Abstract
Purpose
The folate receptor (FR) has emerged as an interesting diagnostic and therapeutic drug target with many potential applications in oncologic and inflammatory disorders. It was therefore the aim of this study to develop a folate-derived Ga-68-based positron emission tomography (PET) imaging tracer that is straightforward to radiolabel and could be broadly used in clinical studies. We validated its target binding affinity and specificity and compared it to [99mTc]EC20, the folate single-photon emission computed tomography (SPECT) imaging tracer that has been most extensively studied clinically so far.
Procedures
The new folic acid-derived PET imaging agent is linked via a polyethyleneglycol linker to the chelator 1,4,7-triazacyclononane-1,4,7-trisacetic acid (NOTA). This new compound, NOTA-folate, was labeled with gallium-68. We tested the probe’s stability in human plasma and its selectivity in vitro, using the FR-positive KB cell line as well as the FR-negative A549 cell line. The pharmacokinetic profile of [68Ga]NOTA-folate was evaluated in FR-positive KB mouse xenografts. Following intravenous injection of [68Ga]NOTA-folate (383 ± 53 μCi), PET/computed tomography (CT) imaging studies as well as biodistribution studies were performed using KB tumor-bearing mice (n = 3). In vitro as well as in vivo studies were performed in parallel with the SPECT imaging tracer [99mTc]EC20.
Results
In comparison to [99mTc]EC20 (radiochemical yield (RCY) = 82.0 ± 2.9 %, 91.8 ± 2.0 % purity), similar radiochemical yield (87.2 ± 6.9 %) and radiochemical purity (95.6 ± 1.8 %) could be achieved for [68Ga]NOTA-folate. For both tracers, we observed high affinity for FR-positive cells in vitro and high plasma stability. In PET/CT and biodistribution studies, [68Ga]NOTA-folate appeared to display slightly superior in vivo performance in comparison to [99mTc]EC20. In detail, 68Ga-NOTA-folate showed very good tumor uptake and retention (6.6 ± 1.1 %ID/g), relatively low kidney uptake (21.7 ± 1.1 %ID/g), and very low liver uptake (0.38 ± 0.08 %ID/g). In vivo blocking studies using a fivefold excess of EC20 reduced the tumor uptake to 2.5 ± 0.7 %ID/g, confirming receptor specific binding of [68Ga]NOTA-folate in vivo.
Conclusion
We validated a new Ga-68 folate-based PET imaging agent with excellent pharmacokinetics and tumor uptake. Based on a head-to-head comparison between both tracers, [68Ga]NOTA-folate is a suitable imaging probe for the delineation of FR-positive tumors and a promising candidate for clinical translation.
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References
Vergote I, Leamon CP (2015) Vintafolide: a novel targeted therapy for the treatment of folate receptor expressing tumors. Ther Adv Med Oncol 7:206–218
Ab O, Whiteman KR, Bartle LM et al (2015) IMGN853, a folate receptor-α (FRα)-targeting antibody-drug conjugate, exhibits potent targeted antitumor activity against FRα-expressing tumors. Mol Cancer Ther 14:1605–1613
Fani M, Tamma ML, Nicolas GP et al (2012) In vivo imaging of folate receptor positive tumor xenografts using novel 68Ga-NODAGA-folate conjugates. Mol Pharm 9:1136–1145
Kamen BA, Wang M-T, Streckfuss AJ et al (1988) Delivery of folates to the cytoplasm of MA104 cells is mediated by a surface membrane receptor that recycles. J Biol Chem 263:13602–13609
Wu M, Gunning W, Ratnam M (1999) Expression of folate receptor type a in relation to cell type malignancy, and differentiation in ovary, uterus, and cervix. Cancer Epidemiol Biomark Prev 8:775–782
Salazar MD, Ratnam M (2007) The folate receptor: what does it promise in tissue-targeted therapeutics. Cancer Metastasis Rev 26:141–152
Parker N, Turk MJ, Westrick E et al (2005) Folate receptor expression in carcinomas and normal tissues determined by a quantitative radioligand binding assay. Anal Biochem 338:284–293
Low PS, Kularatne SA (2009) Folate-targeted therapeutic and imaging agents for cancer. Curr Opin Chem Biol 13:256–262
Müller C (2013) Folate-based radiotracers for PET imaging—update and perspectives. Molecules 18:5005–5031
Sega EI, Low PS (2008) Tumor detection using folate receptor-targeted imaging agents. Cancer Metastasis Rev 27:655–664
Leamon CP, Low PS (2001) Folate-mediated targeting: from diagnostics to drug and gene delivery. Drug Discov Today 6:44–51
Hilgenbrink AR, Low PS (2005) Folate receptor-mediated drug targeting: from therapeutics to diagnostics. J Pharm Sci 94:2135–2146
van Dam GM, Themelis G, Crane LM et al (2011) Intraoperative tumor-specific fluorescence imaging in ovarian cancer by folate receptor-α targeting: first in-human results. Nat Med 17:1315–1319
Chen Q, Meng X, McQuade P et al (2016) Synthesis and preclinical evaluation of folate-NOTA-Al18F for PET imaging of folate-receptor-positive tumors. Mol Pharm 13:1520–1527
Leamon CP, Low PS (1991) Delivery of macromolecules into living cells: a method that exploits folate receptor endocytosis. Proc Natl Acad Sci U S A 88:5572–5576
Paulos CM, Turk MJ, Breur GJ, Low PS (2004) Folate receptor-mediated targeting of therapeutic and imaging agents to activated macrophages in rheumatoid arthritis. Adv Drug Deliv Rev 56:1205–1217
Low PS, Henne WA, Doorneweerd DD (2008) Discovery and development of folic-acid-based receptor targeting for imaging and therapy of cancer and inflammatory diseases. Acc Chem Res 41:120–129
O’Shannessy DJ, Somers EB, Maltzman J et al (2012) Folate receptor alpha (FRA) expression in breast cancer: identification of a new molecular subtype and association with triple negative disease. Springer Plus 1:22
Stover PJ (2004) Physiology of folate and vitamin B12 in health and disease. Nutr Res 62:S3–S12
Seo Y (2008) Quantification of SPECT and PET for drug development. Curr Radiopharm 1:17–21
Leamon CP, Parker MA, Vlahov IR et al (2002) Synthesis and biological evaluation of EC20: a new folate-derived, Tc-based radiopharmaceutical. Bioconjug Chem 13:1200–1210
Reddy JA, Westrick E, Santhapuram HK et al (2007) Folate receptor-specific antitumor activity of EC131, a folate-maytansinoid conjugate. Cancer Res 67:6376–6382
Weitman SD, Lark RH, Coney LR et al (1992) Distribution of the folate receptor GP38 in normal and malignant cell lines and tissues. Cancer Res 52:3396–3401
Ross JF, Chaudhuri PK, Ratnam M (1994) Differential regulation of folate receptor isoforms in normal and malignant tissues in vivo and in established cell lines. Physiologic and Clinical Implications Cancer 73:2432–2443
Morris RT, Joyrich RN, Naumann RW et al (2014) Phase II study of treatment of advanced ovarian cancer with folate-receptor-targeted therapeutic (vintafolide) and companion SPECT-based imaging agent (99mTc-etarfolatide). Ann Oncol 25:852–858
Serpe L, Gallicchio M, Canaparo R, Dosio F (2014) Targeted treatment of folate receptor-positive platinum-resistant ovarian cancer and companion diagnostics, with specific focus on vintafolide and etarfolatide. Pharmgenomics Pers Med 7:31–42
Holm J, Hansen SI, Høier-Madsen M, Bostad L (1992) A high-affinity folate binding protein in proximal tubule cells of human kidney. Kidney Int 41:50–55
Al Jammaz I, Al-Otaibi B, Amer S, Okarvi SM (2011) Rapid synthesis and in vitro and in vivo evaluation of folic acid derivatives labeled with fluorine-18 for PET imaging of folate receptor-positive tumors. Nucl Med Biol 38:1019–1028
Bettio A, Honer M, Müller C et al (2006) Synthesis and preclinical evaluation of a folic acid derivative labeled with 18F for PET imaging of folate receptor-positive tumors. J Nucl Med 47:1153–1160
Boss SD, Betzel T, Müller C et al (2016) Comparative studies of three pairs of α- and γ-conjugated folic acid derivatives labeled with fluorine-18. Bioconjug Chem 27:74–86
Fani M, Wang X, Nicolas G et al (2011) Development of new folate-based PET radiotracers: preclinical evaluation of 68Ga-DOTA-folate conjugates. Eur J Nucl Med Mol Imaging 38:108–119
Müller C, Forrer F, Schibli R et al (2008) SPECT study of folate receptor-positive malignant and normal tissues in mice using a novel 99mTc-radiofolate. J Nucl Med 49:310–317
Ross TL, Honer M, Lam PY et al (2008) Fluorine-18 click radiosynthesis and preclinical evaluation of a new 18F-labeled folic acid derivative. Bioconjug Chem 19:2462–2470
Smith-Jones PM, Stolz B, Bruns C et al (1994) Gallium-67/gallium-68-[DFO]-octreotide—a potential radiopharmaceutical for PET imaging of somatostatin receptor-positive tumors: synthesis and radiolabeling in vitro and preliminary in vivo studies. J Nucl Med 35:317–325
Mathias CJ, Lewis MR, Reichert DE et al (2003) Preparation of 66Ga- and 68Ga-labeled Ga(III)-deferoxamine-folate as potential folate-receptor-targeted PET radiopharmaceuticals. Nucl Med Biol 30:725–731
Mathias CJ, Wang S, Lee RJ et al (1996) Tumor-selective radiopharmaceuticals targeting via receptor-mediated endocytosis of gallium-67-deferoxamine-folate. J Nucl Med 37:1003–1008
Aljammaz I, Al-Otaibi B, Al-Hokbany N et al (2014) Development and pre-clinical evaluation of new 68Ga-NOTA-folate conjugates for PET imaging of folate receptor-positive tumors. Anticancer Res 34:6547–6556
Ross TL, Honer M, Müller C et al (2010) A new 18F-labeled folic acid derivative with improved properties for the PET imaging of folate receptor-positive tumors. J Nucl Med 51:1756–1762
Fisher RE, Siegel BA, Edell SL et al (2008) Exploratory study of 99mTc-EC20 imaging for identifying patients with folate receptor-positive solid tumors. J Nucl Med 49:899–906
Acknowledgements
The authors thank the Small Animal Imaging Core (P30 CA008748-48, S10 OD016207-01) and the Radiochemistry and Molecular Imaging Probes Core (P30 CA008748-48, S10 RR020892-01) for support. We also thank Endocyte, Inc. for generous support. The authors thank also Dr. Jason S. Lewis and Dr. NagaVaraKishore Pillarsetty for helpful discussions. Finally, the study was supported by grants from the National Institute of Health (K25 EB016673 for T.R.), the Center for Molecular Imaging and Nanotechnology of Memorial Sloan Kettering Cancer Center (for T.R.).
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M.G. is an employee of Endocyte, Inc.
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Brand, C., Longo, V.A., Groaning, M. et al. Development of a New Folate-Derived Ga-68-Based PET Imaging Agent. Mol Imaging Biol 19, 754–761 (2017). https://doi.org/10.1007/s11307-017-1049-y
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DOI: https://doi.org/10.1007/s11307-017-1049-y