Data from DS-7300a, a DNA Topoisomerase I Inhibitor, DXd-Based Antibody–Drug Conjugate Targeting B7-H3, Exerts Potent Antitumor Activities in Preclinical Models

Abstract

<div>Abstract<p>B7-H3 is overexpressed in various solid tumors and has been considered as an attractive target for cancer therapy. Here, we report the development of DS-7300a, a novel B7-H3–targeting antibody–drug conjugate with a potent DNA topoisomerase I inhibitor, and its <i>in vitro</i> profile, pharmacokinetic profiles, safety profiles, and <i>in vivo</i> antitumor activities in nonclinical species.</p><p>The target specificity and species cross-reactivity of DS-7300a were assessed. Its pharmacologic activities were evaluated in several human cancer cell lines <i>in vitro</i> and xenograft mouse models, including patient-derived xenograft (PDX) mouse models <i>in vivo</i>. Pharmacokinetics was investigated in cynomolgus monkeys. Safety profiles in rats and cynomolgus monkeys were also assessed.</p><p>DS-7300a specifically bound to B7-H3 and inhibited the growth of B7-H3–expressing cancer cells, but not that of B7-H3–negative cancer cells, <i>in vitro</i>. Additionally, treatment with DS-7300a and DXd induced phosphorylated checkpoint kinase 1, a DNA damage marker, and cleaved PARP, an apoptosis marker, in cancer cells. Moreover, DS-7300a demonstrated potent <i>in vivo</i> antitumor activities in high–B7-H3 tumor xenograft models, including various tumor types of high–B7-H3 PDX models. Furthermore, DS-7300a was stable in circulation with acceptable pharmacokinetic profiles in monkeys, and well tolerated in rats and monkeys.</p><p>DS-7300a exerted potent antitumor activities against B7-H3–expressing tumors in <i>in vitro</i> and <i>in vivo</i> models, including PDX mouse models, and showed acceptable pharmacokinetic and safety profiles in nonclinical species. Therefore, DS-7300a may be effective in treating patients with B7-H3–expressing solid tumors in a clinical setting.</p></div>