Human cartilage glycoprotein 39 (HC gp-39) appears to be a relevant autoantigen in patients with rheumatoid arthritis (RA). Administration of major histocompatibility complex (MHC) Class II complexed antigens without requisite costimulatory signals can induce immunologic tolerance. We evaluated the safety, pharmacokinetics, and preliminary efficacy of AG4263 in patients with RA. AG4263 is a soluble complex of native HLA-DR4 (beta*0401) complexed to Org 36601, a 13-mer peptide derived from HC gp-39 (also referred to as CDP263).
Thirty-one HLA-DRB1*0401 positive patients with persistent RA disease activity despite concurrent methotrexate were randomized to 7 infusions of AG4263 (n = 24) or placebo (n = 7) over 6 weeks. The initial dose of 0.5 micro g/kg was escalated in subsequent cohorts to a maximum of 150 micro g/kg. Safety analyses included recording of adverse events and measurement of CD4/CD8 counts, reactivity to recall antigens, and development of antibodies to HLA-DR4. Efficacy was assessed using the Paulus 20 criteria.
Treatment was well tolerated, with injection site reaction the most common adverse event. There was no loss of reactivity to recall antigens, change in cell counts, or antibodies to HLA-DR. The mean half-life of AG4263 was 12.5 h. Some evidence of clinical response was seen; responses were more common among patients receiving the highest doses of AG4263 and among those with baseline T cell reactivity to CDP263.
AG4263 was safe, well tolerated, and without evidence of generalized immune suppression. Along with the observed trend toward clinical efficacy, the results suggest that this therapeutic approach warrants further investigation in patients with RA.