On the prevention of kidney uptake of radiolabeled DARPins.

Common clinical strategies were not effective for the reduction of kidney uptake of [99mTc]Tc(CO)3-G3. Both fructose and maleate lower the cellular ATP level in the proximal tubule cells and their reduction of the kidney reuptake indicates the involvement of an ATP-driven uptake mechanism. The decrease provided by maleate for both G3 and 9_29 DARPins indicates that their uptake proceeds through a mechanism independent of DARPin structure and binding site composition.