Vemurafenib: Result unchanged despite new data

In continuation of my update on Vemurafenib

Longer survival, but also major side effects

The drug approved since February 2012 can be an option for adults whose melanoma cannot be removed by surgery or has formed secondaries (metastases) and in whose cancer a change (mutation) has occurred in a certain gene (BRAF-V600). G-BA had specified the drug dacarbazine as the appropriate comparator therapy.

In its first AMNOG assessment in June 2012, the Institute concluded that vemurafenib had major advantages in overall survival, but also major disadvantages in the form of side effects. Overall, this resulted in an indication of a considerable added benefit.

Vemurafenib: Result unchanged despite new data

Melanomas that develop resistance to vemurafenib also become addicted to the drug

Vemurafenib (marketed as Zelboraf) is a B-Raf enzyme inhibitor developed by Plexxikon (now part of the Daiichi Sankyo group) and Hoffmann–La Roche for the treatment of late-stage melanoma. The name "vemurafenib" comes from V600E mutated BRAF inhibition.

Vemurafenib received FDA approval for the treatment of late-stage melanoma on August 17, 2011,  Health Canada approval on February 15, 2012 and on February 20, 2012, the European Commission approved vemurafenib as a monotherapy for the treatment of adult patients with BRAF V600 mutation positive unresectable or metastatic melanoma, the most aggressive form of skin cancer....

Mechanism : Vemurafenib has been shown to cause programmed cell death in melanoma cell lines. Vemurafenib interrupts the B-Raf/MEK step on the B-Raf/MEK/ERK pathway if the B-Raf has the common V600E mutation.

Vemurafenib only works in melanoma patients whose cancer has a V600E BRAF mutation (that is, at amino acid position number 600 on the B-Raf protein, the normal valine is replaced by glutamic acid). About 60% of melanomas have this mutation. It also has efficacy against the rarer BRAF V600K mutation. Melanoma cells without these mutations are not inhibited by vemurafenib; the drug paradoxically stimulates normal BRAF and may promote tumor growth in such cases. 

Melanomas that develop resistance to vemurafenib also become addicted to the drug

Drug combinations show promise against metastatic melanoma

In continuation of my update on Vemurafenib..

A Phase I study in 44 patients shows that the combination of the MEK inhibitor GDC-0973  (see structure) and vemurafenib can be delivered safely, Dr Rene Gonzalez of the University of Colorado Cancer Center, Denver, and colleagues report.

"BRAF inhibition has resulted in high response rates and improved survival in patients with BRAF mutated melanoma," Dr Gonzalez said. "One of several mechanisms of resistance has been reactivation of the MAPK pathway. Preclinical models show that combined inhibition of BRAF and MEK can delay the acqusition of resistance compared to BRAF inhibitor monotherapy. Inhibition of the pathway downstream from BRAF with the MEK inhibitor GDC-0973 could theoretically overcome or delay this resistance mechanism and improve outcomes."

The study was not designed to evalate efficacy. "While early data in a small number of patients did show tumor reduction, it would be premature to comment on efficacy based on these preliminary results and further research is warranted," Dr Gonzalez said.

Drug combinations show promise against metastatic melanoma

FDA Approves Zelboraf - Potent New Melanoma Drug

Plexxikon Inc., a member of the Daiichi Sankyo Group, today announced that applications for market approval for vemurafenib ( PLX4032/RG7204, see below structure) for the treatment of metastatic melanoma have been submitted to the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA). The company had 

Phase 2 and 3 trials (BRIM2 and BRIM3) that evaluated vemurafenib in patients with BRAF ^V600 mutation-positive melanoma, as determined by the cobas 4800 BRAF ^V600 Mutation Test.

 Earlier this year, the company reported positive data from an interim analysis of BRIM3 which showed that the study met the pre-specified criteria for co-primary endpoints for BRIM3 for progression-free survival and overall survival, and that the safety profile was generally consistent with the previous vemurafenib studies. Based on these results, the data safety monitoring board for the trial recommended early termination of the trial and allowed dacarbazine-treated patients to immediately cross over to vemurafenib treatment. BRIM2 results reported earlier showed a 52 percent confirmed response rate, with tumor shrinkage in the majority of patients, consistent with results from earlier studies. 

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Positive results from Plexxikon's vemurafenib Phase 2 and 3 trial against metastatic melanoma

We know that, PLX-4032(RG7204, Vemurafenib) is a highly selective inhibitor of BRAF kinase activity, with an IC50 of 44 nmol/L against V600E-mutant BRAF. BRAFV600E cancer-causing mutation occurs in most melanomas and about eight percent of all solid tumors....

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