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Pharmaceuticals (Basel, Switzerland) Feb 2023The simultaneous drug delivery efficiency of a co-loaded single-carrier system of docetaxel (DTX)- and tariquidar (TRQ)-loaded nanostructured lipid carrier (NLC)...
The simultaneous drug delivery efficiency of a co-loaded single-carrier system of docetaxel (DTX)- and tariquidar (TRQ)-loaded nanostructured lipid carrier (NLC) functionalized with PEG and RIPL peptide (PRN) (D^T-PRN) was compared with that of a physically mixed dual-carrier system of DTX-loaded PRN (D-PRN) and TRQ-loaded PRN (T-PRN) to overcome DTX mono-administration-induced multidrug resistance. NLC samples were prepared using the solvent emulsification evaporation technique and showed homogeneous spherical morphology, with nano-sized dispersion (<220 nm) and zeta potential values of -15 to -7 mV. DTX and/or TRQ was successfully encapsulated in NLC samples (>95% encapsulation efficiency and 73-78 µg/mg drug loading). In vitro cytotoxicity was concentration-dependent; D^T-PRN exhibited the highest MDR reversal efficiency, with the lowest combination index value, and increased the cytotoxicity and apoptosis in MCF7/ADR cells by inducing cell-cycle arrest in the G2/M phase. A competitive cellular uptake assay using fluorescent probes showed that, compared to the dual nanocarrier system, the single nanocarrier system exhibited better intracellular delivery efficiency of multiple probes to target cells. In the MCF7/ADR-xenografted mouse models, simultaneous DTX and TRQ delivery using D^T-PRN significantly suppressed tumor growth as compared to other treatments. A single co-loaded system for PRN-based co-delivery of DTX/TRQ (1:1, /) constitutes a promising therapeutic strategy for drug-resistant breast cancer cells.
PubMed: 36986449
DOI: 10.3390/ph16030349 -
Journal of Controlled Release :... Feb 2022Several drugs approved for inhalation for the treatment of pulmonary diseases are substrates of the adenosine triphosphate-binding cassette (ABC) transporter...
Several drugs approved for inhalation for the treatment of pulmonary diseases are substrates of the adenosine triphosphate-binding cassette (ABC) transporter P-glycoprotein (P-gp). P-gp is expressed in the apical membrane of pulmonary epithelial cells and could play a role in modulating the pulmonary absorption and distribution of inhaled drugs, thereby potentially contributing to variability in therapeutic response and/or systemic side effects. We developed a new in vivo experimental approach to assess the functional impact of P-gp on the pulmonary delivery of inhaled drugs in rats. By using positron emission tomography (PET) imaging, we measured the intrapulmonary pharmacokinetics of the model P-gp substrates (R)-[C]verapamil ([C]VPM) and [C]-N-desmethyl-loperamide ([C]dLOP) administered by intratracheal aerosolization in three rat groups: wild-type, Abcb1a/b and wild-type treated with the P-gp inhibitor tariquidar. Lung exposure (AUC) to [C]VPM was 64% and 50% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b rats, respectively, compared to untreated wild-type rats. For [C]dLOP, AUC was 59% and 34% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b rats, respectively. Our results show that P-gp can affect the pulmonary disposition of inhaled P-gp substrates, whereby a decrease in P-gp activity may lead to lower lung exposure and potentially to a decrease in therapeutic efficacy. Our study highlights the potential of PET imaging with intratracheally aerosolized radiotracers to assess the impact of membrane transporters on pulmonary drug delivery, in rodents and potentially also in humans.
Topics: ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Blood-Brain Barrier; Lung; Positron-Emission Tomography; Rats
PubMed: 34971693
DOI: 10.1016/j.jconrel.2021.12.031 -
European Journal of Drug Metabolism and... Oct 2018P-glycoprotein (P-gp), a transmembrane transporter expressed at the blood-brain barrier, restricts the distribution of diverse central nervous system-targeted drugs from... (Comparative Study)
Comparative Study
BACKGROUND AND OBJECTIVE
P-glycoprotein (P-gp), a transmembrane transporter expressed at the blood-brain barrier, restricts the distribution of diverse central nervous system-targeted drugs from blood into brain, reducing their therapeutic efficacy. The third-generation P-gp inhibitor tariquidar (XR9576) was shown to enhance brain distribution of P-gp substrate drugs in humans. Oral bioavailability of tariquidar was found to be low in humans requiring the compound to be administered intravenously, which hinders a broader clinical use. The objective of the present study was to investigate the plasma pharmacokinetics of tariquidar in rats after single intravenous, oral, and intraperitoneal administration.
METHODS
Two different tariquidar formulations (A and B) were used, both at a dosage of 15 mg/kg, respectively. Formulation A was a solution and formulation B was a microemulsion which was previously shown to improve the oral bioavailability of the structurally related P-gp inhibitor elacridar in mice.
RESULTS
In contrast to human data, the present study found a high bioavailability of tariquidar in rats after oral dosing. Oral bioavailability was significantly higher (p = 0.032) for formulation B (86.3%) than for formulation A (71.6%). After intraperitoneal dosing bioavailability was 91.4% for formulation A and 99.6% for formulation B.
CONCLUSION
The present findings extend the available information on tariquidar and provide a basis for future studies involving oral administration of this compound.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Administration, Oral; Animals; Biological Availability; Drug Compounding; Injections, Intraperitoneal; Injections, Intravenous; Male; Models, Biological; Quinolines; Rats, Sprague-Dawley
PubMed: 29616423
DOI: 10.1007/s13318-018-0474-x -
Scientific Reports Nov 2022P-glycoprotein (Pgp) is the most studied ATP-binding cassette (ABC) efflux transporter and contributes to chemoresistance. A few tracers have been developed to detect...
P-glycoprotein (Pgp) is the most studied ATP-binding cassette (ABC) efflux transporter and contributes to chemoresistance. A few tracers have been developed to detect the in-vivo status of chemoresistance using positron emission tomography (PET) imaging. In our study, we have synthesized labeled AVT-011 with fluorine-18 (F) followed by in-vitro and in-vivo analysis. Tosylate AVT-011 precursor was synthesized and characterized by H-NMR and C-NMR. AVT-011 was labeled with F using the nucleophilic substitution method, and a standard set of quality control was performed. The specificity for Pgp was tested in U87MG cells with and without an inhibitor (tariquidar). The biodistribution and in-vivo stability were tested in the small animals (mice). The biodistribution data of [F]-AVT-011 was extracted from the PET-CT imaging of breast cancer patients (n = 6). The precursor was synthesized with 36 ± 4% yield and 97 ± 2% purity. The labeling was more than 95% with a 42 ± 2% yield, as evaluated by Radio-HPLC. The cell-binding assay showed a specificity of the tracer for Pgp as the uptake increased by twice after blocking the Pgp receptors. The radiotracer showed a hepatorenal excretion pathway for clearance in an animal study. The uptake was higher in the liver, lungs, spleen, and heart at 15 min and decreased at 60 min. The patients' distribution showed similar uptake patterns as observed in the small animals. [F]AVT-011 was characterized successfully with high radiochemical purity and yield. The in-vitro and in-vivo studies proved its specificity for Pgp and safe for patient use.
Topics: Animals; Mice; Positron Emission Tomography Computed Tomography; Tissue Distribution; Drug Resistance, Neoplasm; Fluorine Radioisotopes; Positron-Emission Tomography; Radiopharmaceuticals; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP-Binding Cassette Transporters
PubMed: 36329151
DOI: 10.1038/s41598-022-22930-6 -
ACS Chemical Neuroscience Feb 2022The homo-pentameric alpha 7 receptor is one of the major types of neuronal nicotinic acetylcholine receptors (α7-nAChRs) related to cognition, memory formation, and...
The homo-pentameric alpha 7 receptor is one of the major types of neuronal nicotinic acetylcholine receptors (α7-nAChRs) related to cognition, memory formation, and attention processing. The mapping of α7-nAChRs by PET pulls a lot of attention to realize the mechanism and development of CNS diseases such as AD, PD, and schizophrenia. Several PET radioligands have been explored for the detection of the α7-nAChR. F-ASEM is the most functional for quantification of α7-nAChRs in the human brain. The first aim of this study was to initially use results from in silico and machine learning techniques to prescreen and predict the binding energy and other properties of ASEM analogues and to interpret these properties in terms of atomic structures using F-ASEM as a lead structure, and second, to label some selected candidates with carbon-11/hydrogen-3 (C/H) and to evaluate the binding properties and using the labeled candidates. In silico predictions are obtained from perturbation free-energy calculations preceded by molecular docking, molecular dynamics, and metadynamics simulations. Machine learning techniques have been applied for the BBB and P-gp-binding properties. Six analogues of ASEM were labeled with C, and three of them were additionally labeled with H. Binding properties were further evaluated using autoradiography (ARG) and PET measurements in non-human primates (NHPs). Radiometabolites were measured in NHP plasma. All six compounds were successfully synthesized. Evaluation with ARG showed that C-Kln83 was preferably binding to the α7-nAChR. Competition studies showed that 80% of the total binding was displaced. Further ARG studies using H-KIn-83 replicated the preliminary results. In the NHP PET study, the distribution pattern of C-KIn-83 was similar to other α7 nAChR PET tracers. The brain uptake was relatively low and increased by the administration of tariquidar, indicating a substrate of P-gp. The ASEM blocking study showed that C-KIn-83 specifically binds to α7 nAChRs. Preliminary evaluation of KIn-83 by ARG with both C and H and evaluation in NHP showed favorable properties for selectively imaging α7-nAChRs, despite a relatively low brain uptake.
Topics: Animals; Azabicyclo Compounds; Cyclic S-Oxides; Molecular Docking Simulation; Positron-Emission Tomography; Receptors, Nicotinic; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 35020351
DOI: 10.1021/acschemneuro.1c00730 -
Journal of Molecular Biology Jun 2021ABCG2 is an ATP-binding cassette (ABC) transporter whose function affects the pharmacokinetics of drugs and contributes to multidrug resistance of cancer cells. While...
ABCG2 is an ATP-binding cassette (ABC) transporter whose function affects the pharmacokinetics of drugs and contributes to multidrug resistance of cancer cells. While its interaction with the endogenous substrate estrone-3-sulfate (ES) has been elucidated at a structural level, the recognition and recruitment of exogenous compounds is not understood at sufficiently high resolution. Here we present three cryo-EM structures of nanodisc-reconstituted, human ABCG2 bound to anticancer drugs tariquidar, topotecan and mitoxantrone. To enable structural insight at high resolution, we used Fab fragments of the ABCG2-specific monoclonal antibody 5D3, which binds to the external side of the transporter but does not interfere with drug-induced stimulation of ATPase activity. We observed that the binding pocket of ABCG2 can accommodate a single tariquidar molecule in a C-shaped conformation, similar to one of the two tariquidar molecules bound to ABCB1, where tariquidar acts as an inhibitor. We also found single copies of topotecan and mitoxantrone bound between key phenylalanine residues. Mutagenesis experiments confirmed the functional importance of two residues in the binding pocket, F439 and N436. Using 3D variability analyses, we found a correlation between substrate binding and reduced dynamics of the nucleotide binding domains (NBDs), suggesting a structural explanation for drug-induced ATPase stimulation. Our findings provide additional insight into how ABCG2 differentiates between inhibitors and substrates and may guide a rational design of new modulators and substrates.
Topics: ATP Binding Cassette Transporter, Subfamily G, Member 2; Binding Sites; Biological Transport; Humans; Models, Molecular; Pharmaceutical Preparations; Structure-Activity Relationship; Substrate Specificity
PubMed: 33838147
DOI: 10.1016/j.jmb.2021.166980 -
International Journal of Molecular... May 2023Acquired chemoresistance during chemotherapy, often accompanied by cross- and multi-resistance, limits therapeutic outcomes and leads to recurrence. In order to create...
Acquired chemoresistance during chemotherapy, often accompanied by cross- and multi-resistance, limits therapeutic outcomes and leads to recurrence. In order to create in vitro model systems to understand acquired doxorubicin-resistance, we generated doxorubicin-resistant sublines of canine prostate adenocarcinoma and urothelial cell carcinoma cell lines. Chemoresistance to doxorubicin, cross-resistance to carboplatin, and the reversibility of the acquired resistance by the specific MDR1-inhibitor tariquidar were quantified in metabolic assays. Resistance mechanisms were characterized by expression of the efflux transporters MDR1 and RALBP1, as well as the molecular target of doxorubicin, TOP2A, with qPCR and Western blotting. Six out of nine cell lines established stable resistance to 2 µM doxorubicin. Drug efflux via massive MDR1 overexpression was identified as common, driving resistance mechanism in all sublines. MDR1 inhibition with tariquidar extensively reduced or reversed the acquired, and also partly the parental resistance. Three cell lines developed additional, non-MDR1-dependent resistance. RALBP1 was upregulated in one resistant subline at the protein level, while TOP2A expression was not altered. Combination therapies aiming to inhibit MDR1 activity can now be screened for synergistic effects using our resistant sublines. Nevertheless, detailed resistance mechanisms and maintained molecular target expression in the resistant sublines are still to be examined.
Topics: Male; Animals; Dogs; Prostate; ATP Binding Cassette Transporter, Subfamily B, Member 1; Doxorubicin; Cell Line; Urinary Bladder Neoplasms; Drug Resistance, Neoplasm; Cell Line, Tumor
PubMed: 37175843
DOI: 10.3390/ijms24098136 -
Journal of Controlled Release :... Jul 2022The Blood-Brain Barrier P-glycoprotein (P-gp) function can be altered in several neurodegenerative diseases and due to the administration of different drugs which may...
The Blood-Brain Barrier P-glycoprotein (P-gp) function can be altered in several neurodegenerative diseases and due to the administration of different drugs which may cause alterations in drug concentrations and consequently lead to a reduced effectiveness or increased side-effects. The novel PET radiotracer [F]MC225 is a weak P-gp substrate that may show higher sensitivity to detect small changes in P-gp function than previously developed radiotracers. This study explores the sensitivity of [F]MC225 to measure the dose-dependent effect of P-gp inhibitor tariquidar. Twenty-three rats were intravenously injected with different doses of tariquidar ranging from 0.75 to 12 mg/kg, 30-min before the dynamic [F]MC225-PET acquisition with arterial sampling. Tissue and blood data were fitted to a 1-Tissue-Compartment-Model to obtain influx constant K and distribution volume V, which allow the estimation of P-gp function. ANOVA and post-hoc analyses of K values showed significant differences between controls and groups with tariquidar doses >3 mg/kg; while applying V the analyses showed significant differences between controls and groups with tariquidar doses >6 mg/kg. Dose-response curves were fitted using different models. The four-parameter logistic sigmoidal curve provided the best fit for K and V data. Half-maximal inhibitory doses (ID) were 2.23 mg/kg (95%CI: 1.669-2.783) and 2.93 mg/kg (95%CI: 1.135-3.651), calculated with K or V values respectively. According to the dose-response fit, differences in [F]MC225-K values could be detected at tariquidar doses ranging from 1.37 to 3.25 mg/kg. Our findings showed that small changes in the P-gp function, caused by low doses of tariquidar, could be detected by [F]MC225-K values, which confirms the high sensitivity of the radiotracer. The results suggest that [F]MC225 may allow the quantification of moderate P-gp impairments, which may allow the detection of P-gp dysfunctions at the early stages of a disease and potential transporter-mediated drug-drug interactions.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Biological Transport; Blood-Brain Barrier; Positron-Emission Tomography; Rats
PubMed: 35588934
DOI: 10.1016/j.jconrel.2022.05.026 -
Journal of Nuclear Medicine : Official... Jan 2015The permeability-glycoprotein (P-gp) efflux transporter is densely expressed at the blood-brain barrier, and its resultant spare capacity requires substantial blockade... (Clinical Trial)
Clinical Trial
UNLABELLED
The permeability-glycoprotein (P-gp) efflux transporter is densely expressed at the blood-brain barrier, and its resultant spare capacity requires substantial blockade to increase the uptake of avid substrates, blunting the ability of investigators to measure clinically meaningful alterations in P-gp function. This study, conducted in humans, examined 2 P-gp inhibitors (tariquidar, a known inhibitor, and disulfiram, a putative inhibitor) and 2 routes of administration (intravenous and oral) to maximally increase brain uptake of the avid and selective P-gp substrate (11)C-N-desmethyl-loperamide (dLop) while avoiding side effects associated with high doses of tariquidar.
METHODS
Forty-two (11)C-dLop PET scans were obtained from 37 healthy volunteers. PET was performed with (11)C-dLop under the following 5 conditions: injected under baseline conditions without P-gp inhibition, injected 1 h after intravenous tariquidar infusion, injected during intravenous tariquidar infusion, injected after oral tariquidar, and injected after disulfiram. (11)C-dLop uptake was quantified with kinetic modeling using metabolite-corrected arterial input function or by measuring the area under the time-activity curve in the brain from 10 to 30 min.
RESULTS
Neither oral tariquidar nor oral disulfiram increased brain uptake of (11)C-dLop. Injecting (11)C-dLop during tariquidar infusion, when plasma tariquidar concentrations reach their peak, resulted in a brain uptake of the radioligand approximately 5-fold greater than baseline. Brain uptake was similar with 2 and 4 mg of intravenous tariquidar per kilogram; however, the lower dose was better tolerated. Injecting (11)C-dLop after tariquidar infusion also increased brain uptake, though higher doses (up to 6 mg/kg) were required. Brain uptake of (11)C-dLop increased fairly linearly with increasing plasma tariquidar concentrations, but we are uncertain whether maximal uptake was achieved.
CONCLUSION
We sought to increase the dynamic range of P-gp function measured after blockade. Performing (11)C-dLop PET during peak plasma concentrations of tariquidar, achieved with concurrent administration of intravenous tariquidar, resulted in greater P-gp inhibition at the human blood-brain barrier than delayed administration and allowed the use of a lower, more tolerable dose of tariquidar. On the basis of prior monkey studies, we suspect that plasma concentrations of tariquidar did not fully block P-gp; however, higher doses of tariquidar would likely be associated with unacceptable side effects.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Administration, Intravenous; Administration, Oral; Adult; Biological Transport; Blood-Brain Barrier; Dose-Response Relationship, Drug; Female; Humans; Loperamide; Male; Permeability; Positron-Emission Tomography; Quinolines; Safety
PubMed: 25500831
DOI: 10.2967/jnumed.114.146894 -
European Journal of Nuclear Medicine... Jan 2012One important mechanism for chemoresistance of tumours is overexpression of the adenosine triphosphate-binding cassette transporter P-glycoprotein (Pgp). Pgp reduces... (Comparative Study)
Comparative Study
PURPOSE
One important mechanism for chemoresistance of tumours is overexpression of the adenosine triphosphate-binding cassette transporter P-glycoprotein (Pgp). Pgp reduces intracellular concentrations of chemotherapeutic drugs. The aim of this study was to compare the suitability of the radiolabelled Pgp inhibitors [(11)C]tariquidar and [(11)C]elacridar with the Pgp substrate radiotracer (R)-[(11)C]verapamil for discriminating tumours expressing low and high levels of Pgp using small-animal PET imaging in a murine breast cancer model.
METHODS
Murine mammary carcinoma cells (EMT6) were continuously exposed to doxorubicin to generate a Pgp-overexpressing, doxorubicin-resistant cell line (EMT6AR1.0 cells). Both cell lines were subcutaneously injected into female athymic nude mice. One week after implantation, animals underwent PET scans with [(11)C]tariquidar (n = 7), [(11)C]elacridar (n = 6) and (R)-[(11)C]verapamil (n = 7), before and after administration of unlabelled tariquidar (15 mg/kg). Pgp expression in tumour grafts was evaluated by Western blotting.
RESULTS
[(11)C]Tariquidar showed significantly higher retention in Pgp-overexpressing EMT6AR1.0 compared with EMT6 tumours: the mean ± SD areas under the time-activity curves in scan 1 from time 0 to 60 min (AUC(0-60)) were 38.8 ± 2.2 min and 25.0 ± 5.3 min (p = 0.016, Wilcoxon matched pairs test). [(11)C]Elacridar and (R)-[(11)C]verapamil were not able to discriminate Pgp expression in tumour models. Following administration of unlabelled tariquidar, both EMT6Ar1.0 and EMT6 tumours showed increases in uptake of [(11)C]tariquidar, [(11)C]elacridar and (R)-[(11)C]verapamil.
CONCLUSION
Among the tested radiotracers, [(11)C]tariquidar performed best in discriminating tumours expressing high and low levels of Pgp. Therefore [(11)C]tariquidar merits further investigation as a PET tracer to assess Pgp expression levels in solid tumours.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Acridines; Animals; Biological Transport; Breast Neoplasms; Carbon Radioisotopes; Cell Line, Tumor; Disease Models, Animal; Doxorubicin; Drug Resistance, Neoplasm; Feasibility Studies; Female; Gene Expression Regulation, Neoplastic; Mice; Phenotype; Positron-Emission Tomography; Quinolines; Tetrahydroisoquinolines; Verapamil
PubMed: 21983837
DOI: 10.1007/s00259-011-1941-7