Fluoroquinolones are broad-spectrum antibacterial agents based on the structure of nalidixic acid. For nearly five decades it has been known that fluoroquinolones inhibit bacterial growth by blocking the enzymatic action of type II topoisomerases such as DNA gyrase and topoisomerase IV. Only recently has it been discovered that some fluoroquinolones are capable of a mechanism that results in fragmented DNA and leads to rapid bacterial cell death. This mechanism is not well understood. Presented here are studies towards understanding the structure activity relationship (SAR) of fluoroquinolones, specifically to determine what leads to the novel mechanism termed "rapid lethality." This work is based on the hypothesis that structurally unique fluoroquinolones interact with the DNA-topoisomerase complex in a unique manner that ultimately leads to rapid cell death. The first approach to understand SAR for killing was to evaluate the effect of a ring fusion between N-1 and C-8 of the fluoroquinolone core. Known lethal fluoroquinolones are substituted by N-1 cyclopropyl and C-8 methoxy, but some clinically important fluoroquinolones contain a 2-methylmopholino moiety between these two positions. Novel fluoroquinolones were synthesized and clinically available agents were obtained to create a panel of drug molecules with one of six C-7 substituents and either the morpholine ring system or N-1 cyclopropyl and C-8 methoxy. Bacteriostatic and bactericidal activities of these compounds were determined. Bactericidal studies were conducted both in the presence and absence of chloramphenicol, a protein synthesis inhibitor used to simulate non-growing bacteria. Lethality in the presence of chloramphenicol is also important when considering co-administration of fluoroquinolones with other antibiotic classes. In a second study, fluoroquinolones were synthesized with a C-2 thioalkyl substitution. Substitutions at the C-2 position are severely lacking in clinical fluoroquinolones, with only prulifloxacin, a newly developed antibiotic, being substituted by an N-1 to C-2 thiazetidine ring structure. Analogs of ciprofloxacin and moxifloxacin were synthesized such that the N-1, C-2, and C-8 positions were substituted with cyclopropyl, thioethyl/thioisopropyl, and methoxy groups, respectively. The compounds were then evaluated for antibiotic activity against three different bacterial strains to evaluate the contribution of the C-2 thioalkyl substituent to antibacterial activity. In a third study, quinazoline-2,4-diones, a new antibiotic class structurally and mechanistically similar to fluoroquinolones, were modified at the C-4 position in an effort to understand the binding interaction between these compounds and the target enzyme. Importantly, the quinazoline-2,4-diones typically retain activity against bacterial cells known to be resistant to fluoroquinolones and are less likely to select for resistant mutants. In this study, the C-4 carbonyl was replaced with either a thiocarbonyl or a hydroxylimine and the new compounds, bearing C-7 substituents common to potent antibiotic fluoroquinolones and quinazolines, were evaluated for activity against bacterial cells. Despite the findings of recently published X-ray crystallography, it was determined that one of the greatest determinants in antibiotic activity of fluoroquinolones is the C-7 substituent. Additionally, there is increasing evidence that the C-2 carbonyl of quinazoline-2,4-diones affords the increase in activity against resistant mutants by creating a unique binding interaction. Collectively, the conclusions reached here add to our understanding of the structure activity relationship of the fluoroquinolone antibiotic class for rapidly killing bacterial cells and overcoming resistant mutants.

Alkaline degradation of Carbaryl in the presence of CTAB micelles has been reported as the most efficient method; however, the factors accounting for it are not yet clear. The main objective of this work was to study some of the factors affecting the alkaline degradation of Carbaryl in the presence of cetyl trimethylammonium bromide (CTAB). Three specific aims were researched in order to address the main objective. Solubility studies, UV-vis, fluorescence, and 1D-HNMR and 2D-HNMR spectroscopies were used to research the solubilization of carbaryl in CTAB micelles. Solubility studies showed that carbaryl partitions into CTAB micelles with a binding constant of 553 ± 8 M-1, and each mole of micellized surfactant incorporates about 0.336 moles of carbaryl. Spectroscopy studies showed that carbaryl does not interact electrostatically with micelles but does through van der Waals interactions. 1D-HNMR and 2D-HNMR indicated solubilization in the Stern layer, oriented with its hydrophilic moiety towards the Goüy-Chapman layer and the hydrophobic moiety towards the core of the micelle. Kinetic studies as a function of the surfactant concentration along with micellar kinetic models were used to calculate micellar rate constants (k’M) for each of four different cationic surfactants: cetyl trimethylammonium hydroxide (CTAOH), cetyl trimethylammonium bromide (CTAB), cetyl trimethylammonium chloride (CTACl), and cetyl pyridinium chloride (CPCl), and compared to the corresponding rate constants (k’W) in water; the results in all cases showed k’M / k’W > 1. This fact led to the conclusion that additional factors beyond solubilization of substrates are playing a role. Solubility studies revealed the following binding constant order and solubilization capacity order: CPCl > CTAOH ≈ CTAB > CTACl, CPCl > CTAOH ≈ CTAC > CTAB, indicating that for CPCl, Coulombic interactions, such as charge-transfer complexes, may be favoring the concentration effects, while for other surfactants, such as CTAOH, the [–OH] as the micelle counterion increases Carbaryl’s concentration in the Stern layer compared to its bulk concentration. In contrast, large, weakly-hydrated polarizable ions such as Br– displace hydrophilic ions, providing less enhancement. Kinetic experiments as a function of the surfactant head’s charge led to the conclusion that cationic and zwitterionic surfactants have a catalytic effect of the alkaline hydrolysis of carbaryl, while nonionic and anionic surfactants have inhibitory effects: kobs (cationic) > kobs (zwitterionic) > kobs(nonionic) > kobs (anionic). A similar order for solubility parameters (Ks and SC) was observed from equilibrium solubility studies. Experiments as a function of the polarity of the medium in the presence of both polar and nonpolar solvents showed that the hydrolysis rate is inversely proportional to the medium polarity. Ionic strength experiments showed that the hydrolysis rate is inversely proportional to the ion concentration.

Fluoroquinolones, a class of type-II topoisomerase inhibitors, have successfully been used as antibiotics for the last several decades, beginning with the use of nalidixic acid in urinary tract infections. This led to the broad-spectrum activity of ciprofloxacin in the 1980s. Unfortunately, use of fluoroquinolones has led to the emergence of resistant bacteria. Recently, this has generated new bacteria such as multidrug-resistant and extensive-drug-resistant strains of M. tuberculosis that are also fluoroquinolone-resistant. Infections caused by these bacterial strains are widespread, with high mortality rate in immune-compromised populations such as the elderly, infants, and in AIDS or HIV-positive patients. Fluoroquinolone resistance is acquired through amino acid substitutions of key fluoroquinolone-binding residues of the type-II bacterial topoisomerases DNA Gyrase and Topoisomerase IV, the enzyme targets of fluoroquinolones. Amino acid substitutions that result in fluoroquinolone resistance are located on Helix-4 of these enzymes, which is the site of a magnesium (Mg)-water bridge that is a crucial binding interaction for fluoroquinolones. When certain substitutions to Helix-4 occur, the Mg-water bridge is compromised and no longer available to anchor fluoroquinolones into a ternary complex composed of topoisomerase, fluoroquinolone, and DNA. This results in drug resistance. Herein are described attempts to generate fluoroquinolones that are capable of overcoming this mechanism of resistance. In the first study, attempts were made to generate a series of novel tricyclic fluoroquinolones and diones designed to exploit intercalative or pi-stacking binding interactions with the bacterial DNA in the ternary complex in order to lessen the importance of the Mg-water bridge interaction. Despite numerous attempts, no complete synthetic pathway to these core structures was ever discovered. The second study investigated the utility of a C7-aminomethylpyrrolidine group on the fluoroquinolone structure. This was done in order to explore the mechanistic reasons why previously generated fluoroquinolones possessing this C7-aminomethylpyrrolidine group maintained activity against common Helix-4 mutants. A panel of fluoroquinolones with C7-aminomethylpyrrolidine groups and diverse core structures was synthesized and docking studies with the original C7-aminomethylpyrrolidine fluoroquinolone and other fluoroquinolones were performed. Target compounds were synthesized and evaluated for inhibition/poisoning purified enzyme and for the ability to inhibit growth with wild-type and fluoroquinolone-resistant cells. In a third study, fluoroquinolones possessing structural variations of the C7-aminomethylpyrrolidine were designed and synthesized to explore structural requirements of the aminomethylpyrrolidine group binding and overcoming fluoroquinolone-resistance caused by alterations of Helix-4. This led to further exploration of the binding space around the C7-position of the fluoroquinolones. In both the second and third studies, the new fluoroquinolones were evaluated for the ability to specifically target bacterial topoisomerases over human topoisomerase. The results of these studies have contributed new knowledge to the binding requirements of fluoroquinolones that maintain potency against fluoroquinolone-resistant type-II topoisomerases, and represent a step towards methodology to overcome bacteria resistant to fluoroquinolones.

Pyronaridine/Artesunate (PA) 3:1 fixed dose combination is a novel artemisinin-based combination therapy (ACT) in development for the treatment of acute uncomplicated Plasmodium falciparum or Plasmodium vivax malaria. An understanding of both pharmacokinetics and pharmacodynamics of pyronaridine is of importance in order to achieve optimal therapeutic outcome. In this thesis, population pharmacokinetic models for pyronaridine in healthy subjects, and adult and pediatric malaria patients were developed. Pyronaridine pharmacokinetics in both adult and pediatric populations were best described by a two compartment model with first order absorption and elimination from the central compartment. A presence of malaria infection and body weight were the significant covariates that explained pyronaridine pharmacokinetic variability in the adult population. For the pediatric population, age was the only significant covariate that explained pyronaridine pharmacokinetic variability. Monte Carlo simulations were also performed to address differences in pyronaridine exposures among these populations and to explore the exposures of pyronaridine among recommended dosage regimens for pediatric and adult malaria patients. Healthy adults had a higher exposure to pyronaridine as compared to adult malaria patients. For the pediatric population, younger children had a higher exposure to pyronaridine as compared to older children. The overall range of pyronaridine exposures among dosing groups for adult and pediatric malaria patients were relatively similar. The cut-off values of pyronaridine pharmacokinetic parameters associated with successful treatment outcome were also determined by means of receiver operating characteristic (ROC) curve. These cut-off values can be used to optimize the outcome of malaria treatment. Additionally, Cox proportional hazard model was conducted to determine the relationship between several covariates and time to the occurrence of re-infection or recrudescence. The models showed that as the levels of predicted pyronaridine concentrations on day 7 increased, the risks of acquiring re-infection or recrudescence decreased. Finally, pharmacokinetic drug-drug interaction of pyronaridine and ritonavir was assessed based on the overlap pathway for metabolism of both drugs and the high rates of HIV and malaria co-infection. There was an effect of ritonavir on pyronaridine pharmacokinetics. However, the results were not considered clinically relevant. An increase in ritonavir exposure was observed in the presence of fixed dose PA.

OSW-1 is a natural saponin and its anticancer activities are 10- to 100-fold more potent than many well-known anticancer agents in clinical use. Its cytotoxicity profile suggests that it may have a unique mode of action that is different from other well-known anticancer agents. However, its mechanism still remains as a mystery after years of study, and no paper has ever been published in this area. Extensive in vitro and in vivo testing has been conducted and toxicology experiments have also been carried out by our collaborator Prof. Huang's laboratory at MD Anderson Cancer Center. In order to identify the pharmacophore and mechanism of OSW-1 and increase its in vivo activity and selectivity, amino analogues are synthesized for the SAR study employing the chemistry developed in our lab. Superstolide A (1) is a highly potent anti-tumor reagent that was isolated from deep water marine sponge in 1996. The potent anticancer activity, molecular complexity (11 chiral centers) and scarcity in natural resources make this molecule an attractive synthetic target. Currently I am working on the model study for the construction of the 16-membered macrolactone present in Superstolide A. Specifically I am focusing on the investigation of three crucial carbon-carbon bond-forming reactions in our synthetic strategy including Julia olefination, Suzuki coupling and Horner-Emmons olefination.

While there are a variety of therapeutics that interact with the opioid receptor system, they are not without side effects; including constipation, dysphoria and respiratory depression. A better understanding of the opioid receptor system may yield therapeutic agents with a limited side effect profile. The neoclerodane diterpene, salvinorin A, appears to interact at opioid receptors through a unique mode of action. A better understanding of its interactions with opioid receptors will yield valuable information about the opioid system. In order to probe further how salvinorin A interacts at opioid receptors, a series of novel analogues modified at the C-2 and furan ring were synthesized and evaluated for their ability to interact at opioid receptors. Synthetic methods were identified to modulate the furan ring, including the synthesis of Diels-Alder cycloadducts and phenyl rings derived from a reductive elimination. The cycloadducts are one of the first reported examples of Diels-Alder chemistry being applied to modify a neoclerodane while the phenyl ring analogues are the first to have aromatic rings directly off the salvinorin A core. C-2 sulfonate analogues were found to interact differently then their ester counterparts at opioid receptors while several of the cycloadduct analogues maintained affinity and efficacy demonstrating the furan is not required for opioid receptor activity. These findings demonstrate that salvinorin A is amenable for chemical modification, illustrating its potential as a novel scaffold for the development of opioid ligands.

Purpose Two new scales, CORECTS and PUQE-24 are introduced and validated, and the safety and effectiveness of Proctofoam-HC® in pregnancy is demonstrated. Method 315 of Motherisk NVP patients provided information on five clinical parameters as well as PUQE scores. 28 patients visiting a proctologist were graded for the severity of anal conditions by a proctologist before administering CORECTS. Pre and postnatal interviews were conducted with 204 pregnant women prescribed Proctofoam-HC®. Results Strong correlations were found between the following: PUQE-24 scores and parameters of well-being, hospitalization, and multivitamin intake; bleeding and pain components of CORECTS and the proctologist’s grade.There was no significant difference between mean birth weight of Proctofoam-HC® treated and comparison groups. There was a significant reduction in all symptoms of hemorrhoids. Conclusion PUQE-24 and CORECTS are the first validated scales used to assess the severity of NVP and hemorrhoids. Proctofoam-HC® is safe and effective for use in pregnancy.

Purpose Two new scales, CORECTS and PUQE-24 are introduced and validated, and the safety and effectiveness of Proctofoam-HC® in pregnancy is demonstrated. Method 315 of Motherisk NVP patients provided information on five clinical parameters as well as PUQE scores. 28 patients visiting a proctologist were graded for the severity of anal conditions by a proctologist before administering CORECTS. Pre and postnatal interviews were conducted with 204 pregnant women prescribed Proctofoam-HC®. Results Strong correlations were found between the following: PUQE-24 scores and parameters of well-being, hospitalization, and multivitamin intake; bleeding and pain components of CORECTS and the proctologist’s grade.There was no significant difference between mean birth weight of Proctofoam-HC® treated and comparison groups. There was a significant reduction in all symptoms of hemorrhoids. Conclusion PUQE-24 and CORECTS are the first validated scales used to assess the severity of NVP and hemorrhoids. Proctofoam-HC® is safe and effective for use in pregnancy.

Purposes: The purpose of this study was threefold. First, to examine how both the effectiveness of valsartan centric regimens and the patient-related factors affect the control rates of the Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP) and combined SBP/DBP; specifically for Belgian patients with a history of failed or intolerant anti-hypertensive treatment. Secondly, to assess the effectiveness of valsartan treatment groups and the related factors concerning a patients' total cardiovascular risk (TCVR) residuals. Lastly, to attempt to estimate the cost avoidance factor associated with taking varying levels of valsartan treatment doses. Methodology: This research took the form of a secondary-data analysis study, focusing on the analysis of data collected primarily from seven prospective studies conducted between 2004 and 2009, covering different regimens of valsartan. The variants of valsartan doses given to patients included: valsartan monotherapy (80mg or 160 mg); a combination of valsartan with hydrochlorothiazide (HCTZ) (80 mg and 12.5mg, 160mg and 12.5 mg, or 160mg and 25mg); and a combination of valsartan with amlodipine (80mg and 5mg, 160mg and 5mg, or 160mg and 10mg). We applied Bailey's approach, using Kaplan-Meier curves to estimate the distribution of treatment intensity at which the target rates of SBP, DBP and SBP/DBP were achieved. The treatment intensity was calculated by dividing the daily dose prescribed to a patient by the maximum daily recommended dose of that particular drug variant. The outcomes provided by Bailey's approach included the control rates of SBP, DBP and combined SBP/DBP, in addition to the reduction in TCVR residuals. Another aspect of our methodology was the use of a simulation method to estimate the cost avoidance by using valsartan treatment groups. We used OCED data to compare health indicators between the US and Belgium in order to estimate the ratio enabling us to calculate the cost of hypertension per patient per year. This cost was then used in the simulation method to calculate the cost avoidance of using varying levels of the treatment intensity of valsartan regimens. Results: A total of 17,683 patients were included in this study, contributed to by 3,434 physician-investigators. The mean age of the population was 63.63 + 11.83 years, with a mean BMI of 28.45 + 3.13 kg/m^2 and 47.7% of the population was male and the vast majority of the total population was Caucasian (98%). As a baseline the total population who had controlled SBP, DBP and combined SBP/DBP were 1358, 5301 and 1091 respectively. The total population who were categorized as low added risk TCVR, moderate added risk TCVR, high added risk TCVR, and very high added risk TCVR were 192; 3,721; 3,888 and 9,362 respectively. Overall, there was a statistically significant increase in the proportion of patients with controlled SBP, DBP and combined SBP/DBP after 90 days of starting on valsartan-centric regimens (p<0.001). Both older age and the presence of diabetes were associated with a lower control rate of SBP, DBP and combined SBP/DBP (P<0.05). High adherence to valsartan-centric regimens was associated with an increase in the control rates of blood pressure. Substantial reductions in total cardiovascular risk, particularly in the very high added-risk category was observed 5,852 times (33.1%) (P<0.001) and an increase in the low added risk TCVR 3,331 times (18.9%) (p<0.001). The associated cost avoidance with varying levels of treatment intensity were dose related. The cost avoidance associated with the treatment intensity levels of 0.25, 0.5, 0.75, 1.0 and 1.5 were $261,164; $2,403,188; $6,384,142; $8,702,272 and $10,230,321, respectively. Conclusion: The different levels of the treatment intensity of valsartan-centric regimens were effective in increasing the control rates of SBP, DBP and combined SBP/DBP in the real practice for patients whose prior treatment failed. Not only did valsartan regimens improve the BP control rate, they also reduced the TCVR residuals. Additionally, substantial cost avoidance was found to be associated with the use of higher levels of treatment intensity. These results may support the idea that intensive anti-hypertensive treatment may be associated with higher clinical and economic benefits for both patients and payers. However, more research might be needed to validate our results and to address the questions of adverse effects that may be associated with intensive anti-hypertensive therapy and the economic consequences of treating any such effects.

Background: In the current policy environment hospital readmissions are receiving considerable attention due to a provision in the Affordable Care Act (2010), that penalize hospitals through reduced payments for excess readmissions (the hospital readmissions reduction program (HRRP)). This program primarily holds hospitals accountable, although a multitude of factors not directly in control of hospitals can be contributory to readmissions. Of these, whether or not patients are discharged to an appropriate post-discharge care setting can be one contributory factor, and, this study evaluated the association between post-discharge care setting and hospital revisits. Methods: A retrospective analysis of the 2008 Medicare Current Beneficiary Survey (MCBS) was conducted. Three post-discharge care settings were evaluated: 1) routine discharge to home; 2) home with home healthcare; and 3) skilled nursing facility. Two outcomes were assessed: 1) 30-day all-cause hospital readmissions; and 2) 30-day all-cause hospital revisits (combination of inpatient admissions and emergency department visits). Analyses were carried out among patients with hospitalizations for any reason, as well as among a subgroup that were hospitalized for one of seven priority conditions identified in the HRRP. Weighted logistic regression analyses that incorporated information on the complex survey design were conducted. Results: Of the MCBS sample representing 46,048,125 Medicare beneficiaries (unweighted N=11,723), 4.9 percent (N= 2,293,629; unweighted N=670) contributed at least one index hospitalization to the analysis. Among hospitalization for any reason, 30-day all-cause hospital readmissions and revisits was 12.3 percent and 17.8 percent, respectively. The subgroup consisted of 31.8 percent of hospitalizations for any reason (N=730,174; unweighted N=216). Readmissions and revisits in the subgroup were 17.8 percent, and 24.5 percent, respectively. Post-discharge care setting was not significantly associated with either readmissions (P=0.966) or revisits (P=0.728) for hospitalizations for any reason. Findings for the subgroup were similar with no significant association between post-discharge care setting with either readmissions (P=0.850) or revisits (P=0.483). Conclusion: Absence of a difference in readmissions and revisits by post-discharge care setting suggests that the choice of discharge status might be appropriate following an inpatient admission. However, further research with larger sample sizes for conditions in the subgroup both together and separately is recommended.