Chromatin modifications, which involve alterations in DNA methylation and histone modifications, have an epigenetic influence on biological processes such as cellular differentiation and developmental transitions. Among the various post-translational histone modifications, lysine methylation has been extensively studied. The methylation of histone lysine residues is a reversible process, managed by enzymes known as histone lysine methyltransferases and demethylases. One specific demethylase, lysine-specific demethylase 1 (LSD1), removes methyl groups from mono- and di-methylated lysine 4 of histone H3 (H3K4me1/2) through an enzymatic oxidation reliant on flavin adenine dinucleotide. In addition, LSD1 has been highlighted as a potential target for lung cancer, neuroblastoma, and leukemia. Therefore, we have performed a drug discovery study on LSD1 and identified small molecules and peptides as LSD1 inhibitors. In this presentation, we introduced and discussed some peptide-based LSD1 inhibitors and proteolysis targeting chimeras (PROTACs) designed based on SNAIL1, which is a member of the SNAIL/SCRATCH family of transcription factors and interacts with LSD1.