The implementation of health technology assessment principles in public decisions concerning orphan drugs.

Purpose: Over the last few years, the share of public spending for orphan drugs (ODs) has increased in several western countries, raising concern on the exemptions granted to this sector with respect to the implementation of health technology assessment (HTA) principles. The aim of this paper is to shed light on both the HTA criteria adopted and the international agreements implemented in the OD regulation, given the new challenges imposed on western countries by a growing number of therapies for rare diseases. Methods: We carried out a literature review to analyse the development of the international debate on the adaptability of HTA criteria for the OD assessment and regulation. The time span lies between January 1990 and May 2018, and the policies considered relate to both market authorization and reimbursement decisions within western countries. We focus specifically on HTA criteria in some of the dimensions included in the Core Model of the European net for HTA (EUnetHTA). Results: OD high prices, the absence of clarity on the possible high revenues realized by the distribution of a new OD outside the national borders, the risk that – once marketed – a new OD can be used to treat common diseases, are all issues that raise concern on OD regulation and have to be carefully monitored by policymakers in the next future. Conclusions: Across western countries, the preferential track granted to ODs in the implementation of HTA principles is not homogeneous, but fragmented and differentiated. The need for common rules at an international level is underlined, with a view to assessing the sustainability of a sector which, due to this regulatory void, can lend itself to producers' strategic and opportunistic behaviours. [ABSTRACT FROM AUTHOR]