KT203 (Synonyms: ML-296)

IC50: < 5 nM

KT203 is an ABHD6 inhibitor.

ABHD6, a unique and highly conserved enzyme in mammals, is prominently expressed in brain, liver, kidney, and brown adipose tissue based on global gene expression analysis and activitybased protein profiling (ABPP).

In vitro: The in-vitro potency of KT203 was studied and it was found that KT203 was able to potently inhibit ABHD6 as measured by gelbased competitive ABPP and 2-AG hydrolysis assays. Moreover, the in-situ potency was then measured by treating Neuro2A cells with varying concentrations of KT203 for 4 h and the results showed that KT203 inhibited ABHD6 with IC50 values in the subnanomolar range [1].

In vivo: In a previous animal study, mice were treated intraperitoneally with KT203 at various doses (0.1-1 mg/kg) for 4 h. Results showed that KT203 had near-complete blockade of ABHD6 in the liver at the highest dose tested. At lower doses, KT203 showed about 80% inhibition of ABHD6 in the liver. Notably, KT203 exhibited impressive selectivity in the mouse liver even at higher doses, showing little cross-reactivity against the numerous carboxylesterase enzymes that are common off-targets of mechanism-based SH inhibitors in rodents. In addition, KT203 showed good selectivity against other brain and liver SHs as judged by gelbased ABPP, suggesting a single major off-target, carboxylesterase-1 (CES1) [1].

Clinical trial: Up to now, KT203 is still in the preclinical development stage.

Reference:
[1] Hsu KL, Tsuboi K, Chang JW, Whitby LR, Speers AE, Pugh H, Cravatt BF.  Discovery and optimization of piperidyl-1,2,3-triazole ureas as potent, selective, and in vivo-active inhibitors of α/β-hydrolase domain containing 6 (ABHD6). J Med Chem. 2013 Nov 14;56(21):8270-9.