Drug development comprises all the activities involved in transforming a compound from drug candidate (the end-product of the discovery phase) to a product approved for marketing by the appropriate regulatory authorities. Efficiency in drug development is critical for commercial success, for two main reasons: Development accounts for about two-thirds of the total R&D costs. The cost per project is very much greater in the development phase, and increases sharply as the project moves into the later phases of clinical development. Keeping these costs under control is a major concern for management. Failure of a compound late in development represents a lot of money wasted. Speed in development is an important factor in determining sales revenue, as time spent in development detracts from the period of patent protection once the drug goes to market. As soon as the patent expires, generic competition sharply reduces sales revenue.