Antimycobacterial activity of a new rifamycin derivative, 3-(4-cinnamylpiperazinyl iminomethyl) rifamycin SV (T9).

The antimycobacterial activities of a new rifampin (RIF) derivative, 3-(4-cinnamylpiperazinyl iminomethyl) rifamycin SV (To), against 20 susceptible and multidrug-resistant strains of Mycobacterium tuberculosis and 20 Mycobacterium avium complex (MAC) strains were investigated. The radiometric MICs of T9 for M. tuberculosis were significantly lower than those of RIF. The MICs of T9 and RIF at which 90% of the RIF-susceptible strains were inhibited were < or = 0.25 and < or = 0.5 micrograms/ml, respectively. Interestingly, T9 had lower MICs against some RIF-resistant M. tuberculosis strains. T9 had better activity against MAC strains, and the MIC at which 90% of the MAC strains were inhibited was < or = 0.125 micrograms/ml, and that of RIF was < or = 2.0 micrograms/ml. T9 also showed high in vitro bactericidal and intracellular activities which were significantly superior to those of RIF against both M. tuberculosis, and MAC strains. More importantly, T9 showed excellent in vivo activity against M. tuberculosis H37Rv compared with that of RIF in both the lungs and spleens of C57BL/6 mice, indicating the potential therapeutic value of T9 in the treatment of mycobacterial infections.