4-(4-Acetyl-phenoxy)-butyric acid

4-(4-Acetylphenoxy)butanoic acid (CAS 65623-82-7) serves as a core structural unit in acid-sensitive hydrazone linker systems utilized in antibody-drug conjugates (ADCs). Its primary function is to act as a molecular bridge connecting the antibody to cytotoxic agents, such as maytansinoids. Owing to the hydrazone bond within its structure, this linker exhibits high stability under the neutral pH conditions of systemic circulation, thereby minimizing premature release of the cytotoxic payload and reducing off-target toxicity. Upon internalization of the ADC by tumor cells, the hydrazone bond undergoes rapid hydrolytic cleavage in the acidic microenvironment of the lysosome (pH 4.5–5.0), enabling precise and efficient release of the cytotoxic agent to selectively eliminate tumor cells.