Cotellic (cobimetinib) is a targeted cancer medicine used to treat unresectable or metastatic melanoma (skin cancer that has spread) that carries a specific genetic mutation in the BRAF gene (V600E or V600K). It belongs to a class of medicines called MEK inhibitors.

Cotellic is always used in combination with a BRAF inhibitor called vemurafenib (Zelboraf). The two medicines work together to more effectively block the signalling pathways that drive melanoma cell growth.

How it works:

The BRAF mutation found in many melanomas activates a chain of signalling proteins that promote cancer cell growth. BRAF feeds into a protein called MEK, which in turn activates further growth signals. Cotellic blocks MEK, while vemurafenib blocks BRAF. Targeting both points in the same pathway simultaneously is more effective than blocking either one alone, and reduces the chance of the cancer developing resistance.

Your dose:

The usual dose is 60mg (three 20mg tablets) taken once daily for 21 days, followed by 7 days off. This 28-day cycle is then repeated. Cotellic is always taken alongside vemurafenib. Your doctor will confirm the exact schedule.

How to take it:

• Take Cotellic at the same time each day during your 21 days on treatment
• It can be taken with or without food
• Swallow the tablets whole

Before you start:

• Your tumour will be tested to confirm a BRAF V600E or V600K mutation before starting treatment
• Tell your doctor about all other medicines, vitamins, and supplements you take
• Let your doctor know if you have any history of heart, liver, eye, or muscle problems
• Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding. Effective contraception is required during and after treatment

Ongoing check-ups:

You will need regular echocardiograms (heart ultrasounds), liver function tests, skin checks, eye assessments, and blood tests during treatment. Attend all appointments.

• If you remember on the same day: take the missed dose as soon as possible
• If you remember the next day: skip the missed dose and continue your usual schedule
• Never take a double dose

If you think you have taken more than prescribed, call 000 or go to your nearest emergency department straight away.

• Store below 30°C
• Keep in the original packaging, away from moisture and light
• Keep out of reach of children and pets

Side effects are common with Cotellic, particularly when used in combination with vemurafenib.

• Diarrhoea: Very common. Stay well hydrated and tell your doctor if it becomes severe or persistent
• Nausea and vomiting: Common, especially early in treatment. Taking Cotellic with food may help
• Fatigue: Very common. Rest as needed and let your care team know if it significantly affects your daily life
• Fever: Some people develop a fever during treatment. Tell your doctor if this occurs
• Liver changes: Elevated liver enzymes are common. Regular blood tests monitor for this
• Heart function changes: Cobimetinib can reduce the heart's pumping efficiency. Echocardiograms are done regularly to check this
• Eye problems: Some people develop sensitivity to light or blurred vision. Tell your doctor immediately if you notice any visual changes
• Muscle problems (rhabdomyolysis): Rarely, severe muscle breakdown can occur. Report significant muscle pain or weakness to your doctor
• Skin rash and photosensitivity: Use sunscreen and protective clothing

Contact your doctor or pharmacist if any side effect concerns you.

Tell your doctor and pharmacist everything you are taking.

Key interactions include:

• Strong CYP3A4 inhibitors or inducers: Can significantly alter cobimetinib blood levels. Your doctor will check for these before you start
• Medicines that affect the QT interval or heart function: Extra caution is needed given Cotellic's effects on the heart

Never start, stop, or change any medicine without speaking to your doctor first.

Why do I take Cotellic for 21 days and then have 7 days off?

This 21-days-on, 7-days-off schedule was found in clinical studies to be the most effective dosing pattern while allowing the body some recovery time from side effects. The 7-day break does not mean the treatment stops working during that period, as the medicine remains in your system.

Why do I need both Cotellic and vemurafenib?

Using a MEK inhibitor (Cotellic) alongside a BRAF inhibitor (vemurafenib) targets the same cancer pathway at two different points. This dual blockade is significantly more effective than either medicine alone and also reduces the chance of the melanoma developing resistance to treatment.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.