EU/3/07/462

Idiopathic thrombocytopenic purpura is a disease where the affected patients' immune system reacts against certain of their own blood cells that are involved in the blood-clotting process, the so-called platelets. Idiopathic means that the reason why this happens is unknown. As a result, however, there will be fewer platelets present in the blood (thrombocytopenia), resulting in spontaneous bleeding and bruising of the skin in purple spots (this symptom is called purpura). Idiopathic thrombocytopenic purpura can be acute or chronic (long-lasting), and can occur in both children and adults. The severity of the bruising is determined by the degree of thrombocytopenia; it can vary from just small skin spots that occur after small injuries, to spontaneous blood losses (haemorrhages) from the nose, in the gut or in the brain (intracranial haemorrhage), which can be life-threatening.

At the time of designation, idiopathic thrombocytopenic purpura affected between 1 and 4 in 10,000 people in the European Union (EU). This was equivalent to a total of between 50,000 and 200,000 people*, and is below the ceiling for orphan designation, which is 5 people in 10,000. This is based on the information provided by the sponsor and the knowledge of the Committee for Orphan Medicinal Products (COMP).

*Disclaimer: For the purpose of the designation, the number of patients affected by the condition is estimated and assessed on the basis of data from the European Union (EU 27), Norway, Iceland and Liechtenstein. At the time of designation, this represented a population of 500,300,000 (Eurostat 2007).

Treatment of idiopathic thrombocytopenic purpura depends on the form of the disease (acute or chronic) and on the age of onset. Current treatment methods include surgery, consisting of spleen removal (splenectomy), or pharmacological treatment (medicines). Splenectomy is performed in order to limit the destruction of the platelets, since the spleen is the most important organ where platelets are removed from the blood. Several types of medicines were authorised in the Community for the treatment of idiopathic thrombocytopenic purpura at the time of submission of the application for orphan-drug designation. Recombinant human soluble Fc-gamma receptor II b could be of potential significant benefit for the treatment of idiopathic thrombocytopenic purpura because of its mechanism of action. This assumption will have to be confirmed at the time of marketing authorisation. This will be necessary to maintain the orphan status.

The immune-system reaction against the platelets of affected patients is mediated through protein molecules called antibodies. Antibodies are proteins that normally target and bind specific structures in the surface of foreign bodies, such as bacteria. In idiopathic thrombocytopenic purpura, there are antibodies that bind to the platelets with one end and to cells of the immune system, the cells that destroy the platelets, with the other end. Recombinant human soluble Fc-gamma receptor II b is designed to bind to the end of the antibodies that usually binds to the immune cells, thus inhibiting (blocking) the immune reaction that destroys the platelets.

The evaluation of the effects of recombinant human soluble Fc-gamma receptor II b in experimental models was ongoing.

At the time of submission of the application for orphan designation, no clinical trials in patients with idiopathic thrombocytopenic purpura had been initiated.

Recombinant human soluble Fc-gamma receptor II b was not authorised anywhere worldwide for the treatment idiopathic thrombocytopenic purpura or designated as orphan medicinal product elsewhere for this condition, at the time of submission.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 27 June 2007 recommending the granting of this designation.

• the seriousness of the condition;
• the existence or not of alternative methods of diagnosis, prevention or treatment;
• either the rarity of the condition (considered to affect not more than five in ten thousand persons in the Community) or the insufficient return of development investments.

Designated orphan medicinal products are still investigational products that are considered for designation on the basis of potential activity. An orphan designation is not a marketing authorisation. As a consequence, demonstration of quality, safety and efficacy will be necessary before this product can be granted a marketing authorisation.