Tan, Alan

4516 Background: Ipilimumab/nivolumab (ipi/nivo) is a standard of care first-line treatment (tx) for patients (pts) with mccRCC; however, ideal timing of subsequent immunotherapy txs are not well defined. We performed an analysis of patients initially treated with ipi/nivo and subsequent cohort assignments on PDIGREE (A031704). Methods: The PDIGREE trial treated pts with IMDC intermediate/poor risk mccRCC with first-line ipi/nivo (Step 1) at NCTN sites (categorized as academic (A), academic regional (R), and community (C)). Subsequent management was based on iRECIST responses at 12 weeks: pts with complete response (CR) received 1-year nivo maintenance; pts with progressive disease (PD) received cabozantinib (cabo) monotherapy, pts with non-CR/non-PD were randomized to nivo with or without cabo (for primary endpoint of overall survival [OS], target sample size was 1175). Enrollment was held when the randomized sample target was reached. Pts with unresolved toxicity at week 22 were managed off protocol. Step 1 pt demographics, assignments into Step 2, and adverse event (AE) data are presented. Descriptive statistics were used, and cohorts were compared using a chi-square test. These data were released with DSMB approval and do not inform the primary OS endpoint (1EP). Results: From May 2019 to May 2024, 1111 pts were enrolled and treated with ipi/nivo. Pt characteristics included median age 64.0 years (range 29.0-86.0); 819 (73.7%) males; White (85.1%), Hispanic (10.4%), Black (4.2%), and American Indian/Native Hawaiian (1.3%); 849 (76.8%) intermediate risk/257 (23.2%) poor risk; 458 (41.2%) at Academic, 113 (10.2%) at Regional, and 540 (48.6%) at Community centers; and 603 (54.3%) with de novo metastases. 364 pts (33%) stopped tx in Step 1: 160 (44%) for AEs, 46 (13%) for PD/clinical PD/suspected PD, 42 (12%) withdrawals, 39 (11%) alternative txs, 37 (10%) deaths on the study, 12 (3%) other complicating disease, 8 (2%) MD decision and 19 (5%) other reasons. Of the 37 deaths, 15 (1.4%) grade 5 SAEs were reported, 6 of which were due to PD. Of 747 (67%) pts registered to Step 2 at 3 months, 9 (1.2%) achieved CR, and 141 (18.9%) pts were assigned to the PD cohort. 597 pts (80%) were randomized for the 1EP, notable with fewer pts with poor risk [(21 vs 27%, p = 0.01] and bone metastases [24.5% vs 34.2%, p = 0.0007] compared to Step 1 pts who discontinued tx. Gr 3/4 tx-related AEs in 314/1093 (29%) evaluable pts included diarrhea/colitis (8%), transaminase elevation (3%), rash (2%), adrenal insufficiency (2%), fatigue (2%), and hypophysitis (1%). Conclusions: The PDIGREE trial enrolled a representative US-based population with mccRCC. Step 1 pt characteristics and associated outcomes with induction ipi/nivo reveal new insights into the tolerability and tx response of 1L ipi/nivo. Clinical trial information: NCT03793166 .