Herein, the mono and dialkylation of pyridazino[4,5-b]indole were achieved with a set of alkylating agents, including amyl bromide, allyl bromide, benzyl bromide and ethyl chloroacetate in the presence of K₂CO₃/acetone or KOH/DMSO. The hydrazinolysis of mono and di-esters 10 and 11 gave the target hydrazides 12 and 13, which displayed promising, potent, and significant cytotoxic activity against the MCF-7 cell line with IC₅₀ values of 4.25 and 5.35 μm compared to that of the standard drug 5-FU (IC₅₀ 6.98 μm), respectively. RT-PCR analysis of the most active compound 12 was performed to determine its mode of action through the up-regulation of pro-apoptotic genes and inhibition of anti-apoptotic and PI3K/AKT/mTOR genes. The findings were consistent with the proposed mechanism illustrated in the in silico study. Further, the in vivo analysis exhibited its potent anti-cancer activity through the prolongation of survival parameters, and inhibition of ascetic fluid parameters in EAC-bearing mice.