Abstract: A star polymer of formula O[D1]-([X]-A(D2)-[Z]-[D3])n where O is a core; A is a polymer arm that comprises reactive monomers, hydrophilic monomers and/or charged monomers and is attached to the core; X is a linker molecule between the core and the polymer arm; Z is a linker molecule between the end of the polymer arm and D3; D1 is a drug molecule linked to the core; D2 is a drug molecule linked to reactive monomers distributed along the polymer arm; D3 is a drug molecule linked to the ends of the polymer arms; n is an integer number; [ ] denotes that the group is optional; and D2 is linked to the reactive monomers distributed along the polymer arm at a density of between 1 mol % and 80 mol %.