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Talimogene Laherparepvec

Talimogene laherparepvec is a type of medication called an “oncolytic virus.” An oncolytic virus is a virus that makes copies of itself (replicates) in cancer cells. The virus spreads within the tumor. It does not damage normal cells.1 This medication is a type of immunotherapy.

Talimogene laherparepvec is used to treat melanoma in the skin and lymph nodes.2 It is only used on cancer that has recurred (come back) after initial surgery, if the lesions cannot be removed with additional surgery. Talimogene laherparepvec cannot be used to treat melanoma that has spread to your internal organs.

Talimogene laherparepvec is abbreviated T-VEC or called by the brand name Imlygic. T-VEC does not come in generic form.

How does T-VEC work?

T-VEC is a weakened version of the herpes simplex virus. Herpes simplex is the virus that causes cold sores. The virus has been genetically modified, so that it generally does not cause cold sore blisters.2,3 “Genetically modified” means that the virus’ DNA has been changed in a lab. The exact way that T-VEC works is unknown.2 It seems to affect the body in multiple ways that result in tumor destruction.

The modified herpes virus causes tumor cells to rupture (burst open) and die.2 This is how T-VEC kills cancer cells directly.4

The dying tumor cells release antigens.2 Antigens are molecules that trigger an immune response. Certain immune cells learn to recognize specific antigens and become active. In this way, T-VEC acts like a vaccine.4 It trains immune cells to recognize tumor antigens and fight cancer cells.

Finally, T-VEC–infected cells make a protein called GM-CSF.2 GM-CSF stands for granulocyte-macrophage colony-stimulating factor. GM-CSF creates a general immune response. It tells your body to make more white blood cells.5 White blood cells fight foreign and unhealthy cells, including abnormal cancer cells.

How is T-VEC given?

Your doctor will inject T-VEC directly into your melanoma tumors.2 Your doctor may not treat every tumor at each treatment session.

The second dose is given 3 weeks after the first dose. After that, you will be treated with T-VEC every 2 weeks.2 Treatment will continue as long as you have tumors, unless the melanoma worsens or side effects are unacceptable.

Before receiving T-VEC, read the Medication Guide that comes in the package.

What are the side effects of T-VEC?

Most side effects are mild or moderate, and they generally improve within 3 days. The most common side effects of T-VEC include:

  • Tiredness
  • Chills
  • Fever
  • Nausea and vomiting
  • Flu-like symptoms
  • Pain at the injection sites

Contact your doctor if you have signs of a possible herpes infection, including2:

  • Blister on the mouth or genitals that burns, tingles, or feels painful
  • Eye problems (pain, light sensitivity, discharge from the eyes, blurry vision)
  • Weakness in the arms or legs
  • Feeling very sleepy or drowsy
  • Mental confusion

Who should not take T-VEC?

T-VEC is a weakened but live version of the herpes virus. For this reason, you should not use T-VEC if you have a weakened immune system due to disease or medical treatment. Tell your doctor about medical conditions you have or had, especially2:

  • HIV infection or AIDS
  • Blood or bone marrow cancer
  • Autoimmune disease

Tell your doctor about medications you are taking, particularly:

  • Antiviral medications such as acyclovir to treat herpes.
  • Steroids or other medications that weaken your immune system.

T-VEC can harm an unborn baby. Women who are pregnant or plan to become pregnant should not use T-VEC. Use effective birth control during treatment with T-VEC. T-VEC has not been studied in breastfeeding women. Together with your doctor, decide whether to breastfeed or use T-VEC. Do not do both.

What precautions are needed during treatment with T-VEC?

Accidental exposure to T-VEC can lead to herpes infection. Proper care of the treatment sites is important to prevent the virus from spreading.2

Tell your doctor if you have close contact with someone who is pregnant or has a weak immune system. It is particularly important not to spread the virus to that person. A close contact is a household member, caregiver, sex partner, or someone sharing the same bed.2

To avoid spreading T-VEC:2

  • Avoid direct contact between your treatment sites, dressings, or body fluids and another person.
  • Keep treatment sites covered with air- and watertight dressings for at least 1 week after each treatment. If the site is still oozing or weeping after 1 week, keep it covered.
  • Wear gloves while changing your dressings.
  • Replace the dressing if it falls off.
  • Place used dressing and cleaning materials in a sealed bag. Throw it away in the garbage.
  • Do not touch or scratch the treatment sites.
Written by: Sarah O'Brien | Last reviewed: June 2019.
  1. Chiocca EA, Rabkin SD. Oncolytic viruses and their application to cancer immunotherapy. Cancer Immunol Res. 2014;2:295-300.
  2. Imlygic® [prescribing information]. Thousand Oaks, CA: Amgen Inc; March 2017.
  3. Kohlhapp FJ, Kaufman HL. Molecular pathways: Mechanism of action for talimogene laherparepvec, a new oncolytic virus immunotherapy. Clin Cancer Res. 2016;22:1048-1054.
  4. Breitbach CJ, Lichty BD, Bell JC. Oncolytic viruses: Therapeutics with an identity crisis. EBioMedicine. 2016;9:31-36.
  5. GM-CSF. Accessed April 17, 2017 at:
  6. Andtbacka RH, Kaufman HL, Collichio F, et al. Talimogene laherparepvec improves durable response rate in patients with advanced melanoma. J Clin Oncol. 2015;33:2780-2788.
  7. NCCN Clinical Practice Guidelines in Oncology. Melanoma. Version 1.2017. Published November 10, 2016.