Background: While anti-PD-1 and anti-CTLA4 immunotherapies are widely used in the treatment of metastatic melanoma, including melanoma brain metastases (MBM), their efficacy in patients with symptomatic MBM is very limited. In the Checkmate-204 trial of ipilimumab with nivolumab in MBM, the 6-month progression free survival (PFS) rate was 19% with a median PFS of only 1.2 months in symptomatic participants (those with neurological symptoms including steroids up to 4 mg/day of dexamethasone, n=18). (Tawbi, Lancet et al., 2021) In the COMBI-MB study of BRAF/MEK-inhibitors in BRAF-V600 mutant MBM, median PFS was 5.5 months in those with symptomatic metastases (n=17). (Davies et al., Lancet Oncol, 2017) The combination of anti-PD-1/PD-L1 therapy with BRAF/MEK inhibitors has been tested in various trials. The single-arm phase 2 TRICOTEL study explored the triplet regimen of vemurafenib + cobimetinib + atezolizumab in MBM; in the symptomatic brain met cohort, 6-month PFS was 57% (n=24). (Dummer et al., Lancet Oncol 2022). Methods: SWOG S2000 is a randomized phase 2 trial exploring the efficacy of a triplet regimen of BRAF/MEK inhibitors with PD-1 therapy (encorafenib 450 mg qday + binimetinib 30 mg BID + nivolumab 480 mg IV q4 weeks) versus ipilimumab 3 mg/kg + nivolumab 1 mg/kg q3 weeks in patients with symptomatic BRAF-mutant MBM. (The study was amended to exclude patients with asymptomatic MBM.) Eligible patients are ≥18 years old, ECOG 0-2, and prior neoadjuvant or adjuvant anti-PD-1, CTLA-4, or BRAF/MEK-inhibitors is permitted. Steroids up to 8 mg of dexamethasone/day (or equivalent), leptomeningeal spread, and prior local therapy (radiation or surgery) for brain mets are permitted, if a patient has at least one measurable, progressing brain met ≥0.5 cm in size. Primary objective is to compare PFS per (RECIST 1.1) between the two study arms. Secondary objectives include overall survival, toxicity profile, objective tumor response, intracranial response and duration per modified RECIST 1.1, modified RANO-BM, and iRANO criteria, and evaluation of radiographic response criteria by centralized review of banked images. This study is powered to detect an increase in estimated 6-month PFS from 20% to 52% with 80% power and type I error rate of 10%, with 24 eligible patients required. Total sample size is 28 to account for ineligible patients. Available blood, tissue, CSF and stool samples are banked for future correlative studies. The study is currently enrolling patients through SWOG, ECOG and NRG centers. Funding: NIH/NCI grants U10CA180888, U10CA180819, U10CA180820 U10CA180868; and in part by Pfizer, Inc. Clinical trial information: NCT04511013.