LEXINGTON, Mass., May 11, 2026
Partner Therapeutics, Inc. (PTx) announced that the U.S. Food and Drug Administration (FDA) has approved BIZENGRI® (zenocutuzumab-zbco) for the treatment of adults with advanced, unresectable, or metastatic NRG1 fusion-positive cholangiocarcinoma following disease progression after prior systemic therapy. The approval marks a historic milestone as the first targeted therapy specifically approved for NRG1-positive cholangiocarcinoma, a rare molecular subtype of bile duct cancer associated with limited treatment options and poor clinical outcomes. The regulatory decision was accelerated through the FDA’s Commissioner’s National Priority Voucher (CNPV) program, significantly shortening the review timeline and helping deliver the therapy to eligible patients more rapidly.
The latest approval expands BIZENGRI’s oncology indications beyond previously approved uses in NRG1 fusion-positive non-small cell lung cancer (NSCLC) and pancreatic adenocarcinoma, reinforcing the growing importance of precision medicine and biomarker-driven cancer therapies within modern oncology. Industry analysts view the approval as a major advancement for rare oncology treatment development and targeted biologic innovation.
Phase 2 eNRGy Trial Demonstrated Meaningful Clinical Benefit
The FDA approval was supported by data from the multicenter Phase 2 eNRGy clinical trial, which evaluated BIZENGRI in adults with advanced solid tumors harboring NRG1 gene fusions. In the cholangiocarcinoma cohort, 22 patients with unresectable or metastatic disease were enrolled, with 19 patients considered evaluable for efficacy analysis. Trial results demonstrated a confirmed overall response rate (ORR) of 36.8%, with duration of response ranging from 2.8 to 12.9 months.
Researchers and oncology experts highlighted the significance of these findings given the extremely limited treatment landscape for patients with NRG1-positive cholangiocarcinoma. Standard second-line treatment options such as FOLFOX chemotherapy historically produce response rates of approximately 5%, underscoring the importance of new targeted therapies capable of improving outcomes in this rare cancer population.
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BIZENGRI also demonstrated a generally manageable safety profile throughout the study. The most commonly reported adverse reactions included fatigue, diarrhea, musculoskeletal pain, abdominal pain, nausea, cough, dyspnea, and decreased appetite. Investigators noted that fewer than 1% of patients discontinued treatment due to drug-related adverse events, supporting the therapy’s tolerability profile in heavily pretreated patients.
Bispecific Antibody Targets Rare NRG1 Gene Fusions
Zenocutuzumab-zbco is a bispecific HER2/HER3 antibody specifically engineered to target cancers driven by NRG1 gene fusions, rare oncogenic alterations that activate HER2/HER3 signaling pathways responsible for tumor growth and proliferation. Unlike more commonly recognized gene fusions such as ALK, ROS1, RET, and NTRK, NRG1 fusions create oncogenic ligands that stimulate cancer signaling through HER3 activation. BIZENGRI works by blocking HER2/HER3 dimerization and preventing NRG1 fusion interactions, thereby suppressing tumor-promoting signaling activity.
Experts continue to emphasize the growing importance of comprehensive molecular testing, particularly tissue-based RNA sequencing and next-generation sequencing (NGS), to identify actionable genetic alterations such as NRG1 fusions. The approval further reinforces the expanding role of precision diagnostics and biomarker-guided oncology therapies in personalized cancer care.
Precision Oncology Continues Expanding Across Rare Cancers
Cholangiocarcinoma remains one of the most aggressive gastrointestinal cancers, with overall five-year survival rates below 15%. NRG1 gene fusions occur in fewer than 1% of cholangiocarcinoma cases but are often found in younger patients lacking alternative targeted treatment options. The approval of BIZENGRI provides a new precision medicine approach for this underserved patient population while highlighting broader progress in rare cancer drug development.
Partner Therapeutics stated that the approval reflects the company’s ongoing commitment to developing innovative biologic therapies capable of improving outcomes for patients with serious and difficult-to-treat diseases. The company also acknowledged the contributions of patients, investigators, and clinical research teams involved in the eNRGy trial program.
The FDA approval further strengthens momentum across the precision oncology sector as biotechnology companies increasingly focus on rare molecular targets, advanced biologics, and personalized therapeutic strategies aimed at improving survival and treatment outcomes across multiple tumor types.
Source: Partner Therapeutics press release
