Engineered humanized diabodies for microPET imaging of prostate stem cell antigen-expressing tumors (original) (raw)
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Clinical Cancer Research, 2005
Prostate-specific membrane antigen (PSMA) is a cell surface protein that is overexpressed in prostate cancer, including hormone-refractory and metastatic disease. Our goal in this study was to develop a series of PSMA-based imaging agents for clinical use. Experimental Design: We have synthesized and evaluated the in vivo biodistribution of two radiolabeled urea derivatives that have high affinity for PSMA in severe combined immunodeficient mice harboring MCF-7 (breast, PSMA-negative), PC-3 (prostate, PSMA-negative), and LNCaP (prostate, PSMA-positive) xenografts. Radiopharmaceutical binding selectivity and tumor uptake were also evaluated in vivo using dedicated small animal positron emission tomography, single photon emission computed tomography, and gamma scintigraphic imaging devices. N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-[ 11 C]methyl-L-cysteine ([ 11 C]DCMC K i , 3.1 nmol/L) and N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-3-[ 125 I]iodo-L-tyrosine ([ 125 C]DCIT K i , 1.5 nmol/L) were synthesized using [ 11 C]CH 3 I and with [ 125 I]NaI/Iodogen, respectively. Results: At 30 minutes postinjection, [ 11 C]DCMC and [ 125 I]DCIT showed tumor/muscle ratios of 10.8 and 4.7, respectively, with clear delineation of LNCaP-derived tumors on imaging. MCF-7and PC-3-derived tumors showed significantly less uptake of [ 11 C]DCMC or [ 125 I]DCIT. Conclusion: These results show the feasibility of imaging PSMA-positive prostate cancer using low molecular weight agents.
Journal of Nuclear Medicine, 2009
Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein, is highly expressed by virtually all prostate cancers and is currently the focus of several diagnostic and therapeutic strategies. We have previously reported on the generation of several monoclonal antibodies (mAb) and antibody fragments that recognize and bind with high affinity to the extracellular domain of cell-adherent PSMA. This article reports the in vivo behavior and tumor uptake of the radiolabeled anti-PSMA mAb 3/A12 and its potential as a tracer for PET. Methods: The mAb 3/A12 was conjugated with the chelating agent 1,4,7,10-tetraazacyclododecane-N,N9,N$,N9$-tetraacetic acid (DOTA) and radiolabeled with 64 Cu. Severe combined immunodeficient mice bearing PSMA-positive C4-2 prostate carcinoma xenografts were used for small-animal PET imaging. Mice with PSMA-negative DU 145 tumors served as controls. For PET studies, each animal received 20-30 mg of radiolabeled mAb corresponding to an activity of 7.6-11.5 MBq. Imaging was performed 3, 24, and 48 h after injection. After the last scan, the mice were sacrificed and tracer in vivo biodistribution was measured by g-counting. Results: Binding of the mAb 3/A12 on PSMA-expressing C4-2 cells was only minimally influenced by DOTA conjugation. The labeling efficiency using 64 Cu and DOTA-3/A12 was 95.3% 6 0.3%. The specific activity after 64 Cu labeling was between 327 and 567 MBq/mg. After tracer injection, static small-animal PET images of mice with PSMA-positive tumors revealed a tumor-to-background ratio of 3.3 6 1.3 at 3 h, 7.8 6 1.4 at 24 h, and 9.6 6 2.7 at 48 h. In contrast, no significant tracer uptake occurred in the PSMA-negative DU 145 tumors. These results were confirmed by direct counting of tissues after the final imaging. Conclusion: Because of the high and specific uptake of 64 Cu-labeled mAb 3/A12 in PSMA-positive tumors, this ligand represents an excellent candidate for prostate cancer imaging and potentially for radioimmunotherapy.
Humanized Radioiodinated Minibody For Imaging of Prostate Stem Cell Antigen-Expressing Tumors
Clinical Cancer Research, 2008
Purpose: Prostate stem cell antigen (PSCA) is a cell surface glycoprotein that is overexpressed in prostate cancer, including hormone refractory disease. Previous preclinical studies showed the intact anti-PSCA antibodies, 1G8 and hu1G8, localized specifically to PSCA-expressing xenografts. Optimal micro positron emission tomography (microPET) imaging using hu1G8, however, required a delay of 168 hours postinjection. In this study, the 2B3 minibody (an 80-kDa engineered antibody fragment) has been produced for rapid targeting and imaging. Experimental Design: A gene encoding a PSCA-specific minibody,V L -linker-V H -hinge-huIgG1 C H 3, was assembled. The minibody was expressed by secretion from mammalian cells and purified by cation exchange chromatography. Relative affinity and specificity were determined by competition ELISA and flow cytometry. Serial microPET imaging using a 124 I-labeled minibody was conducted at 4 and 21 hours in mice bearing LAPC-9 AD, LAPC-9 AI, PC-3, and LNCaP-PSCA human prostate cancer xenografts. Tumor and tissue biodistribution was determined, and region of interest analysis of the images was conducted. Results: Yields of 20 mg/L purified 2B3 minibody were obtained that showed specific binding to LNCaP-PSCA cells. Purified 2B3 minibody showed specific binding to LNCaP-PSCA cells with an apparent affinity of 46 nmol/L. Radioiodinated 2B3 minibody showed rapid nontarget tissue and blood clearance kinetics (t 1/2 h = 11.2 hours). MicroPET scanning using the 124 I-2B3 minibody showed both androgen-dependent and -independent tumors as early as 4 hours and excellent high contrast images at 21hours postinjection. Conclusions: Imaging PSCA-positive prostate cancer is feasible using an intermediate size antibody fragment at 21hours.
Clinical Cancer Research, 2005
Purpose: Prostate-specific membrane antigen (PSMA) is a cell surface protein that is overexpressed in prostate cancer, including hormone-refractory and metastatic disease. Our goal in this study was to develop a series of PSMA-based imaging agents for clinical use. Experimental Design: We have synthesized and evaluated the in vivo biodistribution of two radiolabeled urea derivatives that have high affinity for PSMA in severe combined immunodeficient mice harboring MCF-7 (breast, PSMA-negative), PC-3 (prostate, PSMA-negative), and LNCaP (prostate, PSMA-positive) xenografts. Radiopharmaceutical binding selectivity and tumor uptake were also evaluated in vivo using dedicated small animal positron emission tomography, single photon emission computed tomography, and gamma scintigraphic imaging devices. N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-[11C]methyl-l-cysteine ([11C]DCMC Ki, 3.1 nmol/L) and N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-3-[125I]iodo-l-tyrosine ([125C]DCIT Ki, 1.5 nmol...
Journal of Nuclear Medicine, 2014
Prostate stem cell antigen (PSCA) is expressed on the cell surface in 83%-100% of local prostate cancers and 87%-100% of prostate cancer bone metastases. In this study, we sought to develop immu-noPET agents using 124 I-and 89 Zr-labeled anti-PSCA A11 minibodies (scFv-C H 3 dimer, 80 kDa) and evaluate their use for quantitative immunoPET imaging of prostate cancer. Methods: A11 anti-PSCA minibody was alternatively labeled with 124 I-or 89 Zr-desferrioxamine and injected into mice bearing either matched 22Rv1 and 22Rv1· PSCA or LAPC-9 xenografts. Small-animal PET data were obtained and quantitated with and without recovery coefficient-based partialvolume correction, and the results were compared with ex vivo biodistribution. Results: Rapid and specific localization to PSCA-positive tumors and high-contrast imaging were observed with both 124 Iand 89 Zr-labeled A11 anti-PSCA minibody. However, the differences in tumor uptake and background uptake of the radiotracers resulted in different levels of imaging contrast. The nonresidualizing 124 Ilabeled minibody had lower tumor uptake (3.62 6 1.18 percentage injected dose per gram [%ID/g] 22Rv1·PSCA, 3.63 6 0.59 %ID/g LAPC-9) than the residualizing 89 Zr-labeled minibody (7.87 6 0.52 %ID/g 22Rv1·PSCA, 9.33 6 0.87 %ID/g LAPC-9, P , 0.0001 for each), but the 124 I-labeled minibody achieved higher imaging contrast because of lower nonspecific uptake and better tumor-to-soft-tissue ratios (22Rv1·PSCA:22Rv1 positive-to-negative tumor, 13.31 6 5.59 124 I-A11 and 4.87 6 0.52 89 Zr-A11, P 5 0.02). Partial-volume correction was found to greatly improve the correspondence between small-animal PET and ex vivo quantification of tumor uptake for immunoPET imaging with both radionuclides. Conclusion: Both 124 Iand 89 Zr-labeled A11 anti-PSCA minibody showed high-contrast imaging of PSCA expression in vivo. However, the 124 I-labeled A11 minibody was found to be the superior imaging agent because of lower nonspecific uptake and higher tumor-to-soft-tissue contrast. Partialvolume correction was found to be essential for robust quantification of immunoPET imaging with both 124 I-and 89 Zr-labeled A11 minibody.
Contrast Media & Molecular Imaging, 2014
a D2B is a new monoclonal antibody directed against an extracellular domain of prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer. The potential of D2B IgG, and F(ab′) 2 and Fab fragments of this antibody for targeting prostate cancer was determined in mice bearing subcutaneous prostate cancer xenografts. The optimal time point for imaging was determined in biodistribution and microSPECT imaging studies with 111 In-D2B IgG, 111 In-capromab pendetide, 111 In-D2B F(ab′) 2 and 111 In-D2B Fab fragments in mice with PSMA-expressing LNCaP and PSMA-negative PC3 tumors at several time points after injection. All 111 In-labeled antibody formats specifically accumulated in the LNCaP tumors, with highest uptake of 111 In-D2B IgG and 111 In-capromab pendetide at 168 h p.i. (94.8 ± 19.2% injected dose per gram (ID/g) and 16.7 ± 2.2% ID/g, respectively), whereas uptake of 111 In-D2B F(ab′) 2 and 111 In-D2B Fab fragments peaked at 24 h p.i. (12.1 ± 3.0% ID/g and 15.1 ± 2.9% ID/g, respectively). Maximum LNCaP tumor-to-blood ratios were 13.0 ± 2.3 (168 h p.i.), 6.2 ± 0.7 (24 h p.i.), 23.0 ± 4.0 (24 h p.i.) and 4.5 ± 0.6 (168 h p.i.) for 111 In-D2B IgG, 111 In-F(ab′) 2 , 111 In-Fab and 111 In-capromab pendetide, respectively. LNCaP tumors were clearly visualized with microSPECT with all antibody formats. This study demonstrates the feasibility of D2B IgG, F(ab′) 2 and Fab fragments for targeting PSMA-expressing prostate cancer xenografts.
First-in-Man Evaluation of 2 High-Affinity PSMA-Avid Small Molecules for Imaging Prostate Cancer
Journal of Nuclear Medicine, 2013
This phase 1 study was performed to determine the pharmacokinetics and ability to visualize prostate cancer in bone, soft-tissue, and the prostate gland using 123 I-MIP-1072 and 123 I-MIP-1095, novel radiolabeled small molecules targeting prostate-specific membrane antigen. Methods: Seven patients with a documented history of prostate cancer by histopathology or radiologic evidence of metastatic disease were intravenously administered 370 MBq (10 mCi) of 123 I-MIP-1072 and 123 I-MIP-1095 2 wk apart in a crossover trial design. 123 I-MIP-1072 was also studied in 6 healthy volunteers. Whole-body planar and SPECT/CT imaging was performed and pharmacokinetics studied over 2-3 d. Target-to-background ratios were calculated. Absorbed radiation doses were estimated using OLINDA/EXM. Results: 123 I-MIP-1072 and 123 I-MIP-1095 visualized lesions in soft tissue, bone, and the prostate gland within 0.5-1 h after injection, with retention beyond 48 h. Target-to-background ratios from planar images averaged 2:1 at 1 h, 3:1 at 4-24 h, and greater than 10:1 at 4 and 24 h for SPECT/CT. Both agents cleared the blood in a biphasic manner; clearance of 123 I-MIP-1072 was approximately 5 times faster. 123 I-MIP-1072 was excreted in the urine, with 54% and 74% present by 24 and 72 h, respectively. In contrast, only 7% and 20% of 123 I-MIP-1095 had been renally excreted by 24 and 72 h, respectively. Estimated absorbed radiation doses were 0.054 versus 0.110 mGy/MBq for the kidneys and 0.024 versus 0.058 mGy/MBq for the liver, for 123 I-MIP-1072 and 123 I-MIP-1095, respectively. Conclusion: 123 I-MIP-1072 and 123 I-MIP-1095 detect lesions in soft tissue, bone, and the prostate gland at as early as 1-4 h. These novel radiolabeled small molecules have excellent pharmacokinetic and pharmacodynamic profiles and warrant further development as diagnostic and potentially when labeled with 131 I therapeutic radiopharmaceuticals.
Molecular imaging, 2013
The humanized antibody (hu1G8) has been shown to localize to prostate stem cell antigen (PSCA) and image PSCA-positive xenografts. We previously constructed hu1G8 anti-PSCA antibody fragments and tested them for tumor targeting and the ability to image prostate cancer at early and late time points postinjection by positron emission tomography (PET). We now then compare the PET imaging and the radioactivity accumulation properties in prostate cancer tumors and nontarget tissues to determine the superior 124I-labeled hu1G8 antibody format. 124I-labeled diabody, minibody, scFv-Fc, scFv-Fc double mutant (DM), and parental IgG were administered into severe combined immunodeficiency (SCID) mice bearing LAPC-9 xenografts and followed by whole-body PET imaging of mice at preselected time points. Regions of interest were manually drawn around tumor and nontarget tissues and evaluated for radioactivity accumulation. The 124I-hu1G8 IgG has its best time point for tumor high-contrast imaging at...
Contrast Media & Molecular Imaging, 2014
a D2B is a new monoclonal antibody directed against an extracellular domain of prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer. The potential of D2B IgG, and F(ab′) 2 and Fab fragments of this antibody for targeting prostate cancer was determined in mice bearing subcutaneous prostate cancer xenografts. The optimal time point for imaging was determined in biodistribution and microSPECT imaging studies with 111 In-D2B IgG, 111 In-capromab pendetide, 111 In-D2B F(ab′) 2 and 111 In-D2B Fab fragments in mice with PSMA-expressing LNCaP and PSMA-negative PC3 tumors at several time points after injection. All 111 In-labeled antibody formats specifically accumulated in the LNCaP tumors, with highest uptake of 111 In-D2B IgG and 111 In-capromab pendetide at 168 h p.i. (94.8 ± 19.2% injected dose per gram (ID/g) and 16.7 ± 2.2% ID/g, respectively), whereas uptake of 111 In-D2B F(ab′) 2 and 111 In-D2B Fab fragments peaked at 24 h p.i. (12.1 ± 3.0% ID/g and 15.1 ± 2.9% ID/g, respectively). Maximum LNCaP tumor-to-blood ratios were 13.0 ± 2.3 (168 h p.i.), 6.2 ± 0.7 (24 h p.i.), 23.0 ± 4.0 (24 h p.i.) and 4.5 ± 0.6 (168 h p.i.) for 111 In-D2B IgG, 111 In-F(ab′) 2 , 111 In-Fab and 111 In-capromab pendetide, respectively. LNCaP tumors were clearly visualized with microSPECT with all antibody formats. This study demonstrates the feasibility of D2B IgG, F(ab′) 2 and Fab fragments for targeting PSMA-expressing prostate cancer xenografts.
The Prostate, 2010
BACKGROUND. The prostate specific membrane antigen (PSMA) is expressed by virtually all prostate cancers and represents an ideal target for diagnostic and therapeutic strategies. This article compares the in vivo behavior and tumor uptake of three different radiolabeled anti-PSMA monoclonal antibodies (mAbs) and corresponding F(ab) 2 and Fab fragments thereof. METHODS. The mAbs 3/A12, 3/F11, and 3/E7 and fragments of 3/A12 were conjugated with the chelating agent DOTA and radiolabeled with 64 Cu. For the microPET imaging studies, SCID mice bearing PSMA-positive C4-2 and PSMA-negative DU 145 prostate cancer xenografts were used. Each animal received 20-30 mg radiolabeled mAb or fragment corresponding to an activity of 8-14 MBq. Imaging was performed 3, 24, and 48 hr post-injection. After the last scan, mice were sacrificed and tracer in vivo biodistribution was measured by gamma-counting. RESULTS. Static microPET images of mice with PSMA-positive tumors revealed a high uptake of the mAbs in the C4-2 tumors at 24 and 48 hr after tracer injection and only a minimal distribution in the DU 145 tumors and other organs. In contrast, the F(ab) 2 and Fab fragments of 3/A12 were detected at a high extend in the kidney but not in the C4-2 tumors. These results were confirmed by gamma counting of dissected organs after the final imaging. CONCLUSIONS. Due to the high and specific uptake of the 64 Cu-labeled mAbs in PSMApositive tumors, these antibodies represent excellent tools for prostate cancer imaging.