Targeted BRAF/MEK Inhibitor Combination Achieves Long-Term Survival in Melanoma

Excerpt:

“More than one-fourth of patients with advanced BRAF V600-mutant melanoma remained alive at 5 years after treatment with the combination of dabrafenib (Tafinlar) and trametinib (Mekinist), long-term follow-up from a randomized trial showed.

“In the subgroup of patients with normal baseline lactate dehydrogenase (LDH) and fewer than 3 organ sites with metastases, half remained at alive at 5 years. No new safety signals emerged during long-term follow-up, as reported at the 2017 ASCO Annual Meeting in Chicago.”

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Melanoma: New Drugs and New Challenges (Part 1 of 2)


New targeted and immunotherapy drugs have changed the diagnosis of metastatic melanoma from a death sentence into a disease that can potentially be managed and even cured. Nevertheless, these new drugs do not work in all patients, or they may stop working after a transient response. This post (part one of two) will describe ongoing efforts to find drug combinations with higher efficacy than single drugs and decipher the mechanisms underlying drug resistance. Continue reading…


Binimetinib Improves PFS in NRAS-Mutated Metastatic Melanoma

Excerpt:

“The novel MEK inhibitor binimetinib resulted in improved progression-free survival (PFS) and response rates vs dacarbazine in patients with NRAS-mutated advanced unresectable/metastatic melanoma, according to results of an open-label phase III trial.

“ ‘NRAS mutations are present in approximately 20% of all patients with metastatic melanoma,’ said Reinhard Dummer, MD, of the University Hospital Zurich in Switzerland. ‘It activates the MAPK pathway and by this drives cell proliferation and anti-apoptotic mechanisms.’ Preclinical studies have shown that NRAS-mutant melanoma is sensitive to MEK inhibition, and binimetinib inhibits both MEK1 and MEK2. A phase II study showed clinical activity in NRAS-mutant metastatic melanoma.

“The NEMO trial included 402 patients randomized 2:1 to receive either binimetinib (269 patients) or dacarbazine (133 patients; 19 were not treated and were not evaluated for safety). Patients were either treatment-naive or had progressed on or after immunotherapy. The primary endpoint of the study was PFS. The results were presented at the 2016 American Society of Clinical Oncology (ASCO) Annual Meeting held earlier this month in Chicago (abstract 9500).”

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Distinct Features Associated With Benefit for BRAF/MEK Inhibition

Excerpt:

“With the development of novel targeted and immunotherapeutic agents that are more efficacious than traditional chemotherapy, treatment paradigms in melanoma have undergone major changes. Current recommendations for first-line systemic therapy for patients with advanced or metastatic melanoma consider BRAF mutation status, tumor growth rate, and the presence or absence of cancer-related symptoms.

“Immunotherapies with agents that block CTLA-4 or PD-1/PD-L1 checkpoints have been associated with durable responses in a subset of patients, and are often considered for patients with low-volume, asymptomatic metastatic melanoma. Targeted therapies, on the other side, are preferred for patients with BRAF-mutant tumors who have symptomatic disease and benefit from the rapid response associated with these agents.”

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Targeted Therapy Combinations Still Key in Metastatic Melanoma

“Combinations of targeted therapies continue to advance toward full regulatory approval for patients with metastatic or unresected melanoma, given the substantial benefits seen with these agents. At this time, the FDA is considering two applications for separate combinations of BRAF and MEK inhibiting agents for patients with unresectable or metastatic BRAFV600 mutation-positive melanoma.

“ ‘The future of the treatment of melanoma is clearly going to be in combinations, both for targeted therapy and for immunotherapy,’ said Jeffrey S. Weber, MD, PhD, who recently joined the NYU Langone Medical Center. ‘Already, there is an FDA-approved combination therapy that is targeted; that is dabrafenib and trametinib. There are new combinations coming up, mainly concerning CDK 4/6 and MEK inhibitors in NRAS-mutated but BRAF wild-type melanoma, which is an unmet medical need.’ “


Triple Combo: Two Targeted Drugs Plus Immunotherapy Show Promise in BRAF-Mutant Melanoma

“Results of a new study by UCLA researchers has found that a groundbreaking new triple combination therapy shows promising signs of more effectively controlling advanced melanoma than previous BRAF + MEK inhibitor or BRAF inhibitor + immunotherapy combos alone, and with increased immune response and fewer side effects.

“An estimated 70,000 new cases of metastatic melanoma are diagnosed each year in the United States, and of those 8,000 will die of the disease. About 50 percent of these men and women (or 35,000 a year) have a mutated protein called a BRAF mutation, which in most cases allows melanoma to eventually build up a resistance to many drug therapies.

“In the new study led by UCLA Jonsson Comprehensive Cancer Center member Dr. Antoni Ribas and colleague Dr. Siwen Hu-Lieskovan, UCLA scientists combined targeted therapies utilizing a BRAF inhibitor (dabrafenib) and MEK inhibitor (trametinib) with immunotherapy. The three together are shown to be more effective treatments by sensitizing the patients’ own immune system to enhance immunotherapy, and reduce the probability of the melanoma eventually developing resistance.

“This is a significant advance compared to previous drug combination findings, in which a combined BRAF inhibitor (vemurafenib) with immunotherapy (ipilimumab) caused serious liver toxicity in some patients, and the targeted therapies (BRAF and/or MEK inhibitors) became less effective and reactivated cancer cell growth.”


Moffitt Researchers Discover Mechanism Leading to Drug Resistance, Metastasis in Melanoma Patients

The gist: New research suggests that some melanoma patients might benefit from a treatment schedule that alternates BRAF inhibitor drugs with MEK inhibitor drugs. The scientists hypothesize that this schedule could help prevent drug resistance and metastasis. The researchers set out to figure out why patients who receive BRAF inhibitors develop more metastases than patients on standard chemotherapy. They found that unusually high activity of a protein called EphA2 on cancer cells may be the culprit. Taking away BRAF inhibitors seemed to lower the aggressiveness of these cells. So, periodically taking away BRAF inhibitors from patients might theoretically help stave off resistance and metastasis.

Moffitt Cancer Center researchers have discovered a mechanism that leads to resistance to targeted therapy in melanoma patients and are investigating strategies to counteract it. Targeted biological therapy can reduce toxicity and improve outcomes for many cancer patients, when compared to the adverse effects of standard chemotherapeutic drugs.  However, patients often develop resistance to these targeted therapies, resulting in more aggressive cells that can spread to other sites or cause regrowth of primary tumors.

“B-Raf is a protein that is frequently mutated in human cancers, leading to increased tumor cell growth, survival and migration.  Drugs that target B-Raf or another protein in the same network called MEK have proved effective in clinical trials. Several B-Raf and MEK inhibitors have been approved with the combination of a B-Raf and a MEK inhibitor being the current standard of care for patients with B-Raf mutant melanoma. However over time many patients become resistant to B-Raf and B-Raf/MEK inhibitor therapy.

“Moffitt researchers found that patients who are on B-Raf inhibitor drugs develop more new metastases than patients who are on standard chemotherapy. The researchers wanted to determine how this acquired resistance develops in order to devise better treatment options for patients. They found that melanoma cells that are resistant to B-Raf inhibitors tend to be more aggressive and invasive, thereby allowing the tumor to spread to a new organ site.  They used a large screening approach and discovered that this resistance and aggressive behavior was due to high activity of a cell surface protein called EphA2, which is also found on glioblastoma stem cells.”


New Standard in Melanoma: Combo of BRAF and MEK Inhibitors

The gist: Two new, similar melanoma treatments have been tested in clinical trials—research studies with volunteer patients. Both of the trials are focused on people with advanced melanoma whose tumors have mutations in the BRAF gene. Such patients are often treated with a targeted therapy called a BRAF inhibitor, but their tumors often become resistant and keep growing. In these two trials, the researchers hope that combining BRAF inhibitors with other targeted drugs known as MEK inhibitors might help patients avoid resistance. One of the trials tested a combination of the drugs vemurafenib and cobimetinib. The other trial combined dabrafenib and trametinib. In both trials, patients treated with the combination treatment fared better than patients treated with just a BRAF inhibitor alone.

“For patients with advanced melanoma that isBRAF-mutation positive, the combination of a BRAF and MEK inhibitor works better than a BRAF inhibitor alone. The data come from 2 phase 3 trials presented here at the presidential session of the European Society for Medical Oncology (ESMO) Congress 2014.

“Experts here say that such combinations should be the new standard of care in this patient population, which accounts for about 40% of all melanoma.

“At present, the first-line treatment for these patients is a BRAF inhibitor used alone, but while these drugs can elicit dramatic responses, they do not last, and after about 5 or 6 months, patients relapse. The tumor develops resistance to the drug via the MAPK pathway, and this is blocked by a MEK inhibitor. Adding a MEK inhibitor to the BRAF inhibitor from the beginning of treatment blocks this resistance pathway and improves outcomes.

“The 2 new trials are known as COMBI-v and coBRIM.

“Both studies used vemurafenib (Zelboraf, Roche/Plexxikon) as the single BRAF inhibitor, but each used a different combination of BRAF and MEK inhibitor.”


ESMO 2014 Press Release: New Data on Combination Treatments for Melanoma

The gist: Researchers tested a new melanoma treatment in a clinical trial—a research study with volunteer patients. The treatment combines the targeted drugs vemurafenib and cobimetinib. All of the patients who participated in the trial had melanoma tumors with mutations in the BRAF gene, as detected by molecular testing. The combination treatment proved more beneficial for these patients than vemurafenib alone.

“Combination therapy with both BRAF inhibitor vemurafenib and MEK inhibitor cobimetinib achieves greater progression-free survival and response rates than vemurafenib plus placebo in BRAF-mutation positive melanoma, according to phase III data presented at the ESMO 2014 Congress in Madrid, Spain.

“ ‘Before the results of this study, we knew that cobimetinib plus vemurafenib could be safely delivered together with highly promising rates of tumour shrinkage; however until the performance of a scientifically rigorous randomised trial the potential magnitude of this benefit could not be measured,’ says lead author Dr Grant McArthur, head of the Cancer Therapeutics Program at the Peter MacCallum Cancer Centre, Melbourne, Australia.

“The ongoing CoBRIM study enrolled 495 treatment-naive patients with BRAFV600-mutation-positive unresectable locally advanced or metastatic melanoma. Patients were randomised to received a 28-day treatment cycle of vemurafenib (960 mg, twice daily), and either cobimetinib or placebo (60 mg daily from days 1-21), with a primary end-point of progression-free survival.

“Patients in the combination arm of the study showed a significantly improved median progression-free survival of 9.9 months, compared to 6.2 months in the placebo arm, and a 49% reduction in the risk of progression. Researchers observed a response rate of 68% in the combination arm and 45% in the control arm, including a complete response in 10% of patients treated with combination therapy compared to 4% of patients treated with vemurafenib alone.”