Tirbanibulin Mesylate (C₁₇H₁₅F₃N₄O₂·CH₃SO₃H) is a synthetic specialty chemical and active pharmaceutical ingredient (API) used in dermatological formulations for the treatment of actinic keratosis, a precancerous skin condition. It acts as a potent microtubule disruptor, rapidly inhibiting tubulin polymerization, inducing G2/M cell cycle arrest, apoptosis, and localized inflammation in hyperproliferative keratinocytes. Supplied at high purity (≥98%) for pharmaceutical research, development, and manufacturing, it enables targeted topical applications in ointments (e.g., 1% w/w, applied once daily for 5 days) with minimal systemic absorption and a favorable safety profile (common local reactions: erythema, scaling, crusting).