Discovery of Orally Bioavailable and Brain-Penetrable Prodrugs of the Potent nSMase2 Inhibitor DPTIP

Abstract

Extracellular vesicles (EVs) can carry pathological cargo and play an active role in disease progression. Neutral sphingomyelinase-2 (nSMase2) is a critical regulator of EV biogenesis, and its inhibition has shown protective effects in multiple disease states. 2,6-<u>D</u>imethoxy-4-(5-<u>p</u>henyl-4-<u>t</u>hiophen-2-yl-1<i>H</i>-<u>i</u>midazol-2-yl)<u>p</u>henol (DPTIP) is one of the most potent (IC₅₀ = 30 nM) inhibitors of nSMase2 discovered to date. However, DPTIP exhibits poor oral pharmacokinetics (PK), limiting its clinical development. To overcome DPTIP's PK limitations, we synthesized a series of prodrugs by masking its phenolic hydroxyl group. When administered orally, the best prodrug (<b>P18</b>) with a 2',6'-diethyl-1,4'-bipiperidinyl promoiety exhibited >fourfold higher plasma (AUC_0-<i>t</i> = 1047 pmol·h/mL) and brain exposures (AUC_0-<i>t</i> = 247 pmol·h/g) <i>versus</i> DPTIP and a significant enhancement of DPTIP half-life (2 h <i>vs</i> ∼0.5 h). In a mouse model of acute brain injury, DPTIP released from <b>P18</b> significantly inhibited IL-1β-induced EV release into plasma and attenuated nSMase2 activity. These studies report the discovery of a DPTIP prodrug with potential for clinical translation.