Plonmarlimab (TJM2/TJ003234) is a humanized IgG1 monoclonal antibody that is designed to neutralise granulocyte-macrophage colony-stimulating factor (GM-CSF; CSF2
) cytokine activity. It was developed by I-Mab Biopharma for potential to treat autoimmune diseases, and is likely to be Hu23F4-27 as claimed in I-Mab patent WO2018050111A1 [2
: Plonmarlimab is being evaluated as a mechanism to down-regulate elevated inflammation/cytokine release syndrome in patients with COVID-19 [1
] in a Phase 2/3 study.