Synthesis and biological activity of 5-alkyl-1,7,8-trisubstituted-6-fluoroquinoline-3-carboxylic acids.

A series of 5-alkyl-1,7,8-trisubstituted-6-fluoro-1,4-dihydro-4-oxo-3- quinolinecarboxylic acids was prepared and evaluated for in vitro and in vivo antibacterial activity. When compared to the 5-hydrogen analogues, the presence of the 5-methyl group enhanced in vitro potency for those compounds containing a cyclopropyl moiety at N1 but decreased potency for those containing an ethyl group at N1. Replacing the 5-methyl with a 5-ethyl significantly reduced the efficacy. In general, the 5-methyl and 5-hydrogen analogues were equipotent in vivo. Several of the 5-methyl-1-cyclopropylquinolones displayed excellent in vitro and in vivo activity, warranting further development.

New quinolone antibacterial agents. Synthesis and biological activity of 7-(3,3- or 3,4-disubstituted-1-pyrrolidinyl)quinoline-3-carboxylic acids.

A series of 7-(3-amino- or 3-aminomethyl-1-pyrrolidinyl)-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-o xo-3-quinolinecarboxylic acids was synthesized and tested for antibacterial activity. Unique to these quinolones was the presence of a methyl or phenyl group in the pyrrolidine ring. Although the in vitro activity of these agents was usually equal to or less than that of their unsubstituted counterparts, one quinolone, 7-[3-(aminomethyl)-3-methyl-1-pyrrolidinyl]-1-cyclopropyl-6,8-difluoro-1 ,4-dihydro-4-oxo-3-quinolinecarboxylic acid, displayed exceptional potency both in vitro and in vivo, particularly against Gram-positive organisms.

Quinolone antibacterial agents. Synthesis and structure-activity relationships of 8-substituted quinoline-3-carboxylic acids and 1,8-naphthyridine-3-carboxylic acids.

A series of 7,8-disubstituted 1-cyclopropyl-6-fluoroquinoline-3-carboxylic acids, 7-substituted 1-cyclopropyl-6-fluoro-1,8-naphthyridine-3-carboxylic acids, and 10-substituted 9-fluoropyridobenzoxazine-6-carboxylic acids has been prepared and evaluated for antibacterial activity. The side chains examined at the 7-position (benzoxazine 10-position) included piperazinyl (g), 3-aminopyrrolidinyl (a), 3-(aminomethyl)pyrrolidinyl (b), and alkylated 3-(aminomethyl)pyrrolidinyl (c-f). Variations at C-8 of the quinolone ring system included hydrogen, nitro, amino, fluorine, and chlorine. The relative enhancement of in vitro activities by the side chains on the 8-hydrogen quinolone and 1,8-naphthyridine against Gram-negative organisms was a greater than b greater than g greater than c-f. The activity imparted to the substituted quinolone nucleus by the 8-substituent was in the order F greater than Cl greater than naphthyridine greater than H greater than benzoxazine greater than NH2 greater than NO2. These trends were retained in vivo.

New structure-activity relationships of the quinolone antibacterials using the target enzyme. The development and application of a DNA gyrase assay.

A series of 60 newly synthesized and known quinolone antibacterials, including quinoline- and 1,8-naphthyridine-3-carboxylic acids, pyrido[2,3-d]pyrimidine-6-carboxylic acids, and some monocyclic 4-pyridone-3-carboxylic acids, were tested and compared in a newly established, easy to perform, DNA gyrase assay. The results were correlated with minimum inhibitory concentrations (MICs) against a variety of organisms. Among the known quinolones were 14 clinically significant drugs (oxolinic acid, norfloxacin, ciprofloxacin, enoxacin, etc.) which were used as standards and compared side-by-side. The study focused on the changes in DNA gyrase inhibition brought about by certain features of the molecules, namely, the C6-fluorine or the nature of the C7 substituent. The intrinsic gyrase inhibition of the fused parent rings, quinoline vs. naphthyridine vs. pyrido[2,3-d]pyrimidine, was also explored. In all cases, loss of enzyme inhibition produced poor MICs, but some compounds with good DNA gyrase inhibition did not correspondingly inhibit bacterial growth. Possible explanations for this phenomena and the benefits of a DNA gyrase-MIC strategy for developing future structure-activity relationships are discussed.

1-Substituted 7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6,8- difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acids. New quantitative structure-activity relationships at N1 for the quinolone antibacterials.

A series of 18 1-substituted 7-[3-[(ethylamino)methyl]-1- pyrrolidinyl]-6,8-difluoro-1,4-dihydro-4-oxo-3-quinoline- carboxylic acids (N1 analogues of CI-934) were synthesized and evaluated for antibacterial activity and DNA-gyrase inhibition. Correlations between the inhibition of DNA gyrase and antibacterial potency were established. A quantitative structure-activity relationship (QSAR) was derived by using the antibacterial potency for each of 11 strains of bacteria and the Gram-negative mean. The equations indicated that antibacterial potency was strongly dependent on STERIMOL length and width and the level of unsaturation of the N1 substituent. Some strains also showed a dependence on the presence of heteroatoms (O, N, S) in the N1 group. No significant correlations between gyrase inhibition and combinations of these parameters were found. These QSAR results are discussed in conjunction with the conformational analyses from molecular modeling studies. The substituent that most enhanced the activity of the quinolone in all regards was the cyclopropyl group. This analogue, 1-cyclopropyl-7-[3-[(ethylamino)-methyl]-1-pyrrolidinyl]-6, 8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (PD 117558), demonstrated outstanding broad spectrum activity both in vitro and in vivo when compared to relevant standards.

Quinolone antibacterial agents. Synthesis and structure-activity relationships of a series of amino acid prodrugs of racemic and chiral 7-(3-amino-1-pyrrolidinyl)quinolones. Highly soluble quinolone prodrugs with in vivo pseudomonas activity.

A series of amino acid prodrugs of racemic and chiral 7-(3-amino-1-pyrrolidinyl)-6-fluoro-1,8-naphthyridine-3-carboxylic acids, 1-cyclopropyl-6,8-difluoro-3-quinolinecarboxylic acids, 1-cyclopropyl-6-fluoro-3-quinolinecarboxylic acids, and 5-amino-1-cyclopropyl-6,8-difluoro-3-quinolinecarboxylic acids have been prepared and evaluated for comparative antibacterial activity. Compounds were prepared by acylation of the 3-amino group of the pyrrolidine with common amino acids using standard peptide chemistry. This series has been compared with the parent compounds for antibacterial activity in vitro and in vivo as well as for comparative solubility. The amino acid analogues were less active in vitro, but had equal or increased efficacy in vivo. Indeed, it was proven that these compounds, which were stable to acid and base under the reaction conditions for their preparation, were rapidly cleaved in serum to give the parent quinolones. The amino acid derivatives showed a 3-70 times improved solubility when compared to the parent compounds. The most active compound of the series was [S-(R*,R*)]-7-[3-[(2-amino-1-oxopropyl)-amino]-1-pyrrolidinyl]-1- cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid (PD 131112).

New 8-(trifluoromethyl)-substituted quinolones. The benefits of the 8-fluoro group with reduced phototoxic risk.

A series of 8-(trifluoromethyl)-substituted quinolones has been prepared and evaluated for in vitro and in vivo antibacterial activity, and phototolerance in a mouse phototolerance assay. These analogues were compared to the corresponding series of 6,8-difluoro- and 6-fluoro-8H-quinolones (ciprofloxacin type). Although their in vitro antibacterial activities are less than the 6,8-difluoro analogues, the 8-(trifluoromethyl)quinolones are generally equivalent to their 8H analogues. In vivo, they are comparable to the 6,8-difluoro series and show up to 10-fold improvement in efficacy when compared to their ciprofloxacin counterparts vs Streptococcus pyogenes and Streptococcus pneumonia. In the phototolerance model, the 8-(trifluoromethyl)quinolones are comparable to the 8H-quinolones. Both of these series display much higher no effect doses (greater tolerance) than the corresponding 6,8-difluoroquinolones.

Treatment of experimental Pseudomonas corneal ulcers with enoxacin, a quinolone antibiotic.

Enoxacin is a broad-spectrum quinolone-derivative antibiotic. In a rabbit model of keratitis caused by a Pseudomonas species, enoxacin (3 mg/mL) was as effective as gentamicin sulfate (3 mg/mL) and enoxacin (10 mg/mL) in reducing viable bacterial counts in corneas after 24 hours of hourly therapy with eye drops. Bacterial counts were reduced by about 5000-fold by enoxacin treatment when compared with placebo-treated controls. Penetration studies of topical enoxacin (3 mg/mL) showed that concentrations in cornea and aqueous humor reached levels above reported minimal inhibitory concentrations when an epithelial defect was present. Further investigation of enoxacin for treatment of ocular disease is warranted.

In vitro activity of sparfloxacin (CI-978, AT-4140, and PD 131501). A quinolone with high activity against gram-positive bacteria.

Sparfloxacin (CI-978, AT-4140 and PD 131501) is a new antimicrobial agent of the piperazinyl quinolone class. Relative to other quinolones, it is a potent antistaphylococcal and antistreptococcal drug in vitro: The microbroth 90% minimum inhibitory concentration (MIC90) (in microgram/ml) was 0.25 vs 26 methicillin-resistant and -sensitive coagulase-positive and -negative staphylococci and 20 Streptococcus pneumoniae; 0.5 vs 20 strains each of S. pyogenes, S. agalactiae, and Enterococcus faecalis. The data indicate sparfloxacin to be generally superior to ciprofloxacin, ofloxacin, oxacillin, cefazolin, doxycycline, amikacin, and vancomycin against these Gram-positive bacterial groups. Additional MIC90s were determined for Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and Neisseria gonorrhoeae (less than or equal to 0.03); Enterobacteriaceae (0.5); and Listeria monocytogenes (1). Activity was generally unchanged with light, 50% human serum, aerobic-anaerobic atmosphere, 5% sodium cholate, cation supplementation, and 100-fold increased or decreased inoculum; as with other quinolones, potency was measurably diminished with decreasing pH (pH less than or equal to 6.0) and in 100% urine. Naturally occurring resistant mutants occurred at frequencies of 10(-8) or lower.

In vitro evaluation of cefdinir (FK482), a new oral cephalosporin with enhanced antistaphylococcal activity and beta-lactamase stability.

Cefdinir (FK482), a new oral cephalosporin with enhanced beta-lactamase stability, was tested by microbroth dilution against respiratory, urogenital, and skin and skin-structure bacterial pathogens. Included were beta-lactamase (beta LAC)-producing and -nonproducing isolates. Activity was compared with that of other orally administered beta-lactams. Cefdinir minimum inhibitory concentrations for 90% of isolates MIC90s (microgram/ml) were < or = 0.5 versus beta LAC+/oxacillin-susceptible Staphylococcus, aureus, S. epidermidis, and S. saprophyticus; < or = 0.06 versus Streptococcus groups A and B, and Neisseria gonorrhoeae beta LAC+; 0.125 versus S. pneumoniae penicillin-susceptible and Proteus mirabilis beta LAC+; 0.25 versus beta LAC+ versus strains of Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and K. oxytoca; 0.5 versus Haemophilus influenzae beta LAC-; 1 versus H. influenzae beta LAC+; 4 versus Legionella pneumophila beta LAC+; and 8 versus Enterococcus faecalis beta LAC-strains. Cefdinir was equally effective against both standard and high inocula of S. aureus strains producing A, B, C, or D beta LAC types. MICs were also generated versus quality-control reference strains.

In vivo therapeutic efficacy of cefdinir (FK482), a new oral cephalosporin, against Staphylococcus aureus and Haemophilus influenzae in mouse infection models.

Cefdinir (FK482), a new oral cephalosporin, displayed potent oral activity versus induced infections in mice. In studies using beta-lactamase-nonproducing (beta LAC-) and -producing (beta LAC+) Staphylococcus aureus strains, respective PD50s (in mg/kg) were 11 and 24 for preventing subcutaneous abscess and 2.7 and 2.3 for preventing lethal systemic infection. In studies using beta LAC- and beta LAC+ Haemophilus influenzae, respective PD50s were 5.8 and 3.1 for preventing lethal systemic infection. Time-kill studies versus H. influenzae showed that 6- to 12-mg/kg dosing was effective in reducing viable counts of these strains in blood by > or = 100-fold by 24 h after challenge. This in vivo performance was comparable to or exceeded values generated by cefaclor, cefpodoxime proxetil, and ampicillin.

In vitro antibacterial activities of the fluoroquinolones PD 117596, PD 124816, and PD 127391.

Three new aminopyrrolidine-substituted fluorocyclopropyl quinolones--PD 117596, PD 124816, and PD 127391--were tested for in vitro antibacterial activity against 349 bacterial strains, which are primarily clinical isolates. The minimum inhibitory concentrations (MIC) in micrograms/ml required for greater than or equal to 90% of strains were 0.03-0.06 for staphylococci (26 strains); 0.06-0.25 for Streptococcus pyogenes, S. agalactiae, S. pneumoniae, and Enterococcus faecalis (80); less than or equal to 0.015 for Branhamella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae (42); 0.06 for Enterobacteriaceae (97); 0.125-0.25 for Acinetobacter spp. (14); 0.5 for Pseudomonas aeruginosa (20); 0.125-1.0 for Bacteroides fragilis (13); and 0.25-0.5 for anaerobic cocci (11). These activities were generally superior to that of ciprofloxacin, imipenem, ampicillin, penicillin G, oxacillin, cefazolin, ceftazidime, cefoxitin, cefsulodin, aztreonam, piperacillin, amikacin, spectinomycin, doxycycline, erythomycin, clindamycin, metronidazole, and vancomycin. The activities of the new quinolones were generally unchanged with light, 50% human serum, aerobic/anaerobic atmosphere, 5% sodium choate, cation supplementation, and 100-fold increased or decreased inoculum; as with other quinolones, potency was measurably diminished with decreasing pH (pH less than or equal to 6.0) and in 100% urine.

A novel rapid throughput phototolerance screen in mice.

A relatively simple, rapid throughput phototolerance screen in small animals would be very useful in early drug development. It could prioritize or select potential lead compounds from among a number of analogs with similar biological activities. This study describes an in vivo mouse phototolerance screen established for that purpose. It also reports phototolerance data with standard reference drugs obtained using this screen.

CI-867, a new broad-spectrum semisynthetic penicillin.

The synthesis and antimicrobial activity of a new semisynthetic penicillin are described. Both in vitro and in vivo, the compound shows promising antibacterial activity when compared with piperacillin and ticarcillin. High activity is shown against Pseudomonas and other Gram-negative bacteria.

Semisynthetic penicillins and cephalosporins containing the substituted 6-vinyl-1,2-dihydro-2-oxo- and 1,4-dihydro-4-oxo-3-pyridinecarboxylic acid side chains. Synthesis and structure-activity relationships.

A series of penicillins and cephalosporins containing the substituted 6-vinyl-1,2-dihydro-2-oxo- and 1,4-dihydro-4-oxo-3-pyridinecarboxylic acid side chains has been prepared and compared to piperacillin and cefoperazone. The compounds show good activity when tested in vitro against an array of Gram-negative bacteria. In vitro activity was also demonstrated against several species of Gram-positive bacteria. Two compounds, 14 and 21, show good in vivo activity when tested against Klebsiella pneumoniae, Enterobacter cloacae, and two strains of Pseudomonas aeruginosa.

Semisynthetic penicillins. A structure - activity study of a new series of acyl amino acid - pyridone and pyrimidone amoxicillin analogs.

The synthesis and biological activities of a series of 12 new semisynthetic penicillins is described. These compounds consisted of acylated amino acid analogs of 6-substituted-1,2-dihydro-2-oxonicotinic acid and 2-substituted-3,4-dihydro-4-oxo-5-pyrimidinecarboxylic acid attached to amoxicillin. The effect of the amino acid substituent, chirality of amino acid and acyl function on biological properties is discussed.

Synthesis and biological activity of a new semisynthetic cephalosporin, CN-92,982.

A new broad spectrum semisynthetic cephalosporin (CN-92,982) was prepared from the condensation of an acetylaminoacylaminophenyl pyridone with trans-7-[(D-2-phenylglycyl) amino]-3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-delta 3-cephem-4-carboxylic acid. The new cephalosporin displayed an in vitro antibacterial spectrum similar to other cephaloglycine types such as cefoperazone and SM-1652. The compound produced a high and prolonged blood level following a single intramuscular dose in a dog.

Phenazopyridine-sulfonamide combination antibacterial therapy in mice.

Phenazopyridine, at its maximum tolerated dose, did not affect the effectiveness of sulfonamides against uropathogenic bacterial species in mice.