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The application of Göttingen minipigs for non-rodent pharmacokinetics (PK) and drug safety testing has seen a dramatic increase in recent years. The aim of this study was to determine the total and unbound brain-to-plasma ratios (K p,brain and K p,uu,brain ) for a diverse set of reference compounds in female Göttingen minipigs and compare these with K p,uu,brain values from other species to assess the suitability of Göttingen minipigs as a model for CNS drug safety testing and brain PK in clinical translation. The reference set consisted of 17 compounds with varying physico-chemical properties and included known human P-glycoprotein (P-gp) substrates. The results of the study showed, that minipig K p,brain and K p,uu,brain values for the tested compounds were in the range 0.03-86 and 0.02-2.4 (n = 3-4) respectively. The K p,uu,brain values were comparable between minipig and rat for a large proportion of the compounds (71% within 2-fold, n = 17). Comparisons of brain penetration across several species for a subset of reference compounds revealed that minipig values were quite similar to those of rat, dog, monkey and human. The study highlighted that the largest K p,uu,brain species differences were observed for compounds classified as transporter substrates (e.g. cimetidine, risperidone, Way-100635 and altanserin). In conclusion these brain penetration data add substantially to the available literature on PK and drug disposition for minipigs and support use of Göttingen minipig as a non-rodent drug safety model for CNS drug candidates and as a brain PK model for clinical translation., (Copyright © 2023. Published by Elsevier B.V.)

Niraparib (Zejula), a selective oral PARP1/2 inhibitor registered for ovarian, fallopian tube, and primary peritoneal cancer treatment, is under investigation for other malignancies, including brain tumors. We explored the impact of the ABCB1 and ABCG2 multidrug efflux transporters, the OATP1A/1B uptake transporters, and the CYP3A drug-metabolizing complex on oral niraparib pharmacokinetics, using wild-type and genetically modified mouse and cell line models. In vitro , human ABCB1 and mouse Abcg2 transported niraparib moderately. Compared to wild-type mice, niraparib brain-to-plasma ratios were 6- to 7-fold increased in Abcb 1 a /1 b -/- and Abcb 1 a /1 b ; Abcg 2 -/- but not in single Abcg mice, while niraparib plasma exposure at later time points was ∼2-fold increased. Niraparib recovery in the small intestinal content was markedly reduced in the Abcb1a/1b-deficient strains. Pretreatment of wild-type mice with oral elacridar, an ABCB1/ABCG2 inhibitor, increased niraparib brain concentration and reduced small intestinal content recovery to levels observed in -/- mice, while niraparib plasma exposure at later time points was ∼2-fold increased. Niraparib recovery in the small intestinal content was markedly reduced in the Abcb1a/1b-deficient strains. Pretreatment of wild-type mice with oral elacridar, an ABCB1/ABCG2 inhibitor, increased niraparib brain concentration and reduced small intestinal content recovery to levels observed in Abcb 1 a /1 b ; Abcg 2 -/- mice. Oatp1a/1b deletion did not significantly affect niraparib oral bioavailability or liver distribution but decreased metabolite M1 liver uptake. No significant effects of mouse Cyp ablation were observed, but overexpression of transgenic human CYP3A4 unexpectedly increased niraparib plasma exposure. Thus, Abcb1 deficiency markedly increased niraparib brain distribution and reduced its small intestinal content recovery, presumably through reduced biliary excretion and/or decreased direct intestinal excretion. Elacridar pretreatment inhibited both processes completely. Clinically, the negligible role of OATP1 and CYP3A could be advantageous for niraparib, diminishing drug-drug interaction or interindividual variation risks involving these proteins. These findings may support the further clinical development and application of niraparib.a ablation were observed, but overexpression of transgenic human CYP3A4 unexpectedly increased niraparib plasma exposure. Thus, Abcb1 deficiency markedly increased niraparib brain distribution and reduced its small intestinal content recovery, presumably through reduced biliary excretion and/or decreased direct intestinal excretion. Elacridar pretreatment inhibited both processes completely. Clinically, the negligible role of OATP1 and CYP3A could be advantageous for niraparib, diminishing drug-drug interaction or interindividual variation risks involving these proteins. These findings may support the further clinical development and application of niraparib.

Purpose: Panobinostat, an orally bioavailable pan-HDAC inhibitor, has demonstrated potent activity in multiple malignancies, including pediatric brain tumors such as DIPG, with increased activity against H3K27M mutant cell lines. Given limited evidence regarding the CNS penetration of panobinostat, we sought to characterize its BBB penetration in a murine model., Methods: Panobinostat 15 mg/kg was administered IV to 12 CD-1 female mice. At specified time points, mice were euthanized, blood samples were collected, and brains were removed. LC-MS was performed to quantify panobinostat concentrations. C max and AUC were estimated and correlated with previously published pharmacokinetic analyses and reports of IC-50 values in DIPG cell lines., Results: Mean panobinostat plasma concentrations (ng/mL) were 27.3 ± 2.5 at 1 h, 7.56 ± 1.8 at 2 h, 1.48 ± 0.56 at 4 h, and 2.33 ± 1.18 at 7 h. Mean panobinostat brain concentrations (ng/g) were 60.5 ± 6.1 at 1 h, 42.9 ± 5.4 at 2 h, 33.2 ± 6.1 at 4 h, and 28.1 ± 4.3 at 7 h. Brain-to-plasma ratio at 1 h was 2.22 and the brain to plasma AUC ratio was 2.63. Based on the published human pharmacokinetic data, the anticipated C max in humans is expected to be significantly higher than the IC-50 identified in DIPG models., Conclusion: It is expected that panobinostat would be effective in CNS tumors where the IC-50 is in the low nanomolar range. Thus, our data demonstrate panobinostat crosses the BBB and achieves concentrations above the IC-50 for DIPG and other brain tumors and should be explored further for clinical efficacy., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Phosphodiesterase 7 (PDE7) is an enzyme responsible for the degradation of cyclic adenosine monophosphate (cAMP), an important cellular messenger. PDE7's role in neurotransmission, expression profile in the brain and the druggability of other phosphodiesterases have motivated the search for potent inhibitors to treat neurodegenerative and inflammatory diseases. Different heterocyclic compounds have been described over the years; among them, phenyl-2-thioxo-( 1H )-quinazolin-4-one, called S14, has shown very promising results in different in vitro and in vivo studies. Recently, polymeric nanoparticles have been used as new formulations to target specific organs and produce controlled release of certain drugs. In this work, we describe poly(lactic-co-glycolic acid) (PLGA)-based polymeric nanoparticles loaded with S14. Their preparation, optimization, characterization and in vivo drug release profile are here presented as an effort to improve pharmacokinetic properties of this interesting PDE7 inhibitor.

Tivozanib is a potent and selective inhibitor of VEGFR1-3, recently approved by the EMA for first-line treatment of renal cell carcinoma. We used wild-type, knockout, and transgenic mouse strains to study the effects of the drug transporters ABCB1, ABCG2, and OATP1A/1B, and of the CYP3A enzymes on the oral availability and tissue distribution of tivozanib. Tivozanib was transported by human ABCB1 and mouse Abcg2 in polarized MDCK-II cells. Upon oral administration, tivozanib showed rapid absorption and the plasma concentration-time curves showed secondary peaks in all mouse strains, suggesting enterohepatic recirculation. The brain-to-plasma ratios were significantly increased in Abcb1a/1b -/- (2.2-fold) and Abcb1a/1b;Abcg2 -/- (2.6-fold) mice compared to wild-type mice, indicating a modest protective role of these transporters in the blood-brain barrier. Slco1a/1b -/- mice showed a 1.2-fold lower liver-to-plasma ratio than wild-type mice, suggesting a minor role of mOatp1a/1b in tivozanib liver distribution. Oral plasma pharmacokinetics of tivozanib was not significantly altered in these mouse strains, nor in Cyp3a knockout and CYP3A4-humanized mice. The modest effect of ABC transporters on tivozanib brain accumulation, if also true in humans, might mean that this drug is not strongly limited in its therapeutic efficacy against malignant lesions situated partly or completely behind the blood-brain barrier., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A novel oxime platform, the substituted phenoxyalkyl pyridinium oximes (US patent 9,227,937), was invented at Mississippi State University with an objective of discovering a brain-penetrating antidote to highly potent organophosphate anticholinesterases, such as the nerve agents. The goal was reactivation of inhibited brain acetylcholinesterase to attenuate the organophosphate-induced hypercholinergic activity that results in glutamate-mediated excitotoxicity and neuropathology. The currently approved oxime antidote in the US, 2-PAM, cannot do this. Using highly relevant surrogates of sarin and VX that leave acetylcholinesterase phosphylated with the same chemical moiety as their respective nerve agents, in vitro screens and in vivo tests in rats were conducted to identify the most efficacious members of this platform. The most promising novel oximes provided 24-h survival of lethal level surrogate exposure better than 2-PAM in almost all cases, and two of the oximes shortened the time to cessation of seizure-like behavior while 2-PAM did not. The most promising novel oximes attenuated neuropathology as indicated by immunohistochemical stains for both glia and neurons, while 2-PAM did not protect either glia or neurons. These results strongly suggest that these novel oximes can function within the brain to protect it, and therefore show great promise as potential future nerve agent antidotes., (Copyright © 2019 Elsevier Inc. All rights reserved.)

It is of great challenge to predict human brain penetration for substrates of multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP), 2 major efflux transporters at blood-brain barrier. Thus, a physiologically based pharmacokinetic (PBPK) model with the incorporation of in vitro MDR1 and BCRP transporter function data and transporter protein expression levels has been developed. As such, it is crucial to generate MDR1 and BCRP substrate data with a high fidelity. In this study, 2 widely used human MDR1 cell lines from Borst and National Institutes of Health laboratories were evaluated using rodent brain penetration data, and the study suggested that the MDR1 expressed in Madin-Darby canine kidney (MDCK) cell line from National Institutes of Health laboratory predicted brain penetration better, particularly for compounds with a high passive permeability. In addition, human BCRP-MDCK cell line with 1 μM PSC833, a specific MDR1 inhibitor, demonstrated the ability to identify BCRP substrates without the confounding of endogenous canine Mdr1. Comparison of human BCRP and mouse Bcrp transporter functions revealed that the functional differences of BCRP between the 2 species is minimal. The incorporation of both the validated MDR1 and BCRP assays into our brain PBPK model has significantly improved the prediction for the brain penetration of MDR1 and BCRP substrates across species., (Copyright © 2019 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

1. The present study is designed to investigate the brain distribution and plasma pharmacokinetics profiles of chlorogenic acid (CGA) after intranasal administration in Charles-Foster rats to evaluate whether the CGA molecules are transported directly via the nose-to-brain path. 2. The CGA is administered intravenously (IV) and intranasally (IN) at the dose of 10 mg/kg. Further, its concentration in the plasma, cerebrospinal fluid (CSF) and the whole brain is analyzed by HPLC-UV method. 3. The study observes that CGA is rapidly absorbed in plasma with t max of 1 min similar to IV route after IN administration. The peak plasma concentration and AUC 0-24 are higher by 3.5 and 4.0 times respectively in IV administration, compared to IN delivery that represents the significant less systemic exposure of CGA in IN route. 4. However, the concentration of CGA in the brain is 4, 6.5, 5.3, 5.2 and 4.5 times higher at 30, 60, 120, 240 and 360 min, respectively in IN administration compared to IV administration. The exposure of CGA in the brain after IN administration (AUC brain, IN ) was significantly greater (4 times) as compared to the exposure of CGA in the brain (AUC brain, IV ) after IV administration reflecting significant brain uptake of CGA through nasal route. Therefore, IN delivery of CGA can be a promising approach for the treatment of stroke and neurodegenerative disorders.

Quizartinib, a second-generation FLT3 inhibitor, is in clinical development for the treatment of acute myeloid leukemia. We studied its pharmacokinetic interactions with the multidrug efflux transporters ABCB1 and ABCG2 and the multidrug metabolizing enzyme CYP3A, using in vitro transport assays and knockout and transgenic mouse models. Quizartinib was transported by human ABCB1 in vitro, and by mouse (m)Abcb1 and mAbcg2 in vivo. Upon oral administration, the brain accumulation of quizartinib was 6-fold decreased by mAbcb1 and 2-fold by mAbcg2 (together: 12-fold). Unexpectedly, the absence of mAbcb1 resulted in a ∼2-fold lower plasma exposure in Abcb1a/1b -/- and Abcb1a/1b;Abcg2 -/- mice, suggesting that loss of mAbcb1 causes compensatory alterations in alternative quizartinib elimination or uptake systems. mAbcb1 and mAbcg2 themselves did not appear to restrict quizartinib oral availability. Oral and intravenous pharmacokinetics of quizartinib were not substantially altered between wild-type, Cyp3a knockout and CYP3A4-humanized mice. All three strains showed relatively high (33-51%) oral bioavailability. If this also applies in humans, this would suggest a limited risk of CYP3A-related inter-individual variation in exposure for this drug. Our results provide a possible rationale for using pharmacological ABCB1/ABCG2 inhibitors together with quizartinib when treating malignant lesions situated in part or in whole behind the blood-brain barrier., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Encorafenib (LGX818) is a promising BRAF V600E inhibitor that has efficacy against metastatic melanoma. To better understand its pharmacokinetics, we studied its interactions with the multidrug efflux transporters ABCB1 and ABCG2 and the multidrug metabolizing enzyme CYP3A. In polarized MDCK-II cells, encorafenib was efficiently transported by canine and human ABCB1 and ABCG2 and by mouse Abcg2. Upon oral administration to wild-type, Abcb1a/1b -/- , Abcg2 -/- , and Abcb1a/1b;Abcg2 -/- mice, encorafenib was absorbed very quickly and to very high plasma levels, but without clear changes in oral availability between the strains. Upon oral or intravenous administration, encorafenib brain accumulation was markedly increased in Abcb1a/1b;Abcg2 -/- mice and to a lesser extent in Abcb1a/1b -/- mice. However, absolute brain concentrations and brain-to-plasma ratios remained very low in all strains, indicating intrinsically poor brain penetration of encorafenib. Upon intravenous administration, Abcb1a/1b;Abcg2 -/- mice showed somewhat reduced plasma elimination of encorafenib compared to wild-type mice, and lower accumulation of the drug in the intestinal tract, suggesting a limited role for these transporters in intestinal elimination of the drug. In Cyp3a -/- mice plasma levels of encorafenib were not markedly increased, suggesting a limited impact of Cyp3a on encorafenib oral availability. The low brain penetration of encorafenib might limit its efficacy against malignancies positioned behind a functional blood-brain barrier, but its oral bioavailability and distribution to other tested organs (liver, kidney, spleen, testis) was high., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The blood-brain barrier (BBB) maintains the integrity and homeostasis of the central nervous system (CNS) yet represents an intimidating hurdle for efficient drug delivery to brain tumors. This up-to-date review summarizes strategies that have been employed to cross the BBB with a focus on non-invasive nanoparticles that could pass the BBB after systemic administration. Recent advances in liposomes, polymeric nanoparticles, micelles, and inorganic nanoparticles are scrutinized mechanistically with an emphasis on design principles. As highlighted in this review, effective drug delivery to brain tumors may be achieved by rationally engineering nanoparticles to possess appropriate sizes, surface properties, and ligands., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Introduction: Adult zebrafish pharmacology is evolving rapidly for creating efficacy and safety models for drug discovery. However, there is very limited research in understanding pharmacokinetics (PK) in adult zebrafish. Methods for understanding PK will help in conducting pharmacokinetic - pharmacodynamic (PK-PD) correlations and improving the quality and applicability of data obtained using zebrafish., Methods: We conducted adult zebrafish PK and brain penetration studies on two known compounds (irinotecan and lorcaserin) with distinct PK and brain penetration properties using validated LCMS/MS method. Irinotecan was studied at a dose of 100mg/kg i.p. and levels of the parent drug and active metabolite SN-38 were measured. Loracserin was studies at a dose of 10mg/kg by two routes i.p. and p.o., Results: Zebrafish PK and brain penetration profiles for both compounds were very similar to that of higher mammals including humans. Irinotecan was metabolised to SN-38 in ratios similar to ratios seen in other species and the compound had long half life with very low brain penetration in our studies. Loracasin was highly permeable in brain as compared to the exposure in blood, with long half life and high relative bioavailability, similar to other mammalian species including humans., Discussion: Adult zebrafish PK studies are relatively an unexplored area of zebrafish research. The zebrafish data for key parameters of irinotecan and loracserin shows a high correlation to the data from higher species, including human. This report explores and discusses the use of adult zebrafish as a predictive PK tool for higher animal studies., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Hypothermic circulatory arrest (HCA) provides neuroprotection during cardiac surgery but entails an ischemic period that can lead to excitotoxicity, neuroinflammation, and subsequent neurologic injury. Hydroxyl polyamidoamine (PAMAM) dendrimers target activated microglia and damaged neurons in the injured brain, and deliver therapeutics in small and large animal models. We investigated the effect of dendrimer size on brain uptake and explored the pharmacokinetics in a clinically-relevant canine model of HCA-induced brain injury. Generation 6 (G6, ~6.7nm) dendrimers showed extended blood circulation times and increased accumulation in the injured brain compared to generation 4 dendrimers (G4, ~4.3nm), which were undetectable in the brain by 48h after final administration. High levels of G6 dendrimers were found in cerebrospinal fluid (CSF) of injured animals with a CSF/serum ratio of ~20% at peak, a ratio higher than that of many neurologic pharmacotherapies already in clinical use. Brain penetration (measured by drug CSF/serum level) of G6 dendrimers correlated with the severity of neuroinflammation observed. G6 dendrimers also showed decreased renal clearance rate, slightly increased liver and spleen uptake compared to G4 dendrimers. These results, in a large animal model, may offer insights into the potential clinical translation of dendrimers., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A comparative study of classification models of brain penetration by different approaches was carried out on a training set of 1000 chemicals and drugs, and an external test set of 100 drugs. Ten approaches were applied in this work: seven medicinal chemistry approaches (including "rule of 5" and multiparameter optimization) and also three SAR techniques: logistic regression (LR), random forest (RF) and support vector machine (SVM). Forty-one different medicinal chemistry descriptors representing diverse physicochemical properties were used in this work. Medicinal chemistry approaches based on the intuitive estimation of preference zones of CNS or non-CNS chemicals, with different rules and scoring functions, yield unbalanced models with poor classification accuracy. RF and SVM methods yielded 82% and 84% classification accuracy respectively for the external test set. LR was also successful in CNS/non-CNS (denoted in this study as CNS+/CNS-) classification and yielded an overall accuracy equivalent to that of SVM and RF. At the same time, LR is especially valuable for medicinal chemists because of its simplicity and the possibility of clear mechanistic interpretation.

An adverse effect associated with the administration of carbapenems is central nervous system (CNS) toxicity, with higher brain concentrations of carbapenems being linked to an increased risk of seizures. However, the pharmacokinetics and brain penetration of carbapenems have not yet been examined. Thus, the aim of this in vivo investigation was to determine the pharmacokinetics and brain penetration of carbapenems in mice. Blood samples and brain tissue samples were obtained 10, 20, 30, 60, and 120 min after the subcutaneous administration of carbapenems (91 mg/kg). We obtained the following values for the pharmacokinetic parameters of carbapenems in mice: 1.20-1.71 L/h/kg for CLtotal/F, 1.41-2.03 h(-1) for Ke, 0.34-0.51 h for T1/2, 0.66-0.95 L/kg for Vss/F, 0.49-0.73 h for MRT, 83.46-110.58 μg/mL for Cmax, plasma, and 0.28-0.83 μg/g for Cmax, brain tissue. The AUC0-∞ of the carbapenems tested in plasma were in the following order: doripenem > meropenem > biapenem > imipenem, and in brain tissue were: imipenem > doripenem > meropenem > biapenem. The degrees of brain tissue penetration, defined as the AUC0-∞, brain tissue/fAUC0-∞, plasma ratio, were 0.016 for imipenem, 0.004 for meropenem, 0.002 for biapenem, and 0.008 for doripenem. The results of the present study demonstrated that, of the carbapenems examined, imipenem penetrated brain tissue to the greatest extent., (Copyright © 2015 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Background: Near-infrared spectroscopy (NIRS) is a non-invasive technique that monitors changes in oxygenation of haemoglobin. The absorption spectra of near-infrared light differ for the oxygenation-deoxygenation states of haemoglobin (oxygenate (HbO2) and deoxygenate (Hb), respectively) so that these two states can be directly monitored., Comparison With Existing Method(s): Different methodologies report different basal values of HbO2 and Hb absolute concentrations in brain. Here, we attempt to calculate basal HbO2 levels in rat CNS via evaluation of the influence of exogenous oxygen or exogenous carbon dioxide on the NIRS parameters measured in vivo., New Method: Furthermore the possibility that changes of haemoglobin oxygenation in rat brain as measured by NIRS might be a useful index of brain penetration of chemical entities has been investigated. Different compounds from different chemical classes were selected on the basis of parallel ex vivo and in vivo pharmacokinetic (PK/PD) studies of brain penetration and overall pharmacokinetic profile., Results: It appeared that NIRS might contribute to assess brain penetration of chemical entities, i.e. significant changes in NIRS signals could be related to brain exposure, conversely the lack of significant changes in relevant NIRS parameters could be indicative of low brain exposure., Conclusions: This work is proposing a further innovation on NIRS preclinical applications i.e. a "chemical" NIRS [chNIRS] approach for determining penetration of drugs in animal brain. Therefore, chNIRS could became a non invasive methodology for studies on neurobiological processes and psychiatric diseases in preclinical but also a translational strategy from preclinical to clinical investigations., (Copyright © 2015 Elsevier B.V. All rights reserved.)

BAF312 (siponimod) is a sphingosine-1-phosphate (S1P) receptor modulator in clinical development for the treatment of multiple sclerosis, with faster organ/tissue distribution and elimination kinetics than its precursor FTY720 (fingolimod). Our aim was to develop a tracer to better quantify the penetration of BAF312 in the human brain, with the potential to be labeled for positron emission tomography (PET) or single-photon emission computed tomography (SPECT). Although the PET radioisotopes (11)C and (18)F could have been introduced in BAF312 without modifying its structure, they do not have decay kinetics compatible with the time required for observing the drug's organ distribution in patients. In contrast, the SPECT radioisotope (123) I has a longer half-life and would suit this purpose. Herein we report the identification of an iodinated derivative of BAF312, (E)-1-(4-(1-(((4-cyclohexyl-3-iodobenzyl)oxy)imino)ethyl)-2-ethylbenzyl)azetidine-3-carboxylic acid (18, MS565), as a SPECT tracer candidate with affinity, S1P receptor selectivity, overall physicochemical properties, and blood pharmacokinetics similar to those of the original molecule. A whole-body autoradiography study performed with [(14)C]MS565 subsequently confirmed that its organ distribution is similar to that of BAF312. This validates the selection of MS565 for (123)I radiolabeling and for use in imaging studies to quantify the brain penetration of BAF312., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cobimetinib is a MEK inhibitor currently in clinical trials as an anticancer agent. The objectives of this study were to determine in vitro and in vivo if cobimetinib is a substrate of P-glycoprotein (P-gp) and/or breast cancer resistance protein (Bcrp1) and to assess the implications of efflux on cobimetinib pharmacokinetics (PK), brain penetration, and target modulation. Cell lines transfected with P-gp or Bcrp1 established that cobimetinib was a substrate of P-gp but not a substrate of Bcrp1. In vivo, after intravenous and oral administration of cobimetinib to FVB (wild-type; WT), Mdr1a/b(-/-), Bcrp1 (-/-), and Mdr1a/b(-/-)/Bcrp(-/-) knockout (KO) mice, clearance was similar in WT (35.5 ± 16.7 mL/min/kg) and KO animals (22.0 ± 3.6 to 27.6 ± 5.2 mL/min/kg); oral exposure was also similar between WT and KO animals. After an oral 10 mg/kg dose of cobimetinib, the mean total brain to plasma ratio (Kp) at 6 h postdose was 0.3 and 0.2 in WT and Bcrp1(-/-) mice, respectively. In Mdr1a/b(-/-) and Mdr1a/1b/Bcrp1(-/-) KO mice and WT mice treated with elacridar (a P-gp and BCRP inhibitor), Kp increased to 11, 6, and 7, respectively. Increased brain exposure in Mdr1a/b(-/-) and Mdr1a/1b/Bcrp1(-/-) KO and elacridar treated mice was accompanied by up to ∼65% suppression of the target (pErk) in brain tissue, compared to WT mice. By MALDI imaging, the cobimetinib signal intensity was relatively high and was dispersed throughout the brain of Mdr1a/1b/Bcrp1(-/-) KO mice compared to low/undetectable signal intensity in WT mice. The efflux of cobimetinib by P-gp may have implications for the treatment of patients with brain tumors/metastases.

Background: For CNS drugs, brain disposition is of critical importance during drug discovery. In vitro methods are used early followed by more predictive in vivo methods later on in the drug discovery process. Current in vivo methods are costly, have long turnover times or do not measure brain disposition at steady state., New Method: A new method to evaluate drug brain disposition in vivo was developed in anaesthetized rats. Seven reference compounds were administered as an initial IV bolus (loading dose) followed by IV infusion for 4.5 h in order to obtain a steady state plasma concentration before brain sampling. The loading dose was estimated from a preliminary single dose IV pharmacokinetic study and was found to successfully bring plasma concentrations to steady state for compounds exhibiting either mono- or bi-compartmental pharmacokinetics., Results: Using this method, a steady state lasting at least 2h was obtained, thus making the in vivo method robust with respect to differences in the pharmacokinetics and/or blood-to-brain equilibration rate of the compounds tested. The method produced highly reproducible results, with substantial advantages in terms of cost, turnaround time and animal welfare., Comparison With Existing Methods: The results agreed with those reported in other, more elaborate preclinical models and in humans, enabling brain disposition to be assessed in a simple, efficient and robust in vivo model for new chemical entities., Conclusions: Introducing the presented method in drug discovery allows brain disposition to be assessed earlier in the drug discovery pipeline and thus facilitate the selection of potent and penetrant CNS drugs., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Here I detail the use of measures of permeability rate and solubility in predicting drug disposition characteristics through the utilization of the Biopharmaceutics Drug Disposition Classification System (BDDCS) and the Extended Clearance Classification System (ECCS) as well as the accuracy of the systems in predicting the major route of elimination and the extent of oral absorption of a new small molecule therapeutics. I compare the BDDCS and ECCS with the FDA Biopharmaceutics Classification System (BCS). I also detail the use of the BCS in predicting food effects and the BDDCS in predicting brain disposition of small molecule therapeutics and in validating DILI predictive metrics. This review provides an update of the current status of these classification systems and their uses in the drug development process.

Abstract: Aim: Recently, sildenafil was reported to be an inhibitor of P-glycoprotein (P-gp/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) in vitro. We have now investigated the in vivo potency of sildenafil. Methods: By using wild-type and Abcb1;Abcg2 knockout mice we have investigated the effect of sildenafil on the brain penetration of two substrate drugs (docetaxel and topotecan). Next we have investigated if sildenafil was able to improve the efficacy of doxorubicin against P-glycoprotein expressing CT26 colon cancer cells in syngeneic Balb/c mice. Results: Sildenafil administered orally at a dose of 50mg/kg did not improve the brain penetration of docetaxel and topotecan, although the plasma level of sildenafil was already much higher than can be achieved in humans. On the other hand, sildenafil increased the plasma levels of the cytotoxic drugs, but not by inhibition of Abcb1 or Abcg2, since this effect was also seen in Abcb1;Abcg2 knockout mice. The brain penetration of sildenafil was more than 20-fold higher in Abcb1;Abcg2 mice versus wild-type mice, indicating that sildenafil is a good substrate of the two transporters. Sildenafil was also not able to improve the efficacy of doxorubicin against subcutaneous CT26 tumours. The doxorubicin level in tumour tissue did increase, but so did the concentration of doxorubicin in plasma and heart. Conclusion: These results demonstrate that the potency and specificity of sildenafil as an inhibitor of ABCB1 and ABCG2 is not sufficient to warrant further clinical testing of this agent in combination with anticancer drugs. [Copyright &y& Elsevier]

Abstract: The only method to quantify free extracellular levels of drugs in the brain of living animals is microdialysis. However, quantitative microdialysis has been hampered by methodological issues for decades. The problems arise from the need to establish the in vivo recovery for appropriate quantitation. In dealing with these issues the “dynamic no-net-flux” (DNNF) method seemed to be the experimental method of choice. Major disadvantages were, however, the need for a very high degree of bioanalytical precision and accuracy and the need for a large number of animals. Moreover, today we know that the experimental data are not always straightforward. To improve robustness and practicality of quantitative microdialysis sampling we modified the ultraslow microdialysis approach. Ultraslow microdialysis uses very low microdialysis flow rates (<200nl/min) which increase recovery (both in vivo and in vitro) to over 90%. However, new practical issues arise when attempting to work with these flow rates. The resulting very low volumes and long lag times make this method very impractical for general application. In the modified version, addition of a carrier flow after the dialysis process has been completed, which negates the problems of long lag times and low volumes. The resulting dilution of the dialysis sample concentration can simply be mathematically corrected. In the current study we measured the free brain levels of two CNS compounds using the classic DNNF and the new modified ultraslow dialysis method. Modified ultraslow microdialysis was shown to generate robust data with the use of only small numbers of rats. The method is a promising tool for common straightforward screening of blood–brain barrier penetration of compounds into the brain. [Copyright &y& Elsevier]

This review examines the progress that is being made towards the in silico prediction of brain permeation. Following a brief introduction to the blood–brain barrier, the datasets currently available for in silico modeling are discussed. Recent developments in in silico models of brain permeation are summarized in the context of the current state of the art in prediction accuracy. An analysis of recent models is presented, focusing on what such models reveal about the molecular properties that determine brain permeation. The review concludes by presenting the current key issues in this area of research, noting in particular, the paucity of brain permeation data available for modeling. Finally, possible future directions are suggested. [Copyright &y& Elsevier]