Breast Cancer Biosimilar Demonstrates Equivalent Efficacy to Trastuzumab

The biosimilar CT-P6 demonstrated equivalent efficacy to the reference drug trastuzumab (Herceptin) in patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer.

For the study, published in The Lancet, investigators sought to establish the equivalence of CT-P6 to reference trastuzumab in neoadjuvant therapy of HER2-positive early-stage breast cancer.

Included in the randomized, double-blind, active-controlled, phase 3 equivalence trial were 549 women, 18 years or older, with stage 1 to 3a operable HER2-positive breast cancer from 112 centers in 23 countries.

Between August 2014 and May 2016, the participants were randomized 1:1 to receive either neoadjuvant CT-P6 or reference trastuzumab intravenously for 8 cycles plus neoadjuvant docetaxel and fluorouracil (FEC), epirubicin, and cyclophosphamide therapy.

The participants underwent surgery within 3 to 6 weeks of the final neoadjuvant study drug dose, followed by an adjuvant treatment period of up to 1 year. Long-term safety and efficacy were monitored for 3 years.

The primary endpoint was pathological complete response assessed via specimens obtained during surgery and analyzed by masked central review of local histopathology reports. The equivalence margin—–defined as clinically meaningful differences in efficacy between the biosimilar and reference product––was -0.15 to 0.15.

The results of the study showed that a similar proportion of patients achieved pathological complete response with CT-P6 (116 of 348 patients) and reference trastuzumab (229 of 256 patients). The estimated treatment outcome difference was within the equivalence margin.

Serious treatment-emergent adverse events (AEs) occurred in 7% of patients in the CT-P6 group and 8% in the reference trastuzumab group. The most commonly reported serious AEs were febrile neutropenia and neutropenia.

Grade 3 or worse AEs were reported in 6% of patients in the CT-P6 group compared with 8% in the reference trastuzumab group, with the most frequent AE observed as neutropenia.

“CT-P6 showed equivalent efficacy to reference trastuzumab and adverse events were similar,” the authors concluded. “Availability of trastuzumab biosimilars could increase access to this targeted therapy for HER2-positive early-stage cancer.”

An estimated 1 of 5 women diagnosed with breast cancer worldwide will have HER2-positive breast cancer. Current treatment options included trastuzumab, which has improved survival rates by more than 30% among women with stage 1 to 3 HER2-positive breast cancer.