Subject(s)
Coloboma , Optic Disk , Humans , Coloboma/complications , Coloboma/diagnosis , Coloboma/diagnostic imaging , Optic Disk/abnormalities , Optic Disk/diagnostic imaging , Male , Tomography, Optical Coherence , Female , Retinal Diseases/complications , Retinal Diseases/diagnosis , Retinal Diseases/diagnostic imagingABSTRACT
Acute macular neuroretinopathy (AMN) affects the outer retina and is most likely induced by non-inflammatory ischaemia of the retinal deep capillary plexus and choriocapillaris. A man in his early 20s developed Valsalva retinopathy following weightlifting at the gym and presented with blurring of vision in the left eye 1 month after the initial retinal haemorrhages had resolved. A diffuse, purplish, donut-shaped, perifoveal lesion was seen on funduscopy and was well defined by an optical coherence tomography angiography (OCTA) en face image in the left eye. Outer retinal changes on optical coherence tomography (OCT) and a dense co-localised scotoma on a visual field (VF) examination confirmed the diagnosis of AMN, and the patient was started on a tapering dose of oral steroids. Improvement was seen in OCT, OCTA and VF during the 6-month follow-up visit. The use of OCTA en face imaging enabled the accurate identification of the lesion in the affected layers of the retina.
Subject(s)
Retinal Diseases , Tomography, Optical Coherence , Valsalva Maneuver , Humans , Male , Tomography, Optical Coherence/methods , Retinal Diseases/etiology , Retinal Diseases/physiopathology , Retinal Diseases/diagnosis , Retinal Diseases/diagnostic imaging , Fluorescein Angiography/methods , Adult , Macula Lutea/diagnostic imaging , Macula Lutea/pathology , Acute Disease , Scotoma/etiology , Scotoma/physiopathology , Visual AcuityABSTRACT
Toll-like receptor-driven and interleukin-1 (IL-1) receptor-driven inflammation mediated by IL-1 receptor-associated kinase 4 (IRAK4) is involved in the pathophysiology of hidradenitis suppurativa (HS) and atopic dermatitis (AD). KT-474 (SAR444656), an IRAK4 degrader, was studied in a randomized, double-blind, placebo-controlled phase 1 trial where the primary objective was safety and tolerability. Secondary objectives included pharmacokinetics, pharmacodynamics and clinical activity in patients with moderate to severe HS and in patients with moderate to severe AD. KT-474 was administered as a single dose and then daily for 14 d in 105 healthy volunteers (HVs), followed by dosing for 28 d in an open-label cohort of 21 patients. Degradation of IRAK4 was observed in HV blood, with mean reductions after a single dose of ≥93% at 600-1,600 mg and after 14 daily doses of ≥95% at 50-200 mg. In patients, similar IRAK4 degradation was achieved in blood, and IRAK4 was normalized in skin lesions where it was overexpressed relative to HVs. Reduction of disease-relevant inflammatory biomarkers was demonstrated in the blood and skin of patients with HS and patients with AD and was associated with improvement in skin lesions and symptoms. There were no drug-related infections. These results, from what, to our knowledge, is the first published clinical trial using a heterobifunctional degrader, provide initial proof of concept for KT-474 in HS and AD to be further confirmed in larger trials. ClinicalTrials.gov identifier: NCT04772885 .
Subject(s)
Dermatitis, Atopic , Hidradenitis Suppurativa , Humans , Hidradenitis Suppurativa/drug therapy , Dermatitis, Atopic/drug therapy , Interleukin-1 Receptor-Associated Kinases , Treatment Outcome , Skin/pathology , Double-Blind Method , Severity of Illness IndexABSTRACT
Conjugation of oligonucleotide therapeutics, including small interfering RNAs (siRNAs) or antisense oligonucleotides, to N-acetylgalactosamine (GalNAc) ligands has become the primary strategy for hepatocyte-targeted delivery, and with the recent approvals of GIVLAARI (givosiran) for the treatment of acute hepatic porphyria, OXLUMO (lumasiran) for the treatment of primary hyperoxaluria, and Leqvio (inclisiran) for the treatment of hypercholesterolemia, the technology has been well validated clinically. Although much knowledge has been gained over decades of development, there is a paucity of published literature on the drug metabolism and pharmacokinetic properties of GalNAc-siRNA. With this in mind, the goals of this minireview are to provide an aggregate analysis of these nonclinical absorption, distribution, metabolism, and excretion (ADME) data to build confidence on the translation of these properties to human. Upon subcutaneous administration, GalNAc-conjugated siRNAs are quickly distributed to the liver, resulting in plasma pharmacokinetic (PK) properties that reflect rapid elimination through asialoglycoprotein receptor-mediated uptake from circulation into hepatocytes. These studies confirm that liver PK, including half-life and, most importantly, siRNA levels in RNA-induced silencing complex in hepatocytes, are better predictors of pharmacodynamics (PD) than plasma PK. Several in vitro and in vivo nonclinical studies were conducted to characterize the ADME properties of GalNAc-conjugated siRNAs. These studies demonstrate that the PK/PD and ADME properties of GalNAc-conjugated siRNAs are highly conserved across species, are largely predictable, and can be accurately scaled to human, allowing us to identify efficacious and safe clinical dosing regimens in the absence of human liver PK profiles. SIGNIFICANCE STATEMENT: Several nonclinical ADME studies have been conducted in order to provide a comprehensive overview of the disposition and elimination of GalNAc-conjugated siRNAs and the pharmacokinetic/pharmacodynamic translation between species. These studies demonstrate that the ADME properties of GalNAc-conjugated siRNAs are well correlated and predictable across species, building confidence in the ability to extrapolate to human.
Subject(s)
Acetylgalactosamine , Porphyrias, Hepatic , Acetylgalactosamine/pharmacokinetics , Asialoglycoprotein Receptor/metabolism , Hepatocytes/metabolism , Humans , Porphyrias, Hepatic/metabolism , RNA, Small Interfering/geneticsABSTRACT
Givosiran (trade name GIVLAARI) is a small interfering ribonucleic acid that targets hepatic delta-aminolevulinic acid synthase 1 (ALAS1) messenger RNA for degradation through RNA interference (RNAi) that has been approved for the treatment of acute hepatic porphyria (AHP). RNAi therapeutics, such as givosiran, have a low liability for drug-drug interactions (DDIs) because they are not metabolized by cytochrome 450 (CYP) enzymes, and do not directly inhibit or induce CYP enzymes in the liver. The pharmacodynamic effect of givosiran (lowering of hepatic ALAS1, the first and rate limiting enzyme in the heme biosynthesis pathway) presents a unique scenario where givosiran could potentially impact heme-dependent activities in the liver, such as CYP enzyme activity. This study assessed the impact of givosiran on the pharmacokinetics of substrates of 5 major CYP450 enzymes in subjects with acute intermittent porphyria (AIP), the most common type of AHP, by using the validated "Inje cocktail," comprised of caffeine (CYP1A2), losartan (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), and midazolam (CYP3A4). We show that givosiran treatment had a differential inhibitory effect on CYP450 enzymes in the liver, resulting in a moderate reduction in activity of CYP1A2 and CYP2D6, a minor effect on CYP3A4 and CYP2C19, and a similar weak effect on CYP2C9. To date, this is the first study evaluating the DDI for an oligonucleotide therapeutic and highlights an atypical drug interaction due to the pharmacological effect of givosiran. The results of this study suggest that givosiran does not have a large effect on heme-dependent CYP enzyme activity in the liver.
Subject(s)
Acetylgalactosamine/analogs & derivatives , Cytochrome P-450 Enzyme System/metabolism , Drug Interactions/physiology , Enzyme Activation/physiology , Liver/metabolism , Pyrrolidines/metabolism , RNA, Small Interfering/metabolism , 5-Aminolevulinate Synthetase/metabolism , Acetylgalactosamine/administration & dosage , Acetylgalactosamine/metabolism , Adult , Caffeine/administration & dosage , Caffeine/metabolism , Cross-Over Studies , Enzyme Activation/drug effects , Female , Humans , Liver/drug effects , Male , Metabolic Clearance Rate/drug effects , Metabolic Clearance Rate/physiology , Midazolam/administration & dosage , Midazolam/metabolism , Middle Aged , Omeprazole/administration & dosage , Omeprazole/metabolism , Porphyrias, Hepatic/drug therapy , Porphyrias, Hepatic/metabolism , Pyrrolidines/administration & dosageABSTRACT
Acute hepatic porphyria (AHP) is a family of rare, serious, and potentially life-threatening metabolic disorders caused by mutations in genes encoding enzymes involved in hepatic heme biosynthesis. AHP is characterized by accumulation of neurotoxic heme intermediates, δ-aminolevulinic acid (ALA), and porphobilinogen (PBG), which are thought to be causal for the disease manifestations. Novel therapeutic treatments such as givosiran, an RNA interference therapeutic that was recently approved for treatment of adults with AHP, are focused on reducing the levels of ALA and PBG in patients toward levels observed in a healthy population. While there are two published reports on the distribution of urinary ALA and PBG levels in healthy subjects, these lacked the required details to enable the calculation of reference limits for ALA and PBG. Therefore, urinary ALA and PBG levels were quantified in 150 healthy subjects using a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method that is highly sensitive, specific, accurate, and reproducible. These data were used to establish the upper limit of normal (ULN) values for ALA and PBG as 1.47 and 0.137 mmol/mol Cr, respectively. Relative to these ULN values, baseline urinary ALA and PBG levels in AHP patients were found to be 9.3- to 12-fold, and 238- to 336-fold higher, respectively. Results from this study can serve as a guide to assess the effectiveness of therapeutic interventions in lowering ALA and PBG.
ABSTRACT
Givosiran is a small interfering ribonucleic acid agent that was recently approved in the United States for the treatment of acute hepatic porphyria (AHP). This phase I study evaluated the safety, pharmacokinetic, and pharmacodynamic profile of subcutaneously (SC) administered givosiran in patients with acute intermittent porphyria, the most common AHP type. Givosiran was rapidly absorbed from the SC injection site with peak plasma concentrations achieved within 0.5-5 hours followed by elimination with a short half-life of 4-10 hours. Plasma exposures of AS(N-1)3' givosiran, an active metabolite with equal potency as givosiran, was 35%-75%. Givosiran treatment resulted in a rapid and dose-dependent reduction in urinary aminolevulinic acid (ALA) and porphobilinogen (PBG) towards the upper limit of normal (ULN) in AHP patients. Greater and more sustained reductions in ALA and PBG were achieved with once monthly dosing compared with once quarterly dosing. After monthly dosing, trough ALA levels were reduced to below the ULN, approximately 95% reduction from baseline, at both the 2.5 and 5.0 mg/kg doses.
Subject(s)
Acetylgalactosamine/analogs & derivatives , Aminolevulinic Acid/urine , Porphobilinogen/urine , Porphyria, Acute Intermittent/drug therapy , Pyrrolidines/administration & dosage , Acetylgalactosamine/administration & dosage , Acetylgalactosamine/pharmacokinetics , Acetylgalactosamine/pharmacology , Adult , Dose-Response Relationship, Drug , Drug Administration Schedule , Female , Half-Life , Humans , Injections, Subcutaneous , Male , Middle Aged , Pyrrolidines/pharmacokinetics , Pyrrolidines/pharmacology , Young AdultABSTRACT
OBJECTIVES: Surgical margin status is a significant determinant of treatment outcome in oral cancer. Negative surgical margins can decrease the loco-regional recurrence by five-fold. The current standard of care of intraoperative clinical examination supplemented by histological frozen section, can result in a risk of positive margins from 5 to 17 percent. In this study, we attempted to assess the utility of intraoperative optical coherence tomography (OCT) imaging with automated diagnostic algorithm to improve on the current method of clinical evaluation of surgical margin in oral cancer. MATERIALS AND METHODS: We have used a modified handheld OCT device with automated algorithm based diagnostic platform for imaging. Intraoperatively, images of 125 sites were captured from multiple zones around the tumor of oral cancer patients (nâ¯=â¯14) and compared with the clinical and pathologic diagnosis. RESULTS: OCT showed sensitivity and specificity of 100%, equivalent to histological diagnosis (kappa, ĸâ¯=â¯0.922), in detection of malignancy within tumor and tumor margin areas. In comparison, for dysplastic lesions, OCT-based detection showed a sensitivity of 92.5% and specificity of 68.8% and a moderate concordance with histopathology diagnosis (ĸâ¯=â¯0.59). Additionally, the OCT scores could significantly differentiate squamous cell carcinoma (SCC) from dysplastic lesions (mild/moderate/severe; pâ¯≤â¯0.005) as well as the latter from the non-dysplastic lesions (pâ¯≤â¯0.05). CONCLUSION: The current challenges associated with clinical examination-based margin assessment could be improved with intra-operative OCT imaging. OCT is capable of identifying microscopic tumor at the surgical margins and demonstrated the feasibility of mapping of field cancerization around the tumor.
Subject(s)
Intraoperative Care , Margins of Excision , Mouth Neoplasms/diagnosis , Mouth Neoplasms/surgery , Point-of-Care Testing , Tomography, Optical Coherence , Adult , Aged , Algorithms , Biopsy , Clinical Decision-Making , Disease Management , Female , Humans , Male , Middle Aged , Neoplasm Grading , Neoplasm Staging , Sensitivity and SpecificityABSTRACT
Drug-drug interaction (DDI) studies are described for tezacaftor/ivacaftor, a new cystic fibrosis transmembrane conductance regulator modulator therapy for the treatment of cystic fibrosis. Three phase I DDI studies were conducted in healthy subjects to characterize the DDI profile of tezacaftor/ivacaftor with cytochrome P450 (CYP)3A substrates, CYP3A inhibitors, and a permeability glycoprotein (P-gp) substrate. The effects of steady-state tezacaftor/ivacaftor on the pharmacokinetics (PKs) of digoxin (a P-gp substrate), midazolam, and ethinyl estradiol/norethindrone (CYP3A substrates) were evaluated. Effects of strong (itraconazole) and moderate (ciprofloxacin) CYP3A inhibitors on tezacaftor/ivacaftor PKs were also determined. Tezacaftor/ivacaftor increased digoxin area under the curve (AUC) by 30% but did not affect midazolam, ethinyl estradiol, or norethindrone exposures. Itraconazole increased the AUC of tezacaftor 4-fold and ivacaftor 15.6-fold. Ciprofloxacin had no significant effect on tezacaftor or ivacaftor exposure. Coadministration of tezacaftor/ivacaftor may increase exposure of sensitive P-gp substrates. Tezacaftor/ivacaftor is unlikely to impact exposure of drugs metabolized by CYP3A, including hormonal contraceptives. Strong CYP3A inhibitors significantly increase the exposures of tezacaftor and ivacaftor.
Subject(s)
Aminophenols/pharmacokinetics , Benzodioxoles/pharmacokinetics , Indoles/pharmacokinetics , Quinolones/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Adolescent , Adult , Aminophenols/blood , Benzodioxoles/blood , Ciprofloxacin/pharmacology , Cytochrome P-450 CYP3A Inhibitors/pharmacology , Drug Interactions , Drug Therapy, Combination , Ethinyl Estradiol , Female , Humans , Indoles/blood , Male , Middle Aged , Quinolones/blood , Young AdultABSTRACT
The study objective was to investigate factors that affect the central nervous system (CNS) distribution of elacridar. Elacridar inhibits transport mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) and has been used to study the influence of transporters on brain distribution of chemotherapeutics. Adequate distribution of elacridar across the blood-brain barrier (BBB) and into the brain parenchyma is necessary to target tumor cells in the brain that overexpress transporters and reside behind an intact BBB. We examined the role of P-gp and Bcrp on brain penetration of elacridar using Friend leukemia virus strain B wild-type, Mdr1a/b(-/-), Bcrp1(-/-), and Mdr1a/b(-/-)Bcrp1(-/-) mice. Initially, the mice were administered 2.5 mg/kg of elacridar intravenously, and the plasma and brain concentrations were determined. The brain-to-plasma partition coefficient of elacridar in the wild-type mice was 0.82, as compared with 3.5 in Mdr1a/b(-/-) mice, 6.6 in Bcrp1(-/-) mice, and 15 in Mdr1a/b(-/-)Bcrp1(-/-) mice, indicating that both P-gp and Bcrp limit the brain distribution of elacridar. The four genotypes were then administered increasing doses of elacridar, and the CNS distribution of elacridar was determined. The observed and model predicted maximum brain-to-plasma ratios (Emax) at the highest dose were not significantly different in all genotypes. However, the ED50 was lower for Mdr1a/b(-/-) mice compared with Bcrp1(-/-) mice. These findings correlate with the relative expression of P-gp and Bcrp at the BBB in these mice and demonstrate the quantitative enhancement in elacridar CNS distribution as a function of its dose. Overall, this study provides useful concepts for future applications of elacridar as an adjuvant therapy to improve targeting of chemotherapeutic agents to tumor cells in the brain parenchyma.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , ATP-Binding Cassette Transporters/metabolism , Acridines/pharmacokinetics , Blood-Brain Barrier/drug effects , Tetrahydroisoquinolines/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily B/genetics , ATP Binding Cassette Transporter, Subfamily B/metabolism , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/genetics , Acridines/administration & dosage , Animals , Blood-Brain Barrier/metabolism , Cell Culture Techniques , Central Nervous System/drug effects , Central Nervous System/metabolism , Dogs , Dose-Response Relationship, Drug , Humans , Injections, Intravenous , Madin Darby Canine Kidney Cells , Mice , Mice, Knockout , Models, Biological , Nonlinear Dynamics , Tetrahydroisoquinolines/administration & dosage , Tetrahydroisoquinolines/blood , Tissue Distribution , ATP-Binding Cassette Sub-Family B Member 4ABSTRACT
Antifolates, in particular methotrexate (MTX), have been widely used in the treatment of primary and secondary tumors of the central nervous system (CNS). Pemetrexed (PMX) is a novel antifolate that also exhibits potent antitumor activity against CNS malignancies. Studies have shown that brain distribution of both antifolates is significantly restricted, possible due to active efflux transport at the blood-brain barrier (BBB). This study characterizes the brain-to-blood transport of PMX and MTX and examines the role of several efflux transporters in brain distribution of the antifolates by use of the intracerebral microinjection technique (brain efflux index). The results from this study show that both PMX and MTX undergo saturable efflux transport across the BBB, with elimination half-lives of approximately 39 minutes and 29 minutes, respectively. Of the various efflux transporters this study investigated, multidrug resistance-associated protein 2 (Mrp2) does not play an important role in the brain distribution of the two antifolate drugs. Interestingly, breast-cancer resistance protein (Bcrp) makes a significant contribution to the brain elimination of MTX but not PMX. In addition, the brain-to-blood transport of both antifolates was inhibited by probenecid and benzylpenicillin, suggesting the involvement of organic anion transporters in the efflux of these compounds from the brain, with organic anion transporter 3 (Oat3) being a possibility. Our results suggest that one of the underlying mechanisms behind the limited brain distribution of PMX and MTX is active efflux transport processes at the BBB, including a benzylpenicillin-sensitive transport system and/or the active transporter Bcrp.
Subject(s)
Blood-Brain Barrier/metabolism , Folic Acid Antagonists/pharmacokinetics , Glutamates/pharmacokinetics , Guanine/analogs & derivatives , Methotrexate/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/deficiency , ATP-Binding Cassette Transporters/genetics , Animals , Biological Transport , Blood-Brain Barrier/drug effects , Capillary Permeability/drug effects , Folic Acid Antagonists/administration & dosage , Folic Acid Antagonists/blood , Glutamates/administration & dosage , Glutamates/blood , Guanine/administration & dosage , Guanine/blood , Guanine/pharmacokinetics , Half-Life , Male , Methotrexate/administration & dosage , Methotrexate/blood , Mice , Mice, Inbred C57BL , Mice, Knockout , Microinjections , Multidrug Resistance-Associated Protein 2 , Multidrug Resistance-Associated Proteins/deficiency , Multidrug Resistance-Associated Proteins/genetics , Organic Anion Transporters, Sodium-Independent/antagonists & inhibitors , Organic Anion Transporters, Sodium-Independent/metabolism , Pemetrexed , Penicillin G/pharmacology , Probenecid/pharmacologyABSTRACT
Despite aggressive treatment with radiation and chemotherapy, recurrence of glioblastoma multiforme (GBM) is inevitable. The objective of this study was to show that the blood-brain barrier (BBB), through a combination of tight junctions and active efflux transporters in the brain microvasculature, can significantly restrict delivery of molecularly targeted agents to invasive glioma cells. Transgenic mice lacking P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) were used to study efflux of erlotinib at the BBB. A U87 rat xenograft model of GBM was used to investigate the regional distribution of erlotinib to the tumor, and brain regions surrounding the tumor. The effect of concurrent administration of elacridar on regional tumor distribution of erlotinib was evaluated. We show that erlotinib transport across an intact BBB is significantly restricted due to P-gp- and Bcrp-mediated efflux transport. We then show that the BBB is sufficiently intact in areas of brain adjacent to the tumor core to significantly restrict erlotinib delivery. Inhibition of P-gp and Bcrp by the dual inhibitor elacridar dramatically increased erlotinib delivery to the tumor core, rim, and normal brain. These results provide conclusive evidence of the impact that active efflux at the BBB has on the delivery of molecularly targeted therapy to different tumor regions in glioma. These data also support the possibility that the repeated failure of clinical trials of new drugs for gliomas may be in part due to a failure to achieve effective concentrations in invasive tumor cells that reside behind an intact BBB.
Subject(s)
Brain Neoplasms/drug therapy , Glioma/drug therapy , Animals , Blood-Brain Barrier , Brain Neoplasms/pathology , Drug Delivery Systems , Glioma/pathology , Neoplasm Invasiveness , Rats , Transplantation, HeterologousABSTRACT
BACKGROUND: The effectiveness of tyrosine kinase inhibitors (TKI) in preventing brain metastases in patients with renal cell carcinoma is unclear. METHODS: Preclinical studies were conducted to determine the steady-state brain and plasma concentrations of sorafenib and sunitinib in mice deficient in the drug efflux transporters; p-glycoprotein, and breast cancer resistance protein. A single-institution retrospective analysis of patients treated from 2008 to 2010 was conducted to assess the incidence of brain metastases before and during TKI treatment. RESULTS: Transport of sorafenib and sunitinib across the blood-brain barrier was restricted. Retrospective analysis revealed that the median time to develop metastatic brain disease was 28 months (range, 1-108 months) while on TKI therapy and 11.5 months (range, 0-64 months) in patients who did not receive TKI therapy. The incidence of brain metastases per month in patients not treated with TKI therapy was 1.6 higher than the incidence in patients treated with TKI therapy. CONCLUSIONS: Penetration of sorafenib or sunitinib through an intact blood-brain barrier to brain tissue is limited; however, the incidence of brain metastases per unit time is decreased in patients on TKI therapy in comparison with the "cytokine" era.
Subject(s)
Antineoplastic Agents/therapeutic use , Brain Neoplasms/secondary , Carcinoma, Renal Cell/drug therapy , Indoles/therapeutic use , Kidney Neoplasms/drug therapy , Niacinamide/analogs & derivatives , Phenylurea Compounds/therapeutic use , Protein Kinase Inhibitors/therapeutic use , Pyrroles/therapeutic use , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/genetics , Animals , Antineoplastic Agents/pharmacokinetics , Blood-Brain Barrier , Brain/metabolism , Brain Neoplasms/drug therapy , Carcinoma, Renal Cell/secondary , Female , Humans , Indoles/pharmacokinetics , Male , Mice , Mice, Knockout , Middle Aged , Niacinamide/pharmacokinetics , Niacinamide/therapeutic use , Phenylurea Compounds/pharmacokinetics , Protein Kinase Inhibitors/pharmacokinetics , Pyrroles/pharmacokinetics , Retrospective Studies , Sorafenib , Sunitinib , Treatment OutcomeABSTRACT
The importance of the blood-brain barrier in preventing effective pharmacotherapy of glioblastoma has been controversial. The controversy stems from the fact that vascular endothelial cell tight junctions are disrupted in the tumor, allowing some systemic drug delivery. P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) efflux drugs from brain capillary endothelial cells into the blood. We tested the hypothesis that although the tight junctions are "leaky" in the core of glioblastomas, active efflux limits drug delivery to tumor-infiltrated normal brain and consequently, treatment efficacy. Malignant gliomas were induced by oncogene transfer into wild-type (WT) mice or mice deficient for Pgp and BCRP (knockout, KO). Glioma-bearing mice were orally dosed with dasatinib, a kinase inhibitor and dual BCRP/PgP substrate that is being currently tested in clinical trials. KO mice treated with dasatinib survived for twice as long as WT mice. Microdissection of the tumor core, invasive rim, and normal brain revealed 2- to 3-fold enhancement in dasatinib brain concentrations in KO mice relative to WT. Analysis of signaling showed that poor drug delivery correlated with the lack of inhibition of a dasatinib target, especially in normal brain. A majority of human glioma xenograft lines tested expressed BCRP or PgP and were sensitized to dasatinib by a dual BCRP/Pgp inhibitor, illustrating a second barrier to drug delivery intrinsic to the tumor itself. These data show that active efflux is a relevant obstacle to treating glioblastoma and provide a plausible mechanistic basis for the clinical failure of numerous drugs that are BCRP/Pgp substrates.
Subject(s)
Brain/metabolism , Glioblastoma/drug therapy , Molecular Targeted Therapy , Pyrimidines/metabolism , Pyrimidines/therapeutic use , Thiazoles/metabolism , Thiazoles/therapeutic use , ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily B, Member 1/deficiency , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/antagonists & inhibitors , ATP-Binding Cassette Transporters/deficiency , ATP-Binding Cassette Transporters/metabolism , Acridines/chemistry , Acridines/pharmacology , Acridines/therapeutic use , Animals , Blood-Brain Barrier/drug effects , Blood-Brain Barrier/metabolism , Blood-Brain Barrier/pathology , Brain/drug effects , Brain/pathology , Dasatinib , Disease Models, Animal , Endothelium, Vascular/drug effects , Endothelium, Vascular/metabolism , Endothelium, Vascular/pathology , Glioblastoma/blood supply , Glioblastoma/pathology , Humans , Mice , Mice, Knockout , Oncogenes , Permeability/drug effects , Pyrimidines/chemistry , Pyrimidines/pharmacology , Signal Transduction/drug effects , Survival Analysis , Tetrahydroisoquinolines/chemistry , Tetrahydroisoquinolines/pharmacology , Tetrahydroisoquinolines/therapeutic use , Thiazoles/chemistry , Thiazoles/pharmacology , Tight Junctions/drug effects , Tight Junctions/metabolism , Tight Junctions/pathology , Tissue Distribution/drug effects , Treatment Outcome , Xenograft Model Antitumor AssaysABSTRACT
The objective of this study was to determine the bioavailability and disposition of elacridar (GF120918; N-(4-(2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl)phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide) in plasma and brain after various routes of administration in the mouse. Elacridar is a potent inhibitor of P-glycoprotein and breast cancer resistance protein and has been used to examine the influence of these efflux transporters on drug distribution to brain. Friend leukemia virus strain B mice were administered 100 mg/kg elacridar either orally or intraperitoneally. The absolute bioavailability of elacridar after oral or intraperitoneal dosing was determined with respect to an intravenous dose of 2.5 mg/kg. At these doses, the absolute bioavailability was 0.22 for oral administration and 0.01 for intraperitoneal administration. The terminal half-life of elacridar was approximately 4 h after intraperitoneal and intravenous administration and nearly 20 h after oral dosing. The brain-to-plasma partition coefficient (Kp,brain) of elacridar increased as plasma exposure increased, suggesting saturation of the efflux transporters at the blood-brain barrier. The Kp,brain after intravenous, intraperitoneal, and oral dosing was 0.82, 0.43, and 4.31, respectively. The low aqueous solubility and high lipophilicity of elacridar result in poor oral absorption, most likely dissolution-rate-limited. These results illustrate the importance of the route of administration and the resultant plasma exposure in achieving effective plasma and brain concentrations of elacridar and can be used as a guide for future studies involving elacridar administration and in developing formulation strategies to overcome the poor absorption.
Subject(s)
Acridines/pharmacokinetics , Brain/metabolism , Tetrahydroisoquinolines/pharmacokinetics , Acridines/administration & dosage , Animals , Biological Availability , Mice , Tetrahydroisoquinolines/administration & dosageABSTRACT
The objective of this study was to quantitatively examine the protein expression of relevant transporters and other proteins in the brain capillary endothelial cells isolated from wild-type mice and P-glycoprotein (P-gp), breast cancer resistance protein (Bcrp), and P-gp/Bcrp knockout mice. After the isolation of brain capillary endothelial cells, a highly sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring was used to determine the quantitative expression of membrane transporters at the blood-brain barrier (BBB) of the various mouse genotypes. Quantitative expression of 29 protein molecules, including 12 ATP-binding cassette transporters, 10 solute carrier transporters, five receptors, and two housekeeping proteins, was examined by quantitative proteomics in the four mouse genotypes. There was no significant difference in the expression of P-gp between the wild-type and Bcrp1(-/-) mice. Likewise, Bcrp expression was not significantly different between the wild-type and Mdr1a/b(-/-) mice. There was no significant difference in the expression of any of the measured proteins in the brain capillary endothelial cells across the genotypes, except for the lack of expression of the corresponding protein in the mice that had a genetic deletion of P-gp or Bcrp. In conclusion, using a quantitative proteomic approach, we have shown that there are no changes in the expression of several relevant transporters in brain capillary endothelial cells isolated from single and combination knockout mice. These data suggest that the mechanism behind the functional compensation between P-gp and Bcrp at the BBB is not related to compensatory changes in transporter expression.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/biosynthesis , ATP-Binding Cassette Transporters/biosynthesis , Endothelial Cells/metabolism , Endothelium, Vascular/cytology , Endothelium, Vascular/metabolism , Proteomics/methods , ATP Binding Cassette Transporter, Subfamily B, Member 1/deficiency , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/deficiency , ATP-Binding Cassette Transporters/genetics , Animals , Blood-Brain Barrier/cytology , Blood-Brain Barrier/metabolism , Cell Separation/methods , Endothelial Cells/cytology , Gene Expression Regulation , Mice , Mice, KnockoutABSTRACT
The ATP-binding cassette transporters P-glycoprotein and breast cancer resistance protein have been shown to be critical determinants limiting drug transport across the BBB into the brain. Several therapeutic agents have been shown to be substrates for these two transporters, and as a result they have limited distribution to the brain. Recently, it has been shown that these two drug transporters cooperate at the BBB and brain penetration of dual substrates increases significantly only when both are absent, e.g., in the Mdr1a/1b(-/-)Bcrp1(-/-) mice. The present study uses the brain penetration of sorafenib to investigate these findings and attempts to explain the mechanistic basis of this cooperation with a simple theory based on affinity and capacity dependent carrier-mediated transport. The brain efflux index method, combined with the organotypic brain slices, was used to determine the net contribution of P-gp and BCRP to the total clearance of sorafenib out of the brain and show that its efflux at the BBB is mediated primarily by BCRP. Sorafenib clearance out of the brain decreased 2-fold in the Bcrp1(-/-) mice and 2.5-fold in the Mdr1a/1b(-/-)Bcrp1(-/-) mice. Clearance out of brain when P-gp was absent did not change significantly compared to wild-type. We also investigated the expression of P-gp and BCRP in the genetic knockout animals and saw no differences in either P-gp or BCRP in the transporter deficient mice compared to the wild-type mice. In conclusion, this study explains the cooperation of P-gp and BCRP by analysis of the efflux clearance of sorafenib and correlating it to the "mechanisms" that determine the clearance, i.e., affinity and capacity.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B/metabolism , ATP-Binding Cassette Transporters/metabolism , Benzenesulfonates/pharmacokinetics , Blood-Brain Barrier/metabolism , Pyridines/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily B/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/genetics , Animals , Blotting, Western , Breast Neoplasms/metabolism , Female , Mice , Mice, Mutant Strains , Niacinamide/analogs & derivatives , Phenylurea Compounds , SorafenibABSTRACT
Cediranib is an orally active tyrosine kinase inhibitor that targets the vascular endothelial growth factor receptor family. Because of its potent antiangiogenic and antitumor activities, cediranib has been evaluated for therapy in glioma, a primary brain tumor. This study investigated the influence of two important efflux transporters at the blood-brain barrier, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), on the delivery of cediranib to the central nervous system. In vitro studies indicated that cediranib is a dual substrate for both P-gp and Bcrp. It is noteworthy that in spite of the in vitro data the in vivo mouse disposition studies conclusively showed that P-gp was the dominant transporter restricting the brain distribution of cediranib. The brain-to-plasma partitioning (AUC(brain)/AUC(plasma), where AUC is area under the curve) and the steady-state brain-to-plasma concentration ratio of cediranib were approximately 20-fold higher in Mdr1a/bâ»/â» and Mdr1a/bâ»/â»Bcrp1â»/â» mice compared with wild-type and Bcrp1â»/â» mice. Moreover, there was no significant difference in brain distribution of cediranib between wild-type and Bcrp1â»/â» mice and between Mdr1a/bâ»/â» and Mdr1a/bâ»/â»Bcrp1â»/â» mice. These results show that, unlike other tyrosine kinase inhibitors that are dual substrates for P-gp and Bcrp, Bcrp does not restrict the distribution of cediranib across the blood-brain barrier. We also show that inhibition of P-gp using specific or nonspecific inhibitors resulted in significantly enhanced delivery of cediranib to the brain. Concurrent administration of cediranib with chemical modulators of efflux transporters can be used as a strategy to enhance delivery and thus efficacy of cediranib in the brain. These findings are clinically relevant to the efficacy of cediranib chemotherapy in glioma.
Subject(s)
Blood-Brain Barrier/metabolism , Brain/metabolism , Quinazolines/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/antagonists & inhibitors , ATP-Binding Cassette Transporters/metabolism , Animals , Biological Transport , Cell Line , Cell Membrane Permeability , Dogs , Humans , Mice , Mice, Knockout , Quinazolines/pharmacology , Tissue DistributionABSTRACT
Brain cancer is a devastating disease. Despite extensive research, treatment of brain tumors has been largely ineffective and the diagnosis of brain cancer remains uniformly fatal. Failure of brain cancer treatment may be in part due to limitations in drug delivery, influenced by the ABC drug efflux transporters P-gp and BCRP at the blood-brain and blood-tumor barriers, in brain tumor cells, as well as in brain tumor stem-like cells. P-gp and BCRP limit various anti-cancer drugs from entering the brain and tumor tissues, thus rendering chemotherapy ineffective. To overcome this obstacle, two strategies - targeting transporter regulation and direct transporter inhibition - have been proposed. In this review, we focus on these strategies. We first introduce the latest findings on signaling pathways that could potentially be targeted to down-regulate P-gp and BCRP expression and/or transport activity. We then highlight in detail the new paradigm of P-gp and BCRP working as a "cooperative team of gatekeepers" at the blood-brain barrier, discuss its ramifications for brain cancer therapy, and summarize the latest findings on dual P-gp/BCRP inhibitors. Finally, we provide a brief summary with conclusions and outline the perspectives for future research endeavors in this field.