Pharmacokinetics and pharmacodynamics of ceftobiprole, an anti-MRSA cephalosporin with broad-spectrum activity

Ceftobiprole, a beta-lactam, is the first of a new generation of broad-spectrum cephalosporins in late-stage development with activity against methicillin-resistant Staphylococcus aureus (MRSA) in addition to broad-spectrum bactericidal activity against other Gram-positive and Gram-negative pathogens. The prodrug, ceftobiprole medocaril, is converted rapidly and almost completely to the active drug, ceftobiprole, upon infusion by type A esterases. In humans, ceftobiprole binds minimally (16%) to plasma proteins, and binding is independent of the drug and protein concentrations. Its steady-state volume of distribution (18.4 L) approximates the extracellular fluid volume in humans. Ceftobiprole undergoes minimal hepatic metabolism, and the primary metabolite is the beta-lactam ring-opened hydrolysis product (open-ring metabolite). Systemic exposure of the open-ring metabolite accounts for 4% of ceftobiprole exposure following single-dose administration; approximately 5% of the dose is excreted in the urine as the metabolite. Ceftobiprole does not significantly induce or inhibit relevant cytochrome P450 enzymes and is neither a substrate nor an inhibitor of P-glycoprotein. Ceftobiprole is rapidly eliminated, primarily unchanged, by renal excretion, with a terminal elimination half-life of 3 hours; the predominant mechanism responsible for elimination is glomerular filtration, with approximately 89% of the dose being excreted as the prodrug, active drug (ceftobiprole) and open-ring metabolite. The pharmacokinetics of ceftobiprole are linear following single and multiple infusions of 125-1000 mg. Steady-state drug concentrations are attained on the first day of dosing, with no appreciable accumulation when administered three times daily (every 8 hours) and twice daily (every 12 hours) in subjects with normal renal function. Low intersubject variability has been seen across studies. Ceftobiprole exposure is slightly higher (~15%) in females than in males; this difference has been attributed to bodyweight. However, the pharmacodynamics of ceftobiprole are similar in males and females, and dosing adjustments are not required based on gender. In patients with moderate to severe renal impairment, systemic clearance of ceftobiprole correlated well with creatinine clearance. For these patients, dose adjustments for the treatment of infections caused by target pathogens, including MRSA, should be based on creatinine clearance. Ceftobiprole is undergoing clinical evaluation in phase III trials in patients with complicated skin and skin structure infections, patients with nosocomial pneumonia, and community-acquired pneumonia in hospitalized patients.