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1.  External Validation of the Bilirubin–Atazanavir Nomogram for Assessment of Atazanavir Plasma Exposure in HIV-1-Infected Patients 
The AAPS journal  2012;15(2):308-315.
Atazanavir increases plasma bilirubin levels in a concentration-dependent manner. Due to less costly and readily available assays, bilirubin has been proposed as a marker of atazanavir exposure. In this work, a previously developed nomogram for detection of suboptimal atazanavir exposure is validated against external patient populations. The bilirubin nomogram was validated against 311 matching bilirubin and atazanavir samples from 166 HIV-1-infected Norwegian, French, and Italian patients on a ritonavir-boosted regimen. In addition, the nomogram was evaluated in 56 Italian patients on an unboosted regimen. The predictive properties of the nomogram were validated against observed atazanavir plasma concentrations. The use of the nomogram to detect non-adherence was also investigated by simulation. The bilirubin nomogram predicted suboptimal exposure in the patient populations on a ritonavir-boosted regimen with a negative predictive value of 97% (95% CI 95–100). The bilirubin nomogram and monitoring of atazanavir concentrations had similar predictive properties for detecting non-adherence based on simulations. Although both methods performed adequately during a period of non-adherence, they had lower predictive power to detect past non-adherence episodes. Using the bilirubin nomogram for detection of suboptimal atazanavir exposure in patients on a ritonavir-boosted regimen is a rapid and cost-effective alternative to routine measurements of the actual atazanavir exposure in plasma. Its application may be useful in clinical settings if atazanavir concentrations are not available.
PMCID: PMC3618856  PMID: 23224752
atazanavir; bilirubin; nomogram
2.  Assessment of a Spectrophotometric Assay for Monoacylglycerol Lipase Activity 
The AAPS journal  2010;12(2):197-201.
PMCID: PMC2844520  PMID: 20186507
monoacylglycerol lipase; spectrophotometric assay
3.  Physical Approaches for Nucleic Acid Delivery to Liver 
The AAPS journal  2008;10(4):589-595.
Liver is a key organ for numerous metabolic pathways and involves many inherited diseases that, although being different in their pathology, are often caused by lack or overproduction of a critical gene product in the diseased cells. In principle, a straightforward method to fix such problem is to introduce into these cells with a gene-coding sequence to provide the missing gene product, or with the nucleic acid sequence to inhibit production of the excessive gene product. Practically, however, success of nucleic acid-based pharmaceutics is dependent on availability of a method capable of delivering nucleic acid sequence in the form of DNA or RNA to liver cells. In this review, we will summarize the progress toward development of physical methods for nucleic acid delivery to liver. Emphasis is placed on the mechanism of action, pros and cons of each method developed so far. We hope the information provided will encourage new endeavor to improve the current methodologies or develop new strategies that will lead to safe and effective delivery of nucleic acids to liver.
PMCID: PMC2628207  PMID: 19083101
Gene delivery; non-viral vectors; physical method; liver; transfection
4.  Pharmacogenetic and Metabolic Differences Between Dog Breeds: Their Impact on Canine Medicine and the Use of the Dog as a Preclinical Animal Model 
The AAPS journal  2008;10(1):110-119.
There is limited information describing species related pharmacogenetic differences in animals. Despite the lack of genetic information in veterinary medicine, breed specific responses to endogenous and exogenous substances have been reported across many species. This finding underscores the importance of obtaining insight into the genotypic and phenotypic variation present across breeds. This article provides a summary of the literature pertaining to canine breed differences in physiology, drug response, drug pharmacokinetics, and metabolic idiosyncrasies. The existing knowledge of pedigrees and the known phenotypes and genotypes of dogs provides important information for determining mode of inheritance, penetration, and other major characteristics of heritable traits. Understanding these breed differences will improve canine population predictions (for canine drug products) and may be of value when extrapolating toxicology data from dogs to humans.
PMCID: PMC2747081  PMID: 18446511
bioavailability; breed-related differences; canine pharmacodynamics; canine pharmacogenetics; canine pharmacokinetics; drug response; population diversity
5.  Glial–Neuronal Interactions—Implications for Plasticity and Drug Addiction 
The AAPS journal  2009;11(1):123-132.
Among neuroscientists, astrocytes have for long played Cinderella to their neuron stepsisters. While the importance of glia in regulating brain activity was predicted by Ramon y Cajal more than a century ago (Garcia-Marin et al., Trends. Neurosci. 30:479–787, 2007), these cells, until recently, have been thought to play mainly a passive part in synaptic signaling. Results obtained over the last decade have begun to suggest otherwise. Experiments carried out in a number of labs have shown that glial cells, especially astrocytes, directly participate in synaptic signaling and potentially regulate synaptic plasticity and network excitability. The presence of signaling pathways on astrocytes that are analogous to those at presynaptic terminals suggests a role for these cells in network plasticity. Findings that the same signaling pathways can be activated by receptors for drugs of abuse present on astrocytes suggest a role for these cells in the addictive process. In this review, we summarize current understanding of astrocytic role in synaptic signaling and suggest that a complete understanding of the process of addiction requires a better understanding of the functional role of these cells.
PMCID: PMC2664886  PMID: 19238557
astrocyte; calcium; gliotransmission; nicotinic; synapse; tripartite synapse
6.  A Bayesian Approach for Quantifying Trace Amounts of Antibody Aggregates by Sedimentation Velocity Analytical Ultracentrifugation 
The AAPS journal  2008;10(3):481-493.
Sedimentation velocity analytical ultracentrifugation (SV-AUC) has become an important tool for the characterization of the purity of protein therapeutics. The work presented here addresses a need for methods orthogonal to size-exclusion chromatography for ensuring the reliable quantitation of immunogenic oligomers, for example, in antibody preparations. Currently the most commonly used approach for SV-AUC analysis is the diffusion-deconvoluted sedimentation coefficient distribution c(s) method, previously developed by us as a general purpose technique and implemented in the software SEDFIT. In both practical and theoretical studies, different groups have reported a sensitivity of c(s) for trace oligomeric fractions well below the 1% level. In the present work we present a variant of c(s) designed for the purpose of trace detection, with customized Bayesian regularization. The original c(s) method relies on maximum entropy regularization providing the most parsimonious distribution consistent with the data. In the present paper, we use computer simulations of an antibody system as example to demonstrate that the standard maximum entropy regularization, due to its design, leads to a theoretical lower limit for the detection of oligomeric traces and a consistent underestimate of the trace populations by ∼0.1% (dependent on the level of regularization). This can be overcome with a recently developed Bayesian extension of c(s) (Biomacromolecules (2007), 8, 2011-2024), utilizing the known regions of sedimentation coefficients for the monomer and oligomers of interest as prior expectation for the peak positions in the distribution. We show that this leads to more clearly identifiable and consistent peaks and lower theoretical limits of quantization by approximately an order of magnitude for some experimental conditions. Implications for the experimental design of SV-AUC and practical detection limits are discussed.
PMCID: PMC2696691  PMID: 18814037
sedimentation velocity; analytical ultracentrifugation; trace aggregates; hydrodynamic separation; size-distribution; Bayesian analysis
7.  Modulation of Microglial Pro-inflammatory and Neurotoxic Activity for the Treatment of Parkinson’s Disease 
The AAPS journal  2006;8(3):E606-E621.
Parkinson’s disease (PD) is a debilitating movement disorder resulted from a progressive degeneration of the nigrostriatal dopaminergic pathway and depletion of neurotransmitter dopamine in the striatum. Molecular cloning studies have identified nearly a dozen genes or loci that are associated with small clusters of mostly early onset and genetic forms of PD. The etiology of the vast majority of PD cases remains unknown and the precise molecular and biochemical processes governing the selective and progressive degeneration of the nigrostriatal dopaminergic pathway is poorly understood. Current drug therapies for PD are symptomatic and appear to bear little impact on the progressive neurodegenerative process. Studies of post mortem PD brains and various cellular and animal models of PD in the last two decades strongly suggest that the generation of pro-inflammatory and neurotoxic factors by the resident brain immune cells, microglia, plays a prominent role in mediating the progressive neurodegenerative process. This review will discuss literature supporting the possibility of modulating the activity of microglia as a neuroprotective strategy for the treatment of PD.
PMCID: PMC2668934  PMID: 17025278
Dopamine neuron; Parkinson’s disease; Movement disorder; Microglia; Neuroprotection; Free radical
8.  Pharmacogenomic Responses of Rat Liver to Methylprednisolone: An Approach to Mining a Rich Microarray Time Series 
The AAPS journal  2005;7(1):E156-E194.
A data set was generated to examine global changes in gene expression in rat liver over time in response to a single bolus dose of methylprednisolone. Four control animals and 43 drug-treated animals were humanely killed at 16 different time points following drug administration. Total RNA preparations from the livers of these animals were hybridized to 47 individual Affymetrix RU34A gene chips, generating data for 8799 different probe sets for each chip. Data mining techniques that are applicable to gene array time series data sets in order to identify drug-regulated changes in gene expression were applied to this data set. A series of 4 sequentially applied filters were developed that were designed to eliminate probe sets that were not expressed in the tissue, were not regulated by the drug treatment, or did not meet defined quality control standards. These filters eliminated 7287 probe sets of the 8799 total (82%) from further consideration. Application of judiciously chosen filters is an effective tool for data mining of time series data sets. The remaining data can then be further analyzed by clustering and mathematical modeling techniques.
PMCID: PMC2607485  PMID: 16146338
Data mining; gene arrays; glucocorticoids; mathematical modeling; pharmacogenomics
10.  Overview of the Proton-coupled MCT (SLC16A) Family of Transporters 
The AAPS journal  2008;10(2):311-321.
The transport of monocarboxylates, such as lactate and pyruvate, is mediated by the SLC16A family of proton-linked membrane transport proteins known as monocarboxylate transporters (MCTs). Fourteen MCT-related genes have been identified in mammals and of these seven MCTs have been functionally characterized. Despite their sequence homology, only MCT1-4 have been demonstrated to be proton-dependent transporters of monocarboxylic acids. MCT6, MCT8 and MCT10 have been demonstrated to transport diuretics, thyroid hormones and aromatic amino acids, respectively. MCT1-4 vary in their regulation, tissue distribution and substrate/inhibitor specificity with MCT1 being the most extensively characterized isoform. Emerging evidence suggests that in addition to endogenous substrates, MCTs are involved in the transport of pharmaceutical agents, including γ-hydroxybuytrate (GHB), 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins), salicylic acid, and bumetanide. MCTs are expressed in a wide range of tissues including the liver, intestine, kidney and brain, and as such they have the potential to impact a number of processes contributing to the disposition of xenobiotic substrates. GHB has been extensively studied as a pharmaceutical substrate of MCTs; the renal clearance of GHB is dose-dependent with saturation of MCT-mediated reabsorption at high doses. Concomitant administration of GHB and l-lactate to rats results in an approximately two-fold increase in GHB renal clearance suggesting that inhibition of MCT1-mediated reabsorption of GHB may be an effective strategy for increasing renal and total GHB elimination in overdose situations. Further studies are required to more clearly define the role of MCTs on drug disposition and the potential for MCT-mediated detoxification strategies in GHB overdose.
PMCID: PMC2574616  PMID: 18523892
butyrate; gamma-hydroxybutyrate; lactate; monocarboxylate transporters; SLC16A
11.  O-Phospho-L-Serine, Multi-functional Excipient for B Domain Deleted Recombinant Factor VIII 
The AAPS journal  2007;9(2):E251-E259.
Factor VIII (FVIII) is an important cofactor in the blood coagulation cascade. A deficiency or dysfunction of FVIII causes hemophilia A, a life-threatening bleeding disorder. FVIII circulates in plasma as a heterodimer comprising 6 domains (heavy chain, A1-A2-B and light chain, A3-C1-C2). Replacement therapy using FVIII is the leading therapy in the management of hemophilia A. However, ∼15% to 30% of patients develop inhibitory antibodies that neutralize the activity of the protein. Neutralizing antibodies to epitopes in the lipid binding region of FVIII are commonly identified in patients’ plasma. In this report, we investigated the effect of O-phospho-L-serine (OPLS), which binds to the lipid binding region, on the immunogenicity of B domain deleted recombinant factor VIII (BDDrFVIII). Sandwich enzyme-linked immunosorbent assay (ELISA) studies showed that OPLS specifically bind to the lipid binding region, localized in the C2 domain of the coagulation factor. Size exclusion chromatography and fluorescence anisotropy studies showed that OPLS interfered with the aggregation of BDDrFVIII. Immunogenicity of free-vs BDDrFVIII-OPLS complex was evaluated in a murine model of hemophilia A. Animals administered subcutaneous (sc) injections of BDDrFVIII-OPLS had lower neutralizing titers compared with animals treated with BDDrFVIII alone. Based on these studies, we hypothesize that specific molecular interactions between OPLS and BDDrFVIII may improve the stability and reduce the immunogenicity of BDDrFVIII formulations.
PMCID: PMC2573386  PMID: 17907766
B domain deleted recombinant factor VIII; O-phospho-L-serine; protein formulation; excipient; physical stability; immunogenicity; inhibitor development
12.  New Paradigms and Tools in Drug Design for Pain and Addiction 
The AAPS journal  2006;8(3):E450-E460.
New modalities providing safe and effective treatment of pain, especially prolonged pathological pain, have not appeared despite much effort. In this mini-review/overview we suggest that new paradigms of drug design are required to counter the underlying changes that occur in the nervous system that may elicit chronic pain states. We illustrate this approach with the example of designing, in a single ligand, molecules that have agonist activity at μ and δ opioid receptors and antagonist activities at cholecystokinin (CCK) receptors. Our findings thus far provide evidence in support of this new approach to drug design. We also report on a new biophysical method, plasmon waveguide resonance (PWR) spectroscopy, which can provide new insights into information transduction in G-protein coupled receptors (GPCRs) as illustrated by the δ opioid receptor.
PMCID: PMC1764851  PMID: 17025262
drug design; neuropathic pain; bifunctional ligands; plasmon waveguide resonance spectroscopy; GPCRs; opioid receptors; cholecystokinin receptors
13.  Impact of epigenetic dietary compounds on transgenerational prevention of human diseases 
The AAPS journal  2013;16(1):10.1208/s12248-013-9538-7.
The etiology of most human diseases involves complicated interactions of multiple environmental factors with individual genetic background which is initially generated early in human life, for example, during the processes of embryogenesis and fetal development in utero. Early embryogenesis includes a series of programming processes involving extremely accurate time-controlled gene activation/silencing expressions, and epigenetic control is believed to play a key role in regulating early embryonic development. Certain dietary components with properties in influencing epigenetic processes are believed to have preventive effects on many human diseases such as cancer. Evidence shows that in utero exposure to certain epigenetic diets may lead to reprogramming of primary epigenetic profiles such as DNA methylation and histone modifications on the key coding genes of the fetal genome, leading to different susceptibility to diseases later in life. In this review, we assess the current advances in dietary epigenetic intervention on transgenerational human disease control. Enhanced understanding of the important role of early life epigenetics control may lead to cost-effective translational chemopreventive potential by appropriate administration of prenatal and/or postnatal dietary supplements leading to early disease prevention.
PMCID: PMC3877417  PMID: 24114450
epigenetic; embryogenesis; diet; transgenerational; prevention; human diseases
14.  Inhibitors of Endocannabinoid Metabolizing Enzymes Reduce Precipitated Withdrawal Responses in THC Dependent Mice 
The AAPS journal  2009;11(2):342-352.
Abstinence symptoms in cannabis-dependent individuals are believed to contribute to the maintenance of regular marijuana use. However, there are currently no medications approved by the FDA to treat cannabis related disorders. The only treatment currently shown consistently to alleviate cannabinoid withdrawal in both animals and humans is substitution therapy, using the psychoactive constituent of marijuana, Δ9-tetrahydrocannabinol (THC). However, new genetic and pharmacological tools are available to increase endocannabinoid levels by targeting fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL), the enzymes responsible for the degradation of the endogenous cannabinoid ligands anandamide (AEA) and 2-arachidonoylglycerol (2-AG), respectively. In the present study, we investigated whether increasing endogenous cannabinoids levels, through the use of FAAH (−/−) mice as well as the FAAH inhibitor URB597 or the MAGL inhibitor JZL184, would reduce the intensity of withdrawal signs precipitated by the CB1 receptor antagonist rimonabant in THC-dependent mice. Strikingly, acute administration of either URB597 or JZL184 significantly attenuated rimonabant-precipitated withdrawal signs in THC-dependent mice. In contrast, FAAH (−/−) mice showed identical withdrawal responses as wild-type mice under a variety of conditions, suggesting that the absence of this enzyme across the development of dependence and during rimonabant challenge does not affect withdrawal responses. Of importance, subchronic administration of URB597 did not lead to cannabinoid dependence, and neither URB597 nor JZL184 impaired rotarod motor coordination. These results support the concept of targeting endocannabinoid metabolizing enzymes as a promising treatment for cannabis withdrawal.
PMCID: PMC2691470  PMID: 19430909
cannabis dependence; Fatty Acid Amide Hydrolase (FAAH); Monoacylglycerol Lipase (MAGL); anandamide, 2-arachindonoylglycerol (2-AG)
15.  Interaction of Dicaproyl Phosphatidylserine With Recombinant Factor VIII and Its Impact on Immunogenicity 
The AAPS journal  2006;8(2):E362-E370.
Replacement therapy with exogenous recombinant factor VIII (rFVIII) to control bleeding episodes results in the development of inhibitory antibodies in 15% to 30% of hemophilia A patients. The inhibitory antibodies are mainly directed against specific and universal immunodominant epitopes located in the C2 domain. Previously we have shown that complexation of O-phospho-L-serine (phosphatidylserine head group) with the phospholipid binding region of the C2 domain can lead to an overall reduction in the immunogenicity of rFVIII. Here, we have investigated the hypothesis that dicaproyl phosphatidylserine, a short-chain water-soluble phospholipid, can reduce the immunogenicity of rFVIII. Circular dichroism and fluorescence spectroscopy studies suggest that dicaproyl phosphatidyl-serine interacts with rFVIII, causing subtle changes in the tertiary and secondary structure of the protein. Sandwich enzyme-linked immunosorbent assay studies indicate that dicaproyl phosphatidylserine probably interacts with the phospholipid binding region of the C2 domain. The immunogenicity of FVIII-dicaproyl phosphatidylserine complexes prepared at concentrations above and below the critical micellar concentrations of the lipid were evaluated in hemophilia A mice. Our results suggest that micellar dicaproyl phosphatidylserine may be useful to reduce the immunogenicity of rFVIII preparations.
PMCID: PMC2574005  PMID: 16796387
Hemophilia A; inhibitor development; aggregation; recombinant human factor VIII; protein folding; factor VIII-DCPS complex

Results 1-15 (15)