Abstract A081: A phase 1b, open-label, dose escalation and expansion study of demcizumab plus pembrolizumab in patients with locally advanced or metastatic solid tumors
Authors: Johnson Melissa , Rasco Drew , Schneider Brian , Shu Catherine , Jotte Robert , Parmer Hema , Stagg Robert , Lopez Juanita 
Published: August 2018

Abstract
Introduction: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway. Demcizumab is a humanized, anti-DLL4 antibody that has been shown using an in vivo tumorigenicity limiting dilution assay to inhibit tumor growth and decrease cancer stem cell frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause an antiangiogenic effect and to decrease the number of monocytic myeloid-derived suppressor cells (MDSCs) within the tumor. Finally, xenograft studies showed enhanced activity when demcizumab was combined with anti-PD1. Therefore, we hypothesized that demcizumab in combination with anti-PD1 may be effective in cancers that are refractory to anti-PD1 therapy and where MDSCs play a role in prognosis such as castrate-resistant prostate cancer and/or may augment the activity of anti-PD-1 in sensitive tumor types. Methods: This was an open-label, phase 1b dose study of demcizumab plus pembrolizumab in patients with advanced or metastatic solid tumors. Patients were enrolled in two stages: a dose-escalation stage and an expansion stage. In the dose escalation phase, patients received demcizumab 2.5 or 5 mg/kg administered IV once every 3 weeks for two 63-day truncated courses (second course starting on Day 168). Pembrolizumab was given at 2 mg/kg administered IV over 30 minutes every 3 weeks. Three cohorts of 10 patients each (anti-PD1 naïve 2L non-squamous NSCLC, anti-PD1 refractory, and advanced castrate-resistant prostate cancer) were planned to be enrolled in the dose escalation portion of the trial and treated with the MTD of demcizumab that was established in the dose escalation phase of the trial. Results: Twenty-seven patients were enrolled in the study: 9 in dose escalation and 18 in expansion. The MTD of demcizumab was determined to be 5 mg/kg (i.e., the highest dose tested). One partial response was observed in a NSCLC patient and 8 patients had stable disease. Peripheral MDSCs were measured over time in 5 of the prostate cancer patients, but no consistent impact was observed on the monocytic MDSCs. Demcizumab plus pembrolizumab was well tolerated. The most common adverse events were fatigue (44%), vomiting (41%), nausea (37%), headache (26%), BNP increased (22%), and decreased appetite (22%). Nine immune-related AEs occurred with only 2 being Grade 3 or greater. Conclusion: Demcizumab plus pembrolizumab therapy was well tolerated, but there was no evidence of enhanced antitumor activity.
Citation Format: Melissa Johnson, Drew Rasco, Brian Schneider, Catherine Shu, Robert Jotte, Hema Parmer, Robert Stagg, Juanita Lopez. A phase 1b, open-label, dose escalation and expansion study of demcizumab plus pembrolizumab in patients with locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A081.