Pifithrin-alpha is a small molecule p53 functional inhibitor reported to behave like an antiapoptotic agent in neurodegenerative models. Pifithrin-alpha is a prodrug that under physiological conditions spontaneously undergoes ring closure to yield pifithrin-beta. Pifithrin-beta demonstrated antiproliferative and neuroprotective effects in vitro. Pifithrin-beta is able to activate the aryl hydrocarbon receptor (AhR) in a complete independent way of the p53 inhibition.

Catharanthine is a terpene indole alkaloid produced by the medicinal plant Catharanthus roseus. Catharanthine is derived from strictosidine, but the exact mechanism by which this happens is currently unknown. Catharanthine is one of the two precursors that form vinblastine, the other being vindoline.