Background/Objectives: The development of antitumor agents possessing low toxicity against non-cancerous cells is still a challenge in medicinal chemistry. In this paper, we report the antitumor activity of “hybrid structures” derived from the amino acid taurine. We have synthesized 26 compounds, structures of which were confirmed using NMR, X-ray diffractometry, and other techniques. Cytotoxicity of the obtained compounds has been evaluated using three human cancer cell lines. Pyrrolidine 4p has exhibited the strongest antiproliferative activity against HL-60 cells with an IC₅₀ of 76.7 μM, while IC₅₀ against normal cells was 176.3 μM. Water-soluble derivatives of taurine have been tested for antileukemia activity in mice of the BDF1 line. Compound 4p has been identified as the leading compound, which increases the mean survival time of mice from 40 to 100% as compared to the control group. Together, these results prove that taurine-based hybrid structures can be a promising scaffold for the discovery of potential antiproliferative agents.