Key-protease inhibition regimens promote tumor targeting of neurotensin radioligands

Neurotensin subtype 1 receptors (NTS1R) represent attractive molecular targets for directing radiolabeled neurotensin (NT) analogs to tumor lesions for diagnostic and therapeutic purposes. This approach has been largely undermined by the rapid in vivo degradation of linear NT-based radioligands. Herein, we aim to increase the tumor targeting of three99mTc-labeled NT analogs by the in-situ inhibition of two key proteases involved in their catabolism. DT1 ([N4- Gly7]NT(7-13)), DT5 ([N4-βAla7,Dab9]NT(7-13)), and DT6 ([N4-βAla7,Dab9,Tle12]]NT(7-13)) were labeled with99mTc. Their profiles were investigated in NTS1R-positive colon adenocarcinoma WiDr cells and mice treated or not with the neprilysin (NEP)-inhibitor phosphoramidon (PA) and/or the angiotensin converting enzyme (ACE)-inhibitor lisinopril (Lis). Structural modifications led to the partial stabilization of99mTc-DT6 in peripheral mice blood (55.1 ± 3.9% intact), whereas99mTc-D

Impact of clinically tested NEP/ACE inhibitors on tumor uptake of [111In-DOTA]MG11

Background: We have recently shown that treatment of mice with the neutral endopeptidase (NEP) inhibitor phosphoramidon (PA) improves the bioavailability and tumor uptake of biodegradable radiopeptides. For the truncated gastrin radiotracer [111In-DOTA]MG11 ([(DOTA)DGlu10]gastrin(10–17)), this method led to impressively high tumor-to-kidney ratios. Translation of this concept in the clinic requires the use of certified NEP inhibitors, such as thiorphan (TO) and its orally administered prodrug racecadotril (Race). Besides NEP, angiotensin-converting enzyme (ACE) has also been implicated in the catabolism of gastrin analogs. In the present study, we first compared the effects induced by NEP inhibition (using PA, TO, or Race) and/or by ACE inhibition (using lisinopril, Lis) on the biodistribution profile of [111In-DOTA]MG11 in mice. In addition, we compared the efficacy of PA and TO at different administered doses to enhance tumor uptake. Methods: [111In-DOTA]MG11 was coinjected with (a) vehicle, (b) PA (300 μg), (c) TO (150 μg), (d) Lis (100 μg), (e) PA (300 μg) plus Lis (100 μg), or (f) 30–40 min after intraperitoneal (ip) injection of Race (3 mg) in SCID mice bearing AR42J xenografts. In addition, [111In-DOTA]MG11 was coinjected with vehicle, or with progressively increasing amounts of PA (3, 30, or 300 μg) or TO (1.5, 15, and 150 μg) in SCID mice bearing twin A431-CCK2R(+/−) tumors. In all above cases, biodistribution was conducted at 4 h postinjection (pi). Results: During NEP inhibition, the uptake of [111In-DOTA]MG11 in the AR42J tumors impressively increased from 1.8 ± 1.0 % ID/g (controls) to 15.3 ± 4.7 % ID/g (PA) and 12.3 ± 3.6 % ID/g (TO), while with Race tumor values reached 6.8 ± 2.8 % ID/g. Conversely, Lis had no effect on tumor uptake and no additive effect when coinjected with PA. During the dose dependence study in mice, PA turned out to be more efficacious in enhancing tumor uptake of [111In-DOTA]MG11 in the CCK2R-positive tumors compared to equimolar amounts of TO. In all cases, renal accumulation remained low, resulting in notable increases of tumor-to-kidney ratios. Conclusions: This study has confirmed NEP as the predominant degrading enzyme of [111In-DOTA]MG11 and ruled out the involvement of ACE in the in vivo catabolism of the radiotracer. NEP inhibition with the clinically tested NEP

One step closer to clinical translation: Enhanced tumor targeting of [99mTc]Tc-DB4 and [111In]In-SG4 in mice treated with entresto

Background: Peptide radioligands may serve as radionuclide carriers to tumor sites overexpressing their cognate receptor for diagnostic or therapeutic purposes. Treatment of mice with the neprilysin (NEP)-inhibit

Localization of Tc-99m-GRP Analogs in GRPR-Expressing Tumors: Effects of Peptide Length and Neprilysin Inhibition on Biological Responses

The overexpression of gastrin-releasing peptide receptors (GRPRs) in frequently occurring human tumors has provided the opportunity to use bombesin (BBN) analogs as radionuclide carriers to cancer sites for diagnostic and therapeutic purposes. We have been alternatively exploring human GRP motifs of higher GRPR selectivity compared to frog BBN sequences aiming to improve pharmacokinetic profiles. In the present study, we compared two differently truncated human endogenous GRP motifs: GRP(14–27) and GRP(18–27). An acyclic tetraamine was coupled at the N-terminus to allow for stable binding of the SPECT radionuclide 99mTc. Their biological profiles were compared in PC-3 cells and in mice without or with coinjection of phosphoramidon (PA) to induce transient neprilysin (NEP) inhibitio

Preclinical pharmacokinetics, biodistribution, radiation dosimetry and toxicity studies required for regulatory approval of a phase I clinical trial with 111In-CP04 in medullary thyroid carcinoma patients

Introduction: From a series of radiolabelled cholecystokinin (CCK) and gastrin analogues, 111In-CP04 (111In-DOTA-(DGlu)6-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2) was selected for further translation as a diagnostic radiopharmaceutical towards a first-in-man study in patients with medullary thyroid carcinoma (MTC). A freeze-dried kit formulation for multicentre application has been developed. We herein report on biosafety, in vivo stability, biodistribution and dosimetry aspects of 111In-CP04 in animal models, essential for the regulatory approval of the clinical trial. Materials and methods: Acute and extended single dose toxicity of CP04 was tested in rodents, while the in vivo stability of 111In-CP04 was assessed by HPLC analysis of mouse blood samples. The biodistribution of 111In-CP04 prepared from a freeze-dried kit was studied in SCID mice bearing do

Radiolabeled gastrins in CCK2R-positive tumor targeting

In this thesis, several novel radiolabeled gastrin analogs were developed preclinically in vitro as well as in vivo in animal models. In addition, the effect of in situ enzyme inhibition on metabolic stability and tumor uptake of the same gastrin radioligands was investigated

99mTc]Tc-DB1 Mimics with Different-Length PEG Spacers: Preclinical Comparison in GRPR-Positive Models

Background: The frequent overexpression of gastrin-releasing peptide receptors (GRPRs) in human cancers provides the rationale for delivering clinically useful radionuclides to tumor sites using peptide carriers. Radiolabeled GRPR antagonists, besides being safer for human use, have often shown higher tumor uptake and faster background clearance than agonists. We herein compared the biological profiles of the GRPR-antagonist-based radiotracers [99mTc]Tc-[N4-PEGx-DPhe6,Leu-NHEt

Theranostic perspectives in prostate cancer with the gastrin-releasing peptide receptor antagonist NeoBOMB1: Preclinical and first clinical results

We recently introduced the potent gastrin-releasing peptide receptor (GRPR) antagonist 68Ga-SB3 (68Ga-DOTA-p-Aminomethylaniline-diglycolic acid-DPhe-Gln-Trp-Ala-Val-Gly-His-Leu-NHEt), showing excellent tumor localizing efficacy in animal models and in patients. By replacement of the C-Terminal Leu13-Met14-NH2 dipeptide of SB3 by Sta13-Leu14-NH2, the novel GRPR antagonist NeoBOMB1 was generated and labeled with different radiometals for theranostic use. We herein report on the biologic profile of resulting 67/68Ga-, 111In-, and 177Lu-NeoBOMB1 radioligands in GRPR-expressing cells and mouse models. The first evidence of prostate cancer lesion visualization in men using 68Ga-NeoBOMB1 and PET/CT is also presented. Methods: NeoBOMB1 was radiolabeled with 67/68Ga, 111In, and 177Lu according to published protocols. The respective metalated species natGa-, natIn-, and natLu-NeoBOMB1 were also synthesized and used in competition binding experiments against [125I-Tyr4]BBN in GRPRpositive PC-3 cell membranes. Internalization of 67Ga-, 111In-, and 177Lu-NeoBOMB1 radioligands was studied in PC-3 cells at 37°C, and their metabolic stability in peripheral mouse blood was determined by high-performance liquid chromatography analysis of blood samples. Biodistribution was performed by injecting a 67Ga-, 111In-, or 177Lu-NeoBOMB1 bolus (74, 74, or 370 kBq, respectively, 100 mL, 10 pmol total peptide6 40 nmol Tyr4-BBN:

Tarikh lihat anak bulan Syawal 25 April

Background: The GRPR-antagonist-based radioligands [67/68Ga/111In/177Lu]NeoBOMB1 have shown excellent theragnostic profiles in preclinical prostate cancer models, while [68Ga]NeoBOMB1 effectively visualized prostate cancer lesions in patients. We were further interested to explore the theragnostic potential of NeoBOMB1 in GRPR-positive mammary carcinoma, by first studying [67Ga]NeoBOMB1 in breast cancer models; Methods: We investigated the profile of [67Ga]NeoBOMB1, a [68Ga]NeoBOMB1 surrogate, in GRPR-expressing T-47D cells and animal models; Results: NeoBOMB1 (IC50s of 2.2 ± 0.2 nM) and [natGa]NeoBOMB1 (IC50s of 2.5 ± 0.2 nM) exhibited high affinity for the GRPR. At 37◦C [67Ga]NeoBOMB1 strongly bound to the T-47D cell-membrane (45.8 ± 0.4% at 2 h), internalizing poorly, as was expected for a radioantagonist. [67Ga]NeoBOMB1 was detected >90% intact in peripheral mouse blood at 30 min pi. In mice bearing T-47D xenografts, [67Ga]NeoBOMB1 specifically localized in the tumor (8.68 ± 2.9% ID/g vs. 0.6 ± 0.1% ID/g during GRPR-blockade at 4 h pi). The unfavorably high pancreatic uptake could be considerably reduced (206.29 ± 17.35% ID/g to 42.46 ± 1.31% ID/g at 4 h pi) by increasing the NeoBOMB1 dose from 10 pmol to 200 pmol, whereas tumor uptake remained unaffected. Notably, tumor values did not decline from 1 to 24 h pi; Conclusions: [67Ga]NeoBOMB1 can successfully target GRPR-positive breast cancer in animals with excellent prospects for clinical translation