The aim of this study is to report and describe all the patients with confirmed diagnosis of inherited metabolic disease (IMD) treated with orphan medicinal products (OMPs) in a cohort of adult patients followed in a reference center for rare diseases (Lausanne University Hospital, CHUV) from 2017-2022.

The development of novel therapies for inherited metabolic diseases, considered has OMPs, has improved the care of these patients. OMPs include a wide range of therapies from dietary products, enzyme replacement, substrate inhibitors, coenzyme replacement to more recently, gene therapy. Despite an increasing use of these therapies, they are still considered highly specialized treatments for very small groups of patients and share the characteristic of aiming to treat small populations with targeted therapies, which leads to higher costs and difficulties in obtaining clinical evidence. Drugs are approved for marketing and orphan designation by medical agencies based on their efficacy and safety.

In Switzerland, a separate country-specific process decides whether an approved drug is reimbursed. Because of the growing number of expensive OMPs, their reimbursement through public health insurances is increasingly manifesting itself as a moral dilemma for decision-makers. It may take a median of several years after submission of the first application by a pharmaceutical company for an orphan drug to become available to patients.

Considering the increasing number of OMP approvals and the still ethical challenge concerning their reimbursement, this study aims to share the experience of a single center in treating adult IMDs with OMPs but also in implementing novel therapies for rare diseases not yet covered by health insurers in Switzerland.

A database was created in 2017 including all patients with IMD followed at the Adult Metabolic Clinic in the CHUV. This database was part of a protocol submitted and approved by the Ethics committee (# 2017-02328). The results of this first analysis were published in the Journal of Orphan Rare Diseases. Investigators will use this database to identify all the patients treated with OMPs. Electronic and paper patient charts from the Division of Genetic Medicine will be reviewed for type of IMD and treatment. All variables will be entered in an excel database.

Inclusion Criteria:

• Age = or > 16 years
• Biological and/or genetically confirmed diagnosis of IMD

Exclusion Criteria:

• Age < 16 years
• Document attesting refusal to participate

Outpatient clinic for Adult patients with IMD from the Lausanne University Hospital (Division of Genetic Medicine)