Meiji Seika Pharma has reported positive results from the global Phase III Integral-1 trial evaluating nacubactam, a novel β-lactamase inhibitor, in patients with complicated urinary tract infections or acute uncomplicated pyelonephritis.
The study addresses a critical clinical need as antimicrobial resistance continues to limit treatment options for serious Gram-negative bacterial infections. Carbapenems remain among the last-resort therapies for severe infections, but rising resistance has increased demand for new agents that can preserve or expand treatment choices.
Integral-1 was a global, double-blind, randomised Phase III trial comparing nacubactam co-administered with either cefepime or aztreonam against imipenem-cilastatin, a carbapenem. The trial met its primary endpoint of composite clinical and microbiological response seven days after the end of treatment.
Cefepime-nacubactam demonstrated non-inferiority to imipenem-cilastatin and also showed superiority over the comparator. Aztreonam-nacubactam demonstrated non-inferiority versus imipenem-cilastatin. Safety outcomes were comparable between groups, with no new safety concerns identified.
Nacubactam differentiates itself through its dual mechanism. In addition to acting as a β-lactamase inhibitor, it inhibits penicillin-binding protein 2, an enzyme involved in bacterial cell wall synthesis. This mechanism may help distinguish it from other β-lactamase inhibitors and support activity against resistant pathogens, including carbapenem-resistant Enterobacterales.
The development programme also includes Integral-2, another Phase III trial evaluating nacubactam in patients with infections caused by carbapenem-resistant Enterobacterales. Positive Integral-2 results were presented at ESCMID Global 2026, with a manuscript currently in preparation.
From a regulatory perspective, Meiji Seika Pharma submitted an application in Japan in December 2025 for manufacturing and marketing approval of nacubactam. If approved, the therapy could strengthen the antibiotic pipeline at a time when healthcare systems are seeking new tools to combat antimicrobial resistance.
Looking ahead, key milestones will include regulatory review progress, publication of Integral-2 data, and further clarity on how nacubactam may be positioned within clinical practice. Its potential impact will depend on approval outcomes, antimicrobial stewardship considerations, and its ability to address urgent treatment gaps in resistant Gram-negative infections.
