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Agents for Tuberculosis Chemotherapy

#B-1928


Development of Novel Anti-Tuberculosis Agents Based on Derivatives of Aromatic Hydroxyaldehydes, Diphenols and Aminophenols

Tech Area / Field

  • MED-DRG/Drug Discovery/Medicine
  • CHE-RAD/Photo and Radiation Chemistry/Chemistry
  • CHE-SYN/Basic and Synthetic Chemistry/Chemistry

Status
3 Approved without Funding

Registration date
14.03.2011

Leading Institute
Belarussian State University / Institute of Physical Chemical Problems, Belarus, Minsk

Supporting institutes

  • State Institution “National Research-and-Practice Centre of Pulmonology and Phtisiology”, Belarus, Minsk

Collaborators

  • Katholieke Universiteit Leuven / Rega Institute for Medical Research, Belgium, Leuven\nSwedish Institute for Infectious Disease Control (SMI), Sweden, Solna

Project summary

The Project purpose: Designing, synthesis and structural identification of new compounds of aromatic series, investigation of their anti-radical properties, performance of in vitro screening for anti-tuberculosis activity with subsequent analysis of anti-radical and pharmacological activity of the compounds under study as function of their structures. The main purpose of the study: finding out novel compounds displaying activity against M. tuberculosis.

The problem statement: Tuberculosis (TB) caused by M.tuberculosis remains one of the most dangerous infectious diseases. The current epidemiological situation provides good reasons to believe that about a third of the global population is infected with tuberculosis in some latent form. A serious problem in TB control is the emergence of Mycobacterium tuberculosis with multidrug resistance (MDR-TB). Drug therapy of tuberculosis has definite limitations. Treatment with anti-TB drugs (ATBDs) is accompanied by various side effects and is very lengthy. Moreover, not a single new drug has been added to the arsenal of ATBD since the 70-ies. Currently available schemes for treatment are based on polychemotherapy involving 4-5 ATBDs. However, the spread of drug resistance makes M. tuberculosis insensitive to various agents. In this connection, there is an urgent need for the development of additional ATBDs, which were effective in both active and latent forms of TB infection [C.E. Barry, M.S. Cheung (2009), Scientific American 300, 62-69].

Resistance to oxidative stress is of paramount importance for survival of aerobic pathogens, including M. tuberculosis. Reactive oxygen species (ROS), such as superoxide radical anions, hydrogen peroxide, hydroxyl radicals and singlet oxygen are formed as by-products of oxygen metabolism. ROS cause damage to the most of biological molecules, such as lipids, proteins and nucleic acids [B. Halliwell, J.M.C. Gutteridge (2009) Free Radicals in Biology and Medicine. 4th Ed., Clarendon Press, Oxford], and play an important role in microbicidal activity manifested by the immune system. Tuberculosis bacteria being subjected to the “oxidative burst” realize various mechanisms for protecting themselves from oxidative damage. Phenolic glycolipids and cyclopropanated mycolic acids protect the cell wall. The ROS-neutralizing ferments - superoxide dismutase and catalase – make their own contribution in cytosol protection, and can play an important role in virulence of such pathogens as mycobacteria. In addition to the fermentative detoxification from ROS and RNS, the maintenance of reductive character in cellular environment of pathogenic bacteria plays an important role in the antioxidant protection systems of bacteria. [Kate S. Carroll et al. (2007), Infectious Disorders – Drug Targets, 7, 140-158].

In the opinion of the Project authors, a promising group of compounds to be used in the search for new synthetic low-molecular antimycobacterial agents could be spatially-hindered phenols, diphenols, aromatic aldehydes, aminophenols and their derivatives. During many years, the Project Authors performed the work on synthesis of such compounds, as well as investigations of their antioxidant, radical-inhibitory and pharmacological activity [O.I. Shadyro et al. (2008), Bioorg. Med. Chem. Lett., 18, 2420-2423]. Biological and pharmacological studies conducted both in vitro and in vivo show that the derivatives of a number of spatially-hindered phenols and aminophenols, as well as their metal complexes, manifest antiviral, antifungal and antibacterial activity [N.V.Loginova et al. (2006), Bioorg. Med. Chem. Lett., 16, 24-37]. Toxicological studies indicate low to moderate toxicity of many of these compounds.

The presence of a broad spectrum of anti-infectious activity in conjunction with relative safety, as well as the ability to exert influence on formation and action of reactive oxygen species and other radicals, give grounds to believe that the search for new anti-TB agents should be performed among the structures of the above named type. Preliminary testing for activity against M. tuberculosis has been performed with several imino derivatives of 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde. At concentrations 2-10 μg/ml, these new organic compounds manifested 100 % inhibition of M. tuberculosis in cell culture experiments conducted with a drug-sensitive strain (H37Rv). Metal complexes of the above named compounds with Ag(I), Fe(II) and Mn(II) proved to be even more active (MIC 1.25-2.5 μg/ml). The Project Authors are planning to synthesize a considerable number of new compounds with a view to perform afterwards a comprehensive screening aimed at discovery of novel non-toxic inhibitors of M. tuberculosis.

Influence of the proposed Project on the progress in the area of development of new antimicrobial agents: The Project authors plan to develop and characterize new active substances– diphenol and aminophenol derivatives, as well as their metal complexes, able to effectively inhibit pathogenic tuberculosis mycobacteria, including multidrug-resistant strains.

The Project Participants: Research Institute for Physicochemical Problems of the Belarusian State University (RI PCP BSU) and State Institution “National Research-and-Practice Centre of Pulmonology and Phtisiology” (NRPCPP).

The researchers of RI PCP BSU have wide experience in the area of organic synthesis, as well as investigations of antioxidants and radical reaction inhibitors. Their work is associated with designing and preparation of new compounds possessing pharmacological and antioxidant activity, as well as with studies of homolytic processes resulting in fragmentation and oxidation of important cell membrane components.

The research team from NRPCPP has more than 80-year experience in studies and treatment of tuberculosis and non-specific diseases of respiratory organs. The Centre is equipped with up-to-date X-ray, bronchoscopic, and ultrasound instruments, as well as a modern helical tomograph. Automated BACTEC MGIT-960 system allows microbiological diagnostics of tuberculosis to be performed, as well as testing drug resistance of Mycobacterium tuberculosis to various ATBDs.

Expected results and their application:

The development category - applied studies. After performance of 3 main tasks, the following results will be obtained:

  • Syntheses of 80 to 100 compounds and their complete structural identification will be carried out using NMR spectroscopy, mass spectrometry, elemental analysis, determination of physicochemical indices, etc.
  • Investigation of the effects produced by the obtained compounds on processes involving free radicals will be performed in chemical and biological models.
  • All of the synthesized compounds will be subjected to in vitro screening with a view to discover activity against M. tuberculosis. Both drug-sensitive and drug-resistant strains will be included in the testing. Also, activity against rapidly growing non-pathogenic mycobacteria will be investigated.

The best performing compounds, as regards activity, selectivity and safety, will be selected for further trials and the development of clinical forms of potential pharmaceutical products.

Application of the Project results: The final goal of this exploratory project is the discovery of novel original compounds possessing anti-TB activity. Optimization of these structures will yield prototypes of new drugs, which could be characterized as effective, non-toxic, low-cost pharmaceuticals manufactured by local industry.

Compliance of the Project with the ISTC goals: The Project complies with the ISTC goals for the following reasons:

  • the Project allows its participants formerly involved in research work in military area to switch over to solving purely humanistic problems, i.e. the development of new drugs;
  • the experimental results of the project implementation will contribute to integration of the Project participants into the global scientific community, because these results will be obtained in cooperation with foreign specialists in the areas of chemistry, biology and medicine;
  • the Project is targeted on solving applied problems for peaceful purposes in the area of public health;
  • the Project realization will enable its participants to enter the market economy, due to the expected sale of licenses associated with the «know-how» used in the search for new pharmacologically active substances, as well as the licenses for synthesis of the substances.

The Project effort: The Project duration is 2 years, because it has a multidiscipline character and requires carrying-out large-scale work in the area of targeted synthesis of a large number (about 100) of new compounds and investigation of their physicochemical and anti-TB properties. In this connection, a team of 11 participants will be recruited for the Project implementation, including 7 from RI PCP BSU and 4 from NRPCPP.

The role of foreign Collaborators: The following forms of participation in the Project have been agreed with the collaborators:

  • performance of joint scientific research;
  • participation in joint seminars and conferences;
  • exchange of scientific information.

Technical approach and methodology: The approach that will be used for the Project implementation consists in systematic and purposeful performance of research work making it possible to establish causal relationship between structures of compounds and their anti-tuberculosis activity. Preliminary data show that that there are compounds among diphenol and aminophenol derivatives suppressing both pathogenic and non-pathogenic mycobacteria in in vitro experiments. Technical solution of the problems will be ensured by using up-to-date synthetic methods, as well as physicochemical research techniques such as gas and liquid chromatography, IR, ESR and NMR spectroscopy, mass spectrometry, elemental analysis, etc.. Microbiological studies will be conducted in accordance with the standard recommendations on mycobacterial culture and determination of the sensitivity to various chemical compounds. The synthesized compounds will be tested in vitro for activity against M. tuberculosis, including both sensitive and drug resistant strains, with known resistance to various combinations of anti-TB drugs to exclude any cross-resistance between the new alternative agents and compounds presently used in anti-TB therapy. The automated BACTEC MGIT-960 system will enable microbiological characterization of M. tuberculosis, including testing for drug resistance.


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