FDA approves Ziihera combos for HER2-positive cancer

The U.S. Food and Drug Administration has granted approval for two distinct treatment regimens that incorporate Ziihera, a bispecific antibody targeting HER2, for adults with advanced gastroesophageal adenocarcinoma that cannot be removed surgically and has spread beyond its original site. This approval expands therapeutic choices for patients whose tumors exhibit high levels of the HER2 protein, a driver that promotes aggressive growth in a subset of stomach and esophageal cancers.

Both newly approved combinations are intended for use as the first therapeutic approach after diagnosis of advanced disease. One regimen pairs Ziihera with the immune‑checkpoint inhibitor Tevimbra and standard chemotherapy, while the other pairs Ziihera directly with chemotherapy for patients whose tumors show particularly strong HER2 expression. Importantly, the regimen that includes Tevimbra is authorized regardless of the tumor’s PD‑L1 status, meaning that patients do not need to be selected based on that additional biomarker.

The clinical evidence supporting the approvals comes from a large, late‑stage study that compared the Ziihera‑based regimens with the long‑standing standard of trastuzumab plus chemotherapy. Researchers evaluated how long patients lived without disease worsening and overall survival, observing clear advantages for the Ziihera combinations across diverse patient subgroups. Benefit was evident whether patients had varying levels of PD‑L1 or different patterns of disease spread, showing the broad applicability of the new options.

Ziihera belongs to a class of therapies known as bispecific antibodies. Unlike conventional antibodies that bind a single target, Ziihera simultaneously engages two distinct sites on the HER2 protein. This dual binding not only reduces the amount of HER2 displayed on the cancer cell surface but also flags the cells for immune‑mediated attack. By diminishing HER2 signaling and recruiting immune mechanisms, Ziihera offers a two‑pronged assault that differs from the way trastuzumab operates.

Tevimbra, the companion immunotherapy in one of the approved combinations, blocks the interaction between PD‑1 on immune cells and its ligands on tumor cells. This interruption lifts a key brake on the immune system, allowing it to recognize and destroy cancer cells more effectively. The cooperation between Ziihera’s HER2‑directed activity and Tevimbra’s checkpoint inhibition creates a complementary strategy that can overcome resistance mechanisms that limit the efficacy of single‑agent approaches.

Safety considerations were a central focus of the trial. The most frequently reported adverse event with the Ziihera‑based regimens was diarrhea, a side effect that can range from mild to severe. Clinical investigators emphasized the importance of early detection and proactive management, including hydration, antidiarrheal medications, and dose adjustments when necessary. In addition to gastrointestinal effects, patients may experience nausea, reduced appetite, vomiting, electrolyte disturbances, fatigue, skin rash, peripheral neuropathy, and reactions related to infusion. Because the drug carries a warning about potential harm to a developing fetus, effective contraception and counseling are essential for patients of reproductive potential.

The introduction of Ziihera‑based therapies marks a shift from the previous reliance on trastuzumab as the primary HER2‑targeted option. While trastuzumab remains an important tool, the new combinations provide alternative mechanisms of action that may be more effective for certain tumor profiles, especially those with robust HER2 expression. Clinicians now have the flexibility to tailor first‑line treatment based on HER2 intensity, patient health status, and preferences regarding immunotherapy.

Patients diagnosed with advanced gastroesophageal adenocarcinoma are encouraged to discuss HER2 testing with their oncology team, as the presence and level of HER2 expression directly influence eligibility for these novel regimens. Understanding the full range of therapeutic possibilities, including the potential benefits and risks of Ziihera‑containing treatments, enables shared decision‑making and personalized care planning.

For ongoing updates on cancer research, treatment advances, and educational resources, don't forget to subscribe to CURE®'s newsletters here.

The prescribing information for Ziihera includes boxed warnings for severe diarrhea and potential harm to an unborn baby.