Background: Anti-PD-(L)1 immunotherapy improves outcomes for patients across various cancers; however, many patients do not benefit. Previous studies combining multi-site SBRT with anti-PD1 have confirmed feasibility and revealed induction of interferon signaling by SBRT. Elevated levels of serum IL8 (sIL8) associate with lack of response to anti-PD1 and we have observed that elevated IL8 is strongly associated with lack of response to immunotherapy and SBRT combinations. Overcoming IL8 induced epithelial-mesenchymal transitioning and trafficking of myeloid derived suppressor cells in tumor microenvironment therefore represents a promising strategy to overcome resistance. BMS-986253 is a fully human neutralizing antibody that binds to sIL8. The combination of BMS-986253 and nivolumab was safe in patients with advanced solid tumors. The present study aims to evaluate safety and preliminary efficacy of combining BMS-986253 with nivolumab and SBRT in patients with advanced solid tumors, Melanoma (MEL) and Renal Cell Carcinoma (RCC). Methods: This is a phase 1 open label single arm study (CT.gov: NCT04572451) which will include safety and efficacy cohorts. Patients will receive SBRT in 1-4 tumor lesions, in 3 or 5 fractions, at the total of 30 or 45 or 50 Gy based on the irradiated organ site. This will be followed by intravenous (IV) nivolumab (480mg q4 weeks (W)) and IV BMS-986253 (2400mg q2W) within seven days of completing SBRT. In the initial safety portion of the clinical trial, we will include 30 patients with advanced/metastatic solid tumors in order to evaluate safety. The primary endpoint of dose limiting toxicity will be assessed by continual Bayesian monitoring. The toxicities will be attributed to combination of SBRT/Immunotherapy as opposed to individual components. The secondary objective of the study is efficacy with an endpoint of objective response rate (ORR) as assessed by RECIST v1.1 in Mel and RCC. We will include 20 patients with MEL and RCC and compare against a historical benchmark of 20% ORR as sufficient signal of activity for further study. ORR will be assessed for association with serum IL-8 levels and radiation-induced changes in peripheral blood T cell populations. Clinical trial information: NCT04572451.