Background: Visilizumab is a humanized IgG(2) monoclonal anti-CD3 antibody. We evaluated its safety and dose response in severe intravenous steroid-refractory ulcerative colitis (UC). Methods: In... Show moreBackground: Visilizumab is a humanized IgG(2) monoclonal anti-CD3 antibody. We evaluated its safety and dose response in severe intravenous steroid-refractory ulcerative colitis (UC). Methods: In all, 104 patients were treated. In Stage 1, 73 patients were randomly assigned to receive intravenous visilizumab 5, 7.5, 10, or 12.5 mu g/kg/day for 2 consecutive days. In Stage II, 33 patients received visilizumab at the optimal clinical dose (OCD) of 5 mu g/kg/day for 2 days. Symptomatic response and remission were defined by the modified Truelove-Witts severity index. Clinical response and remission were defined by the Mayo score. Results: The rates of symptomatic response at day 15 in the 5, 7.5, 10, or 12.5 mu g/kg dose groups were 71%, 70%, 50%, and 61%. respectively, in Stage I and in 54% in Stage II. The symptomatic remission rates were 3.5%, 5%, 22%, and 11% in Stage I and 18% in Stage II. The rates of clinical response at day 30 in the 5, 7.5, 10, or 12.5 mu g/kg dose groups were 71%, 65%, 50%, and 67%, respectively, in Stage I and 55% in Stage II. The clinical remission rates were 6%, 5%, 0%, and 11% in Stage I and 6% in Stage II. All patients experienced adverse events. Serious adverse events included abdominal abscess, cytomegalovirus infection, atrial fibrillation, herpes zoster, and esophageal candidiasis. Conclusions: Treatment with visilizumab induced symptomatic response and clinical response. Results with 5 mu g/kg/day were similar to those observed with higher doses (NCT00267306 at www.clinicaltrials.gov). Show less
