Immunomedics Reports Multiple Partial Responses with IMMU-132 in Solid Cancers, Phase I/II Indicate Overall 77% Disease Control Rate

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 announced that 5 patients reported a partial response as their best response, based on RECIST 1.1 criteria, in the Company's ongoing Phase I/II clinical trial of its investigational antibody-drug conjugate (ADC), IMMU-132, in patients with solid cancers. IMMU-132 is an anti-TROP-2 antibody with SN-38, the active metabolite of irinotecan, linked to the antibody. Results from this multicenter study, as well as initial data from the expansion phase of the trial, were presented by Dr. Alexander Starodub of Indiana University Health Goshen Center for Cancer Care, Goshen, IN, at the 2014 Annual Meeting of the American Association for Cancer Research (AACR) in San Diego, CA. Two of the 3 patients with small-cell lung cancer (SCLC), 2 of the seven patients with triple- negative breast cancer, and 1 of the 11 patients with colorectal cancer were partial responders by at least one computer tomography (CT) assessment. In addition to these 5 partial responses, among the 35 patients who had at least one response assessment by CT, 22 patients had stable disease as their best response, giving an overall disease control rate of 77%. Besides colorectal, triple-negative breast, and SCLC, the 35 CT-assessable patients include 14 other types of solid cancer. These patients had failed a median of 4 prior treatments, some including topoisomerase-I and -II inhibiting drugs, and in some cases are showing durable responses up to almost one year. Grade 3 or 4 adverse events (AE) ≥ 8 % were neutropenia (31%), fatigue (10%), and diarrhea (8%), while mild AE ( > 20%) were reported for nausea, fatigue, alopecia, diarrhea and vomiting. IMMU-132 was administered once weekly for two weeks followed by one week of rest in a 3-week cycle. Despite repeated dosing, no antibodies against the ADC, either to the antibody or to the SN-38, have been detected. The conjugate clears completely within 7 days, which is consistent with our preclinical studies showing 50% of the SN-38 is released in the serum every day. Dr. Starodub commented, "Our experience in the IMMU-132 trial has shown promising efficacy results with a manageable and acceptable safety profile in multiple patient populations, including those with limited therapy options, such as triple-negative breast cancer and small-cell lung cancer." "IMMU-132 continues to produce encouraging results as more patients with advanced solid cancers are enrolled into our expansion trial," said Cynthia L. Sullivan, President and Chief Executive Officer. "We believe this SN-38-containing ADC that targets the TROP-2 antigen has the potential to be a novel platform technology for the therapy of diverse metastatic solid cancers," she added. Results from 13 pancreatic cancer patients with CT-assessments also showed a high disease control rate, but are not included in this report because they will be presented at the upcoming AACR Special Conference on Pancreatic Cancer in May, 2014. The pancreatic cancer patient part of the study was supported in part by Award Number R43CA171388 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.