Reduced immunotoxicity and preservation of antibacterial activity in a releasable side-chain carbapenem antibiotic

Copper-catalyzed peri-selective direct sulfenylation of 1-naphthylamines with disulfides

A copper-catalyzed peri-selective direct C–H sulfenylation of 1-naphthylamines with disulfides was developed.

Cobalt(ii)-catalyzed remote C5-selective C–H sulfonylation of quinolines via insertion of sulfur dioxide

A cobalt(ii)-catalyzed reaction for highly selective C5-sulfonylation of quinolines via insertion of sulfur dioxide is developed, leading to diverse sulfonated quinolines in moderate to good yields.

Copper(ii)-catalyzed remote sulfonylation of aminoquinolines with sodium sulfinates via radical coupling

Many various aminoquinolines-derived sulfones were obtained in moderate to high yields via copper(ii)-catalyzed direct C(sp²)–H sulfonylation of aminoquinolines with sodium sulfinates.

A panel of urinary biomarkers to monitor reversibility of renal injury and a serum marker with improved potential to assess renal function

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Exploring the chemistry of penicillin as a β-lactamase-dependent prodrug

The penam nucleus can be modified to behave as a beta-lactamase-dependent 'prodrug' by incorporation of a vinyl ester side chain at the 6-position. Enzyme-catalysed hydrolysis of the beta-lactam ring uncovers the thiazolidine-ring nitrogen as a nucleophile that drives a rapid intramolecular displacement on the side chain. Attachment of 7-hydroxy-4-methylcoumarin as the releasable group of this side chain generated a penicillin structure that can function as a fluorescence-based reporter substance/diagnostic for the presence of low levels of beta-lactamase enzyme in solution. Mechanistic details of the reaction pattern are documented and the scope and limitations of exploiting the structural modification are discussed.

Elucidating mechanisms of drug-induced toxicity

The early and high-throughput application of assays for non-genetic toxicity is of great interest to the pharmaceutical industry, although few systems have been validated as being of good predictive value. New technologies could enable toxicity to be studied in the context of systems biology. An important factor to be considered is the metabolism of drugs to reactive intermediates. Chemical reactions of these with cell and tissue nucleophiles are relatively well understood, but predicting how biological modifications will affect signalling and regulatory networks remains a challenge. Some of these pathways could be useful as sentinels for toxicity. This article will cover some examples of drug toxicity and the prospects for future technology development.

Novel structures derived from 2-[[(2-pyridyl)methyl]thio]-1H-benzimidazole as anti-Helicobacter pylori agents, Part 1

2-[[(2-Pyridyl)methyl]thio]-1H-benzimidazoles (2, sulfides) exhibit antibacterial properties that are selective for Helicobacter spp., but they also have an inherent susceptibility to metabolic oxidation to furnish 2-[[(2-pyridyl)methyl]sulfinyl]-1H-benzimidazoles (1), which act as proton pump inhibitors (PPIs). We have discovered five compounds with retained antibacterial potency and selectivity in which the overall framework of the sulfides 2 could be kept intact while structural modifications were made to remove PPI activity. These compounds, 2-[((2-methyl-3-(2-(2-(2-methoxyethoxy)ethoxy)ethylthio)phenyl)methyl)thio]-1H-benzimidazole (79), 2-[((2-methyl-3-(2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethoxy)ethylthio)phenyl)methyl)thio]-1H-benzimidazole (80), 2-[((2-methyl-3-((2-morpholino)ethylthio)phenyl)methyl)thio]-1H-benzimidazole (86), 2-[[[2-methyl-3-[2-(2-methyl-5-nitroimidazol-1-yl)ethylthio]phenyl]methyl]thio]-1H-benzimidazole (88), and 2-[[[2-methyl-3-[2-(1,2,4-triazol-1-yl)ethylthio]phenyl]methyl]thio]-1H-benzimidazole (89), had minimum bactericidal concentrations (MBCs) of 0.5, 0.5, 1, 2, and 4 microg/mL, respectively. The reported compounds are bactericidal with MBCs within 1 order of magnitude of MBCs of clinically used antimicrobials such as clarithromycin (0.1 microg/mL) or metronidazole (2-4 microg/mL) but differ from these inasmuch that they have an extremely narrow spectrum activity and appear to be species specific.

Identification by LC/MS(n) of degradates of a novel carbapenem antibiotic in an aqueous matrix

Increased drug resistance in Staphylcocci and Enterococci to currently available antibiotics has significantly limited therapeutic options. Recently, a novel carbapenem antibiotic (Compound A) with a releasable side chain adjacent to the carbapenem was investigated to combat methicillin- and vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci. The major advantage of Compound A over existing antibiotics can be attributed to the fact that cleavage of the side chain upon beta-lactam ring opening retained anti-bacterial activity while expelling the immunodominant epitope of the presumed beta-lactam hapten. In this work, LC/MS methods were developed to identify degradates of Compound A in an aqueous matrix utilized in assessing product safety and supporting analytical method and formulation development. A total of eight significant degradates were observed in this Compound A sample by LC/MS(n) and other techniques. Detailed structural analysis of degradates based upon LC/MS(n) data and other supporting results will be described in this work. Proposed molecular structures were confirmed by synthesis and use of authentic standards for several degradates. Degradates 1 and 4 were identified as degradates formed through the reversal of Michael reaction from Degradate 3 that is apparently formed by hydrolysis. Degradates 2 and 8 were found to be Hofmann elimination degradates. Degradates 5 and 6 are believed to be formed through dimerization of two parent molecules followed by the reversal of Michael reaction. Finally, Degradate 7 is attributed to a displacement reaction. Potential degradation pathways based upon these preliminary studies will also be discussed.

Direct-injection HPLC assay for the determination of a new carbapenem antibiotic in human plasma and urine

Reversed-phase high-performance liquid chromatography (RP-HPLC) assays using ultraviolet (UV) absorbance detection have been developed for the determination of a new carbapenem antibiotic I in human plasma and urine. A column-switching technique is employed in the HPLC methods to perform on-line extraction and separation for each sample. Each plasma sample is thawed, centrifuged, stabilized, and then injected onto an in-line reversed-phase extraction column using a methanol (8%)/phosphate buffer, pH 6.5. After 3 min, the analytes are back-flushed off the extraction column with a mixture of acetonitrile (5.5%) and methanol (10%)/phosphate buffer (pH 6.5) for 3 min onto a BDS Hypersil 3 microm C18 (100 x 4.6 mm i.d.) analytical column. The sample preparation and HPLC conditions for the urine assay are similar to the plasma assay, except that a CN extraction column is used. Both assays are specific with respect to endogenous material and the major metabolite II, and both are linear over the concentration range of 0.25-50, and 2-200 microg/ml, respectively. The assays were successfully applied to a clinical dose-ranging study. One limitation of the on-line extraction method is that the extraction column needs to be replaced regularly every 100-150 plasma samples and every 200-300 urine samples. Subsequently, the urine method was modified to an ion-pair HPLC assay for the simultaneous determination of both the antibiotic I and its metabolite II.

Synthesis of an anti-methicillin-resistant Staphylococcus aureus (MRSA) carbapenem via stannatrane-mediated Stille coupling

[formula: see text] A short synthesis of carbapenem 1 is described. They key step involves the cross-coupling of an enol triflate with an amino-substituted sp3 carbon. This cross-couping, which allows the introduction of the complete side chain in one step, utilizes a stannatrane as the heteroalkyl transfer reagent.

Dicationic 2-fluorenonylcarbapenems: potent anti-MRS agents with improved solubility and pharmacokinetic properties

The synthesis and biological evaluation of a series of dicationic-substituted 2-fluorenonylcarbapenems is described. This class of compounds showed enhanced water solubility while maintaining potent activity against MRS. Introduction of a 1-beta-methyl substituent was found to improve pharmacokinetics.

What's new in the antibiotic pipeline

Many advances have recently been made in the development of chemotherapeutic agents for bacterial infections. As a consequence of problematic antimicrobial-resistant bacteria, research is now directed towards narrow-spectrum agents rather than broad-spectrum agents. Further, orally active agents have always been desirable, but today's cost-saving environment, in line with a desire to minimize treatment costs, values reduced administration costs and keeping patients out of the hospital. There has been a recent increase in research into orally active antibacterial agents, such as carbapenems and cephalosporins, and non-glycopeptide natural products.

Synthesis and properties of 2-(naphthosultamyl)methyl-carbapenems with potent anti-MRSA activity: discovery of L-786,392

A series of 1beta-methyl-2-(naphthosultamyl)methyl-carbapenems bearing dicationic groups on the naphthosultamyl moiety was prepared and evaluated for activity against resistant gram-positive bacteria. Based on a combination of excellent in vitro antibacterial activity, acceptable mouse acute toxicity, and a desirable fragmentation pattern on beta-lactam ring opening, the analog 2g (L-786,392) was selected for extended evaluation.