Mektovi (Binimetinib)
MEK Inhibitor for BRAF-Mutant Melanoma and Non-Small Cell Lung Cancer
Quick Facts About Mektovi
Key Takeaways About Mektovi
- Always used with encorafenib: Mektovi is never taken alone – it must be used in combination with encorafenib (Braftovi) for effective dual blockade of the BRAF/MEK signalling pathway
- Requires BRAF mutation testing: Before starting treatment, a validated test must confirm a BRAF V600 mutation in the tumour tissue
- Regular monitoring essential: Heart function, eye examinations, blood pressure, liver enzymes, and skin checks are required throughout treatment
- Serious cardiac risk: Mektovi can decrease left ventricular ejection fraction – report any shortness of breath, swelling, or irregular heartbeat immediately
- Not for children: Mektovi has not been studied in patients under 18 years of age and is not recommended for this population
What Is Mektovi and What Is It Used For?
Mektovi (binimetinib) is a targeted anticancer medicine that inhibits MEK1 and MEK2 proteins. It is used in combination with encorafenib for the treatment of adults with unresectable or metastatic melanoma, or non-small cell lung cancer (NSCLC), that has a specific BRAF V600 mutation.
Mektovi contains the active substance binimetinib, which belongs to a class of medicines known as MEK inhibitors. MEK (mitogen-activated extracellular signal-regulated kinase) proteins are critical components of the RAS/RAF/MEK/ERK intracellular signalling pathway, also known as the MAPK pathway. This pathway plays a fundamental role in regulating cell growth, division, and survival. In cancers with BRAF mutations, this pathway becomes overactive, driving uncontrolled cancer cell proliferation.
The BRAF gene provides instructions for making a protein called B-Raf, which is part of this same signalling cascade. Mutations in the BRAF gene – most commonly the V600E and V600K mutations – produce an abnormally active B-Raf protein that continuously stimulates cell growth. Approximately 40–60% of cutaneous melanomas and 1–3% of non-small cell lung cancers harbour BRAF V600 mutations, making these cancers particularly amenable to targeted therapy with BRAF and MEK inhibitors.
Mektovi targets MEK, which sits directly downstream of BRAF in the signalling cascade. When used in combination with encorafenib (a BRAF inhibitor, marketed as Braftovi), the dual blockade provides more complete inhibition of the MAPK pathway than either agent alone. This combination approach has two major advantages: it produces more robust tumour shrinkage and it significantly delays the development of acquired resistance, which is a common limitation of single-agent BRAF inhibitor therapy.
The European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA) have approved the binimetinib plus encorafenib combination for the treatment of adult patients with unresectable or metastatic melanoma with a BRAF V600 mutation. The EMA has additionally approved this combination for BRAF V600E-mutant non-small cell lung cancer that has spread to other parts of the body or cannot be removed surgically. Before starting treatment, a validated and approved test must confirm the presence of a BRAF V600 mutation in the tumour.
Think of the MAPK signalling pathway as a relay race inside cancer cells. BRAF passes the signal to MEK, which then passes it further down the chain, telling the cell to grow and divide. Encorafenib blocks the mutant BRAF protein, while Mektovi blocks MEK. By targeting two consecutive points in this relay, the combination therapy provides a more complete blockade of the cancer growth signal. Clinical trials (COLUMBUS study for melanoma, PHAROS study for NSCLC) have demonstrated significant improvements in progression-free survival and overall survival with this dual-targeted approach.
What Should You Know Before Taking Mektovi?
Before starting Mektovi, your doctor will test your tumour for a BRAF mutation, assess your heart function, check your eyes, and review all your current medications. You must inform your doctor about any pre-existing heart, eye, muscle, liver, lung, or bleeding problems.
Since Mektovi is always used in combination with encorafenib, you should carefully read the information for both medications. Your oncologist will perform a thorough assessment before beginning treatment, including blood tests, cardiac evaluation, and ophthalmological examination. It is essential that you provide a complete medical history, including all medications you are currently taking.
Contraindications
You should not take Mektovi if:
- You are allergic to binimetinib or any of the other ingredients in this medicine, including lactose monohydrate, microcrystalline cellulose, colloidal anhydrous silica, croscarmellose sodium, or magnesium stearate
Your oncologist will also consider whether you have any conditions that may make treatment with Mektovi inadvisable, including a history of retinal vein occlusion (a blood clot in the vein that drains blood from the eye). Mektovi is not recommended in patients who have previously experienced retinal vein occlusion.
Warnings and Precautions
Talk to your doctor, pharmacist, or nurse before taking Mektovi, and tell them about all your medical problems, especially if you have any of the following:
- Heart problems: Mektovi can impair heart function or worsen existing cardiac conditions. Your doctor will check your heart function (left ventricular ejection fraction) by echocardiogram or MUGA scan before treatment and at regular intervals during therapy. Contact your doctor immediately if you feel dizzy, tired, lightheaded, short of breath, or notice pounding, racing, or irregular heartbeats, or swelling in your legs.
- Bleeding problems: Mektovi can cause serious bleeding. If you are taking any blood-thinning medication or have a bleeding disorder, inform your doctor. Seek immediate medical attention if you cough up blood, vomit blood or material resembling coffee grounds, pass red or black tarry stools, have blood in your urine, experience abdominal pain, or have unusual vaginal bleeding.
- Eye problems: Mektovi can cause serious eye complications, including fluid leakage under the retina (serous retinal detachment) and retinal vein occlusion. If you have glaucoma or elevated intraocular pressure, inform your doctor. Your doctor will perform eye examinations before and during treatment. Seek immediate medical attention if you experience blurred vision, vision loss, colour changes in your vision, or seeing halos around objects.
- Muscle problems: Mektovi can cause breakdown of skeletal muscle tissue (rhabdomyolysis), which can lead to kidney damage. Your doctor will take blood tests to check for muscle problems before and during treatment. Drink plenty of fluids during treatment. Report any muscle pain, cramping, stiffness, spasms, or dark-coloured urine immediately.
- High blood pressure (hypertension): Mektovi can raise blood pressure. Your blood pressure will be monitored before and during treatment. Report severe headaches, dizziness, lightheadedness, or abnormally high blood pressure readings.
- Blood clots (venous thromboembolism): Mektovi can cause blood clots in the veins of your arms or legs, which can travel to the lungs and be life-threatening (pulmonary embolism). Seek immediate medical attention if you experience chest pain, sudden shortness of breath, difficulty breathing, leg pain with or without swelling, or a cold, pale limb.
- Lung or breathing problems: Mektovi can cause inflammation of the lungs (pneumonitis or interstitial lung disease). Signs include cough, shortness of breath, or fatigue. Your doctor may pause or permanently stop treatment if this occurs.
- Liver problems: Mektovi can cause abnormal blood tests related to liver function (elevated liver enzymes). Your doctor will take blood tests to monitor your liver before and during treatment.
When Mektovi is taken together with encorafenib, other types of skin cancer may develop, including cutaneous squamous cell carcinoma. Your doctor will examine your skin before starting treatment, every two months during treatment, and for up to 6 months after stopping these medicines. Report any new skin changes immediately, such as a new wart, a sore or reddish bump that bleeds or does not heal, or a mole that grows or changes colour. Additional examinations of the head, neck, mouth, lymph nodes, and genital/anal area may also be recommended.
Tumour Lysis Syndrome
Mektovi can cause rapid breakdown of cancer cells, which in some patients can be life-threatening. This is known as tumour lysis syndrome (TLS). Symptoms may include nausea, shortness of breath, irregular heartbeat, muscle cramps, seizures, cloudy urine, decreased urine output, and fatigue. Contact your doctor immediately if you experience any of these symptoms, as they may indicate changes in kidney function caused by the release of breakdown products from dying cancer cells.
Pregnancy and Breastfeeding
Pregnancy: Mektovi is not recommended during pregnancy. Based on its mechanism of action, binimetinib may cause permanent damage or birth defects in an unborn baby. If you are pregnant, think you may be pregnant, or are planning to become pregnant, talk to your doctor before using this medicine.
If you are a woman of childbearing potential, you must use reliable contraception while taking Mektovi and for at least one month after the last dose. Contact your doctor immediately if you become pregnant during treatment. Your doctor will discuss the risks and potential benefits of continuing treatment in your specific situation.
Breastfeeding: Mektovi is not recommended during breastfeeding. It is not known whether binimetinib passes into breast milk. If you are breastfeeding or planning to breastfeed, consult your doctor before taking this medicine. Your doctor will help you decide whether to discontinue breastfeeding or discontinue Mektovi therapy, taking into account the benefit of breastfeeding for your child and the benefit of therapy for you.
Children and Adolescents
Mektovi is not recommended for children and adolescents under 18 years of age. This medicine has not been studied in this age group, and its safety and effectiveness in paediatric patients have not been established.
Driving and Operating Machinery
Mektovi may affect your ability to drive or use machines. Avoid driving or operating machinery if you experience vision problems or any other side effects that could impair your ability to do so safely. Talk to your doctor if you are uncertain about whether it is safe for you to drive.
Lactose Content
Mektovi contains lactose. If you have been told by your doctor that you have an intolerance to some sugars, talk to your doctor before taking this medicine. This medicine contains less than 1 mmol sodium (23 mg) per tablet, meaning it is essentially sodium-free.
How Does Mektovi Interact with Other Drugs?
Mektovi can interact with several medications, including certain antibiotics, antiepileptics, HIV treatments, cancer drugs, antidepressants, cholesterol medications, and herbal supplements such as St. John's Wort. Always inform your doctor about all medicines you are taking.
Binimetinib is primarily metabolised through glucuronidation by UGT1A1, and to a lesser extent by CYP1A2 and CYP2C19. Some medicines can affect how Mektovi works, or Mektovi may affect how other medicines work. It is essential to inform your doctor, pharmacist, or nurse about all medicines you are taking, have recently taken, or might take, including over-the-counter medicines and herbal remedies.
Major Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Rifampicin | Antibiotic (TB treatment) | Strong enzyme inducer that may significantly reduce binimetinib effectiveness | Avoid combination; discuss alternatives with your doctor |
| Phenobarbital / Phenytoin / Carbamazepine | Antiepileptics | Enzyme inducers that may reduce binimetinib blood levels | Avoid if possible; your doctor may need to adjust dosing |
| St. John’s Wort (Hypericum perforatum) | Herbal supplement | Strong enzyme inducer that may reduce effectiveness of Mektovi | Do not take St. John's Wort during Mektovi treatment |
| Sorafenib | Cancer treatment (multikinase inhibitor) | May alter binimetinib metabolism and increase toxicity risk | Combination not recommended; discuss with your oncologist |
Moderate Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Ciprofloxacin | Antibiotic (fluoroquinolone) | CYP1A2 inhibitor that may increase binimetinib blood levels | Monitor for increased side effects; dose adjustment may be needed |
| Indinavir / Atazanavir | HIV protease inhibitors | May affect binimetinib metabolism | Use with caution; monitor for toxicity |
| Duloxetine | Antidepressant (SNRI) | CYP1A2 inhibitor that may alter binimetinib levels | Inform your doctor; monitoring may be needed |
| Pravastatin | Cholesterol-lowering (statin) | May increase risk of muscle toxicity when combined with MEK inhibitors | Monitor creatine kinase levels closely |
| Theophylline | Respiratory medication | CYP1A2 substrate; binimetinib may affect theophylline levels | Monitor theophylline levels; dose adjustment may be required |
What Is the Correct Dosage of Mektovi?
The recommended dose of Mektovi is 45 mg (three 15 mg tablets or one 45 mg tablet) taken twice daily, approximately 12 hours apart, for a total daily dose of 90 mg. Mektovi is always taken in combination with encorafenib.
Always take this medicine exactly as your doctor or pharmacist has told you. Do not change the dose or stop treatment without consulting your doctor first. Your oncologist will determine how long you should continue treatment based on your response and any side effects you experience.
Adults
Standard Adult Dose
45 mg twice daily (total daily dose: 90 mg)
- Take three 15 mg tablets or one 45 mg tablet, twice daily
- Doses should be approximately 12 hours apart
- Swallow tablets whole with water
- Can be taken with or without food
- Always taken together with encorafenib as prescribed by your oncologist
If You Cannot Swallow Tablets Whole
The 15 mg tablets may be dissolved in a small glass (approximately 10 ml, about 2 teaspoons) of water, orange juice, or apple juice. Drink immediately. Rinse the glass with an additional 10 ml of the same liquid and drink that as well. If the mixture is not used within 30 minutes, discard it and prepare a new one.
Dose Modifications
If you experience serious side effects (such as heart problems, eye problems, or skin changes), your doctor may reduce the dose, temporarily pause treatment, or permanently discontinue it. Dose reductions typically follow a stepwise approach determined by your oncologist.
Children
Mektovi is not recommended for children and adolescents under 18 years of age. This medicine has not been studied in paediatric patients.
Elderly Patients
No specific dose adjustment is required for elderly patients. However, older patients may be more susceptible to certain side effects, and closer monitoring is advisable. Your oncologist will assess your individual situation and adjust treatment accordingly.
Missed Dose
If you miss a dose of Mektovi, take it as soon as you remember. However, if the missed dose was due more than 6 hours ago, skip it and take the next dose at the usual time. Do not take a double dose to make up for a missed dose.
If You Vomit After Taking Mektovi
If you vomit after taking Mektovi, do not take an additional dose. Take the next dose at your regular scheduled time.
Overdose
If you take more Mektovi than prescribed, contact your doctor, pharmacist, or nurse immediately. If possible, show them the package leaflet and the tablet packaging. Overdose may intensify the known side effects of binimetinib, including cardiac, ocular, and musculoskeletal toxicity. There is no specific antidote for binimetinib overdose; treatment is supportive and symptomatic.
It is important to continue taking Mektovi for as long as your doctor prescribes. Do not stop taking this medicine unless your doctor tells you to do so. Stopping treatment prematurely may allow the cancer to progress. If you have any concerns about your treatment, discuss them with your oncologist.
What Are the Side Effects of Mektovi?
Like all medicines, Mektovi can cause side effects, although not everyone gets them. Serious side effects include decreased heart function, blood clots, retinal detachment, rhabdomyolysis, severe bleeding, and tumour lysis syndrome. Contact your doctor immediately if you experience any serious symptoms.
The following side effects have been reported when Mektovi is taken in combination with encorafenib. Side effects are categorised by how frequently they occur. It is important to be aware of both common and serious side effects so that you can report any new symptoms to your oncologist promptly.
Serious Side Effects
Contact your doctor immediately if you experience any of the following:
- Heart problems (decreased LVEF): Dizziness, fatigue, unsteadiness, shortness of breath, pounding, racing, or irregular heartbeat, swollen legs
- Blood clots (VTE/PE): Chest pain, sudden shortness of breath, difficulty breathing, leg pain with or without swelling, cold or pale limb
- Eye problems (retinal detachment): Blurred vision, vision loss, colour changes in vision, halos around objects, eye pain, swelling, or redness
- Muscle breakdown (rhabdomyolysis): Muscle pain, cramping, stiffness, spasms, or dark-coloured urine
- Severe bleeding: Coughing up blood, vomiting blood or coffee ground-like material, black tarry stools, blood in urine, unusual vaginal bleeding
- Tumour lysis syndrome: Nausea, shortness of breath, irregular heartbeat, muscle cramps, seizures, cloudy urine, decreased urine output, fatigue
Side Effects by Frequency
The following side effects have been reported when Mektovi is used together with encorafenib:
Very Common
- Anaemia (decreased red blood cell count)
- Peripheral neuropathy (nerve problems causing pain, numbness, or tingling in hands and feet)
- Headache and dizziness
- Bleeding at various sites
- Vision impairment
- Abdominal pain, diarrhoea, nausea, vomiting, constipation
- Itching, dry skin, hair loss or thinning (alopecia)
- Various types of skin rash
- Thickening of the outer skin layers
- Joint pain (arthralgia), muscle disorders, back pain, pain in extremities
- Fever, peripheral oedema (swelling of hands/feet), fatigue
- Abnormal liver function tests
- Elevated creatine kinase (indicating heart/muscle damage)
Common
- Skin tumours such as skin papilloma
- Allergic reaction (may include facial swelling and difficulty breathing)
- Altered taste
- Eye inflammation (uveitis)
- Inflammation of the colon (colitis)
- Redness or cracked skin
- Inflammation of the fat layer under the skin (tender lumps)
- Acne-like rash (acneiform dermatitis)
- Redness, peeling skin or blisters on hands and feet (hand-foot syndrome)
- Kidney failure and elevated creatinine
- Abnormal liver blood tests (elevated alkaline phosphatase)
- Abnormal pancreatic blood tests (elevated amylase, lipase)
- Increased skin sensitivity to sunlight
Uncommon
- Certain types of skin cancer such as basal cell carcinoma
- Weakness and paralysis of facial muscles
- Inflammation of the pancreas (pancreatitis) causing severe abdominal pain
It is important to report suspected side effects after the medicine has been authorised. This helps to continuously monitor the benefit-risk balance of the medicine. Healthcare professionals and patients are encouraged to report any suspected adverse reactions to their national regulatory authority.
How Should You Store Mektovi?
Store Mektovi out of the sight and reach of children. No special storage conditions are required. Do not use this medicine after the expiry date stated on the blister and carton.
Mektovi does not require any special storage conditions – it can be kept at room temperature. Keep the tablets in the original blister pack to protect them from moisture and light until you are ready to take them. Check the expiry date printed on the blister and the outer carton before each use. The expiry date refers to the last day of the stated month.
Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines you no longer use. These measures help to protect the environment and ensure safe handling of anticancer medications.
What Does Mektovi Contain?
Each Mektovi 15 mg film-coated tablet contains 15 mg of binimetinib as the active substance. The tablets also contain lactose monohydrate and various inactive excipients.
Active Substance
The active substance is binimetinib. Each Mektovi 15 mg film-coated tablet contains 15 mg of binimetinib.
Inactive Ingredients (Excipients)
The other ingredients are:
- Tablet core: Lactose monohydrate, microcrystalline cellulose (E460i), colloidal anhydrous silica (E551), croscarmellose sodium (E468), and magnesium stearate (E470b)
- Film coating (15 mg tablets): Poly(vinyl alcohol) (E1203), macrogol 3350 (E1521), titanium dioxide (E171), talc (E533b), yellow iron oxide (E172), and black iron oxide (E172)
Appearance and Pack Sizes
Mektovi 15 mg film-coated tablets are yellow to dark yellow, biconvex, oval, unscored tablets with "A" debossed on one side and "15" on the other. They are available in packs of 84 tablets (7 blisters of 12 tablets each) or 168 tablets (14 blisters of 12 tablets each).
Not all pack sizes may be marketed in all countries. Mektovi is manufactured by Pierre Fabre Medicament Production in Gien, France, and the marketing authorisation is held by Pierre Fabre Medicament, Lavaur, France.
Frequently Asked Questions About Mektovi
Mektovi (binimetinib) is used in combination with encorafenib (Braftovi) for the treatment of adults with unresectable or metastatic melanoma and non-small cell lung cancer (NSCLC) that has a BRAF V600 mutation. The BRAF mutation must be confirmed by a validated test before treatment begins. Mektovi is never used as a single agent – it must always be taken together with encorafenib for optimal effectiveness.
The most common side effects (affecting more than 1 in 10 patients) include anaemia, peripheral neuropathy (nerve pain or tingling in hands and feet), headache, dizziness, bleeding, vision problems, gastrointestinal issues (abdominal pain, diarrhoea, nausea, vomiting, constipation), skin reactions (rash, itching, dry skin, hair loss), musculoskeletal problems (joint and muscle pain, back pain), fever, fatigue, swelling, and abnormal blood test results (liver enzymes, creatine kinase).
Mektovi (a MEK inhibitor) is always used together with encorafenib (a BRAF inhibitor) because targeting both consecutive proteins in the MAPK signalling pathway provides more effective cancer growth inhibition than targeting either alone. This dual blockade produces greater tumour shrinkage and significantly delays the development of treatment resistance, which commonly occurs when BRAF inhibitors are used alone. The combination was specifically studied and approved as a dual-agent regimen in the COLUMBUS and PHAROS clinical trials.
Regular monitoring during Mektovi treatment includes: cardiac assessments (echocardiogram or MUGA scan to check left ventricular ejection fraction), ophthalmological examinations (eye exams to check for retinal problems), blood pressure monitoring, blood tests for liver function, creatine kinase (muscle marker), and kidney function, and skin examinations every two months and for up to 6 months after stopping treatment. CT scans of the head, neck, and chest may also be performed at regular intervals. Patients should report any new symptoms to their oncologist promptly.
Mektovi is not recommended during pregnancy. Based on its mechanism of action, it may cause permanent damage or birth defects. Women of childbearing potential must use effective contraception during treatment and for at least one month after the last dose. If you become pregnant while taking Mektovi, contact your doctor immediately. Mektovi is also not recommended during breastfeeding, as it is unknown whether it passes into breast milk.
If you miss a dose of Mektovi, take it as soon as you remember. However, if the missed dose was due more than 6 hours ago, skip it and take the next dose at the regular scheduled time. Do not take a double dose to compensate for a missed dose. If you vomit after taking a dose, do not take an additional dose – simply take the next dose at the usual time.
References
- European Medicines Agency (EMA). Mektovi (binimetinib) – Summary of Product Characteristics. Updated September 2025. Available at: EMA – Mektovi EPAR
- Dummer R, Ascierto PA, Gogas HJ, et al. Encorafenib plus binimetinib versus vemurafenib or encorafenib in patients with BRAF-mutant melanoma (COLUMBUS): a multicentre, open-label, randomised phase 3 trial. Lancet Oncol. 2018;19(5):603–615. doi:10.1016/S1470-2045(18)30142-6
- Dummer R, Flaherty KT, Robert C, et al. COLUMBUS 5-Year Update: A Randomized, Open-Label, Phase III Trial of Encorafenib Plus Binimetinib Versus Vemurafenib or Encorafenib in Patients With BRAF V600-Mutant Melanoma. J Clin Oncol. 2022;40(36):4178–4188. doi:10.1200/JCO.21.02659
- Riely GJ, Smit EF, Ahn MJ, et al. Phase II, Open-Label Study of Encorafenib Plus Binimetinib in Patients With BRAF V600-Mutant Metastatic Non-Small-Cell Lung Cancer (PHAROS). J Clin Oncol. 2023;41(21):3700–3711. doi:10.1200/JCO.23.00332
- National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Melanoma: Cutaneous. Version 2.2025.
- European Society for Medical Oncology (ESMO). Cutaneous melanoma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2024;35(2):137–165.
- U.S. Food and Drug Administration (FDA). Mektovi (binimetinib) Prescribing Information. Updated 2024.
- World Health Organization (WHO). WHO Model List of Essential Medicines. 23rd edition, 2023.
Editorial Team
This article has been written and medically reviewed by the iMedic Medical Editorial Team, which consists of licensed specialist physicians in oncology, clinical pharmacology, and dermatology. Our team follows international guidelines from ESMO, NCCN, EMA, and WHO, and adheres to the GRADE evidence framework for assessing the quality of medical evidence.
iMedic Medical Editorial Team – Specialists in Oncology and Clinical Pharmacology
iMedic Medical Review Board – Independent expert panel reviewing content according to international guidelines
Level 1A – Based on systematic reviews, randomised controlled trials (COLUMBUS, PHAROS), and international oncology guidelines
No commercial funding. No pharmaceutical company sponsorship. Independent medical editorial content with no conflicts of interest.