New anti-tuberculosis drugs with novel mechanisms of action.

It is estimated that a third of the world's population is currently infected with tuberculosis, leading to 1.6 million deaths annually. The current drug regimen is 40 years old and takes 6-9 months to administer. In addition, the emergence of drug resistant strains and HIV co-infection mean that there is an urgent need for new anti-tuberculosis drugs. The twenty-first century has seen a revival in research and development activity in this area, with several new drug candidates entering clinical trials. This review considers new potential first-line anti-tuberculosis drug candidates, in particular those with novel mechanisms of action, as these are most likely to prove effective against resistant strains. A brief overview of current first-line and recent drugs (such as fluoroquinolones, rifampicin and isoniazid analogues) is initially presented. This is followed by a description of structure-activity relationships, in vitro and in vivo activity, pharmacokinetics, mechanism of action, combination regimens and clinical trials of the new drug candidates SQ109, PA-824, OPC-67683, TMC207 and others.