Background: CIMAvax-EGF is a novel growth-factor depleting immunotherapy consisting of human recombinant EGF conjugated to recombinant P64k derived from Neisseria meningitidis, that elicits an anti-EGF antibody response, resulting in reduction of circulating EGF levels. A randomized phase 3 study of CIMAvax-EGF administered as switch maintenance therapy after first-line platinum-based chemotherapy in patients with advanced NSCLC demonstrated overall survival (OS) advantage in comparison to best supportive care alone, particularly in patients with high baseline serum EGF levels. A phase 1 trial combining CIMAvax-EGF with nivolumab, an anti-PD1 immune checkpoint inhibitor, showed that the combination is safe and appears to induce higher rate of good anti-EGF antibody response within the first 8 weeks of therapy compared to historical comparison group receiving CIMAvax-EGF alone. CIMAvax-EGF is currently being investigated in combination with pembrolizumab in a multi-arm phase II trial as 1L therapy in combination with pembrolizumab for patients with EGFR/ALK wildtype NSCLC and PD-L1 > 50% (Cohort C) and as maintenance therapy after completing 1L chemoimmunotherapy for patients with PD-L1 < 50% (Cohorts D and E). Accrual to this trial is ongoing (NCT02955290). Methods: This is an open-label, non-randomized, multi-site, phase 2 basket trial. CIMAvax-EGF (2.4 mg IM every 2 weeks x 4 doses, then every 4 weeks thereafter) is being tested as first-line therapy in combination with pembrolizumab (200 mg IV every 4 weeks) in patients with advanced NSCLC with PD-L1 ≥ 50% (Cohort C), using a Simon two stage design (n up to 41). A safety lead-in consisting of the first 6 NSCLC patients was completed. There were no G3 or higher adverse events attributed to the combination within the first 4 weeks of protocol treatment. Patients with advanced squamous NSCLC (Cohort D, n=50) and non-squamous NSCLC (without EGFR/ALK/ROS-1/KRAS mutations; Cohort E, n=45) with PD-L1 expression <50% and no evidence of progression of disease by RECIST 1.1 criteria after at least 4 cycles of induction platinum-based doublet with pembrolizumab, prior to initiation of standard of care maintenance therapy will be enrolled to receive protocol treatment with pembrolizumab in combination with CIMAvax-EGF as maintenance therapy. The primary endpoint is to evaluate objective response rate (Cohort C), and 12-month PFS in Cohorts D and E. Secondary endpoints include 12-month overall survival in all cohorts. Exploratory objectives include characterizing tissue-based immune and EGFR signaling profile as well as serum EGF levels, anti-EGF antibody levels and other blood-based biomarkers in relation to clinical outcomes. Clinical trial information: NCT02955290.