| 1. |
- Deyev, S., et al.
(författare)
-
Comparative Evaluation of Two DARPin Variants : Effect of Affinity, Size, and Label on Tumor Targeting Properties
- 2019
-
Ingår i: Molecular Pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 16:3, s. 995-1008
-
Tidskriftsartikel (refereegranskat)abstract
- Designed ankyrin repeat proteins (DARPins) are small engineered scaffold proteins that can be selected for binding to desirable molecular targets. High affinity and small size of DARPins render them promising probes for radionuclide molecular imaging. However, detailed knowledge on many factors influencing their imaging properties is still lacking. We have evaluated two human epidermal growth factor 2 (HER2)-specific DARPins with different size and binding properties. DARPins 9-29-H 6 and G3-H 6 were radiolabeled with iodine-125 and tricarbonyl technetium-99m and evaluated in vitro. A side-by-side comparison of biodistribution and tumor targeting was performed. HER2-specific tumor accumulation of G3-H 6 was demonstrated. A combination of smaller size and higher affinity resulted in a higher tumor uptake of G3-H 6 in comparison to 9-29-H 6 . Technetium-99m labeled G3-H 6 demonstrated a better biodistribution profile than 9-29-H 6 , with several-fold lower uptake in liver. Radioiodinated G3-H 6 showed the best tumor-to-organ ratios. The combined effect of affinity, molecular weight, scaffold composition, and nonresidualizing properties of iodine label provided radioiodinated G3-H 6 with high clinical potential for imaging of HER2.
|
|
| 2. |
- Vorobyeva, Anzhelika, et al.
(författare)
-
Comparison of tumor-targeting properties of directly and indirectly radioiodinated designed ankyrin repeat protein (DARPin) G3 variants for molecular imaging of HER2
- 2019
-
Ingår i: International Journal of Oncology. - : SPANDIDOS PUBL LTD. - 1019-6439 .- 1791-2423. ; 54:4, s. 1209-1220
-
Tidskriftsartikel (refereegranskat)abstract
- Evaluation of human epidermal growth factor receptor 2 (HER2) expression levels in breast and gastroesophageal cancer is used for the stratification of patients for HER2-targeting therapies. The use of radionuclide molecular imaging may facilitate such evaluation in a non-invasive way. Designed ankyrin repeat proteins (DARPins) are engineered scaffold proteins with high potential as probes for radionuclide molecular imaging. DARPin G3 binds with high affinity to HER2 and may be used to visualize this important therapeutic target. Studies on other engineered scaffold proteins have demonstrated that selection of the optimal labeling approach improves the sensitivity and specificity of radionuclide imaging. The present study compared two methods of labeling G3, direct and indirect radioiodination, to select an approach providing the best imaging contrast. G3-H6 was labeled with iodine-124, iodine-125 and iodine-131 using a direct method. A novel construct bearing a C-terminal cysteine, G3-GGGC, was site-specifically labeled using [125I]I-iodo-[(4-hydroxyphenyl)ethyl]maleimide (HPEM). The two radiolabeled G3 variants preserved binding specificity and high affinity to HER2-expressing cells. The specificity of tumor targeting in vivo was demonstrated. Biodistribution comparison of [131I]I-G3-H6 and [125I]I-HPEM-G3-GGGC in mice, bearing HER2-expressing SKOV3 xenografts, demonstrated an appreciable contribution of hepatobiliary excretion to the clearance of [125I]I-HPEM-G3-GGGC and a decreased tumor uptake compared to [131I]I-G3-H6. The direct label provided higher tumor-to-blood and tumor-to-organ ratios compared with the indirect label at 4 h post-injection. The feasibility of high contrast PET/CT imaging of HER2 expression in SKOV3 xenografts in mice using [124I]I-G3-H6 was demonstrated. In conclusion, direct radioiodination is the preferable approach for labeling DARPin G3 with iodine-123 and iodine-124 for clinical single photon emission computed tomography and positron emission tomography imaging.
|
|
| 3. |
- Vorobyeva, Anzhelika, et al.
(författare)
-
Optimal composition and position of histidine-containing tags improves biodistribution of Tc-99m-labeled DARP in G3
- 2019
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Radionuclide molecular imaging of HER2 expression in disseminated cancer enables stratification of patients for HER2-targeted therapies. DARP in G3, a small (14 kDa) engineered scaffold protein, is a promising probe for imaging of HER2. We hypothesized that position (C- or N-terminus) and composition (hexahistidine or (HE)(3)) of histidine-containing tags would influence the biodistribution of [Tc-99m]Tc(CO)(3)-labeled DARP in G3. To test the hypothesis, G3 variants containing tags at N-terminus (H-6-G3 and (HE)(3)-G3) or at C-terminus (G3-H-6 and G3-(HE)(3)) were labeled with [Tc-99m]Tc(CO)(3). Labeling yield, label stability, specificity and affinity of the binding to HER2, biodistribution and tumor targeting properties of these variants were compared side-by-side. There was no substantial influence of position and composition of the tags on binding of [Tc-99m]Tc(CO)(3)-labeled variants to HER2. The specificity of HER2 targeting in vivo was confirmed. The tumor uptake in BALB/c nu/nu mice bearing SKOV3 xenografts was similar for all variants. On the opposite, there was a strong influence of the tags on uptake in normal tissues. The tumor-to-liver ratio for [Tc-99m]Tc(CO)(3)-(HE)(3)-G3 was three-fold higher compared to the hexahistidine-tag containing variants. Overall, [Tc-99m]Tc(CO)(3)-(HE)(3)-G3 variant provided the highest tumor-to-lung, tumor-to-liver, tumor-to-bone and tumor-to-muscle ratios, which should improve sensitivity of HER2 imaging in these common metastatic sites.
|
|
