Association between clinical and disease characteristics and detectable or undetectable baseline ctDNA in patients with metastatic uveal melanoma.

9537 Background: Tebentafusp, a bispecific soluble TCR specific for a gp100 peptide, is licensed for the treatment of metastatic uveal melanoma (mUM) in HLA-A*02:01+ individuals. 82% of patients (pts) with mUM in the IMCgp100-102 (previously treated; 2L+) and 61% in IMCgp100-202 (frontline; 1L) studies, respectively, had detectable baseline ctDNA. There is a strong relationship between decrease in ctDNA by 9 weeks and overall survival (OS) Carvajal 2022; Hassel however, many pts with unDNA had a significant burden of metastatic disease. Baseline unDNA was associated with improved OS outcome vs detDNA in pts with 3.1-8 cm baseline metastatic deposits, but not in pts with ≤ 3cm disease. No association was seen between oncogenic background of GNAQ/GNA11/SF3B1/BAP1 and unDNA vs detDNA. Clinical trial information: NCT02570308 ; NCT03070392 . [Table: see text