Comparative molecular field analysis of fenoterol derivatives interacting with an agonist-stabilized form of the ß2-adrenergic receptor.

The ß2-adrenergic receptor (ß2-AR) agonist [(3)H]-(R,R')-methoxyfenoterol was employed as the marker ligand in displacement studies measuring the binding affinities (Ki values) of the stereoisomers of a series of 4'-methoxyfenoterol analogs in which the length of the alkyl substituent at α' position was varied from 0 to 3 carbon atoms. The binding affinities of the compounds were additionally determined using the inverse agonist [(3)H]-CGP-12177 as the marker ligand and the ability of the compounds to stimulate cAMP accumulation, measured as EC50 values, were determined in HEK293 cells expressing the ß2-AR. The data indicate that the highest binding affinities and functional activities were produced by methyl and ethyl substituents at the α' position. The results also indicate that the Ki values obtained using [(3)H]-(R,R')-methoxyfenoterol as the marker ligand modeled the EC50 values obtained from cAMP stimulation better than the data obtained using [(3)H]-CGP-12177 as the marker ligand. The data from this study was combined with data from previous studies and processed using the Comparative Molecular Field Analysis approach to produce a CoMFA model reflecting the binding to the ß2-AR conformation probed by [(3)H]-(R,R')-4'-methoxyfenoterol. The CoMFA model of the agonist-stabilized ß2-AR suggests that the binding of the fenoterol analogs to an agonist-stabilized conformation of the ß2-AR is governed to a greater extend by steric effects than binding to the [(3)H]-CGP-12177-stabilized conformation(s) in which electrostatic interactions play a more predominate role.

Discovery and optimization of benzotriazine di-N-oxides targeting replicating and nonreplicating Mycobacterium tuberculosis.

Compounds bactericidal against both replicating and nonreplicating Mtb may shorten the length of TB treatment regimens by eliminating infections more rapidly. Screening of a panel of antimicrobial and anticancer drug classes that are bioreduced into cytotoxic species revealed that 1,2,4-benzotriazine di-N-oxides (BTOs) are potently bactericidal against replicating and nonreplicating Mtb. Medicinal chemistry optimization, guided by semiempirical molecular orbital calculations, identified a new lead compound (20q) from this series with an MIC of 0.31 µg/mL against H37Rv and a cytotoxicity (CC(50)) against Vero cells of 25 µg/mL. 20q also had equivalent potency against a panel of single-drug resistant strains of Mtb and remarkably selective activity for Mtb over a panel of other pathogenic bacterial strains. 20q was also negative in a L5178Y MOLY assay, indicating low potential for genetic toxicity. These data along with measurements of the physiochemical properties and pharmacokinetic profile demonstrate that BTOs have the potential to be developed into a new class of antitubercular drugs.