# KT‐939: A Next‐Generation Human Tyrosinase Inhibitor With Superior Efficacy for the Safe Management of Hyperpigmentation

## TL;DR

KT-939 is a new, safe, and effective tyrosinase inhibitor that reduces skin pigmentation and shows antioxidant and anti-inflammatory benefits.

## Contribution

KT-939 is a next-generation tyrosinase inhibitor with superior potency and safety compared to existing agents.

## Key findings

- KT-939 inhibited human tyrosinase with an IC₅₀ of 0.07 μM, four times more potent than Thiamidol.
- It reduced melanin production in human melanocytes and showed antioxidant and anti-inflammatory effects.
- A 28-day clinical trial showed improved skin lightening and tolerability in sensitive skin.

## Abstract

Tyrosinase is the rate‐limiting enzyme in melanin biosynthesis, and its overactivity contributes to hyperpigmentation disorders. Existing tyrosinase inhibitors are often limited by poor potency against human tyrosinase (hTYR) or safety concerns.

To evaluate the inhibitory potency, safety, and multifunctional activity of KT‐939, a newly synthesized human tyrosinase inhibitor, compared with established depigmenting agents.

KT‐939 was synthesized and tested in vitro for tyrosinase inhibition, melanin suppression in human melanocytes, antioxidant activity (DPPH radical scavenging, NRF2 pathway activation), and anti‐inflammatory activity (cytokine expression in LPS‐stimulated macrophages). Safety was assessed in multiple skin‐related cell lines. A 28‐day, single‐center clinical study in healthy women with sensitive skin assessed the effects of 0.2% KT‐939 lotion on pigmentation and tolerability.

KT‐939 strongly inhibited hTYR (IC₅₀ = 0.07 μM), demonstrating ~4‐fold greater potency than Thiamidol and far surpassing other comparators. In melanocytes, KT‐939 reduced melanin production (IC₅₀ = 0.36 μM) with reversible effects upon withdrawal. KT‐939 also displayed antioxidant activity, NRF2 activation, and suppression of pro‐inflammatory cytokines, without cytotoxicity up to 50 μM. Clinically, 28 days of KT‐939 lotion use improved skin spot lightening, tone uniformity, and overall brightness, with good tolerability in sensitive skin.

KT‐939 is a potent and safe human tyrosinase inhibitor with additional antioxidant and anti‐inflammatory activity. These findings support its potential in cosmetic skin brightening and as a therapeutic candidate for hyperpigmentation disorders.