Our revenues to date have been generated primarily from milestone payments under current and previously existing out-licensing agreements.
We expect our revenues for the next several years to be derived primarily from payments under our current out-licensing agreement with Omega Pharma, our collaboration agreement with Novartis and other potential collaboration arrangements, including future royalties on product sales. To date, we have not recorded material revenues from our collaboration with Omega Pharma, but we expect revenues to gradually increase as the product launch expands.
Research and Development
Our research and development expenses consist primarily of salaries and related personnel expenses, fees paid to external service providers, up-front and milestone payments under our license agreements, patent-related legal fees, costs of preclinical studies and clinical trials, drug and laboratory supplies and costs for facilities and equipment. We primarily use external service providers to manufacture our product candidates for clinical trials and for the majority of our preclinical and clinical development work. We charge all research and development expenses to operations as they are incurred. We expect our research and development expense to remain our primary expense in the near future as we continue to develop our therapeutic candidates.