– DNMT1/HDAC-IN-1 (compound (R)-23a), a potent dual inhibitor targeting both DNMT1 and HDAC, exhibits impressive inhibitory effects specifically on HDAC1 (HDAC1:IC50=0.05 μM), a major HDAC isoform that interacts with DNMT1 across multiple protein complexes involved in the transcriptional silencing of TSGs. This compound has been shown to remodel the tumor immune microenvironment and induce tumor regression, effectively reversing cancer-specific epigenetic abnormalities.