American Melanoma Institute · 5 min read
What a BRAF V600 mutation means, the 3 approved pill combinations, their side effects, why resistance develops, and how doctors order them with immunotherapy.
About half of melanomas that start in the skin carry a change in a gene called BRAF. The National Cancer Institute cites a large genetic study, The Cancer Genome Atlas, in which 52% of skin melanoma samples carried a BRAF change. The changed gene makes a protein that is stuck in the on position and keeps telling the cell to divide.
Nearly all of these changes sit at a single spot in the gene, called V600, and the pathology report usually names the exact type, most often V600E or V600K. This mutation arises in the tumor and was not inherited. Doctors order the test on tumor tissue for stage III and stage IV melanoma, where the result affects treatment.
A BRAF inhibitor switches off the faulty BRAF protein. A MEK inhibitor blocks the next protein in the same growth signal chain. Melanoma cells can quickly find a way around a BRAF inhibitor used alone, and blocking the pathway at 2 points delays that escape. Trials showed the pairs work better and longer than a BRAF inhibitor alone, so doctors now prescribe them together.
These drugs only work when the V600 mutation is present. In a melanoma without it, a BRAF inhibitor can speed up growth signals, which is why the test comes first.
All are pills or capsules taken at home once or twice a day. No trial has compared the 3 pairs. Oncologists choose among them based on side effect patterns, other medicines a person takes, and insurance coverage.
Dabrafenib plus trametinib has an added use. After surgery for stage III melanoma with a BRAF mutation, 12 months of this pair lowers the chance of recurrence, as shown in the COMBI-AD trial.
Targeted therapy acts fast. The American Cancer Society notes that doctors favor these drugs when a melanoma needs to shrink quickly, for example when tumors are causing pain or pressing on an organ.
The weakness is resistance. Over months, melanoma cells find new routes to restart the growth signal, and the National Cancer Institute's summary for health professionals states that virtually all patients eventually acquire resistance. In the DREAMseq trial, responses to dabrafenib plus trametinib lasted a median of about 13 months.
Some people do far better than the median. A pooled 5-year analysis of 2 large trials of dabrafenib plus trametinib (Robert and colleagues, New England Journal of Medicine, 2019) concluded that about 1 in 3 patients with advanced melanoma had long-term benefit.
Fever is the signature side effect of dabrafenib plus trametinib. A 2025 meta-analysis (Belloni and colleagues, Cancers) found fever in about 40% of people taking the pair. The fevers often come with chills and tend to recur. Doctors manage them by pausing both drugs until the fever clears and then restarting.
Vemurafenib makes skin very sensitive to sunlight. In the same meta-analysis, about 29% of people taking vemurafenib had a photosensitivity reaction, a sunburn-like rash that can follow brief exposure, even through window glass. People on vemurafenib plus cobimetinib need strict sun protection every day. Encorafenib plus binimetinib has its own pattern, and oncologists sometimes switch a patient to a different pair when a particular side effect becomes hard to live with.
Across all 3 pairs, common effects include rash, fatigue, nausea, diarrhea and joint pain. BRAF inhibitors can cause skin thickening and new skin growths, including squamous cell skin cancers that are removed with minor surgery, so regular skin checks continue during treatment. MEK inhibitors can weaken the heart's pumping strength and can cause fluid to collect under the retina, which blurs vision. New vision changes or shortness of breath deserve a prompt call.
Most side effects ease within days of pausing the pills. This is a major difference from immunotherapy, where some side effects are permanent.
A person with BRAF-mutated advanced melanoma has 2 strong options, and for years nobody knew which to use first. The DREAMseq trial (Atkins and colleagues, Journal of Clinical Oncology, 2023) answered the question. It enrolled 265 patients with untreated BRAF V600 metastatic melanoma. Half started with the immunotherapy pair nivolumab plus ipilimumab and half started with dabrafenib plus trametinib, and each group switched to the other treatment if the melanoma grew.
An independent safety board stopped the trial early because the difference was clear. At 2 years, about 72% of patients who started with immunotherapy were alive, compared with about 52% of those who started with targeted therapy. Responses to immunotherapy also lasted much longer.
For most patients, oncologists now start with immunotherapy and hold targeted therapy in reserve. Exceptions exist. Targeted therapy may come first when the melanoma is growing fast and needs quick control, when a person cannot safely receive immunotherapy (for instance, because of a serious autoimmune disease), or when immunotherapy side effects have forced a stop. A 3-drug regimen that adds the immunotherapy drug atezolizumab to vemurafenib and cobimetinib is also FDA approved.
Timing with food differs between drugs, so follow the pharmacy instructions for your specific pair. Many common medicines interact with BRAF inhibitors, so bring a full list, including supplements, to the oncology pharmacist.
These drugs can harm a developing baby, and BRAF inhibitors may make hormonal birth control less reliable. Ask the care team which form of contraception to use during treatment. After a fever or rash, the team will tell you when to pause the pills and at what dose to resume.
