AstraZeneca and partner Forest Laboratories have unveiled plans for a Phase III programme to investigate a combination antibiotic against superbug infections.

Specifically, CAZ-AVI, combines a broad-spectrum cephalosporin (ceftazidime) and a novel beta-lactamase inhibitor (avibactam) will be tested to treat hospitalised patients with serious Gram-negative bacterial infections including complicated intra-abdominal infections (cIAI) and complicated urinary tract infections (cUTI). The study programme will include five Phase III trials designed to demonstrate that CAZ-AVI is effective for patients with cIAI and cUTI including those with infections that may be resistant to currently available antibiotics.

The decision to advance the drug is based on two Phase II trials and the first showed that the efficacy of CAZ-AVI given with metronidazole in adults was similar to meropenem, an established treatment given to patients with cIAIs. The second study showed that the combo was as effective as imipenem cilastatin, which is used for cUTI patients; the data from both trials showed that CAZ-AVI in general was well tolerated.

Anders Ekblom, AstraZeneca's chief of global medicines development, said that this new step in the development of CAZ-AVI "demonstrates our commitment to help meet the needs of hospitals facing additional healthcare costs linked to a rapid increase of  antimicrobial resistant organisms". If all goes well, the firms hope to file the combo in 2014.

The AstraZeneca/Forest collaboration began in December 2009, when the Anglo-Swedish drugmaker acquired Novexel, a private infection research company in France. The firm simultaneously announced an agreement to collaborate with Forest on two late-stage antibiotics - ceftazidime and ceftaroline fosamil - in combination with Novexel's avibactam.