From a Micromonospora sp. in Lake Michigan sediment, we
isolated novel antibiotic molecules of the diazaquinomycin
class. An analogue, compound 3, displayed an in vitro activity
profile similar or superior to those of clinically used TB agents
and maintained potent inhibitory activity against a panel of
drug-resistant TB strains. This compound displayed a selectivity
profile targeted toward M. tuberculosis, even within the genus
Mycobacterium. Since the 1980s, other research groups have
reported that members of the diazaquinomycin class exhibited
weak antibacterial activity by targeting thymidylate synthase,
although no reports of their anti-TB activity existed and our
studies have suggested an alternate mechanism of action in M.
tuberculosis. Preliminary in vitro analysis of 3 predicts that
DAQA will exhibit high metabolic stability and, therefore, a
long predicted serum half-life in vivo. Further studies are
underway in our laboratories including mutant generation
experiments, screening of 3 against a large overexpression
library of essential M. tuberculosis genes, and determination of
the pharmacokinetic properties of 3 in mice. These studies aim
to further assess the potential of 3 as a TB drug lead and
identify the molecular target of the diazaquinomycins in M.
tuberculosis.