6-Aminophenanthridine is an antiprion agent. It inhibits prion formation in yeast- and mammalian-based screening assays when used alone and, to a greater extent, when used in combination with the α-adrenergic receptor agonist guanabenz . 6-Aminophenanthridine (300 µM) inhibits protein folding activity of the ribosome (PFAR) by directly competing with protein substrates for the active site and decreases the yield of refolded protein without affecting the refolding rate. It prevents progressive wing position defects in a Drosophila model of oculopharyngeal muscular dystrophy (OPMD) when larvae are raised on medium containing doses ranging from 300 to 400 µM and in adults following dietary administration of 1-3 mM doses. 6-Aminophenanthridine also reduces muscle degeneration and decreases the number of nuclear inclusions in thoracic muscle in a Drosophila model of OPMD.