To evaluate the effects of SB 273005, a potent, orally active nonpeptide antagonist of the integrin α_vβ₃ vitronectin receptor, on joint integrity in rats with adjuvant‐induced arthritis (AIA).

Male Lewis rats with AIA were orally dosed either prophylactically (days 0–20) or therapeutically (days 10–20) with SB 273005. Efficacy was determined by measurement of paw inflammation, assessment of bone mineral density using dual‐energy x‐ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and histologic evaluation.

SB 273005 is a potent antagonist of the closely related integrins, α_vβ₃ (Ki = 1.2 nM) and α_vβ₅ (Ki = 0.3 nM). When SB 273005 was administered prophylactically to AIA rats twice per day, it inhibited paw edema at doses of 10, 30, and 60 mg/kg, by 40%, 50%, and 52%, respectively. Therapeutic administration twice daily was also effective, and a reduction in paw edema was observed at 30 mg/kg and 60 mg/kg of the antagonist (by 36% and 48%, respectively). SB 273005 was also effective when administered once per day, both prophylactically and therapeutically. Significant improvement in joint integrity in treated rats was shown using DEXA and MRI analyses. These findings were confirmed histologically, and significant protection of bone, cartilage, and soft tissue was observed within the joint.

Symptoms of AIA in rats were significantly reduced by either prophylactic or therapeutic treatment with the α_vβ₃ antagonist, SB 273005. Measurements of paw inflammation and of bone, cartilage, and soft tissue structure indicated that this compound exerts a protective effect on joint integrity and thus appears to have disease‐modifying properties.