FDA approves third trastuzumab biosimilar


The Food and Drug Administration has approved a biosimilar trastuzumab product for the treatment of HER2-overexpressing breast cancer and HER2-ovexpressing metastatic gastric or gastroesophageal junction adenocarcinoma.

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Ontruzant (trastuzumab-dttb), marketed by Samsung Bioepis, is the third approved biosimilar to Genentech’s Herceptin in the United States.

Patients should be selected for treatment with Ontruzant using an FDA-approved companion diagnostic for a trastuzumab product.

The prescribing information for the newly approved biosimilar includes a boxed warning highlighting the risk of cardiomyopathy, infusion reactions, embryo-fetal toxicity, and pulmonary toxicity associated with the drug.

Ontruzant was shown to be equivalent to Herceptin in a phase 3 study (Eur J Cancer. 2018 Apr;93:19-27).

The trial included 875 patients with HER2-positive early breast cancer. Patients were randomized to receive Ontruzant or Herceptin for eight cycles concurrently with chemotherapy. The chemotherapy consisted of four cycles of docetaxel followed by four cycles of 5-fluorouracil/epirubicin/cyclophosphamide.

The patients then underwent surgery, which was followed by 10 cycles of Ontruzant (n=380) or Herceptin (n=384).

The median follow-up was 437 days in the Ontruzant arm and 438 days in the Herceptin arm. Safety and efficacy results were similar between the treatment arms.

Treatment-emergent adverse events occurred in 97.5% of patients in the Ontruzant arm and 96.1% of those in the Herceptin arm.

The 12-month event-free survival rate was 93.7% in the Ontruzant arm and 93.4% in the Herceptin arm.

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