Talimogene laherparepvec is a novel oncolytic virus recently approved by the Therapeutic Goods Administration (TGA) as monotherapy for the treatment of unresectable melanoma after initial surgery.

Talimogene laherparepvec is a genetically modified herpes simplex virus type 1 (HSV-1). Two genes were deleted from HSV-1 to suppress viral replication within normal cells. An additional gene was inserted to allow viral production of human granulocyte macrophage colony-stimulating factor (GM-CSF). Following infection of a cancer cell, viral replication and GM-CSF production occurs until cell lysis. It is thought that release of GM-CSF leads to recruitment and activation of antigen presenting cells (APCs). APCs then process these tumour-derived antigens to promote a systemic effector T-cell response to cancer cells displaying these antigens.

A recent meta-analysis suggests that overall survival for patients treated with talimogene laherparepvec may be at least as good as that seen with ipilimumab and vemurafenib, although further studies are required. Talimogene laherparepvec is injected intralesionally in a cycle of three treatments. The time to lesion response is shortest for lesions that are directly injected, consistent with the initiation of a delayed systemic immune response.

Herpetic infection is a possible side effect as live, attenuated virus is used. Therefore, it must not be administered to patients at higher risk of complications from herpetic infection, including patients who are severely immunocompromised or during pregnancy.

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