Deuterium-enriched 4-hydroxy-5-methoxy-N,1-dimethyl-2-oxo-N-[(4-trifluoromethyl) -phenyl]-1,2-dihydroquinoline-3-carboxamide, having a deuterium enrichment in the amide-N methyl group of at least 70%; or a salt thereof with a pharmaceutically acceptable organic or inorganic cation; and a method of preparing said compounds. The compounds are useful in therapy, e.g. for the treatment of a malignant hyperproliferative disorder or an autoimmune disease.