Generic Name

tirbanibulin

Mechanism

• Src kinase inhibition: Tirbanibulin obstructs SH2 domain‑mediated Src activation, blocking downstream signaling required for AK cell survival.
• Microtubule destabilization: It binds to the *β‑tubulin* subunit, preventing polymerization and disrupting mitotic spindle formation.
• Induction of apoptosis: By arresting the G2/M phase, the drug triggers caspase‑dependent cell death in dysplastic keratinocytes while sparing normal epidermis.

Pharmacokinetics

• Absorption: Minimal systemic uptake; following topical application of a single 1 mg (1 % cream) dose, plasma concentrations are below the limit of quantitation.
• Distribution: Predominantly confined to the superficial epidermis; negligible blood‑brain barrier penetration.
• Metabolism: Local ester hydrolysis and conjugation in keratinocytes; not significantly hepatically metabolized.
• Elimination: Excreted mainly via the skin and minor fecal routes; half‑life >24 h in the epidermis.

Indications

• Primary: Treatment of clinically visible actinic keratosis lesions on the face and anterior neck of adults.
• Off‑label (emerging evidence): Small, superficial basal‑cell carcinoma and Bowen’s disease, though not FDA‑approved.

Contraindications

• Contraindications
• Known hypersensitivity to tirbanibulin or any cream excipient.
• Active, inflammatory, or eroded skin disorders (e.g., eczema) that may increase systemic absorption.
• Warnings
• Non‑compliance: Failure to apply exactly 5 consecutive daily doses may reduce efficacy.
• Concurrent phototherapy: Avoid ultraviolet exposure during treatment.
• Pregnancy/Lactation: Limited data; use only if benefits outweigh risks.

Dosing

• Dose: 1 % vitegel‑based cream (1 mg/5 mL).
• Application: Apply a thin layer to the AK‑affected area once daily for 5 consecutive days.
• Technique
• Cleanse and dry the skin first.
• Avoid occlusive dressing to lessen irritation.
• Pat gently; do not rub vigorously.
• Post‑application: Wash hands thoroughly.

Adverse Effects

• Common (≥5 %)
• erythema, pruritus, dryness, burning sensation.
• mild scaling or desquamation.
• Serious (≤1 %)
• severe dermatitis or contact allergic reaction.
• rarely, ophthalmic irritation if applied near eyes.

Monitoring

• Routine: No laboratory monitoring required due to negligible systemic exposure.
• Clinical: Assess lesion resolution 2–4 weeks after completing therapy.
• Safety: Watch for signs of allergic contact dermatitis; discontinue if severe.

Clinical Pearls

• Target the exact lesion: Use the half‑coupled occlusion technique—taping the edges of the cream to the skin—reduces fracturing of the drug into surrounding healthy tissue, limiting irritation.
• Optimal timing: Apply in the evening; decreased daylight exposure lowers erythema.
• Re‑application: If lesions recur after 3–6 months, the same 5‑day cycle remains effective; reschedule extra‑treatment when lesion development exceeds 50 %.
• Drug‑interaction caution: No systemic interactions, but avoid concomitant topical agents that can strip the epidermis (e.g., high‑dose exfoliants) on the same day.
• Patient education: Reassure that resolving dysplastic cells may cause temporary redness/flaking; this indicates active therapeutic effect.
• Compliance tip: A simple 5‑day “calendar” reminder improves adherence far better than longer regimens used for other topical chemotherapies.

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• *For detailed prescribing information, refer to the FDA package insert and the latest dermatology guidelines.*