Anil Srivastava

Creating an antibacterial with in vivo efficacy: synthesis and characterization of potent inhibitors of the bacterial cell division protein FtsZ with improved pharmaceutical properties.

3-Methoxybenzamide (1) is a weak inhibitor of the essential bacterial cell division protein FtsZ. Alkyl derivatives of 1 are potent antistaphylococcal compounds with suboptimal drug-like properties. Exploration of the structure−activity relationships of analogues of these inhibitors led to the identification of potent antistaphylococcal compounds with improved pharmaceutical properties.

An Improved Small-Molecule Inhibitor of FtsZ with Superior In Vitro Potency, Drug-Like Properties, and In Vivo Efficacy

ABSTRACT The bacterial cell division protein FtsZ is an attractive target for small-molecule antibacterial drug discovery. Derivatives of 3-methoxybenzamide, including compound PC190723, have been reported to be potent and selective antistaphylococcal agents which exert their effects through the disruption of intracellular FtsZ function. Here, we report the further optimization of 3-methoxybenzamide derivatives towards a drug candidate. The in vitro and in vivo characterization of a more advanced lead compound, designated compound 1, is described. Compound 1 was potently antibacterial, with an average MIC of 0.12 μg/ml against all staphylococcal species, including methicillin- and multidrug-resistant Staphylococcus aureus and Staphylococcus epidermidis. Compound 1 inhibited an S. aureus strain carrying the G196A mutation in FtsZ, which confers resistance to PC190723. Like PC190723, compound 1 acted on whole bacterial cells by blocking cytokinesis. No interactions between compound 1 and a diverse panel of antibiotics were measured in checkerboard experiments. Compound 1 displayed suitable in vitro pharmaceutical properties and a favorable in vivo pharmacokinetic profile following intravenous and oral administration, with a calculated bioavailability of 82.0% in mice. Compound 1 demonstrated efficacy in a murine model of systemic S. aureus infection and caused a significant decrease in the bacterial load in the thigh infection model. A greater reduction in the number of S. aureus cells recovered from infected thighs, equivalent to 3.68 log units, than in those recovered from controls was achieved using a succinate prodrug of compound 1, which was designated compound 2. In summary, optimized derivatives of 3-methoxybenzamide may yield a first-in-class FtsZ inhibitor for the treatment of antibiotic-resistant staphylococcal infections.

Design, synthesis and structure–activity relationships of substituted oxazole–benzamide antibacterial inhibitors of FtsZ

The design, synthesis and structure-activity relationships of a series of oxazole-benzamide inhibitors of the essential bacterial cell division protein FtsZ are described. Compounds had potent anti-staphylococcal activity and inhibited the cytokinesis of the clinically-significant bacterial pathogen Staphylococcus aureus. Selected analogues possessing a 5-halo oxazole also inhibited a strain of S. aureus harbouring the glycine-to-alanine amino acid substitution at residue 196 of FtsZ which conferred resistance to previously reported inhibitors in the series. Substitutions to the pseudo-benzylic carbon of the scaffold improved the pharmacokinetic properties by increasing metabolic stability and provided a mechanism for creating pro-drugs. Combining multiple substitutions based on the findings reported in this study has provided small-molecule inhibitors of FtsZ with enhanced in vitro and in vivo antibacterial efficacy.

Baylis–Hillman Reaction: Convenient Ascending Syntheses and Biological Evaluation of Acyclic Deoxy Monosaccharides as Potential Antimycobacterial Agents

A series of acyclic deoxy carbohydrate derivatives from easily available carbohydrate enals 1, 2, 3 or 5 were prepared involving the Baylis-Hillman reaction. These newly formed carbohydrate based Baylis-Hillman adducts and their amino derivatives were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H(37)R(v). Among the compounds evaluated for their antimycobacterial activity, compound (10) showed the desired activity in the range of 3.125 microg/mL.

Higher acyclic nitrogen containing deoxy sugar derivatives: a new lead in the generation of antimycobacterial chemotherapeutics.

Syntheses of higher acyclic nitrogen containing deoxy sugar derivatives via nitroaldol reaction of different nitroalkanes with 2,3-dideoxy-alpha,beta-unsaturated aldehydo sugars obtained from glycals namely acetylated glucal and galactal and their in vitro antimycobacterial activity are presented.

Design, synthesis and biological evaluation of α-substituted isonipecotic acid benzothiazole analogues as potent bacterial type II topoisomerase inhibitors.

The discovery and optimisation of a new class of benzothiazole small molecules that inhibit bacterial DNA gyrase and topoisomerase IV are described. Antibacterial properties have been demonstrated by activity against DNA gyrase ATPase and potent activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus pyogenes and Haemophilus influenzae. Further refinements to the scaffold designed to enhance drug-likeness included analogues bearing an α-substituent to the carboxylic acid group, resulting in excellent solubility and favourable pharmacokinetic properties.

Protective antigens of Mycobacterium habana are distributed between peripheral and integral compartments of plasma membrane: a study in experimental tuberculosis of mouse.

Mycobacterium habana, a cultivable nonpathogenic mycobacterium provides appreciable resistance in mouse against M. tuberculosis infection. This study is aimed at identification and characterization of protective antigens of M. habana. Protective potential of antigens of cell wall (CW), cell membrane (CM), cytosol (CS) and peripheral and integral compartments of the membrane fraction of M. habana was explored against experimental tuberculosis in mouse. Peripheral and integral membrane proteins were characterized by SDS-PAGE and differential staining with silver and periodic acid. Results reveal that protective antigens are distributed in both peripheral and integral membrane compartments though such effect is dominant in the former. Polysaccharide staining showed that LAM, LM and PIMs have a preference for the detergent phase. Peripheral and integral compartments constitute, respectively, 68 and 31% of the total membrane protein.

The 65 kDa protein of Mycobacterium habana and its putative role in immunity against experimental tuberculosis

Mycobacteria including Mycobacterium tuberculosis and Mycobacterium leprae possess multiple antigens some of which inhibit other anti‐mycobacterial immune responses. Whole cell vaccines are not free from these suppressive molecules and may adversely affect the immunogenic response(s). Purified protein components having only immunogenic properties should prove to be superior vaccine(s). Mycobacterium habana, a candidate vaccine for mycobacterial infections has been dissected for analysing its antigenic myriad. A 65 kDa protein of this mycobacterium has been isolated and characterized for its protective and cell mediated immune responses. The protein was isolated in pure form using an isotachophoresis (SDS–PAGE filtration) technique and identified with low molecular weight markers along with mAb using the immunoblot technique. Mab IIH9 has identified a 65 kDa protein in M. habana. This protein has been found to be immunoprotective in mice against M. tuberculosis H37Rv infection. It generates high levels of DTH responses in mice against M. tuberculosis and M. leprae antigens and inhibits migration of sensitized cells under the antigenic influence of homologous and heterologous origin. Possibilities of developing this protein as a subunit vaccine are discussed in this report.

Discovery and in vivo evaluation of alcohol-containing benzothiazoles as potent dual-targeting bacterial DNA supercoiling inhibitors

A series of dual-targeting, alcohol-containing benzothiazoles has been identified with superior antibacterial activity and drug-like properties. Early lead benzothiazoles containing carboxylic acid moieties showed efficacy in a well-established in vivo model, but inferior drug-like properties demanded modifications of functionality capable of demonstrating superior efficacy. Eliminating the acid group in favor of hydrophilic alcohol moieties at C(5), as well as incorporating solubilizing groups at the C(7) position of the core ring provided potent, broad-spectrum Gram-positive antibacterial activity, lower protein binding, and markedly improved efficacy in vivo.

Lymphostimulatory and delayed-type hypersensitivity responses to a candidate leprosy vaccine strain: Mycobacterium habana.

Lymphostimulatory and delayed-type hypersensitivity (DTH) immune responses to a candidate antileprosy vaccine Mycobacterium habana have been quantified in inbred AKR mice. M. habana vaccine in three physical states, live, heat-killed and gamma-irradiated, was given intradermally to separate groups of mice and after 28 days these mice were given subcutaneous challenge with heat-killed M. leprae and heat-killed M. habana in the left hind footpad. Live BCG vaccine alone and in combination with gamma-irradiated M. habana were also compared similarly. A sufficient degree of DTH response was generated in mice by M. habana vaccine in all physical forms against two challenge antigens (lepromin and habanin). The BCG combination with M. habana did not increase the DTH response indicating internal adjuvanticity endowed in M. habana. The active hypersensitivity of immunized mice was transferable to syngeneic mice by the transfer of sensitized cells from the donor to the recipient mice intravenously. M. leprae-infected Rhesus monkey PBMC have shown comparable stimulatory response with M. habana (sonicate), and M. leprae (sonicate) antigens. The possibility of developing M. habana as a candidate antileprosy vaccine is discussed.