S961

S961 is a **biosynthetic peptide consisting of 43 amino acids** that acts as a **high-affinity, selective antagonist of the insulin receptor (IR)**. It binds to both major isoforms of the human insulin receptor (HIR-A and HIR-B) with inhibition constants (IC50) of approximately 0.048 nM and 0.027 nM, respectively, and exhibits much lower affinity for the human insulin-like growth factor I receptor (HIGF-IR), with an IC50 of 630 nM[2][4][7]. S961 completely blocks the action of insulin in various in vitro cell assays and in vivo models, and is used in research settings to elucidate insulin receptor signaling and function. Its use has demonstrated downregulation of insulin receptor expression and suppression of cell proliferation in breast cancer cell lines, suggesting a potential as a research tool for metabolic and oncologic disease modeling[10][1][2][4]. S961 is **not approved for human therapeutic use** and is intended only for research applications.

Other names

S961S-961S 961NNC0069-0961NNC-0069-0961NNC 0069-0961