The present invention relates to a method of producing sesquiterpene lactones of the thapsigargin family, the method comprising the steps of: (a) culturing plant cells of the genus Thapsia in a nutrient medium in a suspension cell culture, wherein the cells produce one or more sesquiterpene lactones of the thapsigargin family； and (b) recovering one or more sesquiterpene lactones of the thapsigargin family produced in (a). The present invention further relates to a suspension cell culture comprising plant cells of the genus Thapsia, wherein the plant cells are capable of producing one or more sesquiterpene lactones of the thapsigargin family and to a plant cell biomass comprising plant cells of the genus Thapsia obtained from said suspension cell culture.
