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Ahnfelt, Emelie
(author)
In vitro evaluation of formulations used in the treatment of hepatocellular carcinoma
2018
Doctoral thesis (other academic/artistic) abstract
Hepatocellular carcinoma (HCC) causes ~ 600,000 deaths annually, making it the second most deadly cancer form. HCC is classified into five stages and for the intermediate HCC treatment, the two most commonly used drug delivery systems (DDSs) are lipiodol-based emulsions and drug-eluting beads. The aims of this thesis were to develop in vitro methods suitable for studying these DDSs. It is important to investigate the release mechanisms and release rates with relevant in vitro methods, as this can improve the understanding of the in vivo performance. Miniaturized in vitro methods with sample reservoirs separated from the release medium by a diffusion barrier were developed and shown to be suitable for studying drug release from particle DDSs (Paper I). In Paper II these methods were further developed and used to study the release of doxorubicin (DOX) from the clinically used drug-eluting beads. DOX release rates were affected by the method set-up and the characteristics of the release medium. The choice of method and volume of release medium could improve the in vivo-likeness of the in vitro release profiles. Applied theoretical models suggested a film-controlled type of DOX release mechanism from the beads when self-aggregation, DOX-bead interaction, and DOX deprotonation were taken into account.A micropipette-assisted microscopy method was used to further improve the understanding of the release mechanism of amphiphilic molecules from the beads (Paper III). A detailed analysis suggested an internal depletion-layer model dependent on molecular self-aggregation for the release. It was further suggested that a simple ion-exchange mechanism is unrealistic in physiological conditions.The important pharmaceutical factors for the emulsion-based formulations were investigated in Paper IV. DOX solubility, lipid phase distribution, and emulsion stability increased when the contrast agent iohexol was added. Also, an increase in release half-life (h) was observed from emulsions with iohexol.The in vitro methods and theoretical models presented in this thesis can be used during development and optimization of future DDSs.
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Ayoun Alsoud, Rami, et al.
(author)
Model-based interspecies scaling for predicting human pharmacokinetics of CB 4332, a complement factor I protein
Other publication (other academic/artistic) abstract
The extrapolation of a protein pharmacokinetics (PK) from preclinical to clinical studies can be less reliable than for small molecules. CB 4332 is a 150 kDa recombinant complement factor I (CFI) protein. In order to support clinical development, interspecies scaling of CB 4332 using traditional and model-based approaches was performed to inform first-in-human (FIH) dose selection. Plasma concentration versus time data from four preclinical PK studies of single intravenous (i.v.) and subcutaneous (s.c.) CB 4332 dosing in mice, rats and nonhuman primates (NHPs) were modeled simultaneously using naive pooling including allometric scaling. The human-equivalent dose was calculated using the preclinical no observed adverse effect level (NOAEL) as part of the dose-by-factor approach. Pharmacokinetic modelling of CB 4332 revealed species-specific differences in the elimination, which was accounted for by including an additional rat-specific clearance. Signs of anti-drug antibodies (ADA) formation in all rats and some NHPs were observed. Consequently, an additional ADA-induced clearance parameter was estimated including the time of onset. Using the traditional dose-by-factor approach, a maximum recommended starting s.c. dose of 0.9 mg/kg once weekly was calculated using the NOAEL observed in NHPs. The model-based clinical trial simulations predicted it to result in a trough concentration at steady state 12.8% of the determined efficacy target for CB 4332 in humans. Interspecies scaling was performed for CB 4332 using traditional and model-based scaling, where PK modeling allowed the inclusion of preclinical PK information from three species, accounted for potential effects of ADA and species differences in elimination, and allowed the prediction of human PK for FIH dose selection.
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Bergman, Ebba, 1977-
(author)
The Hepatobiliary Transport of Rosuvastatin In Vivo
2009
Doctoral thesis (other academic/artistic) abstract
In vivo studies of hepatobiliary disposition are challenging. The hepatobiliary system is complex, as its physiological localization, complex cellular structure with numerous transporters and enzymes, and the interindividual variability in protein expression and biliary flow will all affect the in vivo disposition of a drug under investigation. The research included in this thesis has focused on the involvement of hepatic transport proteins in the hepatobiliary disposition of rosuvastatin. The impact that several transport inhibitors had on the pharmacokinetics of rosuvastatin was investigated in healthy volunteers and in pigs. The effects were considerable, following inhibition of sinusoidal transport proteins by cyclosporine and rifampicin. These inhibitors significantly reduced the hepatic extraction of rosuvastatin by 50 and 35%, respectively, and the plasma exposure increased by factors of 9.1 and 6.3, respectively. Drug-drug interactions (DDI) resulting in markedly higher plasma exposures are important from a drug safety perspective as increased extrahepatic exposure of statins is associated with an increased risk of severe side-effects, such as myopathy which in rare cases could develop into rhabdomyolysis. The DDI caused by cyclosporine and rifampicin can probably be attributed to inhibition of hepatic uptake transporters. In contrast, inhibition of canalicular transporters by imatinib did not significantly affect the pharmacokinetics of rosuvastatin, which suggests that the intracellular concentration of the inhibitor in the hepatocyte was insufficient to affect the transport of rosuvastatin, or that imatinib is not a sufficiently potent inhibitor in vivo. Furthermore, gemfibrozil administered as a single dose into the jejunum in healthy volunteers and pigs did not affect the plasma or biliary pharmacokinetics of rosuvastatin. The previously reported DDI in humans upon repeated dosing with gemfibrozil might be explained by the accumulation of metabolites able to affect the disposition of rosuvastatin. The investigations presented in this thesis conclude that transport proteins are of considerable importance for the hepatobiliary disposition of rosuvastatin in vivo. The Loc-I-Gut catheter can be applied for the investigation of biliary accumulation and to determine bile specific metabolites, however it has limitations when conducting quantitative measurements. In the porcine model, hepatic bile can be collected for up to six hours and enables the determination of the hepatic extraction in vivo.
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Carlert, Sara, et al.
(author)
Evaluation of the use of Classical Nucleation Theory for predicting intestinal crystallization of two weakly basic BCS class II drugs
Other publication (other academic/artistic) abstract
The aim of this work was to evaluate an in vitro-in silico approach for prediction of small intestinal crystallization of two weakly basic model BCS class II drugs, AZD0865 and mebendazole, and the effect crystallization would have on the absorption prediction of the drug. The crystallization rates were investigated in an in vitro method using simulated gastric and intestinal media, and the result was modeled by using Classical Nucleation Theory (CNT). The effect of varying in vitro parameters (initial drug concentration, rate of mixing gastric and intestinal fluid, stirring and filtration) on the interfacial tension g, being a key parameter in CNT, was investigated. The initial drug concentration had the most significant effect on g for both substances tested, although g is a fundamental parameter independent of concentration according to CNT. In the subsequent in silico prediction of drug absorption an empirical approach was used where g was predicted at expected in vivo small intestinal concentrations. The results showed that lack of crystallization effects on absorption in man of the model drug AZD0865 up to doses of 4 mg/kg could be predicted. Mebendazole intestinal precipitation in canines was also well described by the model, where mean predicted amount precipitated was 111% (range 41-166%) of measured solid amount, and mean predicted supersaturation was 106% (range 73-118%) of measured supersaturation. The plasma concentration of mebendazole after duodenal administration of a solution could not be predicted by the model with the same precision in the absence of measured intestinal drug concentrations as basis for estimating the g value. In conclusion, the in vitro-in silico approach can be used for predictions of absorption effects of crystallization, but the model could benefit from further development work on the theoretical crystallization model and in vitro experimental design.
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Carlert, Sara, 1977-
(author)
Investigation and Prediction of Small Intestinal Precipitation of Poorly Soluble Drugs : a Study Involving in silico, in vitro and in vivo Assessment
2012
Doctoral thesis (other academic/artistic) abstract
The main objectives of the present project were to increase the understanding of small intestinal precipitation of poorly soluble pharmaceutical drugs, investigate occurrence of crystalline small intestinal precipitation and effects of precipitation on absorption. The aim was to create and evaluate methods of predicting crystalline small intestinal drug precipitation using in vivo, in vitro and in silico models.In vivo small intestinal precipitation from highly supersaturated solutions of two weakly basic model drugs, AZD0865 and mebendazole, was investigated in humans and canine models. Potential precipitation of AZD0865 was investigated by examining dose dependent increases in human maximum plasma concentration and total exposure, which turned out to be dose linear over the range investigated, indicating no significant in vivo precipitation. The small intestinal precipitation of mebendazole was investigated from drug concentrations and amount of solid drug present in dog jejunum as well as through the bioavailability after direct duodenal administration in dogs. It was concluded that mebendazole small intestinal precipitation was limited, and that intestinal supersaturation was measurable for up to 90 minutes.In vitro precipitation methods utilizing simulated or real fasted gastric and intestinal fluids were developed in order to simulate the in vivo precipitation rate. The methods overpredicted in vivo precipitation when absorption of drug was not simulated. An in vitro-in silico approach was therefore developed, where the in vitro method was used for determining the interfacial tension (γ), necessary for describing crystallization in Classical Nucleation Theory (CNT). CNT was evaluated using a third model drug, bicalutamide, and could successfully describe different parts of the crystallization process of the drug. CNT was then integrated into an in silico absorption model. The in vivo precipitation results of AZD0865 and mebendazole were well predicted by the model, but only by allowing the fundamental constant γ to vary with concentration. Thus, the in vitro-in silico approach could be used for small intestinal precipitation prediction if the in vitro concentration closely matched in vivo small intestinal concentrations.
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Dahlgren, David
(author)
Biopharmaceutical aspects of intestinal drug absorption : Regional permeability and absorption-modifying excipients
2018
Doctoral thesis (other academic/artistic) abstract
Before an orally administered drug reaches the systemic circulation, it has to dissolve in the intestinal fluids, permeate across the intestinal epithelial cell barrier, and pass through the liver. The permeation rate of drug compounds can be low and show regional differences.The thesis had two general aims. The first of these was, to determine and compare regional intestinal permeability values of model compounds in human and dog. The second was to understand the possible effects of absorption-modifying pharmaceutical excipients (AMEs) on the intestinal permeability of the model compounds. The usefulness of several preclinical animal models for predicting the impact of regional intestinal permeability and AMEs in human was also investigated.There was a good correlation between human and dog permeability values in the small intestines for the model compounds. The colon in dog was substantially more permeable than the human colon to the low permeability drug, atenolol. This difference in colonic permeability may have implications for the use of dog as a model species for prediction of human intestinal drug absorption.There were no effects of AMEs on the intestinal permeability of any of the high permeability compounds, in any animal model. In the rat single-pass intestinal perfusion model, there was a substantial increase in permeability of all low permeability drugs, induced by two AMEs, chitosan and SDS. This AME-induced increase was substantially lower in the more in vivo relevant rat and dog intraintestinal bolus models. A shorter AME exposure-time in the rat single-pass intestinal perfusion model (15 vs. 75 min) could, however, predict the result from the bolus studies in rat and dog. This illustrates the impact of intestinal transit and mucosal exposure time on AME effects in vivo. The intestinal luminal conditions and enteric neural activity also had an impact on determinations of drug permeability in the rat single-pass intestinal perfusion model, which can have implications for its in vivo relevance.In summary, this thesis used multiple in vivo models to evaluate the impact of several biopharmaceutical processes on intestinal drug absorption. This has led to an increased understanding of these absorption mechanisms.
