All-cause mortality rates in adults with carbapenem-resistant Gram-negative bacterial infections: a comprehensive review of pathogen-focused, prospective, randomized, interventional clinical studies

Pathogen-focused, randomized, controlled trials (PF-RCT) are important in the fight against carbapenem-resistant (CR) Gram-negative infections. Some recently approved antibiotics and older generic antibiotics with activity against CR Gram-negative bacteria were investigated in PF-RCTs in a variety of infections. We searched Pubmed, Cochrane database and international clinical trial databases for PF-RCTs for the period between 2005 and 2020 and compared the study designs, patient populations, infection types, pathogens, and Day-28 all-cause mortality (ACM). PF-RCTs are particularly challenging to quantitatively assess and compare due to the heterogeneity in infection types, pathogens, CR mechanism, inclusion/exclusion criteria, and endpoints. Data interpretation is further complicated by lack of formal statistical analysis plans and/or non-inferiority design, and limited power across most PF-RCTs. The studies with new antibiotics (i.e. plazomicin, meropenem/vaborbactam, cefiderocol) ranked lower regarding feasibility, with relatively small sample sizes (analyzed: 37–118) versus the comparative effectiveness studies of older generic drugs (analyzed: 94–406). ACM ranged between 11.8% and 40% for CR Enterobacterales, 17.7% and 57.4% for CR Acinetobacter spp., and 20.0% and 30.8% for CR Pseudomonas aeruginosa. The information gathered must be considered carefully alongside the study limitations and caution should be exercised when making direct comparisons across trials. PLAIN LANGUAGE SUMMARY New antibiotics to treat multidrug-resistant Gram-negative bacterial infections are needed because antimicrobial resistance has become a global threat. In recent years, several pathogen-focused, randomized, controlled clinical trials were conducted to test new antibiotics or combinations of older generic antibiotics in the fight against resistant bacteria. However, these trials were exceptionally challenging and most of them enrolled relatively few patients. These studies were highly heterogeneous in terms of species, antibiotics, infection site, mechanism of resistance, endpoints and patient factors. In these trials, all-cause mortality at Day 28 or Day 30 were numerically lower with the new antibiotics in infections caused by carbapenem-resistant (CR) Enterobacterales. However, in the trials which investigated CR Acinetobacter spp. infections, there was no reduction in all-cause mortality at Day 28 or Day 30 with combinations of older generic antibiotics compared with colistin monotherapy. Limited information was available for CR Pseudomonas aeruginosa. More pathogen-focused, randomized, controlled clinical trials with more feasible design and higher patient numbers are needed to demonstrate clinical benefit in drug-resistant infections.