EU/3/10/738: Orphan designation for the ornithine translocase deficiency (hyperornithinaemia-hyperammonaemia homocitrullinuria (HHH) syndrom

Glyceryl tri-(4-phenylbutyrate)


On 10 June 2010, orphan designation (EU/3/10/738) was granted by the European Commission to Hyperion Therapeutics Limited, United Kingdom, for glyceryl tri-(4-phenylbutyrate) for the treatment of ornithine translocase deficiency (hyperornithinaemia-hyperammonaemia homocitrullinuria (HHH) syndrome).

Update: Glyceryl tri-(4-phenylbutyrate) (Ravicti) has been authorised in the EU since 27 November 2015. Ravicti is indicated for use as adjunctive therapy for chronic management of adult and paediatric patients ≥2 months of age with urea cycle disorders (UCDs) including deficiencies of carbamoyl phosphate-synthase-I (CPS), ornithine carbamoyltransferase (OTC), argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), arginase I (ARG) and ornithine translocase deficiency hyperornithinaemia-hyperammonaemia homocitrullinuria syndrome (HHH) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone.

Ravicti must be used with dietary protein restriction and, in some cases, dietary supplements (e.g., essential amino acids, arginine, citrulline, protein-free calorie supplements).


Key facts

Active substance
Glyceryl tri-(4-phenylbutyrate)
Intended use
Ornithine translocase deficiency (hyperornithinaemia-hyperammonaemia homocitrullinuria (HHH) syndrom
Orphan designation status
EU designation number
Date of designation

Immedica Pharma AB
Solnavagen 3 H
113 63

Review of designation

During its meeting of 6 to 8 October 2015, the Committee for Orphan Medicinal Products (COMP) reviewed the designations EU/3/10/733, EU/3/10/734, EU/3/10/735, EU/3/10/736, EU/3/10/737 and EU/3/10/738 for Ravicti (glycerol phenybutyrate1) as an orphan medicinal product for the treatment of the following urea cycle disorders: carbamoyl phosphate-synthase-1 deficiency, ornithine carbamoyltransferase deficiency, citrullinaemia type 1, argininosuccinic aciduria, hyperargininaemia and ornithine translocase deficiency (hyperornithinaemia-hyperammonaemia homocitrullinuria (HHH) syndrome). The COMP assessed whether, at the time of marketing authorisation, the medicinal product still met the criteria for orphan designation. The Committee looked at the seriousness and prevalence of the conditions, and the existence of other methods of treatment. As other methods of treatment are authorised in the European Union (EU) for three of the above conditions (carbamoyl phosphate-synthase-1 deficiency, ornithine carbamoyltransferase deficiency, and citrullinaemia type 1), the COMP also considered whether the medicine is of significant benefit to patients with these conditions. The COMP recommended that the orphan designations of the medicine be maintained2.

1Previously known as glyceryl tri-(4-phenybutyrate).

2The maintenance of the orphan designation at time of marketing authorisation would, except in specific situations, give an orphan medicinal product 10 years of market exclusivity in the EU. This means that in the 10 years after its authorisation similar products with a comparable therapeutic indication cannot be placed on the market.

Update history

November 2022The sponsor's address was updated.
June 2019The sponsorship was transferred to Immedica Pharma AB, Sweden.
January 2016The sponsorship was transferred to Horizon Pharma Ireland Limited, Ireland.
June 2015Hyperion Therapeutics Limited changed name to Horizon Therapeutics Limited.

Documents related to this orphan designation evaluation

  • List item

    Recommendation for maintenance of orphan designation at the time of marketing authorisation: Ravicti (glycerol phenylbutyrate) for the treatment of urea cycle disorders [carbamoyl phosphate-synthase-1 deficiency, ornithi... (PDF/95.27 KB)


    First published: 04/01/2016
    Last updated: 04/01/2016

  • Patients' organisations

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

    • European Organisation for Rare Diseases (EURORDIS), a non-governmental alliance of patient organisations and individuals active in the field of rare diseases.

    • Orphanet, a database containing information on rare diseases, which includes a directory of patients’ organisations registered in Europe.

    EU register of orphan medicines

    The list of medicines that have received an orphan designation in the EU is available on the European Commission's website:

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