Therapeutic Approaches to Prion Diseases.

Therapy of prion diseases represents an extremely challenging effort for scientists working in the field. These challenges are epitomized by 20 years of failures in clinical trials and preclinical investigations. However, the discovery that misfolded proteins involved in other neurodegenerative diseases show a prion-like mechanism of spreading, is positively impacting the prion drug discovery field. Herein, we describe those efforts that have contributed to strengthen the drug discovery process in prion diseases. Accordingly, we analyze the historical course of clinical trials that have assessed the efficacy of several chemically unrelated repositioned drugs. Unfortunately, none of them resulted successful. Thus, alternative approaches aiming at identifying innovative drugs with a completely new mechanism of action, have been recently pursued. In this respect, the multifactorial nature of prion diseases provides a strong foundation to the development of small molecules directed to two or multiple pathological targets, critically involved in the intricate disease pathogenesis (i.e., multitarget compounds). Second, the fact that misfolded proteins can be considered not only as therapeutic target, but also as neuropathological hallmark, lends support to the development of theranostics, i.e., single molecules with concomitant therapeutic and diagnostic properties. Although nobody knows whether these innovative tools will be brought to clinical trials, and the process is certainly time-consuming and demanding, the rewards are well worth the effort.