3-Deschloro-4-desfluoro-4-chloro-3-fluoro Gefitinib-d3 is the isotope labelled analog of 3-Deschloro-4-desfluoro-4-chloro-3-fluoro Gefitinib (D289540); an impurity of Gefitinib (G304000) which is a tyrosine kinase inhibitor that targets the epidermal growth factor receptor (EGFR).