Prodrugs (MRS7422, MRS7476) of highly selective A3
adenosine receptor (AR) agonists Cl-
IB-MECA and
MRS5698, respectively, were synthesized by succinylation of the 2' and 3'
hydroxyl groups, and the parent, active drug was shown to be readily liberated upon incubation with liver
esterases. The
prodrug MRS7476 had greatly increased aqueous solubility compared with parent
MRS5698 and was fully efficacious and with a longer duration than MRS7422 in reversing mouse
neuropathic pain (chronic constriction injury model, 3 μmol/kg, p.o.), a known A3AR effect. MRS7476 (5 mg/kg, p.o., twice daily) was found to protect against non-
alcoholic steatohepatitis (NASH) in the STAM mouse model, indicated by the
NAFLD activity score. Hepatocyte ballooning,
IL-10 production, and liver histology were significantly normalized in the MRS7476-treated mice, but not
liver fibrosis (no change in ACTA2 levels) or
inflammation. Hepatic expression of ADORA3 in human
NAFLD patients was 1.9-fold lower compared to normal controls. Adora3 expression determined by qPCR in primary mouse liver was associated with the stellate cells, and its mouse full body A3AR knockout worsened liver markers of
inflammation and steatosis. Thus, we have introduced a reversible
prodrug strategy that enables water solubility and in vivo activity of masked A3AR agonists in models of two disease conditions.