Pro-apoptotic Drugs as Host-Directed Treatments for Pulmonary Tuberculosis

During the early phase of infection, Mycobacterium tuberculosis proliferates in macrophages and other cells, preventing apoptosis by the induction of proteins such as from the Bcl-2 family, leading to necrosis of the infected cells. Necrosis increases tuberculosis (TB)-associated morbidity by causing tissue destruction, inducing inflammation, promoting fibrosis, and impairing vascular supply, thereby reducing the penetration of antimicrobials and immune cells to the areas where they are needed most. We have recently demonstrated that adjunctive use of navitoclax, an orally bioavailable, pro-apoptotic small molecule Bcl-2 inhibitor (in clinical trials for cancer treatments, with excellent safety profile), improves bacterial elimination and decreases lung damage in animal models of TB. Additionally, navitoclax has anti-fibrotic effects, which can reverse and prevent lung fibrosis and may promote antibiotic penetration into TB lesions. In fact, post-TB lung disease is a recognized consequence of pulmonary TB, with associated chronic adverse outcomes beyond the TB treatments, including bronchiectasis, poor lung function and respiratory symptoms. Our central hypothesis is that navitoclax (or similar pro-apoptotic drugs) could be used as a cell death mechanism (CDM)-based small molecule, host-directed therapy (HDT) approach to shorten TB treatments, and prevent post-TB lung disease. To understand how these novel therapeutics impact the lung immune landscape, remodeling and bacterial clearance, we have developed several novel, clinically translatable positron emission tomography (PET)-based imaging biomarkers to longitudinally profile lesional characteristics in live animals: 18F-ICMT-11 for apoptosis, 18F-FAPI-74 for fibrosis, 11C-rifampin and 18F-pretomanid (both chemically identical to the parent antibiotic) for tissue antibiotic exposures as well as advanced magnetic resonance and computed tomography imaging to visualize pulmonary damage and necrosis. Finally, we have developed complementary high-dimensional immunophenotyping by flow cytometry to assess the lung immune landscape, remodeling and fibrosis. We will develop CDM-based small molecule HDT approaches for TB treatments, which brings together cutting-edge technologies and cross-disciplinary expertise in TB pathogenesis (Jain), pulmonary immunology (D'Alessio) and oncology (Carroll). There are currently no HDTs approved for clinical use for the treatment of pulmonary TB. Therefore, in this proposal, we will leverage our expertise in animal models of TB, advanced whole-body in vivo imaging and high-dimensional immunophenotyping to gain mechanistic insights on the role of pro- apoptotic drugs to shorten treatments for drug-susceptible and multi-drug resistant (MDR) pulmonary TB as well as to prevent post-TB lung disease. Our goals are to utilize novel pro-apoptotic HDTs to develop short (2-3 months versus current 4-6 months or longer), and efficacious TB treatment regimens which also prevent / improve post-TB lung disease, as well as develop novel clinically-translatable imaging approaches to expedite the development of pro-apoptotic drugs for shortening TB treatments.