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

November 2024 | Volume 23 | Issue 11 | 986 | Copyright © November 2024


Published online October 23, 2024

doi:10.36849/JDD.7985

Paytra A. Klein MBAa, Colin Kincaid BSb, Arash Babadjouni MSb, Natasha A. Mesinkovska MD PhDb

aAlbany Medical College, Albany, NY
bUniversity of California Irvine, Department of Dermatology, Irvine, CA

Abstract
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

INTRODUCTION

Hyperpigmentation, the overproduction of melanin within the skin, is estimated to be the 11th most prevalent disorder seen in dermatology practices and the most frequent skin complaint among patients aged 40 to 45 years.1,2 This condition predominantly affects women with Fitzpatrick skin types (FST) III to V and can be cosmetically disfiguring, alter psychosocial well-being, and adversely impact the quality of life in affected individuals.3,4

Current treatment options - including topicals (eg, hydroquinone, arbutin, and kojic acid), oral agents (eg, cysteamine hydrochloride, melatonin, and tranexamic acid), chemical peels, and laser therapy - have varying efficacies,side effects, and may require lengthy treatment duration to achieve desired effects.5 Hydroquinone is currently the criterion standard for hyperpigmentation treatment. However, its use is limited by several potential adverse effects including contact dermatitis, skin irritation, hypopigmentation, and, paradoxically, exogenous ochronosis (bluish-gray or black hyperpigmentation).6,7 In fact, the European Union banned hydroquinone from cosmetic use due to its adverse effect profile.6  There is therefore a need for clinically efficacious and safer alternative therapies for treating hyperpigmentation.

Tyrosinase, the rate-limiting enzyme of melanogenesis, is an attractive inhibitory target for treating hyperpigmentation (Figure 1).6 While several tyrosinase inhibitors are already 
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