Oncolytic HSV-1 (genetically modified) Pregnancy: Contraindicated in pregnant patients (US §4.2). No adequate and well-controlled studies in pregnant women; women of childbearing potential should use an effective method of contraception during treatment. If a patient becomes pregnant, apprise her of the potential hazards to the fetus and neonate (§8.1).

Talimogene laherparepvec (Specialist drug)

Brand names: Imlygic

Talimogene laherparepvec is an oncolytic immunotherapy (a modified herpes simplex virus type 1) injected directly into melanoma lesions in selected patients with unresectable, locally or regionally advanced disease.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Initial dose: up to 4 mL at a concentration of 10^6 (1 million) plaque-forming units (PFU) per mL. All subsequent doses: up to 4 mL at a concentration of 10^8 (100 million) PFU per mL.

Route: Intralesional injection into cutaneous, subcutaneous and/or nodal lesions that are visible, palpable or detectable by ultrasound guidance. For intralesional injection only — do NOT administer intravenously.

Frequency: Initial dose, then second dose 3 weeks after initial treatment, then all subsequent treatments (including reinitiation) 2 weeks after the previous treatment.

Max: Total injection volume must not exceed 4 mL per treatment visit (all injected lesions combined).

Per-lesion injection volume by lesion size (longest dimension): >5 cm up to 4 mL; >2.5-5 cm up to 2 mL; >1.5-2.5 cm up to 1 mL; >0.5-1.5 cm up to 0.5 mL; <=0.5 cm up to 0.1 mL. Clustered lesions are injected as a single lesion. Prioritise the largest lesion(s) at the initial visit; at later visits inject any new lesions first, then remaining lesions by size until the maximum volume is reached. Continue treatment for at least 6 months unless other treatment is required or there are no injectable lesions; reinitiate if new unresectable cutaneous, subcutaneous or nodal lesions appear after a complete response. Paediatric: safety and effectiveness have not been established in paediatric patients (US §8.4). Geriatric: no overall differences in safety or efficacy vs younger patients (§8.5). Handling: live attenuated herpes simplex virus — healthcare providers who are immunocompromised or pregnant should not prepare or administer it or contact injection sites, dressings or body fluids of treated patients; wear PPE; dispose of contaminated materials as biohazardous waste. Source note: no UK SPC (eMC) record was fetched — regimen taken from the US prescribing information and the fetched §2 text was truncated at the source-fetch limit, so preparation/administration detail beyond thawing is incomplete.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Immunocompromised patients — may cause life-threatening disseminated herpetic infection; includes primary or acquired immunodeficient states, leukaemia, lymphoma, AIDS or other clinical manifestations of HIV infection, and those on immunosuppressive therapy (§4.1)
Pregnant patients (§4.2)

Side effects

Fatigue
Chills
Pyrexia
Nausea
Influenza-like illness
Injection site pain

Interactions

Sensitive to aciclovir — aciclovir or other antiherpetic viral agents may interfere with the effectiveness of talimogene laherparepvec (US label §7)
No drug interaction studies have been conducted (US label §7)

Clinical monograph

How it works

The attenuated virus replicates selectively within tumour cells, causing them to lyse, and it expresses GM-CSF to promote a local and systemic anti-tumour immune response.

Prescribing in practice

Because it is a live attenuated herpes virus, it must not be given to severely immunocompromised patients, and healthcare staff and close contacts who are immunocompromised or pregnant should avoid contact with injection sites and dressings to prevent accidental transmission.
Herpetic infection can occur in patients and theoretically in contacts; aciclovir or other antivirals can treat herpetic infection but may reduce the medicine's effectiveness.
Administered by intralesional injection by trained specialists with standard precautions for handling and disposal.

Monitoring

Monitor injection sites and lesions for response and for signs of herpetic or other infection, including cellulitis.

Counselling the patient

Keep injection sites covered as instructed and avoid touching or scratching them.
Avoid close contact with people who are pregnant, infants, or those with weakened immune systems while sites are healing.
Report cold-sore-like symptoms, fever, or spreading skin redness.

Evidence & guidelines

Approval was based on a randomised trial demonstrating improved durable response rate in advanced melanoma.

Reference: NICE TA410; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways