FDA expands Bizengri to NRG1 fusion-positive cholangiocarcinoma

The FDA has approved Partner Therapeutics’ Bizengri (zenocutuzumab-zbco) for adults with advanced, unresectable, or metastatic cholangiocarcinoma harboring an NRG1 gene fusion after prior systemic therapy, giving this ultra-rare subset its first targeted therapy. FDA posted the approval on May 8, 2026, and said the application moved through the agency’s Commissioner’s National Priority Voucher pilot program, which is intended to speed review for products tied to national priorities. (fda.gov)

The move builds on Bizengri’s earlier FDA path. In December 2024, zenocutuzumab-zbco received accelerated approval for adults with NRG1 fusion-positive non-small cell lung cancer and pancreatic adenocarcinoma after prior systemic therapy. Partner Therapeutics later took over US commercialization rights, then submitted a supplemental biologics license application for cholangiocarcinoma in April 2026. Around the same time, the company said NCCN had added zenocutuzumab-zbco to its biliary tract cancer guidance as a Category 2A subsequent-line option and a Category 2B front-line recommendation for NRG1 fusion-positive cholangiocarcinoma. (fda.gov)

The new approval rests on the phase 2 eNRGy trial, a multicenter, open-label, multi-cohort study in advanced solid tumors with NRG1 fusions. FDA said 22 patients with unresectable or metastatic NRG1 fusion-positive cholangiocarcinoma were enrolled, with 19 evaluable for efficacy. Partner Therapeutics reported an overall response rate of 36.8% and a median duration of response of 12.9 months by blinded independent central review in the cholangiocarcinoma cohort. ASCO Post coverage of the 2025 AACR-NCI-EORTC presentation described activity in more than one-third of patients, with median progression-free survival of 9.2 months and a clinical benefit rate of 58%. (fda.gov)

Mechanistically, zenocutuzumab is a bispecific antibody designed to block HER2/HER3 dimerization and interfere with NRG1 fusion signaling through HER3. That matters because NRG1 fusions are rare and biologically distinct from more familiar fusion drivers such as FGFR, ALK, RET, or ROS1. Partner Therapeutics says these alterations occur in fewer than 1% of cholangiocarcinoma cases, helping explain why this is a small but high-need market. (prnewswire.com)

Expert commentary has framed the approval as validation of a molecularly defined approach in a hard-to-study population. In ASCO Post coverage from October 2025, Memorial Sloan Kettering oncologist Alison Schram said the benefit of zenocutuzumab appeared to extend beyond the drug’s then-approved lung and pancreatic indications to cholangiocarcinoma, and described NRG1-positive cholangiocarcinoma as a group with significant unmet need. Company statements struck a similar note, with Partner Therapeutics calling the approval the first targeted therapy for this subset and highlighting the shortened review timeline under the voucher program. (ascopost.com)

Why it matters: For veterinary professionals, the story isn’t about immediate use in animal patients. It’s about where oncology is heading. This approval reinforces the value of biomarker-led treatment selection, especially in rare cancers where histology alone may not be enough to guide care. It also underscores a practical point with broader relevance: identifying rare fusions may require tissue-based RNA testing, not just standard DNA panels. For veterinary oncologists and diagnostics leaders, that’s a reminder that assay design, referral pathways, and access to advanced molecular profiling increasingly shape what treatment options are even visible to clinicians and pet parents. (partnertx.com)

Safety and monitoring will also be worth following as use expands. In broader reporting on the approval, adverse events were described as mostly grade 1 or 2, with infusion-related reactions among the more common issues, while rare interstitial lung disease or pneumonitis and declines in left ventricular ejection fraction were flagged as clinically important monitoring considerations. Those details matter for oncology practices thinking about infusion capacity, monitoring protocols, and how targeted biologics fit into real-world care delivery. (targetedonc.com)

What to watch: Next steps include publication of the full updated label in Drugs@FDA, real-world uptake in community oncology, any confirmatory evidence tied to the drug’s earlier accelerated approvals, and whether developers push further toward broader NRG1-driven, tumor-agnostic positioning. (fda.gov)