Combination of high-throughput droplet radiosynthesizer and design of experiments for efficient radiopharmaceutical optimization

Radiopharmaceuticals deliver radionuclides to specific biological targets for PET or SPECT imaging or for therapy, enabling rapid and sensitive whole-body assessment or treatment of disease. With the expanding clinical adoption of imaging agents and radiopharmaceutical therapies, there is increasing demand for rapid development of new radiopharmaceuticals targeting emerging biological markers. A major bottleneck in early-stage radiopharmaceutical development is radiosynthesis optimization, which must reliably produce sufficient material for preclinical evaluation and clinical translation. Conventional radiochemistry is labor intensive, limited in throughput, and often requires months of iterative experimentation. Here, we integrate a high-throughput microscale droplet-based radiosynthesis platform with a design of experiments (DoE)–driven closed-loop optimization strategy to accelerate radiochemical development. The platform enables dozens of parallel microscale reactions using 10 μL droplets, while the optimization framework combines D-optimal experimental design with a steepest-ascent method to efficiently explore multidimensional design spaces. Iterative DoE cycles are used to systematically identify optimal reaction conditions with minimal experimental effort. As a proof of concept, we optimized the multi-step synthesis of 3′-deoxy-3′-[ 18 F]fluorothymidine ([ 18 F]FLT), comprehensively investigating seven variables across the fluorination and deprotection steps. Optimal conditions were identified using only two DoE cycles for fluorination and one for deprotection. The optimized microscale synthesis exhibited a final radiochemical yield of 71.2 ± 2.8% ( n = 4) in a synthesis time of 29 min including analytical-scale HPLC purification. This study demonstrates that high-throughput droplet-based synthesis coupled with DoE-guided closed-loop optimization provides an efficient and generalizable strategy for accelerating radiochemistry optimization.