In vivo activities of novel benzoxazinorifamycins against Mycobacterium leprae.

Among the four newly synthesized benzoxazinorifamycin derivatives, KRM-1648 and KRM-2312 completely inhibited the multiplication of rifampicin-sensitive as well as rifampicin-resistant strains of M. leprae in the foot-pads of mice. Both were found to be more potent than rifampicin and were bactericidal. In combination with ofloxacin, another potent bactericidal drug against M. leprae, both KRM-1648 and KRM-2312 exhibited synergism. Thus, combination of one of these benzoxazinorifamycin derivatives and ofloxacin in multidrug regimens is worth evaluating in clinical trials.