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

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-Dimethoxy-4-(5-phenyl-4-thiophen-2yl-1H-imidazol-2-yl)phenol (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 (P18) with a 2 ',6 '-diethyl-1,4 '-bipiperidinyl promoiety exhibited > fourfold higher plasma (AUC(0-t) = 1047 pmol.h/mL) and brain exposures (AUC(0-t) = 247 pmol.h/g) versus DPTIP and a significant enhancement of DPTIP half-life (2 h vs similar to 0.5 h). In a mouse model of acute brain injury, DPTIP released from P18 significantly inhibited IL-1 beta-induced EV release into plasma and attenuated nSMase2 activity. These studies report the discovery of a DPTIP prodrug with potential for clinical translation.