There is provided a compound of Formula I wherein X is a ring system; R1 is any one of a sulphamate group, a phosphonate group, a thiophosphonate group, a sulphonate group or a sulphonamide group; R2 is any one of a sulphamate group, a phosphonate group, a thiophosphonate group, a sulphonate group or a sulphonamide group; wherein when X is a steroidal structure and both of R1 and R2 are sulphamate groups, the steroidal ring system (X) represents an oestrogen; and wherein said compound is capable of inhibiting steroid sulphatase (STS) activity and/or is capable of acting as a modulator of cell cycling and/or as a modulator of apoptosis and/or as a modulator of cell growth. There is also provided a compound of Formula VIII wherein R2 is any one of a sulphamate group, a phosphonate group, a thiophosphonate group, a sulphonate group or a sulphonamide group; and wherein said compound is capable of inhibiting steroid sulphatase (STS) activity and/or is capable of acting as a modulator of cell cycling and/or as a modulator of apoptosis and/or as a modulator of cell growth.