Drugs having long-term retention in target tissue

The present invention relates to a polyethylene glycol-bound ligand in which polyethylene glycol is bound to a ligand having a binding affinity for a specific receptor or a specific protein (i.e., an antigen), wherein the polyethylene glycol-bound ligand is not internalized into cells, a novel medicament in which a drug is introduced into the polyethylene glycol chain of the ligand, and a pharmaceutical composition containing the same as an effective ingredient