Heterogeneity of national legislation and practice on clinical trials with vulnerable patients based on the EU Clinical Trials Directive by the example of adults permanently incapable of giving informed consent.

In principle, persons wishing to participate in a clinical trial must give informed consent in advance after comprehensive information has been provided. Under certain conditions, it is possible to deviate from this requirement in the European Union (EU) in order to enable the participation of so-called vulnerable persons who are incapable of giving their informed consent. Kuthning et al. [1] have already dealt with general and specific aspects of vulnerable patients and the principle of informed consent in clinical trials. One group of vulnerable persons, for example, are adults temporarily or permanently incapable of giving consent due to their state of health. For a long period of time, no systematic and uniform legal basis for clinical trials existed in the EU as a whole. The Clinical Trials Directive (CTD) [2], adopted in 2001, aimed to change this by harmonizing all legal regulations on clinical trials applicable in the EU, but nevertheless allowing national deviations in implementation into national laws through opening clauses and aspects that were left unregulated. In view of the Clinical Trials Regulation (CTR) [3] which, according to the current status, will with high probability be applied from 2022 on, and which in future will be the legal basis for clinical trials with medicinal products in humans, applied directly in all EU member states, the necessity to take stock of the effects of the CTD was evident. The national deviations with regard to the participation of patients incapable of giving informed consent were investigated qualitatively and quantitatively by means of a systematic analysis of legislation in 16 EU countries and a retrospective database analysis of a European clinical trial registry over a ten-year observation period. Although the analysis initially showed a predominantly homogeneous picture, the differences between the EU member states became apparent in a detailed examination. The database analysis yielded a clear result, since in some countries the majority of clinical trials are carried out. The clearest difference was found between the legal analysis and the results of the evaluated clinical trials concerning adults who are permanently incapable of giving informed consent. A presumed association between the "degree of liberality" of the national law and the frequency of clinical trials conducted in the respective country could not be confirmed. In the past, the selection of countries for conducting a clinical trial was based less on legal requirements and more on experience and financial considerations.