Oncologists Welcome New Tailored Treatments for HER2-Positive Gastric Cancer
Physicians who treat gastric cancer are heralding a new drug approval for gastric cancer patients with HER2-positive tumors, with many cheering the addition of two powerful combination treatments for newly diagnosed patients.
On August 25, the U.S. Food and Drug Administration approved the bispecific antibody Ziihera (zanidatamab) for use in two different combination treatments for the first-line treatment of advanced HER2-positive gastric cancer that cannot be removed with surgery. One combines the Ziihera with chemotherapy and the second adds those two drugs to the immunotherapy drug Tevimbra (tislelizumab).
HER2 is a protein on cancer cells that drives tumor growth. Ziihera, which is being developed by Gastric Cancer Foundation sponsors Jazz Pharmaceuticals and BeOne Medicines, is a bispecific antibody that works by inhibiting HER2 from two separate angles. Tevimbra frees up the immune system to further attack the cancer by inhibiting the protein PD-1. The combination of Ziihera, Tevimbra and chemotherapy was approved for all HER2-positive patients regardless of whether or not their tumors express high levels of PD-1.
The approvals were based on results from a pivotal trial, which demonstrated that both drug combinations reduced the risk of tumor progression or death by 35% in HER2-positive gastric cancer patients. Significantly, the combination of Ziihera, Tevimbra and chemotherapy extended median overall survival by seven months when compared to Herceptin (trastuzumab) plus chemotherapy. The median overall survival of 26.4 months among patients on the newly approved drug regimen was the longest ever reported in a phase 3 trial in HER2-positive gastric cancer patients.
“These are obviously nice numbers to see and clinically meaningful to patients, and so we were all happy when we saw this data presented,” said Samuel Klempner, MD, of Massachusetts General Hospital and Harvard Medical School, who is a former Gastric Cancer Foundation grantee, during an educational webinar on September 14.
During the webinar, which was sponsored by GI Cancer Alliance, Klempner also emphasized the importance of biomarker testing in diagnosing gastric cancer—and in helping oncologists tailor treatments to the molecular characteristics of individual patients’ diseases. An estimated 20% of gastric cancer patients have HER2-driven disease. HER2 is one of four main biomarkers currently guiding treatment strategies in gastric cancer.
