The U.S. Food and Drug Administration has approved Bizengri (zenocutuzumab-zbco), the first targeted therapy for adults suffering from an ultra-rare and aggressive form of bile duct cancer known as NRG1 fusion-positive cholangiocarcinoma.

The approval marks a significant breakthrough for patients with advanced, inoperable or metastatic cholangiocarcinoma, a disease that has long faced limited and largely ineffective treatment options after initial therapy.

According to the FDA, Bizengri is specifically designed for patients whose cancer carries an NRG1 gene fusion — a rare genetic alteration that causes abnormal cell growth and fuels cancer development.

NRG1, or neuregulin 1, gene fusion occurs when segments of DNA abnormally join together, triggering uncontrolled tumour growth. While rare, the mutation has increasingly become an important target in precision cancer therapy.

The latest approval expands the growing role of Bizengri in cancer treatment. In 2024, the FDA had already approved the drug for adults with advanced or metastatic non-small cell lung cancer and pancreatic cancer linked to the same genetic mutation.

Medical experts say cholangiocarcinoma, or bile duct cancer, remains one of the most difficult cancers to treat, particularly in advanced stages where surgery is no longer an option.

The FDA noted that the approval was granted under the Commissioner’s National Priority Voucher (CNPV) pilot programme, an initiative aimed at accelerating review timelines for therapies targeting rare diseases and unmet medical needs.

Calling the approval an important step for rare cancer treatment, FDA Commissioner Dr. Marty Makary said patients with this aggressive cancer urgently need new treatment options.

“Patients with this ultra-rare type of cancer desperately need new treatment options,” Makary said in a statement.

“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,” he added.

The approval was based on clinical trial data involving 19 adults with NRG1 fusion-positive cholangiocarcinoma. Researchers found that nearly 37 per cent of patients responded to the treatment, with response durations ranging from around three months to over a year.

While the results offer fresh hope for patients, the FDA also cautioned about potential risks linked to the therapy.

Serious side effects associated with Bizengri include infusion-related reactions, interstitial lung disease or pneumonitis, and left ventricular dysfunction — a condition that affects the heart’s ability to pump blood effectively.

More commonly reported side effects included fatigue, swelling, digestive problems and body aches.

The approval reflects the broader shift toward precision oncology, where treatments are increasingly tailored to specific genetic mutations rather than cancer type alone.

Healthcare experts believe the decision could pave the way for more targeted therapies for rare cancers, especially for patients who previously had very limited treatment choices.