Pyrazolylthiazole as ΔF508-Cystic Fibrosis Transmembrane Conductance Regulator Correctors with Improved Hydrophilicity Compared to Bithiazoles

Deletion of phenylalanine residue 508 (ΔF508) in the cystic fibrosis (CF) transmembrane conductance regulator protein (CFTR) is a major cause of CF. Small molecule ‘correctors’ of defective ΔF508-CFTR cellular processing hold promise for CF therapy. We previously identified and characterized bithiazole CF corrector 1 and s-cis-locked bithiazole 2. Herein, we report the regiodivergent synthesis of Nγ and Nβ isomers of thiazole-tethered pyrazoles with improved hydrophilicity compared to bithiazoles. We synthesized a focused library of fifty-four pyrazolylthiazoles 3, which included examples of both regioisomers 4 and 5. The thiazole-tethered pyrazoles allowed incorporation of property-modulating functionality on the pyrazole ring – ester, acid, and amide – while retaining ΔF508-CFTR corrector activity (EC50) of under 1 μM. The most active pyrazolylthiazole (14h) has an experimentally determined logP of 4.1, which is 1.2 log units lower than bithiazole CF corrector 1.