Abstract CT004: A Phase Ib study of CD40 agonistic monoclonal antibody APX005M together with gemcitabine (Gem) and nab-paclitaxel (NP) with or without nivolumab (Nivo) in untreated metastatic ductal pancreatic adenocarcinoma (PDAC) patients

Background: Checkpoint inhibitors such as anti-PD-1 are ineffective as single agents for patients (pts) with PDAC. Preclinical data suggest that chemotherapy with agonistic CD40 antibodies can be combined with anti-PD-1 to trigger effective T cell immunity. We conducted a multi-center, open label clinical trial to evaluate the combination of APX005M with nivo and standard chemotherapy (gem and NP). Herein, we report safety and efficacy from the ongoing study. Methods: Pts with previously untreated PDAC were enrolled in 4 cohorts: Gem/NP/APX005M 0.1 mg/kg (B1), Gem/NP/APX005M 0.3 mg/kg (B2), Gem/NP/Nivo/APX005M 0.1 mg/kg (C1) and Gem/NP/Nivo/APX005M 0.3 mg/kg (C2). Primary objectives were to evaluate safety and determine the recommended Phase II dose (RP2D) of APX005M. Secondary objectives included tumor response and immune pharmacodynamics. Analyses were performed on dose-limiting toxicity (DLT)-evaluable subjects, defined as receiving 1 dose of APX005M and ≥ 2 doses of gem/NP during Cycle 1 and remaining on study through Cycle 2 Day 1. Results: N=30 pts dosed; 24 DLT-evaluable (6 per cohort). Median follow up is 32.2 weeks. N=13 (54%) pts experienced an AE leading to discontinuation, and 10 (42%) pts experienced a treatment-related serious AE. Two DLTs were observed, 1 each in cohorts B2 and C1 (grade 3 and 4 febrile neutropenia, respectively). AE rates were similar across cohorts. Four (17%) subjects died (2 each in Cohorts B1 and C1) due to disease progression (n=2) and AE (n=2, sepsis and septic shock in the setting of neutropenia). Within the DLT-evaluable population, best overall responses included 14 (58%) PR (11 confirmed, 3 unconfirmed), 8 (33%) SD, 1 (4%) PD and 1 (4%) NE. Post-baseline tumor assessments were available for 2 of the 6 DLT-inevaluable pts (best overall responses of SD and confirmed PR). Multiplexed IHC analysis of baseline tumors revealed a low CD8 T cell and high macrophage infiltrate. Analysis of circulating mutant KRAS DNA showed marked and rapid decrease with therapy in some pts. Immune profiling of PBMCs at baseline and on-treatment by CyTOF revealed remodeling of the myeloid compartment in response to treatment, with rapid activation of dendritic cells in most pts. Conclusions: Gem/NP/APX005M ± nivo demonstrated manageable safety profiles and promising antitumor activity in untreated metastatic PDAC pts. APX005M 0.3 mg/kg was selected as the dose for a randomized Phase II study in which the primary endpoint is 1-year overall survival. Clinical trial information: NCT02482168. Citation Format: Mark H. O9Hara, Eileen M. O9Reilly, Mick Rosemarie, Gauri Varadhachary, Zev A. Wainberg, Andrew Ko, George A. Fisher, Osama Rahma, Jaclyn P. Lyman, Christopher R. Cabanski, Erica L. Carpenter, Travis Hollmann, Pier Federico Gherardini, Lacey Kitch, Cheryl Selinsky, Theresa LaVallee, Ovid C. Trifan, Ute Dugan, Vanessa M. Hubbard-Lucey, Robert H. Vonderheide. A Phase Ib study of CD40 agonistic monoclonal antibody APX005M together with gemcitabine (Gem) and nab-paclitaxel (NP) with or without nivolumab (Nivo) in untreated metastatic ductal pancreatic adenocarcinoma (PDAC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT004.