In vivo efficacy and pharmacokinetics of tomopenem (CS-023), a novel carbapenem, against Pseudomonas aeruginosa in a murine chronic respiratory tract infection model

Tomopenem (CS-023) is a novel parenteral carbapenem with broad-spectrum activity against Gram-positive and -negative bacteria, as well as potent activity against drug-resistant pathogens, including penicillin-resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. We compared the in vivo activity of tomopenem and that of meropenem in a chronic lower respiratory infection mouse model of P. aeruginosa. Mice with chronic airway infection by P. aeruginosa were treated with saline (as the control, twice daily), tomopenem (100 mg/kg, twice daily) or meropenem (100 mg/kg, twice daily) for 7 days. After treatment, the number of viable bacteria in lungs and histopathological findings were analysed. The pharmacokinetics of tomopenem and meropenem were also analysed after initial treatment. The number of viable bacteria in lungs treated with saline, tomopenem or meropenem was 4.21 +/- 1.28, 2.91 +/- 0.87 and 3.01 +/- 1.00 log(10) cfu/lung (mean +/- SEM), respectively (P < 0.05, control versus tomopenem- or meropenem-treated groups). In the histopathological examination of lung specimens, the control group had the features of chronic bronchial infection; however, tomopenem- and meropenem-treated groups had fewer inflammatory cells compared with the control group. The pharmacokinetic parameter of % time above MIC for tomopenem and meropenem was 16% and 17% in sera and 15% and 18% in lungs, respectively. Tomopenem significantly reduced the number of viable bacteria in a murine model of chronic airway infection by P. aeruginosa, compared with the control. Considering the longer half-life of tomopenem in humans compared with most other carbapenems, tomopenem treatment of chronic airway infection with P. aeruginosa is expected to be efficacious.