Salicylate-based Drugs as Adjuvants to Potentiate Bedaquiline's Anti-TB Activity

About This Grant

Project Summary In 2022, over 10 million individuals were diagnosed with tuberculosis (TB) and 1.3 million died of the disease. Approximately 4% of these infections consisted of drug resistant TB (DR TB; defined as rifampin or multidrug resistance), which accounted for a disproportionate 12% of TB-related deaths. A major advancement in the treatment of DR TB came with the approval of bedaquiline, a new mycobacterial ATP synthase inhibitor that is the current backbone of second-line regimens. Addition of bedaquiline to second-line regimens has decreased mortality in patients with DR TB and reduced the length of treatment to 6 months. Newer bedaquiline-based combination therapies are now being investigated as potential short-course universal treatment regimens for TB. Rising rates of low-level resistance to bedaquiline threatens these recent gains. Strategies that boost bedaquiline's anti-TB activity may therefore have relevance for further shortening bedaquiline- based anti-TB regimens to less than 6 months and for combatting existing low-level resistance. Our preliminary data shows that the principal metabolite of aspirin, salicylate, enhances bedaquiline's anti-TB activity at a concentration readily achievable in humans. Salicylate may achieve this effect by shuttling the resulting buildup of protons (from bedaquiline's inhibition of ATP synthase) from the intermembrane space into the cytoplasm. This can kill Mycobacterium tuberculosis (Mtb), the causative agent of TB, by further depleting ATP levels and acidifying the Mtb cytoplasm. The aim of this proposal is to quantitate, validate, and better understand how salicylates potentiate bedaquiline's anti-TB activity. The first aim is to quantify this effect in order to identify salicylate and bedaquiline concentrations that result in best anti-TB activity. We will also explore whether other salicylate-based NSAIDs with stronger protonophoric activity show stronger or more potent potentiation of bedaquiline; and to what extent this potentiation restores bedaquiline's activity in clinical Mtb strains with low-level bedaquiline resistance. In the second aim, we will test the hypothesis that salicylates' aforementioned shuttling of protons is its mechanism of action for boosting of bedaquiline's activity. In the final aim, we will translate our findings by utilizing a macrophage infection model that better approximates the environment and stressors Mtb faces upon infection. These three aims will provide crucial preliminary data to justify progression of at least one of these salicylates into animal models, with the ultimate goal of human trials, with the aim of shortening existing bedaquiline-based regimens and addressing the most common form of resistance in the near term.