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Abstract

OBJECTIVE: CXCL10 (also known as interferon gamma inducible protein-10, IP-10) is a chemokine that potentially plays a role in the immunopathogenesis of RA. This phase II study evaluated the efficacy and safety of MDX-1100, a fully human, neutralizing anti-CXCL10 (anti-IP-10) monoclonal antibody, in patients with RA who had an inadequate response to methotrexate (MTX).

METHODS: Patients with active RA on stable doses of MTX (10 to 25 mg weekly) were randomized to receive intravenous doses of MDX-1100 at 10 mg/kg (n=35) or placebo (n=35) every other week. The primary endpoint was the ACR20 response rate at Day 85 and patients were followed for safety to Day 141.

RESULTS: The ACR20 response rate was significantly higher for MDX-1100 treated patients compared to placebo (54% versus 17%; p-value = 0.0024). Statistically significant difference in ACR20 response rate was observed between MDX-1100 and placebo treatment starting at Day 43 (p<0.05). The ACR50 and ACR70 response rates in the MDX-1100 treatment group at Day 85 were not significantly different from placebo. Overall, 51.4% of MDX-1100 treated patients and 30.3% of placebo treated patients experienced at least 1 adverse event. No drug related serious adverse events were reported.

CONCLUSIONS: MDX-1100 was well tolerated and demonstrated clinical activity in RA patients who had an inadequate response to MTX. This is the first study to demonstrate clinical activity of a chemokine inhibitor in RA and supports the potential role of IP-10 in the immunopathogenesis of RA.