Research and Development Expenses — Research and development costs are expensed as incurred. Included in research and development costs are wages, benefits and other operating costs, facilities, supplies, external services and overhead related to our research and development departments, and clinical trial expenses.
Clinical trial expenses include direct costs associated with contract research organizations ("CROs"), as well as well as patient-related costs at sites at which our trials are being conducted.
Direct costs associated with our CROs are generally payable on a time and materials basis, or when certain enrollment and monitoring milestones are achieved. Expense related to a milestone is recognized in the period in which the milestone is achieved or in which we determine that it is more likely than not that it will be achieved.
The invoicing from clinical trial sites can lag several months. We accrue these site costs based on our estimate of upfront set-up costs upon the screening of the first patient at each site, and the patient related costs based on our knowledge of patient enrollment status at each site.