Mechanobiology is an emerging field that aims to understand how physical forces regulate cell function, morphology, and development. Cells interpret forces, such as the deformation of the membrane to encapsulate a particle, or the rigidity of the extracellular matrix (ECM), and make decisions about cell adhesion, motility, and differentiation. These cell-ECM interactions are important to maintaining homeostasis, and the disruption of this interface has pathological consequences. Common diseases, such as Alzheimer’s disease, cancer, and atherosclerosis each arise, in part, from an abnormality in the mechanotransduction pathway. Hence, understanding the contribution of this pathway and the role of the ECM in cell function, proves to be a useful tool in improving drug targeting and understanding disease progression. While size, shape and surface chemistry of nanoparticle uptake has been extensively studied, varying the particle mechanics can also be a useful design strategy to manipulate particles and improve uptake and targeting. Using model polystyrene-co-N-isopropylacrylamide (pS-co-NIPAM) particles, with varying elastic moduli, it was observed that as the particles became stiffer, there was a subsequent decrease in bound/internalized particles for phagocytic RAW264.7 macrophage and non-phagocytic HepG2 hepatoma carcinoma cells, showing that both of these cell types are sensitive to particle mechanics, even in a higher stiffness regime (MPa). ECM mechanics have recently been implicated in tissue stiffness changes that precede and drive disease development. Recent research has started looking into these effects in the progression of neurodegenerative diseases. This research found that the elasticity of the brain becomes softer with aging, and even softer in patients with AD. Analogous to the pS-co-NIPAM studies, this tissue softening could have implications on amyloid-beta endocytosis as well as neuron dystrophy in response to the peptide. Understanding the role of the ECM in the progression of AD in vitro could provide a better approach to determine an in vivo mechanism behind Alzheimer’s disease pathology. In order to mimic a softer ECM substrate, SH-SY5Y neuroblastoma and human primary neurons were plated on 2-D polyacrylamide and 3-D collagen gels with varying stiffness ranging from 0.15-25kPa. Both cell types grown using these substrates show a sensitivity to their ECM environment, and display an increase in cell spreading and the number of F-actin stress fibers with an increase in substrate rigidity. Moreover, the extent of Aβ internalization and aggregate production increased with ECM stiffness for SH-SY5Y neuroblastoma. Intracellular Aβ processing remains a central question to understanding the early-stage events in AD pathogenesis. As the ECM can modify Aβ endocytosis and aggregation, the ECM is likely influencing downstream neurotoxic effects of AD. Despite an increase in the plaque production on the soft substrates, both SH-SY5Y neuroblastoma and primary neurons showed a decreased toxicity to Aβ with decreasing substrate stiffness. This decrease in toxicity is associated with cytoskeletal actin remodeling, as cells plated on plastic, but pretreated with cytochalasin D displayed a recovery in viability in response to the oligomeric species. The softening of the ECM initiates actin cytoskeletal depolymerization, as a protective mechanism against neuronal loss and AD progression. This work demonstrates that the ECM impacts Aβ endocytosis and aggregation, and the ECM prompts neuroprotective actin reorganization against the neurotoxic effects of AD. Further, it is demonstrated the biophysical role of ECM stiffness in modifying Aβ internalization, plaque production, and toxicity offers an improved in vitro model of critical AD components. By better understanding the cytoskeletal reorganization triggered by a softening ECM, potential novel avenues of therapeutic intervention could later be determined to stop the progression of the disease.

Artemisinin compounds are the most potent anti-malarial drugs available in the market. Today, malaria treatment is largely relies on the artemisinin-based combination therapies. Artesunate (AS) is the most widely used artemisinin derivative. In this thesis, we characterized the population pharmacokinetics of AS and its active metabolite dihydroartemisinin (DHA) following oral administration of AS in different populations. In Chapter II, we developed a population pharmacokinetic model of AS and DHA in healthy subjects. These subjects received either single- or multiple-dosing of oral AS, as a monotherapy regimen or in combination with pyronaridine, with or without food. In Chapter III, we developed a population pharmacokinetic model of AS and DHA in adult and pediatric patients with uncomplicated falciparum and vivax malaria who were administered oral pyronaridine/artesunate combination once daily for 3 days. We modeled the AS and DHA data simultaneously using a parent-metabolite model that assumed complete conversion of AS to DHA. Following oral administration, AS is rapidly absorbed with maximum concentrations reached at about 0.5 hours post-dose. AS is rapidly converted to DHA. DHA then undergoes rapid metabolism, with an elimination half-life of about 0.8 hours in malarial patients. Inter-individual variability for almost all pharmacokinetic parameters and residual variability for both compounds were estimated by the models. Substantial variability was seen in the pharmacokinetic parameters between the subjects. In healthy subjects, intake of food with the dose was found to delay the absorption of AS significantly, but not the extent of absorption. Weight was also included in this model as a determinant of DHA clearance. When modeling the data from patients, we included weight as part of the model a prioria priori using an established allometric function. No other covariates examined in the analysis were statistically significant. The performance of final models was evaluated using non-parametric bootstrap technique and visual predictive check. The models were found to adequately described the data at hand, and robust with sufficient predictive power. The results can be used as the base to develop a population pharmacokinetic-pharmacodynamic model and as prior information in guiding the selection of optimal sampling schedule for future pharmacokinetic studies of AS.

The drug metoclopramide was found to adsorb to the unionized and ionized silica surface. The primary objective of this research was to use potentiometric titration in order to study the specificity of the interactions of benzamide analogs with the hydroxyl groups, silanols, on the Aeroperl® silica surface. Mass titration studies showed that the acidity of surface silanols increases with dissolved metoclopramide and similar compounds. The nature of the interaction was concluded to involve a physical adsorption process. A different potentiometric titration method was devised to determine the ionization of silanols in the presence of a dissolved compound with solubility limitations. This method was found to give similar results as that described in the literature. The presence of dissolved metoclopramide was found to cause a large increase in the density of the negatively charged silanols on the silica surface. The ionization of silica was dependent on the concentration of dissolved metoclopramide at low pH but was found to be constant over a wide concentration range at pH 7.0 or higher. Adsorption studies with unionized silica indicated that specific interactions with the surface silanols occur as well as non-specific interactions driven by hydrophobic bonding with the surface siloxane groups. There was an increase in the adsorption of metoclopramide with increasing ionization of the silica surface which suggested that the negatively charged silanols constituted an additional adsorption site. The mechanism of the interaction was elucidated by potentiometric titration with various probe compounds. The titration data with lidocaine suggested that the ionization of the surface silanols is influenced by specific interactions with the adsorbed compound rather than concentration effects. The ionized site density of silica was found to be related to the relative magnitude of the aromatic π-electron density of the adsorbed benzamides. A comparison of these titration data with that of triethylamine indicated that ionic interactions between the positively charged amine groups and the negatively charged silanols are likely to be occurring. Based on the difference in chemical structure, the titration data with dissolved ephedrine indicated that the other site of interaction is likely to be between the carbonyl oxygen of the adsorbed benzamides and the unionized silanols. The pH dependence of the ionization of silanols for both adsorption sites suggested that silanols interact simultaneously with several functional groups on a single adsorbed molecule.

Cognitive decline is increasingly recognized as a side effect of chemotherapy. However, cognitive decline doesn't occur in all patients receiving chemotherapy, and there is variability in the cognitive domains affected (Ahles; JCO,Oct 20, 2012:3675-3686). Safety pharmacogenomics, i.e. using genetic variations to predict response/toxicity, offers an exciting approach to identify the subset of patients most likely to suffer from cognitive decline post chemotherapy. Consequently specific therapeutic interventions can be developed to target this group of patients, and/or alternate chemotherapeutic regimens can be used to limit toxicity, thereby offering a way to individualize therapy while minimizing toxicity. In our research we studied the effect of 16 SNPs in 6 genes on cognition in a sample of healthy older adults. We found that SNPs that affect serotonin, dopamine and glutamate levels in the brain influence cognition in a healthy sample of older adults, possibly in a domain specific manner. This allowed us to identify a group of healthy adults who inherently have lower cognitive functioning in some domains but that is still within the normal range. In addition individuals with SNPs that previously were associated with lower levels of myeloperoxidase performed better on the executive functions, verbal memory, verbal IQ and IQ. SNPs associated with lower levels were also associated with improvement in self reported verbal and visual memory post chemotherapy. APOE E2 allele was associated with higher cognitive performance compared to other alleles. However we didn't see an effect of APOE post chemotherapy. In chapter five, the effects of 31 SNPs in 15 genes on cognition post chemotherapy were evaluated in community dwelling lymphoma patients. Changes in the domains of verbal memory, visual perceptual memory, and attention of the Multiple Ability Self Report Questionnaire were observed following chemotherapy, but only when groups were stratified by genotype. Contrary to what we might expect, patients showed improvements in function after chemotherapy. However, using patient stratification based on genotype, specific groups of patients had a measurable decline in cognitive function post chemotherapy. Interestingly a SNP in the DNA replication enzyme and the target of doxorubicin topoisomerase II was associated with varying degree of self reported attention; specifically the AA genotype of rs471692 was associated with statistically significant decline in attention post chemotherapy. This indicates that cognitive changes following chemotherapy can be subtle, and stratification by genotype helps us in identifying susceptible individuals and provides some insights on the inconsistencies that are frequently reported in the literature. These results allow for identifying genetic risk factors associated with chemotherapy-induced cognitive changes, which will ultimately help in developing therapeutic approaches for the management of those deficits. Strategies to avoid chemotherapy-induced cognitive changes will be prospectively evaluated in future studies and include alternative chemotherapy and less toxic regimens, intervention strategies to improve cognitive abilities, and drug therapy to improve cognition in patients who develop chemotherapy-induced cognitive changes. The overarching goals of our studies are to help improve cancer patients' quality of life while maintaining or improving cancer cure rates.

Geographic access to cancer care is an important dimension of quality of cancer care. Previous studies have shown that the more uncertain medical evidence is, the more geographic variation is observed in the medical care utilization that is attributable to local care health care system capacity and local area patient/physician preferences. Chemotherapy for metastatic breast cancer (MBC) is such a case. Although clinical trials have proven the efficacy of chemotherapy in treating MBC, whether to treat elderly MBC patients with chemotherapy is uncertain because of the underrepresentation of elderly patients in the clinical trials. As age advances, uncertainties increase due to competing causes of death, limited life expectancy, and higher risk of toxicities. As a result, geographic access may matter more in chemotherapy choice for older patients than for younger patients. Literature has shown that older patients are less likely to be treated with chemotherapy. In this study, we examined the effect of access to cancer care on age-related difference in chemotherapy use for elderly MBC patients. Access to cancer care is measured by four variables, including travel time to the nearest oncologist practice, local area per capita number of oncologists among stage IV cancer patients, local area per capita number of hospices among stage IV cancer patients, and local area chemotherapy percentage among stage IV cancer patients. The retrospective cohort study used the 1992-2002 SEER-Medicare database. Chemotherapy use was defined as at least one chemotherapy-related claim within 6 months post diagnosis. To examine the age variant effect of access on chemotherapy choice, the analysis adopted both interaction term approach and subgroup analysis. In interaction term analysis, product term between age and access dummy variables were specified in the multivariate logistic regression model controlling for other covariates; in subgroup analysis, age subgroups were specified consistently with interaction term approach. For each age subgroup, we used multivariate logistic regression to estimate the effect of access to cancer care on immediate chemotherapy use controlling for covariates. Among 4533 elderly patients with MBC, 30.16% used chemotherapy. Chemotherapy rate decreased with age. Interaction term approach did not show significant interaction between age and access in each specification. Both interaction term and subgroup analysis showed that the local area treatment rate was positively associated with immediate chemotherapy use across patient age. In addition, subgroup analysis showed among patients who were 85+ years old, the local area oncologist supply was negatively associated with chemotherapy use. This effect was not observed among younger age groups. Our results suggest that estimating all patients in one equation with dummies and interactions can hide results. By estimating each group separately, subgroup analysis showed that provider access is paramount for age subgroup 85 years or older. Our access measures suggest that access to cancer care affects chemotherapy choice among elderly patients whose clinical evidence is uncertain. This can be attributable to local practice style and physician concern of real benefits of chemotherapy. The local area chemotherapy practice styles affect chemotherapy choice for patients across age except patients aged between 80 to 84 years old; provider access plays an important role for patients 85 years or older. The more certain the evidence with age, the more access may affect chemotherapy choice.

Purpose: Ivermectin (IVM) is a lipophilic BCS-II compound (molecular weight=875 g/mole, LogP=3.22, intrinsic solubility=700 ug/L). IVM is used as antiparasitic drug in both humans and animals. IVM is known to have a half-life of 12-56 hours in humans. Strongyloidiasis is a chronic parasitic infection of humans caused by Strongyloides stercoralis, with an estimated 30-100 million people infected worldwide. Infection may be severe and even life-threatening in cases of immunodeficiency. Patients with disseminated strongyloidiasis are usually bedridden hospitalized patients that show symptoms such as paralytic ileus and reduced plasma albumin and cholesterol. Oral IVM is the only FDA-approved treatment but may not be effective in patients with disseminated disease. Veterinary subcutaneous formulations have been used in severe infections. We hypothesized that IVM PK in patients with disseminated strongyloidiasis can be predicted using PBPK model originally built and refined in healthy human and animal species. This hypothesis was tested and shown to be valid. Methods:A systematic method was used to build and refine different parts of the PBPK model. The process involved construction of models, parameterization of these models, evaluation of the effect of uncertainty in model parameters on model prediction via local and global sensitivity analyses and finally, refinement of model predictions. Two disposition models that differ in the rate limiting step in drug distribution were constructed and include perfusion-limited and permeability-limited distribution models. The ability of each model to predict IVM disposition was evaluated using plasma PK data in rat after intra-arterial dosing and in dog after intravenous bolus dosing. Then the disposition model was scaled to humans and an oral input model was constructed as a modification on the well-known ACAT model. The oral input model was coupled with the disposition model and used to predict IVM plasma concentration-time profile in healthy fasted human subject after oral dosing. Two subcutaneous (SQ) input models were constructed and used to evaluate the effect of IVM precipitation at the injection site. Plasma PK data in dog after SQ dosing was used to refine the constructed SQ input models. The refined disposition, oral input and SQ input physiologically-based models were used to predict IVM PK in patients with disseminated strongyloidiasis after a complex dosing regimen. The physiological parameters of the model were modified to account for the effect of the disease-induced pathophysiological changes on the body physiology and hence on the drug PK. Plasma PK data from hospitalized subjects with disseminated strongylidiasis was used in this part. Results and conclusions:The disposition model with assumption of permeability-limited distribution was more capable of describing IVM disposition in rat after intra-arterial dosing compared to when perfusion-limited distribution was assumed. The model predicted that hepatic clearance is the most impactful parameter on model-predicted plasma concentration of the drug. Also, IVM was shown to have low hepatic extraction ratio along with high binding in plasma and large volume of distribution, which collectively may explain the long half-life in the plasma of 63 hours in rat after intra-arterial dosing. The oral input model predicted that the oral input is limited by drug dissolution in the GI lumen and that a very small fraction of oral tablet dose (0.03) is available in the systemic circulation in healthy fasted human subjects. Both of the studied SQ input models predicted that majority of IVM absorption after SQ dosing is via the lymphatic route and that drug precipitation at the injection site can further slowdown the drug absorption after SQ administration. The PBPK model was able achieve the main goal of this research which is to predict IVM pharmacokinetics in patients with disseminated strongyloidiasis after a complex dosing regimen of multiple oral and SQ dosing. This was achieved by modifying the most impactful physiological parameters of the model affected by the disease state and that are related to drug binding in the plasma (fraction unbound), the GI motility (gastric emptying rate) and the lymphatic flow rate. Based on our analysis, we recommend measurement of plasma IVM concentrations early after initiation of therapy to exclude treatment failure due to reduced oral and/or SQ absorption. Also, we recommend measurement of plasma lipoprotein levels and their composition in these patients to differentiate between low total plasma concentrations due to low binding plasma as opposed to low drug input. Finally, interventional procedures that enhance lymphatic flow rate to site of SQ injection are recommended to enhance SQ absorption.

Medication related problems occur frequently and can be difficult to predict. Medication monitoring by health care providers allows for problems to be identified before they become severe. Medication monitoring is an an emerging role for community pharmacists. This mixed methods study examines pharmacist perspectives on medication monitoring. Study methods included 12 semi-structured interviews, a mixed methods item generation process to create a pharmacist medication motioning attitude measure, and mailed factorial survey designed to assess pharmacist decision making related to asking non-adherence, side effect, and effectiveness questions for randomly generated refill dispensing vignettes. Hierarchical linear modeling was used to identify significant vignette level and pharmacist level variables associated with likelihood to ask the three monitoring questions. The qualitative analysis showed barriers to medication monitoring including time limitations, busyness, low patient expectation, and a perceived routine nature of refills by both patients and pharmacists. Monitoring non-adherence was a challenge because workflows often do not make non-adherence apparent to the pharmacists when the patient presents to the pharmacy. Lastly, monitoring interactions often are precipitated by "gateway conversations" which begin as technical or cost issues related to the prescription but then progress to monitoring issues when the patient reflects interest. Analysis of the survey showed in general, pharmacists had positive medication monitoring attitudes and worked in pharmacies somewhat conducive to medication monitoring, although there was variation. The factorial survey showed pharmacist monitoring attitudes were significantly associated with the likelihood to ask all three monitoring question types. For the different prescriptions involved, warfarin and hydrocodone were significantly associated with asking monitoring questions whereas fluoxetine and metoprolol appeared less question-worthy. The number of days late was associated with greater question asking likelihood suggesting days late is an important activator for pharmacist medication monitoring. Number of patients waiting was a barrier. This study shows community pharmacists are oriented to monitoring, but there are significant barriers which need to be addressed when advancing this role.

Artemisinin derivatives are key to the current global treatment approach for malaria. However, much remains unknown regarding the pharmacokinetics of these agents, particularly in children and pregnant women, two groups highly vulnerable to development of severe malaria infection. In this thesis, nonlinear mixed effects modeling is used to characterize the pharmacokinetics of the artemisinin derivative artesunate and its active metabolite, dihydoartemisinin (DHA), in children and in pregnant women. Chapter 1 of this thesis contains a general review of the clinical pharmacokinetic findings for artesunate and DHA following artesunate administration by the intravenous, intramuscular, oral and rectal routes. Chapter 2 presents a population pharmacokinetic model utilizing both pediatric and adult data from one Phase II and four Phase III clinical trials evaluating the combination agent pyronaridine tetraphosphate/artesunate. The focus of the modeling described in this chapter is the evaluation of the effects of body size and gender on the pharmacokinetics of artesunate and DHA in pediatric patients with uncomplicated malaria. Chapter 3 consists of a population pharmacokinetic model built utilizing plasma artesunate and DHA concentrations from 26 parasitemic second and third trimester pregnant women and 25 parasitemic non-pregnant female controls in the Democratic Republic of Congo who received 200 mg oral artesunate. The model described in Chapter 2 is a simultaneously implemented parent-metabolite model consisting of a one compartment model for artesunate, a one compartment model for DHA, and first-order artesunate absorption. Various approaches for incorporating body size on artesunate and DHA apparent clearance and volume of distribution parameters were evaluated, with a linear body surface area model and an allometric scaling model both proving satisfactory. The effect of gender was modeled on artesunate and DHA apparent clearance and volume terms. Only the effect of gender on DHA apparent clearance could be estimated with reasonable precision, with the 95% confidence interval for the effect being almost wholly contained within the predefined 0.75 to 1.25 no relevant clinical effect interval. The model described in Chapter 3 consists of a one compartment model for artesunate, a one compartment model for DHA, and mixed zero-order, lagged first order absorption of artesunate. In this model, pregnancy was found to have a marked effect on DHA apparent clearance, with a pregnancy-associated increase in DHA apparent clearance of 42.3%. The models described in this thesis indicate that, for a given mg/kg dose of artesunate, both young children and pregnant women would be expected, on average, to display lower DHA concentrations than would be observed following administration of the same mg/kg dose to non-pregnant adults. Suboptimal dosing has clinical implications for the individual as well as potential implications regarding parasite susceptibility. Given this, the findings of the research described in this thesis highlight the necessity of investigations designed to comprehensively characterize the pharmacokinetics of artesunate and DHA in these two highly susceptible populations.

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