This phase II study will be conducted to:

1. evaluate the pharmacokinetics, safety, tolerance, and efficacy of different dosing schedules of Posaconazole in immunocompromised hosts with a variety of refractory invasive fungal infections or in subjects who require empiric antifungal therapy and
2. identify the dosing schedule that provides the most consistent therapeutic drug exposure in this patient population.

This is an open-label, randomized, parallel group, study of pharmacokinetics, safety, tolerance, and efficacy of Posaconazole in the treatment of immunocompromised hosts with refractory invasive fungal infections or in subjects who require empiric antifungal therapy.

The projected number of subjects planned for enrollment is 100 evaluable subjects. The number of planned study sites is approximately ten in the United States and approximately eight in the rest of the world.

Inclusion Criteria:

• A proven, either probable or possible invasive fungal infection which is refractory to standard antifungal therapies.
• Subjects who received >72 hours of systemic empiric antibacterial therapy and are neutropenic (<500 neutrophils per mm3 and, have had fever that has reached an oral temperature >38c (or >100.4f)twice in the last 48 hours, or

have a recurrence of fever (oral temperature, >38c or >100.4F) while receiving broad spectrum antibacterial therapy after prior resolution of fever while on antibacterial therapy.

• Able to take oral medication or take medication via enteral feeding tube.