Double-blind, randomized phase III study to compare the efficacy and safety of trastuzumab and its biosimilar candidate CT-P6 in HER2 positive early breast cancer (EBC)

Abstract

Background: CT‐P6 is a proposed biosimilar to Reference Trastuzumab (RTZ). This trial (2013‐004525‐84) evaluated the similarity of CT‐P6 and RTZ in efficacy and safety for HER2+ EBC. Methods: 549 patients with HER2+ EBC were randomized to receive CT‐P6 (n=271) or RTZ (n=278) in combination with docetaxel (Cycles 1‐4) and 5‐fluorouracil, epirubicin and cyclophosphamide (Cycles 5‐8). CT‐P6 or RTZ was administered at 8 mg/ kg (Cycle 1 only) followed by 6 mg/kg every 3 weeks. After surgery, patients received CT‐P6 or RTZ monotherapy up to 10 cycles. The primary endpoint was pathological complete response (pCR) rate at surgery. Secondary endpoints were overall response rate (ORR), PK, PD and safety. Results: The pCR rate was 46.8% in CT‐P6 and 50.4% in RTZ. The 95% CIs for the estimate of treatment difference were within the equivalence margin (±0.15) in both PPS and ITT. The proportion of patients with at least 1 SAE was 7.4%in CT‐P6 and 11.9% in RTZ over 1‐year treatment. 6 patients (3 in CT‐P6 and 3 in RTZ) withdrew treatment due to significant LVEF decrease. Infusion related reaction was reported for 11.4% of patients in CT‐P6 and 10.4% of patients in RTZ. Conclusions: This study demonstrated the equivalence of efficacy between CT‐P6 and Reference Trastuzumab in EBC patients. Secondary efficacy endpoints also supported the similarity for two study drugs. CT‐P6 was well tolerated with a similar safety profile to that of Reference Trastuzumab through the neoadjuvant and adjuvant period. (Figure Presented).