Orphan Drug Designation Given to New Potential Oral Therapy for Hypereosinophilic Syndrome

Hypereosinophilic Syndrome

Hypereosinophilic syndrome (HES) is a rare disease which causes high levels of white blood cells in the body. These cells are called eosinophils, and they’re essential for proper immune system function. A diagnosis of HES is only given if eosinophil levels are elevated for 6 months or more and all other probable causes for the elevation are ruled out. The cause of this condition is still unknown. 

High levels of eosinophils can eventually result in organ damage, however which organs the condition affects varies among patients. Symptoms of the condition are dependent on which areas of the body are affected. Some of the more common areas of impact are the lungs, heart, nervous system, bone marrow, and skin.

Symptoms of HES range in severity but can include skin rashes, lung disease, fatigue, nerve damage, memory loss, heart disease, and brain damage.

HES is generally more prevalent in males than females. It is typically diagnosed when the individual is between 20 and 50 years of age and affects approximately one person out of every million.

Treatment of the condition focuses on lowering eosinophil levels. Depending on how the disease presents in the patient, their treatment plan will vary. Treatment may include steroids, interferon alpha, gleevec, or chemotherapy.

But, a new potential oral treatment for HES has just received Orphan Drug Designation from the FDA. It’s called dexpramipexole.


Dexpramipexole is being developed by Knopp Biosciences. It is an oral medication which works to selectively deplete eosinophils. Clinical trials thus far have shown extreme promise for this therapy, reducing eosinophil levels in both the blood and the tissues persistently.

Phase 2 clinical trial results have been published in Blood. 

This new designation will provide Knopp a variety of incentives which should help accelerate the development of this potential therapy. Knopp recognizes the urgent need for this patient population as HES is under-recognized. There is a true need for more treatment options, and this new designation confirms the potential of this promising therapy.

You can read more about Knopp’s research of dexpramipexole here.

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