The US Food and Drug Administration (FDA) has lifted a clinical hold that had been placed on the injectable hepcidin mimetic agent rusfertide (PTG-300), it was announced on October 11, 2021, in a press release provided by Protagonist Therapeutics, Inc.

With this announcement, ongoing clinical trials involving rusfertide are allowed to resume dosing. A phase 3 registrational trial of the agent is also scheduled to begin in the first quarter of 2022.

“We are extremely pleased that the FDA has acted so quickly in lifting the clinical hold on the rusfertide development program, allowing us to resume patient dosing in our clinical studies,” said Dinesh Patel, PhD, President and Chief Executive Officer of Protagonist in the press release announcing the FDA’s decision. “Patient safety continues to be our topmost priority. We believe that the cumulative evidence regarding the safety and clinical risk-benefit of rusfertide is supportive of expedited clinical development,” Dr Patel continued.

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The full clinical hold had been applied on September 17, 2021, to all the company’s rusfertide clinical trials because of a nonclinical result involving a 26-week rasH2 transgenic mouse model that had developed both benign and malignant subcutaneous mouse tumors. This finding also led to reconsideration of 4 cases of cancer seen from a total population of 160 patients in clinical trials involving rusfertide. Comprehensive review of details in the safety database, such as regarding suspected unexpected serious adverse reactions, was also undertaken. However, no further cases of cancer or unexpected safety signals were identified through this review.

Protagonist Therapeutics, Inc., said in their press release that they have complied with requests for information by the FDA, such as updating investigator brochure and patient consent forms. The company indicated they will also work closely with study investigators and clinical trial sites.

“We are actively preparing to initiate the phase 3 registrational study for polycythemia vera in the first quarter of 2022,” Dr Patel said in the press release. “Protagonist will continue to work closely with the FDA to ensure patient safety with amendments to current and planned future studies with rusfertide. We remain optimistic about the future potential of rusfertide to address unmet medical needs in excessive erythrocytosis and iron overload related diseases like polycythemia vera and hereditary hemochromatosis, respectively.”


Protagonist Therapeutics announces removal of FDA clinical hold on the rusfertide clinical development program. Newark, CA: PRNewswire; October 11, 2021.