ABSTRACT
We describe herein the synthesis and biological evaluation of a series of novel cephalosporins with potent activity against Pseudomonas aeruginosa. Introduction of various amino groups to the 4-position of a 3-amino-2-methylpyrazole cephalosporin 3-side chain resulted in enhanced MIC values against multiple Pseudomonas aeruginosa strains and ultimately led to the discovery of FR264205 (15) with excellent anti-bacterial activity and weak convulsion effect by direct intracerebroventricular injection assay.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Cephalosporins/chemical synthesis , Cephalosporins/pharmacology , Pseudomonas aeruginosa/drug effects , Animals , Anti-Bacterial Agents/adverse effects , Anti-Bacterial Agents/chemistry , Ceftazidime/pharmacology , Cephalosporins/adverse effects , Cephalosporins/chemistry , Drug Design , Drug Evaluation, Preclinical , Mice , Pseudomonas aeruginosa/growth & development , Seizures/chemically induced , Structure-Activity RelationshipABSTRACT
AmpC beta-lactamase is one of the leading causes of Pseudomonas aeruginosa (P. aeruginosa) resistance to cephalosporins. FR259647 is a cephalosporin having a novel pyrazolium substituent at the 3-position and exhibits excellent activity (MIC=1 microg/mL) against the AmpC beta-lactamase overproducing P. aeruginosa FP1380 strain in comparison with the third-generation cephalosporins FK518 [Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 454; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 455; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 456; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 457] (MIC=16 microg/mL) and ceftazidime (CAZ) (MIC=128 microg/mL). The stability of FR259647 and FK518 to AmpC beta-lactamase was evaluated using MIC assays against both the P. aeruginosa PAO1 strain and a PAO1 mutant strain overproducing AmpC beta-lactamase as a differential assay, which indicates that the main difference derives from their stability to AmpC beta-lactamase. A structural analysis using computer simulations indicated that the difference in stability may be due to steric hindrance of the 3-position substituents causing differential affinity. This steric hindrance may disturb entry of the cephalosporins into the binding pocket. We predicted the possibility of inhibition of entry as a potential means of enhancing stability by conformational analysis. In order to validate this speculation, novel FR259647 derivatives 4-9 were designed, calculated, synthesized, and evaluated. As a result, we demonstrated that their probability of entry correlated with the MIC ratio of the mutant strain to the parent strain and supports the validity of our model.
Subject(s)
Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/metabolism , Cephalosporins/chemistry , Cephalosporins/pharmacology , beta-Lactamase Inhibitors , beta-Lactamases/metabolism , Bacterial Proteins/chemistry , Enzyme Stability/drug effects , Imaging, Three-Dimensional , Models, Molecular , Molecular Structure , Protein Binding , Pseudomonas aeruginosa/drug effects , beta-Lactam Resistance/drug effects , beta-Lactamases/chemistryABSTRACT
A series of 3-(4-pyrazolylmethylthio)cephalosporins with various C-7 side chains was designed, synthesized and evaluated for antibacterial activity and oral absorption in rats. Antibacterial activity against Haemophilus influenzae was markedly increased by the C-7 oxime moiety. Deamination at the 2 position of, or introduction of a substituent such as halogen or methyl to, the 5 position of the (Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino) moiety improved oral absorption. Among these compounds, FR192752 having a (Z)-2-(2-amino-5-chlorothiazol-4-yl)-2-hydroxyiminoacetamido moiety, showed potent antibacterial activity against both Gram-positive and Gram-negative bacteria including H.influenzae and penicillin G-resistant Streptococcus pneumoniae (PRSP). Further, it showed higher oral absorption than CFDN and FK041.
