To cure and control Tuberculosis (TB) disease we need shorter, simpler and safer therapies. The goal is to develop therapies of low pill burden; of shorter duration (ideally 2-3 months); with 3-4 drug regimens that avoid resistance and of limited toxicity. Today test regimens are identified in preclinical in vitro and animal models and the most promising multi-drug regimens are subsequently evaluated as a unit in clinical trials. This strategy was used to develop one of the most successful TB regimens so far; the 6moBPaL regimen (a 6-month all oral drug regimen consisting of bedaquiline (B), pretomanid (Pa) and linezolid (L)) Unfortunately, a high rate of adverse events associated with long-term administration of linezolid (a protein synthesis inhibitor) was also reported with this regimen. An option to improve the BPaL regimen is to replace L with spectinamides, another protein synthesis inhibitor without oral bioavailability but an excellent safety profile and with potent efficacy against drug sensitive (DS) and multidrug or extensively drug resistant (MDR-XDR) Mtb strains. The preclinical lead compound 1810 (backup 1599) administered in vivo as injectable, or directly into the lungs via aerosol, demonstrated potent synergistic effects with other oral TB drugs. Moving forward, we propose to develop new 3-4 drug regimens consisting of spectinamide (S) administered via aerosol and combined with BPa (aka: BPaS regimen) and BPaS in combination with pyrazinamide (Z) (aka: BPaSZ regimen). We have shown that 4-weeks of BPaS treatment resulted in similar bactericidal effect to that of the BPaL regimen in BALB/c and C3HeB/FeJ mice. Moreover, the BPaS regimen avoided the myelosuppression and anemia observed in mice treated with BPaL. Our preliminary data also suggests that sterility with BPaS is possible. The studies proposed here test inhalational therapies with spectinamides within new regimens of TB therapy for treatment of DS-TB and MDR-XDR TB. (Aim 1) We had produced small quantities of dry powder 1810 (DP1810) for inhalation and here we will manufacture and physico-chemically characterize larger scale of DP1810 and evaluate their aerodynamic performance for human or animal use. Aim 2 will use pharmacokinetics studies to determine the optimal dose level and dosing frequency for regimens BPaS and BPaSZ. Aim 3, using BALB/c and C3HeB/FeJ TB models will assess the efficacy and sterilization potential of BPaS and BPaSZ regimens. Aim 4 will develop PK/PD simulation-based allometric scaling to aid in human dose projections. Finally, in preparation for the IND preclinical package, Aim 5 will develop non- GLP toxicologic dose range finding studies in rats after inhaled DP1810 administration. Our Multi-PI team led by Dr. Gonzalez-Juarrero at CSU, Dr. Hickey from the RTI International, and Dr. Meibohm at the University of Tennessee will work together with experts in TB drug modeling, TB drug combinations and clinical pathology experts (Drs. Lyons, Robertson a...