Background: CD73 is an ectonucleotidase that converts adenosine monophosphate to adenosine, a potent immunosuppressive soluble mediator that inhibits the cytotoxic function of CD8+ T cells and natural killer cells while promoting proliferation of immunosuppressive cells. BMS-986179 is a high-affinity antibody that inhibits CD73 enzymatic activity and downregulates its expression on tumor cells. Blockade of CD73 enhanced the antitumor activity of anti-PD-1 in preclinical models (Barnhart BC, et al. Cancer Res. 2016;76(14 suppl) [abstract 1476]). Here we describe preliminary results of the first-in-human phase 1/2a study of BMS-986179 + nivolumab (NIVO) in patients (pts) with advanced solid tumors (NCT02754141). Methods: Pts with ≥ 1 prior therapy were treated in this open-label, dose-escalation and -expansion study. Escalation began with a 2-week monotherapy lead-in, in which pts received BMS-986179 150-1600 mg IV QW followed by BMS-986179 (same dose) IV QW + NIVO 240 mg IV Q2W. Pharmacokinetics (PK), pharmacodynamics (PD), safety, and preliminary antitumor activity were evaluated. PD analyses included immunohistochemistry, enzyme activity assays in tumor biopsies, and evaluation of receptor occupancy and soluble CD73 in peripheral blood. Results: As of the Dec 19, 2017, data cutoff, 59 pts were treated with BMS-986179 ± NIVO during dose escalation. PK of BMS-986179 was nonlinear at lower doses due to target-mediated drug disposition, and exposure increased proportionally from 1200 to 1600 mg. BMS-986179 demonstrated complete and persistent CD73 target engagement in the tumor and periphery at all doses. Treatment-related AEs (TRAEs) were observed in 30 of 52 pts (58%) who received the combination, with no clear dose relationship. Only 8 pts (15%) experienced grade 3 TRAEs, and 1 discontinued treatment due to a TRAE (grade 3 increased ALT). Both the monotherapy lead-in and the combination were well tolerated, with no grade 4 TRAEs and no treatment-related deaths. BMS-986179 efficiently inhibited CD73 enzyme activity in the tumor vasculature and tumor cells at all doses, without dose dependency. Overall, 7 pts with head and neck, pancreatic, prostate, anal, and renal cancer achieved confirmed partial responses and 10 pts had stable disease. Conclusions: BMS-986179 + NIVO was well tolerated, with CD73 target engagement in the tumor and periphery and a safety profile similar to that of NIVO monotherapy. The combination demonstrated preliminary antitumor activity. These data support the ongoing evaluation of this combination in pts with advanced solid tumors. Citation Format: Lillian L. Siu, Howard Burris, Dung T. Le, Antoine Hollebecque, Neeltje Steeghs, Jean-Pierre Delord, John Hilton, Bryan Barnhart, Emanuela Sega, Kinjal Sanghavi, Anke Klippel, Cyrus Hedvat, Ed Hilt, Mark Donovan, Adrianna Gipson, Paul Basciano, Jennifer Postelnek, Yue Zhao, Raymond P. Perez, Richard D. Carvajal. Preliminary phase 1 profile of BMS-986179, an anti-CD73 antibody, in combination with nivolumab in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT180.

Purpose: The success of checkpoint blockade has led to a significant increase in the development of a broad range of immunomodulatory molecules for the treatment of cancer, including agonists against T-cell costimulatory receptors, such as OX40. Unlike checkpoint blockade, where complete and sustained receptor saturation may be required for maximal activity, the optimal dosing regimen and receptor occupancy for agonist agents is less well understood and requires further study.Experimental Design: We integrated both preclinical and clinical biomarker data sets centered on dose, exposure, receptor occupancy, receptor engagement, and downstream pharmacodynamic changes to model the optimal dose and schedule for the OX40 agonist antibody BMS-986178 alone and in combination with checkpoint blockade.Results: Administration of the ligand-blocking anti-mouse surrogate antibody OX40.23 or BMS-986178 as monotherapy or in combination with checkpoint blockade led to increased peripheral CD4 þ and CD8 þ T-cell activation in tumor-bearing mice and patients with solid tumors, respectively. OX40 receptor occupancy between 20% and 50% both in vitro and in vivo was associated with maximal enhancement of T-cell effector function by anti-OX40 treatment, whereas a receptor occupancy > 40% led to a profound loss in OX40 receptor expression, with clear implications for availability for repeat dosing.Conclusions: Our results highlight the value of an integrated translational approach applied during early clinical development to aggregate preclinical and clinical data in an effort to define the optimal dose and schedule for T-cell agonists in the clinic.

Background: Activation of OX40, a costimulatory protein in the tumor necrosis factor receptor super family, enhances T effector cell activation and inhibits T regulatory (Treg) cell-mediated suppression. Preclinical data showed that combination of an OX40 agonist with checkpoint blockade (anti-PD-1 or anti-CTLA-4) enhanced antitumor activity vs checkpoint blockade alone. BMS-986178 is a fully human IgG1 agonist monoclonal antibody that binds with high affinity to OX40 and was well tolerated ± NIVO (anti-PD-1; Olszanski AJ, et al. J Immunother Cancer 2017;5(suppl2) [abstract O17]). The relationship between receptor modulation and the activity of agonist OX40 agents in the clinic is not clear. Here we present findings on the regulation of OX40 receptor expression and T-cell activation by BMS-986178 ± NIVO or IPI (anti–CTLA-4) from the phase 1/2a study in patients with advanced solid tumors (NCT02737475). Methods: Patients with ≥ 1 prior therapy were treated in this open-label, dose-escalation and -expansion study. During escalation, patients received BMS-986178 monotherapy 20-320 mg IV Q2W, BMS-986178 20-320 mg + NIVO 240 mg IV Q2W, or BMS-986178 20-320 mg + IPI 1 mg/kg IV Q3W. Pharmacokinetics (PK) and systemic pharmacodynamics (PD) were evaluated, including analysis of OX40 receptor occupancy (RO), CD4+ T cell- and Treg-cell surface OX40 expression, soluble OX40 (sOX40) levels, cytokines, and proliferation of effector memory T cells in circulation. Results: BMS-986178 PK was linear from 20 to 320 mg when administered as monotherapy (n = 20), + NIVO (n = 38), or + IPI (n = 32). Moreover, BMS-986178 ± NIVO or IPI stimulated the production of IFN-γ and increased proliferating (Ki-67+) effector memory T cells. Concomitant downregulation of OX40 expression on the cell surface of CD4+ T cells and Tregs was observed as OX40 RO approached saturation at BMS-986178 doses of ≥ 40 mg. Furthermore, BMS-986178 doses of 20-160 mg ± NIVO or IPI increased sOX40 levels, while BMS-986178 doses of ≥ 160 mg ± NIVO or IPI led to sOX40 plateau. Conclusions: Clinical PK/PD findings showed efficient BMS-986178 target engagement and confirmed preclinical observations that BMS-986178 can modulate RO and OX40/sOX40 expression. Furthermore, peripheral T-cell activation was observed in patients treated with BMS-986178 ± NIVO or IPI. Coupled with our preclinical observations, these findings highlight a complex dose-response relationship between BMS-986178 receptor saturation, receptor modulation, and induction of soluble receptor. These data support further clinical investigation of a broader dose range and optimal schedules for BMS-986178 ± NIVO or IPI. Citation Format: Rui Wang, Yan Feng, Ed Hilt, Xiling Yuan, Chan Gao, Xiao Shao, Yongliang Sun, Michael D'silva, Katherine Yang, Becky Penhallow, Goce Bogdanoski, Rajesh Anand, Irene Pak, Danielle Greenawalt, Anke Klippel, Nataly Manjarrez-Orduno, Robert Neely, Michael Quigley, Michael Hedrick, Praveen Aanur, Z Cao. From bench to bedside: Exploring OX40 receptor modulation in a phase 1/2a study of the OX40 costimulatory agonist BMS-986178 ± nivolumab (NIVO) or ipilimumab (IPI) in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-127.

In the development of therapeutic compounds that bind cell surface molecules, it is critical to demonstrate the extent to which the drug engages its target. For cell‐associated targets, flow cytometry is well‐suited to monitor drug‐to‐target engagement through receptor occupancy assays (ROA). The technology allows for the identification of specific cell subsets within heterogeneous populations and the detection of nonabundant cellular antigens. There are numerous challenges in the design, development, and implementation of robust ROA. Among the most difficult challenges are situations where there is receptor modulation or when the target‐antigen is expressed at low levels. When the therapeutic molecules are bi‐specific and bind multiple targets, these challenges are increased. This manuscript discusses the challenges and proposes best practices for designing, optimizing, and validating ROA.

<p>Supplementary Figure 5b</p>