Regulatory update: mepolizumab for the treatment of hypereosinophilic syndrome (HES)

GSK today announced that it has notified the European Medicines Agency of its decision to withdraw the Marketing Authorisation Application (MAA) in the EU for mepolizumab for the treatment of hypereosinophilic syndrome (HES).

Issued: Wednesday 29 July 2009, London, UK

GSK today announced that it has notified the European Medicines Agency of its decision to withdraw the Marketing Authorisation Application (MAA) in the EU for mepolizumab for the treatment of hypereosinophilic syndrome (HES).

GSK took the decision to withdraw the submission for mepolizumab based on feedback from the Committee for Medicinal Products for Human Use (CHMP) that additional data would be required to further demonstrate clinical benefit and support the application for approval.  GSK continues to believe that the evidence supports mepolizumab as a treatment option for patients with HES but accepts the CHMP’s recommendation that the medicine cannot be approved at this time without further data. 

David Gordon, VP, Biopharm R&D, GSK said: “Research and development in HES is tremendously challenging.  It is a disease with very limited treatment options and this decision has been extremely difficult to take.  Nevertheless, we are committed to exploring new options to develop mepolizumab as a treatment for HES and we will continue to make it available to patients who are currently benefiting from mepolizumab through our compassionate use programme.”

The intended use of mepolizumab was for the treatment of FIP1* negative HES, to reduce or eliminate the need for corticosteroid therapy and to reduce eosinophil (a type of white blood cell) count.  There is a significant need among HES patients for new treatment options as there are no currently approved therapies in the EU for FIP1 negative HES. 

Developing a new treatment for such a rare orphan disease as HES and establishing a favourable benefit to risk profile is a significant challenge: small numbers of patients make recruitment for clinical trials difficult and there are no recognised clinical endpoints for HES as this disease affects patients in many different ways and in many different body organs. 

In recognition of the severity of the disease and currently limited treatment options GSK will continue, where permitted, to support access to mepolizumab for patients with life-threatening HES through its ongoing compassionate use programme.  Patients will receive the medicine for as long as they and their treating physicians believe they are benefiting from continued treatment.

GSK will explore future options for development of mepolizumab as a treatment of HES and withdrawal of the EU application does not preclude GSK from making a new application at a later stage.  Development programmes for the other potential indications will continue as planned, including for use to treat severe asthma.

* HES patients without the FIP1L1-PDGFRA fusion gene.

Notes to Editors

About HES

Hypereosinophilic syndrome (HES) is a group of disorders characterised by persistent and marked build-up in the blood and organs of a type of white blood cell, known as an eosinophil, in the absence of a recognised cause.  Depending on which organs are affected, the overabundance of eosinophils can lead to complications ranging from fever and malaise to blood abnormalities, respiratory and cardiac problems, or death in some patients with advanced disease.

About mepolizumab

Mepolizumab is an investigational, humanised monoclonal antibody that binds to and inactivates a protein cell messenger called interleukin-5, which is the main controller of eosinophils in the blood.  The antibody treatment reduces the accumulation of eosinophils in the blood.1,2  Mepolizumab has been granted orphan drug status for the HES indication by regulatory authorities in the US and the European Union.  

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Cautionary statement regarding forward-looking statements
Under the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995, GSK cautions investors that any forward-looking statements or projections made by GSK, including those made in this announcement, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Factors that may affect GSK' s operations are described under 'Risk Factors' in the 'Business Review' in the company' s Annual Report on Form 20-F for 2008.


1.        Ames RS, Tornetta MA, McMillan et al. Neutralizing murine monoclonal antibodies to human IL-5 isolated from hybridomas and a filamentous phage Fab display library. J Immunol 1995; 6355-6564.

2.        Hart TK, Cook RM, Zia-Amirhosseini P, et al. Preclinical efficacy and safety of mepolizumab (SB-240563), a humanized monoclonal antibody to IL-5, in cynomolgus monkeys. J Allergy Clin Immunol 2001; 108:250-7.