Biologic agents in the treatment of rheumatoid arthritis.

Advances in the understanding of the pathogenesis of rheumatoid arthritis (RA) as well as improved biotechnology has enabled selective targeting of the pathogenic elements of disease. Targeting cell recruitment through adhesion molecules has been shown to be successful in pre-clinical murine models. Results of studies of an anti-ICAM-1 monoclonal antibody and anti-sense oligonucleotides have been encouraging. An alternate approach to inhibiting recruitment has been the targeting of chemoattractant molecules ie. chemokines. Important advances have been made in cytokine directed therapy targeting TNFalpha and IL-1. TNF antagonists (anti-TNF monoclonal antibody/soluble TNF receptor Fc fusion protein) have resulted in rapid and substantial improvement in signs and symptoms of disease as well as disease modification, shown by slowing of radiological progression. IL-1 receptor antagonist protein appears to have a significant effect on radiological progression despite a modest effect on symptoms and signs. Studies using anti-inflammatory cytokines such as IL-10 are in progress. A more recent therapeutic approach has been to target T-cell activation by interfering with co-stimulatory complexes such as CD40L/CD40 and CD28/CD80 and CD86. Both pre-clinical and preliminary clinical studies in human subjects support the concept. Another approach involving T-cell receptor peptide vaccination with VB peptides over-utilized in RA synovium has shown to be beneficial. Targeting the cytokines driving T-cells in the RA synovium ie. IL-12 & IL-15 has also proven beneficial in animal studies. Recent attention has also been directed toward the invading synovial fibroblast using Fas-FasL mediated apoptosis. Pre-clinical studies in which angiogenesis and osteoclast activation are targeted have been encouraging. In conclusion, the proof of principle has been established that selective targeting of pathogenic elements of disease results in substantial improvement in signs and symptoms as well as disease progression. Improved efficacy is expected with more aggressive targeting of the pathogenic elements.