The co-expression of multiple different ADC targets within the same tumor provides an opportunity for the development of future clinical trials involving combinations of ADCs or the creation of bi-specific ADCs, for example, combining anti-NECTIN4 with anti-Trop-2 in lung, breast, and ovarian cancer or anti-HER2 with anti-ERBB3 in lung, breast, and prostate cancer [54,63]. The gene discussed is ERBB2; the disease is Familial prostate cancer.