Patent ID: 8354455

Claim:
A compound of formula (I), or pharmaceutically acceptable salts thereof: wherein, a is 0; B is S—S; A is CH 2 ; A 1 is CH 2 ; D 1 represents a therapeutic agent comprising one or more of the functional groups selected from the group consisting of —NHR 1 , CONHR 1 , —OC(═O)NHR 1 , —SO 2 NHR 1 , —OSO 2 NHR 1 , —N(R 1 )C(═O)NHR 1 and —N(R 1 )SO 2 NHR 1 ; wherein the N atom in said functional groups is either a part of or directly attached to L 1 ; D 2 is selected from the group consisting of a peptide, a protein, a monoclonal antibody, a vitamin, R 2 , R 4 and a polymer; with the proviso that the derivatizable OH, SH, NH or CO 2 H groups of D 2 are involved in the formation of L 2 wherein the heteroatom of OH, SH or NH groups or C(═O) of the C(═O)OH group is either a part of or directly attached to L 2 ; E represents CH 2 ; L 1 is wherein, X represents at each occurrence O or NR 1 ; Y represents at each occurrence C═O; L 2 represents O; R 1 represents H or a bond to the same drug residue at an atom other than the atom to which N is attached; R 2 represents NH 2 ; R 4 represents at each occurrence H or a group selected from the group consisting of: R 6 represents at each occurrence H, Na + , K + or any other pharmaceutically acceptable metal ion and f is 0-6.