BiTE drugs fuse an antibody onto a molecule that attracts immune system cells called T cells to attack tumor cells. Distinct antibodies can be used to target drugs to different tumor types, which explains Micromet's multiple partnerships. And of course immunotherapies are hot after the success of Dendreon 's (Nasdaq: DNDN) Provenge and Bristol-Myers Squibb 's (NYSE: BMY) Yervoy.