Immunomedics Inc., a biopharmaceutical company, has reported initial clinical experience with a combination of epratuzumab, the company’s humanized anti-CD22 antibody, labeled with the radioisotope, yttrium-90 (90Y), and veltuzumab, the company’s humanized anti-CD20 antibody, in patients with relapsed aggressive non- Hodgkin lymphoma (NHL).

Unlike indolent NHL, aggressive NHLs have proven to be more resistant to currently approved antibody therapies unless they are combined with chemotherapy, such as rituximab + CHOP (R- CHOP) for diffuse large B-cell lymphoma (DLCBL) and rituximab + hyper-fractionated CVAD for mantle cell lymphoma (MCL). A significant percentage of these patients who relapsed or become refractory are ineligible for high-dose salvage therapy or stem cell transplant due to advanced age, chemo-resistant disease, and/or concurrent co-morbid medical conditions. Indeed, elderly DLBCL patients who failed R-CHOP have a poor prognosis after disease progression.

Thus, there is a considerable need for developing better treatment alternatives for these patients. A novel approach for NHL therapy that the Company is pursuing involves radioimmunotherapy (RAIT) with 90Y-epratuzumab combined with immunotherapy using unlabeled veltuzumab. This is a new therapy concept due to the fact that CD22 and CD20 are distinct antigens. Consequently, anti-CD20 antibodies would not cross-block anti-CD22 RAIT, which, at least in the case of DLBCL, could allow for more effective consolidation with anti-CD22 RAIT after R-CHOP therapy.

13 patients with various types of aggressive NHL who had failed 1 or more prior standard therapies have been enrolled into this Phase I/II study to receive four weekly treatment of veltuzumab at 200 mg/m2, with indium-111-epratuzumab for imaging and pharmacokinetics on week 2 and 90Y-epratuzumab at planned dose levels on weeks 3 and 4. At the time of reporting, results from 10 patients were available. Five patients received 6 or 9 mCi/m2 of 90Y-epratuzumab while the other 5 patients were dosed at 12 or 15 mCi/m2.

Half of the patients showed an overall objective response rate, with 1 DLBCL patient having a complete response which is ongoing at 9 months. Three patients with transformed follicular NHL and 1 DLBCL patient were partial responders. Three of these partial responders relapsed after 3 to 6 months with 1 ongoing for 4 weeks. For MCL, all three patients had disease stabilization as their best response, with 2 patients relapsing after 3 to 6 months and 1 ongoing at 4 weeks.

Commenting on these preliminary results, Cynthia L Sullivan, president and CEO remarked, “We are pleased with this initial evidence of therapeutic activity in these difficult to treat patients. The trial is continuing to determine an acceptable 90Y dose for this population and define the safety and efficacy profile of this combination approach.”

The combination treatment was well tolerated, with the pharmacokinetic behavior of the two agents substantially unchanged when given together. Hematologic toxicity necessitated lowering the 90Y dose, most likely due to the prior aggressive chemotherapies or depletion of the normal B-cell pool by veltuzumab that preceded 90Y-epratzumab. This study was supported in part by Award Number R44CA139668 from the National Cancer Institute. The content is solely the responsibility of the Company and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health.

Immunomedics is a New Jersey-based biopharmaceutical company primarily focused on the development of monoclonal antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases.