The bispecific HER2-targeted antibody zanidatamab was found to safely induce durable antitumor activity in an expansion cohort of patients with HER2-overexpressing biliary tract cancer (BTC). Data from the phase 1 study’s (ClinicalTrials.gov identifier: NCT02892123) expansion cohort were presented at the 2021 Gastrointestinal Cancers Symposium by Funda Meric Bernstam, MD, chair of the department of investigational cancer therapeutics at The University of Texas MD Anderson Cancer Center in Houston.

Twenty of the 21 patients included in the cohort were available for response, and tumor shrinkage was observed in most of them. The confirmed objective response rate was 40% (95% CI, 19.1-63.9), with 8 patients achieving a partial response. The disease control rate was 65%, and the median duration of response was 7.4 months.

In the dose-escalation part of the phase 1 study, the investigators identified 20 mg/kg of zanidatamab administered every 2 weeks as the recommended dose. This dose was used in the expansion cohort of 21 patients. Tumors were assessed every 8 weeks.


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The median patient age was 63 years, and 67% of patients were female. Gallbladder cancer was the most common diagnosis (57%), followed by intrahepatic cholangiocarcinoma (24%) and extrahepatic cholangiocarcinoma (19%). Twenty-four percent of patients received prior HER2-targeted therapy.

Regarding safety, zanidatamab was found to be well-tolerated. No patient experienced a grade 3 or higher drug-related adverse event (AE). One zanidatamab-related serious AE, grade 2 fatigue, was observed in 1 of the trial participants. Two deaths were reported during the study; 1 was due to progressive disease and the other, to an AE not related to zanidatamab therapy.

All patients experienced treatment-emergent adverse events, the most common of which were diarrhea (43%) and infusion-related reactions (33%).

“Based on these results, zanidatamab has the potential to address unmet need in patients with HER2-positive biliary tract cancer,” Meric-Bernstam concluded.

A registration-enabling global phase 2 study in HER2-amplified BTC (ClinicalTrials.gov identifier: NCT04466891) is now open for enrollment.

Disclosures: Some of the study authors disclosed financial relationships with the pharmaceutical industry and/or the medical device industry. For a full list of disclosures, please refer to the original study. This clinical trial was supported by Zymeworks.

Reference

Meric-Bernstam F, Hanna DL, El-Khoueiry AB, et al. Zanidatamab (ZW25) in HER2-positive biliary tract cancers (BTCs): results from a phase 1 study. Presented at 2021 Gastrointestinal Cancers Symposium; January 15-17, 2021. Abstract 299.

This article originally appeared on Cancer Therapy Advisor