L-Histidinol-d3 ((S)-2-Amino-3-(1H-imidazol-5-yl)propan-1-ol-d3) is a deuterium-labeled form of L-Histidinol, which acts as an oral inhibitor of histidyl-tRNA synthetase. It disrupts the initial phase of protein synthesis, thereby affecting cell proliferation and metabolism. Additionally, L-Histidinol regulates the sensitivity of tumor cells to chemotherapeutic agents, potentially reducing the toxicity to normal tissues while enhancing the responsiveness of tumor cells to these agents.