ABSTRACT The goal of this proposal is to investigate the potential for teixobactin (TXB) to treat drug-resistant tuberculosis (TB). TB is a major global health issue and second largest killer by an infectious agent. Non-compliance by TB patients due to lengthy treatment times have resulted in drug-resistant strains that require longer treatment durations and a high risk of adverse side effects. Thus, there is a pressing need for a drug regimen that is safer, shorter in duration and avoids drug resistance. The most remarkable property of TXB is the lack of any detectable resistance. This lack of resistance is most likely due to its two-pronged mode of action. TXB hits two related targets—lipid II, precursor of peptidoglycan and lipid III, precursor of wall teichoic acid. These highly conserved targets are not mutable, as they are not proteins and are not directly coded by DNA. In addition, once bound to its bacterial target, TXB self-associates into large macromolecular structures that weaken the membrane and further contribute to its potent killing activity. Likely, these structures are irreversible, which can explain how low TXB doses are so effective in various animal models of infection. Since discovering TXB, we and others have failed to generate resistant mutants in any species including Mycobacterium tuberculosis. Importantly, in a recent study conducted at John Hopkins University, TXB was highly efficacious in a validated rabbit model of TB, demonstrating its promise to treat this devastating disease. TXB is in preclinical development as an intravenous (IV) drug for treating serious skin infections caused by pathogens such as MRSA. At a pre-Investigational New Drug (IND) meeting, the FDA generally agreed with our development plan, and an IND submission is planned in approximately 1.5 to 2 years. The goal of this proposal is to continue exploring TXB’s potential to treat TB. In this project, Aim 1 will produce enough TXB for all the proposed studies. Aim 2 will conduct blood and lung PK studies in mice using intranasal administration of TXB. Intranasal administration offers several advantages, including delivering the drug directly to the primary site of infection (lung) and avoiding side effects with drugs delivered systemically. Aim 3 will use the Kramnik TB mouse model to test the efficacy of intranasal TXB delivered alone and in combination with current TB drugs. Kramnik mice develop pulmonary granulomas that more closely resembled human lesions. Aim 4 will use a validated rabbit model to compare the efficacy of IV-delivered TXB alone and in combination with other TB drugs. In Aims 3 and 4, TXB drug regimens will be compared to the BPaL (bedaquiline, pretomanid, linezolid) regimen currently used for multidrug resistant TB. With successful completion of these studies, we will have demonstrated the promise of TXB for treating drug-resistant TB and explored a convenient route of administration.