Isobutylamido Thiazolyl Resorcinol (Thiamidol) for Combatting Hyperpigmentation: A Systematic Review of Clinical Studies.

Background: Tyrosinase is the rate-limiting enzyme of melanogenesis and thus an ideal inhibitory target for treating hyperpigmentation. There are many commercially available tyrosinase inhibitors with limited clinical efficacy. A recent screen of 50,000 compounds found isobutylamido thiazolyl resorcinol (ITR) to be the most potent inhibitor of human tyrosinase.

Objective: To summarize the current evidence on the efficacy and adverse effects of ITR in treating hyperpigmentation.

Methods: A literature search was conducted using PubMed and Google Scholar databases in June 2022. Fourteen clinical studies investigating the use of topical ITR in hyperpigmentation treatment or prevention were identified.

Results: Most studies (n=13) investigated topical ITR as a treatment, while only one investigated ITR as a preventative measure against hyperpigmentation. All studies (n=14) found ITR to provide statistically significant improvements to hyperpigmentation conditions, including facial hyperpigmentation (n=3), melasma (n=5), post-inflammatory hyperpigmentation (PIH) (n=3), and UV-induced hyperpigmentation (n=3). Evidence suggests that the effective dosage and duration of topical ITR appears to be 0.1% to 0.2% ITR 2 to 4 times daily for 12 to 24 weeks. Successful prevention of UVB-induced hyperpigmentation has been seen following twice-daily topical ITR application for 3 weeks (P<0.001).

Conclusion: Topical ITR can significantly reduce hyperpigmentation, however, the evidence for its use is limited. Further investigation is warranted to identify the optimal dosage and application schedule of ITR, as well as compare the efficacy of ITR vs hydroquinone to determine if ITR is superior to the current standard of care. J Drugs Dermatol. 2024;23(11):986-991.  doi:10.36849/JDD.7985.