Real-world safety and effectiveness of CT-P6 (biosimilar trastuzumab): A post-marketing surveillance study in Korea

e13025 Background: CT-P6 is a biosimilar trastuzumab product approved in many countries worldwide, including the European Union and the United States. This study aims to confirm the safety and effectiveness of CT-P6 in routine clinical practice settings for the approved indications of HER2-positive metastatic breast cancer (MBC), early breast cancer (EBC), and metastatic gastric cancer (MGC) in the Republic of Korea. Methods: The observational, prospective, multi-center, post-marketing surveillance (PMS) study was conducted from October 5, 2018 to October 4, 2022, on Korean patients diagnosed with MBC, EBC or MGC and newly treated with CT-P6 regardless of previous treatment of trastuzumab products other than CT-P6. Patients receiving at least one CT-P6 treatment according to the prescribing information and being monitored for safety and effectiveness were included in these analyses. Safety was evaluated by all types of adverse events (AEs), including adverse drug reaction (ADR), and serious adverse event (SAE); for up to a year after the first dose of CT-P6. Safety was further summarized by background factors (demographic and clinical characteristics) for subgroup analysis to identify variables independently affecting the incidence proportion. As for effectiveness, disease-specific clinical response (by best overall response for MBC and MGC; disease progression, and pathologic complete response (pCR) for EBC) were assessed for up to one year. Results: The safety population included 642 patients (94 MBC, 494 EBC, 54 MGC). For patients with MBC, AEs occurred in 71.28%, ADRs in 48.94%, and SAEs in 19.15%. For EBC, AEs occurred in 43.52%, ADRs in 26.52%, and SAEs in 6.48%. In case of MGC, AEs occurred at a rate of 79.63%, ADRs at 40.74%, and SAEs at 14.81%. Overall, the incidence of ADR was statistically different for groups ≥65 of age ( p=0.0323); comorbidity or complication, especially with cardiac disorder ( p=0.0018); and previous chemotherapy ( p=0.0002). In terms of effectiveness, positive outcomes were observed. Conclusions: CT-P6 administered to Korean patients according to the prescribing information was well tolerated, with no new safety signals identified. The safety and efficacy profiles of CT-P6 in a real-world population were consistent with those observed in the previous clinical studies. [Table: see text]