Investigational Treatment for Hypereosinophilic Syndrome Granted Orphan Drug Status

The Food and Drug Administration (FDA) has granted Orphan Drug designation to dexpramipexole (Knopp Biosciences), an investigational treatment for hypereosinophilic syndrome (HES).

HES is characterized by peripheral eosinophilia with evidence of organ involvement. Treatment depends on the severity of the condition and underlying cause; while steroid therapy is effective in most patients, high doses are often needed

Dexpramipexole is an orally bioavailable synthetic aminobenzothiazole, being developed as a targeted therapy for eosinophilic inflammatory disorders. A proof-of-concept study involving 10 patients with HES on steroid monotherapy showed that dexpramipexole could potentially be an effective steroid-sparing drug as 4 of the 10 evaluable patients were able to reach a ≥50% reduction in their minimally effective corticosteroid dose. In addition, three of these patients had complete symptom resolution with an absolute eosinophil count of  0/uL within 3 months of starting dexpramipexole, and remained in remission for a median duration of 29 on dexpramipexole monotherapy.

Related Articles

“We are very pleased to receive Orphan Drug designation for dexpramipexole for HES,” said Michael Bozik, MD, CEO of Knopp Biosciences. “There is an urgent need for effective treatments for patients suffering from this under-recognized, debilitating disease, especially for oral medications that selectively deplete eosinophils, and this designation represents an important regulatory milestone as we advance our dexpramipexole program toward late-stage clinical development.”

For more information visit