Oral absorption of cephalosporin antibiotics. 2. Expanded structure-activity relationships of 7-(arylacetamido)-3-substituted cephalosporins.

The structure-activity relationship for 7-arylacetamido cephalosporins has been extended. Modifications of the 7-aryl group led to improvements in microbiological activity against Gram-positive organisms. However, Gram-negative activity was generally much poorer than that of the lead compound 7-[(2-aminothiazol-4-yl)acetamido]-3-chloro-cephalosporanic acid (A). Modifications of the 3-position did not significantly change the microbiological activity or spectrum. Of the compounds selected for mouse protection studies (ED50's), 7-[(benzothien-3-yl)acetamido]-3-chloro cephalosporin and A showed the best per oral to subcutaneous ED50 ratios.

Orally absorbable cephalosporin antibiotics. 2. Structure-activity studies of bicyclic glycine derivatives of 7-aminodeacetoxycephalosporanic acid.

Three positional analogues (4-, 5-, and 7-) of benzothienylglycine and (N-acetylindolinyl)-5-glycine were prepared and coupled to 7-aminodeacetoxycephalosporanic acid (7-ADCA) to give the cephalosporins 17a-c. In addition two isomeric (2,3-b and 3,2-b) thienothiopheneglycines were synthesized and coupled to 7-ADCA to yield cephalosporins 30d and 30e. In vitro testing of these new cephalosporins indicates good activity against Gram-positive bacteria. Against Streptococcus pneumoniae infections compound 25 displayed better mouse protection (both orally and subcutaneously) than cephalexin.

Structure-activity relationship within a series of pyrazolidinone antibacterial agents. 2. Effect of side-chain modification on in vitro activity and pharmacokinetic parameters.

The structure-activity relationship among a series of novel pyrazolidinone antibacterial agents is described. Specifically, the effect of modification of the side chain attached to the nitrogen at C-7 was explored in an attempt to improve the potency and spectrum of activity. This approach was successful in identifying several compounds having good in vitro profiles. These top candidates were then evaluated for their activity in vivo, and their pharmacokinetic behavior in various animal models was explored. This information proved critical for the identification of candidates for clinical evaluation.

Synthesis and biological evaluation of a series of parenteral 3'-quaternary ammonium cephalosporins.

The preparation and biological evaluation of a series of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoximinoacetamido]cep halosporins, substituted at the 3'-position with monocyclic or bicyclic nitrogen-containing heterocycles are described. The resulting family of parenteral compounds displays a broad spectrum of antibacterial activity. Some compounds exhibit a similar level of Gram-negative activity to that of the "third-generation" cephalosporins with increased staphylococcal activity. The in vitro and in vivo antimicrobial activity, structure-activity relationships, beta-lactamase stability, and in vitro and in vivo pharmacological evaluations are presented.

Synthesis and evaluation of tylosin-related macrolides modified at the aldehyde function: a new series of orally effective antibiotics.

Modification of the aldehyde group in tylosin and related macrolide antibiotics dramatically enhanced the oral efficacy of the derivatives against experimental infections caused by susceptible bacteria in laboratory animals. A large number and wide variety of aldehyde-modified macrolide derivatives were prepared, utilizing the Mitsunobu reaction and other chemical transformations. Evaluation of in vitro and in vivo antimicrobial activity indicated that derivatives of demycarosyltylosin (desmycosin) combined the broadest spectrum of antimicrobial activity with the best efficacy and bioavailability after oral administration.

Oral absorption of cephalosporin antibiotics. 1. Synthesis, biological properties, and oral bioavailability of 7-(arylacetamido)-3-chloro cephalosporins in animals.

A number of 7-(arylacetamido)-3-substituted cephalosporins were prepared and tested in animals for oral absorbability. Bioavailability in mice, rats, dogs, and monkeys was determined after oral or parenteral administration. Oral bioavailability of five compounds selected for more intensive study was generally higher than that of penicillin V in all species tested. The results of ED50 testing against experimental infections in mice generally supported the bioavailability studies. Antibiotic activities were evaluated against Gram-positive and Gram-negative organisms with some derivatives expressing in vitro activity similar to cefaclor. The plasma half-life in rats was relatively short and the plasma curves were strongly influenced by probenecid, indicating rapid renal secretion. Some 7-(arylacetamido)-3-chloro cephalosporins are orally absorbed in animals to a greater extent than penicillin V, and antibacterial agent of proven clinical utility.

Synthesis and in vitro antibacterial activities of 3-thiazol-4-yl-1-carba-1-dethiacephalosporins.

The synthesis and microbiological evaluation of a new series of 3-thiazol-4-yl-carba-1-dethiacephalosporins is described. Structure activity relationship was achieved by changing substitution at the 2-position of the thiazole moiety. The result was a marked variance of microbiological activity in the C7 side-chain derivatives. ATMO derivatives possess potent activity against both Gram-positive and Gram-negative bacteria. For example, MICs (microgram/ml) of LY215226 against representative organisms are as follows: S. aureus 0.25, S. pneumoniae 0.008, H. influenzae 0.008, E. coli 0.25, K. pneumoniae 0.008, E. cloacae 0.5, S. typhi 0.25, and M. morganii 0.25.

Synthesis and antibacterial activity of N-acyl vancomycins.

Several glycopeptides containing N-acyl groups have been isolated recently. We undertook the synthesis of N-acyl vancomycins, using the active ester method. The in vitro and in vivo antibacterial activity were evaluated, and structure-activity relationship of this series of semisynthetic vancomycins is discussed.

Synthesis and antibacterial evaluation of N-alkyl vancomycins.

Over eighty N-alkyl vancomycins were synthesized by reductive alkylation of vancomycin with the appropriate aldehydes. The N-alkyl vancomycins exhibit greater antibacterial activity than the corresponding N-acyl vancomycins and the parent antibiotic. Some of these semisynthetic vancomycins are five times more active than vancomycin. The N-alkyl vancomycins also show longer elimination half-lives in rats than vancomycin.

Synthesis and characterization of a novel inhibitor of an aminoglycoside-inactivating enzyme.

A novel low-molecular weight inhibitor of an aminoglycoside-inactivating enzyme, initially isolated from fermentation broths of Streptomyces neyagawaensis, was determined to be 7-hydroxytropolone. Its structure was confirmed by synthesis. In vitro synergy was demonstrated between 7-hydroxytropolone and certain aminoglycosides against bacteria which were resistant to those aminoglycosides by virtue of a 2"-O-adenylyltransferase. The synthesis and characterization of some analogs of 7-hydroxytropolone is also described.

Structure-activity studies among 16-membered macrolide antibiotics related to tylosin.

Although a substantial number of 16-membered macrolides related to tylosin have now been isolated and evaluated as antibiotics, none appeared to be superior to tylosin in treating bacterial or mycoplasmal infections caused by sensitive organisms. Nevertheless, this comparison of the antibiotic activity of 16-membered macrolides clearly indicates that novel antibiotics with potentially useful activity can be obtained from mutant strains which have been blocked at various steps in their biosynthesis of antimicrobial agents. The novel compounds thus produced may also be used as starting materials for additional chemical and microbiological modification. Furthermore, the mutant strains which produced these novel compounds should be useful recipients for interspecific genetic recombination by protoplast fusion or gene cloning to yield hybrid antibiotics. Even greater exploitation of these methods will be required in the continuing search for new antibiotics and improved methods for producing them.

Synthesis and antimicrobial evaluation of 20-deoxo-20-(3,5-dimethylpiperidin-1-yl)desmycosin (tilmicosin, EL-870) and related cyclic amino derivatives.

A series of 20-deoxo-20-cyclic (alkylamino) derivatives of tylosin, desmycosin, macrocin and lactenocin was prepared by reductive amination of the C-20 aldehyde group. The majority of the compounds were prepared using metal hydrides (sodium cyanoborohydride or sodium borohydride) as the reducing agents and a suitable cyclic alkylamine. Subsequently, a more convenient procedure was developed using formic acid as a reducing agent. The C-20 amino derivatives prepared from desmycosin exhibited good in vitro antimicrobial activity against Pasteurella haemolytica and Pasteurella multocida (MIC range of 0.78 approximately 6.25 micrograms/ml) as well as Mycoplasma species (MIC range of 0.39 approximately 6.25 micrograms/ml). Several derivatives showed excellent oral efficacy against infections caused by P. multocida in chicks. One of these derivatives, 20-deoxo-20-(3,5-dimethylpiperidin-1-yl)desmycosin (tilmicosin or EL-870) was selected for development as a therapeutic agent for pasteurellosis in calves and pigs.

Synthesis, antimicrobial evaluation and structure-activity relationships within 23-modified derivatives of 5-O-mycaminosyltylonolide.

A large series of C-23-modified derivatives of 5-O-mycaminosyltylonolide were synthesized, in which the C-23 hydroxyl group was replaced by halo, aryl ether or thioether, azido, amino or dialkylamino substituents via SN2 displacement reactions. The majority of derivatives possessed excellent in vitro activity against a variety of aerobic and anaerobic bacteria. While some of the compounds treated experimental infections in rodents by parenteral administration, none showed any significant efficacy or bioavailability after oral dosing. Novel rearrangement products were obtained from some of the reactions; these were identified as 13,23-cyclopropyl-12,22-exomethylene and 13,23-cyclopropyl-12-alkoxy derivatives.

Enzymatic and chemical modifications of lipopeptide antibiotic A21978C: the synthesis and evaluation of daptomycin (LY146032).

The novel lipopeptide antibiotic A21978C complex is active against Gram-positive organisms. This complex consists of a common peptide nucleus with various lipid acyl groups at the N-terminus characteristic of each individual factor. The fatty acid acyl group is removed by incubation of the A21978C complex with Actinoplanes utahensis to give the peptide nucleus. This peptide nucleus has the same amino acid sequence as A21978C. New analogs of A21978C were synthesized by acylation of the N-terminus of a tert-butoxycarbonyl (tert-BOC)-protected nucleus and subsequent deprotection. 1H NMR showed that the newly introduced acyl group was at the desired N-terminus. Three major groups of analogs were synthesized bearing fatty acid acyl, amino-aroyl and extended peptide side chains. Each analog was evaluated for antimicrobial activity and acute toxicity. Of these analogs, the n-decanoyl analog of A21978C (LY146032) gave the best survival in the mouse acute toxicity test at a high dose of 1,000 mg/kg, iv and was chosen for further study. This analog has been named daptomycin.

Synthesis and antimicrobial evaluation of acyl derivatives of 16-membered macrolide antibiotics related to tylosin.

A large number and wide variety of acyl derivatives of the tylosin-related macrolides 23-demycinosyltylosin (DMT), 23-demycinosyloxytylosin (DMOT) and 5-O-mycaminosyltylonolide (OMT) were synthesized and evaluated. This encompassed conversion of the hydroxyl groups at 2',4' and 23 of the appropriate macrolides to the corresponding esters, in which a variety of different substitution patterns were examined. A wide range of acyl substituents was investigated, particularly for 23-O-acyl derivatives of OMT, since these were substantially more active in vitro than OMT itself. However, the acyl derivatives which were prepared demonstrated no substantial improvement in oral efficacy or bioavailability over the parent macrolides.

Structure-activity studies of 20-deoxo-20-amino derivatives of tylosin-related macrolides.

Reductive amination of the C-20 aldehyde group of tylosin and related macrolides yielded a large series of derivatives with potentially useful antibiotic properties. Evaluation of these new compounds was conducted on the basis of: 1) Broad antimicrobial spectrum in vitro, with particular emphasis on inhibition of Pasteurella multocida and Pasteurella haemolytica; 2) in vivo efficacy, especially when given orally, against P. multocida in experimental infections in chicks; and 3) bioavailability after oral administration to laboratory animals. The most useful activity was found within a series of derivatives produced by reductive amination of desmycosin with secondary amines.

A54145 a new lipopeptide antibiotic complex: microbiological evaluation.

A54145 complex is made up of eight factors; A, A1, B, B1, C, D, E, and F which were active in vitro (MIC 0.25 approximately greater than 32 micrograms/ml) against Gram-positive aerobic organisms. The complex, factor B and B1 were found to be active against two strains of Clostridium perfringens. A calcium dependence study on some of the factors showed that their in vitro antibacterial activity was greatly enhanced by the presence of calcium (50 mg/liter) in the media. Resistance build-up was seen when Staphylococcus sp. and Streptococcus sp. were passed seven times in the presence of sublethal concentrations of A54145 antibiotics. This resistance disappeared immediately when the resistant organisms were passed in the absence of the antibiotics. Factor A was very effective against Staphylococcus aureus and Streptococcus pyogenes infections in mice (sc ED50s of 3.3 approximately 2.4 mg/kg x 2, respectively). Factor B was more active against S. pyogenes in vivo (sc ED50, 0.9 mg/kg x 2). Acute mouse toxicities were determined with these antibiotics. Semisynthetic derivatives were evaluated.

Erysipelas serum titration with sheep red blood cells passively sensitized with a cellular extract.

We have demonstrated that sheep red blood cells can be passively sensitized with an extract from Erysipelothrix rhusiopathiae. Diagnostic differential hemagglutination titrations may then be made with porcine serum for Erysipelas antibody.

Hemagglutination inhibition of passively sensitized red blood cells.

It has been shown that sheep red blood cells sensitized with the polysaccharides of Haemophilus influenzae type B and pneumococcal types I, III, IV, VII, VIII, XII, and XIV respond readily in hemagglutination-inhibition testing and exhibit antigen inhibition at levels of 0.09 to 4.0 ng.