Motoko Nagata

Raludotatug Deruxtecan, a CDH6-Targeting Antibody–Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models

Abstract Cadherin-6 (CDH6) is expressed in several cancer types, but no CDH6-targeted therapy is currently clinically available. Here, we generated raludotatug deruxtecan (R-DXd; DS-6000), a novel CDH6-targeting antibody–drug conjugate with a potent DNA topoisomerase I inhibitor, and evaluated its properties, pharmacologic activities, and safety profile. In vitro pharmacologic activities and the mechanisms of action of R-DXd were assessed in serous-type ovarian cancer and renal cell carcinoma cell lines. In vivo pharmacologic activities were evaluated with several human cancer cell lines and patient-derived xenograft mouse models. The safety profile in cynomolgus monkeys was also assessed. R-DXd exhibited CDH6 expression-dependent cell growth-inhibitory activity and induced tumor regression in xenograft models. In this process, R-DXd specifically bound to CDH6, was internalized into cancer cells, and then translocated to the lysosome. The DXd released from R-DXd induced the phosphorylation of Chk1, a DNA damage marker, and cleaved caspase-3, an apoptosis marker, in cancer cells. It was also confirmed that the DXd payload had a bystander effect, passing through the cell membrane and impacting surrounding cells. The safety profile of R-DXd was favorable and the highest non-severely toxic dose was 30 mg/kg in cynomolgus monkeys. R-DXd demonstrated potent antitumor activity against CDH6-expressing tumors in mice and an acceptable safety profile in monkeys. These findings indicate the potential of R-DXd as a new treatment option for patients with CDH6-expressing serous-type ovarian cancer and renal cell carcinoma in a clinical setting.

Human epidermal growth factor receptor 3 expression in patients with epithelial ovarian cancer: a potential target for ovarian mucinous and clear cell carcinoma

Human epidermal growth factor receptor 3 (HER3), a tyrosine kinase belonging to the HER family, is a known target for cancer therapy; recently, an anti-HER3 antibody-drug conjugate (ADC) is developing. To understand HER3 expression in epithelial ovarian cancer (EOC), this study was conducted. We investigated the expression of HER3 in 202 patients with EOC using immunohistochemistry (IHC), and the association between HER3 expression, clinicopathological features, prognosis, and treatment timing. Of all the cases, 55.4% had a HER3 IHC score ≥ 1 + . In particular, 78.0% of the patients with clear cell carcinoma (CCC) and 87.9% of the patients with mucinous carcinoma (MC) had a HER3 IHC score ≥ 1 + . Regarding clinicopathological features, early disease stage, feasibility of primary debulking surgery, no residual tumor, and low CA125 levels were more frequently observed in patients with a HER3 IHC score ≥ 1 + . Furthermore, a HER3 no-expression showed a significant association with a relatively short progression-free survival (PFS). And, for patients with mucinous carcinoma, those with a HER3 IHC score ≥ 1 + had poorer PFS and overall survival than those with a HER3 no-expression (no statistically significant difference). In addition, we analyzed HER3 expression at primary tumor and recurrence tumor in same patients. Thus, we observed the HER3 IHC score tended to change from 0 to ≥ 1 + in recurrence cases compared with primary cases. These observations suggested that patients with MC, CCC and recurrence of all histological type may potentially benefit from future clinical trials of HER3-directed therapies.