Abstract Introduction: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway, which is important for cancer stem cell (CSC) survival. 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 CSC frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause dysfunctional sprouting of new vessels, resulting in an antiangiogenic effect. Data from a phase 1b study of carboplatin (C), pemetrexed (P), and demcizumab (D) in patients with 1st-line metastatic non-squamous NSCLC led to this double-blind randomized 3-arm placebo (Pl)-controlled phase 2 study. Methods: Patients with non-squamous NSCLC were randomized (1:1:1) to 1st-line therapy with either Arm 1 -CPPl, Arm 2 -CPD with a single 70-day truncated course of demcizumab or Arm 3 - CPD with two 70-day truncated courses of demcizumab (second course starting on Day 168). CP were given at usual dose and schedule; P/D was given IV on days 1 and 15 in cycles 1-3 and 7-9. The primary endpoint was response rate and secondary endpoints included progression-free survival, survival, safety, immunogenicity, pharmacokinetics, and biomarkers of Notch signaling and CSCs in blood, hair follicles, and tumor cells. The primary study analyses compared CPPl to the two pooled CPD arms. Results: 82 patients were randomized and all 82 were treated. The median age was 61, the male/female ratio was 40/42, 80 pts had adenocarcinoma, 0 pts harbored EGFR mutation or ALK rearrangement, and 15 were KRAS mutated. The response/clinical benefit rates were 52%/92% and 28%/79% in the CPPl and pooled CPD arms, respectively (response p value = 0.04). The median progression-free survival (PFS) was 8.7 months (95% CI: 5.4-12.5) in the CPPl arm and 5.5 months (95% CI: 4.1-6.9) in the pooled CPD arms (HR = 2.3; 95%CI: 1.1-4.8). The interim median overall survival (OS) for the CPPl and pooled CPD arms was not reached (95% CI: 16.0—NR) and 15.5 months (95% CI: 8.3-NR) (HR= 2.4; 95% CI: 0.94-6.1), respectively. CPD was generally well tolerated with nausea, fatigue, constipation, anemia, and hypertension being the most common reported toxicities. The incidences of the Grade 3 or greater toxicities of special interest with demcizumab therapy were hypertension (8% vs 25%), pulmonary hypertension (0% vs 0%), heart failure (0% vs. 0%), and bleeding (0% vs. 3.4%) in the CPPl and pooled CPD arms, respectively. Conclusions: The addition of either 1 or 2 truncated courses of demcizumab to 1st-line carboplatin and pemetrexed did not improve the efficacy compared to CPPl in patients with 1st-line metastatic NSCLC. CPD therapy was generally well tolerated. Citation Format: Brett Hughes, Andrew Dean, Ben Markman, Luke Dreisbach, Mariano Provencio, Libero Ciuffreda, Rachel Dear, Peter Graze, Alforia Nadal, Baerin Houghton, Teresa Moran, Rachel Roberts, Grace Dy, Taus Alvaro, Alex Martinez Marti, Rainer Brachmann, Robert Stagg, Ramaswamy Govindan. DENALI: a 3-arm double-blind randomized phase 2 study of carboplatin, pemetrexed, and placebo (CPP) versus carboplatin, pemetrexed, and either 1 or 2 truncated courses of demcizumab (CPD) in patients with non-squamous non-small cell lung cancer (NSCLC) [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 A084.