CS-834 is a beta-lactam antibiotic of a carbapenem class, developed by the Japanese company Sankyo Co. Ltd. CS-834 is an ester-type prodrug of the active metabolite R-95867. The drug showed potent and well balanced antibacterial activity as well as stability against dehydropeptidase-I. The in vivo efficacy of CS-834 was evaluated in murine systemic infections caused by 16 strains of gram-positive and -negative pathogens. The efficacy of CS-834 was in many cases superior to those of cefteram pivoxil, cefpodoxime proxetil, cefdinir, and cefditoren pivoxil, especially against infections caused by S. aureus, penicillin-resistant S. pneumoniae, E. coli, Citrobacter freundii, and Proteus vulgaris. Pharmacokinetics of CS-834 was evaluated in healthy male volunteers, but no further clinical development of the drug was reported.