**3.2 Moxifloxacin, Gatifloxacin, levofloxacin and DC-159a**

Moxifloxacin and Gatifloxacin are fourth-generation broad-spectrum antibiotics belonging to the family of fluoroquinolone drugs. The main function of this class of antimicrobials is to inhibit the bacterial enzymes DNA gyrase and topoisomerase IV which are crucial for DNA duplication events such as transcription, recombination and cell replication [16, 18, 19]. They were initially approved for the treatment of a number of bacterial infections of the skin, stomach and lungs and along with levofloxacin has also shown promise as an effective and safe candidate for inclusion in the current TB treatment regimen [16, 20]. This is mainly because of their potent antimycobacterial activity as studies have shown that they can significantly improve sputum culture conversion rate and clinical outcome of TB treatment as well as reduce TB resurgence after treatment [17, 21]. These antimicrobials are currently being evaluated as a possible replacement for Isoniazid or Ethambutol in patients with poor tolerability as they were shown to exhibit potent antimycobacterial activity *in vitro* [16]*.* Moxifloxacin, Gatifloxacin and Levofloxacin are the most commonly prescribed fluoroquinolone drugs used to treat patients with MDR-TB. Despite these analogues displaying enhanced antimycobacterial activity *in vitro* and *in vivo*, levofloxacin was shown to be more cost-effective, and therefore more accessible in resource-limited high burden settings [18]. In comparison to moxifloxacin, gatifloxacin and levofloxacin, DC-159a, a relatively new fluoroquinolone analogue was shown to exhibit enhanced bactericidal activity against MDR-TB both *in vitro* and *in vivo* and may therefore be a promising new therapeutic candidate for reducing treatment time for both MDR- and drug-sensitive (DS)-TB [22, 23].
