A VEGFR TK inhibitor, KRN951, suppressed the progression of pX-induced chronic and collagen-antibody–induced acute arthritis. (A) Experimental design for the treatment of mice with pX-induced chronic arthritis with a VEGFR inhibitor, KRN951. The VEGFR inhibitor was orally administered from 8 to 26 weeks of age (5 d/wk). (B) Clinical grades of arthritis gradually increased with age. The KRN951-administered group showed a reduction in the progression of arthritis compared with the untreated group. The data represent the mean ± SEM. *P < .05, **P < .01; KRN951-treated group versus control. (C) The scores of histologic findings in the treated group were also decreased (statistically not significant). (D) Experimental design for the treatment of mice with collagen-antibody–induced acute arthritis. Anticollagen-antibody was injected into the peritoneum of mice, followed by a peritoneal injection of LPS after 3 days. The administration of KRN951 started at day 3 and ended at day 7. (E-F) Clinical grade and histologic score of acute arthritis decreased in a KRN951 dose–dependent manner. The data represent the mean ± SEM. *P < .05; 40 mg/kg/d versus control. Sx indicates symptom.