Optimization of Isothiazolo[4,3-b]pyridine-Based Inhibitors of Cyclin G Associated Kinase (GAK) with Broad-Spectrum Antiviral Activity

Abstract

There is an urgent need for strategies to combat dengue and other emerging viral infections. We reported that cyclin G-associated kinase (GAK), a cellular regulator of the clathrin-associated host adaptor proteins AP-1 and AP-2, regulates intracellular trafficking of multiple unrelated RNA viruses during early and late stages of the viral lifecycle. We also reported the discovery of potent, selective GAK inhibitors based on an isothiazolo[4,3- b]pyridine scaffold, albeit with moderate antiviral activity. Here, we describe our efforts leading to the discovery of novel isothiazolo[4,3- b]pyridines that maintain high GAK affinity and selectivity. These compounds demonstrate improved in vitro activity against dengue virus, including in human primary dendritic cells, and efficacy against the unrelated Ebola and chikungunya viruses. Moreover, inhibition of GAK activity was validated as an important mechanism of antiviral action of these compounds. These findings demonstrate the potential utility of a GAK-targeted broad-spectrum approach for combating currently untreatable emerging viral infections.

A Scaffold‐Hopping Strategy toward the Identification of Inhibitors of Cyclin G Associated Kinase

“…Recently, we reported the discovery of potent GAK inhibitors based on an isothiazolo[4,3 ‐b ]pyridine scaffold, of which compounds 1 , 2 , and 3 are the most promising representatives (Figure ). These compounds display potent GAK affinity ( K d values in the range of 8–80 n m ), are selective, and are also endowed with broad‐spectrum in vitro antiviral activity against HCV, DENV, EBOV, and CHIKV …”

“…Previous explorations of the structure–activity relationship (SAR) of isothiazolo[4,3 ‐b ]pyridines as GAK inhibitors focused on modifications of the functional groups at positions 3 and 6 of the scaffold . In this study, an alternative approach based on scaffold hopping was followed.…”

“…These compoundsd isplay potent GAK affinity (K d valuesi nt he range of 8-80 nm), are selective, and are also endowedw ith broad-spectrum in vitro antiviral activity against HCV,D ENV, EBOV,a nd CHIKV. [15,16] Previous explorations of the structure-activity relationship (SAR) of isothiazolo [4,3-b]pyridines as GAK inhibitors focused on modifications of the functional groups at positions3and 6 of the scaffold. [15][16][17] In this study,a na lternative approach based on scaffold hopping was followed.…”

“…[15,16] Previous explorations of the structure-activity relationship (SAR) of isothiazolo [4,3-b]pyridines as GAK inhibitors focused on modifications of the functional groups at positions3and 6 of the scaffold. [15][16][17] In this study,a na lternative approach based on scaffold hopping was followed. Scaffold hopping is a widelya pplied medicinal chemistry strategy in whicht he core skeleton (the scaffold) of lead molecules is subjected to bioisosteric replacements, leading to the discovery of structurally novel compounds.…”

Medicinal chemistry strategies toward host targeting antiviral agents

“…The mechanism of action studies confirmed that the inhibition of GAK is an important target underlying the broad-spectrum antiviral activity of compound 51. 115,116 The other chemotype of GAK inhibitor is quin(az)oline, 117,118 yet their antiviral activity was not probed.…”