REGN7999 is a monoclonal antibody that inhibits TMPRSS6. By suppressing TMPRSS6 activity, REGN7999 prevents HJV cleavage, enhancing BMP6-HJV signaling and increasing serum hepcidin levels. This inhibition aids in alleviating iron overload and impaired erythropoiesis in β-thalassemia mouse models. REGN7999 is applicable for research in β-thalassemia.

REGN7999 effectively inhibits the activity of human and mouse TMPRSS6 in HEK293 cells that overexpress HJV and TMPRSS6, with IC50 values of 0.68 nM and 16 nM, respectively, and prevents HJV cleavage. It binds to TMPRSS6, reducing the proteolytic activity of both the reference and variant human TMPRSS6, cynomolgus monkey TMPRSS6, and mouse TMPRSS6 across species.

REGN7999 administered at 10 mg/kg subcutaneously once weekly for 12 weeks in the Hbb th3/+ mouse model can increase serum hepcidin levels, reduce liver iron content, restore red blood cell (RBC) levels, and enhance the health of RBCs. A single dose of REGN7999 (5 mg/kg subcutaneous injection) can elevate serum hepcidin and decrease serum iron in the C57BL/6 mouse model.