The present disclosure relates to a lipid conjugated bivalent peptide ligand which bind to Protein Interacting with C Kinase-1 (PICK1) and thereby inhibit PICK1. The PICK1 inhibitors of the present disclosure comprise a peptide portion comprising two peptide ligands of PICK1, and a non-peptide portion comprising a linker, linking the two peptide ligands, and a lipid. The disclosure furthermore relates to therapeutic and diagnostic use of said PICK1 inhibitor for treatment of diseases or disorders associated with maladaptive plasticity.