Participant-funded clinical trials on rare diseases.

The development of medicines for certain rare diseases can be cut short by lack of funding. In certain cases the patients themselves, or their relatives, occasionally fund the clinical trial in which they will be treated with the investigational medicine. There are three models of self-funded clinical research: two of them, 'pay to try' and 'pay to participate', have already been put into practice. The third, the 'plutocratic' proposal, which has been recently put forward is still a theoretical model. In this work the scientific, social and ethical benefits and risks of the two clinical research models, 'pay to participate and the 'plutocratic' proposal, are reviewed. Patient-funded clinical trials are frequently performed through crowdfunding. The most controversial aspects of this funding modality are also addressed in this article from several perspectives. Finally, a future scenario that would allow the launching of self-funded clinical trials in Spain by the 'plutocratic' proposal is proposed.