title: Camelid single-domain antibody-fragment engineering for (pre)clinical in vivo molecular imaging applications: adjusting the bullet to its target.
abstract: BACKGROUND
  Molecular imaging is a fast developing field and there is a growing need for specific imaging tracers in the clinic. Camelid single-domain antibody-fragments (sdAbs) recently emerged as a new class of molecular imaging tracers.
  
  
  METHODS
  We review the importance of molecular imaging in the clinic and the use of camelid sdAbs as in vivo molecular imaging tracers. Interest in imaging tracers based on antibody fragments or man-made protein scaffolds expanded over the last years. Camelid sdAbs are small, monomeric binding fragments that are derived from unique heavy-chain-only antibodies. In vivo imaging studies with sdAbs targeting various cell membrane receptors in different disease models have been reported and more sdAb imaging tracers are under development. The first clinical trial with a camelid sdAb as a molecular imaging tracer targeting the breast cancer marker Human Epidermal growth factor Receptor 2 is currently ongoing.
  
  
  CONCLUSIONS
  We expect that the development and use of sdAbs as tracers for both preclinical and clinical molecular imaging applications will become widespread.
authors.affiliation: Laboratory of Cellular and Molecular Immunology (CMIM), Vrije Universiteit Brussel, Pleinlaan 2, Building E.8, 1050 Brussels, Belgium.
authors.forename: Jens
authors.initials: J
authors.lastname: De Vos
authors.forename: Nick
authors.initials: N
authors.lastname: Devoogdt
authors.forename: Tony
authors.initials: T
authors.lastname: Lahoutte
authors.forename: Serge
authors.initials: S
authors.lastname: Muyldermans
mesh_terms: D000818:Animals; D005069:Evaluation Studies as Topic; D006801:Humans; D007128:Immunoglobulin Fragments; D057054:Molecular Imaging; D061905:Single-Domain Antibodies
chemical_list: D007128:Immunoglobulin Fragments; D061905:Single-Domain Antibodies