The FDA approved trastuzumab-dttb (Ontruzant, Samsung Bioepis) for all eligible indications of the reference product, Herceptin (Genentech).

Trastuzumab-dttb can be used as an adjuvant therapy for HER2-overexpressing breast cancer, metastatic breast cancer, and metastatic gastric cancer or gastroesophageal junction adenocarcinoma in patients who have not received prior treatment for metastatic disease. 

Trastuzumab-dttb is indicated for adjuvant treatment of HER2-overexpressing node-positive or node-negative (estrogen receptor [ER]- or progesterone receptor [PR]-negative or with one high-risk feature) breast cancer as part of a treatment regimen containing doxorubicin, cyclophosphamide, and either paclitaxel or docetaxel; with docetaxel and carboplatin; or as a single agent following multimodal anthracycline-based therapy. (“High risk” is defined as ER- or PR-positive with one of the following features: tumor size greater than 2 cm, age less than 35 years, or tumor grade 2 or 3.)

 Trastuzumab can be used in combination with paclitaxel for the first-line treatment of HER2-overexpressing metastatic breast cancer or as a single agent for the treatment of HER2-overexpressing breast cancer in patients who have received one more chemotherapy regimens for metastatic disease.

Trastuzumab also can be used with cisplatin and capecitabine or 5-fluorouracil for the treatment of patients with HER2-overexpressing metastatic gastric gastroesophageal junction adenocarcinoma, who have not received prior treatment for metastatic disease.

Patients should be selected for treatment based on an FDA-approved companion diagnostic test.

The most common adverse reactions to trastuzumab products in breast cancer were fever, nausea, vomiting, infusion reactions, diarrhea, infections, increased cough, headache, fatigue, dyspnea, rash, neutropenia, anemia and myalgia. In metastatic gastric cancer, they were neutropenia, diarrhea, fatigue, anemia, stomatitis, weight loss, upper respiratory tract infections, fever, thrombocytopenia, mucosal inflammation, nasopharyngitis and dysgeusia.

Trastuzumab carries a boxed warning. Trastuzumab products can result in congestive heart failure and decreased left ventricular ejection fraction, with the greatest risk when administered with anthracyclines. Cardiac function should be evaluated before and during treatment. Trastuzumab should be discontinued if cardiomyopathy occurs.

Trastuzumab administration can result in serious and fatal infusion reactions and pulmonary toxicity. Symptoms usually occur during or within 24 hours of administration. If anaphylaxis, angioedema, interstitial pneumonitis or acute respiratory distress syndrome occurs, the drug should be discontinued.

Trastuzumab can be fetotoxic. For complete prescribing information, click here.

Trastuzumab-dttb is Samsung Bioepis’ first oncology biosimilar to receive FDA approval, and Merck will market and distribute it in the United States.

—Clinical Oncology News Staff