TACSTD2 and breast cancer: SG is composed of humanized RS7 (hRS7) anti-Trop-2 monoclonal antibody that delivers SN-38, the active metabolite of irinotecan and a topoisomerase inhibitor, to Trop-2-expressing cells which is expressed on 93% of triple-negative and 50% of HR + breast cancer cells [8, 9].