Immunomedics Provides Update On Phase 2 Study Of Isactuzumab Govitecan In Patients With Diverse Metastatic Solid Cancers

Immunomedics, Inc.,

today announced that isactuzumab govitecan (IMMU-132), the Company's proprietary solid-tumor antibody-drug conjugate (ADC), continues to produce encouraging results in a Phase 2 clinical trial in heavily-pretreated patients with diverse, metastatic solid cancers. The provisional results were presented by Dr. David M. Goldenberg, Chairman, Chief Scientific Officer, and Chief Medical Officer, at the 5th Annual World ADC Summit in San Diego, CA. In 113 patients who have received at least one dose of isactuzumab govitecan, treatments with the ADC resulted in at least 64 patients (57%) with partial responses and disease stabilization. All lesions were measured by computed tomography (CT) based on RECIST 1.1 criteria. The major responses were observed among patients with 6 different advanced cancers, including triple-negative breast, small-cell and non-small-cell lung, colorectal, esophageal, and urinary bladder cancers. The ADC was well tolerated at the Phase 2 dose used in the trial expansion, with neutropenia being the major toxicity, and about 10% of patients having grade 3 and 4 other toxicities. This suggests a higher therapeutic index (ratio of therapeutic benefit to toxicity) than historical results with irinotecan, SN-38's parent compound. "We are most encouraged with the results in patients with triple-negative breast cancer, small-cell and non-small-cell lung cancers, especially in these patients who have late-stage diseases," remarked Cynthia L. Sullivan, President and Chief Executive Officer. "We plan to complete the Phase 2 study before the end of this year. Discussions with key opinion leaders, as well as potential corporate partners, on the further development of this valuable agent are ongoing," Ms. Sullivan added. Isactuzumab govitecan is made up of SN-38, the active metabolite of irinotecan, conjugated to the Company's humanized anti-TROP-2 antibody. TROP-2 is expressed by many human tumors, such as cancers of the breast, cervix, colon and rectum, kidney, liver, lung, ovary, pancreas, and prostate, but with only limited expression in normal human tissues. Preclinical studies have indicated that isactuzumab govitecan delivers up to 135-times the amount of SN-38 to a human pancreatic tumor xenograft than when irinotecan is given. In patients who relapsed or were refractive to prior topoisomerase I or II inhibitors, this ADC demonstrated subsequent activity, suggesting that it can overcome resistance to such inhibitors, including irinotecan. In addition to isactuzumab govitecan (IMMU-132), the Company is also developing another SN-38 based ADC, labetuzumab govitecan (IMMU-130), for the treatment of patients with metastatic colorectal cancer. The clinical study of this agent is advancing into a Phase 2 trial, with some patients under therapy for many months and showing long-term disease control after failing prior irinotecan-containing regimens. Here again, despite the frequent dosing, the ADC appears to be well tolerated by patients, with transient and reversible neutropenia, and manageable diarrhea the major side effects, which were mild and irregular.