Synthesis and preliminary biological evaluation of a small library of hybrid compounds based on Ugi isocyanide multicomponent reactions with a marine natural product scaffold

A mixture-based combinatorial library of five Ugi adducts (4-8) incorporating known antitubercular and antimalarial pharmacophores was successfully synthesized, starting from the naturally occurring diisocyanide 3, via parallel Ugi four-center three-component reactions (U-4C-3CR). The novel α-acylamino amides obtained were evaluated for their antiinfective potential against laboratory strains of Mycobacterium tuberculosis H37Rv and chloroquine-susceptible 3D7 Plasmodium falciparum. Interestingly, compounds 4-8 displayed potent in vitro antiparasitic activity with higher cytotoxicity in comparison to their diisocyanide precursor 3, with the best compound exhibiting an IC50 value of 3.6 nM. Additionally, these natural product inspired hybrids potently inhibited in vitro thromboxane B2 (TXB2) and superoxide anion (O2(-)) generation from Escherichia coli lipopolysaccharide (LPS)-activated rat neonatal microglia, with concomitant low short-term toxicity

Identification of Novel Inhibitors of Nonreplicating Mycobacterium tuberculosis Using a Carbon Starvation Model

During Mycobacterium tuberculosis infection, a population of bacteria is thought to exist in a nonreplicating state, refractory to antibiotics, which may contribute to the need for prolonged antibiotic therapy. The identification of inhibitors of the nonreplicating state provides tools that can be used to probe this hypothesis and the physiology of this state. The development of such inhibitors also has the potential to shorten the duration of antibiotic therapy required. Here we describe the development of a novel nonreplicating assay amenable to high-throughput chemical screening coupled with secondary assays that use carbon starvation as the <i>in vitro</i> model. Together these assays identify compounds with activity against replicating and nonreplicating M. tuberculosis as well as compounds that inhibit the transition from nonreplicating to replicating stages of growth. Using these assays we successfully screened over 300,000 compounds and identified 786 inhibitors of nonreplicating M. tuberculosis In order to understand the relationship among different nonreplicating models, we tested 52 of these molecules in a hypoxia model, and four different chemical scaffolds in a stochastic persister model, and a streptomycin-dependent model. We found that compounds display varying levels of activity in different models for the nonreplicating state, suggesting important differences in bacterial physiology between models. Therefore, chemical tools identified in this assay may be useful for determining the relevance of different nonreplicating <i>in vitro</i> models to <i>in vivo </i>M. tuberculosis infection. Given our current limited understanding, molecules that are active across multiple models may represent more promising candidates for further development

BUMC Annual Report: 1968-1969

Annual report of the Boston University Medical Center

Discovery and Optimization of Benzotriazine Di-<i>N</i>-Oxides Targeting Replicating and Nonreplicating Mycobacterium tuberculosis

Compounds bactericidal against both replicating and nonreplicating Mtb may shorten the length of TB treatment regimens by eliminating infections more rapidly. Screening of a panel of antimicrobial and anticancer drug classes that are bioreduced into cytotoxic species revealed that 1,2,4-benzotriazine di-<i>N</i>-oxides (BTOs) are potently bactericidal against replicating and nonreplicating Mtb. Medicinal chemistry optimization, guided by semiempirical molecular orbital calculations, identified a new lead compound (<b>20q</b>) from this series with an MIC of 0.31 μg/mL against H37Rv and a cytotoxicity (CC₅₀) against Vero cells of 25 μg/mL. <b>20q</b> also had equivalent potency against a panel of single-drug resistant strains of Mtb and remarkably selective activity for Mtb over a panel of other pathogenic bacterial strains. <b>20q</b> was also negative in a L5178Y MOLY assay, indicating low potential for genetic toxicity. These data along with measurements of the physiochemical properties and pharmacokinetic profile demonstrate that BTOs have the potential to be developed into a new class of antitubercular drugs

Synthesis and preliminary biological evaluation of a small library of hybrid compounds based on Ugi isocyanide multicomponent reactions with a marine natural product scaffold

A mixture-based combinatorial library of five Ugi adducts (4–8) incorporating known antitubercular and antimalarial pharmacophores was successfully synthesized, starting from the naturally occurring diisocyanide 3, via parallel Ugi four-center three-component reactions (U-4C-3CR). The novel α-acylamino amides obtained were evaluated for their antiinfective potential against laboratory strains of Mycobacterium tuberculosis H(37)Rv and chloroquine-susceptible 3D7 Plasmodium falciparum. Interestingly, compounds 4–8 displayed potent in vitro antiparasitic activity with higher cytotoxicity in comparison to their diisocyanide precursor 3, with the best compound exhibiting an IC(50) value of 3.6 nM. Additionally, these natural product inspired hybrids potently inhibited in vitro thromboxane B(2) (TXB(2)) and superoxide anion (O(2)(−)) generation from Escherichia coli lipopolysaccharide (LPS)-activated rat neonatal microglia, with concomitant low short-term toxicity

The antimicrobial effect of colistin methanesulfonate on Mycobacterium tuberculosis in vitro

Polymyxins have previously been described to have activity against M. tuberculosis (MTB), but further research was abandoned due to systemic toxicity concerns to achieve the required MIC. Colistin methanesulfonate (CMS), a polymyxin, is well tolerated when inhaled directly into the lungs, resulting in high local concentrations. We report here for the first time, MIC and MBC data for CMS determined by the microtiter Alamar Blue assay (MABA). We also determined how the MIC would be affected by the presence of pulmonary surfactant (PS) and if any synergy with isoniazid (INH) and rifampicin (RIF) exists. The effect of CMS on the ultrastructure of MTB was also determined. The MIC for CMS was 16 mg/L, while the MBC was 256 mg/L. MIC for CMS in PS was antagonised by eight fold. For synergy, indifference was determined while time-kill assays revealed a greater killing effect when CMS was used together with INH. Ultrastructure analysis suggests that the disruption of the outer polysaccharide layer of MTB by CMS may lead to enhanced uptake of INH. Our findings may provide insight for further investigations of CMS against MTB.http://intl.elsevierhealth.com/journals/tube2016-07-30hb201