[Bispecific antibodies in prostate cancer therapy]

Prostate cancer (PC) is the second most common cancer in men. As soon as androgen deprivation therapy fails, treatment options are limited. Despite intense efforts, hardly any of the T cell-based immunotherapeutic strategies that have revolutionized oncological treatment in other cancer entities are yet established for the treatment of PC. This includes immune checkpoint inhibition, which generally reinforces T cell-immunity but failed to achieve broad activity in PC, as well as chimeric antigen receptor T (CART) cells and bispecific antibodies (bsAbs), which specifically mobilize T cells against tumor cells. Compared to CART cells, bsAbs have the advantage of being readily available "off-the-shelf" reagents. Currently several bispecific constructs are in development for PC. While development of some was discontinued due to substantial side effects or development of anti-drug antibodies, others have yielded promising results. These include in particular bsAbs directed against six-transmembrane epithelial antigen of the prostate 1 (STEAP1) and prostate-specific membrane antigen (PSMA), which are currently being evaluated in both patients with metastasized disease and biochemical relapse. The concepts underlying the different constructs, the current status of clinical development, and future perspectives are discussed.