Discovery of natural product-like spirooxindole derivatives as highly potent and selective LSD1/KDM1A inhibitors for AML treatment

Histone lysine specific demethylase 1 (LSD1) is a promising new therapeutic target for Cancer therapy. Following the work on the discovery of natural LSD1 inhibitor higenamine, we herein performed further structure-based design, synthesis, and extensive structure-activity relationship (SAR) studies, affording structurally new spirooxindole derivatives. Particularly, FY-56 was identified to be a highly potent LSD1 inhibitor (IC₅₀ = 42 nM) and showed high selectivity over monoamine oxidases (MAO-A/B). Mechanistic studies showed that FY-56 moderately inhibited the proliferation and clone formation of leukemia cells, induced H3K4me1/2 accumulation and p53 activation as well as reduced the mRNA levels of the transcription factors HOXA9 and MEIS1. Meanwhile, FY-56 induced differentiation of MOLM-13 and MV4-11 cells, accompanied by an enhanced percentage of markers characteristic to differentiated macrophages and monocytes. Further in vivo studies showed that FY-56 obviously reduced the proportion of CD45⁺/CD33⁺ leukocytes in peripheral blood and spleen, and significantly prolonged the survival rate of mice. Collectively, FY-56 represents a structurally novel, highly potent and selective LSD1 inhibitor and exhibits therapeutic promise for AML treatment. The spirooxindole scaffold derived from FY-56 could be used to design structurally new LSD1 inhibitors for treating human diseases.