The treatment of inflammatory diseases can be achieved by inhibiting relevant cytokine pathways including the interleukin-1 (IL-1) family. RPH-104 (Goflikicept) is a newly developed heterodimeric fusion protein to block IL-1. Preclinical studies were conducted to evaluate the efficacy and safety of RPH-104 using both in vitro and in vivo studies including investigations in relevant species. A surface plasmon resonance-based approach was used to determine the affinity of RPH-104 to IL-1α, IL-1β, IL-1 receptor antagonist (IL-1Ra). In vitro efficacy was demonstrated in a cell-based model system. Its ability to interact with Fcɣ receptors, and therefore estimate influence on PK/PD, was also assessed. RPH-104 was well tolerated in single-dose and 4-week repeat-dose toxicity studies in Macaca fascilularis (cynomolgus monkeys). Single dose toxicity study included the assessment of the toxicity and pharmacokinetics of RPH-104 following a single subcutaneous and intravenous (bolus) administration. Repeated-dose toxicity and toxicokinetics studies were performed following subcutaneous administrations for 28 days. There were no clinical signs of local or systemic toxicity during in vivo studies. The results of nonclinical studies facilitated the successful advancement of RPH-104 into the clinical trials (recurrent pericarditis, familial Mediterranean fever).