In an attempt to search for clinically useful antitumor agents, we have discovered that a series of 1,7-disubstituted-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids possessed moderate cytotoxic activity. We investigated the structure-activity relationships in this series of compounds by changing N-1 and C-7 positions and the core ring structure itself and evaluated the synthesized compounds against several murine and human tumor cell lines. These modifications led us to the following findings. (1) The 2-thiazolyl group at the N-1 position of the naphthyridine structure is the best substituent for antitumor activity. (2) Regarding core ring structure, the naphthyridine derivative is the most active followed by pyridopyrimidine analogue. (3) At the C-7 position, aminopyrrolidine derivatives are more effective than other amines or thioether derivatives. Finally, the trans-3-amino-4-methoxypyrrolidinyl derivative (43j) and the 3-amino-3-methylpyrrolidinyl derivative (43f) as well as 3-aminopyrrolidinyl derivative (AT-3639, 1) were determined to be effective in in vitro and in vivo antitumor assays, and their activity was comparable to that of etoposide.
E1040 is a new parenteral cephalosporin with a broad antibacterial spectrum and potent activity against Gram-negative bacteria including Pseudomonas aeruginosa. The in-vitro activities of E1040 against clinical isolates of Enterobacter cloacae, Ent. aerogenes, Providencia rettgeri, and Morganella morganii were superior to those of ceftazidime, cefoperazone, cefmenoxime, and cefuzonam. The activities of E1040 against Gram-positive cocci were comparable with those of ceftazidime, but it was less active than cefmenoxime, cefuzonam, and cefoperazone. Against Ps. aeruginosa, E1040 was more potent than the other compounds, with an MIC90 of 0.39 mg/l, 1/16 that of ceftazidime. The in-vitro activity of E1040 was well sustained in vivo as shown by results obtained in experimental infections in mice. In particular, E1040 was the most active drug against Ps. aeruginosa including gentamicin-resistant and beta-lactamase-overproducing strains. Morphological studies using a scanning electron microscope and a phase-contrast microscope showed that E1040 caused spheroplast and bulge formation in Ps. aeruginosa at low concentrations.
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