Immunomedics, Inc. has announced its sacituzumab govitecan research received the U.S. Food and Drug Administration (FDA) designation of Fast Track development program for the treatment of triple negative breast cancer (TNBC) patients who failed to respond to previous therapies for metastatic disease. Sacituzumab govitecan (IMMU-132) is an investigational antibody-drug conjugate (ADC) that consists of hRS7, a humanized antibody binding to the trophoblast cell-surface antigen (TROP-2), conjugated with an active irinotecan metabolite, SN-38. While this metabolite is already in use to treat several types of tumors, the TROP-2 antigen is present in many tumor cells, including breast, colon, lung and prostate, but somewhat absent in healthy cells. This novel antibody binds to cancer cells that express TROP-2 and becomes internalized, allowing the specific delivery of its toxic SN-38 agent. FDA’s Fast Track designation was based on the company’s promising results in TNBC patients, along with their research plans to develop sacituzumab govitecan. Preliminary clinical results have shown that in patients who have had an average of 4 prior therapies, 30% has shown complete and partial remissions by computed tomography, with 30 to 100% rates of tumor shrinkage.