In an environment where gastric cancer treatments are currently lacking, the approval of Enhertu (ingredient: trastuzumab deruxtecan) as a tertiary treatment for HER2-positive gastric cancer represents a major milestone for gastric cancer patients, said an expert.
Daiichi Sankyo Korea and AstraZeneca Korea held a joint press conference at the Plaza Hotel on Thursday to celebrate the domestic launch of Enhertu, the first and only HER2 target ADC, which improves treatment for advanced and metastatic gastric cancer.
Enhertu was domestically approved in September last year as an indication for locally progressive or metastatic HER2 positive gastric or gastroesophageal junction (GEJ) adenocarcinoma, which had previously been administered two or more treatments, including anti-HER2 treatment,
Gastric cancer is one of the most common cancers in Korea and Korea’s incidence rate of gastric cancer per 100,000 people is about 10 times that of the U.S. Gastric cancer has a five-year survival rate of 97 percent if diagnosed when cancer is still localized, but the rate drops steeply to 62.1 percent after local progression and 6.4 percent when it metastasizes.
Professor Rha Sun-young who is the Chairman of Gastric Cancer of the Korean Cancer Study Group shared about the development status of therapeutic drugs for HER2-positive advanced and metastatic gastric cancer and the clinical significance of Enhertu as a HER2-targeted treatment which has not existed for 10 years.
Professor Rha elaborated, "Studies have been conducted on various targeted treatments in gastric cancer, but it has not been easy due to gastric cancer's complex pathogenesis, heterogeneity in tumors, and heterogeneity among patients. Since trastuzumab was approved as the primary treatment in metastatic gastric cancer in 2010, studies of other HER2 target drugs have not proven clinical significance in gastric cancer."
She supported these claims with data from the DESTINY-Gastric01 clinical trials and noted that unlike the data presented in January for the breast cancer indication, the results for gastric cancer did not vary much across geographical regions.
The objective response rate (ORR) of the Enhertu group was 51 percent, which showed significant improvement over irinotecan or paclitaxel. In addition, the median overall survival period (mOS) for the Enhertu group was 12.5 months which reduced the risk of death by 41 percent compared to 8.4 months in the control group.
"Enhertu is the only HER2-targeted therapy to demonstrate overall survival of more than one year in advanced gastric cancer after trastuzumab treatment,” Professor Rha remarked. “Based on the Bystander effect, the clinical trial was able to meet the unmet needs of patients with metastatic and advanced HER2-positive gastric cancer.”
Commenting on the insurance coverage for this drug, an official from Daiichi Sankyo Korea said, "In December last year, we completed the application for insurance reimbursement for breast cancer and gastric cancer together and are currently awaiting a response from the Health Insurance Review Assessment (HIRA)."
“Even if a new drug is approved, reimbursement is essential to ensure patients can access this treatment,” Professor Rha remarked. Given that the number of HER2 positive gastric cancer patients receiving tertiary or higher treatment is small enough for it to be considered rare cancer, I hope that insurance benefits can first be granted for the gastric cancer indication ahead of breast cancer."
