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OP0204 Characterization of the novel C5AR antagonist CCX168, a potential therapeutic for ANCA-vasculitis, rheumatoid arthritis, and other autoimmune disorders
  1. J.P. Powers1,
  2. P.J. Bekker1,
  3. D.J. Dairaghi1,
  4. J.C. Jennette2,
  5. D.A. Johnson1,
  6. M. Leleti1,
  7. S. Miao1,
  8. L.C. Seitz1,
  9. Y. Wang1,
  10. H. Xiao2,
  11. T.J. Schall1,
  12. J.C. Jaen1
  1. 1ChemoCentryx Inc., Mountain View, CA
  2. 2UNC Chapel Hill, NC, United States

Abstract

Background The C5a receptor (C5aR) is expressed by cells of the innate immune system and is thought to play a key role in numerous autoimmune diseases, such as anti-neutrophil cytoplasmic antibody (ANCA) vasculitis and rheumatoid arthritis (RA). CCX168 is an orally active antagonist of C5aR that has completed Phase 1 evaluation and is currently in a Phase 2 trial for induction of remission in patients with ANCA-associated renal vasculitis (AARV).

Objectives To evaluate CCX168 in preclinical and clinical studies to determine safety, pharmacokinetic, and pharmacodynamics properties, and integrate these properties into a PK/PD relationship predictive of receptor coverage required for effective use in treating C5aR-mediated autoimmune diseases in humans.

Methods The in vitro potency of CCX168 against C5aR was assessed by [125I]-C5a binding and chemotaxis assays. Inhibition of C5a-induced leukopenia by CCX168 was determined in multiple species. In the Phase 1 program, ex vivo analysis of C5aR coverage on blood neutrophils was performed based on C5a-induced chemotaxis and CD11b expression. A similar PD assay was performed on blood samples from human C5aR knock-in mice dosed orally with CCX168. PK/PD requirements were defined for inhibition of C5aR-mediated neutrophil activation and prevention of anti-MPO IgG induced glomerulonephritis by CCX168 in these mice.

Results CCX168 potently blocks [125I]-C5a binding to human C5aR with an IC50 of 0.62 nM, C5a-mediated chemotaxis with an IC50 of 0.25 nM (U937 cells), and C5a-mediated Ca2+ mobilization with an IC50 of 0.2 nM in human neutrophils. In human whole blood, CCX168 blocks C5a-mediated chemotaxis of neutrophils (IC50 1.7 nM) and CD11b upregulation (IC50 4 nM), and also blocks the granulocyte chemotactic activity displayed by human synovial fluid samples (IC50 ∼5 nM). In human C5aR knock-in mice, CCX168 inhibited C5a-induced leukopenia with an ED50 of ∼0.03 mg/kg, and oral dosing to these mice markedly suppressed the induction of glomerulonephritis by anti-MPO IgG. The lowest dose that produced near-maximal therapeutic benefit in this model was 4 mg/kg bid. CCX168 was well tolerated with excellent oral bioavailability and dose-proportional exposure in a Phase 1 study in healthy volunteers, and plasma levels of CCX168 of 197 ng/mL (∼400 nM) were reached after a 100 mg dose, far exceeding the levels required in the anti-MPO mouse model for near-maximal prevention of glomerulonephritis. Twelve hours following a 100 mg single dose of CCX168, there was a 94% reduction in C5a-induced CD11b upregulation on blood neutrophils (ex vivo PD assay). The combined clinical and preclinical PK/PD results indicate a 30 mg bid dosing regimen in humans should result in >90% receptor coverage on human blood leukocytes at all times.

Conclusions CCX168 is a highly potent, orally active, antagonist of C5aR which was well tolerated in Phase 1. The PK/PD data from preclinical and human Phase 1 studies indicate that 30 mg CCX168 bid in humans should result in >90% coverage of C5aR in blood at all times, considered optimal for C5aR antagonism in patients with autoimmune diseases such as vasculitis and RA. A Phase 2 trial of CCX168 in patients with AARV is currently underway.

Disclosure of Interest J. Powers Employee of: ChemoCentryx, P. Bekker Employee of: ChemoCentryx, D. Dairaghi Employee of: ChemoCentryx, J. Jennette: None Declared, D. Johnson Employee of: ChemoCentryx, M. Leleti Employee of: ChemoCentryx, S. Miao Employee of: ChemoCentryx, L. Seitz Employee of: ChemoCentryx, Y. Wang Employee of: ChemoCentryx, H. Xiao: None Declared, T. Schall Employee of: ChemoCentryx, J. Jaen Employee of: ChemoCentryx

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