NHT101, amphotericin B (AMB) powder/DryNeb (a novel, active dry powder nebulizer), is being developed for fungal lung disease. Two studies were performed, 1) NHT101 in vitro aerosol testing, and 2) AMB efficacy-safety. AMB was micronized to ?4 ?m [D(v90)]. 1):A mesh covered chamber with AMB and 2 PTFE-magnetic bars were inserted above a motor to generate dynamic motion and AMB aerosol clouds. The latter was entrained in airflow directed to a mouthpiece driven by negative pressure approximating tidal inspiration. Aerodynamic particle sizes were 3.5-4.5/1-2?m MMAD/GSD. 2):Guinea Pigs (GP) were exposed to AMB aerosols (1mg/L; 1.67/2.84um MMAD/GSD) by nose only inhalation. Days 1, 4, and 7 were AMB exposure days. Air controls were included. GP were sacrificed on Day 8. Daily AMB average pulmonary dose was calculated at 3.76 mg/kg. For safety, 3m/3f GP were exposed to AMB and 2m/2f to air. Lungs were assayed for AMB and preserved for histopathology. For efficacy, 16m GP (8 air and 8 AMB) were challenged with a pulmonary dose of 0.67×10⁵ aerosolized Aspergillus fumigatus (AF) conidia/kg on Day 0. Lung burden was performed Day 8. For safety, AMB caused non-adverse minimal-mild increases in lung macrophages and mixed cell inflammation. Lung AMB was ~40ug/g at sacrifice. For efficacy, of air AF GP, 1 was found dead and 2 moribund on Day 8 prior to scheduled sacrifice (survival rate of 62.5%). All AMB GP survived to necropsy. Fungal burden was higher in air GP (mean ~1000 CFU/g lung) vs AMB GP (mean ~20 CFU/g). Conclusion: NHT101 has optimal clinical aerosol characteristics. Inhaled AMB was protective in a stringent GP AF model. NHT101 possesses clinical feasibility for the treatment of fungal lung diseases.