Combination benefit of treatment with the cytokine inhibitors interleukin-1 receptor antagonist and PEGylated soluble tumor necrosis factor receptor type I in animal models of rheumatoid arthritis

Objective. To determine the potential for additive or synergistic effects o f combination therapy with the recombinant anticytokine agents interleukin- 1 receptor antagonist (IL-1Ra) and PEGylated soluble tumor necrosis factor receptor type I (PEG sTNFRI) in established type LI collagen-induced arthri tis (CIA) and developing adjuvant-induced arthritis (AIA) in rats. Methods. Rats with established CIA or developing AIA were treated with vari ous doses of IL-1Ra in a slow-release hyaluronic acid vehicle or with PEG s TNFRI, either alone or in combination with the IL-1Ra. The effects of treat ment were monitored by sequential caliper measurements of the ankle joints or hind paw volumes, final paw weights, and histologic evaluation with part icular emphasis on bone and cartilage lesions. Results. Combination therapy with IL-1Ra and PEG sTNFRI in rats with CIA re sulted in an additive effect on clinical and histologic parameters when mod erately to highly efficacious doses of each protein were administered. Grea ter-than-additive effects were seen when an inactive dose of IL-1Ra was giv en in combination with moderately to minimally active doses of PEG sTNFRI, Plasma levels associated with the latter effect (for both proteins) were si milar to those seen in rheumatoid arthritis (RA) patients in clinical trial s with these agents. Combination therapy in the ATA model generally resulte d in additive effects, but some parameters shelved a greater-than-additive benefit. Conclusion, The results provide preclinical support for the hypothesis that IL-1Ra administered in combination with PEC sTNFRI might provide substanti ally more clinical benefit to RA patients than either agent alone at blood levels that are currently achievable in patients.