title: Development of 177Lu-nanobodies for radioimmunotherapy of HER2-positive breast cancer: evaluation of different bifunctional chelators.
abstract: Nanobodies show favourable pharmacokinetic characteristics for tumor targeting, including high tumor-to-background-ratios. Labelled with a therapeutic radionuclide, nanobodies could be used as an adjuvant treatment option for HER2-overexpressing minimal residual disease. The therapeutic radionuclide Lutetium-177 is linked to the nanobody using a bifunctional chelator. The choice of the bifunctional chelator could affect the in vivo behaviour of the radiolabeled nanobody. Consequently, we compared four different bifunctional chelators - p-SCN-Bn-DOTA, DOTA-NHS-ester, CHX-A"-DTPA or 1B4M-DTPA - in order to select the optimal chemical link between Lutetium-177 and a HER2 targeting nanobody. MS results revealed different degrees of chelator-conjugation. High stability in time was observed, together with nanomolar affinities on HER2-expressing tumor cells. Ex vivo biodistributions as well as SPECT/micro-CT analyses showed high activities in tumors expressing medium HER2 levels with low background activity except for the kidneys. The 1B4M-DTPA-coupled conjugate was further evaluated in a high HER2-expressing tumor model. Here, tumor uptake values of 5.99 ± 0.63, 5.12 ± 0.17, 2.83 ± 0.36 and 2.47 ± 0.38 %IA/g were obtained at 1, 3, 24 and 48h p.i., which coincided with exceptionally low background values, except for the kidneys, and unprecedented tumor-to-background ratios. No specific binding was observed in a HER2-negative model. In conclusion, the in-house developed anti-HER2 nanobody 2Rs15dHIS can be successfully labeled with (177) Lu using different bifunctional chelators. Both macrocyclic and acyclic chelators show high stability in time. High specific tumor uptake combined with the lowest background uptake was measured using the 1B4M-DTPA-based conjugate.
authors.affiliation: Radiobiology Unit, Molecular and Cellular Biology Expert Group, Belgian Nuclear Research Center (SCK•CEN), Mol, Belgium. mdhuyvet@vub.ac.be
authors.forename: Matthias
authors.initials: M
authors.lastname: D'Huyvetter
authors.forename: An
authors.initials: A
authors.lastname: Aerts
authors.forename: Catarina
authors.initials: C
authors.lastname: Xavier
authors.forename: Ilse
authors.initials: I
authors.lastname: Vaneycken
authors.forename: Nick
authors.initials: N
authors.lastname: Devoogdt
authors.forename: Marlies
authors.initials: M
authors.lastname: Gijs
authors.forename: Nathalie
authors.initials: N
authors.lastname: Impens
authors.forename: Sarah
authors.initials: S
authors.lastname: Baatout
authors.forename: Bernard
authors.initials: B
authors.lastname: Ponsard
authors.forename: Serge
authors.initials: S
authors.lastname: Muyldermans
authors.forename: Vicky
authors.initials: V
authors.lastname: Caveliers
authors.forename: Tony
authors.initials: T
authors.lastname: Lahoutte
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000276:immunology / Q000628:therapy*; D045744:Cell Line, Tumor; D002614:Chelating Agents; D005260:Female; D006801:Humans; D007700:Kinetics; D008187:Lutetium; D008297:Male; D051379:Mice; D053758:Nanoparticles; D004369:Pentetic Acid / Q000031:analogs & derivatives; D016499:Radioimmunotherapy / Q000379:methods*; D011868:Radioisotopes; D011877:Radionuclide Imaging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D002614:Chelating Agents; D008187:Lutetium; D004369:Pentetic Acid; D011868:Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases; C077295:2-(4-isothiocyanatobenzyl)-6-methyldiethylenetriaminepentaacetic acid