Protagonist Therapeutics has received a verbal communication from the US Food and Drug Administration (FDA) that its clinical studies for rusfertide, an investigational product candidate presently in development, have been put on a clinical hold.

This communication on the development programme of rusfertide (PTG-300) comes after the firm’s notification to the regulatory authority of a recent non-clinical finding in a 26-week rasH2 transgenic mouse model study.

The rasH2 model is intended to discover signals associated with tumorigenicity.

This study observed benign and malignant subcutaneous skin tumours.

The firm stated that it is working with the FDA and will be ready to make all required updates to clinical study documents.

In consultation with the regulatory agency, the firm stated that it will also determine the next steps.

It plans to provide further clinical safety reports, update the investigator brochures and patient informed consent forms, besides making required changes to study protocols.

Under the ongoing clinical trials with rusfertide, dosing of patients will be put on hold.

The study investigators have been asked to facilitate patient notification.

Protagonist president and CEO Dinesh Patel said: “Patient safety is our absolute top priority. We are fully committed to working closely with the FDA in understanding and evaluating potential clinical risks and determining next steps for the development of rusfertide.”

The California-based biopharmaceutical company’s pipeline includes rusfertide, which is an injectable hepcidin mimetic in a Phase II proof-of-concept clinical trial for polycythemia vera (PV), a Phase II study in PV subjects with high hematocrit levels, and a Phase II study for hereditary hemochromatosis.