Effect of the Anti-C1s Humanized Antibody TNT009 and Its Parental Mouse Variant TNT003 on HLA Antibody-Induced Complement Activation-A Preclinical In Vitro Study

Am J Transplant. 2017 Sep;17(9):2300-2311. doi: 10.1111/ajt.14256. Epub 2017 Mar 31.


The classic pathway (CP) of complement is believed to significantly contribute to alloantibody-mediated transplant injury, and targeted complement inhibition is currently considered to be a promising approach for preventing rejection. Here, we investigated the mode of action and efficacy of the humanized anti-C1s monoclonal antibody TNT009 and its parental mouse variant, TNT003, in preclinical in vitro models of HLA antibody-triggered CP activation. In flow cytometric assays, we measured the attachment of C1 subcomponents and C4/C3 split products (C4b/d, C3b/d) to HLA antigen-coated flow beads or HLA-mismatched aortic endothelial cells and splenic lymphocytes. Anti-C1s antibodies profoundly inhibited C3 activation at concentrations >20 μg/mL, in both solid phase and cellular assays. While C4 activation was also prevented, this was not the case for C1 subcomponent attachment. Analysis of serum samples obtained from 68 sensitized transplant candidates revealed that the potency of inhibition was related to the extent of baseline CP activation. This study demonstrates that anti-C1s antibodies TNT009 and TNT003 are highly effective in blocking HLA antibody-triggered complement activation downstream of C1. Our results provide the foundation for clinical studies designed to investigate the potential of TNT009 in the treatment or prevention of complement-mediated tissue injury in sensitized transplant recipients.

Keywords: basic (laboratory) research/science; complement biology; flow cytometry; fusion proteins and monoclonal antibodies; histocompatibility; immunosuppressant; immunosuppression/immune modulation; major histocompatibility complex (MHC); rejection: antibody-mediated (ABMR); translational research/science.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology*
  • Complement Activation / immunology*
  • Complement C1s / immunology*
  • Follow-Up Studies
  • Glomerular Filtration Rate
  • Graft Rejection / drug therapy*
  • Graft Rejection / etiology
  • Graft Survival
  • HLA Antigens / immunology*
  • Humans
  • Isoantibodies / adverse effects*
  • Kidney Failure, Chronic / immunology
  • Kidney Failure, Chronic / surgery
  • Kidney Function Tests
  • Kidney Transplantation / adverse effects*
  • Mice
  • Prognosis


  • Antibodies, Monoclonal
  • HLA Antigens
  • Isoantibodies
  • TNT003
  • Complement C1s