Kynurenine is an amino acid that plays a vital role in several biochemical processes in the body. However, during the manufacturing process of kynurenine-based drugs, impurities can be formed, which may affect the quality, safety, and efficacy of the drug. Kynurenine impurities can be formed due to various factors such as incomplete reaction, side reactions, and contaminants. Therefore, it is crucial to monitor and control the levels of kynurenine impurities to ensure the quality and safety of the drug.