282 - Alpha Particle Therapy with Bi-213-DTPA-hAnnA1 Antibody Targeting Murine Ovarian Cancer Cells

Purpose: Antibody-based oncology therapies rely on passive mechanisms for tumor delivery. The humanized antibody against Annexin A1 (hAnnA1) actively targets tumor endothelium and cancer cells for potentially better therapeutic outcomes. Our prior studies indicted 30200-luc and HGS2-luc OC cells showed in vitro and in vivo binding and retention of Zr-89-labeled hAnnA1 compared to control IgG1. This study assessed targeted alpha-particle therapy (TAT) using Bi-213 labelled hAnnA1 for the in vitro treatment of murine ovarian cancer (OC) cells.

Materials and Methods: hAnnA1 and IgG1 antibodies were conjugated with DTPA and radiolabeled with Bi-213 from an in-house packed generator; purity of radiolabeled Abs was confirmed with iTLC. Survival assays at 24- and 48-hour survival assays in 96-well plates (5,000 cells/well) included Bi-213-DTPA-hAnnA1/or-IgG, and untreated controls. Clonogenic assays (200 cells/well) were performed using Bi-213-DTPA-hAnnA1/or -IgG, hAnnA1, IgG, and untreated groups. A range of doses were studied with 3-5 µCi the highest levels. qPCR of the treated and untreated conditions from the survival assays was performed with GAPDH (control), PCNA, and RAD51. Two-way ANOVA with Tukey’s test assessed statistical significance (p< 0.05) using SAS 9.4.


Results: The specific activities of Bi-213-DTPA-hAnnA1 and Bi-213-DTPA-IgG were 0.8±0.3µCi/ug and 1.0±0.6µCi/mg, respectively (each >95% purity). The Bi-213-DTPA-hAnnA1 significantly reduced survival (p< 0.05) compared with Bi-213-DTPA-IgG or untreated cells; the effect was observed starting at doses of 5µCi and 2.5µCi for 30200 and for HGS2 cells. There was a significant decrease in colony number and size for Bi-213-DTPA-hAnnA1 compared with the control groups, starting at 3µCi for 30200 cells and 5µCi for HGS2 cells (p< 0.05). qPCR showed significantly decreased expression of PCNA and Rad51 for the Bi-213-DTPA-hAnnA1 group compared with the untreated groups (p< 0.05) for both cell lines.


Conclusion: Bi-213-DTPA-hAnnA1 TAT inhibited OC growth in vitro compared with controls, showing reduced colony counts, decreased proliferation, and decreased dsDNA damage repair markers at doses as low as 2.5µCi.