Protagonist's story gets a happy ending as FDA's hold swiftly lifted on rusfertide program

A month ago, Protagonist Therapeutics' shares more than halved on an FDA clinical hold of its blood cancer drug after worrying preclinical safety signals.

Today, the biotech’s shares have jumped nearly 100% to around $35 in premarket trading Monday morning after announcing a swift reversal of the hold. In mid-September, the FDA slapped a full clinical hold after an animal study showed mice developed benign and malignant skin tumors when using the drug.

Protagonist has been testing the therapy, rusfertide, in several phase 2 trials. These include two studies in polycythemia vera (PV), a slow-growing blood cancer in which the body makes too many red blood cells, and one study in hereditary hemochromatosis, a group of rare disorders in which iron builds up in organs such as the liver, heart and pancreas.

The FDA told the Newark, California-based biotech it can now fully continue on with the program after individual patient clinical safety reports were handed over. Protagonist also “updated the investigator brochure and patient informed consent forms, performed a comprehensive review of the most recent safety database, and included new safety and stopping rules in the study protocols,” according to a statement.

“We believe that the cumulative evidence regarding the safety and clinical risk-benefit of rusfertide is supportive of expedited clinical development,” said Dinesh Patel, Ph.D., president and CEO of Protagonist.

RELATED: FDA hits pause on Protagonist's blood cancer med after mouse study turns up skin tumors 

“We are actively preparing to initiate the phase 3 registrational study for polycythemia vera in the first quarter of 2022. 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.”

Rusfertide is a synthetic form of the hormone hepcidin, which controls the production of red blood cells thanks to the role it plays in the absorption, storage and distribution of iron in the body.

Current treatments for PV include having one’s blood drawn in a process called phlebotomy to reduce the volume of red blood cells in the body.

Many patients will also receive medicines that tamp down on the formation of blood cells in the bone marrow, such as the chemo drug hydroxyurea and drugs like aspirin to lower the risk of blood clots. In 2014, the FDA approved Incyte’s JAK inhibitor Jakafi for PV patients for whom hydroxyurea does not work.