From the same paper, curcumin is mentioned. While everyone waits for re-purposed drugs to make it out of these trials, maybe curcumin could help now.

Curcumin (diferuloylmethane) also reduces significantly cell toxicity of α-Syn aggregates by binding to preformed oligomers and fibrils46 with effectiveness comparable with doxycycline (1:1 molar ratio)47. However, the instability, low solubility, little oral bioavailability of curcumin limit its clinical applications and to overcome this drawback, some structural curcumin analogues with antiaggregation properties are been developed. In this context, no human long-term toxicity studies have been reported until now with curcumin structural analogues48. On the contrary, oral administration of doxycycline proved to be a safe and effective drug for dermatologically long-term treatments49,50. Moreover, it was also reported that sub-antibiotic doses of doxycycline have no effect on the composition or antibiotic resistance of different microflora51.