Drug-resistant tuberculosis: emerging treatment options

Abstract

Multidrug-resistant tuberculosis has emerged worldwide, with an increasing incidence due to failure of implementation of apparently effective first-line antituberculous therapy as well as primary infection with drug-resistant strains. Failure of current therapy is attributed to a long duration of treatment leading to nonadherence and irregular therapy, lack of patient education about the disease, poverty, irregular supply by care providers, drug-drug interactions in patients coinfected with human immunodeficiency virus (HIV), inadequate regulations causing market overlap and irresponsible drug usage in the private sector, and lack of research, with no addition of new drugs in the last four decades. Present standards of care for the treatment of drugsusceptible tuberculosis, multidrug-resistant tuberculosis, tuberculosis-HIV coinfection, and latent tuberculosis infection are all unsatisfactory. Since 2000, the World Health Organization (WHO) has focused on drug development for tuberculosis, as well as research in all relevant aspects to discover new regimens by 2015 and to eliminate tuberculosis as a public health concern by 2050. As a result, some 20 promising compounds from 14 groups of drugs have been discovered. Twelve candidates from eight classes are currently being evaluated in clinical trials. Ongoing research should prioritize identification of novel targets and newer application of existing drugs, discovery of multitargeted drugs from natural compounds, strengthening host factors by immunopotentiation with herbal immunomodulators, as well as protective vaccines before and after exposure, consideration of surgical measures when indicated, development of tools for rapid diagnosis, early identification of resistant strains, and markers for adequacy of treatment and an integrative approach to fulfill WHO goals. However, regulatory control over the drug market, as well as public-private partnership to use health program facilities to track patients and ensure completion of adequate therapy will be necessary to exploit fully the potential of the newer regimens to eliminate tuberculosis.

Keywords: biomarkers; drug resistance; human immunodeficiency virus; tuberculosis; vaccine.

Figure 1

TB drug development time-line. Abbreviations: TB, tuberculosis; MDR, multidrug-resistant.

Figure 2

TB drug regimen goal. Abbreviation: TB, tuberculosis.