Elucidation of muscle-binding peptides by phage display screening

Muscle makes up the largest tissue volume of the body, yet its size makes muscle-specific therapy difficult. This becomes particularly relevant when approaches to gene therapy for inherited myopathies are evaluated. Thus, a mechanism to target constructs or pharmaceuticals to muscle following intravenous injection would be advantageous. By screening a random phage display library we have identified a heptapeptide sequence, ASSLNIA, with enhanced in vivo skeletal and cardiac muscle binding. Phage carrying this peptide showed a 9- to 20-fold (depending on control tissue) increase in muscle selectivity compared with phage with no insert. When the injected individual phage clone was localized by immunohistochemistry, it was found within focal areas of the membrane of myofibers. Thus, the peptide identified represents a ligand that is capable of accessing skeletal and cardiac muscle from the lumen of blood vessels and could therefore readily be exploited for targeted delivery to muscle cells.