Amgen has entered an exclusive licensing agreement to develop and commercialize Kyowa Hakko Kogyo Co.’s humanized monoclonal antibody KW-0761 worldwide, except in Japan, Korea, China and Taiwan, where Kyowa Hakko will retain development and commercialization rights.     Under the terms of the agreement, Amgen will make an upfront payment to Kyowa Hakko of $100 million. Kyowa Hakko could receive as much as $420 million in additional payments, including development, approval and sales mil...