Efficiency of succinylated gelatin and amino acid infusions for kidney uptake reduction of radiolabeled αvβ6-integrin targeting peptides: considerations on clinical safety profiles.

Abstract

68Ga-Trivehexin is an investigational PET radiopharmaceutical (NCT05799274) targeting αvβ6-integrin for PET imaging of carcinomas. 177Lu-D0301 is a structurally related therapeutic peptide tetramer. However, it showed considerable kidney uptake in rodents, impeding clinical applicability. We therefore evaluated the impact of different kidney protection strategies on the biodistribution of both agents in normal and tumor-bearing mice. Ex-vivo biodistribution of 68Ga-Trivehexin (90min p.i.) and 177Lu-D0301 (90min and 24h p.i.) was determined in healthy C57BL/6N and H2009 (human lung adenocarcinoma) xenografted CB17-SCID mice without and with co-infusion of 100µL of solutions containing 2.5% arginine + 2.5% lysine (Arg/Lys), 4% succinylated gelatin (gelofusine, gelo), or combinations thereof. Arg/Lys was injected either i.p. 30min before and after the radiopharmaceutical, or i.v. 2min before the radiopharmaceutical. Gelo was administered either i.v. 2min prior activity, or pre-mixed and injected together with the radiopharmaceutical (n = 5 per group). C57BL/6N mice were furthermore imaged by PET (90min p.i.) and SPECT (24h p.i.). Kidney uptake of 68Ga-Trivehexin in C57BL/6N mice was reduced by 15% (Arg/Lys i.p.), 25% (Arg/Lys i.v.), and 70% (gelo i.v.), 90min p.i., relative to control. 177Lu-D0301 kidney uptake was reduced by 2% (Arg/Lys i.p.), 41% (Arg/Lys i.v.), 61% (gelo i.v.) and 66% (gelo + Arg/Lys i.v.) 24h p.i., compared to control. Combination of Arg/Lys and gelo provided no substantial benefit. Gelo furthermore reduced kidney uptake of 177Lu-D0301 by 76% (90min p.i.) and 85% (24h p.i.) in H2009 bearing SCID mice. Since tumor uptake was not (90min p.i.) or only slightly reduced (15%, 24h p.i.), the tumor/kidney ratio was improved by factors of 3.3 (90min p.i.) and 2.6 (24h p.i.). Reduction of kidney uptake was demonstrated by SPECT, which also showed that the remaining activity was located in the cortex. The kidney uptake of both investigated radiopharmaceuticals was more efficiently reduced by gelofusine (61-85%) than Arg/Lys (25-41%). Gelofusine appears particularly suitable for reducing renal uptake of αvβ6-integrin targeted 177Lu-labeled peptide multimers because its application led to approximately three times higher tumor-to-kidney ratios. Since the incidence of severe adverse events (anaphylaxis) with succinylated gelatin products (reportedly 0.0062-0.038%) is comparable to that of gadolinium-based MRI or iodinated CT contrast agents (0.008% and 0.04%, respectively), clinical use of gelofusine during radioligand therapy appears feasible if similar risk management strategies as for contrast agents are applied.