The anti-human epidermal growth factor receptor 2 (HER2) monoclonal antibody trastuzumab is indicated for treatment of HER2-positive early breast cancer (EBC), metastatic breast cancer (MBC) and metastatic gastric cancer (MGC). Often used in conjunction with chemotherapy, trastuzumab was originally approved as an intravenous (IV) formulation. Subcutaneous (SC) formulations were more recently approved for HER2-positive breast cancer in 2013 (Europe)  and 2019 (US) .
After European Union (EU) and US patent expirations for IV trastuzumab, five IV trastuzumab biosimilars were developed and recently approved in both Europe and the US. The approvals of SC trastuzumab and new IV trastuzumab biosimilars create multiple options for patients and their providers. The anticipated patent expiration of SC trastuzumab will likely result in development of SC trastuzumab biosimilar formulations as well. Waller and colleagues have provided a timely review comparing IV and SC formulations of trastuzumab, in addition to discussing the potential benefits of available IV trastuzumab biosimilars .
Several studies have verified the similarity of pharmacological and clinical profiles of IV and SC trastuzumab. Efficacy profiles of both formulations are remarkably comparable, and no new safety signals have been reported with use of SC formulations or when switching between formulations (IV to SC or vice versa). Given these similarities, treatment considerations can be guided by patient preferences and cost. In two clinical trials, patients reported a preference for SC over IV administration. However, the IV formulation may be appropriate due to prior placement of a central venous port when administered in conjunction with other therapies.
Trastuzumab SC formulations may reduce costs over an entire treatment course compared with IV formulations due to drug costs, provider time and consumables. However, biosimilars offer more substantial cost savings. Biosimilars in general may provide discounts from 30% to 69% over reference products, with potential savings of > US$50 billion over a decade in the US. Single-year savings from the use of trastuzumab biosimilars have been estimated from €0.26 to €0.69 million in Croatian patients with EBC or MBC and from €58 to €68 million in patients with EBC, MBC or MGC in 28 European countries.
As the relatively high cost of biological therapies can be a significant deterrent to clinical use, increased access to biosimilars could eliminate this barrier to treatment. Given the substantial savings associated with the use of trastuzumab biosimilars and their comparable clinical benefits to reference products, efforts should be made to provide comparative cost analyses and education to healthcare providers regarding their use. The availability of multiple formulations of both reference trastuzumab and trastuzumab biosimilars is likely to enhance the quality of individualized patient care in certain cancers.
Conflict of interest
The authors of the research paper  reported conflicts of interest, including being a consultant/advisory board member for Mylan and being an employee of Mylan. For full details of the authors’ conflict of interest, see the research paper .
Abstracted by Professor Dr Cornelius Waller, Department of Haematology, Oncology and Stem Cell Transplantation, University Medical Centre Freiburg and Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Readers interested to learn more about clinical trials for trastuzumab biosimilars and SC biosimilars are invited to visit www.gabi-journal.net to view the following manuscripts published in GaBI Journal:
Clinical trials for trastuzumab biosimilars
Is the local tolerance of injectable biosimilars too underestimated?
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1. GaBI Online - Generics and Biosimilars Initiative. Biosimilars approved in Europe [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Apr 30]. Available from: www.gabionline.net/Biosimilars/General/Biosimilars-approved-in-Europe
2. GaBI Online - Generics and Biosimilars Initiative. Biosimilars approved in the US [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Apr 30]. Available from: www.gabionline.net/Biosimilars/General/Biosimilars-approved-in-the-US
3. Waller CF, Möbius J, Fuentes-Alburo A. Intravenous and subcutaneous formulations of trastuzumab, and trastuzumab biosimilars: implications for clinical practice. Br J Cancer. 2021;124(8):1346-52.
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