Trastuzumab Biosimilar Demonstrates Sufficient Efficacy in HER2+ Advanced Gastric Cancer

Trastuzumab-pkrb (Herzuma, CT-P6; Celltrion, Inc), a biosimilar to trastuzumab (Herceptin; Genentech), demonstrated sufficient efficacy and no new safety concerns in patients with HER2-positive (HER2+) advanced gastric cancer. These data, which were published in Oncology and Therapy, offer evidence that Herzuma can be an effective, cost-efficient alternative to its reference product.¹

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Trastuzumab is an FDA-approved antineoplastic biologic that targets HER2+ breast and gastric cancer. It was approved in 1998, making it one of the first available “targeted” chemotherapies for patients. Trastuzumab deruxtecan is a trastuzumab conjugate that releases its cytotoxic components after binding and entering HER2-expressing cells, treating HER2+ gastric, lung, colorectal, and metastatic breast cancers.²

Herzuma is indicated in adult patients as a monotherapy or as part of a combination therapy in adjuvant breast cancer, metastatic breast cancer, and metastatic breast cancer. As a biosimilar, Herzuma is a large, complex molecule that is highly similar to and has no clinically meaningful differences in safety, purity, and potency from its reference product, Herceptin.³ A study published in Expert Opinion on Biological Therapy⁴ in 2019 demonstrated that the biosimilar’s mechanism of action, both as a monotherapy and in combination with paclitaxel (Taxol; Bristol Myers Squibb) or pertuzumab (Perjeta; Genentech), was similar to that of trastuzumab when used to treat HER2+ breast cancer and gastric cancer.

For the current study, the investigators aimed to confirm Herzuma’s effects in HER2+ gastric cancer. A total of 171 patients with HER2+ unresectable advanced or recurrent gastric cancer were enrolled from August 2018 until August 2022 in a postmarketing, prospective surveillance study. Baseline patient demographics and pathological features of tumors—including location, histology, HER2 status, and metastatic sites—were collected. Additionally, information on prior surgery and treatment with chemotherapy, as well as the use of concomitant medications with Herzuma, was recorded.¹

The key safety data were monitored before and during treatment with Herzuma, including cardiac examinations, respiratory evaluations, and laboratory tests. Patients received treatment according to the approved dosage and dosing interval (8 mg/kg for the first dose, followed by 6 mg/kg every 3 weeks). There were no specific chemotherapy regimens to be combined with the study drug. Patients were followed up for 1 year after the initiation of Herzuma administration.¹

Overall, the objective response rate was approximately 34.4% in those receiving Herzuma, and the disease control rate was 82.4%. The progression-free survival (PFS) was about 7.4 months, and significant risk factors for PFS included gastroesophageal junction, 3 or more metastases, no gastrectomy, prior chemotherapy, and no platinum agent.¹

The findings indicated that Herzuma was primarily combined with fluoropyrimidine and/or platinum-based agents. Adverse events occurred in approximately 88.3% of patients (n = 151), of which 32.3% (n = 55) experienced grade 3 or higher. Specifically, infusion reactions occurred in 12.3%. A total of 4 cardiac disorders were reported, of which 2 were grade 1 cardiac dysfunction and the remaining 2 were severe ischemic heart disease. Interstitial lung disease was reported in 2.3% of patients (n = 4).¹

“The results of this prospective cohort study confirm that [Herzuma] presented no new safety issues and exhibited sufficient efficacy in various treatment settings and combination regimens. In Japan, biosimilars such as [Herzuma] are priced lower than the originator owing to government regulations aimed at reducing health care costs,” concluded the study authors. “As a result, [Herzuma] is considered a cost-effective alternative to the originator trastuzumab in the treatment of HER2+ advanced gastric cancer.”¹

REFERENCES

1. Taniguchi H, Nishikawa K, Haneji T, et al. Prospective Cohort Study of Trastuzumab Biosimilar CT-P6 in HER2-Positive Gastric Cancer: Japanese Real-World Outcomes. Oncol Ther. 2025;13,485–503. doi:10.1007/s40487-025-00341-7

2. National Library of Medicine – National Center for Biotechnology Information. Trastuzumab. Accessed August 5, 2025. https://www.ncbi.nlm.nih.gov/books/NBK532246/

3. Herzuma (trastuzumab-pkrb). About Biosimilars. Accessed August 5, 2025. https://www.herzumahcp.com/about-biosimilars

4. Jeong SA, Choi JM, Park JM, et al. Mechanism of action of the trastuzumab biosimilar CT-P6. Expert Opin Biol Ther. 2019;19(10):1085-1095. doi:10.1080/14712598.2019.1554052