Bevacizumab Radioimmunotherapy (RIT) with Accelerated Blood Clearance Using the Avidin Chase.

The overexpression of vascular endothelial growth factor (VEGF) in varying types of solid tumor renders radioimmunotherapy (RIT) with the anti-VEGF antibody bevacizumab (BV) a promising treatment. However, the slow blood clearance of BV, which may increase the occurrence risk of hematotoxicity, hinders the application of BV-RIT. Using the avidin chase is a long-known blood clearance enhancement strategy for biotinylated-mAb. To enhance RIT efficacy by increasing the radioactivity dose, we evaluated the ability of avidin to accelerate the blood clearance of yttrium-90 (90Y)-labeled biotinylated BV (90Y-Bt-BV) in a xenograft mouse model of triple-negative breast cancer (TNBC). The biodistribution study in the TNBC xenograft mice confirmed the high and specific tumor accumulation of the indium-111 (111In)-BV. The blood clearance enhancement effect of the avidin chase was demonstrated in the normal mouse studies with 111In-Bt-BV. In the subsequent biodistribution studies with the tumor-bearing mice, an optimized dose of avidin injection subsequent to 111In-Bt-BV with an appropriate biotin valency successfully accelerated the blood clearance of 111In-Bt-BV without impairing its tumor accumulation level. The avidin chase enabled an increase in the maximum tolerated dose of 90Y-Bt-BV to twice as much as that of 90Y-BV in tumor-bearing mice and thereby significantly improved the therapeutic effect of 90Y-Bt-BV compared to 90Y-BV ( p < 0.05). These results underscored the potential usefulness of 90Y-bevacizumab-RIT with the avidin chase for the treatment of VEGF-positive tumors.