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Introduction: Biorthogonal pretargeted imaging using the inverse electron demand Diels Alder (IEDDA) reaction between tetrazine (Tz) and trans-cyclooctene (TCO) is one of the most attractive strategies in molecular imaging. It allows the use of short-lived radioisotopes such as fluorine-18 for imaging of long circulating vectors with improved imaging contrast and reduced radiation dose. Here we aim to develop a novel F-18-labeled transcyclooctene (TCO) with improved metabolic stability and assess its potential usefulness in a pretargeted PET imaging approach. Methods: We have synthetized a new TCO-analogue containing a 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) chelator, allowing radiolabeling by chelation with aluminum fluoride (Al[F-18]F). Stability and pharmacokinetic profile of Al[(HF)-H-18-NOTA-TCO ([F-18]MICA-205) were evaluated in healthy animals at different timepoints after injection of the radiotracer. To assess the potential use of this new PET tracer for tumor targeting, in vivo pretargeted PET imaging was performed in LS174T tumor-bearing mice pre-treated with a tetrazine-modified anti-TAG-72 monoclonal antibody (CC49). Results: The radiotracer was obtained with a radiochemical yield (RCY) of 12.8 +/- 2.8% and a radiochemical purity (RCP) of >= 95%. It also showed a promising in vivo stability with 51.9 +/- 5.16% of radiotracer remaining intact after 1 h. The biodistribution in healthy mice demonstrated mixed hepatobiliary and renal clearance, with a rapid blood clearance and low uptake in other tissues. The low bone uptake indicated lack of tracer defluorination. Interestingly, a pretargeted PET imaging experiment showed a significantly increased radiotracer uptake (0.67 +/- 0.16%ID/g, p < 0.001) in the tumors of mice pre-treated with CC49-tetrazine compared to the CC49 alone (0.16 0.08%ID/g). Conclusions: [189 MICA-205 represents a large improvement in in vivo metabolic stability compared to previous reported F-18-labeled TCOs, allowing a clear visualization of tumor tissue in a small-animal pretargeted PET imaging experiment. Despite the favorable in vivo stability and image contrast obtained with [F-18]MICA-205, the development of next-generation derivatives with increased absolute tumor uptake is warranted for future pretargeting applications. (C) 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

9 p.-5 fig.-2 tab., We report the evaluation of 265 compounds from a PDE-focused library for their antischistosomal activity, assessed in vitro using Schistosoma mansoni. Of the tested compounds, 171 (64%) displayed selective in vitro activity, with 16 causing worm hypermotility/spastic contractions and 41 inducing various degrees of worm killing at 100 μM, with the surviving worms displaying sluggish movement, worm unpairing and complete absence of eggs. The compounds that did not affect worm viability (n=72) induced a complete cessation of ovipositing. 82% of the compounds had an impact on male worms whereas female worms were barely affected. In vivo evaluation in S. mansoni-infected mice with the in vitro ‘hit’ NPD-0274 at 20 mg/kg/day orally for 5 days resulted in worm burden reductions of 29% and intestinal tissue egg load reduction of 35% at 10 days posttreatment.Combination of praziquantel (PZQ) at 10 mg/kg/day for 5 days with NPD-0274 or NPD-0298 resulted in significantly higher worm killing than PZQ alone, as well as a reduction in intestinal tissue egg load, disappearance of immature eggs and an increase in the number of dead eggs., This work is part of the PDE4NPD consortium supported by Framework Program 7 of the European Commission No: 602666.Funding from RICET/FEDER funds (RD16/0027/0010), and the Ministry of Education, Culture and Sport (MECD) of Spain (Grant FPU15/1465 to V. S.-P.) is also acknowledged. Y. Z. was supported by a grant of the Chinese Science Council; A. R. B. and I. J. P. dE. were supported by the Netherlands Science Foundation.

Human African trypanosomiasis is causing thousands of deaths every year in the rural areas of sub-saharan Africa. There is a high unmet medical need since the approved drugs are poorly efficacious, show considerable toxicity and are not easy to administer. This work describes the optimization of the pharmacokinetic properties of a previously published family of triazine lead compounds. One compound (35 (UAMC-03011)) with potent anti-trypanosomal activity and no cytotoxicity was selected for further study because of its good microsomal stability and high selectivity for Trypanosoma brucei over a panel including Trypanosoma cruzi, L.eishmania infantum, and Plasmodium falciparum. In vivo pharmacokinetic parameters were determined and the compound was studied in an acute in vivo mouse disease model. One of the important learnings of this study was that the rate of trypanocidal activity is an important parameter during the lead optimization process.

The synthesis and in vitro properties of six analogues of the selective glucocorticoid receptor (GR) agonist GSK866, bearing a warhead for covalent linkage to the glucocorticoid receptor, is described.

The purpose of this work was to design and evaluate a vaginal film delivery system for UAMC01398, a novel non-nucleoside reverse transcriptase inhibitor currently under investigation for use as an anti-HIV microbicide. UAMC01398 (1 mg) films consisting of hydroxypropylmethylcellulose (HPMC) and polyethylene glycol 400 (PEG400) in different ratios were prepared by solvent evaporation. Based on its flexibility, softness and translucent appearance, the 30% PEG400 and 70% HPMC containing film was selected for further assessment. The vaginal film formulation was fast-dissolving (

In this study, we investigated the potential of supersaturation for the formulation of the poorly water-soluble microbicide dapivirine (DPV) in an aqueous vaginal gel in order to enhance its vaginal tissue uptake. Different excipients such as hydroxypropylmethylcellulose, polyethylene glycol 1000, and cyclodextrins were evaluated for their ability to inhibit precipitation of supersaturated DPV in the formulation vehicle as such as well as in biorelevant media. In vitro permeation assessment across HEC-1A cell layers demonstrated an enhanced DPV flux from supersaturated gels compared with suspension gels. The best performing supersaturated gel containing 500 M DPV (supersaturation degree of 4) in the presence of sulfobutyl ether-beta-cyclodextrin (2.5%) appeared to be stable for at least 3 months. In addition, the gel generated a significant increase in vaginal drug uptake in rabbits as compared with suspension gels. We conclude that supersaturation is a possible strategy to enhance the vaginal concentration of hydrophobic microbicides, thereby increasing permeation into the vaginal submucosa. (c) 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3696-3703, 2014

The presence of a structural recognition motif for the nucleoside P2 transporter in a library of pyrimidine and triazine non-nucleoside HIV-1 reverse transcriptase inhibitors, prompted for the evaluation of antitrypanosomal activity. It was demonstrated that the structureactivity relationship for anti-HIV and antitrypanosomal activity was different. Optimization in the diaryl triazine series led to 6-(mesityloxy)-N2-phenyl-1,3,5-triazine-2,4-diamine (69), a compound with potent in vitro and moderate in vivo antitrypanosomal activity.

Introduction: The tetrazine-trans-cylooctene cycloaddition using radiolabeled tetrazine or radiolabeled transcyclooctene (TCO) has been reported to be a very fast, selective and bioorthogonal reaction that could be useful for in vivo radiolabeling of molecules. We wanted to evaluate the in vivo biodistribution profile and brain uptake of F-18-labeled TCO ([F-18]TCO) to assess its potential for pre-targeted imaging in the brain. Methods: We evaluated the in vivo behavior of[F-18]TCO via an ex vivo biodistribution study complemented by in vivo mu PET imaging at 5, 30, 60, 90, 120 and 240 mm post tracer injection. An in vivo metabolite study was performed at 5 min, 30 mm and 120 min post [F-18]TCO injection by RP-HPLC analysis of plasma and brain extracts. Incubation with human liver microsomes was performed to further evaluate the metabolite profile of the tracer. Results: mu PET imaging and ex-vivo biodistribution revealed an high initial brain uptake of [F-18]TCO (3.8%ID/g at 5 min pi) followed by a washout to 3.0%ID/g at 30 min pi. Subsequently the brain uptake increased again to 3.7%ID/g at 120 min pi followed by a slow washout until 240 min pi (2.9%ID/g). Autoradiography confirmed homogenous brain uptake. On the WET images bone uptake became gradually visible after 120 mm pi and was clearly visible at 240 mm pi. The metabolite study revealed a fast metabolization of [F-18]TCO in plasma and brain into three main polar radiometabolites. Conclusions: Although [F-18]TCO has previously been described to be a useful tracer for radiolabeling of tetrazine modified targeting molecules, our study indicates that its utility for in vivo chemistry and pretargeted imaging will be limited. Although [F-18]TCO clearly enters the brain, it is quickly metabolized with a non-specific accumulation of radioactivity in the brain and bone. (c) 2014 Elsevier Inc. All rights reserved.

Introduction The urokinase plasminogen activator (uPA) system is a proteolytic cascade involved in tumor invasion and metastasis. uPA and its inhibitor PAI-1 are described as biomarkers for breast cancer with the highest level of evidence. The present study describes the synthesis and first in vivo application of an activity based uPA PET-probe. Methods Based on the design of a small irreversible and selective uPA-inhibitor we developed a 18 F-labeled activity based probe for uPA imaging. Human uPA expressing MDA-MB-231-luc2-GFP cells were inoculated in the mammary fat pads of nude mice and treated with the probe once tumors reached a volume of 150 mm3. Scans were performed at 0.25, 0.75, 1.5, 4 and 6 h post injection. To evaluate tumor uptake in vivo and ex vivo data were gathered. Biodistribution data of the organs and tissues of interest were collected at all time points. Due to a relatively low tumor uptake, probe stability was further evaluated. Results The uPA targeting PET tracer was produced in high purity and with good specific radioactivity. In vivo PET data showed a maximum tumor uptake of 2,51 ± 0,32 %ID/g at 4 h p.i. A significant correlation between in vivo and ex vivo tumor uptake calculation was found (R = 0.75; p < 0.01). Due to a high blood signal at all time points, probe stability was further examined revealing high plasma protein binding and low plasma stability. Conclusions In vivo and ex vivo results clearly demonstrate that uPA expressing tumors can be detected with non-invasive PET imaging. Stability tests suggest that further optimization is needed to provide a better tumor-to-background contrast.

The T cell activation Ag CD26/dipeptidylpeptidase IV (DPP IV) combines co-stimulatory and enzymatic properties. Catalytically, it functions as an exopeptidase, modulating biological activity of key chemokines and peptides. Here we investigated the effect of organ-specific inhibition of DPP IV catalytic activity on ischemia/reperfusion injury after extended ischemia in the mouse model of orthotopic single lung transplantation. C57BL/6 mice were syngeneically, transplanted, grafts were perfused and stored in Perfadex with (treated) or without (control) a DPP IV enzymatic activity inhibitor (AB192). Transplantation was performed after 18 h cold ischemia time; following 2-h reperfusion, grafts were analyzed for oxygenation, thiobarbituric acid-reactive substances, histomorphology, and immunohistochemistry was performed for leukocyte Ag 6, myeloperoxidase, hemoxygenase 1, vasoactive intestinal protein (VIP), and real-time PCR for VIP. Treatment with the DPP IV inhibitor AB192 resulted in significant improvement of gas exchange, less lipid oxidation, preservation of parenchymal ultrastructure, reduced neutrophil infiltration, reduced myeloperoxidase expression, increased hemoxygenase 1 expression, pronounced expression of VIP in alveolar macrophages and increased mRNA expression of VIP. Inhibition of intragraft DPP IV catalytic activity with AB192 strikingly ameliorates ischemia/reperfusion injury after extended ischemia. Furthermore, preservation of endogenous intragraft VIP levels correlate with maintaining lung function and structural integrity.

Metacaspase (MCA) is an important enzyme in Trypanosoma brucei, absent from humans and differing significantly from the orthologous human caspases. Therefore MCA constitutes a new attractive drug target for antiparasitic chemotherapeutics, which needs further characterization to support the discovery of innovative drug candidates. A first series of inhibitors has been prepared on the basis of known substrate specificity and the predicted catalytic mechanism of the enzyme. In this Letter we present the first inhibitors of TbMCA2 with low micromolar enzymatic and antiparasitic activity in vitro combined with low cytotoxicity.

The aim of present study was to examine whether cationic Eudragit® containing poly(lactide-co-glycolide) (PLGA) nanoparticles can adhere to Pseudomonas aeruginosa and Staphylococcus aureus. In order to prepare fluorescent nanoparticles, fluorescein was covalently coupled to PLGA. Fluorescent PLGA and Eudragit®/PLGA nanoparticles were prepared by w/o/w emulsification solvent evaporation. Particle size and zeta potential of the nanoparticles were measured. Nanoparticles were incubated for a short time with P. aeruginosa and S. aureus followed by measurement of the size of nanoparticles and of P. aeruginosa and S. aureus with and without adherent nanoparticles. Flow cytometric measurements were performed to detect the attachment of particles to microorganisms. Eudragit® containing nanoparticles possessed a positive zeta potential, while PLGA nanoparticles were negatively charged. Following adsorption of Eudragit® containing nanoparticles, a size increase for P. aeruginosa was observed. Flow cytometric analyses confirmed that Eudragit® containing particles showed stronger interactions with the test organisms than PLGA nanoparticles. Adhesion of particles was more pronounced for P. aeruginosa than for S. aureus. Cationic Eudragit® containing nanoparticles showed better adhesion to microorganisms than anionic PLGA nanoparticles, which is probably due to enhanced electrostatic interactions.

Background CD26/DPP IV is a T-cell-membrane protein that cleaves dipeptides from extracellular peptides. Inhibition of its enzymatic activity using Pro-Pro-diphenylphosphonate derivatives has been shown to abrogate acute and accelerated rejection in models of cardiac and pulmonary allotransplantation. Here we investigated the effects of enzymatic DPP IV inhibition on ischemia/reperfusion (I/R) injury after extended ischemia before pulmonary transplantation. Methods A syngeneic rat orthotopic left-lung transplantation model was used. Group I donor lungs (controls) were flushed and preserved in Perfadex for 18 hours at 4°C and then transplanted and reperfused for 2 hours. Group II grafts were perfused with and stored in Perfadex + 25 μmol/liter AB192 [bis(4-acetamidophenyl) 1-( S )-prolylpyrrolidine-2( R , S )-phosphonate]. Group III lungs were perfused with Perfadex + AB192, and stored in Perfadex. After 2-hour reperfusion, oxygenation, peak airway pressure (PawP), graft wet/dry (W/D) weight ratio, myeloperoxidase activity, thiobarbituric acid–reactive substances, graft specific DPP IV enzymatic activities and histomorphology were analyzed. Results AB192 perfusion significantly reduced DPP IV intragraft enzymatic activity in Groups II and III. Compared with controls, transplants from Groups II and III showed significantly improved oxygenation capacity, PawP and W/D weight ratio, with lower intragraft lipid peroxidation; and preserved histologic structure. Conclusions Targeting intragraft DPP IV enzymatic activity attenuated post-transplantation I/R injury and preserved early graft function after extended ischemia.

The influence of the P1 amino acid on the substrate selectivity, the catalytic parameters K(m) and k(cat), of carboxypeptidase M (CPM) (E.C. 3.4.17.12) was systematically studied using a series of benzoyl-Xaa-Arg substrates. CPM had the highest catalytic efficiency (k(cat)/K(m)) for substrates with Met, Ala and aromatic amino acids in the penultimate position and the lowest with amino acids with branched side-chains. Substrates with Pro in P1 were not cleaved in similar conditions. The P1 substrate preference of CPM differed from that of two other members of the carboxypeptidase family, CPN (CPN/CPE subfamily) and CPB (CPA/CPB subfamily). Aromatic P1 residues discriminated most between CPM and CPN. The type of P2 residue also influenced the k(cat) and K(m) of CPM. Extending the substrate up to P7 had little effect on the catalytic parameters. The substrates were modelled in the active site of CPM. The results indicate that P1-S1 interactions play a role in substrate binding and turn-over.

CD26 is a T-cell co-stimulator, and interacts with adenosine deaminase, human immunodeficiency virus (HIV) Tat-1 protein and extracellular matrix. It possesses dipeptidylpeptidase IV (DPP IV) catalytic activity, which is linked to its co-stimulatory efficacy. We investigated the effect of specific DPP IV systemic activity inhibition on acute pulmonary rejection.Rat single-lung transplantation (Tx) was performed (LBNF1/LEW donor/recipient) in two groups (n = 12). Group I (n = 6) received daily treatment with a Pro-Pro-diphenylphosphonate derivative (AB197), and Group II served as an untreated control. At Day 5 post-Tx, ventilatory parameters, cytotoxicity and mixed lymphocyte reaction were analyzed and staining for ISHLT rejection grade and proliferating cell nuclear antigen (PCNA) was performed.Treatment with AB192 abrogated acute rejection and preserved pulmonary function up to Day 5 post-Tx for PO2 (Group II: 24.9 +/- 6.9 mm Hg; Group I: 149.5 +/- 24.3 mm Hg; p0.001), PCO2 (Group II: 53.3 +/- 13.6 mm Hg; Group I: 39.0 +/- 9.8 mm Hg; p0.05) and peak airway pressure (Group II: 50.7 +/- 17.2 mm Hg; Group I: 20.2 +/- 10.0 mm Hg; p0.01). Controls showed moderate/severe rejection (ISHLT Grade A2 or 3), grafts from inhibited hosts revealed no/mild rejection (Grade A0 to 2: Group II: 2.8 +/- 0.3; Group I: 1.25 +/- 1.0; p0.005). Proliferating cell nuclear antigen (PCNA) staining of rejection-associated cellular infiltrates showed a significant reduction in positivity in perivascular infiltrates (34 +/- 11.5%; p0.05) and bronchial surface epithelium (31.7 +/- 10.6%; p0.05) in Group I vs Group II (55.9 +/- 8.4% and 57.2 +/- 4.5%).Irreversible enzymatic inhibition of DPP IV has been shown to abrogate acute pulmonary rejection, maintain pulmonary function, and preserve histomorphologic architecture. These results extend earlier findings and illustrate the role of CD26/DPP IV in alloantigen-mediated immune responses.

Dipeptidyl peptidase (DPP) II (E.C. 3.4.14.2) is an intracellular protease that releases, preferably at acidic pH, N-terminal dipeptides from oligopeptides with Pro or Ala in the penultimate position. The natural substrates and the physiological role of DPPII remain unclear. The aim of the present study was to investigate the involvement of DPPII activity in different forms of cell death (apoptosis, necrosis and autophagy) in human leukocytes. We determined specific DPP activities in leukocytes. Compared to other subpopulations of peripheral blood mononuclear cells (PBMC), we observed relatively high DPPII specific activity in monocytic cells, opening new perspectives for further investigation of the DPPII functions. A second intriguing finding was that DPPII specific activity increased during necrosis, whereas induction of apoptosis or autophagy did not affect any of the dipeptidyl peptidase activities. Finally, we showed that inhibition of DPPII (>90%) using the in vitro applicable, highly potent ( K i of 0.082 ± 0.048 nM) and selective DPPII inhibitor UAMC00039, did not induce any form of cell death in leukocytes. These data are of importance for a more precise interpretation of the in vitro and in vivo effects of other dipeptidyl peptidase inhibitors.

The function of prolyl oligopeptidase (PO) has been associated with several disorders of the central nervous system. The purpose of this study was to identify endogenous substrates for recombinant porcine PO in porcine brain. The smaller polypeptides were extracted from total brain homogenates and fractionated by two-dimensional chromatography prior to incubation with PO. Shifts in the mass spectrum between the control and the incubated sample, marked potential substrates. Using MSMS peptide sequencing techniques, we identified several fragments of intracellular proteins as potential substrates, which opens new perspectives for finding the function of PO in the intracellular space.

( E )- and ( Z )-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors were synthesized. A Wadsworth–Horner–Emmons reaction, followed by amide formation and reduction of the amide were used for the construction of the α-fluoro-α,β-unsaturated amine functionality.

CD26/Dipeptidyl peptidase (DPP) IV is an integral membrane protein of lymphocytes that modulates the activities of chemokines, interleukins, and neuropeptides. We investigated the effect of enzymatic DPP IV inhibition on ischemia/reperfusion injury after extended ischemia prior to transplantation. Materials and Methods. We used a syngeneic rat (Lewis) orthotopic left lung transplantation model. In the control group (group I), donor lungs were flushed and preserved in Perfadex for 18 hours at 4°C, then transplanted and reperfused for 2 hours. Group II donor lungs were perfused with and stored in Perfadex +25mol/L AB192 (bis(4-acetamidophenyl) 1-(S)-prolylpyrrolidine-2(R,S)-phosphonate), a small molecular weight DPP IV inhibitor. After 2-hour reperfusion, we measured blood gas, peak airway pressure, and thiobarbituric acid reactive substances. Results. Grafts from group II versus group I showed a significantly increased oxygenation capacity (II: 298.4 ± 87.6 mm Hg vs 120.9 ± 48.0, P

Several acyclic and cyclic dipeptidyl acetals were synthesized. Among these, N-[N-benzyloxycarbonyl-(S)-prolyl]-(S)-prolinal dimethyl acetal 8 was shown to be a potent inhibitor of prolyl endopeptidase.

Oligonucleotides containing acyclic nucleosides with a 3( S ),5-dihydroxypentyl ( 1a–e ) or 4( R )-methoxy-3( S ),5-dihydroxypentyl ( 2a ) side chain were prepared and their hybridization properties as well as their stability towards degradation with snake venom posphodiesterase were studied. Attachment of an acyclic nucleoside at the 3′-end of an oligonucleotide makes it extremely resistant against enzymatic breakdown. Whereas oligonucleotides consisting completely of acyclic 2′-deoxyadenosine analogues ( 1a or 2a ) can still hybridize with an unmodified oligothymidylate, completely modified oligothymidylates or hetero-oligomers do not hybridize with their unmodified complementary oligonucleotide. This can be explained by the favourable enthalpy change on hybridization for the oligomers with adenine bases because of their higher degree of stacking and the ability to form T- A * .T triplets. In base-pairing with the natural DNA-nucleosides (dA,dC,dG,T), the acyclic nucleoside analogues ( 1a–e ) discriminate less compared to the natural 2′-deoxynucleosides. 9-(3( S ),5-Dihydroxypentyl)hypoxanthine shows the least spreading in melting temperature on hybridization with the four natural 2′-deoxynucleosides. Because of their conformational flexibility, acyclic nucleosides can be considered as universal nucleoside for the design of probes with ambiguous positions.

The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine, starting from the well known carbohydrate precursors 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (12 steps) or from tri-O-acetyl-D-glucal (11 steps) is described.