Heterogeneity of Recent Phase 3 Complicated Urinary Tract Infection Clinical Trials

Area of Science:

• Infectious Diseases
• Clinical Pharmacology
• Regulatory Science

Background:

• The US Food and Drug Administration (FDA) regulatory pathway for new antibiotics targeting antibiotic-resistant Gram-negative infections requires complicated urinary tract infection (cUTI) trials.
• These trials often use an active control susceptible to clinical isolates, enabling noninferiority study designs.
• However, significant variability exists in trial designs and patient populations despite adherence to regulatory guidelines.

Purpose of the Study:

• To analyze patient selection and outcome parameters in recent cUTI trials pivotal to new drug applications (NDAs).
• To identify variables influencing trial design and patient demographics within regulatory frameworks.

Main Methods:

• A selective descriptive analysis of publicly available data from 6 cUTI trials for new antibiotics against multidrug-resistant Gram-negative infections.
• Included antibiotics: ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, cefiderocol, plazomicin, and fosfomycin.
• Eravacycline was excluded as it was not approved for cUTI.

Main Results:

• Key comparisons included microbiologic modified intent-to-treat sample size, patient age, sex distribution, presence of acute pyelonephritis (AP), baseline pathogens (e.g., *Escherichia coli*), and protocol-specified switch to oral antibiotics.
• Outcome measures comprised clinical response, microbiologic eradication, and composite endpoints, including a subset of patients with AP.
• The proportion of AP varied significantly across studies.

Conclusions:

• Trial designs adhering to regulatory guidelines can still encompass diverse patient populations.
• The proportion of AP in a study influenced patient demographics (age, gender) and baseline microbiology.
• Lower AP proportions correlated with older patients, fewer females, less *E. coli*, and reduced success rates.
• Fluoroquinolones and piperacillin/tazobactam warrant reconsideration as active comparators due to high resistance rates.