Dabrafenib [Tafinalar] and Trametinib [Mekinist] Approved for BRAF V600 Mutated Metastatic Melanoma

May 30, 2013

May 30, 2013 – From a Medscape News Release we learn today that two new drugs have been approved by the US Food and Drug Administration (FDA) for use in certain patients with metastatic or unresectable melanoma, along with a diagnostic test to identify patients who are suitable for treatment.

The new products, Dabrafenib [Tafinalar] and Trametinib [Mekinist], were both developed by GlaxoSmithKline. Both are orally available tablets, but they have slightly different mechanisms of action.

Dabrafenib [Tafinalar]  acts as a BRAF inhibitor and is approved for use in patients with melanoma whose tumors express the BRAF V600E gene mutation. It is seen as being a next-generation product but is in the same class as the first BRAF inhibitor to reach the market, Vemurafenib [Zelboraf] (Genentech).

Trametinib [Mekinist] has a related but slightly different mechanism and acts as a mitogen-activated, extracellular signal-regulated kinase inhibitor (MEK inhibitor). It is the first drug in this class to be approved and is indicated for use in patients with whose tumors express the BRAF V600E or V600K gene mutations.

Approximately half of melanomas arising in the skin have a BRAF gene mutation, the FDA notes in its approval notice. Alongside the new drugs, the agency also approved a genetic test, the THxID BRAF test, a companion diagnostic developed in collaboration with bioMérieux that will help determine wither a patient’s melanoma cells have the V600E or V600K mutation in the BRAF gene.

Melanoma is the leading cause of death from skin disease, the FDA adds. The National Cancer Institute estimates 76,690 Americans will be diagnosed with melanoma and 9480 will die from the disease in 2013.

Clinical Trial Data

Dabrafenib [Tafinalar]  was approved on the basis of data from the BREAK 3 study, conducted in 250 patients with previously untreated BRAF V600 mutation–positive metastatic melanoma. It showed that in such patients, Dabrafenib [Tafinalar]  significantly improved the median progression-free survival compared with chemotherapy with dacarbazine (5.1 vs 2.7 months; P < .0001). These results were published in July 2012 issue of the Lancet (2012;380:358-365).

The FDA notes that the most serious adverse effects reported in patients receiving Dabrafenib [Tafinalar] included an increased risk for cutaneous squamous cell carcinoma, fevers that may be complicated by hypotension, severe rigors, dehydration, kidney failure, and increased blood sugar levels requiring changes in diabetes medication or the need to start medicines to control diabetes.

The most common adverse effects reported in patients receiving Dabrafenib [Tafinalar]  included hyperkeratosis, headache, fever, joint pain, noncancerous skin tumors, hair loss, and hand–foot syndrome.

The pivotal study for Trametinib [Mekinist], the METRIC study, was a little different in that it was conducted in 322 patients who had already tried a prior regimen of chemotherapy. In this study, compared with chemotherapy, Trametinib [Mekinist] significantly improved progression-free survival as well as overall survival. The results were published in the New England Journal of Medicine.

The FDA notes that the most serious adverse effects reported in patients receiving Trametinib [Mekinist]  included heart failure, lung inflammation, skin infections, and loss of vision. Common adverse effects included rash, diarrhea, tissue swelling (peripheral edema), and skin breakouts that resemble acne.

The agency also noted that women of childbearing years should be advised that Dabrafenib [Tafinalar]  and Trametinib [Mekinist]  carry the potential to cause fetal harm. Men and women should also be advised that both drugs also carry the potential to cause infertility.

Being Investigated in Combination

Dabrafenib [Tafinalar]  and Trametinib [Mekinist]  have been approved for use as monotherapy, and not as a combination treatment, the FDA has emphasized. However, there is a lot of interest from clinicians in using both drugs together, and indeed the manufacturer is conducting a clinical trial with the combination.

Preliminary results from a clinical trial with the combination suggest that use of the 2 drugs together resulted in less toxicity, and specifically in fewer secondary skin cancers, than has been seen with  Vemurafenib [Zelboraf]  used alone.

GlaxoSmithKline is now conducting a phase 3 study (known as COMBI-AD) of the combination of Dabrafenib [Tafinalar]  and Trametinib [Mekinist]  in patients with BRAF V600 melanoma that has been completely removed by surgery. Such patients are at high risk for relapse, and the combination of drugs is being tested to see whether it can delay or prevent the recurrence of melanoma, the company noted.

Problem: Responses Are Short-lived

The new Dabrafenib [Tafinalar]  appears to be similar to the already-marketed Vemurafenib [Zelboraf], but there are important differences between the 2 BRAF inhibitors in their toxicity profiles, noted Kim Margolin, MD, from the Seattle Cancer Care Alliance in Washington..

Skin toxicities, particularly the emergence of low-grade squamous cancers and keratoacanthomas, which occurred in a substantial number of patients taking Vemurafenib [Zelboraf], appear to be quite unusual with Dabrafenib [Tafinalar], Dr. Margolin noted. However, a systemic “pyrexia reaction,” which is almost never seen with Vemurafenib [Zelboraf], has been seen in a substantial percentage of patients taking Dabrafenib [Tafinalar]. “We don’t know yet about the off-target mechanisms of these differences and how much may be due to the vehicle or the formulation for each of these oral agents,” she added.

However, the biggest problem with the BRAF inhibitors in the treatment of melanoma has been the lack of durable response: These drugs “tend to work for an average of 5 to 6 months,” Dr. Margolin noted. What to do when patients fail on these drugs remains a challenge, she added.

Ultimately, combination therapy with a BRAF inhibitor (such as Vemurafenib [Zelboraf]  or Dabrafenib [Tafinalar]) plus a MEK inhibitor (such as Trametinib [Mekinist]) is “likely to be most valuable for improved and lasting results,” according to Dr. Margolin. Firstclinical results along these lines have been published in the New England Journal of Medicine at the end of last year.


Patients on Vemurafenib [Zelboraf] Need Testing for RAS Mutations: Secondary Cancers a Major Concern

January 26, 2012

January 26, 2012 – A January 20, 2012 article in Medscape Medical New illustrates how personalized medicine can be tricky. The case is Vemurafenib [Zelboraf], which was introduced to the market together with an companion genetic test mid 2011 for the treatment of advanced melanoma in suitable BRAF mutation (V600E) positive patients only. In these patients, while melanoma therapy response rates are impressive, a new problem seems to arise, namely secondary tumours. Please read the article published  by Medscape Medical News on this topic.

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Patients with advanced melanoma who are treated with Vemurafenib [Zelboraf ]  should be tested for RAS mutations, according to an editorial published in the January 19 issue of the New England Journal of Medicine.

A study that accompanies the editorial reports that RAS mutations frequently occur in secondary skin tumors that develop in vemurafenib-treated patients.

The testing is necessary because there is “potential for secondary tumor development” that arises from treatment with vemurafenib and other BRAF inhibitors, writes Ashani T. Weeraratna, PhD, from the molecular and cellular oncogenesis program at The Wistar Institute in Philadelphia, Pennsylvania, in her editorial. These secondary skin tumors — namely, cutaneous squamous cell carcinomas and keratoacanthomas — are relatively benign, compared with melanoma, and are no reason to discontinue vemurafenib, said Dr. Weeraratna. However, testing will alert clinicians to which patients have RAS-driven secondary tumors.

The testing is important because patients with RAS mutations could also develop secondary cancers in organs beyond the skin, advised Dr. Weeraratna. “If patients have RAS mutations they should be monitored closely for any development of cutaneous squamous cell carcinomas in all organs,” she told Medscape Medical News.

“Although cutaneous squamous cell carcinomas are not deadly, these lesions can be life-threatening when they occur in other organs,” Dr. Weeraratna writes in her editorial. She discussed other potentially affected organs. “Squamous cell carcinomas can potentially arise in any organ with a squamous epithelium, essentially a layer of flattened epithelial cells that line the basement membranes of organs. A squamous epithelium is found most often in organs where rapid filtration and diffusion is necessary, such as the alveolar lining of the lungs and the glomerulus (kidney). Thus, squamous cell carcinomas can be found in organs such as the lungs, cervix, and esophagus, and also account for a large proportion of head and neck cancers,” Dr. Weeraratna explained.

Importantly, there is no evidence that vemurafenib triggers tumors in other organs. “It is as yet unclear whether the generation of squamous cell carcinomas in these organs, upon BRAF inhibitor therapy, occurs, but these data certainly alert us to that potential risk,” she said.

MEK Inhibitors May Help

In this study of melanoma patients, the investigators sought to characterize the molecular mechanism behind the development of secondary skin cancers in patients treated with vemurafenib.

They admit that a skin cancer drug that causes other skin cancers is unexpected. The development of cutaneous squamous cell carcinomas and keratoacanthomas “is the opposite of what would be expected from a targeted oncogene inhibitor,” write the study authors, led by Fei Su, PhD, from Hoffman-La Roche Pharmaceuticals in Nutley, New Jersey. In their search to understand this toxicity, the investigators analyzed the DNA of a sampling of these tumors and found a high rate of RAS mutations (21 of 35 tumors; 60%). “Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib,” write the authors.

“This study points out that BRAF inhibitors should only be used in patients who have cancers driven by BRAF mutations, and it raises the concern that cancers driven by RAS mutations (KRAS, HRAS, or NRAS) can be paradoxically activated instead of inhibited with this class of drugs,” said coauthor Antoni Ribas, MD, PhD, in email correspondence with Medscape Medical News. He is from the division of hematology–oncology at the UCLA Medical Center in Los Angeles, California.

Why patients treated with vemurafenib have such a high rate of RAS mutations in these secondary cancers is not known. However, the investigators performed animal-model studies that suggest that the development of RAS-mutation-driven secondary tumors might be prevented with a MEK inhibitor, another class of drugs. There might be “usefulness of combining a BRAF inhibitor with a MEK inhibitor to prevent this toxic effect” of secondary cancers, write the authors.

There has already been clinical investigation of this concept — a phase 2 study of the combination of the MEK inhibitor GSK1120212 and the RAF inhibitor GSK2118436 in metastatic melanoma. That study, which was presented at the 2011 annual meeting of the American Society of Clinical Oncology, and reported at that time by Medscape Medical News, showed that the toxicity of the combination seemed to be lower than that of either agent used alone.

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NEJM: Study

NEJM: Editoral

Medscape Medical News: Article


Vemurafenib [Zelboraf] Approved Together with a Companion Diagnostic Test by FDA for Advanced Melanoma in BRAF V600E Positive Patients

August 20, 2011

August 17, 2011 — The US Food and Drug Administration (FDA) has just approved the oral targeted therapy Vemurafenib [Zelboraf] for the first-line treatment of both metastatic and unresectable melanomas. The drug is specifically indicated for patients with melanoma whose tumors have V600E mutations in the BRAF gene. An estimated 50% of patients with melanoma have this type of BRAF mutation, which does not occur in normal cells. The drug is not indicated for use in melanoma patients negative for the BRAF V600E mutation. Vemurafenib [Zelboraf] is a BRAF inhibitor that blocks the function of the V600E-mutated BRAF protein.

Vemurafenib [Zelboraf] has been approved with a companion diagnostic test that will help determine whether a patient’s melanoma cells have the BRAF V600E mutation. The first-of-a-kind test is known as the cobas 4800 BRAF V600 Mutation Test (by Roche Molecular Systems).

The approval of Vemurafenib [Zelboraf] and the cobas test is a great example of how companion diagnostics can be developed and used to ensure patients are exposed to highly effective, more personalized therapies in a safe manner,” said Alberto Gutierrez, PhD, director of the Office of In Vitro Diagnostic Device Evaluation and Safety in the FDA’s Center for Devices and Radiological Health. The FDA’s approval of the cobas 4800 BRAF V600 Mutation Test was based on data from the same study that evaluated the safety and effectiveness of Vemurafenib [Zelboraf].

Vemurafenib [Zelboraf] was reviewed under the FDA’s priority review program that provides for an expedited 6-month review of drugs that may offer major advances in treatment or that provide a treatment when no adequate therapy exists, says the agency.

“This has been an important year for patients with late-stage melanoma. Vemurafenib [Zelboraf] is the second new cancer drug approved that demonstrates an improvement in overall survival,” said Richard Pazdur, MD, director of the Office of Oncology Drug Products in the FDA’s Center for Drug Evaluation and Research, in a press statement. “In March, we approved Ipilimumab [Yervoy], another new treatment for late-stage melanoma that also showed patients live longer after receiving the drug.”


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