Immunomedics Reports Durable Responses in Patients With Advanced Solid Cancers After Therapy With Sacituzumab Govitecan

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Immunomedics, Inc.,
IMMU
today announced that sacituzumab govitecan, the Company's lead investigational antibody-drug conjugate (ADC), produced durable responses that exceeded one year in some patients with metastatic triple-negative breast (TNBC), small-cell (SCLC) and non-small-cell lung (NSCLC) cancers. In other patients with less than 1 year of response duration, their responses are continuing. Dr. David M. Goldenberg, Chairman, Chief Scientific Officer and Chief Patent Officer, presented the results at the 2015 World ADC San Diego conference. The presentation on TNBC focused on those patients who relapsed after 2 or more prior lines of therapy that included taxane, a class of chemotherapy agents used to treat solid cancers, such as breast, gastric, head and neck, lung, ovarian, pancreatic, and prostate. At the time of this analysis, 56 enrolled patients had received sacituzumab govitecan at the optimal dose of 10 mg/kg given on days 1 and 8 of a 3-week cycle, and in some patients the therapy continued for many months. The median number of prior lines of therapy for the patients enrolled with metastatic TNBC was 5 (range, 2 – 12). Treatment response, assessed by computed tomography (CT) according to the rules set by the Response Evaluation Criteria In Solid Tumors (RECIST 1.1), was available for 52 patients. The objective response rate was 29% (15/52), with 2 confirmed complete responses. The interim median progression-free survival (PFS), a measure of time patients are living without their cancer progressing, was 7.0 months, which appears to be longer than the best PFS results in this patient setting achieved by currently-used agents. Forty-six percent of these TNBC patients had experienced a PFS event. Overall survival (OS) data were too early to report because 86% of patients are still alive. For metastatic lung cancers, a total of 33 patients with NSCLC, having received a median of 3 (range, 1 – 7) prior therapies, were enrolled to receive sacituzumab govitecan at the 8.0 mg/kg or 10 mg/kg dose level. Among the 29 patients that were assessable, an objective response (partial response) rate of 28% (8/29) was observed, including patients with both squamous cell and adenocarcinoma NSCLC types. For the 25 patients at the 10 mg/kg dose, the interim median PFS was 3.8 months, with 48% of patients in this dose group having experienced a PFS event. In SCLC, of the 27 patients, with a median of 3 prior therapies (range 1 – 5), enrolled at the doses of 8.0 mg/kg and 10 mg/kg, 25 were assessable for response. Six patients achieved a partial response (objective response rate = 24%). Interim median PFS for the 12 patients at the 10 mg/kg dose level was 3.6 months and 83% of patients had experienced a PFS event. Since 96% of NSCLC patients and 100% of SCLC patients were still alive at the time of analysis, OS data at the optimal dose of 10 mg/kg are too early to report. Dr. Goldenberg also presented results, for the first time, on 15 patients with metastatic urothelial cancers, mostly urinary bladder cancers. At the time of analysis, 6 of 11 patients who relapsed to a prior platinum-containing therapy and evaluable by CT achieved a partial response (objective response rate = 55%), with 5 patients still continuing treatment. Sacituzumab govitecan continues to demonstrate a highly tolerable safety profile. Among the 261 patients enrolled to-date, only 8 patients had reported adverse events that temporarily interrupted the infusion. In the 118 patients receiving the ADC at the dose of 10 mg/kg, the major toxicity reported was Grades 3 or 4 neutropenia in 20% of patients. "These efficacy and safety results reaffirm the high therapeutic index of sacituzumab govitecan in TROP-2-expressing solid cancers, which, we believe, distinguishes it from other ADCs approved or in development," remarked Cynthia L. Sullivan, President and Chief Executive Officer. "The Phase 2 study will be further updated at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics in November, and the San Antonio Breast Cancer Symposium in December," Ms. Sullivan added. Ms. Sullivan further commented, "We continue to advance our regulatory preparations with the FDA to move sacituzumab govitecan to a Phase 3 registration trial in patients with late-stage, metastatic TNBC, while we also focus on our business development activities for this agent. We will continue to expand our studies in patients with metastatic NSCLC, SCLC, and urothelial cancer. We believe this novel ADC will also show important activity in other cancer types, based on preclinical and early clinical results." Sacituzumab govitecan is a first-in-class ADC developed by the Company by conjugating the moderately-toxic drug, SN-38, site-specifically and at a high ratio of drug to antibody, to a humanized antibody that targets the TROP-2 receptor expressed by many solid cancers. The ADC has received Fast Track designation from the FDA for the treatment of patients with TNBC, SCLC and NSCLC, and has also been designated an orphan drug for the treatment of patients with SCLC or pancreatic cancer in the U.S., and for the treatment of patients with pancreatic cancer in the European Union.
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