Improved contrast of affibody-mediated imaging of HER3 expression in mouse xenograft model through co-injection of a trivalent affibody for in vivo blocking of hepatic uptake

Abstract

Human epidermal growth factor receptor type 3 (HER3) plays a crucial role in the progression of many cancer types. In vivo radionuclide imaging could be a reliable method for repetitive detection of HER3-expression in tumors. The main challenge of HER3-imaging is the low expression in tumors together with endogenous receptor expression in normal tissues, particularly the liver. A HER3-targeting affibody molecule labeled with radiocobalt via a NOTA chelator [ 57 Co]Co-NOTA-Z 08699 has demonstrated the most favorable biodistribution profile with the lowest unspecific hepatic uptake and high activity uptake in tumors. We hypothesized that specific uptake of labeled affibody monomer might be selectively blocked in the liver but not in tumors by a co-injection of non-labeled corresponding trivalent affibody (Z 08699 ) 3 . Biodistribution of [ 57 Co]Co-NOTA-Z 08699 and [ 111 In]In-DOTA-(Z 08699 ) 3 was studied in BxPC-3 xenografted mice. [ 57 Co]Co-NOTA-Z 08699 was co-injected with unlabeled trivalent affibody DOTA-(Z 08699 ) 3 at different monomer:trimer molar ratios. HER3-expression in xenografts was imaged using [ 57 Co]Co-NOTA-Z 08699 and [ 57 Co]Co-NOTA-Z 08699 : DOTA-(Z 08699 ) 3 . Hepatic activity uptake of [ 57 Co]Co-NOTA-Z 08699 : DOTA-(Z 08699 ) 3 decreased with increasing monomer:trimer molar ratio. The tumor activity uptake and tumor-to-liver ratios were the highest for the 1:3 ratio. SPECT/CT images confirmed the biodistribution data. Imaging of HER3 expression can be improved by co-injection of a radiolabeled monomeric affibody-based imaging probe together with a trivalent affibody.

Evaluating the Therapeutic Efficacy of Mono- and Bivalent Affibody-Based Fusion Proteins Targeting HER3 in a Pancreatic Cancer Xenograft Model

“…than the bivalent variants 33A and 3A3 [24]. It has previously been shown that a trimeric anti-HER3 affibody (without an ABD) had a 10-fold higher hepatic uptake than a monomeric affibody, supposedly due to the slower dissociation of the multivalent affibody and HER3 sequestration [32]. It could be speculated that the bivalent therapeutic variants have a similar effect, and as a result, the hepatic uptake of 68 Ga-(HE) 3 -Z HER3 -NODAGA was observed in the 3A treated group, but not the 3A3 and 33A groups.…”

Influence of Residualizing Properties of the Radiolabel on Radionuclide Molecular Imaging of HER3 Using Affibody Molecules

“…This approach increased the tumor-to-liver ratio by ca. [41] in a BxPC-3 xenograft model. It has to be noted that although both EGFR and HER3 are expressed in normal tissues, including liver, the expression level of HER3 in tumors is appreciably lower than the level of EGFR.…”

“…Indirect radioiodination of (HE) 3 -Z HER3:08698 -DOTAGA using N-succinimidyl-para-(trimethylstannyl)benzoate was performed as described earlier for affibody molecules [49] and DARPins [48]. An aqueous solution of 0.1% acetic acid (60-90 µL) was added to radioiodine (40)(41)(42)(43)(44)(45). Then, N-succinimidyl-p-(trimethylstannyl)benzoate (6.5 nmoles, 2.5 µg, 2.5 µL of 1 mg/mL in 5% acetic acid in methanol) and chloramine-T (80 µg, 10 µL, 8 mg/mL in water) were added.…”

“…Further studies showed that the off-target interactions can be modulated by the composition of the radionuclide-chelator complex [31,[33][34][35]. The best tumor-to-liver ratio of 2.3 ± 0.5 was obtained at 24 h post-injection (pi) by a co-injection of [ 57 Co]Co-NOTA-Z HER3:08699 with a three-fold molar excess of unlabeled (Z08699) 3 HER3-affibody trimer [41].…”

Guest Edited Collection: Radioisotopes and radiochemistry in health science

“…Radiometals have their deserved place in the toolbox of nuclear medicine: cobalt ( 57 Co, 271.8 d; as a surrogate for 55 Co, 17.5 h) and indium ( 111 In, 2.8 d) were used as labels for affibody monomers targeting tumours in BxPC-3 xenografted mice 27 . A further contribution broaches the application of nanospheres labelled with 89 Zr (78.4 h) 28 , a positron emitter with a half-life roughly matching the in vivo circulation of antibodies.…”