Identifying obstacles hindering the conduct of academic-sponsored trials for drug repurposing on rare-diseases: an analysis of six use cases oleh Marta del Álamo, Christoph Bührer, Dirk Fisher, Matthias Griese, Paul Lingor, Giovanni Palladini, Nicolas Sireau, Virginie Hivert, Luca Sangiorgi, Florence Guillot, Juliane Halftermeyer, Lenka Soucková, Kristýna Nosková, Regina Demlová