By Connor Hart

Shares of Protalix BioTherapeutics fell after the company said the European Medicines Agency rejected its request to approve a once-every-four-weeks dosing schedule for its Fabry disease treatment, Elfabrio.

The stock tumbled 30% to $1.67 in premarket trading Friday. Through Thursday's close, shares are up 28% so far this year.

The Israel-based company, which developed Elfabrio alongside Chiesi Global Rare Diseases, part of Italy-based Chiesi Group, had been seeking approval for a new, less frequent dosing regimen for Elfabrio. The treatment is currently approved at a lower dose, once every two weeks.

Protalix and Chiesi submitted data from a recent study testing the monthly dosing in patients who had already been using the drug. However, the agency's Committee for Medicinal Products for Human Use concluded that data wasn't strong enough to prove it had the same efficacy as that of the currently approved schedule, the companies said on Friday.

Elfabrio is an enzyme-replacement therapy for Fabry disease, a rare genetic disorder that causes the buildup of fatty substances in organs including the heart, kidneys and skin.

"We are disappointed by the result of this review but want to express our immense appreciation for the collaboration of the patient community, researchers and European Commission throughout this process," said Giacomo Chiesi, executive VP of Chiesi Global Rare Diseases.

Protalix Chief Executive Dror Bashan added that the companies remain committed to reducing the treatment burden for patients with Fabry disease.

Write to Connor Hart at connor.hart@wsj.com

(END) Dow Jones Newswires

October 17, 2025 09:28 ET (13:28 GMT)

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