Vemurafenib (Zelboraf)

Medicine at a glance

Vemurafenib is a targeted medicine taken by mouth, usually twice daily. Zelboraf is its verified brand. It blocks an altered form of the BRAF protein, which helps transmit growth signals within cells. Testing the cancer for the appropriate BRAF change is an essential part of selecting treatment.

Some people receive vemurafenib alone; others receive it with cobimetinib, a medicine that blocks another part of the same pathway. The two medicines have different dosing calendars and some different risks. Follow the written plan for each one.

Important precautions include sun protection, regular skin checks, heart-rhythm monitoring and liver and kidney blood tests. Joint pain, tiredness, rash, hair changes and digestive symptoms can occur. Targeted treatment is not free of serious side effects, but early reporting gives the team more options to manage them.

What vemurafenib is and how it works

BRAF forms part of a chain of proteins that carries messages controlling cell growth. Certain changes, called mutations, can make the protein send growth signals too strongly. Vemurafenib blocks particular altered forms of BRAF, helping interrupt this signalling. It is not a treatment for every BRAF change or for every cancer.

The medicine is a small-molecule targeted therapy, not conventional chemotherapy or an immune-checkpoint treatment. A cancer's molecular test results help the specialist decide whether blocking BRAF is appropriate. The exact variant, diagnosis and other clinical information all matter.

Cobimetinib, when prescribed alongside vemurafenib, blocks MEK proteins further along the pathway. No treatment can guarantee a response, and cancer cells can develop resistance. Clinical reviews and scans show whether treatment is helping.

How the team decides whether it is suitable

The oncologist reviews your diagnosis, tumour test, earlier treatment, symptoms and general health. Current prescribing information requires a relevant BRAF V600 change; the exact accepted result depends on the treatment setting. European information notes limited evidence for rare V600 variants other than V600E and V600K. Do not interpret a test report without the specialist.

Using a BRAF inhibitor in the wrong molecular setting can stimulate rather than suppress growth signals. This is why testing is a safety requirement, not simply an administrative step. Tell the team about any other current or previous cancer, including a blood cancer, because its biology may affect the decision and monitoring.

Do not take it with a known allergy to vemurafenib or its ingredients. Treatment should not start with uncorrectable blood-salt abnormalities, long-QT syndrome, markedly prolonged QT or medicines that prolong QT. The team must resolve these risks first. Discuss liver, kidney or eye disease and previous cancers. Severe liver or kidney impairment has limited dosing evidence. This guide describes adult care; safety and effectiveness in children are not established.

Before treatment starts

Bring a complete list of medicines, vitamins, herbal remedies and supplements. Include occasional treatments for nausea, infection, sleep or pain, because some can affect heart rhythm or change vemurafenib levels. Tell the team about allergies, pregnancy possibility, breastfeeding and any radiotherapy you have had or expect to receive.

Baseline checks include an ECG, which records the heart's electrical activity, and blood tests for salts such as potassium, magnesium and calcium. Liver function, kidney function and blood counts are assessed. A skin examination documents existing lesions. The team may also examine the mouth and lymph nodes and arrange other checks for additional cancers according to the clinical plan.

If cobimetinib is included, additional assessments look at heart pumping function, eyes and a muscle enzyme called creatine phosphokinase, or CPK. Abnormal CPK can indicate muscle injury. These are separate from an ECG's assessment of electrical rhythm.

Before leaving, check the dose, food plan, repeat prescriptions and urgent-contact details. Ask when to withhold a dose and who authorises restarting.

How to take vemurafenib

Dose, timing and food

A usual starting dose is 960 mg twice a day, around 12 hours apart. Each Zelboraf tablet contains 240 mg, so this example means four tablets in the morning and four in the evening. Your dose may be lower after a treatment interruption or side effects. Common clinician-directed reductions are to 720 mg and then 480 mg twice daily; never make these changes yourself.

Swallow tablets whole with water. Do not chew or crush them. If swallowing becomes difficult, contact the oncology pharmacist before altering a tablet. The current labels do not provide a routine home-dispersion or feeding-tube method.

The US label permits taking vemurafenib with or without a meal. European guidance also permits either, but advises against regularly taking both daily doses on an empty stomach. Agree a consistent eating and dosing routine with the pharmacist rather than repeatedly changing between fed and fasting conditions. This is not the same food rule as for every other BRAF medicine.

Treatment usually continues while it is helping and side effects remain acceptable. Dose pauses and restarts require an individual plan. If you miss several doses, have difficulty obtaining supplies or cannot keep tablets down, tell the team rather than trying to catch up later.

A missed dose, vomiting or an extra dose

If more than four hours remain before the next dose, take the forgotten dose when remembered. If less than four hours remain, skip it. At exactly four hours, the US patient leaflet says to skip; professional and European wording differs. Follow your supplied leaflet or pharmacist’s instructions. Never double a dose.

If you vomit after taking vemurafenib, do not take a replacement dose. Continue with the next scheduled dose. Report repeated vomiting, because dehydration and inability to absorb treatment need assessment. Contact the team promptly after an accidental extra dose, giving the strength, number of tablets and time taken.

Storage and the companion medicine

Keep tablets in their original packaging, away from children and pets, moisture and excessive heat. US guidance specifies 20–25°C (68–77°F), allowing short excursions to 15–30°C (59–86°F). Follow the supplied label for your product; do not leave it in a hot car. Ask the pharmacy how to return or dispose of unused tablets safely.

Cobimetinib commonly follows a once-daily schedule for 21 days, then seven days off, within a 28-day cycle. Vemurafenib usually continues through that planned cobimetinib break. Do not stop both simply because one calendar shows a rest week. Unplanned pauses for side effects may follow different rules. Cobimetinib's missed-dose instructions also differ from vemurafenib's and vary between US and European leaflets; use its own prescribed plan.

Monitoring and checking whether treatment is working

Vemurafenib can prolong the QT interval, part of the heart's electrical cycle. Blood salts and ECGs are therefore checked before treatment and again during it. The US label specifies checks around day 15, monthly for the first three months, then every three months or more often when needed, including after relevant dose changes.

European guidance starts repeat ECG and salt checks after one month and after dose changes, with additional monitoring particularly in people with moderate or severe liver impairment. Your team decides the schedule appropriate to your product and risk factors. Vomiting, diarrhoea and new medicines can change the risk between planned checks.

Liver tests are checked before treatment and usually monthly. Kidney function is checked before treatment and periodically afterwards. Blood counts may also need monitoring, particularly if another blood disorder is present. Skin review is typically every two months under US guidance and monthly under European guidance; follow-up can continue for six months after stopping.

With cobimetinib, heart pumping is measured before treatment, after one month and about every three months thereafter. Regular eye assessments and CPK and kidney tests are also needed. Report symptoms promptly even when a recent test was normal.

Scans and clinical assessments judge benefit. A lower dose may help treatment remain tolerable; it does not by itself prove that the medicine is ineffective.

Common side effects and practical management

Sun sensitivity and skin discomfort

Vemurafenib can make skin unusually sensitive to sunlight, causing a burn-like reaction after exposure that previously seemed harmless. Avoid unnecessary sun exposure, seek shade and wear protective clothing and a hat. Use broad-spectrum UVA/UVB sunscreen and lip balm with at least SPF 30 when outdoors, reapplying according to the product instructions. Avoid sunbeds. Cobimetinib can add to this risk.

An itchy rash, dry skin, thickened areas, wart-like growths or tender skin can occur. Use a gentle cleanser and unperfumed moisturiser. Do not cut off or treat a new growth yourself with a wart-removal product. Ask the team to assess it. Report sunburn that is painful, blistered or interfering with daily life; the treatment plan may need changing.

Joint pain, muscle aches and fatigue

Joint pain and stiffness can affect walking, sleep or hand use. Tell the team how symptoms affect you, and ask which pain medicine is suitable. Gentle movement and pacing activities may help. Avoid assuming new severe pain is simply an expected side effect.

Fatigue may fluctuate. Plan demanding tasks for better periods, take breaks and accept practical help. Blood tests and clinical review may identify treatable contributors. Severe muscle pain or weakness, particularly with dark urine when taking cobimetinib, requires urgent contact because it can indicate muscle breakdown.

Nausea, diarrhoea and appetite

Take prescribed anti-sickness medicine as directed. Small meals and regular sips may be easier to manage, within your agreed dosing routine. Ask for dietary support if appetite or weight is falling.

Record loose stools and use the team's diarrhoea plan early. Drink regularly unless you have a fluid restriction. Severe diarrhoea, inability to keep fluids down, little urine, dizziness, fever or blood in the stool needs urgent assessment. Do not simply increase over-the-counter medicine while these warning signs are present.

Hair and mouth changes

Hair thinning or loss can occur. Gentle hair care, head coverings or other support may help; changes vary between people. Protect exposed scalp from the sun. Mouth soreness may respond to a soft toothbrush and gentle, non-irritating mouth care. Tell the team if ulcers or pain make eating difficult.

Important risks that need medical assessment

Heart rhythm and electrolyte changes

QT prolongation can lead to a dangerous rhythm. New palpitations, light-headedness or near-fainting requires immediate contact. Fainting, chest pain or severe breathlessness is an emergency. Low potassium, magnesium or calcium and other medicines can increase the risk. Do not start mineral supplements without advice and blood-test guidance.

The team may correct salts, change interacting medicines, withhold vemurafenib or restart at a reduced dose. Persistent or marked ECG changes can require permanent discontinuation. The decision depends on the ECG and your clinical situation, not simply how you feel.

Severe allergy and skin reactions

A severe allergic reaction can occur during treatment or after restarting. Facial or throat swelling, wheezing, breathing difficulty or collapse needs emergency care. Do not take another dose while seeking urgent assessment for a suspected severe reaction.

Rare severe skin reactions include Stevens–Johnson syndrome, toxic epidermal necrolysis and DRESS. These can involve blistering or peeling skin, sores in the mouth or eyes, a widespread rash, fever, facial swelling or internal-organ problems. Stop taking the medicine and seek immediate medical care if these symptoms occur. Severe confirmed allergic or skin reactions require permanent discontinuation under specialist care.

New skin lesions and other cancers

Vemurafenib can increase the risk of new skin cancers and may promote some other cancers. Report a new lump, wart-like lesion, non-healing sore, bleeding patch or changing mole. Many new skin lesions can be removed while cancer treatment continues, but examination and laboratory assessment of the lesion are important. Do not assume every new spot is harmless or that every lesion means vemurafenib must stop.

The team also checks for cancers outside the skin. Report persistent unexplained symptoms such as a new mouth lesion, neck lump, swallowing difficulty or abnormal bleeding. European guidance includes additional head and neck examinations, chest imaging and selected other examinations.

Liver, kidneys, eyes and inflammation

Liver injury can initially show only on blood tests. Yellow eyes or skin, dark urine, pale stools, upper abdominal pain, appetite loss or unusual bruising requires immediate contact. Reduced urine or new swelling may indicate a kidney problem. Severe abdominal pain, especially with vomiting, can indicate pancreatic inflammation and needs urgent assessment.

Eye inflammation can cause pain, redness, light sensitivity or blurred vision. Report these symptoms immediately; sudden loss of vision is an emergency. Do not use leftover steroid eye drops without an examination. Vemurafenib can also cause retinal vein blockage. Cobimetinib adds risks including fluid under the retina; confirmed retinal vein blockage requires permanent discontinuation of that partner under US guidance.

Sarcoidosis, a condition in which clusters of inflammatory cells form in tissues, has been reported. New persistent cough, breathlessness, unusual skin lumps or eye symptoms needs assessment rather than being assumed to be cancer progression or a minor side effect. Low white blood cells can also occur; fever or shaking chills needs urgent contact because infection is another possible cause of illness.

Hands, feet, radiotherapy and partner risks

Thickened tissue in the palm can pull fingers towards the hand, called Dupuytren's contracture. Similar thickening in the sole is called plantar fascial fibromatosis. Report nodules, tightening, pain or reduced movement early, especially if you have had these problems before. Some cases interfere substantially with function and need a treatment change.

Vemurafenib can intensify reactions to radiotherapy, including in areas treated previously. These reactions can affect skin and internal organs. Tell both oncology teams about past and planned radiotherapy; they must coordinate any interruption. New pain, severe skin inflammation or breathing symptoms after radiotherapy needs prompt assessment. Do not use an internet-derived number of days to pause treatment yourself.

Cobimetinib can additionally weaken heart pumping, cause serious bleeding and injure muscles. New ankle swelling, rapid weight gain, breathlessness, unusual bleeding, severe muscle pain or dark urine needs immediate advice. Heavy bleeding, vomiting blood, black stools or collapse requires emergency care.

Other medicines, supplements and vaccines

Vemurafenib interacts with medicines through liver enzymes and transport proteins. Some combinations raise its level and toxicity; others lower its level and may reduce treatment effectiveness. Have all new treatments checked, including antibiotics, antifungals, antiviral medicines and herbal remedies.

US guidance advises avoiding strong CYP3A4 inhibitors and inducers. Examples needing particular attention include certain azole antifungals, ritonavir, rifampicin, carbamazepine, phenytoin and St John's wort. European guidance also avoids strong inducers, while strong inhibitors require caution and close monitoring. Any dose adjustment needed for an unavoidable interaction is a prescribing decision.

Vemurafenib can increase levels of medicines such as tizanidine, theophylline and digoxin. Some combinations should be avoided because a small change in blood concentration can be harmful. Warfarin may need extra INR tests, and hormonal contraception may become less reliable. Drugs that prolong QT need particular scrutiny, including some anti-sickness and infection treatments. Do not stop an essential medicine without an agreed replacement plan.

Cobimetinib has additional CYP3A interactions. Avoid grapefruit juice when taking that partner, according to its European information. Concurrent ipilimumab and vemurafenib is not recommended in European guidance because of increased liver toxicity. Tell the team about any other immunotherapy plan.

Discuss vaccines with the oncology team before arranging them. Live-vaccine suitability depends on the complete treatment and immune status; non-live vaccines may be offered with appropriate timing. There is no single timetable that applies to every person taking a targeted medicine.

Everyday life during treatment

Keep a dosing record and plan outdoor activities around shade and sun protection. Check alcohol advice with the team because liver injury and other medicines may affect what is appropriate.

Gentle exercise and flexible work arrangements can help, but avoid driving or machinery when fatigued, dizzy or visually impaired. Tell the team if pain or hand tightening limits daily tasks. Emotional strain and changes in appearance or intimacy deserve support; ask about counselling and practical assistance.

For travel, carry labelled medicine with a prescription, maintain suitable storage conditions and plan blood tests and access to urgent care. Tell dentists and other clinicians about cancer treatment before procedures. Do not create a treatment break for travel or dental work without oncology advice.

Pregnancy, contraception, fertility and breastfeeding

Vemurafenib can harm an unborn baby. Discuss pregnancy possibility, testing and reliable contraception before starting, and contact the team promptly if pregnancy is suspected. The after-treatment instructions differ substantially: US guidance specifies effective contraception for patients who can become pregnant during treatment and for two weeks afterwards; European guidance requires at least six months afterwards. Obtain a clear end date from your team.

European information warns that hormonal contraception may be less effective. Discuss a suitable additional or alternative non-hormonal method. Neither vemurafenib label gives a fixed male-partner contraception period, so seek individual advice rather than borrowing an interval from another medicine.

With cobimetinib, US guidance requires female contraception for two weeks after its last dose; European guidance advises two effective methods during treatment and for at least three months afterwards. Follow all applicable partner precautions and the longer relevant interval. The European vemurafenib interval must not be shortened to cobimetinib's three months.

Do not breastfeed while taking treatment. US vemurafenib and cobimetinib guidance extends this for two weeks after the last dose of each medicine. European information does not give a fixed post-treatment restart interval; ask the team to confirm when it is appropriate. Effects of vemurafenib on human fertility are not well established. Discuss preservation options before treatment if future parenthood matters to you.

After a pause or when treatment finishes

Restart only after the team confirms the dose and any necessary blood tests or ECG. A severe allergy or skin reaction can make restarting unsafe. If receiving cobimetinib, obtain separate instructions for each medicine; a planned partner rest week and a toxicity-related interruption are different situations.

Continue skin surveillance and any other arranged cancer checks after stopping. New skin cancers can appear after treatment, so follow-up may continue for six months. Maintain contraception and breastfeeding restrictions for the applicable period. Return unwanted tablets safely and clarify the next scan, appointment and symptom-support plan.

Frequently asked questions