Madueke, Ikenna

481 Background: EV is an anti-Nectin-4 antibody-drug conjugate that has been approved by the US FDA for mUC progressing on platinum and PD1/L1 inhibitor therapy and in cisplatin-ineligible pts following prior therapy. However, prognostic and predictive biomarkers in the setting of EV therapy are unclear. We aimed to investigate baseline and early changes in commonly available clinical and laboratory tests that could help predict survival and toxicities in patients with mUC treated with EV. Methods: Data from patients with mUC who were treated with EV at Dana Farber Cancer Institute between 2017 and 2021 were reviewed retrospectively. We assessed the association of demographic (age, sex), clinical (ECOG-performance status [PS], sites of metastasis) and laboratory variables (hemoglobin, RDW, neutrophil count, lymphocyte count, neutrophil-to-lymphocyte ratio, platelet count and serum albumin) at baseline as well as after 4-7 weeks of treatment with Overall Survival (OS) by constructing univariate and multivariable Cox proportional-hazards models. Any variables significantly associated with OS at the univariate level (using an alpha-level of 0.1 to determine statistical significance) were then entered into the multivariable model. Predictors were eliminated from the final multivariable models by a backward selection process, retaining only those with a p-value of ≤ 0.05. Results: A total of 49 patients who received EV were included in the analysis. The median age was 72 years (range 48-88) and 36 (73.5%) were male. The median OS was 13.3 months (range: 2.7-38.7) and grade 3-4 toxicities were seen in 11 pts (22.4%). In the final multivariable models, lower serum albumin at 4-7 weeks (HR = 0.18; 95% CI = 0.05-0.71; p = 0.015), and baseline ECOG-PS of 1 vs. 0 (HR = 2.56; 95% CI = 1.05-6.21; p = 0.038) were significantly associated with worse OS (Table). Patients with higher serum albumin levels at 4-7 weeks also had significantly lower odds of experiencing grade 3-4 adverse events on EV (OR = 0.05; 95% CI = 0.002-0.52; p = 0.02). Conclusions: Lower serum albumin appeared to predict worse survival and severe toxicities in mUC pts receiving EV. This information may guide therapy and assist in the prevention of toxicities. Additionally, ECOG-PS was prognostic while the location of metastatic disease was not prognostic in the setting of EV.[Table: see text]