Novel tetravalent bispecific antibody, PSMA/TRAIL‑R2 REGULGENT™, induces selective tumor cell apoptosis without hepatotoxicity.

Tumor necrosis factor‑related apoptosis‑inducing ligand‑receptor 2 (TRAIL‑R2) can induce apoptosis in various tumors through the oligomerization of TRAIL. Several TRAIL‑R2 agonistic monoclonal antibodies have been tested in clinical trials but have failed owing to a lack of efficacy or severe hepatotoxicity. Although bispecific constructs have been developed to improve TRAIL‑R2 targeting and enhance efficacy against tumors while reducing adverse effects on hepatocytes, the risk of hepatotoxicity still persists. The present study used a TRAIL‑R2 antibody, E11, that does not trigger apoptosis in the absence of crosslinking and constructed a novel tetravalent bispecific IgG4‑based antibody, REGULGENT™, comprised of E11 and a clone that binds to prostate‑specific membrane antigen (PSMA), a specific marker for prostate tumors. PSMA/TRAIL‑R2 REGULGENT™ selectively induced death in PSMA/TRAIL‑R2 double‑positive cells but not in TRAIL‑R2 single‑positive cells in vitro and in vivo. By contrast, a bivalent bispecific antibody did not result in tumor cell death, indicating that tetravalent bispecific antibodies have an important role in inducing tumor cell apoptosis by binding to TRAIL‑R2 in a bivalent manner. Moreover, the present study demonstrated, for the first time to the best of the authors' knowledge, that PSMA/TRAIL‑R2 REGULGENT™ is not hepatotoxic in vitro (primary human hepatocytes) or in vivo (chimeric human hepatocyte‑transplanted PXB mouse model). This finding suggests that tetravalent bispecific therapeutics such as REGULGENT™ can be promising therapeutic agents for TRAIL‑R2‑positive tumors by exerting tumor‑specific activity while avoiding toxicity.