Orphan drug development in the United States.

Drug research and development in the U.S. tends to focus on drugs to treat common diseases because of the anticipated return on investment. To stimulate pharmaceutical manufacturers to pursue the development of drugs for rare conditions, the Orphan Drug Act was enacted by Congress on January 4, 1983. Under the provisions of this Act, the FDA can make recommendations on the investigations necessary for marketing approval; exclusive marketing privileges can be obtained; tax credits for expenses incurred are allowed; availability of orphan drugs on an investigational basis is encouraged; and the Orphan Product Board is established for the coordination of research efforts and their reimbursement. The effects of this legislation are evident in the continuing increase in orphan drug designations.