(R)-GSK-3685032 is the R-enantiomer of GSK-3685032. GSK-3685032 is a first-in-class, non-time-dependent, non-covalent, reversible, selective DNMT1 inhibitor with an IC 50 of 0.036 μM. GSK-3685032 induces robust loss of DNA methylation, transcriptional activation and inhibition of cancer cell growth.