DS-8273

Purpose: Myeloid-derived suppressor cells (MDSC) are one of the major contributors to immune suppression in cancer. We recently have demonstrated in preclinical study that MDSCs are sensitive to TRAIL receptor 2 (TRAIL-R2) agonist. The goal of this study was to clinically test the hypothesis that targeting TRAIL-R2 can selectively eliminate MDSCs.Experimental Design: The TRAIL-R2 agonistic antibody (DS-8273a) has been tested in 16 patients with advanced cancers enrolled in a phase I trial. The antibody (24 mg/kg) was administered intravenously once every 3 weeks till disease progression, unacceptable toxicities, or withdrawal of consent. The safety and the presence of various populations of myeloid and lymphoid cells in peripheral blood and tumor tissues were evaluated.Results: The treatment was well tolerated with only mild to moderate adverse events attributable to the study drug. Treatment with DS-8273a resulted in reduction of the elevated numbers of MDSCs in the peripheral blood of most patients to the levels observed in healthy volunteers. However, in several patients, MDSCs rebounded back to the pretreatment level by day 42. In contrast, DS-8273a did not affect the number of neutrophils, monocytes, and other populations of myeloid and lymphoid cells. Decrease in MDSCs inversely correlated with the length of progression-free survival. In tumors, DS-8273a treatment resulted in a decrease of MDSCs in 50% of the patients who were able to provide pre- and on-treatment biopsies.Conclusions: Targeting TRAIL-R2 resulted in elimination of different populations of MDSCs without affecting mature myeloid or lymphoid cells. These data support the use of this antibody in combination immmunotherapy of cancer. Clin Cancer Res; 23(12); 2942–50. ©2016 AACR.

Background DR5 is a transmembrane receptor that transduces extracellular ligand-binding to activate apoptosis signaling cascades. This phase 1 study evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of a new monoclonal antibody potent DR5 agonist, DS-8273a, in subjects with advanced solid tumors. Methods The study comprised dose escalation and dose expansion cohorts. The dose escalation cohorts intended to determine the safety and to identify the maximum tolerated dose (MTD) or maximum administered dose (MAD) and to characterize the pharmacokinetics and pharmacodynamics by a conventional 3 + 3 design (starting at 2 mg/kg and escalating through 8, 16 and 24 mg/kg once every 3 weeks). In the dose expansion cohort, additional subjects were treated at the MAD for further evaluation of PK and safety. Results Thirty two subjects were enrolled and treated, 16 in the dose escalation cohorts and 16 in the dose expansion cohort. No subjects experienced a dose limiting toxicity (DLT). Treatment emergent adverse events were observed in 29 (91%) subjects, 14 (44%) of which were attributed to study-drug; all drug-related events were grade 1 and 2 in severity, and were mainly fatigue, nausea, vomiting and diarrhea. Measures of plasma exposure increased dose-proportionally and the mean terminal elimination half-life was 11 days. Blood samples available from a subset of patients treated at 24 mg/kg revealed declines in myeloid derived suppressor cells (MDSC) at 2 weeks. No objective responses were observed in any subjects. Conclusions DS-8273a was well tolerated and demonstrated linear pharmacokinetics. Decreases in MDSC were temporally associated with DS-8273a exposure. This agent could be studied further in combination with other agents, pending further proof-of-target-engagement.