We show that BAT8003 is effectively internalized upon binding to Trop-2, and inhibits proliferation of Trop2-overexpressed tumor cells with IC50s of ˜1 nM. In a TNBC (MDA-MB-468 cell) mouse xenograft model, BAT8003 strongly inhibits tumor growth at a dose level as low as 5 mg/kg. BAT8003 also demonstrates potent activity in another TNBC (MX-1 cell) mouse tumor model, in which it shows the same inhibition activity as the naked antibody conjugated heterogeneously with almost two fold payload (DAR 3.5), suggesting the effect caused by site-specific conjugation.