To elucidate the role of methionine aminopeptidase type-2 (MetAP-2) in the clinical pathology of rheumatoid arthritis, arthritis was induced in rats by administration of peptidoglycan-polysaccharide (PG-PS).
The inhibitor of MetAP-2, PPI-2458, was administered orally at 5 mg/kg every other day during 3 distinct phases of the disease. In vitro studies were performed to clarify in vivo findings.
Ankle swelling was completely alleviated by MetAP-2 inhibition. Inhibition of MetAP-2 in blood and tissues correlated with protection against PG-PS-induced arthritis. Histopathology of the tarsal joints improved following PPI-2458 administration, including a significant improvement of bone structure. In in vitro studies, osteoclast formation and activity were inhibited by PPI-2458, a mechanism not previously attributed to MetAP-2 inhibition.
The important role that MetAP-2 has in the pathophysiological disease processes of PG-PS arthritis provides a strong rationale for evaluating PPI-2458 as a disease modifying antirheumatic treatment for rheumatoid arthritis.