EU/3/20/2278: Orphan designation for the treatment of immune thrombocytopenia

Immune thrombocytopenia is a condition in which the immune system (the body’s natural defences) attacks platelets, components in the blood that help it to clot. As a result, blood levels of platelets are low (thrombocytopenia), resulting in spontaneous bleeding and bruising. Although not all patients experience bleeding, severe bleeding can occur in some patients. Immune thrombocytopenia is a debilitating and life-threatening condition because of the risk of severe bleeding, especially in the brain.

At the time of designation, immune thrombocytopenia affected less than 3 in 10,000 people in the European Union (EU). This was equivalent to a total of fewer than 156,000 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).

^*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, Iceland, Liechtenstein, Norway and the United Kingdom. This represents a population of 519,200,000 (Eurostat 2020).

At the time of designation, authorised treatments included human normal immunoglobulin, Nplate (romiplostim), Revolade (eltrombopag), Tavlesse (fostamatinib) and certain corticosteroids. Some patients required surgery (splenectomy) to remove the spleen, an organ involved in the removal of platelets from the body.

The sponsor has provided sufficient information to show that the medicine might be of significant benefit for patients with immune thrombocytopenia. This is because in early studies patients for whom other treatments had not worked had improvements in platelet levels after treatment with the medicine. This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.

Rilzabrutinib binds to and blocks the activity of an enzyme called Bruton’s agammaglobulinemia tyrosine kinase (Btk). This enzyme is involved in activating the immune system, leading to damage to platelets. By blocking Btk, the medicine is expected to reduce platelet damage caused by the immune system and improve symptoms of the condition.

The effects of rilzabrutinib have been evaluated in experimental models.

At the time of submission of the application for orphan designation, clinical trials with rilzabrutinib in patients with immune thrombocytopenia were ongoing.

At the time of submission, rilzabrutinib was not authorised anywhere in the EU for the treatment of immune thrombocytopenia. Orphan designation of rilzabrutinib had been granted in the United States for this condition.

In accordance with Regulation (EC) No 141/2000, the COMP adopted a positive opinion on 23 April 2020, recommending the granting of this designation.

• the seriousness of the condition;
• the existence of alternative methods of diagnosis, prevention or treatment;
• either the rarity of the condition (affecting not more than 5 in 10,000 people in the EU) or insufficient returns on investment.

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