Discovery of arylbenzylamines as PDE4 inhibitors with potential neuroprotective effect.

Growing evidence confirms the potential of PDE4 inhibitors for the treatment of Parkinson's disease. Our reported PDE4 inhibitors FCPR16 and FCPR03 have displayed neuroprotective effects in SH-SY5Y cells, but have very low oral bioavailability. To access analogues with improved bioavailability, a new series of arylbenzylamine derivatives were designed and synthesized. Preliminary screening results of the series showed that arylbenzylamine derivatives bearing a pyridin-3-amine side chain displayed good inhibitory activities against human PDE4B1 and PDE4D7 isoforms. Moreover, kinetic studies revealed that the most potent compounds 11r and 11s with mid-nanomolar IC ₅₀ values partially bind to PDE4B1 (I _max  = 93% and 90% respectively). Molecular docking results revealed the possible interactions of compounds 11r and 11s with upstream conserved region 2 (UCR2) of PDE4B1, which illuminate possible reasons for their partial inhibition against PDE4. Using a cell-based model of PD, compounds 11r and 11s were found to alleviate cellular apoptosis in SH-SY5Y cells induced by MPP ⁺ (1-methyl-4-phenylpyridinium), with this neuroprotective effect being greater than PDE4 inhibitor rolipram. Furthermore, compound 11r displayed nearly sevenfold oral bioavailability (8.20%) than FCPR03 (1.23%).
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