Hydrogels with biodegradable crosslinking

A method to prepare a drug-releasing degradable hydrogel, which method comprises

• (a) providing a first multi-armed polymer wherein each arm is terminated by a group comprising orthogonal first and second functional groups, which first orthogonal functional group is different from said second orthogonal functional group;
• (b) reacting said first multi-armed polymer of (a) with a linker-drug conjugate wherein said conjugate comprises a third functional group that reacts with only the first orthogonal functional group to obtain a derivatized first polymer;
• and
• (c) reacting the derivatized first polymer obtained in (b) with a crosslinker coupled to a second multi-armed polymer wherein said crosslinker comprises a fourth functional group that reacts with only the second orthogonal functional group present on said derivatized polymer to obtain said drug-releasing degradable hydrogel, or
• (d) reacting said first multi-armed polymer of (a) with a crosslinker coupled to a second multi-armed polymer wherein said crosslinker comprises a fourth functional group that reacts only with the second orthogonal functional group to obtain a crosslinked polymer, and
• (e) reacting the crosslinked polymer of (d) with a linker-drug conjugate, wherein said conjugate comprises a third functional group that reacts with only the first orthogonal functional group to obtain a said drug-releasing degradable hydrogel.