The present invention provides a pharmaceutical compound, or pharmaceutically acceptable salt thereof, for use in medicine, wherein said compound is of formula I
wherein
R is a pharmaceutically active moiety;
Ar is an aromatic moiety;
X is a linker group; and
Y is a moiety comprising two phosphonate groups.
Further aspects of the invention relate to a method for palliative and curative treatment of bone disorders and cancer related disorders, such as breast cancer.