Thieno(2,3-b)pyridines—A new class of multidrug resistance (MDR) modulators

Abstract To identify new potent multidrug resistance modulators, we have synthesized a series of novel thieno[2,3- b ]pyridines and furo[2,3- b ]pyridines, and examined their stucture–activity relationships. All synthesized compounds were tested to determine BCRP1, P-gp, and MRP1 inhibitor activity, and most potent MDR modulators were also screened for their toxicity, cytotoxicity and Ca 2+ channel antagonist activity. Among these compounds, thieno[2,3- b ]pyridine ( 6r ) was found to exhibit a potent P-gp inhibitory action with EC 50  = 0.3 ± 0.2 μM, MRP1 inhibitory action with EC 50  = 1.1 ± 0.1 μM and BCRP1 inhibitory action with EC 50  = 0.2 ± 0.05 μM and may represent suitable candidate for further pharmacological studies.