FDA Grants Orphan Drug Designation to ZielBio’s ZB131 for Cholangiocarcinoma


The investigational drug is a monoclonal antibody with a high affinity and specificity for cancer-specific plectin, a cell surface protein that correlates with aggressive tumors and poor prognosis.

The FDA has granted orphan drug designation to ZielBio Inc’s ZB131 for the treatment of cholangiocarcinoma, a rare solid tumor originating from the bile duct system.1

The drug is a monoclonal antibody with a high affinity and specificity for cancer-specific plectin, which is a cell surface protein in a wide range of cancer that correlates with aggressive tumors and poor prognosis.1

“Patients suffering from cholangiocarcinoma have few promising therapeutic options,” Kimberly Kelly, PhD, CEO and founder of ZielBio, said in a statement. “Receiving this orphan drug designation is a regulatory milestone for ZielBio that validates our sustained efforts to bring new treatments to underserved patients.”1

ZB131 was developed to target cancer-specific plectin after investigators discovered that plectin presents on the surface of cancer cells, functioning as a driver of tumor growth and metastasis. This differs from healthy cells, where plectin is in the cytoplasm.1

In preclinical studies, ZB131 showed high specific binding to cancer-specific plectin, as well as strong anti-cancer activity. Investigators are investigating the efficacy, safety, and tolerability of the drug in individuals with solid tumors, including cholangiocarcinoma, ovarian, and pancreatic cancer, in a phase 1/2 trial (NCT05074472).1

The phase 1/2 trial is a dose escalation, first-in-human, open label, multicenter study that it is expanded at the RP2D. Investigators will enroll approximately 12 to 24 individuals in the dose escalation stage and meet the eligibility criteria during screening.2

ZB131 will be given intravenously every week, and participants will be treated until disease progression or unacceptable toxicities occur. The total number of individuals will depend on the dose level of RP2D decided.2

The FDA grants orphan drug designation to biological products or investigational drugs showing promise in treating rare conditions or diseases that affect fewer than 200,000 individuals in the United States.1


1. ZielBio receives orphan drug designation for ZB131 for the treatment of cholangiocarcinoma. PR Newswire. News release. November 15, 2022. Accessed November 29, 2022. https://www.prnewswire.com/news-releases/zielbio-receives-orphan-drug-designation-for-zb131-for-the-treatment-of-cholangiocarcinoma-301678075.html

2. Ramanathan, R. A phase 1/2 first-in-human open label dose escalation study of a CSP targeting functional antibody in solid tumors. ClinicalTrials.gov. Updated August 31, 2022. Accessed November 29, 2022. https://beta.clinicaltrials.gov/study/NCT05074472

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