Rifampin and ritonavir increase oral availability and elacridar enhances overall exposure and brain accumulation of the NTRK inhibitor larotrectinib.

INTRODUCTION: Larotrectinib is an FDA-approved oral small-molecule inhibitor for neurotrophic tropomyosin receptor kinase (NTRK) fusion-positive cancer treatment. Here larotrectinib pharmacokinetic behavior upon co-administration with prototypical inhibitors of the efflux transporters ABCB1/ABCG2 (elacridar), the SLCO1A/1B (OATP1A/1B) uptake transporters (rifampin), and the drug-metabolizing enzyme CYP3A (ritonavir), respectively, was investigated. METHODS: Inhibitors were orally administered prior to oral larotrectinib (10 mg/kg) to relevant genetically modified mouse models. Larotrectinib plasma and tissue homogenate concentrations were measured by a liquid chromatography-tandem mass spectrometric assay. RESULTS: Elacridar increased oral availability (2.7-fold) and markedly improved brain-to-plasma ratios (5.0-fold) of larotrectinib in wild-type mice. Mouse (m)Oatp1a/1b but not hepatic transgenic human (h)OATP1B1 or -1B3 restricted larotrectinib oral availability and affected its tissue distribution. Rifampin enhanced larotrectinib oral availability not only in wild-type mice (1.9-fold), but surprisingly also in Slco1a/1b-/- mice (1.7-fold). Similarly, ritonavir increased the larotrectinib plasma exposure in both wild-type (1.5-fold) and Cyp3a-/- mice (1.7-fold). Intriguingly, both rifampin and ritonavir decreased liver and/or intestinal larotrectinib levels in all related experimental groups, suggesting additional inhibition of enterohepatic Abcb1a/1b activity. CONCLUSIONS: Elacridar enhances both larotrectinib plasma and tissue exposure and especially relative brain penetration, which might be therapeutically relevant. Hepatic mOatp1a/1b but not hOATP1B1 or -1B3 transported larotrectinib. Additionally, rifampin enhances larotrectinib systemic exposure, most likely by inhibiting mOatp1a/1b, but probably also hepatic and/or intestinal mAbcb1. Similar to rifampin, dual-inhibition functions of ritonavir affecting both CYP3A enzymes and enterohepatic Abcb1 transporters enhanced larotrectinib oral availability. The obtained insights may be used to further optimize the clinical-therapeutic application of larotrectinib.

Optimization of dose and route of administration of the P-glycoprotein inhibitor, valspodar (PSC-833) and the P-glycoprotein and breast cancer resistance protein dual-inhibitor, elacridar (GF120918) as dual infusion in rats.

Transporters can play a key role in the absorption, distribution, metabolism, and excretion of drugs. Understanding these contributions early in drug discovery allows for more accurate projection of the clinical pharmacokinetics. One method to assess the impact of transporters in vivo involves co-dosing specific inhibitors. The objective of the present study was to optimize the dose and route of administration of a P-glycoprotein (P-gp) inhibitor, valspodar (PSC833), and a dual P-gp/breast cancer resistance protein (BCRP) inhibitor, elacridar (GF120918), by assessing the transporters' impact on brain penetration and absorption. A dual-infusion strategy was implemented to allow for flexibility with dose formulation. The chemical inhibitor was dosed intravenously via the femoral artery, and a cassette of known substrates was infused via the jugular vein. Valspodar or elacridar was administered as 4.5-hour constant infusions over a range of doses. To assess the degree of inhibition, the resulting ratios of brain and plasma concentrations, Kp's, of the known substrates were compared to the vehicle control. These data demonstrated that doses greater than 0.9 mg/hr/kg valspodar and 8.9 mg/hr/kg elacridar were sufficient to inhibit P-gp- and BCRP-mediated efflux at the blood-brain barrier in rats without any tolerability issues. Confirmation of BBB restriction by efflux transporters in preclinical species allows for subsequent prediction in humans based upon the proteomic expression at rodent and human BBB. Overall, the approach can also be applied to inhibition of efflux at other tissues (gut absorption, liver clearance) or can be extended to other transporters of interest using alternate inhibitors.

Targeted Tumor Therapy with Radiolabeled DNA Intercalator: A Possibility? Preclinical Investigations with 177Lu-Acridine.

OBJECTIVE: A DNA intercalating agent reversibly stacks between the adjacent base pairs of DNA and thus is expected to exhibit preferential localization in the tumorous lesions as tumors are associated with enhanced DNA replication. Therefore, radiolabeled DNA intercalators are supposed to have potential to be used in targeted tumor therapy. Working in this direction, an attempt was made to radiolabel 9-aminoacridine, a DNA intercalator, with 177Lu, one of the most useful therapeutic radionuclides, and study the potential of 177Lu-acridine in targeted tumor therapy. Experiments. 9-Aminoacridine was coupled with p-NCS-benzyl-DOTA to facilitate radiolabeling, and the conjugate was radiolabeled with 177Lu. Different reaction parameters were optimized in order to obtain 177Lu-acridine complex with maximum radiochemical purity. In vitro stability of the radiolabeled complex was studied in normal saline and human blood serum. Biological behavior of the radiolabeled agent was studied both in vitro and in vivo using the Raji cell line and fibrosarcoma tumor-bearing Swiss mice, respectively. RESULTS: 177Lu-acridine complex was obtained with ~100% radiochemical purity under the optimized reaction conditions involving incubation of 1.5 mg/mL of ligand with 177Lu (1 mCi, 37 MBq) at 100°C at pH ~5 for 45 minutes. The complex maintained a radiochemical purity of >85% in saline at 6 d and >70% in human serum at 2 d postpreparation. In vitro cellular study showed uptake of the radiotracer (5.3 ± 0.13%) in the Raji cells along with significant cytotoxicity (78.06 ± 2.31% after 6 d). Biodistribution study revealed considerable accumulation of the radiotracer in tumor 9.98 ± 0.13 %ID/g within 1 h postadministration and retention therein till 6 d postadministration 4.00 ± 0.16 %ID/g with encouraging tumor to nontarget organ uptake ratios. CONCLUSIONS: The present study, although preliminary, indicates the potential of 177Lu-acridine and thus radiolabeled DNA intercalators in targeted tumor therapy. However, further detailed evaluation is required to explore the actual potential of such agents in targeted tumor therapy.

Preparation and Preliminary Evaluation of 68Ga-Acridine: An Attempt to Study the Potential of Radiolabeled DNA Intercalator as a PET Radiotracer for Tumor Imaging.

INTRODUCTION: Acridine is a well-known DNA intercalator and thereby gets easily inserted within DNA. As uncontrolled rapid cell division is one of the primary characteristics of the tumors, it is expected that acridine or its suitable derivatives will have preferential accumulation in the tumorous lesions. Therefore, an attempt was made to radiolabel an acridine derivative with 68Ga and study the potential of the 68Ga-acridine complex as a PET agent for tumor imaging. METHODS: 9-aminoacridine was coupled with p-NCS-benzyl-DOTA to render it suitable for labeling with 68Ga. The purified acridine-DOTA conjugate was radiolabeled with 68Ga, eluted from a 68Ge/68Ga radionuclide generator. Various radiolabeling parameters were optimized and the stability of the radiolabeled preparation was studied. The biological behavior of the 68Ga-acridine complex was studied both in vitro and in vivo using Raji cell line and fibrosarcoma tumor bearing Swiss mice, respectively. RESULTS: 68Ga-acridine complex was obtained with ~100% radiochemical purity under the optimized reaction conditions involving incubation of 2mg/mL of ligand at 100°C for 30 minutes. The complex maintained a radiochemical purity of >95% in normal saline and >65% in human blood serum at 3h post-incubation. In vitro cellular study showed (3.2±0.1)% uptake of the radiotracer in the Raji cells. Biodistribution study revealed significant tumor accumulation [(11.41±0.41)% injected activity in per gram] of the radiotracer within 1h postadministration along with uptake in other non-target organs such as, blood, liver, GIT kidney etc. Conclusion: The present study indicates the potential of 68Ga-acridine as a PET agent for imaging of tumorous lesions. However, further detailed evaluation of the agent is warranted to explore its actual potential.

A new photosafety screening strategy based on in chemico photoreactivity and in vitro skin exposure for dermally-applied chemicals.

This study involved an attempt to establish a new photosafety screening system for dermally-applied chemicals consisting of a reactive oxygen species (ROS) assay and an in vitro skin permeation test. The ROS assay was undertaken to evaluate photoreactivity of six test compounds, acridine (ACD), furosemide (FSM), hexachlorophene (HCP), 8-methoxypsoralen (MOP), norfloxacin (NFX), and promethazine (PMZ), and the in vitro skin permeation test was conducted to obtain steady-state concentration (Css) values of test compounds in removed rat skin. All test compounds were photoreactive based on ROS generation under simulated sunlight exposure. In particular, ROS generation from ACD was high compared with other test compounds, and photoreactivity of ACD was deduced to be potent. The Css values of ACD, HCP, MOP, and PMZ were over 50 µg/mL, and skin exposure to FSM and NFX was found to be extremely low. Upon these findings, ACD was judged to be highly phototoxic. The rank for phototoxic risk of test compounds based on photoreactivity and in vitro skin exposure was mostly in agreement with outcomes on their in vivo phototoxicity in rats. The proposed strategy, an alternative to animal testing, would be efficacious for photosafety evaluation of drug candidates in early stages of pharmaceutical development.

Acridine-based (thio)semicarbazones and hydrazones: Synthesis, in vitro urease inhibition, molecular docking and in-silico ADME evaluation.

Urease is a bacterial enzyme that is responsible for virulence of various pathogenic bacteria such as Staphylococcus aureus, Proteus mirabilis, Klebsiella pneumoniae, Ureaplasma urealyticum, Helicobacter pylori and Mycobacterium tuberculosis. Increased urease activity aids in survival and colonization of pathogenic bacteria causing several disorders especially gastric ulceration. Hence, urease inhibitors are used for treatment of such diseases. In search of new molecules with better urease inhibitory activity, herein we report a series of acridine derived (thio)semicarbazones (4a-4e, 6a-6l) that were found to be active against urease enzyme. Molecular docking studies were carried out to better comprehend the preferential mode of binding of these compounds against urease enzyme. Docking against urease from pathogenic bacterium S. pasteurii was also carried out with favorable results. In silico ADME evaluation was done to determine drug likeness of synthesized compounds.

Codelivery of doxorubicin and elacridar to target both liver cancer cells and stem cells by polylactide-co-glycolide/d-alpha-tocopherol polyethylene glycol 1000 succinate nanoparticles.

PURPOSE: Liver cancer is the third leading cause of cancer-related deaths worldwide. Liver cancer stem cells (LCSCs) are a subpopulation of cancer cells that are responsible for the initiation, progression, drug resistance, recurrence, and metastasis of liver cancer. Recent studies have suggested that the eradication of both LCSCs and liver cancer cells is necessary because the conversion of cancer stem cells (CSCs) to cancer cells occasionally occurs. As ATP-binding cassette (ABC) transporters are overexpressed in both CSCs and cancer cells, combined therapies using ABC transporter inhibitors and chemotherapy drugs could show superior therapeutic efficacy in liver cancer. In this study, we developed poly(lactide-co-glycolide)/d-alpha-tocopherol polyethylene glycol 1000 succinate nanoparticles to accomplish the simultaneous delivery of an optimized ratio of doxorubicin (DOX) and elacridar (ELC) to target both LCSCs and liver cancer cells. METHODS: Median-effect analysis was used for screening of DOX and ELC for synergy in liver cancer cells (HepG2 cells) and LCSCs (HepG2 tumor sphere [HepG2-TS]). Then, nanoparticles loaded with DOX and ELC at the optimized ratio (NDEs) were prepared by nanoprecipitation method. The cytotoxicity and colony and tumor sphere formation ability of nanoparticles were investigated in vitro, and the tissue distribution and antitumor activity of nanoparticles were evaluated in vivo. RESULTS: We demonstrated that a DOX/ELC molar ratio of 1:1 was synergistic in HepG2 cells and HepG2-TS. NDEs were shown to exhibit significantly increased cytotoxic effects against both HepG2 and HepG2-TS compared with DOX-loaded nanoparticles (NDs) or ELC-loaded nanoparticles (NEs) in vitro. In vivo studies demonstrated that the nanoparticles exhibited better tumor targeting, with NDE showing the strongest antitumor activity with lower systemic toxicity. CONCLUSION: These results suggested that NDE represented a promising combination therapy against liver cancer by targeting both liver cancer cells and CSCs.

Impact of P-Glycoprotein on Intestinal Absorption of an Inhibitor of Apoptosis Protein Antagonist in Rats: Mechanisms of Nonlinear Pharmacokinetics and Food Effects.

PURPOSE: This study was designed to investigate the effects of P-glycoprotein (P-gp) expressed in the intestine on the nonlinear pharmacokinetics (PK) of T-3256336, an inhibitor of apoptosis protein inhibitor, and food effects on its bioavailability in rats. METHODS: To investigate the factors that contribute to nonlinear PK of T-3256336 in the intestine and liver, rats double-cannulated in the portal vein and femoral artery (PS rats) were used. FaFg (Fa, absorption ratio; Fg, intestinal availability) and hepatic availability (Fh) were simultaneously evaluated based on the difference between the portal and systemic blood area under the concentration-time curve (AUC). Elacridar was used as a P-gp inhibitor to assess the impact of P-gp on the intestinal absorption. RESULTS: After oral administration of T-3256336 to PS rats at 3 and 30 mg/kg, FaFg value increased with dose escalation, whereas Fh value was nearly constant. Moreover, co-administration of elacridar resulted in a 5-fold increase in the FaFg value at 3 mg/kg. The AUC value of T-3256336 under fed conditions was 3-fold lower than that under fasted conditions. This food effect on the oral bioavailability (BA) was reduced by concomitant administration of elacridar. CONCLUSION: P-gp expressed in the intestine would cause nonlinear PK and a food effect on BA of T-3256336 in rats.

Intravenous infusion for the controlled exposure to the dual ABCB1 and ABCG2 inhibitor elacridar in nonhuman primates.

Elacridar (GF120918) is a highly potent inhibitor of both P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2), the main efflux transporters expressed at the blood-brain barrier (BBB). Elacridar shows very low aqueous solubility, which complicates its formulation for i.v. administration. An intravenous infusion protocol would be preferred to achieve high and controlled plasma concentrations of elacridar in large animals, including nonhuman primates. Formulation of elacridar for i.v. infusion was achieved using a co-solvent strategy, resulting in an aqueous dispersion with a final concentration of 5 g L-1 elacridar with tetrahydrofuran (5% w/v) in aqueous D-glucose solution (2.5%, w/v). Particle size (mean = 2.8 ± 0.9 µm) remained stable for 150 min. The preparation was i.v. administered as a continuous infusion (12 mg kg-1 h-1 for 90 min) to three baboons. Arterial and venous plasma pharmacokinetics (PK) of elacridar were monitored using a newly developed and validated HPLC-UV method. Elacridar concentration increased rapidly to reach a plateau at 9.5 µg mL-1 within 20 min after the start of infusion. Elacridar PK in venous plasma did not differ from arterial plasma facing the BBB, indicating the absence of an arteriovenous concentration gradient. Intravenous infusion of elacridar allows for controlled exposure of the BBB and offers a useful tool to assess the impact of ABCB1/ABCG2 on drug disposition to the brain in nonhuman primates, a relevant animal model for the study of transporter function at the BBB.

Therapeutic Potential and Utility of Elacridar with Respect to P-glycoprotein Inhibition: An Insight from the Published In Vitro, Preclinical and Clinical Studies.

The occurrence of efflux mechanisms via Permeability-glycoprotein (P-gp) recognized as an important physiological process impedes drug entry or transport across membranes into tissues. In some instances, either low oral bioavailability or lack of brain penetration has been attributed to P-gp mediated efflux activity. Therefore, the objective of development of P-gp inhibitors was to facilitate the attainment of higher drug exposures in tissues. Many third-generation P-gp inhibitors such as elacridar, tariquidar, zosuquidar, etc. have entered clinical development to fulfil the promise. The body of evidence from in vitro and in vivo preclinical and clinical data reviewed in this paper provides the basis for an effective blockade of P-gp efflux mechanism by elacridar. However, clinical translation of the promise has been elusive not just for elacridar but also for other P-gp inhibitors in this class. The review provides introspection and perspectives on the lack of clinical translation of this class of drugs and a broad framework of strategies and considerations in the potential application of elacridar and other P-gp inhibitors in oncology therapeutics.

Evaluation of a general toxicity study incorporating phototoxicity assessments in Sprague-Dawley rats.

Previously, we showed that phototoxicity assessments in Sprague-Dawley (SD) rats can detect phototoxic potential to the same degree as those in guinea pigs. In this study, we examined whether phototoxicity assessments can be incorporated into general toxicology studies, using SD rats. Three phototoxic compounds were tested. Acridine and 8-methoxypsoralen (8-MOP) were transdermally administered, and 8-MOP and lomefloxacin were orally administered. The animals were allocated to three groups for each compound: single-dose, repeated-dose, and repeated-dose plus toxicokinetics (TK). The single-dose group was irradiated with UV-A and UV-B after a single administration of the drug. The repeated-dose and TK groups were irradiated after 8 days of repeated administration of the drug. Blood samples were also collected from the TK group on days 1 and 7 after administration. The phototoxic compounds resulted in skin reactions in all the groups, with no difference in the degree of skin reaction among the three groups. In the TK measurements, all of the phototoxic compounds were detected in the plasma samples, and the irradiation timing was close to the Tmax. These results indicate that phototoxic potential could be evaluated in the TK group, and phototoxicity assessments could be incorporated into general toxicology studies. This reduces the number of studies and animals required, thus shortening the research and development period, and supporting the 3Rs principle of animal experiments. The study also provides information regarding appropriate irradiation timings, differences between the sexes, and dose-response, in turn enabling the phototoxic risk of the compounds to be clearly evaluated.

Pharmaceutical development of an amorphous solid dispersion formulation of elacridar hydrochloride for proof-of-concept clinical studies.

OBJECTIVE: A novel tablet formulation containing an amorphous solid dispersion (ASD) of elacridar hydrochloride was developed with the purpose to resolve the drug's low solubility in water and to conduct proof-of-concept clinical studies. SIGNIFICANCE: Elacridar is highly demanded for proof-of-concept clinical trials that study the drug's suitability to boost brain penetration and bioavailability of numerous anticancer agents. Previously, clinical trials with elacridar were performed with a tablet containing elacridar hydrochloride. However, this tablet formulation resulted in poor and unpredictable absorption which was caused by the low aqueous solubility of elacridar hydrochloride. METHODS: Twenty four different ASDs were produced and dissolution was compared to crystalline elacridar hydrochloride and a crystalline physical mixture. The formulation with highest dissolution was characterized for amorphicity. Subsequently, a tablet was developed and monitored for chemical/physical stability for 12 months at +15-25 °C, +2-8 °C and -20 °C. RESULTS: The ASD powder was composed of freeze dried elacridar hydrochloride-povidone K30-sodium dodecyl sulfate (1:6:1, w/w/w), appeared fully amorphous and resulted in complete dissolution whereas crystalline elacridar hydrochloride resulted in only 1% dissolution. The ASD tablets contained 25 mg elacridar hydrochloride and were stable for at least 12 months at -20 °C. CONCLUSIONS: The ASD tablet was considered feasible for proof-of-concept clinical studies and is now used as such.

Clinical pharmacokinetics of an amorphous solid dispersion tablet of elacridar.

Elacridar is an inhibitor of the permeability glycoprotein (P-gp) and the breast cancer resistance protein (BCRP) and is a promising absorption enhancer of drugs that are substrates of these drug-efflux transporters. However, elacridar is practically insoluble in water, resulting in low bioavailability which currently limits its clinical application. We evaluated the in vitro dissolution and clinical pharmacokinetics of a novel amorphous solid dispersion (ASD) tablet containing elacridar. The dissolution from ASD tablets was compared to that from a crystalline powder mixture in a USP type II dissolution apparatus. The pharmacokinetics of the ASD tablet were evaluated in an exploratory clinical study at oral doses of 25, 250, or 1000 mg in 12 healthy volunteers. A target Cmax was set at ≥ 200 ng/mL based on previous clinical data. The in vitro dissolution from the ASD tablet was 16.9 ± 3.7 times higher compared to that from a crystalline powder mixture. Cmax and AUC0-∞ increased linearly with dose over the explored range. The target Cmax of ≥ 200 ng/mL was achieved at the 1000-mg dose level. At this dose, the Cmax and AUC0-∞ were 326 ± 67 ng/mL and 13.4 ± 8.6 · 103 ng · h/mL, respectively. In summary, the ASD tablet was well tolerated, resulted in relevant pharmacokinetic exposure, and can be used for proof-of-concept clinical studies.

Pyrrolidine-Acridine hybrid in Artemisinin-based combination: a pharmacodynamic study.

Aiming to develop new artemisinin-based combination therapy (ACT) for malaria, antimalarial effect of a new series of pyrrolidine-acridine hybrid in combination with artemisinin derivatives was investigated. Synthesis, antimalarial and cytotoxic evaluation of a series of hybrid of 2-(3-(substitutedbenzyl)pyrrolidin-1-yl)alkanamines and acridine were performed and mode of action of the lead compound was investigated. In vivo pharmacodynamic properties (parasite clearance time, parasite reduction ratio, dose and regimen determination) against multidrug resistant (MDR) rodent malaria parasite and toxicological parameters (median lethal dose, liver function test, kidney function test) were also investigated. 6-Chloro-N-(4-(3-(3,4-dimethoxybenzyl)pyrrolidin-1-yl)butyl)-2-methoxyacridin-9-amine (15c) has shown a dose dependent haem bio-mineralization inhibition and was found to be the most effective and safe compound against MDR malaria parasite in Swiss mice model. It displayed best antimalarial potential with artemether (AM) in vitro as well as in vivo. The combination also showed favourable pharmacodynamic properties and therapeutic response in mice with established MDR malaria infection and all mice were cured at the determined doses. The combination did not show toxicity at the doses administered to the Swiss mice. Taken together, our findings suggest that compound 15c is a potential partner with AM for the ACT and could be explored for further development.

Whole-Body Distribution and Radiation Dosimetry of 11C-Elacridar and 11C-Tariquidar in Humans.

UNLABELLED: (11)C-elacridar and (11)C-tariquidar are new PET tracers to assess the transport activity of P-glycoprotein (adenosine triphosphate-binding cassette subfamily B, member 1 [ABCB1]) and breast cancer resistance protein (adenosine triphosphate-binding cassette subfamily G, member 2 [ABCG2]). This study investigated the whole-body distribution and radiation dosimetry of both radiotracers in humans. METHODS: Twelve healthy volunteers (6 women, 6 men) underwent whole-body PET/CT imaging over the 90 min after injection of either (11)C-elacridar or (11)C-tariquidar. Radiation doses were calculated with OLINDA/EXM software using adult reference phantoms. RESULTS: Biodistribution was consistent with a major elimination route of hepatobiliary excretion, which may be mediated by ABCB1 and ABCG2. High radioactivity uptake was seen in liver, followed by spleen and kidneys, whereas brain uptake was lowest. Effective doses were 3.41 ± 0.06 µSv/MBq for (11)C-elacidar and 3.62 ± 0.11 µSv/MBq for (11)C-tariquidar. CONCLUSION: Our data indicate that both (11)C-elacridar and (11)C-tariquidar are safe radiotracers, for which an injected activity of 400 MBq corresponds to a total effective dose of approximately 1.5 mSv.

Pilot PET Study to Assess the Functional Interplay Between ABCB1 and ABCG2 at the Human Blood-Brain Barrier.

ABCB1 and ABCG2 work together at the blood-brain barrier (BBB) to limit brain distribution of dual ABCB1/ABCG2 substrates. In this pilot study we used positron emission tomography (PET) to assess brain distribution of two model ABCB1/ABCG2 substrates ([(11) C]elacridar and [(11) C]tariquidar) in healthy subjects without (c.421CC) or with (c.421CA) the ABCG2 single-nucleotide polymorphism (SNP) c.421C>A. Subjects underwent PET scans under conditions when ABCB1 and ABCG2 were functional and during ABCB1 inhibition with high-dose tariquidar. In contrast to the ABCB1-selective substrate (R)-[(11) C]verapamil, [(11) C]elacridar and [(11) C]tariquidar showed only moderate increases in brain distribution during ABCB1 inhibition. This provides evidence for a functional interplay between ABCB1 and ABCG2 at the human BBB and suggests that both ABCB1 and ABCG2 need to be inhibited to achieve substantial increases in brain distribution of dual ABCB1/ABCG2 substrates. During ABCB1 inhibition c.421CA subjects had significantly higher increases in [(11) C]tariquidar brain distribution than c.421CC subjects, pointing to impaired cerebral ABCG2 function.

Direct detection of the anti-cancer drug 9-phenylacridine in tissues by graphite rod laser desorption vacuum-ultraviolet post-ionization mass spectrometry.

RATIONALE: Traditionally, drug analysis in biological tissue by mass spectrometry has required complicated sample pre-treatment, which not only wasted time, but also had adverse effects on the results. In order to assist assessment of potential drugs rapidly and accurately, a direct analytical method for drug detection in tissues is needed. The development of such a method is described in this study. METHODS: An anti-cancer drug, 9-phenylacridine (ACPH), injected into the kidney of mice, was directly analysed from tissues placed on the surface of a graphite rod by near-infrared (1064 nm) laser desorption single photon ionization mass spectrometry (LD/SPI-MS). RESULTS: The LD/SPI-MS method was successfully validated by direct analysis of ACPH in kidney sections of mice, without any complicated and time-consuming sample pre-treatment. The sensitivity of detection was down to about 100 fmol per spot and the wide linear dynamic range allowed quantitative detection of ACPH in complex biological samples. A drug-time curve was acquired of ACPH in the kidney of mice after the drug had been injected into the caudal vein. CONCLUSIONS: It was demonstrated that the anti-tumor drug ACPH could be directly and rapidly detected by LD/SPI-MS in biological tissues without any time-consuming pre-treatment procedure. This method could potentially be applied to the selective localization and analysis of small molecule drugs in tissues and to the study of the pharmacokinetics of new drugs.

Liposomes Coloaded with Elacridar and Tariquidar To Modulate the P-Glycoprotein at the Blood-Brain Barrier.

This study prepared three liposomal formulations coloaded with elacridar and tariquidar to overcome the P-glycoprotein-mediated efflux at the blood-brain barrier. Their pharmacokinetics, brain distribution, and impact on the model P-glycoprotein substrate, loperamide, were compared to those for the coadministration of free elacridar plus free tariquidar. After intravenous administration in rats, elacridar and tariquidar in conventional liposomes were rapidly cleared from the bloodstream. Their low levels in the brain did not improve the loperamide brain distribution. Although elacridar and tariquidar in PEGylated liposomes exhibited 2.6 and 1.9 longer half-lives than free elacridar and free tariquidar, respectively, neither their Kp for the brain nor the loperamide brain distribution was improved. However, the conjugation of OX26 F(ab')2 fragments to PEGylated liposomes increased the Kps for the brain of elacridar and tariquidar by 1.4- and 2.1-fold, respectively, in comparison to both free P-gp modulators. Consequently, the Kp for the brain of loperamide increased by 2.7-fold. Moreover, the plasma pharmacokinetic parameters and liver distribution of loperamide were not modified by the PEGylated OX26 F(ab')2 immunoliposomes. Thus, this formulation represents a promising tool for modulating the P-glycoprotein-mediated efflux at the blood-brain barrier and could improve the brain uptake of any P-glycoprotein substrate that is intended to treat central nervous system diseases.

ABCB1, ABCG2, and PTEN determine the response of glioblastoma to temozolomide and ABT-888 therapy.

PURPOSE: Little is known about the optimal clinical use of ABT-888 (veliparib) for treatment of glioblastoma. ABT-888 is a PARP inhibitor undergoing extensive clinical evaluation in glioblastoma, because it may synergize with the standard-of-care temozolomide (TMZ). We have elucidated important factors controlling ABT-888 efficacy in glioblastoma. EXPERIMENTAL DESIGN: We used genetically engineered spontaneous glioblastoma mouse models and allograft models that were orthotopically transplanted into wild-type (WT) and Abcb1/Abcg2-deficient (KO) recipients. RESULTS: ABT-888/TMZ is not efficacious against p53;p16(Ink4a)/p19(Arf);K-Ras(v12);LucR allografts in wild-type recipients, indicating inherent resistance. Abcb1/Abcg2 mediated efflux of ABT-888 at the blood-brain barrier (BBB) causes a 5-fold reduction of ABT-888 brain penetration (P < 0.0001) that was fully reversible by elacridar. Efficacy studies in WT and KO recipients and/or concomitant elacridar demonstrate that Abcb1/Abcg2 at the BBB and in tumor cells impair TMZ/ABT-888 combination treatment efficacy. Elacridar also markedly improved TMZ/ABT-888 combination treatment in the spontaneous p53;p16(Ink4a)/p19(Arf);K-Ras(v12);LucR glioblastoma model. Importantly, ABT-888 does enhance TMZ efficacy in Pten deficient glioblastoma allografts and spontaneous tumors, even in Abcb1/Abcg2 proficient wild-type mice. Loss of PTEN occurs frequently in glioblastoma (36%) and in silico analysis on patient with glioblastoma samples revealed that it is associated with a worse overall survival (310 days vs. 620 days, n = 117). CONCLUSIONS: The potential of ABT-888 in glioblastoma can best be demonstrated in patients with PTEN null tumors. Therefore, clinical trials with ABT-888 should evaluate these patients as a separate group. Importantly, inhibition of ABCB1 and ABCG2 (by elacridar) may improve the efficacy of TMZ/ABT-888 therapy in all glioblastoma patients.

Saturable active efflux by p-glycoprotein and breast cancer resistance protein at the blood-brain barrier leads to nonlinear distribution of elacridar to the central nervous system.

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.