2587 Background: ICIs have now become standard of care treatment for multiple malignancies. However, patients (pts) who are African American decent (AA), have a poor ECOG performance status (PS) or chronic viral infections [human immunodeficiency virus (HIV), hepatitis B (HBV) and hepatitis C (HCV)] were underrepresented in early clinical trials with ICIs and outcome data in these pt populations is not well reported. Methods: We performed a retrospective analysis of pts treated with ICIs (anti-PD(L)-1, anti-CTLA-4, or combination ICIs) across five MedStar Health hospitals from January 2011 to April 2018. Investigator-assessed best responses were noted. CTCAE v4.03 was used to capture immune-related adverse events (irAEs). Results: We identified 765 pts treated with 829 unique ICIs therapies across different malignancies. A total of 203 AA pts, 178 pts with a pre-treatment ECOG PS ≥2, 21pts with HIV, and 50 pts with HBV/HCV were noted. Any grade and grade ≥ 3 irAEs in the HIV cohort were 24% and 10% with an ORR of 29%. Any grade and grade ≥ 3 irAEs in HBV/HCV were 50% and 26% with an ORR of 21%. No viral reactivation or changes in pts anti-viral medications were noted during ICIs treatment. The ORR in AA pts was 35%. Any grade and grade ≥ 3 irAEs in the AA cohort were 27% and 8%, respectively. The ORR in pts with ECOG PS ≥2 was 14%. Any grade and grade ≥ 3 irAEs in this cohort were 20% and 4%. Similar trends were seen in the subset of patients with NSCLC treated with anti-PD(L)1 monotherapy (Table). Outcomes of NSCLC pts treated with anti-PD(L)-1 monotherapy. Conclusions: ICI therapy was not associated with any new safety signal in the above underrepresented populations. Prospective studies are needed to validate this data.[Table: see text]