Breast cancer.

The FDA recently approved the biosimilar trastuzumab-dttb (Ontruzant^®, Samsung Bioepis Co, Ltd) at a multi-dose of 420 mg for treating patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer.

Biosimilars are biological agents made from living organisms and are "similar" to another biologic drug that is already FDA approved. Trastuzumab-dttb, a biosimilar that references trastuzumab (Herceptin^®, Genentech), has been previously approved by the FDA at a 150 mg single-dose vial to treat patients with HER2-overexpressing breast cancer, metastatic breast cancer, and metastatic gastric cancer or gastroesophageal junction adenocarcinoma for patients who are treatment-naive for metastatic disease.

Approval was based on a phase 3 trial (NCT02149524) that enrolled 875 patients with HER2-positive early breast cancer. Patients were randomized in a 1:1 ratio to receive either trastuzumab-dttb or trastuzumab. After a median follow-up of 3 years, the researchers found that the incidence of side effects were comparable between groups, as well as event-free survival (93.7% for trastuzumab-dttb and 93.4% for trastuzumab).

Trastuzumab-dttb is also now approved for adjuvant treatment of HER2-overexpressing node-positive or node-negative breast cancer including as a part of a treatment regimen containing doxorubicin, cyclophosphamide, and either paclitaxel or docetaxel, with docetaxel and carboplatin, or as a single agent following multi-modality anthracycline-based therapy. In addition, trastuzumab-dttb can be used in combination with paclitaxel for the first-line treatment of HER2-overexpressing metastatic breast cancer, as well as a single agent for treating patients with HER2-overexpressing breast cancers who have already received one or more chemotherapy regimens for metastatic disease.

For patients with breast cancer treated with trastuzumab-dttb, the most common treatment-related adverse events include fever, nausea, vomiting, infusion reactions, diarrhea, infections, increased cough, headache, fatigue, dyspnea, rash, neutropenia, anemia, and myalgia. This adverse event profile was comparable to trastuzumab.

For More Information

Clinicaltrials.gov (2020). A study to compare the effect of SB3 and Herceptin® in women with HER2 positive breast cancer. NLM identifier: NCT02149524.

Pivot X, Bondarneko I, Nowecki Z, et al (2018). A phase III study comparing SB3 (a proposed trastuzumab biosimilar) and trastuzumab reference product in HER2-positive early breast cancer treated with neoadjuvant-adjuvant treatment: final safety, immunogenicity and survival results. Eur J Cancer, 93:19-27. DOI:10.1016/j.ejca.2018.01.072

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