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Talimogene laherparepvec (or T-VEC) is a genetically modified form of the cold sore virus that is designed to infect and kill melanoma cells. T-VEC isn’t used very commonly, as there may be other treatments, such as surgery or immunotherapy, that could be more effective depending on the stage and type of melanoma. T-VEC has to be injected directly into melanomas, and so is only suitable and most effective for people who have lumps that can be felt (such as skin lumps or lymph nodes) and the melanomas cannot have spread to any internal organs. The virus helps to stimulate the bodys own immune system to potentially try to kill and destroy melanoma cells.

This video explains T-VEC and how it works:

 Understanding T-VEC

Dr Elaine Vickers explains how T-VEC works, and why it is used in the treatment of melanoma skin cancer.

The treatment will be given in a hospital or clinic. After the first injection, the second dose is given 3 weeks later, then additional doses will be given every two weeks for at least 6 months, until there are no remaining injectable tumours to treat or other treatment is required. You should keep the area where the injection was given covered for 2 days after treatment, and throw away the dressing in a special bin provided by the hospital.

T-VEC is not offered as a treatment in all hospitals that treat melanoma and therefore you may have to travel to another hospital where they have been trained to administer the treatment.

Possible side effects

All cancer therapies are associated with some side effects that may impact on daily life to a lesser or greater extent. Early treatment of side effects can help manage them better.  

Flu-like symptoms

It’s very common to get flu-like symptoms after having T-VEC. Symptoms include a high temperature, feeling tired and weak, headaches, chills (shivering), muscle aches. These symptoms usually get better after a few days. Your medical team will advise you what to do if you experience these symptoms.

Being sick (vomiting) or feeling sick (nausea)

If you feel sick or are being sick while on treatment, medicines can be given to help control this. It is important if you are being sick to drink lots of fluids to stop you from becoming dehydrated.

Swollen hands and feet

Swelling of the hands and legs can occur due to a build-up of fluid (oedema).

Pain at the injection site

Some people can experience pain, redness, bleeding, swelling, inflammation, discharge, and warmth at the injection site.

Pain in different parts of the body (muscles, joints, arms and legs)

These pains should only be temporary, and painkillers can be used to control this if needed.

Some other common side effects of T-VEC may be:

Tiredness and weakness, cough, headaches or skin rashes


If you have any worries or concerns, please contact your medical team or call our:

Melanoma Helpline on 0808 801 0777

There may be clinical trials looking at new treatments to treat your type of melanoma. 

For more information on clinical trials see the Melanoma TrialFinder

Questions you may have

  • What are my treatment options?
  • Where is the nearest hospital that offers this treatment?
  • How frequently will I have treatment?
  • What are the potential side-effects and what should I do if I experience anything unusual?
  • What clinical trials are potential options for me?
  • When will I know if the T-VEC treatment has been successful?

Electronic Medicines Compendium, https://www.medicines.org.uk/emc/files/pil.5117.pdf [Accessed 2023]

Cancer Research UK, Talimogene laherparepvec (T-VEC), https://www.cancerresearchuk.org/about-cancer/treatment/drugs/talimogene-laherparepvec [Accessed 2023]