Lysine-specific demethylase 1 (LSD1) plays a vital role in the epigenetic regulation of various cancers, making it a promising therapeutic target for anticancer treatments. Herein, we designed and synthesized a novel series of 1H-pyrrolo[2,3-c]pyridin derivatives as potent LSD1 inhibitors. A detailed structure-activity relationship exploration was carried out to discover multiple derivatives with nanomolar enzymatic IC50 values. Further biological evaluation demonstrated that these compounds acted as selective and reversible LSD1 inhibitors. The representative compounds exhibited highly potent antiproliferative activity against both AML (MV4-11 and Kasumi-1) and SCLC (NCI-H526) cell lines. Additionally, they effectively activated CD86 mRNA expression in MV4-11 cells and induced differentiation of AML cell lines. Notably, the most promising compound 23e showed a favorable oral PK profile and effectively suppressed the tumor growth in an AML xenograft model. Overall, our medicinal chemistry efforts provide compound 23e as a lead compound for developing LSD1 inhibitors for the treatment of AML and other advanced malignancies.