The present invention relates to a hydrogel comprising a polymer, a first polypeptide and a polypeptide binding partner, wherein the polypeptide binding partner is a second polypeptide, a nucleic acid or a small molecule, and wherein the interaction between the first polypeptide and the polypeptide binding partner stabilizes the hydrogel and is modulated by the addition of a modulating compound. A drug may be physically entrapped in the hydrogel, bound to the polymer forming the hydrogel structure, or bound to the first polypeptide or the polypeptide binding partner, and then be set free on addition of the modulating compound. Such a hydrogel comprising a drug may be injected into a patient, and drug release modulated by orally administering the modulating compound.