Enhertu, AstraZeneca’s Drug against Gastric Cancer Gets Breakthrough Therapy Designation
By T. Chakraborty, Ph.D.
Gastric cancer is difficult to treat and is the third most common cause of cancer mortality. With a 32% five-year survival rate, it is estimated to account for 11,000 deaths in the United States in 2020. The survival rate further decreases to 5% for metastatic patients creating a need for treatment for this aggressive form of cancer. The major types of treatment include surgery, chemotherapy, radiation therapy, and targeted therapy. One among five patients with this illness consists of Human epidermal growth factor receptor 2 (HER2) positive cancer cells making it a lucrative drug target [1,2].
In 2010, Roche’s Trastuzumab, a monoclonal antibody against HER2, became the first biologic therapy to be approved by the FDA for advanced gastric cancer. Its combination with chemotherapy prolonged overall survival in patients, the primary endpoint of the ToGA trial . However, there are no treatments available for patients whose disease progresses after the recommended first-line therapy with this combination.
FDA Approval of Enhertu
On the 11th of May, AstraZeneca and Daiichi Sankyo announced that Enhertu (trastuzumab deruxtecan) has been granted the FDA’s breakthrough therapy designation for the treatment of HER2 positive metastatic gastric cancer patients. If approved, it would be the first HER2 directed antibody drug conjugate (ADC) for this condition. Earlier, the drug achieved this status and also went on to receive FDA approval for breast cancer.
Gilles Gallant, the head of Oncology Research and Development at Daiichi Sankyo, said, “DESTINY-Gastric01 represents the first randomized trial of Enhertu to demonstrate clinically meaningful and statistically significant results, including objective response and survival increases compared to physician’s choice of chemotherapy. We are thrilled that the FDA has granted Enhertu a second Breakthrough Therapy Designation.”
José Baselga, Executive VP of AstraZeneca, added, “Current therapy options are limited for patients with HER2-positive metastatic gastric cancer and for those who relapse, there are no approved HER2-targeted medicines. We look forward to working with the FDA to further explore the potential of Enhertu to become an important new treatment and the first antibody drug conjugate for this devastating disease.” In early 2019 AstraZeneca and Daiichi Sankyo started a global collaboration to develop and globally commercialize Enhertu .
DESTINY-Gastric01 is a Phase 2, open-label, multicenter trial that evaluated the safety and efficacy of Enhertu in 188 HER2 positive, advanced gastric cancer or gastroesophageal junction adenocarcinoma patients from Japan and South Korea. The patients were randomized 2:1 to receive 6.4 mg/kg dose of Enhertu once every three weeks or investigator’s choice of chemotherapy (paclitaxel or irinotecan monotherapy). The cohort consisted of patients who have already progressed on two or more prior treatments, including fluoropyrimidine and platinum chemotherapy and trastuzumab.
Patients who received Enhertu showed a statistical and clinical improvement in overall survival and objective response rate as compared to chemotherapy. The overall safety profile of this drug was consistent with earlier observations, and the most common side effects were hematologic and gastrointestinal issues. When the results were released last January, José Baselga said they believed Enhertu “has the potential to redefine the treatment of patients with HER2-expressing cancers” .
Six more registrational trials are underway to evaluate the efficacy and safety profile of Enhertu across various HER2 positive cancer like breast, gastric, and lung cancer. Trials are also underway in combination with other therapies like immunotherapy and chemotherapy .
Editor: Rajaneesh K. Gopinath, Ph.D.
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