Orphan Drug Designation Granted to Potential New Hypereosinophilic Syndrome Treatment

Hypereosinophilic syndrome

Hypereosinophilic syndrome (HES) refers to a group of rare conditions characterized by high levels of eosinophils which result in organ damage. These eosinophils often affect the lungs, heart, skin, central nervous system, and gastrointestinal tract but ultimately can impact any organ in the body. Treatment involves the reduction of eosinophils within the tissues and blood. This reduction works to prevent organ damage and slow progression of the disease. Some of the typical treatments are immunomodulatory therapies, cytotoxic therapies, and glucocorticoids. When HES is not treated it can be fatal. 

The FDA has just granted a new potential therapy for this condition Orphan Drug Designation (ODD). It’s called Fasenra and it was developed by AstraZeneca. ODD designation is given to drugs which could benefit the rare disease population. These diseases affect approximately 200,000 individuals in the United States alone.


Fasenra is an antibody. It works to attract killer cells to the eosinophils and ultimately depletes them via apoptosis. This drug has already been approved in the European Union, Japan, and the United States as a supplemental treatment for severe eosinophilic asthma. In addition to HES, Fasenra is also currently being examined as a potential treatment for severe nasal polyposis.

A Phase II clinical trial examining Fasenra as a therapy for HES has already been completed. This trial was conducted by NIH in collaboration with AstraZeneca. The primary endpoint of this trial was depletion of eosinophils in the blood. Fasenra met this endpoint at week 12. Additionally, by week 24 there was evidence of the clearance of eosinophils from the affected tissues.

Full results from this trial should be published later this year and a Phase III trial is in development.

You can read more about this potential treatment for HES here.

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