The majority of pharmaceutical products are formulated as solids in the crystalline state. With the potential to exist in different crystalline modifications or polymorphs, each solid form bears its own physical and chemical properties, influencing directly bioavailability and manufacturability of the final dosage form. In view of the importance of crystalline form selection in the drug development process, it is imperative for pharmaceutical scientists to work arduously on various aspects of polymorphism, ranging from fundamental understanding of the phenomenon at the molecular level to practical utilization of a specific crystalline form. One common feature of organic crystals is the existence of distinct molecular conformations in different polymorphic structures, known as conformational polymorphism. Conformational polymorphs are routinely observed in drug development, produced when crystal growth conditions vary. Crystallization from solution involves nucleation and crystal growth, the mechanisms that influence the polymorphic outcome. The embryonic solute aggregate has been recognized to play a critical role in dictating the final crystal structure, and solution conditions are also known to drastically influence the self-association behavior of solute molecules during crystallization, affecting crystal packing of organic molecules. For the crystal growth of conformational polymorphs, changes in molecular conformation not only determine the growth kinetics, but also influence the nature and strength of interactions present in the crystal structures. How conformation and intermolecular interaction affect each other underlines the intricacy and the wonder of crystal growth of the organic. Thus, the overall goal of this research is to provide the fundamental understanding of the extent to which solution conditions influence the molecular conformation in the solid-state of a model drug, tolfenamic acid. By combining experimental studies with advanced computational tools, this dissertation offers novel insights into solution species during pre-nucleation and molecular packing of conformational polymorphs of tolfenamic acid. In-depth understanding of the underlying connection between molecular conformation and crystal packing will help advance the knowledge required for rational control of crystal growth.

Microneedles are a minimally invasive method for delivering drugs through the impermeable skin layers, and have been used to deliver a variety of compounds including macromolecules, vaccines, and naltrexone. Microneedles can be applied to the skin once, creating micropores that allow for drug delivery into the underlying circulation from a drug formulation. The utility of this technique, however, is blunted by rapid micropore closure. This research project sought to: 1) characterize micropore lifetime and re-sealing kinetics, and 2) prolong micropore lifetime via inhibition of the skin’s barrier restoration processes. Impedance spectroscopy was used as a surrogate technique in animals and humans to measure micropore formation and lifetime. A proof of concept study in humans, using impedance spectroscopy, demonstrated that diclofenac (a topical anti-inflammatory) applied to microporated skin resulted in slower re-sealing kinetics compared to placebo, in agreement with previous animal studies. The clinical feasibility of prolonging micropore lifetime with diclofenac was confirmed via 7-day delivery of naltrexone through microneedle treated skin in humans (compared to 72 hour delivery with placebo). Lastly, naltrexone gels with calcium salts were applied to microneedle treated skin (hairless guinea pigs) to restore the altered epidermal calcium gradient; this method did not significantly extend micropore lifetime.

The organic anion transporting polypeptide 4c1 (Oatp4c1) was previously identified as a novel uptake transporter predominantly expressed at the basolateral membrane in the rat kidney proximal tubules. Its functional role was suggested to be a vectorial transport partner of an apically-expressed efflux transporter for the efficient translocation of physiological substrates into urine, some of which were suggested to be uremic toxins. In vitro studies in polarized cell lines showed that upon transfection rat Oatp4c1 localizes at the apical membrane. The objectives of this project were to further validate the subcellular localization of Oatp4c1/OATP4C1 in rat and human tissues as well as their localization and function in polarized cells. Using several complementary biochemical, molecular and proteomic methods as well as antibodies amenable to immunohistochemistry, immunofluorescence, and immunoblotting, we investigated the expression pattern of Oatp4c1 in epithelial cell lines and in the rat kidney and mammary gland (MG). Collectively, these data demonstrated that rat Oatp4c1 localized at the apical cell surface of polarized epithelium and primarily in the proximal straight tubules, the S3 segment of proximal tubule, in the juxtamedullary cortex. Drug uptake studies in Oatp4c1-expressing cells demonstrated that Oatp4c1- mediated estrone-3-sulfate (E3S) uptake was ATP-independent and pH-dependent. The increased E3S transport activity at acidic extracellular pH was ascribed to the increased maximum transport rate (Vmax). In addition, E3S transport inhibition by various substrates suggests that Oatp4c1 possesses multiple substrate binding sites. The apical localization of Oatp4c1 in the rat kidney and MG is a novel finding and implies that this transporter protein plays a role in the reabsorption, not vectorial secretion, of its substrates. In addition, the upregulation of Oatp4c1 expression during lactation indicates that it is involved in reuptake of xenobiotic from the milk, resulting in their reduced exposure to the suckling infants, or that it functions as a scavenger system. Further, studies to identify physiological substrates are needed to better understand the significance of Oatp4c1 function in renal and mammary epithelium.

Patients with cystic fibrosis who are infected with the pathogen Pseudomonas aeruginosa have shown favorable responses to the drug azithromycin (AZM). This drug works in an anti-inflammatory capacity, improving clinical outcomes and improving quality of life in this population. The drug has also been shown to affect macrophage polarization by shifting these cells away from an inflammatory phenotype toward an alternatively activated anti-inflammatory phenotype. The full impact of this phenotypic change is not well understood in the context of the response to P. aeruginosa infection, or the overall immune response in cystic fibrosis. To understand how the AZM-polarized macrophage affects other types of cells, we utilized a co-culture in vitro system, with macrophages and fibroblasts incubating together. In this system, we determined that AZM causes upregulation of the pro-fibrotic mediator transforming growth factor-β as well as the extracellular matrix (ECM) protein fibronectin. The mediator of ECM turnover, matrix metalloproteinase (MMP)-9 was upregulated in this system as well. In an in vivo model of P. aeruginosa infection, MMP- 9 and fibronectin were increased in the bronchoalveolar lavage 7 days post-infection in mice that were treated with AZM. This was accompanied by a decrease in damage to the lung tissue, determine by histological examination. To determine if these changes would continue in human subjects with cystic fibrosis, a clinical study was done in this population. Subjects with AZM treatment had decreased TGF-β levels, but no differences in MMP-9 or fibronectin. Interestingly, correlations between certain fibrotic mediators and inflammatory cytokines, specifically interleukin -1β, were different in subjects with AZM treatment compared to subjects without AZM therapy. Together, these data indicate that AZM alters the fibrotic response from the macrophages, as well as the interaction of the inflammatory response and fibrosis development.

Obesity and drug abuse share common neural circuitries including the mesocoticolimbic and striatal dopamine reward system. In the current study, a rat model of diet-induced obesity (DIO) was used to determine striatal dopamine function, impulsivity and motivation as neurobehavioral outcomes and predictors of obesity. For the outcome study, rats were randomly assigned a high-fat (HF) or a low-fat (LF) diet for 8 wk. Following the 8-wk HF-diet exposure, rats were segregated into obesity-prone and obesity-resistant groups based on maximum and minimum body weight gain, respectively, and neurobehavioral outcomes were evaluated. For the predictor study, neurobehavioral antecedents were evaluated prior to an 8-wk high-fat diet exposure and were correlated with subsequent body weight gain. Striatal D2 receptor density was determined by in vitro kinetic analysis of [3H]raclopride binding. DAT function was determined using in vitro kinetic analysis of [3H]dopamine uptake, methamphetamine-evoked [3H]dopamine overflow and no net flux in vivo microdialysis. DAT cell-surface expression was determined using biotinylation and Western blotting. Impulsivity and food-motivated behavior were determined using a delay discounting task and progressive ratio schedule for food-reinforcers, respectively. Relative to obesity-resistant, obesity-prone rats exhibited 18% greater body weight, 42% lower striatal D2 receptor density, 30% lower total DAT expression, 40% lower in vitro and in vivo DAT function, 45% greater extracellular dopamine concentration, and 2-fold greater methamphetamine-evoked [3H]dopamine overflow. Obesity-prone rats exhibited higher motivation for food, but were less impulsive relative to obesity-resistant rats. Neurobehavioral antecedents of DIO included greater motivation for high-fat reinforcers in rats subsequently shown to be obesity-prone relative to obesity-resistant. Impulsivity, DAT function and extracellular dopamine concentration did not predict the DIO-phenotype. Thus, motivation for food is linked to both initiation and maintenance of obesity. Importantly, obesity results in decreased striatal DAT function, which may underlie the maintenance of compulsive food intake in obesity.

Simvastatin is a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor that is used for the treatment of hyperlipidemia. Simvastatin has recently been studied for its potential use in cancer therapy. In-vitro studies have shown that simvastatin displays anticancer activity, but at concentrations unlikely to be achieved in patients being receiving typical antihyperlipidemic treatment doses. Thus, several clinical trials were conducted to study the tolerability of high dose statins in cancer patients. The maximum tolerated dose of simvastatin was determined to be 15 mg/kg/day, 25-fold higher than a typical dose. However, it is not known if simvastatin plasma concentrations can reach those found to be effective in-vitro. In this context, we initiated a clinical study to determine the pharmacokinetics of high dose simvastatin in patients with chronic lymphocytic leukemia. For this purpose, an LC-MS/MS method was developed and validated for the quantitation of simvastatin and its acid form in plasma and peripheral blood mononuclear cells obtained from CLL patients. Results show that simvastatin concentrations were dose proportional relative to the antihyperlipidemic doses, but lower than those required for in-vitro cytotoxicity against cancer cells. These findings demonstrate that the in-vitro effective concentrations of simvastatin are not achievable clinically, which might explain the limited effectiveness of high dose simvastatin in this study and in previous clinical trials. In view of these data, the use of simvastatin as a sole therapy in cancer treatment was not encouraging and led us to examine the use in combination with other anticancer drugs. After screening several chemotherapeutic agents in combination with simvastatin, we showed that tipifarnib (a farnesyltransferase inhibitor) interacts synergistically in several leukemia cell lines. Mechanistically we showed that simvastatin augments the cytotoxicity of tipifarnib by disrupting the localization of RAS in the cell membrane and by subsequent deactivation of the ERK pathway. Consistent with this observation, drug treatment led to the induction of apoptosis through the caspase cascade activation and the cleaved PARP upregulation. Notably, this synergistic effect was observed at clinically achievable concentrations of simvastatin and tipifarnib. Thus, the effectiveness of this combination should be explored further in future clinical studies.

Gilvocarcin V (GV) belongs to the angucycline class of antibiotics that possesses remarkable anticancer and antibacterial activities with low toxicity. Gilvocarcin exhibits its light induced anticancer activity by mediating crosslinking between DNA and histone H3. When photo-activated by near-UV light, the C8 vinyl group forms a [2+2] cycloadduct with thymine residues of double stranded DNA. D-fucofuranose is considered essential for histone H3 interactions. However, the poor water solubility has rendered it difficult to develop gilvocarcin as a drug. We aim to design novel gilvocarcin analogues with improved pharmaceutical properties through chemo-enzymatic synthesis and mutasynthesis. Previous studies have characterized many biosynthetic genes encoding the gilvocarcin biosynthetic skeleton. Despite these previous findings the exact functions of many other key genes are yet to be fully understood. Prior gene inactivation and cross-feeding experiments have revealed that the first isolable tetracyclic aromatic product undergoes a series of steps involving C–C bond cleavage followed by two O-methylations, a penultimate C-glycosylation and final lactone formation in order to fully develop the gilvocarcin structure. To provide a deeper understanding of these complex biochemical transformations, three specific aims were devised: 1) synthesis of the proposed intermediate and in vitro enzyme reactions revealed GilMT and GilM’s roles in gilvocaric biosynthesis; 2) utilizing in vitro studies the enzyme responsible for the C–C bond cleavage and its substrate were determined; 3) a small series of structural analogues of the intermediate from the gilvocarcin pathway was generated via chemical synthesis and fed to the mixture of the enzymes, GilMT and GilM. These reaction mixtures were then analyzed to establish the diversity of substrates tolerated by the enzymes.

The present study was divided between two different drug delivery goals, each involving naltrexone (NTX) or its active metabolite, 6-β-naltrexol (NTXOL). First, amino acid esters of NTX and NTXOL were prepared in order to test their candidacy for microneedle-enhanced transdermal delivery. Second, a 3-O-(-)-cytisine-naltrexone (CYT-NTX) codrug was prepared for screening as a potential oral delivery form of NTX and (-)-cytisine (CYT). The amino acid prodrugs were intended for the treatment of alcohol abuse, while the codrug was designed as a single agent for the treatment of alcoholism and tobacco-dependency co-morbidities. One hypothesis of this work was that prodrugs of NTX or NTXOL can be designed that possess superior skin transport properties through microneedle-treated skin compared to parent NTX or NTXOL. Nine amino acid ester prodrugs were prepared, and only three 6-O amino acid ester prodrugs of NTXOL were stable enough at skin pH (pH 5.0) to move forward to studies in 50% human plasma. 6-O-β-Ala-NTXOL, the lead compound, exhibited the most rapid bioconversion to NTXOL in human plasma (t1/2 = 2.2 ± 0.1 h); however, this in vitro stability value indicates that the prodrug may require hepatic enzyme-mediated hydrolysis for sufficiently rapid bioconversion to NTXOL in vivo. A second hypothesis of this work was that a CYT-NTX codrug could be designed with appropriate stability characteristics for oral delivery. CYT-NTX was found to be stable over the time course of 24 h in buffer systems of pH 1.5, 5.0, 7.4 and 9.0, and in 80% rat plasma, 80% human plasma, simulated gastric fluid and simulated intestinal fluid. Six (3 rats/group) Sprague-Dawley male rats were dosed i.v. with 1 mg/kg CYT-NTX codrug, or 10 mg/kg, p.o. Oral administration of a 10 mg/kg dose of CYT-NTX codrug resulted in rapid absorption and distribution (5 min) of CYT-NTX codrug, and NTX was released from codrug with a peak plasma concentration of 6.8 ± 0.9 nmol/L reached within 65 minutes. Plasma CYT was not detected; however, NTX delivery was achieved with a fraction absorbed value of 13%. Thus, CYT-NTX may hold promise as a potential oral codrug for further optimization and development.

The majority of pharmacologically active chemotherapeutics are poorly water soluble. Solubilization enhancement by the utilization of organic solvents often leads to adverse side effects. Nanoparticle-based cancer therapy, which is passively targeted to the tumor tissue via the enhanced permeation and retention effect, has been vastly developed in recent years. Nanocrystals, which exist as crystalline and carry nearly 100% drug loading, has been explored for delivering antineoplastic agents. Additionally, the hybrid nanocrystal concept offers a novel and simple way to integrate imaging agents into the drug crystals, enabling the achievement of theranostics. The overall objective of this dissertation is to formulate both pure and hybrid nanocrystals, evaluate their performance in vitro and in vivo, and investigate the extent of tissue distribution and tumor accumulation in a murine model. Pure and hybrid nanocrystals of several model drugs, including paclitaxel (PTX), camptothecin, and ZSTK474, were precipitated by the antisolvent method in the absence of stabilizer, and their size was further minimized by homogenization. The nanocrystals of PTX, which is the focus of the study, had particle size of approximately 200 nm and close-to-neutral surface charge. Depending on the cell type, PTX nanocrystals exerted different level of cytotoxicity. In human colon and breast cancer xenograft models, nanocrystals yielded similar efficacy as the conventional formulation, Taxol, at a dose of 20 mg/kg, yet induced a reduced toxicity. Biodistribution study revealed that 3H-PTX nanocrystals were sequestered rapidly by the macrophages upon intravenous injection. Yet, apparent toxicity was not observed even after four weekly injections. The sequestered nanocrystals were postulated to be released slowly into the blood circulation and reached the tumor. Tritium-labeled-taxol, in contrast, was distributed extensively to all the major organs, inducing systemic toxicity as observed in significant body weight loss. The biodistribution results obtained from radioactive analysis and whole-body optical imaging was compared. To some degree, the correlation was present, but divergence in the quantitative result, due to nanocrystal integrity and limitations associated with the optical modality, existed. Despite their promising properties, nanocrystal suspensions must be securely stabilized by stealth polymers in order to minimize opsonization, extend blood-circulation time, and efficiently target the tumor.

AR-67 is a lipophilic third generation camptothecin analogue, currently under early stage clinical trials. It acts by targeting Topoisomerase 1 (Top1), a nuclear enzyme essential for DNA replication and transcription and is present in two forms, the pharmacologically active lipophilic lactone and the charged carboxylate. In oncology patients participating in a phase I clinical trial, AR-67 lactone was the predominant species in plasma. Similarly to other camptothecins, the identified dose-limiting toxicities for AR-67 were neutropenia, thrombocytopenia and fatigue. In addition, in vitro metabolism studies indicated AR-67 lactone as a substrate for CYP3A4/5 as well as the UGT1A7 and UGT1A8 enzymes localizing in the liver and the gut. Numerous studies have demonstrated the over-expression of transporters in certain tumor types. Here, the effect of interactions between AR-67 and efflux or uptake transporters on the antitumor efficacy of AR-67 in vitro was studied. We showed that BCRP and MDR1 overexpression confers resistance to AR-67. Moreover, we demonstrated the therapeutic superiority of protracted dosing over more intense dosing regimens of AR-67 using xenografts models. Our studies indicated the schedule-dependent expression of Top1 and the preferential partitioning of AR-67 in the tumor tissue. We reason that these are factors that need to be taken into consideration when designing dosing schedules aiming to maximize efficacy. As most cytotoxic drugs, AR-67 has a narrow therapeutic window. Thus, it is essential to identify the variables influencing exposure to this camptothecin analogue. A thorough compartmental pharmacokinetic analysis was performed on the patient data obtained in a phase 1 clinical trial on AR-67. Moreover, sources of intersubject variability associated with obtaining pharmacokinetic parameter estimates were identified and a population covariate pharmacokinetic model was developed. In conclusion, the drug development of AR-67 is a work in process. Findings presented above provide an insight on the factors contributing to its efficacy and toxicity when given to cancer patients.