Background: COM701 is a novel 1st-in-class monoclonal antibody that binds with high affinity to poliovirus receptor related immunoglobulin domain containing (PVRIG) blocking its interaction with its ligand, PVRL2. In preclinical experiments inhibition of PVRIG alone and in combination with a PD-1 inhibitor leads to activation of T cells in the tumor microenvironment generating an anti-tumor immune response leading to tumor growth inhibition. Novel checkpoint therapies are needed for the treatment of patients with advanced malignancies. We hypothesized that COM701 monotherapy and in combination with nivolumab will be safe and tolerable and demonstrate preliminary antitumor activity in pts with advanced solid malignancies. Methods: This ongoing phase 1 study (NCT03667716) is evaluating the safety and tolerability of escalating doses of COM701 monotherapy IV Q3 or Q4 weekly and in combination with nivolumab 360 mg IV Q3 weekly or 480 mg IV Q4 weekly. Key Inclusion Criteria: Age ≥18 yrs, histologically or cytologically confirmed advanced solid malignancy and has exhausted all available standard therapy, ECOG performance status 0-1, prior ICI permissible. Key Exclusion Criteria: Symptomatic interstitial lung disease or inflammatory pneumonitis, untreated or symptomatic central nervous system metastases. Primary outcome measures are the incidence of adverse events and dose-limiting toxicities (21-day or 28-day DLT window), pharmacokinetics of COM701 and to identify the maximum tolerated dose and/or the recommended dose for expansion. Key secondary outcome measures are to characterize the immunogenicity and preliminary antitumor activity of COM701 as monotherapy and in combination with nivolumab. Study Design: Hybrid accelerated titration and 3+3 study design. Statistical Considerations: Adverse events graded as per CTCAE v4.03, responses as per RECIST v1.1. Analyses of all study objectives are descriptive and hypothesis generating. As of the date of this submission dose level 8 of COM701 monotherapy and dose level 3 of the combination arm are open to enrollment. Updated data will be presented at the conference. Clinical trial information: NCT03667716