The present invention provides pharmaceutical compositions of an HDAC inhibitor and a chelatable metal compound. In one embodiment, the invention provides a method of treating cancer and alleviating the side effects of the HDAC inhibitor by administering the pharmaceutical composition. In another embodiment, the present invention also provides pharmaceutical compositions of metal HDAC inhibitor chelate complexes. In another embodiment, the invention provides methods of treating cancer by administering the pharmaceutical compositions. The invention provides crystalline compositions of metal HDAC inhibitor chelate complexes and methods of producing same.