Background: The therapeutic landscape in metastatic NSCLC has dramatically changed with approvals of immunotherapy agents in both treatment-naïve and previously treated cancer patients (pts) and irrespective of histology. Pts with tumors that develop resistance is a significant area of unmet need. Vascular endothelial growth factor (VEGF) has been shown to modulate the tumor immune microenvironment and combination immune checkpoint and VEGF/VEGF receptor inhibition have shown benefit in multiple tumor types. Lung-MAP is a master protocol for pts with stage IV, previously treated NSCLC. Pts who were not eligible for a biomarker-matched substudy enrolled in S1800A. The adverse event profile will be presented. Methods: S1800A is a phase II randomized trial for pts who previously received PD-1 or PD-L1 inhibitor therapy for at least 84 days and platinum-based doublet therapy with ECOG 0-1 stratified by PD-L1 expression, histology and intent to receive ramucirumab in the standard of care (SOC) arm. Pts were randomized 1:1 to pembrolizumab and ramucirumab P+R or SOC (docetaxel +R [SOC w R]; docetaxel, pemetrexed or gemcitabine [SOC wo R]). The primary endpoint was overall survival. Secondary endpoints included response, duration of response, investigator assessed-progression free survival and evaluation of toxicity. Results: From May 17, 2019 to November 16, 2020, 166 pts enrolled and 140 determined eligible [69 (49%) P+R; 46 (33%) SOC w R; 25 (18%) SOC wo R]. Treatments for those who received SOC wo R included 3 on docetaxel (19%); 12 on gemcitabine (75%); and on 1 on pemetrexed (6%). 131 were eligible for adverse event (AE) assessment. The most common AE were fatigue (38%), proteinuria (28%), hypertension (23%), diarrhea (22%) and hypothyroidism (22%) on P+R; fatigue (61%), anemia (48%), diarrhea (41%) and neutropenia (39%) on SOC w R and anemia (56%), leukopenia (56%), fatigue (44%) and neutropenia (44%) on SOC wo R. Grade ≥ 3 treatment-related AEs occurred in 32% of pts on P+R, 54% of pts on SOC w R and 56% of pts on SOC wo R. Cardiac and thromboembolic events occurred in 12% of pts on P+R, 11% of pts on SOC w R and 0% of pts on SOC wo R. Grade 5 AE occurred in 2 pts on P+R (respiratory failure and cardiac arrest), 3 pts on SOC w R (2 respiratory failure and sepsis) and 1 pt on SOC wo R (sepsis). Four patients were diagnosed with COVID-19 (1 on P+R and 3 on SOC) and 3 died (1 on P+R and 2 on SOC). Conclusions: Grade 3 toxicities were lower in P+R compared to SOC arms with or without R. Cardiac and thromboembolic events were similar in arms that included R. P+R was generally well-tolerated. Efficacy outcomes will be presented when data matures. Clinical trial information: NCT03971474