Antibody-mediated stripping of CD4 from lymphocyte cell surface in patients with rheumatoid arthritis.

OBJECTIVE: Keliximab studies have provided evidence of the therapeutic potential of a non-depleting CD4 monoclonal antibody (mAb) in the treatment of rheumatoid arthritis (RA). Clenoliximab, an immunoglobulin G4 derivative of keliximab, has substantially reduced potential to deplete CD4 cells. In initial studies of clenoliximab, we investigated the hypothesis that the decrease in cell surface CD4 is the result of antibody-mediated stripping from the cell surface. METHODS: Patients received single or multiple intravenous infusions of clenoliximab as follows: 0.05, 0.2, 1, 5, 10 or 15 mg/kg (n=3-5/group); 150 or 350 mg weekly x 4; or 350 or 700 mg every other week x 2 (n=12/group). Blood was collected for up to 16 weeks and pharmacokinetic and pharmacodynamic assessments were conducted using immunoassay and flow cytometry. RESULTS: CD4 count was largely unaffected by clenoliximab treatment. Dose-dependent CD4 coating, down-modulation and stripping were observed. Maximal down-modulation persisted for an increasing period as dose increased, while soluble CD4-clenoliximab complexes accumulated. The amount of CD4 in soluble complex was as much as 20 times the amount of cell-associated CD4. For the same total dose, administration of higher doses, less frequently, resulted in pharmacodynamic profiles similar to those of lower doses administered more frequently. CONCLUSION: Decrease in the density of CD4 on the T-lymphocyte surface is caused by antibody-mediated stripping.

Phase I clinical trial of a monoclonal antibody against CD40-ligand (IDEC-131) in patients with systemic lupus erythematosus.

OBJECTIVE: To investigate the safety and pharmacology of a humanized monoclonal antibody against CD40-ligand (IDEC-131) in patients with systemic lupus erythematosus (SLE). METHODS: Cohorts of 3 to 5 patients with symptomatic lupus each received 0.05, 0.25, 1.0, 5.0, or 15.0 mg/kg of IDEC-131 as a single intravenous infusion. Patients were followed for 3 months to evaluate toxicity and pharmacokinetics. RESULTS: This phase I, single dose, dose-escalating study was conducted in 23 patients at a single institution. All patients experienced at least 1 adverse event (AE) during a 3 month followup period, although 58 AE in 17 patients were considered possibly or probably related or of unknown relationship to treatment. No dose relationship in the distribution of AE was apparent. No infusion related cytokine-release syndrome was observed; no infusions were interrupted, and all patients completed treatment. Eight mild (grade 1 or 2) infections were reported in 8 patients. All infections were considered unrelated to drug administration and all resolved uneventfully. No patient developed detectable antibodies to IDEC-131. Flow cytometry revealed no apparent treatment related depletion of lymphocyte subsets. Pharmacokinetic analysis indicated that the maximum serum concentration and the area under the concentration curve of IDEC-131 were proportional to the dose administered. At doses between 1.0 and 15.0 mg/kg, the serum half-life ranged from 299 to 320 h. Efficacy was not formally evaluated in this single dose study. CONCLUSION: IDEC-131 (humanized Mab against CD40L) administered in a single intravenous infusion at doses of 0.05-15.0 mg/kg is safe and well tolerated in patients with SLE.

A population pharmacokinetic-pharmacodynamic analysis of single doses of clenoliximab in patients with rheumatoid arthritis.

Clenoliximab (IDEC-151) is a macaque-human chimeric monoclonal antibody (immunoglobulin G4) specific for the CD4 molecule on the surface of T lymphocytes. It is being studied in patients with rheumatoid arthritis in which T cell activation orchestrates inflammation and tissue damage. In this initial study in humans, the pharmacokinetics and pharmacodynamics of clenoliximab were investigated after single intravenous infusion. Blood was collected up to 12 weeks after dose administration to measure clenoliximab concentration, CD4+ T-cell count, CD4 antigen coating, and CD4 cell surface density. Clenoliximab displayed nonlinear pharmacokinetic behavior and caused an 80% reduction in CD4 density for up to 3 weeks, without depleting T cells. A pharmacokinetic-pharmacodynamic model was developed that described the relationship between antibody concentration, antigen coating, and the observed decreases in CD4 cell surface density. This was used to anticipate the effects of clenoliximab in untested regimens and optimize the design of future clinical trials.

IgG but not other classes of anti-[(H2A-H2B)-DNA] is an early sign of procainamide-induced lupus.

A longitudinal study was undertaken to characterize the autoantibodies induced during the course of procainamide treatment and to relate this information to the appearance of symptomatic drug-induced lupus. IgG, IgA, and IgM Abs to histones, native and denatured DNA, chromatin, and (H2A-H2B)-DNA were determined by ELISA in serial serum samples obtained over the course of an average of 2.1 yr on 22 patients undergoing treatment with procainamide and on an additional 9 patients after discontinuation of procainamide because of drug-induced lupus. Ten patients in the prospective group developed lupus-like symptoms after an average of 1.8 +/- 2.1 yr of procainamide treatment. Of the total of 19 patients with drug-induced lupus, 16 had IgG Abs to the (H2A-H2B)-DNA complex at the time of diagnosis; this autoantibody was first detected 0.9 +/- 1.3 yr before diagnosis in 7 patients. In contrast, the 9 patients who remained asymptomatic during treatment with procainamide for an average of 4.3 +/- 2.2 yr had negligible levels of IgG anti-[(H2A-H2B)-DNA], although IgA and IgM Abs of this specificity were not uncommon. Abs to denatured DNA and histones were elicited coordinately, but these specificities did not discriminate symptomatic from asymptomatic procainamide-treated patients. We conclude that chronic exposure to procainamide commonly elicited autoantibodies with specificities for denatured epitopes on DNA and histones and for native regions on the (H2A-H2B)-DNA subunit of chromatin. However, rapid switch to the IgG class of anti-[(H2A-H2B)-DNA] occurred only in patients who went on to develop symptomatic disease.

Association of antibody to histone complex H2A-H2B with symptomatic procainamide-induced lupus.

Antinuclear antibodies develop in most patients who are given prolonged procainamide therapy, but clinical symptoms resembling those of lupus appear in only 15 to 20 percent of such persons. No objective marker for symptomatic procainamide-induced lupus has been described. However, IgG antibodies to the histone complex H2A-H2B have previously been reported in this disorder, and it has been suggested that antiguanosine antibodies may be a marker for major manifestations of procainamide-induced lupus. We therefore tested for these antibodies in 20 symptomatic and 31 asymptomatic patients treated with procainamide. Most of the symptomatic patients had multiple manifestations of drug-induced lupus; resolution of symptoms after the discontinuation of procainamide was required for inclusion in the symptomatic group. All 20 symptomatic patients had elevated IgG antibodies to H2A-H2B, in contrast to only 2 asymptomatic patients (P less than 0.001). This activity was absent in patients not treated with procainamide and in patients with lupus induced by hydralazine or quinidine. IgG antiguanosine was elevated as compared with normal controls in 13 of 20 symptomatic and 19 of 31 asymptomatic patients--a finding that did not distinguish between symptomatic and asymptomatic patients. We conclude that IgG antibodies to H2A-H2B are a sensitive and specific marker for procainamide-induced lupus. The striking correlation between antibodies to H2A-H2B and symptomatic disease suggests a possible association between this antibody and the underlying pathogenic events.

Drug-induced lupus. Genetic, clinical, and laboratory features.

Drug-induced lupus is a disorder similar to idiopathic systemic lupus erythematosus in terms of manifestations. However, these entities have significant serologic and clinical differences, which call into question the concept that they represent an identical disease process. Nonetheless, further research into the drug-induced disease will enhance our understanding and management of this clinically significant iatrogenic disease and will likely contribute to our comprehension of the pathogenesis of autoimmunity.