At the time of reporting, 10 patients were enrolled into the second cohort, with 1 patient rolled over from the first cohort. Among the 44 patients enrolled, 42 were evaluable for efficacy. The overall objective response (OR) rate was 50%, with 12 patients (29%) having a complete response (CR), which means that their platelet levels rose to or above 100,000 per µL.
For the 12 patients with ITP one year or less, OR and CR rates were 58% and 25%, respectively. For the 30 patients who had the more refractory, chronic disease, of which 50% had the disease between 5 to 37 years, 47% still achieved ORs, including 30% CRs. Responses occurred across all doses tested, including the lowest dose at 80 mg x 2.
Response durability from initial dose was available from patients in the first cohort only. Of the 17 patients who responded to subcutaneous veltuzumab, the median relapsed-free survival was 8 months, with 47% of responders maintaining their response longer than 1 year. Seven responding patients had been retreated, with 2 patients (29%) achieving responses comparable to their initial responses.
This multicenter study was presented by Howard A. Liebman, MD, of the Jane Anne Nohl Division of Hematology, Keck School of Medicine, University of Southern California, Los Angeles, CA, and included also Georgia Cancer Specialists, Marietta, GA; Weill Cornell Medical Center, New York Presbyterian Hospital, New York, NJ; and Low Country Cancer Care Associates, Savannah, GA.In oncology, the Company has previously reported that 4 subcutaneous injections of low-dose veltuzumab given 2 weeks apart produced responses in 17 NHL patients that are comparable to intravenous doses. For CLL, however, high levels of circulating leukemic cells may require more frequent and prolonged dosing. Thus, a multicenter, open-label, Phase I study of single-agent veltuzumab therapy was undertaken to evaluate 2 different subcutaneous dosing schedules. Over an 8-week treatment period, three dose levels of veltuzumab at 80, 160, or 320 mg were either injected once every 2 weeks for a total of 4 doses (cohort 1), or given twice weekly for a total of 16 doses (cohort 2). A total of 11 patients with newly diagnosed or relapsed CLL had been enrolled into the first cohort, with cohort 2 currently having 10 patients enrolled.