Abstract
BACKGROUND: Understanding the interaction between radiopharmaceuticals and human serum albumin (HSA) is essential for optimizing pharmacokinetics and therapeutic efficacy. This study evaluated the binding properties of (nat)Lu-FAPi-46 and (nat)Lu-FAP-2286 to HSA using theoretical and experimental techniques. RESULTS: Docking results revealed moderate affinities for (nat)Lu-FAPi-46 (- 9.7 kcal/mol) and (nat)Lu-FAP-2286 (- 7.8 kcal/mol), correlating with their lower blood retention (0.43% and 0.03% I.A./g at 4 h p.i.). Comparative docking of albumin-binding derivatives of FAPi-46 showed stronger binding, consistent with increased blood retention. Experimental analyses (fluorescence quenching, circular dichroism, and cyclic voltammetry) confirmed complex formation and conformational changes in HSA, validating the computational findings. CONCLUSIONS: Together, the computational and experimental results underscore the importance of albumin-binding in shaping the pharmacokinetic properties of FAP-targeted radiopharmaceuticals. Strategic optimization of albumin-binding linkers may improve stability, circulation time, and overall therapeutic performance in next-generation FAP-based agents.