Development of new drug-regimens against multidrug-resistant tuberculosis

Isoflavonoid and Furanochromone Natural Products as Potential DNA Gyrase Inhibitors: Computational, Spectral, and Antimycobacterial Studies

In pursuit of new antitubercular agents, we here report the antimycobacterial (H₃₇Rv) and DNA gyrase inhibitory potential of daidzein and khellin natural products (NPs). We procured a total of 16 NPs based on their pharmacophoric similarities with known antimycobacterial compounds. The H₃₇Rv strain of M. tuberculosis was found to be susceptible to only two out of the 16 NPs procured; specifically, daidzein and khellin each exhibited an MIC of 25 μg/mL. Moreover, daidzein and khellin inhibited the DNA gyrase enzyme with IC₅₀ values of 0.042 and 0.822 μg/mL, respectively, compared to ciprofloxacin with an IC₅₀ value of 0.018 μg/mL. Daidzein and khellin were found to have lower toxicity toward the vero cell line, with IC₅₀ values of 160.81 and 300.23 μg/mL, respectively. Further, molecular docking study and MD simulation of daidzein indicated that it remained stable inside the cavity of DNA GyrB domain for 100 ns.

Kolocouris A. Synthesis and Testing of Analogs of the Tuberculosis Drug Candidate SQ109 against Bacteria and Protozoa: Identification of Lead Compounds against Mycobacterium abscessus and Malaria Parasites

SQ109 is a tuberculosis drug candidate that has high potency against Mycobacterium tuberculosis and is thought to function at least in part by blocking cell wall biosynthesis by inhibiting the MmpL3 transporter. It also has activity against bacteria and protozoan parasites that lack MmpL3, where it can act as an uncoupler, targeting lipid membranes and Ca2+ homeostasis. Here, we synthesized 18 analogs of SQ109 and tested them against M. smegmatis, M. tuberculosis, M. abscessus, Bacillus subtilis, and Escherichia coli, as well as against the protozoan parasites Trypanosoma brucei, T. cruzi, Leishmania donovani, L. mexicana, and Plasmodium falciparum. Activity against the mycobacteria was generally less than with SQ109 and was reduced by increasing the size of the alkyl adduct, but two analogs were ∼4-8-fold more active than SQ109 against M. abscessus, including a highly drug-resistant strain harboring an A309P mutation in MmpL3. There was also better activity than found with SQ109 with other bacteria and protozoa. Of particular interest, we found that the adamantyl C-2 ethyl, butyl, phenyl, and benzyl analogs had 4-10× increased activity against P. falciparum asexual blood stages, together with low toxicity to a human HepG2 cell line, making them of interest as new antimalarial drug leads. We also used surface plasmon resonance to investigate the binding of inhibitors to MmpL3 and differential scanning calorimetry to investigate binding to lipid membranes. There was no correlation between MmpL3 binding and M. tuberculosis or M. smegmatis cell activity, suggesting that MmpL3 is not a major target in mycobacteria. However, some of the more active species decreased lipid phase transition temperatures, indicating increased accumulation in membranes, which is expected to lead to enhanced uncoupler activity.

Optimized LC-MS/MS quantification of tuberculosis drug candidate macozinone (PBTZ169), its dearomatized Meisenheimer Complex and other metabolites, in human plasma and urine

Tuberculosis, and especially multidrug-resistant tuberculosis (MDR-TB), is a major global health threat which emphasizes the need to develop new agents to improve and shorten treatment of this difficult-to-manage infectious disease. Among the new agents, macozinone (PBTZ169) is one of the most promising candidates, showing extraordinary potency in vitro and in murine models against drug-susceptible and drug-resistant Mycobacterium tuberculosis. A previous analytical method using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed by our group to support phase I clinical trials of PBTZ169. These plasma sample analyses revealed the presence of several additional metabolites among which the most prominent was H₂PBTZ, a reduced species obtained by dearomatization of macozinone, one of the first examples of Meisenheimer Complex (MC) metabolites identified in mammals. Identification of these new metabolites required the optimization of our original method for enhancing the selectivity between isobaric metabolites as well as for ensuring optimal stability for H₂PBTZ analyses. Sample preparation methods were also developed for plasma and urine, followed by extensive quantitative validation in accordance with international bioanalytical method recommendations, which include selectivity, linearity, qualitative and quantitative matrix effect, trueness, precision and the establishment of accuracy profiles using β-expectation tolerance intervals for known and newer analytes. The newly optimized methods have been applied in a subsequent Phase Ib clinical trial conducted in our University Hospital with healthy subjects. H₂PBTZ was found to be the most abundant species circulating in plasma, underscoring the importance of measuring accurately and precisely this unprecedented metabolite. Low concentrations were found in urine for all monitored analytes, suggesting extensive metabolism before renal excretion.

Identification of novel anti-tuberculosis agent: An in silico investigation

BACKGROUND

Multi-drug resistance tuberculosis is chronic and highly affected to mankind. Millions of people are affected by tuberculosis and lost their lives every year. Mycobacterium tuberculosis is resistant to the most commonly used anti-TB drugs, hence new drugs need to be developed in a short time. In this direction, many chemical compounds including benzimidazole derivatives have been identified as potent anti-tb agents.

METHOD

Various benzimidazole derivatives were subjected to in-silico computational screening to identify the potent anti-tubercular analogues. The ADME pharmacokinetics evaluation was performed to identify the drug-like molecules. Molecular docking investigation of selected compounds was performed against Mycobacterium Tuberculosis Enoyl Reductase (Inha) with PDB ID: 2B37, 1QG6, 4TZK, and 4TZK. The common pharmacophore hypothesis was generated using the molecular docking post-processing module.

RESULT

The result of ADME pharmacokinetics of some compounds is very close to the drug-like properties and can be developed as good inhibitors. Molecular docking study suggests that the proposed benzimidazole and 4H-pyran derivative have better binding affinity than standard and triclosan derivatives. Results from the pharmacophore hypothesis development study also support and suggest our prediction regarding the minimum pharmacophore features required in ligands to behave as a Mycobacterium Tuberculosis inhibitor.

CONCLUSION

Coumarin, phenylurea clubbed benzimidazole moiety and pyrano[2,3-c]pyrazole derivatives have shown greater selectivity and potency towards Mycobacterium Tuberculosis. By employing a combination of ADME, docking, and pharmacophore study calculations, novel potent hits to inhibit enoyl-acp reductase were identified with the points for consideration for designing of enoyl-acp reductase inhibitor.

Recent updates in natural terpenoids as potential anti-mycobacterial agents

Tuberculosis is considered as a leading health issue globally. Even though, the todays first line anti-mycobacterial treatments used in the hospital have low deaths, multidrug-resistance forms of the ailment have now spread globally and become a major issue. The wide-ranging biodiversity of medicinal plants, ocean animals have gained considerable attention for drug discovery in previous spans, and the emergence of TB drug resistance has inspired interest in judging natural products (NPs) to cure this disease. Till now, several compounds have been isolated from natural sources with anti-mycobacterial activity, few of which demonstrate significant activity and have the potential for further development. Worldwide huge natural flora and fauna are existing, this flora and fauna must be investigated for new potent lead against infectious TB. This review systematically surveys various classes of terpenoid molecules obtained from different medicinal plants, fungi, sponges, and sea plumes with anti-TB activity, which could be useful for further optimization and development in this field.

Improved Synthesis of the Antitubercular Agent SQ109

We present here an improved procedure for the preparation of the promising antitubercular drug SQ109 that is currently in phase Ib/III of clinical trials against Mycobacterium tuberculosis. We investigated and tested the literature synthetic procedure that enables the development of structure–activity relationships and report the observed inconsistencies as well as presenting improvements or novelties for the more efficient preparation of SQ109. Most significantly we applied a novel reduction step of the aminoamide precursor using Me3SiCl­/LiAlH4 under mild conditions. These findings are important for research groups investigating the efficacy of this drug and analogues in academia and industry.

Xanthone: A Promising Antimycobacterial Scaffold

BACKGROUND

Tuberculosis (TB) is one of the infectious diseases associated with high rate of morbidity and mortality and still remains one of the top-ten leading causes of human death in the world. The development of new anti-TB drugs is mandatory due to the existence of latent infection as well as the expansion of the resistant Mycobacterium tuberculosis (MBT) strains. Xanthones encompass a wide range of structurally diverse bioactive compounds, obtained either naturally or through chemical synthesis. There is a growing body of literature that recognizes the antitubercular activity of xanthone derivatives.

OBJECTIVE

The objective of this review is to highlight the main natural sources along with the critical design elements, structure-activity relationships (SARs), modes of action and pharmacokinetic profiles of xanthone-based anti-TB compounds.

METHODS

In the present review, the anti-TB activity of xanthones reported in the literature from 1972 to date is presented and discussed.

RESULTS

Exploration of xanthone scaffold led to the identification of several members of this class having superior activity against both sensitive and resistant MBT strains with distinctive mycobacterial membrane disrupting properties. However, studies regarding their modes of action, pharmacokinetic properties and safety are limited.

CONCLUSION

Comprehendible data and information are afforded by this review and it would certainly provide scientists with new thoughts and means which will be conducive to design and develop new drugs with excellent anti-TB activity through exploration of xanthone scaffold.

Development of (4-methoxyphenyl)-1H-tetrazol-5-amine regioisomers as a new class of selective antitubercular agents

A series of halogenated (4-methoxyphenyl)-1H-tetrazol-5-amine regioisomers (1a-9a, 1b-9b) were synthesized from their corresponding thiourea analogues (1-9). The synthesis pathway was confirmed by an X-ray crystallographic studies of 1a, 1b and 5a. Title derivatives were tested for their in vitro antitubercular activity against standard, "wild-type" and atypical mycobacteria. The highest therapeutic potential was attributed to isomeric N-(bromophenyl)tetrazoles 8a and 9a. Their growth-inhibitory effect against multidrug-resistant Mycobacterium tuberculosis Spec. 210 was 8-16-fold stronger than that of the first-line tuberculostatics. Other new tetrazole-derived compounds were also more or equally effective towards that pathogen comparing to the established pharmaceuticals. Among non-tuberculous strains, Mycobacterium scrofulaceum was the most susceptible to the presence of the majority of tetrazole derivatives. The synergistic interaction was found between 9a and streptomycin, as well as the additivity of both 8a and 9a in pairs with isoniazid, rifampicin and ethambutol. None of the studied compounds displayed antibacterial or cytotoxic properties against normal and cancer cell lines, which indicated their highly selective antimycobacterial effects.