Pharmacokinetic, pharmacodynamic and clinical effects of a humanized IgG1 anti-CD4 monoclonal antibody in the peripheral blood and synovial fluid of rheumatoid arthritis patients

Background. CD4(+) T cells are important mediators in the pathogenesis of r heumatoid arthritis (RA). Tn this open-label, dose-escalating study, we exa mined the pharmacokinetic (PK), clinical, biological and immunological effe cts of a humanized IgG1 anti-CD4 monoclonal antibody (mAb), 4162W94, in the peripheral blood (PB) and synovial fluid (SF) of RA patients. Method. Twenty-four patients in four cohorts (six patients in each cohort) were allocated to be treated with five consecutive daily doses of 4162W94 ( 10, 30, 100 or 300 mg i.v.). Disease activity was measured by the American College of Rheumatology (ACR) criteria and disease activity score (DAS). We also measured 4162W94 concentration, the percentage of 4162W94-coated CD4( +) lymphocytes, percentage down-modulation of CD4, interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF alpha) levels in the PB and SF. Results. A direct relationship between 4162W94 dose, biological response an d clinical outcome was seen. Treatment with 10 and 30 mg of 4162W94 for 5 c onsecutive days resulted in transient coating and down-modulation of CD4(+) lymphocytes, with little effect observed beyond the final dose. However, t reatment with 100 and 300 mg resulted in sustained coating and/or down-modu lation for 3 weeks and 4 weeks, respectively, in PB and >4 weeks in SF in o ne patient from the 300 mg cohort. There was a dose-related moderate but tr ansient depression in the CD4(+) lymphocyte count in most patients, with al l but three returning to >0.40 x 10(9)/1 or > 75% baseline by the end of th e study period. Significant clinical improvement (ACR 20%) was seen in only 1/6 patients in each of the 10- and 30-mg cohorts; however, 3/6 and 5/5 pa tients in the 100 and 300-mg cohorts, respectively, were ACR 20% responders . In addition, there were significant reductions in PB acute phase reactant s as well as SF IL-6 and TNF alpha concentrations in parallel to clinical i mprovement. Conclusion. Data from this pilot study suggest that 4162W94 is a clinically active novel immunotherapeutic agent that may suppress inflammation in RA.