Immunomedics Offers Updated Clinical Results on Potential New Treatment Regiment for NHL

Immunomedics, Inc.

, 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 reported that small, repeated doses of epratuzumab labeled with the radioisotope, yttrium-90 (^90Y), demonstrated therapeutic activity in 2 clinical trials in patients with aggressive non-Hodgkin lymphoma (NHL). Epratuzumab is a humanized antibody that binds to the CD22 receptor on B cells. In various clinical trials, epratuzumab was found to be active as an unlabeled antibody in patients with NHL or lupus. Previous clinical studies have also demonstrated that repeated administration of small doses of ^90Y-epratuzumab are tolerable in NHL patients and produced high rates of durable responses. Despite recent advances in the use of antibody for the management of NHL, aggressive NHLs have proven to be more resistant to currently approved antibody therapies unless they are combined with chemotherapy. Diffuse large B-cell lymphoma (DLCBL) is the most common type of aggressive NHL, with approximately 20,000 new patients diagnosed each year in the United States. The standard-of-care for DLBCL is combining the anti-CD20 antibody, rituximab, with the CHOP chemotherapy regimen, or R-CHOP. However, elderly patients who fail R-CHOP have a poor outcome. Due to advanced age, chemo-resistant disease, and/or concurrent co-morbid medical conditions, a significant percentage of these patients are not eligible for high-dose salvage therapy or stem cell transplant. Consequently, there is a need for alternative therapy for high-risk patients with a lower chance of being cured with standard R-CHOP. An innovative approach for NHL therapy that the Company and its outside collaborators are developing is to combine antibody-directed radiation therapy using ^90Y-epratuzumab with antibody therapy targeting a different antigen. Since the two antibodies bind to two distinct antigens and do not cross-block each other, this concept may offer more synergy than current NHL radioimmunotherapy that employs unlabeled antibody targeting the same B-cell antigen. Updated results from a multicenter Phase II trial sponsored by the French LYSA study group were reported in an oral presentation at this year's ASH Annual Meeting by Pierre Soubeyran, MD, PhD, of the Bergonié Cancer Institut, Bordeaux, France. The goal of this open-label study is to evaluate ^90Y-epratuzumab given in small doses as consolidation therapy after R-CHOP in previously untreated elderly patients with advanced DLBCL. Primary end-point of the study is 2-year event-free survival (EFS). At the time of reporting, a total of 75 patients between the ages of 60 and 80 years had been enrolled to receive 6 cycles of R-CHOP therapy, with 61 patients eligible for 2 consolidation treatments of ^90Y-epratuzumab at 15 mCi/m^2. Using the 1999 International Workshop for Response Criteria for NHL, the overall response rate (ORR) after 6 cycles of R-CHOP therapy was 94.6% (71/75), with 52 patients (69.3%) achieving a complete or unconfirmed complete response (CR/CRu) and 19 patients (25.3%) reporting a partial response (PR). At a median follow-up of 24 months (range from 1 - 46), 18 patients experienced lymphoma progression and/or related death, yielding an estimated 2-year EFS of 73.3% (60.7 - 82.5%) and an estimated 2-year overall survival (OS) of 83.2% (71.4 - 90.4%). For the 61 patients who received the 2 consolidation ^90Y-epratuzumab treatments, ORR was 91.8% (56/61), with 50 patients (81.9%) achieving a CR/CRu. Eight of 16 patients (50.0%) who had less than a CR/CRu with R-CHOP converted to CR/CRu after receiving radiolabeled epratuzumab. Among these 61 patients, 12 experienced progression and/or related death, yielding an estimated 2-year EFS of 78.7% (65.1 - 87.4%) and an estimated 2-year OS of 90.1% (77.7 - 95.8%). Separately, the Company is investigating a combination of ^90Y-epratuzumab and its second-generation, humanized anti-CD20 antibody, veltuzumab, in patients with relapsed aggressive NHL. Michael B Tomblyn, MD, of H. Lee Moffitt Cancer Center, Tampa, FL, presented updated results at the same ASH medical conference, with clinical research sites from Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN; Helen F Graham Cancer Center, Newark, DE; Weill Cornell Medical College, New York, NY; and Indiana University Health Center for Cancer Care, Goshen, IN, participating in this Phase I, open-label study. Results from 18 patients with various types of aggressive NHL who had failed 1 or more prior standard therapies were reported at the conference. The ^90Y dose was repeatedly de-escalated from 15 (N=3) to 12 (N=3), 9 (N=6), and currently 6 (N=6) mCi/m^2 due to hematologic dose-limiting toxicities. Otherwise, treatment was well-tolerated with no infusion reactions. The overall objective response rate among 17 patients who have had treatment response assessments was 53%, including one DLBCL patient (6%) with a CR continuing 12 months later. The combination is active in all NHL subgroups and across ^90Y dose levels. At the maximum tolerated dose of 6 mCi/m^2 x 2, 5 of 6 patients (83%) achieved PRs.