What is the fine-grained topic of the following text: We have accumulated an extensive patent portfolio in the course of our research in the areas of Multivalent Bispecific Antibodies, F-18 Labeling, DOCK-AND-LOCK™, Antibody-Drug Conjugates, Antibody-Drug Conjugate Linker, and T-cell Redirecting Antibodies, which we believe constitutes a very valuable business asset. Only return the topic.
Patent portfolio in biomedical research