Investigation of a Pharmacological Approach for Reduction of Renal Uptake of Radiolabeled ADAPT Scaffold Protein.

Anzhelika Vorobyeva,Tianqi Xu,Sarah Lindbo,Maryam Oroujeni,Javad Garousi,Sara S Rinne,Sophia Hober,Yongsheng Liu

doi:10.3390/molecules25194448

Abstract

Albumin binding domain-Derived Affinity ProTeins (ADAPTs) are small (5 kDa) engineered scaffold proteins that are promising targeting agents for radionuclide-based imaging. A recent clinical study has demonstrated that radiolabeled ADAPTs can efficiently visualize human epidermal growth factor receptor 2 (HER2) expression in breast cancer using SPECT imaging. However, the use of ADAPTs directly labeled with radiometals for targeted radionuclide therapy is limited by their high reabsorption and prolonged retention of activity in kidneys. In this study, we investigated whether a co-injection of lysine or gelofusin, commonly used for reduction of renal uptake of radiolabeled peptides in clinics, would reduce the renal uptake of [99mTc]Tc(CO)3-ADAPT6 in NMRI mice. In order to better understand the mechanism behind the reabsorption of [99mTc]Tc(CO)3-ADAPT6, we included several compounds that act on various parts of the reabsorption system in kidneys. Administration of gelofusine, lysine, probenecid, furosemide, mannitol, or colchicine did not change the uptake of [99mTc]Tc(CO)3-ADAPT6 in kidneys. Sodium maleate reduced the uptake of [99mTc]Tc(CO)3-ADAPT6 to ca. 25% of the uptake in the control, a high dose of fructose (50 mmol/kg) reduced the uptake by ca. two-fold. However, a lower dose (20 mmol/kg) had no effect. These results indicate that common clinical strategies are not effective for reduction of kidney uptake of [99mTc]Tc(CO)3-ADAPT6 and that other strategies for reduction of activity uptake or retention in kidneys should be investigated for ADAPT6.

Highlights

Targeting aberrant overexpression of molecular targets on cancer cells is an efficient strategy to deliver radioactivity to tumors and reduce damage to normal tissues
Albumin binding domain-Derived Affinity ProTeins (ADAPTs) variant carrying a hexahistidine-tag at C-terminus, termed ADAPT6, was ADAPT radiolabeled variant carrying a hexahistidine-tag
The two receptors involved in the reabsorption of some peptides and small proteins in renal proximal tubules were identified as megalin and cubilin [35]

Summary

Introduction

Targeting aberrant overexpression of molecular targets on cancer cells is an efficient strategy to deliver radioactivity to tumors and reduce damage to normal tissues. Previous studies suggest that there is a relationship between tumor uptake, size of a targeting agent, and its affinity [1,2,3]. Small targeting molecules have high accumulation in tumors at early time points. For prolonged tumor retention, high affinity is required [4]. Small engineered scaffold proteins (ESPs) with the size of. 4–20 kDa bind to selected antigens with high specificity and affinity [5,6,7]. The small size of ESPs is beneficial for their use in radionuclide diagnostic imaging as it allows imaging on the day of injection

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Discussion

Conclusion