Background: Androgen receptor signaling inhibitors (ARSI), including APA and ABI plus prednisone, are approved for the treatment of mCSPC. However, studies evaluating survival for these agents in clinical trials or the real-world have not been investigated. This study describes real-world survival among men with mCSPC who initiated APA or ABI in the United States (US). Methods: Data from the Flatiron Metastatic Prostate Cancer (PC) Core Registry Electronic DataMart (1/1/2013–05/31/2023) was used to identify ARSI-naïve patients with chart-confirmed metastasis and without evidence of castration resistance at ARSI initiation. Patients were classified into two treatment cohorts based on the start date for APA or ABI (index date) on/after 9/17/2019. Patients had ≥12 months of clinical data pre-index and were followed from the index date until the earliest of 24 months post-index, end of clinical activity, or end of data availability. Patients’ date of death was obtained by integrating data from electronic medical records, the Social Security Death Index, and or other confirmed sources. Using an intention-to-treat approach, Kaplan-Meier analysis was used to describe the proportion of patients surviving by 24 months post-index. An unadjusted Cox proportional hazards model was used to describe crude differences in survival rates between patients initiating APA and ABI. Results: This study included 242 APA (mean age: 73.0 years; 60.3% White, 13.6% Black) and 607 ABI (mean age: 73.1 years; 57.3% White, 16.8% Black) patients. APA median time on-treatment was 11.4 months over a median observation period of 14.3 months. ABI median time on-treatment was 10.8 months over a median observation of 14.0 months. By 24 months, 85.7% of the APA cohort and 75.9% of the ABI cohort were living (unadjusted hazard ratio=0.60, 95% confidence interval: 0.38, 0.96; p=0.033; Table). Conclusions: In this study, we observed that more ARSI-naïve patients with mCSPC survived by 24 months after initiating APA than those who initiated ABI. While the current study presents unadjusted comparisons, additional causal analyses controlling for confounding variables should be conducted to confirm these initial findings.