Comparative evaluation of dimeric and monomeric forms of ADAPT scaffold protein for targeting of HER2-expressing tumours

Javad Garousi, Sarah Lindbo, Jesper Borin, Emma von Witting, Anzhelika Vorobyeva, Maryam Oroujeni, Bogdan Mitran, Anna Orlova, Jos Buijs, Vladimir Tolmachev, Sophia Hober

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


ADAPTs are small engineered non-immunoglobulin scaffold proteins, which have demonstrated very promising features as vectors for radionuclide tumour targeting. Radionuclide imaging of human epidermal growth factor 2 (HER2) expression in vivo might be used for stratification of patients for HER2-targeting therapies. ADAPT6, which specifically binds to HER2, has earlier been shown to have very promising features for in vivo targeting of HER2 expressing tumours. In this study we tested the hypothesis that dimerization of ADAPT6 would increase the apparent affinity to HER2 and accordingly improve tumour targeting. To find an optimal molecular design of dimers, a series of ADAPT dimers with different linkers, -SSSG- (DiADAPT6L1), -(SSSG) 2 - (DiADAPT6L2), and -(SSSG) 3 - (DiADAPT6L3) was evaluated. Dimers in combination with optimal linker lengths demonstrated increased apparent affinity to HER2. The best variants, DiADAPT6L2 and DiADAPT6L3 were site-specifically labelled with 111 In and 125 I, and compared with a monomeric ADAPT6 in mice bearing HER2-expressing tumours. Despite higher affinity, both dimers had lower tumour uptake and lower tumour-to-organ ratios compared to the monomer. We conclude that improved affinity of a dimeric form of ADAPT does not compensate the disadvantage of increased size. Therefore, increase of affinity should be obtained by affinity maturation and not by dimerization.

Original languageEnglish
Pages (from-to)37-48
Number of pages12
JournalEuropean Journal of Pharmaceutics and Biopharmaceutics
Publication statusPublished - Jan 2019
Externally publishedYes


  • Dimer
  • HER2
  • Indium-111
  • Iodine-125
  • Radionuclide molecular imaging

ASJC Scopus subject areas

  • Biotechnology
  • Pharmaceutical Science

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