Multidrug-resistant tuberculosis, accounting for nearly 5% of cases, is difficult and expensive to treat. A recent clinical trial reports positive results for a new drug, delamanid, in people with this form of tuberculosis (N. Engl. J. Med. 366, 2151–2160).

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Delamanid, an inhibitor of mycolic acid synthesis, has previously been shown to have antituberculosis activity in both in vitro and in vivo preclinical studies. Gler et al. tested delamanid at two doses in a randomized, placebo-controlled trial. A total of 321 patients with multidrug-resistant tuberculosis were treated with delamanid, as compared to 160 patients treated with placebo, with all patients receiving a background drug regimen. After 2 months of treatment, the two delamanid-treated groups had a higher proportion of sputum cultures that were negative for mycobacterial growth. However, a dose response was not observed. The drug seemed to be well tolerated, although it was associated with an effect on cardiac electrical activity—QT interval prolongation.

Effects on sputum culture growth have previously been associated with long-term outcomes of tuberculosis treatments, but longer clinical trials of delamanid will be needed. In addition, it will be important to determine how delamanid can be used most effectively in combination with other antituberculosis agents.