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# BRAF and MEK inhibitors

Oral drugs that block two steps of the MAPK pathway in BRAF V600-mutant melanoma, lung, thyroid and colorectal cancer; usually given as a pair.

Updated Nov 1, 2026

## What they are

BRAF inhibitors (vemurafenib, dabrafenib, encorafenib; suffix «-rafenib») block mutant BRAF; MEK inhibitors (trametinib, cobimetinib, binimetinib, selumetinib; suffix «-metinib») block the next kinase in the chain. Standard pairs are dabrafenib + trametinib, vemurafenib + cobimetinib and encorafenib + binimetinib.

## Mechanism of action

The RAS–RAF–MEK–ERK (MAPK) pathway carries growth signals to the nucleus. About half of melanomas carry a BRAF mutation, most often V600E, which keeps BRAF active without any upstream signal. BRAF inhibitors block the mutant kinase; MEK inhibitors bind an allosteric pocket of MEK1/2, downstream. Single-agent resistance appears within months, often by reactivating the pathway; blocking two steps together delays resistance and lowers the rate of new skin squamous cell cancers seen with BRAF inhibitors alone.

Target: Mutant BRAF (V600E/K) and the MEK1/MEK2 kinases of the MAPK pathway

## Key points

- Only for tumours with a BRAF V600 mutation; not for BRAF wild-type melanoma.
- BRAF inhibitors alone cause new cutaneous squamous cell carcinomas; the BRAF + MEK pair delays and reduces them.
- Dabrafenib + trametinib: fever is the typical reaction.
- MEK inhibitors: rash, diarrhoea, reduced heart function and eye toxicity.
- Encorafenib with cetuximab is used in BRAF V600E colorectal cancer.

## Drugs in this class

- [**Dabrafenib** An oral inhibitor of mutant BRAF, paired with trametinib in BRAF V600 melanoma, lung and thyroid cancer. Watch fever… BRAF serine/threonine kinase (V600E/K mutants)](https://durgical.com/en/pharmacology/dabrafenib/)
- [**Encorafenib** A BRAF inhibitor given with binimetinib in BRAF V600 melanoma and lung cancer, and with cetuximab in BRAF V600E… BRAF serine/threonine kinase (V600E mutant), also wild-type BRAF and CRAF](https://durgical.com/en/pharmacology/encorafenib/)
- [**Trametinib** The first MEK inhibitor: an oral drug, usually with dabrafenib, for BRAF V600 melanoma, lung and thyroid cancer. Watch… MEK1 and MEK2 (MAP2K1/2) kinases](https://durgical.com/en/pharmacology/trametinib/)
- [**Binimetinib** A MEK1/2 inhibitor always given with encorafenib in BRAF V600 melanoma and lung cancer. Watch heart, eyes, muscles… MEK1 and MEK2 (MAP2K1/2) kinases](https://durgical.com/en/pharmacology/binimetinib/)

## Others in the class

- vemurafenib
- cobimetinib
- selumetinib

## Test yourself

Think of the answer, then tap the question to see it.

## Why are a BRAF inhibitor and a MEK inhibitor given together?

Blocking two steps of the MAPK pathway delays resistance and reduces new skin cancers caused by BRAF inhibitors alone.

## Which BRAF mutation is the classic target of these drugs?

V600E (valine 600 replaced by glutamic acid); V600K is also covered.

## Which suffixes identify BRAF and MEK inhibitors?

«-rafenib» for BRAF and «-metinib» for MEK.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01EC) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01EE) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [Dabrafenib Mesylate - NCI](https://www.cancer.gov/about-cancer/treatment/drugs/dabrafenib) (National Cancer Institute, 2024).

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