Immunomedics Announces Expanded Phase 1/2 Trials Which Confirm Activity, Good Safety Profile of IMMU-132

Immunomedics, Inc.,

today announced that sacituzumab govitecan, the Company's novel investigational antibody-drug conjugate (ADC), continues to produce a partial response (PR) rate of 30% and a 70% clinical benefit rate (CBR), defined as PR and stable disease, in patients with metastatic triple-negative breast cancer (TNBC) who had been heavily pretreated. For patients with PR or stable disease longer than 6 months, the CBR was 40%. Significantly, PRs ranging from 30% to 70% tumor shrinkage as best response were reported. Responses are measured by computed tomography (CT) based on RECIST 1.1 criteria. Dr. Aditya Bardia of Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA, presented the Phase 1/2 study at the San Antonio Breast Cancer Symposium in San Antonio, TX. Commenting on the results, Dr. Bardia stated, "TNBC patients in this late-stage setting have limited treatment options that are effective. We are quite encouraged with this experience with sacituzumab govitecan, especially the time-to-progression results, which showed that the duration of response for the responding patients was generally longer than their last prior therapy for TNBC." As the name implies, TNBC represents breast cancers that are negative for estrogen and progesterone receptors, as well as human epidermal growth factor receptor 2, or HER2. This type of breast cancer comprises about 15-20% of all invasive breast cancers and is more prevalent in young and African-American women. Despite the fact that initial responses with chemotherapy are high, TNBC characteristically has a high recurrence rate and is perhaps the most difficult type of breast cancer to treat successfully with current cytotoxic agents. According to a published report, the median survival for patients with metastatic triple-negative breast cancer is estimated to be 13 months.^1 Currently, there are no targeted treatments available for TNBC. More than 40 patients with relapsed or refractory metastatic TNBC have been enrolled into the multicenter study, of which 23 patients were evaluable with at least one post-therapy CT assessment. These patients had a median of 4 prior therapies (range 1-15) with taxane, a FDA-approved drug for breast cancer treatment, alone or in combination with other chemotherapeutic agents or investigational drugs. The adverse event profiles for 21 patients were available at the time of reporting. Transient neutropenia (9 patients) was the major Grade 3 or 4 toxicity, while manageable diarrhea (11 patients) was the main Grade 1 or 2 event. No patient discontinued therapy due to toxicity. "After we have completed patient enrollment into this study, which is expected by the end of this month, we plan to discuss the registration pathway for this valuable agent in breast cancer with FDA and our medical advisers," remarked Cynthia L. Sullivan, President and Chief Executive Officer. "Furthermore, discussions with potential corporate partners are ongoing," Ms. Sullivan added. In addition to Dr. Bardia of Massachusetts General Hospital, the multicenter study also involved Dr. Alexander Starodub, Indiana University Health Center for Cancer Care, Goshen, IN; Dr. Rebecca L. Moroose, UF Health Cancer Center, Orlando, FL; Dr. Ingrid A. Mayer, Breast Cancer Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN; Dr. Jennifer R. Diamond, University of Colorado Cancer Center, Aurora, CO; Drs. Ellen Chuang, Allyson J. Ocean, and Linda T. Vahdat, Weill Cornell Medical College, New York, NY. In a separate presentation at this year's Symposium, Dr. David M. Goldenberg, Chief Scientific Officer, described the Company's ADC technology, which uses a moderately-toxic drug, SN-38, the active metabolite of irinotecan, conjugated to an anti-TROP-2 antibody at a drug to antibody ratio of 7.6, which is about twice that of other ADCs, for the creation of sacituzumab govitecan. With the use of a moderately-toxic drug, patients were able to tolerate a dosing schedule of once a week for two weeks followed by one week of rest in a 3-week cycle, which increases the therapeutic index of the ADC. Indeed, sacituzumab govitecan has also demonstrated activity in other solid tumors, producing PRs in patients with colorectal, esophageal, small-cell and non-small-cell lung, and urinary bladder cancers. Despite repeated dosing, no antibodies against the ADC, either to the antibody or to the SN-38, have been detected.