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

This is a Phase I, multi-center, clinical study of XF-73 to evaluate the local (nasal) safety and tolerability of a modified, thinner, lower viscosity formulation of intranasal XF-73 in healthy male and female subjects. In addition, the potential for systemic absorption of XF-73 in the modified, thinner, lower viscosity and the previously investigated thicker, higher viscosity formulations and their decolonization efficacy in comparison to placebo will be evaluated. Both parts of the study will be double-blinded, and Part 2 will also be placebo-controlled. Study subjects will be healthy volunteers, male or female, aged 18 - 45 years. The study will be conducted in two distinct parts. In Part 1 of the study 8 healthy male and female subjects, aged 18 to 45 years, will be in two groups of four per formulation will have a study duration of up to 36 days. All subjects will receive intranasal applications of 5,15-bis-\[4-(3-Trimethylammonio-propyloxy)-phenyl\]-porphyrin dichloride (XF-73). In Part 2 only, subjects will also need to be confirmed as persistent nasal SA carriers (n = 48). (Persistent SA carriage is defined by 3 separate, SA positive cultures from nasal swabs: the first taken at Pre-Screening no more than 12 weeks (84 days). Administration will last five days, being three times a day on Day 1, then twice a day thereafter. Primary objective is to establish the safety and tolerability of two concentrations of a modified thinner, lower viscosity nasal formulation of XF-73 and to compare them to a previously investigated, thicker, higher viscosity formulation. Secondary objectives are to establish whether there is any potential systemic exposure following administration of the two nasal formulations of XF-73 and to evaluate the anti-staphylococcal efficacy of two concentrations of a lower and one of a thicker, higher viscosity nasal formulation of XF-73.