To determine the optimal dose regimen for intravenous Ro 45-2081 (lenercept) in patients with rheumatoid arthritis (RA) by evaluating efficacy, safety, tolerability, and pharmacokinetic and pharmacodynamic characteristics.
Adult patients with longstanding RA who were taking stable doses of nonsteroidal antiinflammatory drug and/or low dose corticosteroids but who had stopped their previous disease-modifying antirheumatic drug were randomly assigned to receive 3 intravenous infusions, one every 4 weeks, of placebo or Ro 45-2081 in a double blind, placebo controlled, parallel group multicenter trial. Patients received one of the following: (1) placebo, (2) low dose Ro 45-2081 (0.05 mg/kg, maximum 5 mg), (3) middle dose (mid-dose) Ro 45-2081 (0.2 mg/kg, maximum 20 mg), or (4) high dose Ro 45-2081 (0.5 mg/kg, maximum 50 mg). Efficacy measures included change from baseline in number of swollen joints and tender joints, scores on physician and patient assessments of disease activity, and patient assessment of pain, as well as acute phase reactants.
Patients treated with Ro 45-2081 exhibited improvement after one day of the first intravenous infusion. This treatment benefit maximized by 2 weeks but diminished thereafter. After the second and third infusion, improvement was of shorter duration as non-neutralizing anti-Ro 45-2081 antibodies developed and accelerated clearance of Ro 45-2081. There were no antibodies after the first infusion. This made efficacy transient in the mid-dose group and modest in the low and high dose groups at 12 weeks of treatment, resulting in no statistical differences at most time points or doses of Ro 45-2081. The majority of adverse experiences were mild or moderate, and were not related or only remotely related to study drug. No clinically relevant changes in mean laboratory values were reported. The third dose pharmacokinetic measurements showed that the average Ro 45-2081 clearance rate more than doubled compared with the first dosing interval, thus reducing the average Ro 45-2081 AUC by 36%.
Intravenous Ro 45-2081 every 4 weeks proved to be well tolerated and transiently effective in the mid-dose group and modestly effective in the low and high dose groups in patients with longstanding RA. The interactions between Ro 45-2081, its non-neutralizing anti-Ro 45-2081 antibody, and the clinical benefit remain complex, but affected efficacy over the 12 weeks of treatment as Ro 45-2081 concentrations fell.