FDA Grants Zenocutuzumab-Zbco Approval for Adults With Rare Bile Duct Cancer

Zenocutuzumab-zbco (Bizengri; Partner Therapeutics, Inc) received FDA approval for the treatment of patients with NRG1 fusion–positive cholangiocarcinoma, supported by data from the phase 1/2 eNRGy trial (NCT02912949). The decision marks the seventh FDA approval under the National Priority Voucher Pilot Program.¹

“Patients with this ultrarare type of cancer desperately need new treatment options,” said FDA Commissioner Marty Makary, MD, MPH, in an official release. “Through the national priority voucher pilot program, the FDA is accelerating therapies for rare diseases with unmet medical needs, reviewing applications in significantly shortened timelines.”¹

Cholangiocarcinoma is a rare, aggressive cancer of the bile ducts—slender tubes responsible for carrying digestive fluids—that affects an estimated 2000 to 3000 individuals each year in the United States. Approximately 1% of all diagnoses are NRG1 positive, meaning the tumors harbor NRG1 fusion proteins. These proteins activate cancer-promoting cellular processes, contributing to disease progression.^2,3

Zenocutuzumab-zbco is a bispecific antibody that targets and binds to HER2 and HER3 on the surface of malignant cells and tumor cells to prevent NRG1 from binding to HER3.⁴ In 2024, it was approved for adults with unresectable or metastatic non–small cell lung cancer harboring an NRG1 gene fusion with disease progression on or after prior systemic therapy or advanced, unresectable, or metastatic pancreatic ductal adenocarcinoma harboring an NRG1 gene fusion with disease progression on or after prior systemic therapy.⁵

The open-label, multicenter, multinational, dose-escalation, single-agent eNRGy trial assessed the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and antitumor activity of zenocutuzumab in patients with solid tumors harboring an NRG1 fusion. Twenty-two patients (median age, 57) were included in the cholangiocarcinoma cohort, and 19 were evaluable for efficacy measures. Of the patients, 91% had received prior systemic therapy.

The primary end points included confirmed overall response rate (ORR) and duration of response (DOR) as determined by blinded independent central review according to RECIST 1.1 criteria.

The data showed that patients with cholangiocarcinoma treated with zenocutuzumab-zbco achieved an ORR of 36.8% (95% CI, 16.3-61.6) and a DOR ranging from 2.8 to 12.9 months.

The label for zenocutuzumab-zbco carries warnings for infusion-related reactions, hypersensitivity and anaphylactic reactions, interstitial lung disease or pneumonitis, left ventricular dysfunction, and embryo-fetal toxicity. The most common adverse reactions include diarrhea, musculoskeletal pain, fatigue, nausea, infusion-related reactions, dyspnea, rash, constipation, vomiting, abdominal pain, and edema.

Zenocutuzumab-zbco is administered as a 750-mg intravenous infusion every 2 weeks, continuing until disease progression or unacceptable toxicity.

REFERENCES

1. FDA grants seventh approval under the National Priority Voucher Pilot Program. News release. FDA. May 8, 2026. Accessed May 8, 2026. https://www.fda.gov/news-events/press-announcements/fda-grants-seventh-approval-under-national-priority-voucher-pilot-program?utm_medium=email&utm_source=govdelivery

2. Cholangiocarcinoma (bile duct cancer). Mayo Clinic. July 29, 2025. Accessed May 8, 2026. https://www.mayoclinic.org/diseases-conditions/cholangiocarcinoma/symptoms-causes/syc-20352408

3. Zenocutuzumab shows clinical benefit in rare bile duct cancer. News release. AACR. October 22, 2025. Accessed May 8, 2026. https://www.aacr.org/about-the-aacr/newsroom/news-releases/zenocutuzumab-shows-clinical-benefit-in-rare-bile-duct-cancer/

4. Merus announces FDA approval of bizengri (zenocutuzumab-zbco) for nrg1+ pancreatic adenocarcinoma and nrg1+ non–small cell lung cancer (NSCLC) based on safety and efficacy data from the eNRGy study. News release. Merus. December 4, 2024. Accessed May 8, 2026. https://ir.merus.nl/news-releases/news-release-details/merus-announces-fda-approval-bizengrir-zenocutuzumab-zbco-nrg1

5. FDA grants accelerated approval to zenocutuzumab-zbco for non-small cell lung cancer and pancreatic adenocarcinoma. FDA. December 4, 2024. Accessed May 8, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-zenocutuzumab-zbco-non-small-cell-lung-cancer-and-pancreatic

6. FDA approves zenocutuzumab-zbco for advanced, unresectable or metastatic cholangiocarcinoma. FDA. May 8, 2026. Accessed May 8, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-zenocutuzumab-zbco-advanced-unresectable-or-metastatic-cholangiocarcinoma