FDA lifts hold on Protagonist lead candidate trials

Oct. 11, 2021

Protagonist Therapeutics announced that the U.S. FDA has removed the full clinical hold on studies for the company's lead investigational product candidate for blood cancer, rusfertide, less than a month after trials were halted over safety concerns.

Rusfertide (PTG-300) is an injectable hepcidin mimetic that was currently in a phase 2 study for the treatment of polycythemia vera, a rare type of blood cancer.

The hold, issued Sept 17, followed the California-based biotech's notification to the FDA of a non-clinical finding in a 26-week rasH2 transgenic mouse model study. Both benign and malignant subcutaneous skin tumors were observed in the study.

According to Protagonist, the rasH2 signal also prompted a re-examination of the four cases of cancer observed across all rusfertide clinical trials involving over 160 patients, and a comprehensive review of the safety database, including cases of suspected unexpected serious adverse reaction. No additional cancer cases, and no other unexpected safety signals, surfaced in this process.

The company said it provided the FDA with the requested individual patient clinical safety reports, 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.

Per the FDA, all dosing in all clinical studies of rusfertide may now be resumed. Protagonist's CEO, Dinesh Patel, expressed how pleased the company was in the FDA's swift action in a recent press release.