 Navidea Biopharmaceuticals, Inc. NYSE American: NAVB Navidea or the Company, a company focused on the development of precision immunodiagnostic agents and immunotherapeutics, today announced that on March 17, 2020 the U.S. Patent and Trademark Office USPTO issued a Certificate to extend the duration of U.S. patent 6,409,990 for an additional five years through May 12, 2025. This Certificate was based on the U.S. Food and Drug Administrations FDA recommendation for a five-year extension under the Hatch-Waxman Act for patent term lost in regulatory review. 