This is a Phase 1, open-label, single-center PK study in healthy adult male and female participants between 18 and 55 years of age (both inclusive). Thirty-one participants will each undergo one standard bronchoscopy with bronchoalveolar lavage (BAL) following the fifth dose of ceftibuten-ledaborbactam etzadroxil or ceftibuten alone. BAL fluid samples and plasma samples will be collected at designated timepoints to determine the concentrations of ceftibuten, ledaborbactam, and urea.

Inclusion Criteria:

• Healthy adults 18-55 years
• Males or non-pregnant, non-lactating females
• Body Mass Index: ≥18 and ≤32 kg/m2
• Forced expiratory volume in 1 second of at least 80% of predicted value
• Laboratory values meeting defined entry criteria

Exclusion Criteria:

• History of drug allergy or hypersensitivity to penicillin, cephalosporin, or β-lactam antibacterial drug or to medications used during a bronchoscopy
• Conditions that potentially alter absorption and/or excretion of orally administered drugs
• History or presence of significant diseases, including any clinically relevant acute illness or surgery within the past 3 months
• Positive alcohol, drug, or tobacco use/test