Trastuzumab is a monoclonal antibody that interferes with the human epidermal growth factor receptor 2 (HER2)/neu receptor. In some cancers, notably certain types of breast cancer, HER2 is overexpressed, and causes cancer cells to reproduce uncontrollably. Trastuzumab is therefore used to treat certain breast cancers.

In this international, multicentre, double-blind, randomized, clinical trial, the equivalence of CT‑P6 (trastuzumab) was compared to Herceptin (trastuzumab) in terms of efficacy and safety in 549 patients with HER2+ early breast cancer (EBC).

The results of the study were presented at the American Society of Clinical Oncology (ASCO) annual meeting ASCO 2017, which was held in Chicago, Illinois, USA on 2−6 June 2017.

Patients were randomly assigned into two groups at a ratio of 1:1 to receive CT‑P6 (n = 271) or Herceptin (n = 278) in combination with docetaxel (Cycles 1−4) and 5‑fluorouracil, epirubicin and cyclophosphamide (Cycles 5−8). The drugs were administered at 8 mg/kg (Cycle 1 only) followed by 6 mg/kg every 3 weeks.

The pathological complete response (pCR) rate at surgery was 46.8% for CT‑P6 and 50.4% for Herceptin. The 95% confidence intervals (CIs) for the risk ratio estimate were within the equivalence margin (0.74, 1.35) in the per-protocol and intention-to-treat analysis sets. Other efficacy endpoints were similar between CT‑P6 and trastuzumab. The proportion of patients with at least one treatment-emergent serious adverse event (SAE) was 6.6% for CT‑P6 and 7.6% for trastuzumab. Only one patient in each group withdrew treatment due to significant left ventricular ejection fraction decrease. Infusion-related reaction was reported for 8.5% of patients in CT‑P6 and 9.0% of patients in trastuzumab.

The authors concluded that ‘this study demonstrated the similarity of efficacy in terms of pCR between CT-P6 and trastuzumab in EBC patients. Secondary efficacy endpoints also supported the similarity between CT-P6 and trastuzumab. CT-P6 was well tolerated with a similar safety profile to that of trastuzumab during the neoadjuvant period’.

Celltrion submitted its candidate trastuzumab biosimilar to the European Medicines Agency (EMA) for approval in November 2016 [2]. The company also submitted CT‑P6 to Japan’s Ministry of Health, Labour and Welfare (MHLW) for approval in April 2017 [3].

Conflict of interest
The authors of the research paper [1] did not provide any conflict of interest statement.

Editor’s comment
It should be noted that data of the study presented in this article were published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Related article
Biosimilars of trastuzumab

References
1. Stebbing J, et al. Double-blind, randomized phase III study to compare the efficacy and safety of CT-P6, trastuzumab biosimilar candidate versus trastuzumab as neoadjuvant treatment in HER2 positive early breast cancer (EBC). ASCO 2017; Chicago, Illinois, USA; 2-6 June 2017.
2. GaBI Online - Generics and Biosimilars Initiative. Celltrion submits trastuzumab biosimilar application to EMA [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2017 Aug 11]. Available from: www.gabionline.net/Biosimilars/News/Celltrion-submits-trastuzumab-biosimilar-application-to-EMA
3.    GaBI Online - Generics and Biosimilars Initiative. Celltrion making progress with biosimilars in China and Japan [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2017 Aug 11]. Available from: www.gabionline.net/Biosimilars/News/Celltrion-making-progress-with-biosimilars-in-China-and-Japan

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