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Orphan designation

On 12 October 2017, orphan designation (EU/3/17/1941) was granted by the European Commission to Capnia (UK) Ltd, United Kingdom, for diazoxide choline for the treatment of Prader-Willi syndrome.

In December 2017, Capnia (UK) Ltd changed name to Soleno Therapeutics UK Ltd.

What is Prader-Willi syndrome?

Prader-Willi syndrome is an inherited condition caused by defects in specific regions of chromosome 15. This causes a wide range of symptoms, some of which can appear at birth, such as feeding problems, small size and reduced muscle strength. During childhood further symptoms develop, including increased appetite leading to constant eating and severe obesity, short stature, incomplete sexual development, learning difficulties and behavioural problems, such as aggression and stubbornness.

Prader-Willi syndrome is a life-long debilitating and life-threatening disease because of its serious symptoms, particularly learning difficulties, behavioural problems and obesity.

What is the estimated number of patients affected by the condition?

At the time of designation, Prader-Willi syndrome affected approximately 0.3 in 10,000 people in the European Union (EU). This was equivalent to a total of around 15,000 people*, and is below the ceiling for orphan designation, which is 5 people in 10,000. This isbased 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 28), Norway, Iceland and Liechtenstein. This represents a population of 515,700,000 (Eurostat 2017).

What treatments are available?

At the time of designation, growth hormone was authorised in the EU for treating Prader-Willi syndrome. In addition, symptoms were treated or managed in various ways, including supervised access to food to prevent obesity.

The sponsor has provided sufficient information to show that the medicine might be of significant benefit for patients with Prader-Willi syndrome, with data showing that it may reduce the excessive food intake – benefit not seen with current therapy. This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.

How is this medicine expected to work?

The way diazoxide choline works in Prader-Willi syndrome is unclear, but it is thought to stimulate potassium channels in the brain, which in turn reduces production of a substance called neuropeptide Y that nerve cells use to communicate with neighbouring cells. Neuropeptide Y is responsible for stimulating appetite. By reducing its production, diazoxide choline is expected to reduce the excessive food intake seen in patients with Prader-Willi syndrome.

What is the stage of development of this medicine?

The effects of diazoxide choline have been evaluated in experimental models.

At the time of submission of the application for orphan designation, clinical trials with the medicine in patients with Prader-Willi syndrome were ongoing.

At the time of submission, diazoxide was authorised in some EU countries for the treatment of hypoglycaemia (low blood glucose levels) and hypertensive crises (sudden, dangerously high blood pressure).

At the time of submission, diazoxide choline was not authorised anywhere in the EU for Prader-Willi syndrome. Orphan designation of diazoxide choline had been granted in the United States for this condition.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 5 October 2017 recommending the granting of this designation.

Opinions on orphan medicinal product designations are based on the following three criteria
  • 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.

Key facts

Product details for <p>diazoxide choline</p>
Active substancediazoxide choline
Medicine Name
Disease/conditiontreatment of Prader-Willi syndrome
Date of decision12/10/2017
Orphan decision numberEU/3/17/1941

Review of designation

The Committee for Orphan Medicinal Products reviews the orphan designation of a product if it is approved for marketing authorisation.

Sponsor's contact details

Soleno Therapeutics UK Ltd
43 High Street
Marlow SL7 1BA
United Kingdom
Tel. +44 1628 876432

Patients' organisations

For contact details of patients’ organisations whose activities are targeted at rare diseases see:

  • Orphanet, a database containing information on rare diseases, which includes a directory of patients’ organisations registered in Europe;
  • European Organisation for Rare Diseases (EURORDIS), a non-governmental alliance of patient organisations and individuals active in the field of rare diseases.