Safety Evaluation of Initial CT-P6 Administration for 30 min during the Switch from Reference Trastuzumab in Maintenance Infusion: A Multicenter Observational Study.

CT-P6 is a biosimilar of trastuzumab and is recommended to be administered for 30-90 min in subsequent maintenance infusions to prevent infusion-related reactions (IRRs). We administered CT-P6 for 30 min as the first injection and as an alternative to reference trastuzumab in the maintenance infusion and evaluated the safety of the administration. A total of 140 patients with breast or gastric cancer, who received a switch from tri-weekly reference trastuzumab to CT-P6 for 30 min in maintenance infusions, were retrospectively evaluated. Premedication was administered prior to an infusion of CT-P6 and a cytotoxic agent. However, premedication was not provided when CT-P6 was co-administered with pertuzumab or administered alone. The primary endpoint was the incidence of IRRs. The secondary endpoint was the incidence of diarrhea and skin toxicity. Ninety-five percent of the patients had breast cancer, and 44.3% had advance-stage cancer. The treatment included CT-P6 alone (17.9%) or with cytotoxic agents (23.6%), antihormonal drugs (25.7%), and pertuzumab (62.9%). Median administration time of trastuzumab at the switch was 13 administrations (range 2-140). Premedication was administered to 20.7% patients. One patient (0.7%) experienced grade 3 IRR. The frequency of diarrhea in the reference trastuzumab group and the CT-P6 group was 7.1 and 6.4%, respectively, and that of skin toxicity was 6.4 and 5.0%, respectively, without differences. In conclusion, we first demonstrated that an initial CT-P6 administration for 30 min during the switch from reference trastuzumab in maintenance infusion is an acceptable administration method.