Background: Despite advances in therapy of clear cell renal cell carcinoma, outcomes for patients with aRCCVH remain poor and these patients have typically been excluded from pivotal phase III studies. COSMIC-313 (NCT03937219) exploring C/N/I vs N/I excludes those with aRCCVH. Given responses seen with C as well as N/I in aRCCVH, there is reason to explore this triplet combination in this population. Methods: NCT04413123 is single arm phase 2 trial multi-institutional study involving Dana-Farber Cancer Institute, Beth Israel Deaconess Medical Center, Winship Cancer Institute, Karmanos Cancer Center, University of California in San Diego and University of Texas Southwestern. The primary objective is to assess the objective response rate (ORR) by investigator-assessed Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 of C in combination with N/I in aRCCVH. Key secondary endpoints are progression-free survival (PFS), overall survival (OS) and toxicity by Common Terminology Criteria for Adverse Events (CTCAE) version 5. Mandatory pretreatment biopsy (unless medically infeasible) is required for correlative analysis to define the composition and transcriptional states of tumor and immune cells within the aRCCVH microenvironment in addition to determining the number and state of tumor-infiltrating T cell clones in aRCCVH and relation to response. Any variant histology is allowed, including clear-cell RCC with over 80% sarcomatoid features. Patients may be treatment naïve or received prior therapy including up to one anti-vascular endothelial growth factor agent not including C; prior therapy with immune checkpoint inhibitors is exclusionary. All International Metastatic RCC Database Consortium risk classifications are allowed; patients should have adequate organ function with performance status 0-1. C will be administered at a starting dose of 40 mg daily. N will be dosed at 3 mg/kg with I 1 mg/kg every 3 weeks followed by maintenance N 480 mg IV every 4 weeks and will be continued until progressive disease or unacceptable toxicity. C can be reduced to. 20 mg daily or 20 mg every other day as needed for toxicity. Dose reductions of N or I are not permitted but delays up to 12 weeks are allowed; N may be continued without I if toxicity can be directly attributed to I. Radiographic imaging is performed at baseline with first scheduled assessment at 12 weeks then every 8 weeks thereafter. A one-stage design is employed to enroll 40 eligible patients, which provides 93% power at 1-sided alpha of 0.09 to distinguish an ORR of 40% versus 20%. 12 or more responses are required to deem treatment promising. Seven of the planned 40 patients have been enrolled as of 2/1/2021. Clinical trial information: NCT04413123