Background: In patients with previously untreated aRCC, A + Ax combination therapy has shown superior progression-free survival (PFS) and objective response rate (ORR) vs sunitinib across all International Metastatic RCC Database Consortium (IMDC) risk groups. This study reports real-world outcomes at up to 36 months post treatment initiation in patients with aRCC receiving A + Ax in the UK. Methods: Retrospective data were collected from medical records of patients aged ≥18 years diagnosed with aRCC, who initiated A + Ax on or after August 1, 2019, via the Early Access to Medicines Scheme at 10 UK sites. Patients were followed until July 31, 2023. Primary endpoints were overall survival (OS), PFS, ORR, and best response at 36 months post A + Ax initiation. Data were analyzed descriptively. Results: 130 patients were included. Median age at baseline was 67.1 years (range, 38.5-87.0 years); 74% (n=96) were male; 69% (n=90) were White, 4% (n=5) were Asian/Asian British, and ethnicity was not recorded in 27% (n=35); 94% (n=122) had an Eastern Cooperative Oncology Group score of 0 or 1. IMDC risk status was favorable in 39% (n=51), intermediate in 40% (n=51), and poor in 19% (n=25). Median time from aRCC diagnosis to A + Ax initiation was 2.5 months (range, 0.03-115.4 months). Clear cell histology was the most prevalent (88%; n=115); 68% (n=88) had undergone nephrectomy, and 78% (n=102) had 1 or 2 metastatic sites at index. The OS rate (95% CI) at 12, 24, and 36 months was 81.5% (75.1%-88.5%), 65.3% (57.6%-74.0%), and 53% (45.2%-62.9%), respectively. The PFS rate (95% CI) at 12, 24, and 36 months was 53.1% (45.1%-62.5%), 36.4% (29.0%-45.8%), and 27% (20.3%-36.0%), respectively. Median PFS was 13.5 months (95% CI, 10.2-17.7 months). ORR (n=127) at 36 months was 62% (95% CI, 53.8%-70.6%), including a best response of complete response (CR) in 5% (n=6) and partial response (PR) in 57% (n=73); best response was stable disease in 31% (n=39) and progressive disease in 7% (n=9; best response was not recorded in 3 patients). Median duration of response was 14.9 months (95% CI, 12.0-23.5). Median time to discontinuation (TTD) of A or Ax was 11.7 months (95% CI, 9.0-17.6), and for A + Ax combined was 14.7 months (95% CI, 11.0-24.4). Adverse events (AEs) were reported in 68% (88/129) of patients, who had a total of 519 nonserious AEs due to A + Ax treatment; 13% (17/129) of patients had a total of 27 serious AEs. The most common AEs (number of patients) were diarrhea (n=49), fatigue (n=33), and oral mucositis (n=24); 9 patients discontinued A and/or Ax due to AEs, including diarrhea in 3 patients. Conclusions: In this UK-based real-world study of first-line A + Ax treatment in patients with aRCC, OS, PFS, ORR, and best response observed at 36 months were in line with findings from clinical trials, with no newly emerging AEs.