DC-159a is a new 8-methoxy
fluoroquinolone that possesses a broad spectrum of antibacterial activity, with extended activity against gram-positive pathogens, especially streptococci and staphylococci from patients with
community-acquired infections.
DC-159a showed activity against Streptococcus spp. (MIC(90), 0.12 microg/ml) and inhibited the growth of 90% of
levofloxacin-intermediate and -resistant strains at 1 microg/ml. The MIC 90s of
DC-159a against Staphylococcus spp. were 0.5 microg/ml or less. Against
quinolone- and methicillin-resistant Staphylococcus aureus strains, however, the MIC 90 of
DC-159a was 8 microg/ml.
DC-159a was the most active against Enterococcus spp. (MIC 90, 4 to 8 microg/ml) and was more active than the marketed
fluoroquinolones, such as
levofloxacin,
ciprofloxacin, and
moxifloxacin. The MIC 90s of
DC-159a against Haemophilus influenzae, Moraxella catarrhalis, and Klebsiella pneumoniae were 0.015, 0.06, and 0.25 microg/ml, respectively. The activity of
DC-159a against Mycoplasma pneumoniae was eightfold more potent than that of
levofloxacin. The MICs of
DC-159a against Chlamydophila pneumoniae were comparable to those of
moxifloxacin, and
DC-159a was more potent than
levofloxacin. The MIC 90s of
DC-159a against Peptostreptococcus spp., Clostridium difficile, and Bacteroides fragilis were 0.5, 4, and 2 microg/ml, respectively; and among the
quinolones tested it showed the highest level of activity against anaerobic organisms.
DC-159a demonstrated rapid bactericidal activity against
quinolone-resistant Streptococcus pneumoniae strains both in vitro and in vivo. In vitro,
DC-159a showed faster killing than
moxifloxacin and
garenoxacin. The bactericidal activity of
DC-159a in a murine muscle
infection model was revealed to be superior to that of
moxifloxacin. These activities carried over to the in vivo efficacy in the murine
pneumonia model, in which treatment with
DC-159a led to bactericidal activity superior to those of the other agents tested.