Epratuzumab-rituximab combination therapy effective against previously untreated follicular lymphoma

Immunomedics, Inc. (Nasdaq:IMMU), a biopharmaceutical company primarily focused on the development of monoclonal antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases, today announced that combination therapy with epratuzumab and rituximab was effective, with durable complete responses in one-third of evaluable patients, and was very well tolerated by patients with previously untreated follicular lymphoma (FL).

Epratuzumab is Immunomedics' proprietary humanized anti-CD22 monoclonal antibody that has shown single agent activity in FL, and when used in combination with rituximab, produced durable, complete responses in patients with relapsed or refractory indolent non-Hodgkin's lymphoma (NHL). Rituximab is also effective as single agent therapy for FL, and has extended remissions and survival when combined with chemotherapy.  The goal of this multicenter, open-label, Phase II trial was to evaluate the combination of epratuzumab and rituximab without chemotherapy in treatment-naive FL patients.

Sixty evaluable FL patients were enrolled by the NCI-sponsored study group, CALGB, to receive intravenous epratuzumab and rituximab at 360 mg/m² and 375 mg/m², respectively. Rituximab was administered weekly for 4 weeks, then every 8 weeks for 4 additional doses for a total of 8 doses over 9 months. Epratuzumab was given two days before the first rituximab dose to assess toxicity.  From week 2 on, epratuzumab was given before rituximab on the same day for a total of 8 doses over 9 months.

Patients were categorized into three groups with good, intermediate or poor prognosis, based on their Follicular Lymphoma International Prognostic Index (FLIPI) scores.  A high FLIPI score predicts a patient having a poorer chance of having a treatment response.  FLIPI scores at study entry were 13 (22%) low; 28 (47.5%) intermediate; and 18 (30.5%) high. 

Results from 57 evaluable patients were reported at the meeting. Overall, the two antibodies produced an objective response rate of 84.2% with 20 complete responses (CRs) (33.3%), 30 partial responses (PRs) (50.9%) and 8 patients (13.6%) having stable disease. The mean time to CR was 9 months. Four patients progressed after a period of stable disease, and 23 of the 30 patients who achieved PR remain in response. All 20 CRs also remain in remission at the time of reporting, with a median follow-up of 1.4 years. The CR rate in low risk patients was 31%, 44% in intermediate risk and 18% in high risk patients.

"This is the 4th multicenter trial indicating high efficacy of epratuzumab when combined with rituximab," commented Cynthia L. Sullivan, President and Chief Executive Officer of Immunomedics, Inc.