ABSTRACT
TD-1792 is a novel glycopeptide-cephalosporin heterodimer investigational antibiotic that displays potent bactericidal effects against clinically relevant Gram-positive organisms
in vitro
. The present studies evaluated the
in vivo
pharmacokinetics (PK) and pharmacodynamics (PD) of TD-1792 in the neutropenic murine thigh infection animal model. TD-1792, dosed subcutaneously (SC), produced dose-dependent reduction in the thigh bacterial burden of several organisms, including methicillin-susceptible and -resistant strains of
Staphylococcus aureus
and
Staphylococcus epidermidis
(MSSA, MRSA, MSSE, MRSE, respectively), penicillin-susceptible strains of
Streptococcus pneumoniae
(PSSP),
Streptococcus pyogenes
, and vancomycin-intermediate-susceptible
Staphylococcus aureus
(VISA). In single-dose efficacy studies, the 1-log
10
CFU kill effective dose (ED
1-log kill
) estimates for TD-1792 ranged from 0.049 to 2.55 mg/kg of body weight administered SC, and the bacterial burden was reduced by up to 3 log
10
CFU/g from pretreatment values. Against
S. aureus
ATCC 33591 (MRSA), the total 24-h log
10
stasis dose (ED
stasis
) and ED
1-logkill
doses for TD-1792 were 0.53 and 1.11 mg/kg/24 h, respectively, compared to 23.4 and 54.6 mg/kg/24 h for vancomycin, indicating that TD-1762 is 44- to 49-fold more potent than vancomycin. PK-PD analysis of data from single-dose and dose-fractionation studies for MRSA (ATCC 33591) demonstrated that the total-drug 24-h area under the concentration-time curve-to-MIC ratio (AUC/MIC ratio) was the best predictor of efficacy (
r2
= 0.826) compared to total-drug maximum plasma concentration of drug-to-MIC ratio (Cmax/MIC ratio;
r2
= 0.715) and percent time that the total-drug plasma drug concentration remains above the MIC (%Time>MIC;
r2
= 0.749). The magnitudes of the total-drug AUC/MIC ratios associated with net bacterial stasis, a 1-log
10
CFU reduction from baseline and near maximal effect, were 21.1, 37.2, and 51.8, respectively. PK-PD targets based on such data represent useful inputs for analyses to support dose selection decisions for clinical studies of patients.