New data show first-line triplet regimen of pembrolizumab, Herzuma® (biosimilar trastuzumab) and chemotherapy are effective in treatment of HER2-positive advanced gastric cancer

  • Data from a phase Ib/II trial show a first-line triple combination therapy of pembrolizumab, Herzuma® (biosimilar trastuzumab) and chemotherapy was effective in patients with HER2-positive advanced gastric cancer (AGC)1
  • Patients experienced clinically significant tumour shrinkage regardless of PD-L1 status with no new safety signals observed 1
  • Access to a first-line immunotherapy/chemotherapy combination with Herzuma® (biosimilar trastuzumab) has the potential to improve patient outcomes whilst reducing overall treatment costs for healthcare systems

INCHEON, South Korea--()--Data presented today as part of the ASCO20 Virtual Scientific Program show that a first-line triplet regimen comprising of pembrolizumab, Herzuma® (biosimilar trastuzumab) and chemotherapy is effective in patients with HER2-positive advanced gastric cancer (AGC). The PANTHERA trial (a phase Ib/II study of first line pembrolizumab in combination with trastuzumab, capecitabine, and cisplatin in HER2-positive gastric cancer), sponsored by Celltrion Inc. and MSD, is investigating the potential of a first-line immunotherapy/chemotherapy combination with biosimilar trastuzumab. This is in light of a growing body of evidence that the immune system contributes to the therapeutic effects of monoclonal antibodies such as biosimilar trastuzumab in treating solid tumours.1

A total of 43 patients were treated with a median follow up of 18 months. Patients were treated with pembrolizumab 200mg via IV infusion D1, biosimilar trastuzumab 6mg/kg (after 8mg/kg load) D1, capecitabine 1000mg/m2 bid D1-D14 and cisplatin 80mg/m2 D1 every 3 weeks.1

The primary endpoint for phase II was the overall response rate (ORR), measured in line with the RECIST 1.1 guidelines. The results showed a significant tumour shrinkage of 95.3% with an ORR of 76.7%. Of these patients, 16.3% exhibited complete response (CR) and 60.5% partial response (PR). Furthermore, PD-L1 status at diagnosis did not have an effect on overall survival (OS) and the data also indicate a disease control rate (DCR) of 97.7%.1

Secondary endpoints for the trial included progression-free survival (PFS), OS, duration of response (DoR) and safety. Molecular analysis was carried out through targeted next generation sequencing (NGS). The median PFS was 8.6 months (95% CI 7.2-16.4) and the median OS was 19.3 months (95% CI 16.5-NA).1 The median duration of response (DOR) was 10.8 months (95% CI 7.17-NA).

Whilst carrying out the study, the investigators did not observe any new safety signals. The most common haematologic adverse events included a decreased neutrophil count, as seen in 46.5% of patients, and anaemia which was experienced by 32.6%. Other frequently reported adverse events included anorexia (39.5%) and nausea (32.6%), and the most observed immune-related adverse event was hypothyroidism (11.6%).1

According to our study, patients with HER2-positive AGC treated with this first-line triplet regimen experienced clinically meaningful improvements in tumour shrinkage regardless of PD-L1 status,” said Professor Sun Young Rha at Yonsei Cancer Center, Yonsei University College of Medicine. “Enabling access to the first immunotherapy/chemotherapy combination with Herzuma® (biosimilar trastuzumab) in the first-line setting will make a real difference to patients.”

Prof Rha added, “With the costs of oncology treatments being so burdensome, the availability of biosimilar trastuzumab could reduce the overall cost by combination treatment with innovative new drugs and chemotherapy. High quality treatments at reduced overall treatment cost could imply a benefit to health systems worldwide.”

-- ENDS --

Notes to Editors:

About metastatic (advanced) gastric cancer2,3,4,5

Gastric cancer is a leading cause of cancer-related deaths worldwide, with over a million new cases of gastric cancer diagnosed each year. HER2 overexpression has been reported in 7-34% of gastric cancers. Gastric cancer commonly begins in the inner lining of the upper part of the stomach and can spread through the walls of the stomach. The cancer can then invade other organs or spread to the lymph vessels and nodes. Gastric cancer can be staged from 0 to IV depending on its progression. As the stage number increases, the larger the cancer growth and the further the cancer has spread.

Clinical trials have evaluated trastuzumab in combination with chemotherapy as first-line treatment for metastatic (advanced) gastric cancer.

About Herzuma® (biosimilar trastuzumab)6

Herzuma® is a humanised monoclonal antibody that is designed to bind selectively to the extracellular domain of an antigen called human epidermal growth factor reception 2 (HER2). Herzuma® is indicated for the treatment of adult patients with early breast cancer, metastatic breast cancer, and metastatic gastric cancer and was approved by the European Medicines Agency (EMA) in February 2018.

Similarity of Herzuma® to the reference product, Herceptin® was demonstrated in terms of pharmacokinetic, pharmacodynamics, efficacy and safety through multiple global clinical trials.6

About Celltrion Healthcare

Celltrion Healthcare is committed to delivering innovative and affordable medications to promote patients’ access to advanced therapies. Its products are manufactured at state-of-the-art mammalian cell culture facilities, designed and built to comply with the US FDA cGMP and the EU GMP guidelines. Celltrion Healthcare endeavours to offer high-quality cost-effective solutions through an extensive global network that spans more than 110 different countries. For more information please visit:

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1 Rha, S., Lee, C., Kim, H., et al. Targeting HER2 in combination with anti-PD-1 and chemotherapy confers a significant tumor shrinkage of gastric cancer: A multi-institutional phase Ib/II trial of first-line triplet regimen (Pembrolizumab, Trastuzumab, Chemotherapy) for HER2 positive advanced gastric cancer (AGC). Poster presented at: ASCO20 Virtual Scientific Program; May 29, 2020
2 Rawla P, Barsouk A. Epidemiology of gastric cancer: global trends, risk factors and prevention. Prz Gastroenterol. 2019;14(1):26‐38. doi:10.5114/pg.2018.80001
3 Rüschoff J, Hanna W, Bilous M, et al. HER2 testing in gastric cancer: a practical approach. Mod Pathol. 2012;25(5):637‐650. doi:10.1038/modpathol.2011.198
4 Kanayama K, Imai H, Usugi E, Shiraishi T, Hirokawa YS, Watanabe M. Association of HER2 gene amplification and tumor progression in early gastric cancer. Virchows Arch. 2018;473(5):559‐565. doi:10.1007/s00428-018-2433-y
5 Bang YJ, Van Cutsem E, Feyereislova A, et al. Trastuzumab in combination with chemotherapy versus chemotherapy alone for treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA): a phase 3, open-label, randomised controlled trial [published correction appears in Lancet. 2010 Oct 16;376(9749):1302]. Lancet. 2010;376(9742):687‐697. doi:10.1016/S0140-6736(10)61121-X
6 European Medicines Agency Summary of Product Characteristics (SmPC). Herzuma. Available at Last accessed May 2020


Zuzanna Grzeskiewicz
+44 (0)7506 339043

Sophia Eminson
+44 (0)7751 116252


Zuzanna Grzeskiewicz
+44 (0)7506 339043

Sophia Eminson
+44 (0)7751 116252