Trastuzumab deruxtecan has been recommended for EU approval as monotherapy for patients with HER2-positive advanced gastric cancer
Trastuzumab deruxtecan (brand name Enhertu) been recommended for approval in the European Union (EU) as monotherapy for the treatment of adult patients with advanced HER2-positive gastric or gastro-oesophageal junction adenocarcinoma who have received a prior trastuzumab-based regimen according to a press release from the manufacturer, AstraZeneca.
Gastric cancer is the 5th most common cancer worldwide and there were more than 1 million new cases in 2020 and 719,523 deaths. If a gastric cancer is diagnosed and treated when localised, the 5-year survival rate is 70%. However, if the cancer has spread to surrounding areas and/or the regional lymph nodes, the 5-year survival rate is 32% and this rate reduces to 6% if the cancer undergoes metastases. Given this poor prognosis it is important to have gastric biomarkers one of which is the Human epidermal growth factor receptor 2 (HER2) protein. While over expression is increasingly recognised as a molecular abnormality in breast cancer, there is mounting evidence of the role of HER2 over expression in patients with gastric cancer, and it has been correlated to poor outcomes and a more aggressive disease. The frequency of HER2 over expression in gastric and gastro oesophageal cancer ranges from 4.4% to 53.4%, with a mean of 17.9%. Trastuzumab is a recombinant humanised monoclonal antibody that targets the HER2 protein. In fact, trastuzumab in combination with chemotherapy is a treatment option for patients with HER2-positive advanced gastric cancer. Data obtained from two clinical trials, suggests treatment with trastuzumab deruxtecan, improves both the response and overall survival in patients with metastatic gastric cancer.
Trastuzumab deruxtecan and gastric cancer outcomes
In an open label, dose-escalation and dose-expansion phase 1 trial, 44 patients with HER2-positive gastric or gastro-oesophageal junction cancer, who received Trastuzumab deruxtecan (T-Dx-T) had a manageable safety profile and showed preliminary activity in heavily pre-treated patients with HER2-positive patients. These findings prompted the authors to suggest that T-Dx-T should be further investigated for HER2-positive gastric or gastro-oesophageal junction cancer patients. In a second phase 2 trial with HER2-positive advanced gastric cancer patients, researchers compared T-Dx-T with a physician’s choice of chemotherapy. The results showed that an objective response was seen in 51% of T-Dx-T compared with 14% of those in the physician’s choice group. In addition, the median overall survival was also longer with T-Dx-T than with chemotherapy (12.5 vs. 8.4 months).
The most recent data on T-Dx-T comes from a study reported at the ESMO Congress 2022 and provided an update from a second trial, DESTINY-GASTRIC-02, a T-Dx-T monotherapy open-label, single-arm trial in HER2-positive, unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma patients. The results demonstrated after a median duration of follow up of 10.2 months, a confirmed objective response rate of 41.8% was seen in T-Dx-T patients with a median duration of response of 8.1 months a progression-free survival of 5.6 months.
These two trials provided the necessary data to enable CHMP to give a positive opinion for the drug and it follows on from FDA approval of the drug in 2021.