142 Background: T-VEC, a modified oncolytic herpes virus, is an intralesional therapy for unresectable advanced melanoma. COSMUS-1, a recently presented observational chart review study from 7 US academic sites, described metastatic melanoma treatment (tx) patterns and safety of T-VEC in the real-world setting (Perez et al, SMR 2018). In this analysis, we evaluated T-VEC use in pts after prior CPI use or with CPI from COSMUS-1. Methods: Of 76 pts treated with T-VEC (first dose 27Nov2015-15Dec2016), 33 pts had received pembrolizumab, nivolumab and/or ipilimumab (ie, CPI) prior to or with T-VEC and were analyzed for demographics, clinicopathologic characteristics, outcomes, and adverse events. Two groups were identified: Group A, CPI then T-VEC only and Group B, CPI with T-VEC. Results: There were 21 pts in A and 12 pts in B; in B, all received TVEC + CPI with (1) prior CPI, n = 5, (2) prior CPI and additional CPI after combination, n = 1, (3) as combination only, n = 4, or (4) as combination followed by CPI only, n = 2. In A and B, respectively, mean age was 72 yrs and 63 yrs; 12 (57%) and 9 (75%) were men; 17 (81%) and 9 (75%) had ECOG 0-1,10 (48%) and 4 (33%) had Stage IIIB-IVM1a, and 11 (52%) and 7 (58%) had Stage IVM1b/c. Two pts (both in B) remained on T-VEC by study end. 21 (100%) pts in A and 10 (83%) pts in B discontinued T-VEC (most common, respectively: 10 pts and 3 pts due to disease progression, 4 pts and 2 pts due to physician decision). 2 pts had no injectable lesions left (in A) and 1 pt (in A) had pathologic complete response (CR). Adverse events of interest were reported in 7 pts (33%) in A and 6 pts (50%) in B; most common events in A and B, respectively, were immune-mediated events (n = 3 and 6) which included flu-like symptoms (fever, chills, rigor; n = 2 and 5) and injection site complications (n = 5 and 2). No herpetic infections were reported in pts. Conclusions: These real-world data suggest that T-VEC is well tolerated and can be administered in pts previously treated with a CPI, both those who switched to T-VEC or those where T-VEC was added on. One pt achieved a pathologic CR.