Antimycobacterial activities of 2,4-diamino-5-deazapteridine derivatives and effects on mycobacterial dihydrofolate reductase

Development of new antimycobacterial agents for Mycobacterium avium complex MAC) infections is important particularly for persons coinfected with huma n immunodeficiency virus, The objectives of this study were to evaluate the in vitro activity of 2,4-diamino-5-methyl-5-deazapteridines (DMDPs) agains t MAC and to assess their activities against MAC dihydrofolate reductase re combinant enzyme (rDHFR), Seventy-seven DMDP derivatives were evaluated ini tially for in vitro activity against one to three strains of MAC (NJ168, NJ 211, and/or NJ3404. MICs were determined with 10-fold dilutions of drug and a colorimetric (Alamar Blue) microdilution broth assay, MAC rDHFR 50% inhi bitory concentrations versus those of human rDHFR were also determined, Sub stitutions at position 5 of the pteridine moiety included -CH3, -CH2CH3, an d -CH2OCH3 groups. Additionally, different substituted and unsubstituted ar yl groups were linked at position 6 through a two-atom bridge of either -CH 2NH, -CH2N(CH3), -CH2CH2, or -CH2S, All but 4 of the 77 derivatives were ac tive against MAC NJ168 at concentrations of less than or equal to 13 mu g/m l. Depending on the MAC strain used, 81 to 87% had MICs of less than or equ al to 1.3 mu g/ml. Twenty-one derivatives were > 100-fold more active again st MAC rDHFR than against human rDHFR In general, selectivity was dependent on the composition of the two-atom bridge at position 6 and the attached a ryl group with substitutions at the 2' and 5' positions on the phenyl ring. Using this assessment, a rational synthetic approach was implemented that resulted in a DMDP derivative that had significant intracellular activity a gainst a MAC-infected Mono Mac 6 monocytic cell line. These results demonst rate that it is possible to synthesize pteridine derivatives that have sele ctive activity against MAC.