Germany's Affimed has inked a deal that makes it the latest in a long string of biotechs to partner up with Merck ($MRK) on a combination study using the PD-1 blockbuster Keytruda. Affimed is underwriting a Phase Ib study that combined its drug AFM13 with Keytruda against Hodgkin lymphoma. AFM13 is a bispecific antibody that is designed to engage NK (natural killer) cells. And Affimed has rights to spring forward into Phase III, if the data look right. Release