25-nitro-20-epi-vitamin D analogue with anti-proliferative and cytoprotective properties: Biological and pharmacological evaluation.

We report the synthesis and pharmacological evaluation of UG-635, a novel 25-nitro vitamin D analogue bearing a 20-epimeric configuration. Cytotoxicity studies in SH-SY5Y neuroblastoma and HepG2 hepatocarcinoma cells showed that UG-635 is well tolerated at low concentrations but reduces viability at higher doses. Importantly, UG-635 demonstrated protective effects against oxidative stress in neuronal cells and exhibited anti-proliferative activity in breast cancer (MCF7) and osteoblast (MC3T3-E1) models, with efficacy comparable to calcitriol. Structural and crystallographic analyses revealed efficient binding to the vitamin D receptor (VDR), stabilizing its active conformation through favorable interactions with anchoring histidines. These findings highlight UG-635 as a promising vitamin D analogue with potential pharmacological relevance in cancer and neurodegenerative disease contexts, combining anti-proliferative and cytoprotective properties.