A novel bispecific antibody as an immunotherapeutic agent in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) remains one of the most common and highly fatal malignancies in humans worldwide with increasing prevalence and limited therapeutic options. For many decades, many researchers have attempted to find effective curative methods for HCC and great strides have been made. GPC3 is overexpressed in HCC, but not in normal liver, making it a rational immunotherapeutic target for HCC. GC33, a humanized mAb directed against GPC3, is a safe and well-tolerated therapy choice for patients with HCC, which tested in a phase I trial in advanced HCC patients. Phase II trials of GC33 to evaluate its efficacy and safety in advanced or metastatic HCC, showed no significant differences in overall survival and progression-free survival compared with the placebo. Retrospective analysis indicates that high drug exposure and high CD16 expression may contribute to the clinical efficacy of GC33. Chugai Pharmaceutical has restarted its Phase I trial of GC33, continuing to explore its clinical value targeting GPC3 in solid tumors. To enhance the antitumor potency of GC33, we designed a GPC3/CD16A bispecific antibody (QDEB). In this study, we obtained QDEB at high purity and assessed its effectiveness in the therapy of HCC compared with GC33. In vitro cytotoxicity assays and in vivo experiments demonstrated that QDEB could enhance anti-tumor efficacy compared with GC33. CD16A activation and increased cytokines release were associated with higher anti-tumor activity. In conclusion, this bispecific antibody may possibly help develop new therapeutic strategies for HCC and develop new treatment options in the future.