosphorylation of ERK, a downstream marker of BRAF inhibition, and potently inhibits proliferation of BRAF V600E/K mutant melanoma cell lines (IC50 18-38 nM). PF-07284890 was designed to distribute to the brain and, as such, in vitro experiments indicate that PF-07284890 has high cellular membrane permeability and is not a substrate for human P glycoprotein (P-gp). After oral administration of PF-07284890 to mice and rats, PF-07284890 distributes to the brain where the free fraction adjusted exposure in the brain was approximately proportional to the free fraction adjusted exposure in plasma (i.e., Cbrain,u/Cplasma,u approaches 1.0). In vivo, PF-07284890 inhibits phosphorylation of ERK in A375 BRAF V600E tumors, achieving maximal target inhibitions at a dose of 10 mg/kg. PF-07284890 has been evaluated for its ability to control BRAF V600E cell line and patient-derived melanoma xenograft tumor growth in nude mice when implanted both subcutaneously and intracranially. Dose-related tumor growth inhibition was demonstrated at dose levels ranging from 1 to 30 mg/kg, BID in both subcutaneous and intracranial xenograft models. In all models, regardless of tumor location, maximal efficacy was observed in dose ranges of 10-30 mg/kg BID. In the intracranial A375-luc BRAF V600E melanoma xenograft model, significant and durable tumor regressions were seen at doses of 10 and 30 mg/kg/day which translated to a profound survival benefit in animals receiving PF-07284890 (median survival > 55 days post-implantation) compared to control animals (median survival = 15 days). GLP safety studies demonstrated a good safety profile for PF-07284890. PF-07284890 is fully brain penetrant, with the potential to address this key unmet medical need and thereby defines a new class of brain penetrant, potent and selective BRAF inhibitors. Citation Format: Karyn Bouhana, Deborah Anderson, Walter DeWolf, Suzy Brown, Lance Williams, Li Ren, David Moreno, Ross Wallace, Jay Brad Fell, Dylan Hartley, Patrice Lee. Nonclinical development of PF-07284890 (ARRY-461), a potent, brain-penetrant, small molecule inhibitor of BRAF V600-mutation-driven tumors in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1473.

Active notch protects MAPK activated melanoma cell lines from MEK inhibitor cobimetinib

The crosstalk between Notch and MAPK pathway plays a role in MEK inhibitor resistance in BRAFV600E metastatic melanoma (MM) and promotes migration in GNAQQ209L uveal melanoma (UM) cells. We determined the cytotoxicity of combinatorial inhibition of MEK and Notch by cobimetinib and γ-secretase inhibitor (GSI) nirogacestat, in BRAFV600E and BRAF wt MM and GNAQQ209L UM cells displaying different Erk1/2 and Notch activation status, with the aim to elucidate the impact of Notch signaling in the response to MEK inhibitor. Overall the combination was synergic in BRAFV600E MM and GNAQQ209L UM cells and antagonistic in BRAF wt one. Focusing on UM cells, we found that cobimetinib resulted in G0/G1 phase arrest and apoptosis induction, whereas the combination with GSI increased treatment efficacy by inducing a senescent-like state of cells and by blocking migration towards liver cancer cells. Mechanistically, this was reflected in a strong reduction of cyclin D1, in the inactivation of retinoblastoma protein and in the increase of p27KIP1 expression levels. Of note, each drug alone prevented Notch signaling activation resulting in inhibition of c-jun(Ser63) and Hes-1 expression. The combination achieved the strongest inhibition on Notch signaling and on both c-jun(Ser63) and Erk1/2 activation level. In conclusion we unveiled a coordinate action of MAPK and Notch signaling in promoting proliferation of BRAFV600E MM and GNAQQ209L UM cells. Remarkably, the simultaneous inhibition of MEK and Notch signaling highlighted a role for the second pathway in protecting cells against senescence in GNAQQ209L UM cells treated with the MEK inhibitor.

Establishing the six-month resource utilization and cost-of-care for the treatment of first-line metastatic BRAF (V600) melanoma with combination BRAF and MEK inhibitors.

e19396 Background: Comparative data on cancer therapy health care resource utilization (HCRU) and associated cost will be helpful as value-based healthcare moves forward. BRAF & MEK inhibitor combinations are considered first-line treatment for BRAF (V-600) metastatic melanoma (MM), although head-to-head trials are lacking. We aimed to establish the real-world HCRU and 6-month (mo) cost-of-care in V-600 MM treated with BRAF & MEK inhibitor therapy. Methods: A single data team in 2018 performed a multicenter, retrospective chart audit of adult patients with BRAF V-600 MM. Four institutions from across the US with patients who had received either dabrafenib + Trametinib (DT) or vemurafenib + cobimetinib (VC) were enrolled. In the most recent 12 mo period, data was captured from the start of therapy for 6 mo or until therapy was stopped. Dose change or stoppage was accessed for cause (toxicity, disease, death, other). Variables included hospitalization, emergency room (ER), all clinic visits (routine + extra), scans, labs, and treatment drug (AWP). Medicare reimbursed rates were applied for cost estimates. Utilization and costs were measured on per patient per month (PPPM) bases and the total cost over 6 mo for each combination. Results: Of the 42 patients included, 34 and 8 were initiated on DT and VC, respectively. Proportions of patients with extra clinic visits and hospital admissions were 79%, 15% and 75%, 13%, respectively for DT and VC. PPPM hospitalization was the lowest among the resources utilized 0.24 for DT and 0.17 for VC. A higher proportion of VC patients (75%) had a dose reduction due to drug toxicity compared with 29% of patients treated with DT (P < 0.05). Discontinuation rates were the same between both combinations (0.26). 32 patients had completed 6 mo of treatment (26 DT and 6 VC). For those DT, the mean total costs including drug and the mean monthly total costs were $157,253 and $26,209 compared to $107,240 and $17,873 for VC, respectively. The mean total costs for hospitalization were $10,562 for DT and $7,456 for VC. The mean total costs for the drug were $145,012 for DT and $97,924 for VC. Conclusions: The 6-month total cost-of-care for the treatment of first-line V-600 MM with DT was $157,253 and $107,240 for VC, mostly attributable to drug cost. In a value-based healthcare system, total 6-month cost-of-care may help distinguish between equally effective regimens.

Abstract 4260: 3D colorectal cancer organoids as preclinical models for assessment of activity of RAF inhibitor BGB-283

Abstract Tumor organoids are three-dimensional (3D) cultures of cancer cells. They can be derived from the tumor cell lines, patient-derived xenografts and tumor tissues from cancer patients, thereby providing an attractive in vitro assay to optimize anticancer treatment. Oncogenic B-RAF, which drives cell transformation and proliferation, has been detected in 5-15% of colorectal cancers (CRC). Despite the remarkable clinical activities achieved by vemurafenib in treating B-RAF V600E metastatic melanoma, their clinical efficacy in B-RAF V600E CRC is far less impressive. BGB-283, currently under clinical development for RAF and RAS mutated solid tumors, is a novel inhibitor of the RAF dimer with inhibitory activities against RAF family kinases. In this study, we evaluated the anti-proliferative effect of BGB-283 and compared it to BRAF inhibitor vemurafenib in CRC patient tumor derived organoids models. BGB-283 exhibited therapeutic potentials in tumors with mutations in the MAPK pathway. Herein, we reported the establishment of tumor organoid models from 19 CRC patients’ tumor tissues with a success rate of 83%. Organoids maintained many characteristics of their original tumors based on their histology. Our studies using primary CRC tumor organoids showed that in contrast to vemurafenib, which only inhibited B-RAF V600E CRC tumors, BGB-283 had inhibition effect on both B-RAF V600E and KRAS mutated tumors. These findings support BGB-283 as a promising clinical stage antitumor agent in treating CRC harboring B-RAF V600E and KRAS mutations. In addition, we showed that patient-derived organoids can be a valuable tool to test drug sensitivity in a personalized treatment and help to fill the gap between tumor genetics and patient trials. Citation Format: Xiaoran Wu, Chunyan Fu, Xi Yuan, Lianhai Zhang, Xiaohong Wang, Jiafu Ji, Lusong Luo. 3D colorectal cancer organoids as preclinical models for assessment of activity of RAF inhibitor BGB-283. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4260.

BGB-283, a Novel RAF Kinase and EGFR Inhibitor, Displays Potent Antitumor Activity in BRAF-Mutated Colorectal Cancers.

Oncogenic BRAF, which drives cell transformation and proliferation, has been detected in approximately 50% of human malignant melanomas and 5% to 15% of colorectal cancers. Despite the remarkable clinical activities achieved by vemurafenib and dabrafenib in treating BRAF(V600E) metastatic melanoma, their clinical efficacy in BRAF(V600E) colorectal cancer is far less impressive. Prior studies suggested that feedback activation of EGFR and MAPK signaling upon BRAF inhibition might contribute to the relative unresponsiveness of colorectal cancer to the first-generation BRAF inhibitors. Here, we report characterization of a dual RAF kinase/EGFR inhibitor, BGB-283, which is currently under clinical investigation. In vitro, BGB-283 potently inhibits BRAF(V600E)-activated ERK phosphorylation and cell proliferation. It demonstrates selective cytotoxicity and preferentially inhibits proliferation of cancer cells harboring BRAF(V600E) and EGFR mutation/amplification. In BRAF(V600E) colorectal cancer cell lines, BGB-283 effectively inhibits the reactivation of EGFR and EGFR-mediated cell proliferation. In vivo, BGB-283 treatment leads to dose-dependent tumor growth inhibition accompanied by partial and complete tumor regressions in both cell line-derived and primary human colorectal tumor xenografts bearing BRAF(V600E) mutation. These findings support BGB-283 as a potent antitumor drug candidate with clinical potential for treating colorectal cancer harboring BRAF(V600E) mutation.

Abstract 4692: BGB-283, a novel RAF kinase and EGFR dual inhibitor, displays potent antitumor activity in B-RAF mutated colorectal cancers

Abstract Oncogenic B-RAF, which drives cell transformation and proliferation, has been detected in approximately 70% of human malignant melanomas and 5-15% of colorectal cancers (CRC). B-RAFV600E mutation, which gives rise to constitutive MAPK signaling, accounts for at least 90% of oncogenic B-RAF mutations. Despite the remarkable clinical activities achieved by vemurafenib and dabrafenib in treating B-RAFV600E metastatic melanoma, their clinical efficacy in B-RAFV600E CRC is far less impressive. Prior studies suggested that feedback activation of EGFR and MAPK signaling upon B-RAF inhibition contributed to the intrinsic resistance of CRC to the first generation B-RAF inhibitors. This report represents the first characterization of a dual RAF kinase/EGFR inhibitor, BGB-283, which is currently under clinical investigations. BGB-283 is a potent and selective pan-RAF and EGFR inhibitor with IC50 ranging from 5 to 47 nM on RAF and EGFR kinases. In vitro, BGB-283 potently inhibits B-RAFV600E-activated ERK phosphorylation and cell proliferation. It demonstrates selective cytotoxicity and preferentially inhibits proliferation of cancer cells harbouring B-RAFV600E and EGFR mutation/amplification. In B-RAFV600E CRC cell lines, BGB-283 effectively inhibits the reactivation of EGFR and achieved sustained inhibition of MAPK pathway. In vivo, BGB-283 is highly efficacious in inhibiting tumor growth accompanied by partial and complete tumor regressions in both BRAFV600E mutant cell derived CRC xenograft models, including HT29, Colo205, WiDr, as well as two primary human CRC xenograft models. In particular, BGB-283 shows compelling efficacy and potent inhibition of EGFR/MAPK signaling in WiDr xenograft model where EGFR reactivation occurs upon B-RAF inhibition. These findings support BGB-283 as a potent antitumor drug candidate with clinical potential for treating CRC harboring B-RAFV600E mutation. Citation Format: Zhiyu Tang, Xi Yuan, Rong Du, Shing-Hu Cheung, Guoliang Zhang, Jing Wei, Yuan Zhao, Yingcai Feng, Yi Zhang, Yunguang Du, Xiaoxia Hu, Wenfeng Gong, Yong Liu, Yajuan Gao, Rui Hao, Jiafu Ji, Lianhai Zhang, Shuangxi Li, David Sutton, Min Wei, Changyou Zhou, Lai Wang, Lusong Luo. BGB-283, a novel RAF kinase and EGFR dual inhibitor, displays potent antitumor activity in B-RAF mutated colorectal cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4692. doi:10.1158/1538-7445.AM2015-4692

PCN39 - Modeling Annual Projected Revenue Impact of Therapy Introduction For Patients With Braf V600 Metastatic Melanoma From A Hospital Perspective

PCN39 - Modeling Annual Projected Revenue Impact of Therapy Introduction For Patients With Braf V600 Metastatic Melanoma From A Hospital Perspective

Health-related quality of life impact in a randomised phase III study of the combination of dabrafenib and trametinib versus dabrafenib monotherapy in patients with BRAF V600 metastatic melanoma

AimTo present the impact of treatments on health-related quality of life (HRQoL) from the double-blind, randomised phase III COMBI-d study that investigated the combination of dabrafenib and trametinib versus dabrafenib monotherapy in patients with BRAF V600E/K-mutant metastatic melanoma. COMBI-d showed significantly prolonged progression-free survival for the combination. MethodsHRQoL was evaluated using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-C30, a generic cancer questionnaire (completed at baseline, during study treatment, at progression and post progression) assessing various dimensions (global health/QoL, functional status, and symptom impact). A mixed-model, repeated-measures analyses of covariance evaluated differences between arms. ResultsQuestionnaire completion rates were >95% at baseline, >85% to week 40 and >70% at disease progression. Baseline scores across both arms were comparable for all dimensions. Global health dimension scores were significantly better at weeks 8, 16 and 24 for patients receiving the combination during treatment and at progression. The majority of functional dimension scores (physical, social, role, emotional and cognitive functioning) trended in favour of the combination. Pain scores were significantly improved and clinically meaningful (6–13 point difference) for patients receiving the combination for all follow-up assessments versus those receiving dabrafenib monotherapy. For other symptom dimensions (nausea and vomiting, diarrhoea, dyspnoea, and constipation), scores trended in favour of dabrafenib monotherapy. ConclusionThis analysis demonstrates that the combination of dabrafenib and trametinib provides better preservation of HRQoL and pain improvements versus dabrafenib monotherapy while also delaying progression. (Clinicaltrials.gov registration number: NCT01584648).

Predictors of Treatment (Tx) Response and Progression in Braf V600E Metastatic Melanoma (Mm) Patients (Pts) with Brain Metastases (Bm) Receiving Vemurafenib (Vem) in a Real-World Setting

ABSTRACT Aim: mM pts with BM are associated with poor prognosis. Selective BRAF inhibitors may have a significant role in the tx of BM but data are limited. This study investigates predictors of intracranial tx response and intracranial progression among BRAFV600E mM pts with BM receiving vem in a real-word setting. Methods: Demographic and clinical characteristics, disease progression status, and tx response data were collected from a chart review by a panel of US oncologists on 283 BRAFV600E mM pts with active BM receiving vem. Predictors of intracranial tx response (complete response [CR] or partial response [PR]) and intracranial disease progression while on vem were identified using logistic regression models. Results: At vem initiation, mean age was 57 years, 61% of pts were male, and 68% had ECOG 0-1. Median follow-up time after vem initiation was 5.7 months. 53% of pts discontinued vem tx and 7% of pts had a vem dose reduction. While on vem, 48% of pts achieved intracranial CR/PR and 46% of pts achieved extracranial CR/PR. Intracranial disease progression occurred in 28% of pts while on vem. Predictors of intracranial CR/PR were corticosteroid use while on vem and the use of vem as 1st line tx after BM diagnosis (Table). Pts with larger number and size of BM before vem were less likely to achieve intracranial CR/PR. Predictors of disease progression were progressive extracranial disease before vem, larger number and size of BM before vem, and extent of extracranial metastasic disease before vem. The use of local tx before vem was associated with a reduced risk of intracranial progression. Conclusions: In real-world practice, 48% pts achieved intracranial CR/PR when treated with vem. Predictors of tx response were lower size and number of BM, earlier use of vem, and corticosteroid use. Predictors of intracranial progression were larger size and number of BM, progressive extracranial disease before vem, extent of extracranial metastasic disease, and no local tx before vem. Prospective data on tx outcomes are warranted in this population with high unmet need. Odds ratio (95% CI) Predictors of Intracranial CR or PR Concomitant use of corticosteroids (ref: no use of corticosteroids) 3.7 (1.9; 7.0) Number of BM (ref: ≤ 3 BM) ≥ 4 BM 0.3 (0.1; 0.6) Diameter of the largest BM (ref: 5-10mm 0.2 (0.1; 0.7) ≥ 10mm 0.8 (0.3; 1.9) Vem as 1st line after BM diagnosis (ref: vem initiated later lines) 4.4 (1.4; 13.3) Predictors of Intracranial Progression Progressive extracranial metastatic disease before vem initiation (ref: stable/regressive) 4.8 (2.3; 10.1) Local treatment for BM (ref: no local treatments) 0.4 (0.2; 0.9) Number of BM (ref: ≤ 1 BM) 2-4 BM 1.5 (0.6; 3.6) ≥ 5 BM 8.2 (2.3; 28.8) Number of sites of extracranial metastases (ref: ≤ 1 site) 2 sites 3.7 (1.6; 8.8) ≥ 3 sites 1.9 (0.8; 4.8) Diameter of the largest BM (ref: 5-10mm 7.8 (2.1; 29.1) ≥ 10mm 3.3 (0.9; 11.7) Disclosure: G. Gibney: Geoffrey Thomas Gibney is an employee of the Moffitt Cancer Center and a consultant for Roche/Genentch; G. Gauthier: Genevieve Gauthier is an employee of Analysis Group, Inc., which has received consultancy fees from Genentech Inc. No other disclosures apply; C. Ayas: Charles Ayas is an employee of Analysis Group, Inc., which has received consultancy fees from Genentech Inc. No other disclosures apply; P. Galebach: Phil Galebach is an employee of Analysis Group, Inc., which has received consultancy fees from Genentech Inc. No other disclosures apply; E. Wu: Eric Wu is an employee of Analysis Group, Inc., which has received consultancy fees from Genentech Inc. No other disclosures apply; Y.M. Yim: Yeun Mi Yim is an employee of Genentech Inc. and hold stock ownership of Roche; S.S. Abhyankar: Sarang S. Abhyankar is an employee of Genentech Inc. and hold stock ownership of Roche; C. Reyes: Carolina M. Reyes is an employee of Genentech Inc. and hold stock ownership of Roche; A. Guerin: Annie Guerin is an employee of Analysis Group, Inc., which has received consultancy fees from Genentech Inc. No other disclosures apply.

Dabrafenib and Trametinib, Alone and in Combination for BRAF-Mutant Metastatic Melanoma

Dabrafenib and trametinib were approved for use as monotherapies in BRAF-mutant metastatic melanoma by the U.S. Food and Drug Administration (FDA) in 2013, and most recently, their use in combination has received accelerated FDA approval. Both drugs target the mitogen-activated protein kinase (MAPK) pathway: dabrafenib selectively inhibits mutant BRAF that constitutively activates the pathway, and trametinib selectively inhibits MEK1 and MEK2 proteins activated by RAF kinases. The phase III study of dabrafenib in BRAF(V600E) metastatic melanoma reported rapid tumor regression in most patients and a 59% objective RECIST response rate. The median progression-free survival (PFS) and overall survival (OS) were improved compared with dacarbazine. Toxicities were well tolerated and different from those reported for vemurafenib, the first FDA-approved BRAF inhibitor. Efficacy has been demonstrated in other BRAF-mutant genotypes. The phase III study of trametinib in BRAF inhibitor-naïve patients with BRAF(V600E) or BRAF(V600K) also showed benefit with a prolonged median PFS and OS compared with chemotherapy. Trametinib is ineffective in patients who have progressed on BRAF inhibitors. A phase II trial of combined dabrafenib and trametinib demonstrated higher response rates and longer median PFS than dabrafenib monotherapy, with less cutaneous toxicity. Here, we review the clinical development of both drugs as monotherapies and in combination, and discuss their role in the management of BRAF-mutant melanoma.

Vemurafenib in the French temporary authorization for use metastatic melanoma cohort

Vemurafenib, a selective BRAF inhibitor, has recently shown an improved overall survival (OS) in metastatic melanoma with V600E mutation in phase 2 and 3 trials. Patients with BRAF V600E metastatic melanoma received vemurafenib orally, in the French temporary authorization for use program from April 2011 to April 2012. We analysed the clinical benefit and safety of vemurafenib. Secondary analyses included the impact of brain metastases on median OS and progression-free survival (PFS). Fifty patients were enrolled, of whom 20% had stage IIIC and 80% stage IV disease. The majority were men (58%), with a median age of 58 years (51-69). Forty-three patients had an Eastern Cooperative Oncology Group performance status of 0 or 1 (86%). Twenty patients had brain metastases (40%). Overall response rate was 53%. Complete response was achieved in five patients (10%), partial response in 21 patients (43%) and stable disease in seven patients (14%). Median OS was 7.5 months (95% confidence interval 5.6-12.7) and PFS was 3.6 months (95% confidence interval 2.9-5.9). Patients with brain metastasis had a response rate of 50% (nine partial response, one complete response), and median OS and PFS were, respectively, 4.3 and 3.1 months. Common adverse events were fatigue, arthralgia and cutaneous side effects. Sixteen per cent developed squamous cell carcinoma. Grade 3/4 was observed in 11 patients (22%). Six per cent required temporary discontinuation and/or dose reduction because of toxic effects. This study confirms the considerable clinical benefit of vemurafenib for patients with brain metastasis, with manageable toxicity.

COX-2 inhibition prevents the appearance of cutaneous squamous cell carcinomas accelerated by BRAF inhibitors

Keratoacanthomas (KAs) and cutaneous squamous cell carcinomas (cuSCCs) develop in 15–30% of patients with BRAFV600E metastatic melanoma treated with BRAF inhibitors (BRAFi). These lesions resemble mouse skin tumors induced by the two-stage DMBA/TPA skin carcinogenesis protocol; in this protocol BRAFi accelerates tumor induction. Since prior studies demonstrated cyclooxygenase 2 (COX-2) is necessary for DMBA/TPA tumor induction, we hypothesized that COX-2 inhibition might prevent BRAFi-accelerated skin tumors. Celecoxib, a COX-2 inhibitor, significantly delayed tumor acceleration by the BRAFi inhibitor PLX7420 and decreased tumor number by 90%. Tumor gene expression profiling demonstrated that celecoxib partially reversed the PLX4720-induced gene signature. In PDV cuSCC cells, vemurafenib (a clinically approved BRAFi) increased ERK phosphorylation and soft agar colony formation; both responses were greatly decreased by celecoxib. In clinical trials trametinib, a MEK inhibitor (MEKi) increases BRAFi therapy efficacy in BRAFV600E melanomas and reduces BRAFi-induced KA and cuSCC frequency. Trametinib also reduced vemurafenib-induced PDV soft agar colonies, but less efficiently than celecoxib. The trametinb/celecoxib combination was more effective than either inhibitor alone. In conclusion, celecoxib suppressed both BRAFi-accelerated skin tumors and soft-agar colonies, warranting its testing as a chemopreventive agent for non-melanoma skin lesions in patients treated with BRAFi alone or in combination with MEKi.

Vemurafenib and Radiosensitization

The BRAF inhibitor, vemurafenib, was recently approved for the treatment of patients with BRAFV600 metastatic melanoma. Wider use of this drug and longer follow-up periods of treatment are resulting in the emergence of a growing number of reports detailing new adverse effects. Cutaneous adverse effects are preeminent with UV-A-dependent phototoxicity, hyperkeratotic folliculitis, hand-foot skin reaction, hair changes, verrucous papillomas, keratoacanthomas, and squamous cell carcinomas. We report 2 cases of dermatitis occurring on a previously irradiated skin area in patients treated with vemurafenib for a BRAFV600-mutated metastatic melanoma. The first case occurred 10 days after a low dose of radiation was delivered that usually does not induce any radiodermatitis, suggesting radiosensitization by vemurafenib. The second case occurred 30 days after radiotherapy and was diagnosed as radiation recall dermatitis. Vemurafenib should be considered a potential cutaneous radiosensitizer and an inducer of radiation recall dermatitis. However, these adverse effects are easily managed with topical corticosteroids. Dose reduction or interruption of vemurafenib is not required. Further studies and reports will enlighten us as to whether this pharmacodynamic interaction between x-rays and vemurafenib is also seen with other BRAF or MEK inhibitors on the same mitogen-activated protein kinase pathway currently under development.

NRAS and BRAF mutations in atypical melanocytic lesions arising in melanoma patients treated with vemurafenib.

9017 Background: BRAF inhibition with targeted therapy has demonstrated improved overall survival in patients with BRAF mutant melanoma. The use of the selective BRAF inhibitors vemurafenib and dabrafenib are associated with a range of known and predictable cutaneous side effects, including squamous cell carcinomas often associated with RAS mutations. Preclinical evidence indicates that BRAF inhibitors may give rise to non-melanoma tumors by promoting MAPK activation in the tissues that lack mutant BRAF. Here we report atypical melanocytic lesions arising in patients treated with the BRAF inhibitor vemurafenib. Methods: To characterize the mutations of both the melanoma tumors and the atypical melanocytic lesions arising in patients with BRAF V600E/K melanoma treated with vemurafenib, a custom Sequenom panel designed to detect 74 mutations in 12 genes known to play a role in the pathogenesis of melanoma was applied to both melanoma and atypical melanocytic lesions for each patient. Results: We observed a total of six atypical melanocytic lesions (melanoma in situ and severely dysplastic nevi) in three patients undergoing treatment with vemurafenib. Mutations analysis in both pre-treatment tumor samples and on-treatment melanocytic lesions was feasible in two of the three patients. One patient with BRAF V600E metastatic melanoma developed two new melanoma in situ lesions while on vemurafenib, diagnosed 10 and 23 weeks after starting vemurafenib. Both on-treatment melanoma in situ lesions were found by Sequenom analysis to be BRAF wild-type, with a NRAS Q16R detected in one of the two lesions. Another patient’s pre-treatment primary melanoma demonstrated synchronous BRAF kinase domain mutations V600K and G466A, and CTNNB1 D32E mutation; a severely dysplastic nevus which arose after 25 weeks on vemurafenib in this patient showed only a BRAFG466A mutation. Conclusions: We identified an NRAS mutation and a rare BRAF kinase domain mutation in atypical melanocytic lesions that arose in patients treated with vemurafenib. Further studies are warranted to demonstrate a causal relationship between BRAF inhibition and the development or accelerated growth of atypical melanocytic lesions.

Abstract 2037: Establishment and characterization of paired mutant B-raf, vemurafenib-sensitive and -resistant patient-derived xenograft models.

Abstract Background: Vemurafenib is a recently approved anticancer therapy for B-RafV600E metastatic melanoma. Treatment with this agent increases overall patient survival compared with dacarbazine; however, most patients receiving vemurafenib progress within a year and are left with limited treatment options. Few validated screening tools exist to evaluate potentially beneficial therapies for these resistant/refractory patients. To address this deficiency we have generated a panel of paired mutant B-Raf vemurafenib-sensitive and -resistant patient-derived xenograft (PDX) models of metastatic melanoma and colorectal cancer. Each parent model was screened for activating mutations and all evaluated in vivo against vemurafenib. In addition, select model pairs were subjected to whole genome sequencing and RNA analysis to identify differences in genetic and expression profiles. Methods: Establishment of parent models was previously described. Vemurafenib-resistant PDX models (PDX-VR) were generated by in vivo administration of clinical-grade vemurafenib at increasing concentrations over limited tumor passages. Parental vemurafenib-sensitive models were screened for activating mutations of fifty-two known cancer genes using a PCR-based assay with customized primers. DNA and RNA was extracted from select model pairs and profiled and compared for alterations. Results: To date we have generated six B-RafV600E PDX-VR models (3 melanoma + 3 colorectal) with additional B-RafV600E and B-RafV600K PDX-VR models in development. In vivo studies evaluating vemurafenib in parent models reported notable tumor growth inhibition in all but one colorectal model (ST428), including tumor regressions in melanoma. PDX-VR models reported tumor growth similar to untreated controls at vemurafenib concentrations up to 150 mg/kg/day. Comparative analysis of paired models revealed some differences in DNA and RNA profiles. Conclusion: We have generated a panel of paired mutant B-raf vemurafenib-sensitive and -resistant patient-derived xenograft (PDX) models representing metastatic melanoma and colorectal cancer available as validated screening tools to evaluate potentially beneficial therapies for vemurafenib-resistant/refractory patients. Citation Format: Michael J. Wick, Teresa L. Vaught, Lizette Gamez, Justin Meade, Skylar Carden, Anthony W. Tolcher, Drew W. Rasco, Amita Patnaik, Alexander Miller, Ronald Drengler, Kyriakos P. Papadopoulos. Establishment and characterization of paired mutant B-raf, vemurafenib-sensitive and -resistant patient-derived xenograft models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2037. doi:10.1158/1538-7445.AM2013-2037

BRAFV600E protein expression and outcome from BRAF inhibitor treatment in BRAFV600E metastatic melanoma

Background:To examine the association between level and patterns of baseline intra-tumoural BRAFV600E protein expression and clinical outcome of BRAFV600E melanoma patients treated with selective BRAF inhibitors.Methods:Fifty-eight BRAFV600E metastatic melanoma patients treated with dabrafenib or vemurafenib on clinical trials had pre-treatment tumour BRAFV600E protein expression immunohistochemically (IHC) assessed using the BRAF V600E mutant-specific antibody VE1. Sections were examined for staining intensity (score 1–3) and percentage of immunoreactive tumour cells, and from this an immunoreactive score (IRS) was derived (intensity × per cent positive/10). The presence of intra-tumoural heterogeneity for BRAFV600E protein expression was also assessed. BRAFV600E expression was correlated with RECIST response, time to best response (TTBR), progression-free survival (PFS) and overall survival (OS).Results:Expression was generally high (median IRS 28 (range 5–30)) and homogeneous (78%). Expression of mutated protein BRAFV600E as measured by intensity, per cent immunoreactive cells, or IRS did not correlate with RECIST response, TTBR, PFS or OS, including on multivariate analysis. Heterogeneity of staining was seen in 22% of cases and did not correlate with outcome.Conclusion:In the current study population, IHC-measured pre-treatment BRAFV600E protein expression does not predict response or outcome to BRAF inhibitor therapy in BRAFV600E metastatic melanoma patients.