Representative cytotoxicity experiments (Effector to target: E/T; 25:1 and 50:1) using hRS7 against the Trop-2-positive cell line (i.e., EEC-ARK-1, upper panel) versus the Trop-2-negative cancer cell lines (i.e., EEC-ARK-2, middle panel and EEC-ARK-3, lower panel). High levels of hRS7 induced cytotoxicity were evident against EEC-ARK-1 primary cell line expressing high levels of Trop-2. In contrast, negligible cytotoxicity was detectable against EEC-ARK-2 and EEC-ARK-3 (i.e., low Trop-2 expressor cell lines). In all cell lines tested, no significant cytotoxicity was detected in the absence of hRS7 or in the presence of rituximab control mAb.