“Geoffrey R. Oxnard, MD, specializes in researching molecular mutations in non–small cell lung cancer (NSCLC) with a particular emphasis on prognostic and predictive biomarkers. Oxnard, who is an assistant professor of Medicine at Harvard Medical School and a thoracic oncologist at the Dana-Farber Cancer Institute, spoke with Targeted Oncology about the potential for BRAF-targeting therapies in NSCLC.
“TARGETED ONCOLOGY: What is the potential for utilizing currently available BRAF/MEK-targeted therapies in treating patients with NSCLC?
“Oxnard: Combination BRAF/MEK inhibitor therapy is a very compelling approach because combinations of BRAF and MEK inhibitors have clearly been shown to improve response rates and overall survival in melanomas harboring BRAF V600E mutations when compared with single-agent BRAF inhibition.”
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The gist: A drug called XL888 has shown promise for people with unresectable stage III/IV BRAF V600 mutation-positive melanoma. It was tested in a clinical trial with volunteer patients. It is hoped that XL888 could help prevent resistance to the drug vemurafenib (aka Zelboraf). In the trial, a combination of XL888 and vemurafenib was safely given to patients. The patients showed good response to the treatment.
“Exelixis, Inc. (EXEL) today announced preliminary results from a phase 1 investigator-sponsored trial (IST) evaluating the safety and activity of XL888, an Exelixis-discovered small molecule oral inhibitor of Heat Shock Protein 90 (HSP90), in combination with vemurafenib in patients with unresectable stage III/IV BRAF V600 mutation-positive melanoma. Safety and efficacy results support the further investigation of 90 mg of XL888 twice weekly (BIW) and vemurafenib 960 mg twice daily (BID) in additional studies that would include a third agent.
“The trial results were presented today by Keiran Smalley, Ph.D., an investigator on the trial and an associate professor at H. Lee Moffitt Cancer Center, Tampa, Florida, in a late-breaking oral presentation session at the Society for Melanoma Research 2014 International Congress, which is taking place November 13-16, 2014, in Zurich, Switzerland. Based on these results, as well as findings from coBRIM, the phase 3 pivotal trial of cobimetinib, an Exelixis-discovered MEK inhibitor, and vemurafenib in previously untreated metastatic melanoma patients with a BRAF V600 mutation, the Moffitt Center plans to initiate a phase 1b IST of the triple combination of vemurafenib, cobimetinib, and XL888 in a similar patient population.
“ ‘The BRAF inhibitor vemurafenib is active in BRAF-mutated malignant melanoma, but development of resistance is common. Preclinical studies led by Keiran Smalley, Ph.D. suggested that most BRAF inhibitor resistance mechanisms involve proteins that are clients of HSP90, and the preclinical evaluation of XL888 showed that it is highly active in vemurafenib-resistant melanoma models,’ said Jeffrey Weber, MD, Ph.D., director of the Donald A. Adam Comprehensive Melanoma Research Center at the Moffitt Cancer Center and Research Institute in Tampa, FL. ‘The current phase 1 data show that both drugs can be given together, and compelling initial response results suggest potential cooperative activity.’ “
The gist: A recent clinical trial with volunteer patients compared two treatments for metastatic melanoma. It showed that one of the treatments might give longer survival times for people whose tumors have mutations called BRAF V600E or BRAF V600K. This treatment combines the drugs dabrafenib and trametinib. In the trial, some patients were treated with the combination, and some were treated with only the drug vemurafenib (aka Zelboraf). People who took dabrafenib and trametinib lived several months longer than people who took vemurafenib. None of the patients had taken any previous treatments for their melanoma.
“The combination of dabrafenib and trametinib significantly extended OS compared with vemurafenib monotherapy in patients with treatment-naive metastatic melanoma who harbored BRAF V600E or V600K mutations, according to results of a randomized, open-label phase 3 study.
“The regimens demonstrated comparable toxicity profiles, researchers wrote.
“ ‘Together with the previously reported phase 2 and 3 trials of dabrafenib plus trametinib as compared with dabrafenib monotherapy, these data provide clear evidence for the benefit of this combination therapy over BRAF monotherapy in prolonging survival,’ Caroline Robert, MD, PhD, head of the dermatology unit at Institut Gustave-Roussy in Paris, and colleagues wrote.”
The gist: Two new targeted treatment approaches are showing promise for some lung cancer patients. Researchers are testing the targeted drug dabrafenib in a clinical trial—a research study with volunteer patients. Dabrafenib is meant to treat certain people who have already been treated for advanced non-small cell lung cancer (NSCLC) but who need additional treatment. The patients who participated in the trial had a tumor mutation called BRAF V600E. The study results supported dabrafenib as an effective treatment for these patients. In another clinical trial, researchers found that a combination of the drugs temsirolimus and neratinib had beneficial effects for people with advanced non-small cell lung cancer (NSCLC) whose tumors had mutations in the HER2 gene.
“The BRAF inhibitor dabrafenib has significant anti-tumour activity in patients with advanced BRAF V600E mutant non-small cell lung cancer whose disease has progressed after chemotherapy, according to phase II data presented at the ESMO 2014 Congress in Madrid, Spain.
” ‘Reports of lung cancers bearing mutations in BRAF have generated considerable interest because these mutations may be associated with increased sensitivity to BRAF tyrosine-kinase inhibiting agents,’ says lead author Dr David Planchard, pulmonary oncologist at the Gustav-Roussy Cancer Campus, Paris, France.
“Planchard says studies suggest that activating BRAF mutations are present in around 2% of lung carcinomas — approximately 80% of which are V600E mutations. The BRAF V600E mutations are frequently associated with shorter disease-free, overall survival, and lower response rates to platinum-based chemotherapy.
“This open-label phase II study involves patients with BRAF V600E mutant non-small cell lung cancer, treated with dabrafenib alone (150 mg, twice daily). The primary endpoint is investigator-assessed overall response rate, with secondary endpoints of progression-free survival, duration of response, overall survival, safety and tolerability, and population pharmacokinetics.”
The gist: Researchers tested a new melanoma treatment in a clinical trial—a research study with volunteer patients. The treatment combines the targeted drugs dabrafenib and trametinib. All of the patients who participated in the trial had inoperable stage IIIC or stage IV melanoma. Also, each patient’s tumors had one of two particular mutations in the BRAF gene, known as V600E and V600K. In the trial, patients who were treated with the combination therapy had significantly lower chances of their cancer worsening and lower chances of death.
“A world-first study in today’s New England Journal of Medicine heralds the efficacy of a targeted combination drug therapy after reporting major declines in the risk of disease progression and death in people with metastatic melanoma.
“The multi-centre, double-blind, randomised, phase 3 trial compared oral dabrafenib (150 mg twice daily) and oral trametinib (2 mg once daily) combination therapy with oral dabrafenib (150 mg twice daily) and placebo.
“All trial patients had inoperable stage 3C or 4 metastatic melanoma that had a BRAF gene mutation V600E or V600K. Among cancer patients with metastatic melanoma, about 40 per cent have a BRAF gene mutation – an abnormality that assists some melanoma tumours to grow and spread.
“Led by Associate Professor Georgina Long of Melanoma Institute Australia at the University of Sydney, the finding affirms accumulating evidence of the efficacy of targeted combination therapies in extending life and halting disease progression in patients with cancers that carry genetic mutations that resist monotherapies.”
“Patients with metastatic melanoma treated with dabrafenib demonstrated improved quality of life compared with those who received dacarbazine, according to phase 3 study results.
“Initial analyses of the BREAK-3 trial indicated dabrafenib (Tafinlar; GlaxoSmithKline) prolonged median PFS compared with dacarbazine (DTIC) in patients with BRAFV600E-mutant metastatic melanoma (5.1 months vs. 2.7 months; HR=0.30; 95% CI, 0.18-0.53).”
Johannessen CM, Johnson LA, Piccioni F, Townes A, et al. Nature. Nov 3, 2013.
“Malignant melanomas harbouring point mutations (Val600Glu) in the serine/threonine-protein kinase BRAF (BRAF(V600E)) depend on RAF–MEK–ERK signalling for tumour cell growth1. RAF and MEK inhibitors show remarkable clinical efficacy in BRAF(V600E) melanoma2, 3; however, resistance to these agents remains a formidable challenge2, 4. Global characterization of resistance mechanisms may inform the development of more effective therapeutic combinations. Here we carried out systematic gain-of-function resistance studies by expressing more than 15,500 genes individually in a BRAF(V600E) melanoma cell line treated with RAF, MEK, ERK or combined RAF–MEK inhibitors. These studies revealed a cyclic-AMP-dependent melanocytic signalling network not previously associated with drug resistance, including G-protein-coupled receptors, adenyl cyclase, protein kinase A and cAMP response element binding protein (CREB). Preliminary analysis of biopsies from BRAF(V600E) melanoma patients revealed that phosphorylated (active) CREB was suppressed by RAF–MEK inhibition but restored in relapsing tumours. Expression of transcription factors activated downstream of MAP kinase and cAMP pathways also conferred resistance, including c-FOS, NR4A1, NR4A2 and MITF. Combined treatment with MAPK-pathway and histone-deacetylase inhibitors suppressed MITF expression and cAMP-mediated resistance. Collectively, these data suggest that oncogenic dysregulation of a melanocyte lineage dependency can cause resistance to RAF–MEK–ERK inhibition, which may be overcome by combining signalling- and chromatin-directed therapeutics.”
Melanomas commonly stop responding to targeted therapies, and a new study helps explain why. The researchers linked resistance to BRAF and MEK inhibitors in people with two genetic abnormalities: extra copies of BRAF-V600E, the most common melanoma mutation, as well as a new mutation called MEK2-Q60P. Encouragingly, the researchers also found that adding a third treatment (a PI3K inhibitor) to the mix makes melanomas stop growing in mice. While the team cautions that the solution is unlikely to be as simple of a triple inhibitor treatment for people, this work could help researchers find ways of overcoming drug resistance in melanomas.
A small subset of patients with non-small cell lung cancer (NSCLC), especially those with lung adenocarcinoma, have a mutation in the BRAF gene called V600E. An ongoing phase II clinical trial is investigating whether the BRAF inhibitor dabrafenib (Tafinlar) benefits patients with this mutation. Tafinlar is currently approved for treatment of the skin cancer melanoma. Recently released trial results show that the drug partially shrank tumors in 40% of advanced NSCLC patients whose cancer had worsened after at least one round of chemotherapy. Another 20% of study participants maintained stable disease (tumors neither shrinking nor growing). Almost half of the patients currently remain on the treatment. These findings are the first evidence that treatments targeting the BRAF V600E mutation may be effective in lung cancer.