The FDA has approved fosfomycin (Contepo) for injection for the treatment of adult patients with complicated urinary tract infections (cUTIs), including acute pyelonephritis, caused by susceptible isolates of Escherichia coli and Klebsiella pneumoniae, according to Meitheal Pharmaceuticals. This approval addresses a critical unmet medical need, with an estimated three million cases of cUTIs treated in hospital settings annually.
Novel Mechanism Targets Resistant Pathogens
Fosfomycin represents the only FDA-approved epoxide antibacterial product, belonging to the phosphonic class of antibiotics. The drug works by covalently binding and inhibiting phosphoenolpyruvate transferase (MurA), which prevents the formation of cell wall precursors, blocks cell wall synthesis, and leads to bacterial destruction. Importantly, fosfomycin has demonstrated no known cross-resistance to other antibiotic classes.
"The rise of multi-drug-resistant pathogens poses a significant threat to our ability to combat infectious diseases, underscoring the continued need for novel therapies that target resistant organisms in patients having cUTIs," said Keith S. Kaye, MD, MPH, Chief of the Division of Allergy, Immunology and Infectious Diseases at Robert Wood Johnson Medical School.
ZEUS Trial Demonstrates Efficacy
The approval is supported by data from the phase 2/3 ZEUS trial (NCT02753946), which enrolled hospitalized patients with cUTI to assess the safety and efficacy of IV fosfomycin. The study found that IV fosfomycin was non-inferior to piperacillin/tazobactam in terms of the primary endpoint of overall success, defined as clinical cure and microbiological eradication at the test of cure visit on day 19.
In the microbiological intent-to-treat population, overall success was achieved in 63.5% (108 of 170) patients in the fosfomycin arm compared to 55.6% (94 of 169) in the piperacillin/tazobactam arm, with a treatment difference of 7.9 (95% CI, -3.1 to 18.9). Patients were randomly assigned to receive either 6 g fosfomycin three times daily or 4.5 g piperacillin/tazobactam three times daily for 7 days.
Safety Profile and Monitoring Requirements
Fosfomycin was generally well-tolerated in the trial. The most common adverse events occurring in 2% or higher of patients included transaminase elevations (10.3%), hypokalemia (9.9%), neutropenia (6.4%), nausea (4.3%), diarrhea (3.9%), vomiting (3.9%), hypocalcemia (3.9%), hypernatremia (3.4%), headache (2.6%), and hypophosphatemia (2.1%).
The drug requires careful monitoring due to its high sodium content of 1,980 mg per vial, which may result in electrolyte disturbances. Healthcare providers must monitor serum electrolyte levels and fluid status during treatment, with particular attention to patients who should restrict sodium intake or are prone to fluid overload. The drug has also been shown to prolong the QT interval in some patients, necessitating electrocardiographic monitoring.
Expanding Treatment Arsenal
"CONTEPO's safety, efficacy, and novel mechanism of action makes it a favorable new treatment option," said Keith Robinson, MD, MS, FCCP, Chief Medical Officer of Meitheal Pharmaceuticals. The approval marks the second branded antibiotic in Meitheal's portfolio, following the 2019 approval of lefamulin (Xenleta) for community-acquired bacterial pneumonia.
"The escalating public health issue of antimicrobial resistance and emergence of highly resistant organisms demands immediate attention and innovative therapeutic solutions," concluded Tom Shea, CEO of Meitheal Pharmaceuticals. "The approval of CONTEPO is a major milestone in our company's evolution and the fight against the ongoing threat of antibiotic resistance."
