FDA Approves Trastuzumab for Metastatic Gastric/Gastroesophageal Junction Adenocarcinoma

The US Food and Drug Administration (FDA) has approved trastuzumab-dttb (Ontruzant) for the treatment of patients with HER2-overexpressing metastatic gastric or gastroesophageal junction adenocarcinoma in combination with cisplatin and capecitabine or 5-fluorouracil.

Trastuzumab is administered via injection for intravenous (IV) infusion use. Recommended doses for metastatic HER2-overexpressing gastric cancer include an initial dose of 8 mg/kg over 90 minutes IV infusion, followed by 6 mg/kg over 30 to 90 minutes IV infusion every 3 weeks.

The most common adverse reactions observed in this patient population (≥ 10%) include neutropenia, diarrhea, fatigue, anemia, stomatitis, weight loss, upper respiratory tract infections, fever, thrombocytopenia, mucosal inflammation, nasopharyngitis, and dysgeusia.

Samsung Bioepis presented safety and efficacy study results for the biosimilar at 1 year in an abstract at the 2018 San Antonio Breast Cancer Symposium, held in San Antonio, Texas, from December 4 to 8, 2018. The study evaluated patients with HER2-positive early breast cancer or locally advanced breast cancer who were randomized to receive either the biosimilar or its reference concurrently with chemotherapy.

Patients underwent surgery, then received treatment with either SB3 or its reference. Afterward, 367 patients—181 of whom had been treated with the reference trastuzumab and 186 of whom had been treated with the biosimilar—were enrolled.

In a group of patients treated with the reference, 126 patients had been exposed to lots of trastuzumab, with expiry dates from August 2018 to December 2019, that had a lower antibody-dependent cell-mediated cytotoxicity (ADCC) than other lots of the reference product. The remaining 55 patients given the reference therapy were unexposed to these lots. After 30.1 months of treatment with the biosimilar and 30.2 months of treatment with the reference, there was no statistically significant difference in EFS between the biosimilar arm (96.7%) and the patients who were unexposed to the lower-ADCC activity lots of the reference (98.2%) (hazard ratio [HR], 1.19; 95% CI, .23-6.18; P = .8376).

The treatment was also approved for the treatment of patients with HER2-overexpressing breast cancer.

This article was adapted from The Center for Biosimilars.