Bispecific antibodies for dual-modality cancer therapy: killing two signaling cascades with one stone.

The additive and synergistic therapeutic effects derived from combinations of chemotherapeutic drugs and radiation have established an indispensable paradigm: cancer must be attacked on multiple fronts. However, the increased antitumor efficacy of such combinational regimens is also associated with severe systemic toxicity, as these drugs cannot selectively target tumor cells. Monoclonal antibodies (mAbs), which have exquisite specificity for their antigens, are becoming an increasingly important class of antitumor agents, as they enhance the efficacy of various therapeutic regimens without significantly increasing systemic toxicity. Furthermore, preclinical and early clinical evidence indicate that combinations of antibody-based drugs provide even greater efficacy with minimal side effects. Unfortunately, the research, manufacturing and regulatory costs of mAb development pose a significant barrier to the use of antibody-based combination therapies. An emerging alternative is the use of dual-targeting bispecific antibodies (BsAbs). BsAbs are derived from the recombination of variable domains of two antibodies with different specificities; BsAbs are thus capable of binding both antigens of their parental antibodies. With the recent progress that has been made in antibody engineering technology, BsAbs that simultaneously target two tumor-associated molecules (eg, growth factor receptors) are being heralded for their potential to deliver two therapeutic moieties in a single molecule.