Background: Uveal melanoma is a rare melanoma subtype with poor outcome from immune checkpoint inhibition (ICI) compared to cutaneous melanoma. UM expresses high levels of Glycoprotein 100 (Gp-100) implicating potential sensitivity to tebentafusp (tebe), a novel immune-mobilizing monoclonal T cell receptor therapy. A recent phase 3 study compared tebe to investigator chosen standard of care (SOC) with crossover at progression. SOC regimens were single agent pembrolizumab, ipilimumab and Dacarbazine with 82% of SOC patients receiving pembrolizumab¹. Other single arm studies suggest that survival with combination ICI is superior to single agent. We sought to compare overall survival (OS) of first or second line tebe in relation to combination ICI. Methods: Retrospective chart review at a single institution was conducted on patients with metastatic UM (mUM) treated with tebe on clinical trial between June 2018 and December 2021, either in first [NCT03070392] or second line [NCT02570308] setting. Patients were included if they received ipilimumab plus nivolumab either before or after tebe. Data including patient demographics and factors demonstrated in the phase 2 and 3 trials to correlate with survival including lactate dehydrogenase (LDH), size of largest liver lesion and early onset of rash with tebe were extracted. OS was the main outcome measure and was calculated as the time interval between the date of diagnosis of metastatic disease and date of death. Results: Six patients were identified in our data set as having received both ICI and Tebe, three in each sequence order. Mean characteristics were included in table. OS trended towards improvement in the cohort of patients who received tebe first in sequence both in OS in time from UM diagnosis (42.1 vs 63.5 months) (p = 0.21) and in OS in time from detection of mUM (29.8 vs 42.0 months) (p = 0.28), although neither difference was statistically significant given the small sample size. Conclusions: Our limited data demonstrate longer OS with tebe followed by combination ICI on progression compared to the reverse sequence. This comparison of patients at a single institution is underpowered to show a statistically significant OS difference but does demonstrate a trend in favor of first line tebe similar to the conclusive comparison of tebe and single agent ICI in the randomized trial. Reference: 1. Orloff, Marlana et al. Overall survival in patients who received checkpoint inhibitors after completing tebentafusp in phase 3 randomized trial of first-line metastatic uveal melanoma. (2021): 9526-9526.