Full preclinical validation of the 123I-labeled anti-PSMA antibody fragment ScFvD2B for prostate cancer imaging

Abstract

PurposeIn the context of prostate cancer (PCa) imaging, the aim of this study was to optimize (in vitro) the specificity and assess preclinically (in vivo) the tumor targeting properties of the 123I-scFvD2B antibody specific for prostate-specific membrane antigen (PSMA).Experimental DesignThe 123I-labeling conditions of the antibody fragment scFvD2B, produced in an eukaryotic system under GMP-compliant conditions, were optimized and assessed for purity and immunoreactivity. The specificity and potency of tumor uptake were tested in three preclinical in vivo models of subcutaneously xenografted human tumors expressing different levels of PSMA (LNCaP, naturally expressing PSMA; PC3-PIP and LS174T-PSMA, transfected with PSMA) or PC3 and LS174T, as negative controls, to assess the clearance, biodistribution and imaging potential of 123I-scFvD2B.ResultsThe set conditions of production and radiolabeling yielded a reagent suitable for human delivery thanks to the purity of the formulation and the high immunoreactivity. In all preclinical models 123I-scFvD2B showed specific targeting only to PSMA-positive tumors with the final specific activity ranging up to 1500 MBq/mg. Despite different levels of PSMA expression, biodistribution analyses and SPECT/CT imaging demonstrated similar results and maximal signal-to-background ratios 24 hours after injection.ConclusionsDue to its in vitro and in vivo properties, 123I-scFvD2B could be a promising tool for the early diagnosis of PCa, and may represent a molecular imaging option to monitor disease progression and assist in the clinical management of PCa patients.

Targeted Radionuclide Therapy of Prostate Cancer—From Basic Research to Clinical Perspectives

“…Recently, a comprehensive overview of the current literature on PSMA-targeted monovalent scFv fragments for radionuclide PET and SPECT imaging was presented by Diao et al [12]. The highly promising preclinical results in vitro were reported for scFv constructs developed from the D2B antibody and radiolabeled with 131 I ( 131 I-scFvD2B), 111 In ( 111 In-scFvD2B), 123 I ( 123 I-scFvD2B) and 124 I ( 124 I-scFvD2B) [90][91][92][93]. The PSMA-targeted scFv constructs were also developed from the huJ591 antibody (DOTA-cysteine-modified scFv fragment labeled with 64 Cu and its conjugate to DSPE-PEG micelles) for PET imaging [89].…”

Development of 177Lu-scFvD2B as a Potential Immunotheranostic Agent for Tumors Overexpressing the Prostate Specific Membrane Antigen

“…To establish the minimal amount of DOTA-scFvD2B necessary to obtain 177 Lu-DOTA-scFvD2B ( 177 Lu-scFvD2B) with a high radiochemical yield, 0.5 mL of 0.25 M sodium acetate buffer (pH 7.0), containing different concentrations of DOTA-scFvD2B (15,30,60 and 75 nmol), were incubated with 15 µL (from 100 to 370 MBq) of no-carrier-added 177 LuCl 3 (ITG) for 2 h at 37 °C. The radiochemical yield of 177 Lu-scFvD2B was assessed at 1 and 2 h by high performance liquid chromatography (HPLC).…”

“…ScFvD2B (MW 27 kDa) was produced in an eukaryotic system (ExcellGene) and purified on protein L-sepharose column (GE Healthcare) as previously described 13,15 . To synthesize the DOTA-scFvD2B conjugate, a concentrated solution of scFvD2B (10 mg/mL) in 0.2 M sodium carbonate buffer (pH 9.5) was incubated with p-SCN-Bz-DOTA at 37 °C using 1:2, 1:3 1:4 and 1:5 scFv:DOTA molar ratios.…”

Two decades of SPECT/CT – the coming of age of a technology: An updated review of literature evidence

“…The development of PET radioligands directed against the prostate-specific membrane antigen (PSMA) has revolutionized the diagnostic workup of prostate cancer [82,83]. 99m Tc-labelled PSMA-ligand agents have also recently been developed [84][85][86][87][88]. SPECT/CT with 99m Tc-MIP 1404 (PSMA-ligand subtype) enabled the detection of small LNs or additional metastases ( Fig.…”