Talimogene laherparepvec is a weakened herpes simplex virus that has been modified to replicate within tumour cells and produce human granulocyte macrophage colony-stimulating factor (GM-CSF). The immunotherapy causes death of tumour cells and the release of tumour-derived antigens, promoting the anti-tumour response.
In an open-label trial in 436 patients, talimogene laherparepvec was associated with significantly higher rates of durable (≥6 months) response than GM-CSF (16.3% [95% CI 12.1%–20.5%] vs 2.1% [95% CI 0%–4.5%]; odds ratio 8.9, p<0.001).
The overall response rate was also higher in patients treated with talimogene laherparepvec than in those given GM-CSF (26.4% [95% CI 21.4%–31.5%] vs 5.7% [95% CI 1.9%–9.5%]), as was median overall survival, at 23.3 months (95% CI 19.5–29.6 months) vs 18.9 months (95% CI 16.0–23.7 months) (hazard ratio 0.79, 95% CI 0.62–1.00; p=0.051).
Mild to moderate adverse effects
The most commonly reported adverse reactions to talimogene laherparepvec were fatigue, chills, pyrexia, nausea, flu-like illness and injection site pain. The majority (98%) of these effects reported in the pivotal study (n=292) were mild or moderate in severity. Cellulitis was the most common severe adverse event, occurring in 2.1% of patients.
Risk of herpes infection
Talimogene laherparepvec can cause herpes infection in patients and their contacts, particularly those who are immunocompromised. Patients must be informed of the risks and given a patient alert card. Healthcare professionals and close contacts should avoid direct contact with injected lesions or body fluids of treated patients during and for 30 days after treatment, and women of childbearing potential must be advised to use contraception during treatment.