New Agent for Biliary Tract Cancer Approved

The U.S. Food and Drug Administration (FDA) has approved zanidatamab (Ziihera, Jazz Pharmaceuticals, Inc.) as monotherapy for previously treated, unresectable or metastatic HER2-positive biliary tract cancer (BTC). This approval makes the bispecific antibody the first HER2-targeted treatment to carry the indication. 

Zanidatamab binds two separate regions on the HER2 cell surface protein, crosslinking neighboring HER2 proteins, blocking HER2 signaling, and inducing cytotoxic immune responses.

The FDA simultaneously announced that it has also approved VENTANA PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody (Ventana Medical Systems, Inc./Roche Diagnostics) as a companion diagnostic device to aid in identifying patients with BTC who may be eligible for treatment with zanidatamab.

Zanidatamab Trial Results

The approval of zanidatamab was based on the phase 2b HERIZON-BTC-01 trial— which was open-label, multicenter, and single-arm — involving 62 patients with unresectable or metastatic HER2-positive (IHC3+) BTC. In this trial, zanidatamab 20 mg/kg was administered every 2 weeks to patients who had received gemcitabine-containing chemotherapy previously but not a HER2-targeted therapy.

The objective response rate was 52%, and the median duration of response was 14.9 months, according to the statement from the FDA.

The life expectancy for advanced BTC treated in the second line with standard chemotherapy is approximately 6-9 months, according to Jazz Pharmaceuticals. 

Boxed Warning and Adverse Events

The prescribing information contains a boxed warning for embryo-fetal toxicity. The most common adverse reactions reported in at least 20% of patients who received zanidatamab were diarrhea, infusion-related reactions, abdominal pain, and fatigue.

The recommended zanidatamab dose is 20 mg/kg, administered as an intravenous infusion once every 2 weeks until progression or unacceptable toxicity. 

Jazz Pharmaceuticals’ application was granted priority review, breakthrough therapy designation, and orphan drug designation.

An ongoing phase 3 trial, HERIZON-BTC-302, is testing zanidatamab in combination with standard-of-care therapy in the first-line setting for advanced or metastatic HER2-positive BTC. The bispecific antibody is also being developed for HER2-positive advanced/metastatic gastroesophageal adenocarcinoma.

M. Alexander Otto is a physician assistant with a master’s degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape. Alex is also an MIT Knight Science Journalism fellow. Email: aotto@mdedge.com

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