Study of the Safety and Local Tolerability of Intranasal Gel Formulations of XF-73

Placebo: 4% Klucel® gel formulation, concentration 0, total daily volume 1.8 ml, 3 doses 8 hours apart on Day 1 and 1.2 ml, 2 doses 12 hrs apart on Days 2 to 5.

XF-73 in a modified 2% Klucel® gel formulation: Part 1, #1: concentration 0.5 mg/g, twice a day in volume 0.3 mL/naris/dose, total dose 0.6 mg; Part 1, #2: 2.0 mg/g concentration, twice a day in volume 0.3 mL/naris/dose, total dose 2.4 mg; Part 2, #1: Concentration 0.5 mg/g, 3 doses 8 hours apart on Day 1, total volume 1.8 ml, total dose 0.9 mg, 2 doses 12 hours apart on Days 2-5, total volume 1.2 ml and total dose 0.6 mg ; Part 2, #2: 2.0 mg/g, 3 doses 8 hours apart on Day 1, total volume 1.8 ml, total dose 3.6 mg, 2 doses 12 hours apart on Days 2-5,total volume 1.2 ml and total dose 2.4 mg.

XF-73 in a 4% Klucel® gel formulation: Part 2 #3: concentration of 0.5 mg/g and volume of 0.3 mL/naris/dose in 3 doses 8 hours apart on Day 1 and 2 doses, 12 hours apart on Days 2 to 5. Total daily volume of 1.8 ml on Day 1 and 1.2 ml on Days 2 to 5; and total daily dose of 0.9 mg on Day 1 and 0.6 mg on Days 2 to 5.