Combining a recent review on ADCs in clinical trials [52] and a search of the ClinicalTrials.gov database [53, 54] revealed that our list of cell membrane targets contained the majority of target antigens for ADCs in clinical development for the treatment of breast cancer, with the possible exception of the tumor-associated calcium signal transducer 2 (TACSTD2), a recently identified ADC target for triple-negative breast cancer [55]. The gene discussed is TACSTD2; the disease is breast cancer.