Zanidatamab’s Dual-Targeting Design Offers Alternative To Trastuzumab Deruxtecan
Zanidatamab provides a new option for patients with HER2-positive cancers, offering a different approach from existing therapies like trastuzumab deruxtecan. As a humanized monoclonal antibody, it targets two distinct parts of the HER2 receptor, which may improve how it stops cancer growth.
Mechanism of Action and Dual-Targeting Design
Zanidatamab is an IgG-like bispecific antibody that binds to two non-overlapping domains of the HER2 protein. This dual-targeting design allows it to block HER2 signaling more completely than some single-target antibodies. It is manufactured in Chinese hamster ovary cells and is designed to recruit immune cells to destroy cancer cells while preventing HER2 from sending growth signals.
Comparison to Trastuzumab Deruxtecan
Unlike trastuzumab deruxtecan, which is an antibody-drug conjugate that delivers chemotherapy directly to HER2-positive cells, zanidatamab does not carry a cytotoxic payload. Instead, it works through dual HER2 blockade and immune-mediated mechanisms. This difference may affect how patients respond and what side effects they experience, offering an alternative mechanism of action for those who may not tolerate or respond to antibody-drug conjugates.
Clinical Data and Efficacy
Zanidatamab’s efficacy was studied in the HERIZON-BTC-01 trial, an open-label, single-arm study involving 62 participants with unresectable or metastatic HER2-positive biliary tract cancer who had received at least one prior gemcitabine-containing regimen. The trial supported its accelerated approval in the United States on November 21, 2024, and full approval for gastroesophageal cancer on August 25, 2026. The U.S. Food and Drug Administration has designated zanidatamab as a first-in-class medication, noting its novel mechanism compared to existing HER2-targeted therapies.
Side Effects and Management
The most common adverse reactions to zanidatamab include diarrhea, infusion-related reactions, abdominal pain, and fatigue. Diarrhea was frequently observed in clinical trials, often occurring within the first week of treatment. According to oncology specialists, proactive management with mandatory loperamide prophylaxis helps resolve diarrhea quickly, allowing many patients to reduce or stop additional antidiarrheal therapy. Care teams are advised to contact patients early in treatment to monitor and manage symptoms effectively.
Regulatory Pathway and Global Approvals
Zanidatamab received accelerated approval from the U.S. Food and Drug Administration on November 21, 2024, for previously treated, unresectable or metastatic HER2-positive biliary tract cancer, based on the HERIZON-BTC-01 trial. Full approval for gastroesophageal cancer followed on August 25, 2026. The drug was granted priority review, breakthrough therapy, and orphan drug designations during its development.
In April 2025, the Committee for Medicinal Products for Human Use of the European Medicines Agency issued a positive opinion recommending conditional marketing authorization for Ziihera in the European Union for adults with unresectable locally advanced or metastatic HER2-positive biliary tract cancer. Zanidatamab was subsequently authorized for medical use in the EU in June 2025. The application was submitted by Jazz Pharmaceuticals Ireland Limited.
Development and Trial Design
Zanidatamab’s development was informed by earlier-phase studies that evaluated its safety and pharmacokinetics in patients with advanced solid tumors. The pivotal HERIZON-BTC-01 trial, which supported its initial accelerated approval, enrolled 62 participants with HER2-positive biliary tract cancer who had progressed after at least one prior gemcitabine-containing regimen. This open-label, single-arm study assessed overall response rate as the primary endpoint, with durability of response and overall survival as key secondary outcomes. The trial’s design reflected the unmet need in a heavily pretreated population with limited therapeutic options.
Subsequent trials expanded the investigation of zanidatamab into gastroesophageal adenocarcinoma, including the HERIZON-GEA-01 study, which examined the drug in combination with chemotherapy and tislelizumab. Insights from these studies informed dosing strategies and adverse event management, particularly regarding gastrointestinal toxicities. The cumulative data from these trials contributed to the regulatory submissions that led to full approval in the United States and conditional authorization in the European Union.
Manufacturer and Development Background
Zanidatamab is developed and manufactured by Jazz Pharmaceuticals, which submitted the application for its approval in both the United States and the European Union. The drug is produced in Chinese hamster ovary cells, a standard platform for monoclonal antibody manufacturing that ensures proper folding and glycosylation of the IgG-like bispecific antibody. Jazz Pharmaceuticals Ireland Limited served as the applicant for the European Medicines Agency’s Committee for Medicinal Products for Human Use, which issued a positive opinion in April 2025 recommending conditional marketing authorization for Ziihera in the EU.
The development of zanidatamab was informed by earlier-phase clinical studies that assessed its safety, pharmacokinetics, and preliminary efficacy in patients with advanced solid tumors. These foundational studies supported the design of the pivotal HERIZON-BTC-01 trial, which enrolled 62 participants with HER2-positive biliary tract cancer who had progressed after at least one prior gemcitabine-containing regimen. Insights from these early investigations helped shape dosing strategies and adverse event monitoring protocols, particularly for gastrointestinal toxicities like diarrhea.
Zanidatamab’s regulatory journey included several key designations from the U.S. Food and Drug Administration, including priority review, breakthrough therapy, and orphan drug status, reflecting its potential to address unmet medical needs in rare and aggressive cancers. These designations facilitated an accelerated development timeline, contributing to its approval for biliary tract cancer in November 2024 and subsequent full approval for gastroesophageal adenocarcinoma in August 2026. The drug’s status as a first-in-class medication underscores its novel dual-targeting mechanism relative to existing HER2-directed therapies.
Patient Support and Monitoring Strategies
Effective management of zanidatamab therapy involves proactive patient monitoring, particularly for gastrointestinal side effects. Clinical guidance recommends that care teams initiate contact with patients within the first few days of treatment to identify early signs of diarrhea, which commonly occurs during the initial week of therapy. This early intervention allows for timely adjustments and helps prevent symptom escalation.
Prophylactic use of loperamide is advised as a standard measure to manage zanidatamab-associated diarrhea, enabling many patients to reduce or discontinue additional antidiarrheal medications. Distinguishing between zanidatamab-related diarrhea and immune-mediated colitis is critical, as the latter typically presents later and requires different management, such as holding immunotherapy and initiating corticosteroids.
When zanidatamab is combined with regimens like FOLFOX and tislelizumab, clinicians are advised to omit the fluorouracil bolus to lower diarrhea risk. These supportive strategies, informed by data from the HERIZON-GEA-01 trial and earlier-phase studies, aim to maintain treatment continuity while minimizing adverse impact on patient quality of life.
Sources
- Before you continue to Google
- Zanidatamab
- Proactive Diarrhea Management With Zanidatamab-Based Regimens | OncLive
Photo: Happi Raphael (CC BY-SA 4.0)
