ABSTRACT:
Increasing rates of antimicrobial resistance require additional safe and effective options for managing difficult-to-treat infections. SPR206 is a next-generation polymyxin with improved
in vivo
safety profiles. This study determined the
in vitro
activity of SPR206 against a diverse collection of gram-negative isolates. SPR206 was tested against 5,179 Enterobacterales,
Pseudomonas aeruginosa
, and
Acinetobacter
spp. collected from patients in the United States (US), Europe, Israel, and Turkey. Broth microdilution was performed following the Clinical & Laboratory Standards Institute (CLSI) guidelines, and MIC results interpreted by CLSI, European Committee on Antimicrobial Susceptibility Testing (EUCAST), and United States Food and Drug Administration (US FDA) criteria. SPR206 (MIC
50/90
, 0.25/0.25–0.5 mg/L) was active against
P. aeruginosa
, including the multidrug-resistant, extensively drug-resistant, and difficult-to-treat subsets, with 99.8–100% of isolates inhibited at MIC values of ≤2 mg/L. SPR206 inhibited 94.5% of
Acinetobacter
spp., including 90.4 and 87.9% of the multidrug-resistant (MIC
50/90
, 0.12/2 mg/L) and extensively drug-resistant (MIC
50/90
, 0.12/8 mg/L) subsets at MIC values of ≤2 mg/L. SPR206 (MIC
50/90
, 0.06/0.25 mg/L) inhibited 95.4% of non-Morganellaceae Enterobacterales at MIC values of ≤2 mg/L. SPR206 MIC
50
and MIC
90
values of 0.06 and 0.5 mg/L were obtained against carbapenem-resistant Enterobacterales from the US and Western Europe, whereas MIC
50
of 0.5 mg/L and MIC
90
of 64 mg/L were noted against carbapenem-resistant Enterobacterales isolates from Eastern Europe. SPR206 demonstrated potent activity against a large collection of gram-negative organisms, including resistant subsets. These results, along with an enhanced safety profile, warrant the development of SPR206 as a candidate for the treatment of infections caused by gram-negative bacteria.
IMPORTANCE:
SPR206 is a novel, next-generation polymyxin with improved safety profiles that demonstrates activity against gram-negative organisms. This study benchmarks the activity and spectrum of SPR206 against a large collection of gram-negative isolates, including multidrug-resistant and extensively drug-resistant
Acinetobacter
spp. and
Pseudomonas aeruginosa
, and carbapenem-resistant Enterobacterales collected from multiple medical sites in the US and Europe. Additional treatment options are needed as antimicrobial resistance emerges and spreads. The results presented in this manuscript show potent SPR206 activity against resistant and difficult-to-treat gram-negative organisms.