Definitions of Rare Diseases and Orphan Drugs: Challenges to Harmonization and Paths to Legal Convergence in the CIS

The journal BMJ Open (2025) has published a systematic review titled "Global insight into rare disease and orphan drug definitions", which analyzes more than 200 unique definitions of rare diseases (RDs) and ultra-rare diseases (URDs), as well as orphan drugs (ODs) and ultra-orphan drugs (UODs), used in scientific and regulatory literature worldwide.

Download the article «Global insight into rare disease and orphan drug definitions»

Most definitions are based on quantitative criteria, primarily prevalence (from 1 in 1,000 to 1 in 200,000), less often - incidence or the total number of patients.

They are supplemented by qualitative features: severity of the condition, lack of alternative therapy, significant medical need, low commercial interest of pharmaceutical companies, high cost of development.

The lack of international harmonization in approaches creates serious obstacles:

• it is difficult to maintain international registries and it is impossible to compare statistics,
• it is difficult to evaluate therapy and conduct cross-border studies,
• there is inconsistency in access to orphan drugs and in regulatory procedures.

The problem is especially relevant for the CIS countries:

• there is no agreed upon definition of orphan status,
• different prevalence thresholds are applied,
• qualitative criteria are often not taken into account.

This impedes the development of a common regulatory framework, limits policy coordination and exacerbates unevenness in access to therapy.

These challenges will be the topic of discussion at the session “Legal and regulatory space for rare diseases: challenges, approaches, prospects”, which will be held as part of the II CIS Orphan Forum in Moscow.

The participants will discuss:

• existing approaches to defining orphan status and regulating orphan drugs in the CIS countries,
• principles of transparency and fairness in decision-making,
• prospects for convergence of positions and inclusion of uniform provisions in the model law-making of the CIS member states.

Session moderator - Sergey Ivanovich Savashinsky, Deputy Chairman of the Working Group on the Development of Principles of Bioethics and Evidence-Based Medicine of the Expert Council on Healthcare under the CIS IPA.

The Forum will be held online on June 26–27

Participation is free!

Registration for the Forum: https://orphan-cis.net/events/92/