Bispecific Antibodies, Immune Checkpoint Inhibitors, and Antibody−Drug Conjugates Directing Antitumor Immune Responses: Challenges and Prospects

Tumor immunotherapy includes bispecific antibodies (BsAbs), immune checkpoint inhibitors (ICIs), vaccines, and adoptive cell immunotherapy. BsAbs belong to the family of antibodies that can specifically target two or more different antigens and are a promising option for tumor immunotherapy. Immune checkpoints are antibodies targeting PD-1, PD-L1, and CTLA4 and have demonstrated remarkable therapeutic efficacy in the treatment of hematological and solid tumors, whose combination therapies have been shown to synergistically enhance the antitumor effects of BsAbs. In addition, the clinical efficacy of existing monoclonal antibodies targeting PD-1 (e.g., ipilimumab, nivolumab, pembrolizumab, and cemiplimab) and PD-L1 (e.g., atezolizumab, avelumab, and durvalumab) could also be enhanced by conjugation to small drugs as antibody−drug conjugates (ADCs). The development of truly effective therapies for patients with treatment-resistant cancers can be achieved by optimizing the various components of ADCs.