<sup>64</sup>Cu-labeled daratumumab F(ab')<sub>2</sub> fragment enables early visualization of CD38-positive lymphoma.

Kang, Lei; Li, Cuicui; Yang, Qi; Sutherlin, Logan; Wang, Lin; Chen, Zhao; Becker, Kaelyn V; Huo, Nan et al. · Eur J Nucl Med Mol Imaging · 2022

basic_science · Level V

Where this comes from

Abstract

Abnormal CD38 expression in some hematologic malignancies, including lymphoma, has made it a biomarker for targeted therapies. Daratumumab (Dara) is the first FDA-approved CD38-specific monoclonal antibody, enabling successfully immunoPET imaging over the past years. Radiolabeled Dara however has a long blood circulation and delayed tumor uptake which can limit its applications. The focus of this study is to develop <sup>64</sup>Cu-labeled Dara-F(ab')<sub>2</sub> for the visualization of CD38 in lymphoma models. F(ab')<sub>2</sub> fragment was prepared from Dara using an IdeS enzyme and purified with Protein A beads. Western blotting, flow cytometry, and surface plasmon resonance (SPR) were performed for in vitro assay. Probes were labeled with <sup>64</sup>Cu after the chelation of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). Small animal PET imaging and quantitative analysis were performed after injection of <sup>64</sup>Cu-labeled Dara-F(ab')<sub>2</sub>, IgG-F(ab')<sub>2</sub>, and Dara for evaluation in lymphoma models. Flow cytometry and SPR assay proved the specific binding ability of Dara-F(ab')<sub>2</sub> and NOTA-Dara-F(ab')<sub>2</sub> in vitro. Radiolabeling yield of [<sup>64</sup>Cu]Cu-NOTA-Dara-F(ab')<sub>2</sub> was over 90% and with a specific activity of 4.0 ± 0.6 × 10<sup>3</sup> MBq/μmol (n = 5). PET imaging showed [<sup>64</sup>Cu]Cu-NOTA-Dara-F(ab')<sub>2</sub> had a rapid and high tumor uptake as early as 2 h (6.9 ± 1.2%ID/g) and peaked (9.5 ± 0.7%ID/g) at 12 h, whereas [<sup>64</sup>Cu]Cu-NOTA-Dara reached its tumor uptake peaked at 48 h (8.3 ± 1.4%ID/g, n = 4). In comparison, IgG-F(ab')<sub>2</sub> and HBL-1 control groups found no noticeable tumor uptake. [<sup>64</sup>Cu]Cu-NOTA-Dara-F(ab')<sub>2</sub> had significantly lower uptake in blood pool, bone, and muscle than [<sup>64</sup>Cu]Cu-NOTA-Dara and its tumor-to-blood and tumor-to-muscle ratios were significantly higher than controls. [<sup>64</sup>Cu]Cu-NOTA-Dara-F(ab')<sub>2</sub> showed a rapid and high tumor uptake in CD38-positive lymphoma models with favorable imaging contrast, showing its promise as a potential PET imaging agent for future clinical applications.

Medical subject headings

Read the full text

View on PubMed · Publisher (DOI)