Lactam-modified adeno-associated virus vectors

An adeno-associated virus (AAV) vector comprising a moiety according to formula (II):

• or a pharmaceutically acceptable salt thereof, wherein
• N* is a nitrogen atom of an amino group of an amino acid residue of the AAV vector's capsid;
• ----- represents the point of attachment to the AAV vector's capsid;
• Z is a functional moiety comprising a cell-type specific ligand, a labelling agent, a steric shielding agent, a drug moiety or combinations thereof;
• L is a linker;
• R1, R1, R2 and R2′ are each independently hydrogen, halogen, or an optionally substituted C1-6 alkyl;
• or
• R1 and R1′ or R2 and R2′, together with their intervening atoms, may come together of form an optionally substituted spiro-fused ring;
• or
• R1 and R2, together with their intervening atoms, may form an optionally substituted 3- to 7-membered saturated, partially unsaturated, or aryl or heteroaryl ring having 0-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.