Tirbanibulin Ointment 1% as a Novel Treatment for Actinic Keratosis: Phase 1 and 2 Results

Background: Current field-directed treatments of actinic keratosis (AK), a pre-malignant condition, are often limited by severe local reactions and/or complex treatment. Tirbanibulin, a novel potent anti-proliferative synthetic agent that inhibits tubulin polymerization and Src kinase signalling, is being developed as a convenient, safe, and effective field treatment of actinic keratosis. Hypothesis: A short course of tirbanibulin ointment 1% safely reduces AK lesions. Methods: In the Phase 1 study, 4 treatment cohorts with forearm lesions received tirbanibulin ointment 1% over 25 or 100 cm(2) once daily for 3 or 5 days and were evaluated through day 45. In the Phase 2 study, 2 treatment cohorts with face or scalp lesions received tirbanibulin ointment 1% once daily for 3 or 5 days over 25 cm(2) and were evaluated through day 57 Lesion reductions, clearance rates, safety, and pharmacokinetics were assessed. Results: Forearm AK lesions were reduced by day 45 in all Phase 1 cohorts (N=30). Complete AK clearance at day 57 for face/scalp AK lesions in Phase 2 cohorts (N=168) was demonstrated in 43% and 32% of participants of the 5-day and 3-day cohorts, respectively. Adverse reactions were mainly transient mild local erythema and flaking/scaling, pruritus, and pain. Tirbanibulin plasma concentrations were low or undetectable. Conclusion:Tirbanibulin ointment 1% was well tolerated and active in AK reduction. Based on activity, the 5-day regimen was selected for Phase 3 development.