Sara Lopez

Synthesis and spectrum of the neoglycoside ACHN-490.

ABSTRACT ACHN-490 is a neoglycoside, or “next-generation” aminoglycoside (AG), that has been identified as a potentially useful agent to combat drug-resistant bacteria emerging in hospitals and health care facilities around the world. A focused medicinal chemistry campaign produced a collection of over 400 sisomicin analogs from which ACHN-490 was selected. We tested ACHN-490 against two panels of Gram-negative and Gram-positive pathogens, many of which harbored AG resistance mechanisms. Unlike legacy AGs, ACHN-490 was active against strains expressing known AG-modifying enzymes, including the three most common such enzymes found in Enterobacteriaceae. ACHN-490 inhibited the growth of AG-resistant Enterobacteriaceae (MIC90, ≤4 μg/ml), with the exception of Proteus mirabilis and indole-positive Proteae (MIC90, 8 μg/ml and 16 μg/ml, respectively). ACHN-490 was more active alone in vitro against Pseudomonas aeruginosa and Acinetobacter baumannii isolates with AG-modifying enzymes than against those with altered permeability/efflux. The MIC90 of ACHN-490 against AG-resistant staphylococci was 2 μg/ml. Due to its promising in vitro and in vivo profiles, ACHN-490 has been advanced into clinical development as a new antibacterial agent.

Resistance of Streptococcus pneumoniae to Deformylase Inhibitors Is Due to Mutations in defB

ABSTRACT Resistance to peptide deformylase inhibitors in Escherichia coli or Staphylococcus aureus is due to inactivation of transformylase activity. Knockout experiments in Streptococcus pneumoniae R6x indicate that the transformylase (fmt) and deformylase (defB) genes are essential and that adef paralog (defA) is not. Actinonin-resistant mutants of S. pneumoniae ATCC 49619 harbor mutations indefB but not in fmt. Reintroduction of the mutated defB gene into wild-type S. pneumoniaeR6x recreates the resistance phenotype. The altered enzyme displays decreased sensitivity to actinonin.

Novel antibacterial azetidine lincosamides.

The synthesis and evaluation of novel azetidine lincosamides 1 are described. Eleven new (3-trans-alkyl)azetidine-2-carboxylic acids were synthesized via alkylation of N-TBS-4-oxo-azetidine-2-carboxylic acid and subsequent elaboration then coupled to 7-chloro-1-methylthio-lincosamine. The resulting lincosamides differ from the drug clindamycin in both the size of the ring and the position/structure of the alkyl side-chain. SAR within the series was explored with attention to alkyl variants in positions 1 and 3 of the azetidine ring.