This thesis investigates the safety profiles of HER2-targeted biologics, focusing on trastuzumab and its biosimilars using real-world pharmacovigilance data. It compares reported adverse drug reactions between the originator product and its biosimilars. The most commonly reported adverse events were consistent with known effects of HER2-targeted therapies and their combination with chemotherapy. While there was a high degree of overlap in safety profiles, some differences in reported reactions were observed. Overall, the findings support comparable safety between biologics and biosimilars, while emphasizing the need for continued post-marketing surveillance.