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Vemurafenib

Vemurafenib (INN), sold under the brand name Zelboraf, is a medication used for the treatment of late-stage melanoma.[2] It is an inhibitor of the B-Raf enzyme and was developed by Plexxikon.[2]

Mechanism of action

Vemurafenib causes programmed cell death in melanoma cell lines.[3] 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).[4] About 60% of melanomas have this mutation. It also has efficacy against the rarer V600K BRAF (the normal valine is replaced by lysine) 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.[5][6]

Resistance

Three mechanisms of resistance to vemurafenib (covering 40% of cases) have been discovered:

  • Cancer cells begin to overexpress cell surface protein PDGFRB, creating an alternative survival pathway.
  • A second oncogene called NRAS mutates, reactivating the normal BRAF survival pathway.[7]
  • Stromal cell secretion of hepatocyte growth factor (HGF).[8][9]

Side effects

At the maximum tolerated dose (MTD) of 960 mg twice a day 31% of patients get skin lesions that may need surgical removal.[2] The BRIM-2 trial investigated 132 patients; the most common adverse events were arthralgia in 58% of patients, skin rash in 52%, and photosensitivity in 52%. In order to better manage side effects, some form of dose modification was necessary in 45% of patients. The median daily dose was 1750 mg, 91% of the total daily MTD.[10]

History

In a phase I clinical study, vemurafenib (then known as PLX4032) was able to reduce numbers of cancer cells in over half of a group of 16 patients with advanced melanoma. The treated group had a median increased survival time of 6 months over the control group.[11][12][13][14]

A second phase I study, in patients with a V600E mutation in B-Raf, ~80% showed partial to complete regression. The regression lasted from 2 to 18 months.[15]

In early 2010 a Phase I trial[16] for solid tumors (including colorectal cancer), and a phase II study (for metastatic melanoma) were ongoing.[17]

A phase III trial (vs dacarbazine) in patients with previously untreated metastatic melanoma showed an improved rates of overall and progression-free survival.[18]

In June 2011, positive results were reported from the phase III BRIM3 BRAF-mutation melanoma study.[19] The BRIM3 trial reported good updated results in 2012.[20]

Further trials are planned including a trial of vemurafenib co-administered with GDC-0973 (cobimetinib), a MEK-inhibitor.[19] After good results in 2014, the combination was submitted to the European Medical Agency and the US Food and Drug Administration for marketing approval.[21]

Society and culture

Legal status

Vemurafenib was approved in the United States for the treatment of late-stage melanoma in August 2011,[22] making it the first drug designed using fragment-based lead discovery to gain regulatory approval.[23]

Vemurafenib was approved for use in Canada in February 2012.[24]

In February 2012, the European Commission approved vemurafenib as a monotherapy for the treatment of adults with BRAF V600E mutation positive unresectable or metastatic melanoma, the most aggressive form of skin cancer.[25]

In November 2017, the US Food and Drug Administration (FDA) approved vemurafenib for the treatment of people with Erdheim–Chester disease (ECD), a rare type of histiocytic neoplasm.[26][27]

Research

A trial combining vemurafenib and ipilimumab was stopped in April 2013 because of signs of liver toxicity.[28]

Treating Hairy Cell Leukemia (HCL)

In 2012, a grant from the Hairy cell leukemia Foundation supported the discovery of the BRAF mutation in classic HCL. This discovery charted a new path forward for many patients. It improved diagnosis and opened the door for additional therapies to be used in managing HCL.[29] In a phase II clinical trial, Memorial Sloan Kettering is testing Vemurafenib, plus Obinutuzumab, in patients with previously untreated classical hairy cell leukemia.[30] A separate clinical study treatment with only Vemurafenib (or monotherarpy) demonstrated high response rates in relapsed/refractory (R/R) hairy cell leukemia (HCL), achieving an overall response rate of 86%, including 33% complete response and 53% partial response. However, after a median follow-up of 40 months, 21 of 31 responders (68%) experienced relapse with a median relapse-free survival (RFS) of 19 months (range, 12.5-53.9 months).[31]

Further reading

References

  1. Australian Product Information: Zelboraf® (vemurafenib) Roche Products Pty Limited, 25 March 2020, retrieved 9 January 2023^
  2. Clinical efficacy of a RAF inhibitor needs broad target blockade in BRAF-mutant melanoma Nature, September 2010^
  3. BRAF silencing by short hairpin RNA or chemical blockade by PLX4032 leads to different responses in melanoma and thyroid carcinoma cells Molecular Cancer Research, May 2008^
  4. Metastatic melanoma - a review of current and future treatment options Acta Dermato-Venereologica, May 2015^
  5. RAF inhibitors prime wild-type RAF to activate the MAPK pathway and enhance growth Nature, March 2010^
  6. PLX4032, a selective BRAF(V600E) kinase inhibitor, activates the ERK pathway and enhances cell migration and proliferation of BRAF melanoma cells Pigment Cell & Melanoma Research, April 2010^
  7. Melanomas acquire resistance to B-RAF(V600E) inhibition by RTK or N-RAS upregulation Nature, December 2010 Researchers Uncover Drug-Resistance Mechanisms in BRAF Melanoma Genetic Engineering & Biotechnology News, November 25, 2010^
  8. Tumour micro-environment elicits innate resistance to RAF inhibitors through HGF secretion Nature, July 2012^
  9. Widespread potential for growth-factor-driven resistance to anticancer kinase inhibitors Nature, July 2012^
  10. BRIM-2 Upholds Benefits Emerging with Vemurafenib in Melanoma Oncology & Biotech News, July 2011, retrieved 2011-09-29^
  11. Drug hope for advanced melanoma BBC News, 2009-06-02, retrieved 2009-06-07^
  12. A Roller Coaster Chase for a Cure The New York Times, 2010-02-21^
  13. Cancer research. Melanoma drug vindicates targeted approach Science, December 2009^
  14. Phase I study of PLX4032: Proof of concept for V600E BRAF mutation as a therapeutic target in human cancer 2009 ASCO Annual Meeting Abstract, J Clin Oncol 27:15s, 2009 (suppl; abstr 9000), retrieved 2010-09-10^
  15. Inhibition of mutated, activated BRAF in metastatic melanoma The New England Journal of Medicine, August 2010 PLX4032: The Good News and the Bad News Corante, September 9, 2010^
  16. {{ClinicalTrialsGov|NCT00405587|Safety Study of PLX4032 in Patients With Solid Tumors}}^
  17. {{ClinicalTrialsGov|NCT00949702|A Study of RO5185426 in Previously Treated Patients With Metastatic Melanoma}}^
  18. Plexxikon Announces First Patient Dosed in Phase 3 Trial of PLX4032 (RG7204) for Metastatic Melanoma Plexxikon, 2010-01-08, retrieved 2011-02-03^
  19. Plexxikon and Roche Report Positive Data from Phase III BRAF Mutation Melanoma Study Genetic Engineering & Biotechnology News, Mary Ann Liebert Publishers, 6 June 2011^
  20. Vemurafenib Improves Overall Survival in Patients with Metastatic Melanoma retrieved 2012-12-17^
  21. Cobimetinib at exelixis.com retrieved 2015-02-04^
  22. FDA Approves Zelboraf (Vemurafenib) and Companion Diagnostic for BRAF Mutation-Positive Metastatic Melanoma, a Deadly Form of Skin Cancer Genentech, retrieved 2011-08-17^
  23. Vemurafenib: the first drug approved for BRAF-mutant cancer Nature Reviews. Drug Discovery, November 2012^
  24. Notice of Decision for ZELBORAF Health Canada, 11 March 2012, retrieved 21 April 2012^
  25. First Personalized Cancer Medicine Allows Patients with Deadly Form of Metastatic Melanoma to Live Significantly Longer Onco'Zine, The International Cancer Network, February 20, 2012, retrieved February 18, 2013^
  26. FDA approves first treatment for certain patients with Erdheim–Chester disease, a rare blood cancer U.S. Food and Drug Administration (FDA), retrieved 2018-05-20^
  27. Vemurafenib for BRAF V600-Mutant Erdheim-Chester Disease and Langerhans Cell Histiocytosis: Analysis of Data From the Histology-Independent, Phase 2, Open-label VE-BASKET Study JAMA Oncology, March 2018^
  28. Getting close and personal The Economist, January 4, 2014, retrieved 2016-04-15^
  29. Hairy Cell Leukemia: Celebrating Progress? HCLF Blog, July 29, 2022, retrieved July 25, 2022^
  30. {{ClinicalTrialsGov|NCT03410875|Hairy Cell Leukemia with Vemurafebib}}^
  31. Long-term outcomes in patients with relapsed or refractory hairy cell leukemia treated with vemurafenib monotherapy Blood, December 2022^