Histone Acid Extraction and High Throughput Mass Spectrometry to Profile Histone Modifications in Arabidopsis thaliana

Histone post-translational modifications (PTMs) play important roles in many biological processes, including gene regulation and chromatin dynamics, and are thus of high interest across many fields of biological research. Chromatin immunoprecipitation coupled with sequencing (ChIP-seq) is a powerful tool to profile histone PTMs in vivo. This method, however, is largely dependent on the specificity and availability of suitable commercial antibodies. While mass spectrometry (MS)-based proteomic approaches to quantitatively measure histone PTMs have been developed in mammals and several other model organisms, such methods are currently not readily available in plants. One major challenge for the implementation of such methods in plants has been the difficulty in isolating sufficient amounts of pure, high-quality histones, a step rendered difficult by the presence of the cell wall. Here, we developed a high-yielding histone extraction and purification method optimized for Arabidopsis thaliana that can be used to obtain high-quality histones for MS. In contrast to other methods used in plants, this approach is relatively simple, and does not require membranes or additional specialized steps, such as gel excision or chromatography, to extract highly purified histones. We also describe methods for producing MS-ready histone peptides through chemical labeling and digestion. Finally, we describe an optimized method to quantify and analyze the resulting histone PTM data using a modified version of EpiProfile 2.0 for Arabidopsis. In all, the workflow described here can be used to measure changes to histone PTMs resulting from various treatments, stresses, and time courses, as well as in different mutant lines. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Nuclear isolation and histone acid extraction Basic Protocol 2: Peptide labeling, digestion, and desalting Basic Protocol 3: Histone HPLC-MS/MS and data analysis.

Pharmacokinetics and safety of lefamulin after single intravenous dose administration in subjects with impaired renal function and those requiring hemodialysis

STUDY OBJECTIVE

Lefamulin is a novel IV and oral pleuromutilin recently approved for the treatment of community-acquired bacterial pneumonia (CABP). Given that renal comorbidities are common in patients admitted for CABP, understanding the pharmacokinetics of lefamulin in the face of severe renal impairment, including those requiring hemodialysis, is needed.

DESIGN

Open-label, Phase-1 pharmacokinetic study.

SETTING

Research Study Center.

PATIENTS

Twenty-three matched subjects were included, seven with "Normal" renal function (creatinine clearance >90 ml/min), eight with "Severe" renal impairment (glomerular filtration rate <30 ml/min/1.73 m² ), and eight subjects requiring hemodialysis.

MEASUREMENTS AND MAIN RESULTS

Subjects were administered a single dose of lefamulin IV 150 mg as a 1-h infusion. Subjects in the hemodialysis group started hemodialysis within 1 h after lefamulin infusion (On dialysis), as well as, on a non-dialysis day (Off dialysis). Plasma, urine, and dialysate fluid were collected for 36 h and analyzed for lefamulin and its major metabolite, BC-8041. Lefamulin was primarily excreted non-renally across groups. Statistical analyses revealed lefamulin and BC-8041 pharmacokinetics were similar between Normal and Severe groups, except for renal clearance, which decreased in Severe subjects (mean 1.3 L/h Normal vs. 0.4 L/h Severe). Likewise, lefamulin pharmacokinetics during on and off dialysis were unchanged, with lefamulin not measurably filtered in dialysate fluid. Two, three, and three subjects reported drug-related treatment-emergent adverse events (TEAE) in Normal, Severe, and Hemodialysis groups, respectively. All TEAEs were mild, except one (infusion-site reaction) that was classified as moderate.

CONCLUSION

No dosage adjustment is required for patients with renal impairment, and lefamulin can be administered without regard to hemodialysis timing.

Pharmacokinetics and safety of lefamulin after single intravenous dose administration in subjects with impaired-hepatic function

STUDY OBJECTIVE

Lefamulin is a novel pleuromutilin recently approved by the FDA for the treatment of community-acquired bacterial pneumonia. Given that, lefamulin is primarily metabolized by CYP450 Phase-1 reactions, this study evaluated the pharmacokinetics of IV lefamulin in subjects with various degrees of hepatic impairment as compared with matched healthy subjects.

DESIGN

Open-label, Phase-1 clinical pharmacokinetic study.

SETTING

Research Study Center.

PATIENTS

Twenty-seven subjects; comprised of 11 individuals with normal hepatic function and eight each with moderate or severe hepatic impairment were included, as classified by Child-Pugh scores.

MEASUREMENTS AND MAIN RESULTS

Subjects were administered a single dose of IV lefamulin 150 mg over 1 h. Plasma was collected for 48 h and analyzed for lefamulin and its major metabolite, BC-8041, concentrations in addition to assessing lefamulin plasma protein binding. Pharmacokinetics were evaluated by noncompartmental analysis. Pharmacokinetic parameters were compared using least square geometric mean ratios. Lefamulin was well tolerated in all hepatic function groups. Statistical analyses revealed reductions in C_max and increases in renal clearance for Moderate and Severe groups, as well as, the increased volume of distribution for the Severe group. Lefamulin plasma AUC mean (SD) was similar across groups at 7615 (1554), 8233 (2286), and 8938 (1640) h.ng/mL for Normal, Moderate, and Severe groups, respectively, despite decreased clearance observed primarily during terminal elimination phases. Decreased plasma-protein binding was seen in hepatically-impaired versus normal subjects.

CONCLUSION

Lefamulin was generally well tolerated. Differences in lefamulin and BC-8041 pharmacokinetics were small, relative to the overall variability, and any changes appear to be compensated by increases in renal clearance and decreased protein binding.

Benchmarking Quantitative Performance in Label-Free Proteomics

Previous benchmarking studies have demonstrated the importance of instrument acquisition methodology and statistical analysis on quantitative performance in label-free proteomics. However, the effects of these parameters in combination with replicate number and false discovery rate (FDR) corrections are not known. Using a benchmarking standard, we systematically evaluated the combined impact of acquisition methodology, replicate number, statistical approach, and FDR corrections. These analyses reveal a complex interaction between these parameters that greatly impacts the quantitative fidelity of protein- and peptide-level quantification. At a high replicate number (n = 8), both data-dependent acquisition (DDA) and data-independent acquisition (DIA) methodologies yield accurate protein quantification across statistical approaches. However, at a low replicate number (n = 4), only DIA in combination with linear models for microarrays (LIMMA) and reproducibility-optimized test statistic (ROTS) produced a high level of quantitative fidelity. Quantitative accuracy at low replicates is also greatly impacted by FDR corrections, with Benjamini-Hochberg and Storey corrections yielding variable true positive rates for DDA workflows. For peptide quantification, replicate number and acquisition methodology are even more critical. A higher number of replicates in combination with DIA and LIMMA produce high quantitative fidelity, while DDA performs poorly regardless of replicate number or statistical approach. These results underscore the importance of pairing instrument acquisition methodology with the appropriate replicate number and statistical approach for optimal quantification performance.

1318. Pharmacokinetics and Safety of Cefepime-Taniborbactam (formerly Cefepime/VNRX-5133) in Subjects with Renal Impairment

Background

Taniborbactam is a novel, non-ß-lactam, ß-lactamase inhibitor with activity against serine (Class A, C, D) and metallo (Class B) ß-lactamases including epidemiologically important carbapenemases. Both cefepime and taniborbactam are predominantly renally excreted and are likely to require dose adjustment in patients with renal impairment and end-stage renal disease (ESRD). The current study was designed to evaluate the pharmacokinetics and safety in patients with renal impairment and ESRD.

Methods

This was a Phase 1, open-label study in subjects with normal renal function (eCL_CR ≥ 90 mL/min) matched to subjects with mild, moderate, and severe renal impairment (eGFR 60-89, 30-59, and < 30 mL/min/1.73m², respectively), and patients with ESRD on hemodialysis. Subjects received a single dose of cefepime 2 g and taniborbactam 500 mg; subjects with ESRD received a single dose before HD and after a 9 day washout period, following HD. PK parameters including AUC_0-inf and total body clearance (CL) were evaluated. Safety assessments included adverse events (AEs), vital signs, clinical laboratory evaluations, electrocardiograms, and physical examinations.

Results

Thirty-three subjects were enrolled; 67% male, 58% white and 39% black/African Americans. Median age and BMI were 55.0 years and 29.5 kg/m², respectively. For both cefepime and taniborbactam, exposures increased, and CL decreased with increasing renal impairment (see Table). The hemodialysis extraction ratio was 49.7% and 47.4% for taniborbactam and cefepime respectively. No safety signals were observed and there were no serious adverse events.

Table

Conclusion

Cefepime and taniborbactam CL is similarly reduced with varying degrees of renal impairment. Dialysis removes a high fraction of both drugs. Dose adjustments recommended for cefepime are appropriate for taniborbactam.

Disclosures

Brooke Geibel, BS, Venatorx Pharmaceuticals (Employee, Shareholder) James A. Dowell, PhD, Venatorx Pharmaceuticals (Independent Contractor) Thomas C. Marbury, MD, Venatorx Pharmaceuticals (Independent Contractor) William Smith, MD, Venatorx Pharmaceuticals (Independent Contractor) Paul C. McGovern, MD, Venatorx Pharmaceuticals (Employee) Cynthia Richards, MD, Venatorx Pharmaceuticals (Independent Contractor) Tim Henkel, MD, PhD, Venatorx Pharmaceuticals (Employee, Shareholder)

722. Pharmacokinetics (PK) and Safety of Lefamulin (LEF) After Single Intravenous Dose Administration in Subjects With Impaired Hepatic Function

Background

Patients with chronic liver disease (CLD) have impaired immune function, are prone to community-acquired bacterial pneumonia (CABP), and experience greater morbidity/mortality and healthcare costs than CABP patients without CLD. LEF, a novel pleuromutilin antibiotic (IV/oral) with primary liver elimination, was generally well tolerated and noninferior to moxifloxacin in two phase 3 studies of adults with CABP. We investigated the PK and safety of LEF and its main metabolite, BC-8041, in subjects with hepatic impairment.

Methods

In this open-label study, subjects were allocated to 1 of 3 groups based on hepatic function level; Moderate (Child-Pugh score 7–9) or Severe subjects (Child-Pugh score ≥10) were matched (gender, age, and weight) to subjects in the Normal group (normal hepatic function, no liver cirrhosis). Subjects received a single 1-hour 150 mg LEF infusion. Blood and urine samples were collected predose and over a 48-hour period postdose for PK analysis; plasma and urine were assayed for LEF and BC-8041 using validated assays. Safety assessments included treatment-emergent adverse events (TEAEs), labs, vital signs, and electrocardiograms.

Results

27 subjects enrolled in and completed the study (n = 11, Normal; n = 8, Moderate; n = 8, Severe). Mean LEF and BC-8041 plasma concentration profiles were comparable across all hepatic function groups through the first 12 hours following the start of infusion. Subjects with hepatic impairment had slightly slower rates of elimination in the later elimination phases. LEF and BC-8041 exposures were similar across all hepatic function groups (table), and the majority of LEF and BC-8041 were excreted nonrenally. TEAEs were reported in 2 (18.2%) subjects in the Normal group, 2 (25%) in the Moderate group, and 1 (12.5%) in the Severe group. None of the TEAEs were serious or led to study drug discontinuation. No subject met Hy’s law criteria. Within 4 hours postdose, the maximum mean change from baseline in the QTcF interval was 12.4, 19.2, and 14.1 msec in the Normal, Moderate, and Severe groups, respectively.

Conclusion

No dosage adjustment for LEF appears to be required when treating subjects with hepatic impairment. LEF was generally well tolerated in all subjects regardless of hepatic functional status.

Disclosures

All authors: No reported disclosures

705. Pharmacokinetics (PK) and Safety of Lefamulin (LEF) After Single Intravenous Dose Administration in Subjects With Impaired Renal Function and in Those Requiring Hemodialysis

Background

Renal comorbidities are common in patients hospitalized with community-acquired bacterial pneumonia (CABP). LEF, a novel pleuromutilin antibiotic (IV/oral), was generally well tolerated and noninferior to moxifloxacin in two phase 3 studies of adults with CABP. We investigated the PK and safety of LEF and its main metabolite, BC-8041, in subjects with severe renal impairment and those requiring hemodialysis (HD).

Methods

In this open-label study, subjects were allocated to 1 of 3 groups based on renal function level. Severe subjects (estimated glomerular filtration rate <30 mL/minute/1.73 m², not on HD, Severe) were matched (gender, age, and weight) to subjects with normal renal function (estimated creatinine clearance ≥90 mL/minute, Normal). Subjects in the Normal and Severe groups received a single 1-hour 150 mg LEF infusion. Subjects in the HD group started HD within 1 hour after LEF infusion (“On-dialysis”) and on a nondialysis day (“Off-dialysis”). Blood and urine samples were collected predose and over a 36-hour period postdose for PK analysis; LEF and BC-8041 were assayed in plasma and urine with validated methods. Safety assessments included treatment-emergent adverse events (TEAEs), labs, vital signs, and electrocardiograms.

Results

23 subjects enrolled in and completed the study (n = 7, Normal; n = 8, Severe; n = 8, HD). LEF and BC-8041 pharmacokinetic parameters (table) were comparable between the Normal and Severe groups and between the On-dialysis and Off-dialysis treatment periods for the HD group. The majority of LEF and BC-8041 were excreted nonrenally in Normal and Severe subjects and were not measurably filtered into dialysate. TEAEs were reported in 2 (28.6%) subjects in the Normal group, 4 (50%) in the Severe group, and 4 (50%) in the HD group. None of the TEAEs were serious or led to study drug discontinuation. Within 4 h post-dose, the maximum mean change from baseline in the QTcF interval was 8.9, 6.6, 15.9, and 17.6 msec in the normal, severe, on-dialysis, and off-dialysis groups, respectively.

Conclusion

No dosage adjustment is required for LEF when treating subjects with severe renal impairment, and LEF can be administered without regard to HD timing. LEF was generally well tolerated in all subjects regardless of renal function status.

Disclosures

All authors: No reported disclosures.

TDP-43 interacts with mitochondrial proteins critical for mitophagy and mitochondrial dynamics

Transactive response DNA-binding protein of 43 kDa (TDP-43) functions as a heterogeneous nuclear ribonucleoprotein and is the major pathological protein in frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis/motor neuron disease (ALS/MND). TDP-43 pathology may also be present as a comorbidity in approximately 20-50% of sporadic Alzheimer's disease cases. In a mouse model of MND, full-length TDP-43 increases association with the mitochondria and blocking the TDP-43/mitochondria interaction ameliorates motor dysfunction. Utilizing a proteomics screen, several mitochondrial TDP-43-interacting partners were identified, including voltage-gated anion channel 1 (VDAC1) and prohibitin 2 (PHB2), a crucial mitophagy receptor. Overexpression of TDP-43 led to an increase in PHB2 whereas TDP-43 knockdown reduced PHB2 expression in cells treated with carbonyl cyanide m-chlorophenylhydrazone (CCCP), an inducer of mitophagy. These results suggest that TDP-43 expression contributes to metabolism and mitochondrial function however we show no change in bioenergetics when TDP-43 is overexpressed and knocked down in HEK293T cells. Furthermore, the fusion protein mitofusin 2 (MFN2) interacts in complex with TDP-43 and selective expression of human TDP-43 in the hippocampus and cortex induced an age-dependent change in Mfn2 expression. Mitochondria morphology is altered in 9-month-old mice selectively expressing TDP-43 in an APP/PS1 background compared with APP/PS1 littermates. We further confirmed TDP-43 localization to the mitochondria using immunogold labeled TDP-43 transmission electron microscopy (TEM) and mitochondrial isolation methods There was no increase in full-length TDP-43 localized to the mitochondria in APP/PS1 mice compared to wild-type (littermates); however, using C- and N-terminal-specific TDP-43 antibodies, the N-terminal (27 kDa, N27) and C-terminal (30 kDa, C30) fragments of TDP-43 are greatly enriched in mitochondrial fractions. In addition, when the mitochondrial peptidase (PMPCA) is overexpressed there is an increase in the N-terminal fragment (N27). These results suggest that TDP-43 processing may contribute to metabolism and mitochondrial function.

TDP-43 expression influences amyloidβ plaque deposition and tau aggregation

Although the main focus in Alzheimer's disease (AD) has been an investigation of mechanisms causing Aβ plaque deposition and tau tangle formation, recent studies have shown that phosphorylated TDP-43 pathology is present in up to 50% of sporadic cases. Furthermore, elevated phosphorylated TDP-43 has been associated with more severe AD pathology. Therefore, we hypothesized that TDP-43 may regulate amyloid-beta precursor protein (APP) trafficking and tau phosphorylation/aggregation. In order to examine the role of TDP-43 in AD, we developed a transgenic mouse that overexpresses hippocampal and cortical neuronal TDP-43 in a mouse expressing familial mutations (K595N and M596L) in APP and presenilin 1 (PSEN1ΔE9). In our model, increased TDP-43 was related to increased tau aggregation as evidenced by thioflavin S-positive phosphorylated tau, which may implicate TDP-43 expression in pre-tangle formation. In addition, there was increased endosomal/lysosomal localization of APP and reduced Aβ plaque formation with increased TDP-43. Furthermore, there was decreased calcineurin with elevated TDP-43 expression. Since calcineurin is a phosphatase for TDP-43, the decreased calcineurin expression may be one mechanism leading to an increase in accumulation of diffuse phosphorylated TDP-43 in the hippocampus and cortex. We further show that when TDP-43 is knocked down there is an increase in calcineurin. In our model of selective TDP-43 overexpression in an APP/PSEN1 background, we show that TDP-43 decreases Aβ plaque deposition while increasing abnormal tau aggregation. These observations indicate that TDP-43 may play a role in regulating APP trafficking and tau aggregation. Our data suggest that TDP-43 could be a putative target for therapeutic intervention in AD affecting both Aβ plaque formation and tauopathy.

Histone Lysine-to-Methionine Mutations Reduce Histone Methylation and Cause Developmental Pleiotropy

Epigenetic modifications play critical roles in diverse biological processes. Histone Lys-to-Met (K-to-M) mutations act as gain-of-function mutations to inhibit a wide range of histone methyltransferases and are thought to promote tumorigenesis. However, it is largely unknown whether K-to-M mutations impact organismal development. Using Arabidopsis (Arabidopsis thaliana) as a model system, we discovered that a transgene exogenously expressing histone 3 Lys-36 to Met mutation (K36M) acts in a dominant-negative manner to cause global reduction of H3K36 methylation. Remarkably, this dominant repressive activity is dosage-dependent and causes strong developmental perturbations including extreme branching and early flowering by affecting the expression of genes involved in developmental and metabolic processes. Besides the established pathological roles of K-to-M mutations in tumor cells, we demonstrate a physiological outcome for K-to-M induced H3K36 hypomethylation. This study provides evidence for a conserved dominant-negative inhibitory role of histone K-to-M mutation across the plant and animal kingdoms. We also highlight the unique ability of K36M mutations to alter plant developmental processes leading to severe pleiotropic phenotypes. Finally, our data suggests K-to-M mutations may provide a useful strategy for altering epigenetic landscapes in organisms where histone methyltransferases are uncharacterized.

Iron Deprivation Induces Transcriptional Regulation of Mitochondrial Biogenesis

Mitochondria are essential organelles that adapt to stress and environmental changes. Among the nutrient signals that affect mitochondrial form and function is iron, whose depletion initiates a rapid and reversible decrease in mitochondrial biogenesis through unclear means. Here we demonstrate that, unlike the canonical iron-induced alterations to transcript stability, loss of iron dampens the transcription of genes encoding mitochondrial proteins with no change to transcript half-life. Using mass spectrometry, we demonstrate that these transcriptional changes are accompanied by dynamic alterations to histone acetylation and methylation levels that are largely reversible upon readministration of iron. Moreover, histone deacetylase inhibition abrogates the decreased histone acetylation observed upon iron deprivation and restores normal transcript levels at genes encoding mitochondrial proteins. Collectively, we demonstrate that deprivation of an essential nutrient induces transcriptional repression of organellar biogenesis involving epigenetic alterations.

Increased expression of AT-1/SLC33A1 causes an autistic-like phenotype in mice by affecting dendritic branching and spine formation

The import of acetyl-CoA into the lumen of the endoplasmic reticulum (ER) by AT-1/SLC33A1 regulates Nε-lysine acetylation of ER-resident and -transiting proteins. Specifically, lysine acetylation within the ER appears to influence the efficiency of the secretory pathway by affecting ER-mediated quality control. Mutations or duplications in AT-1/SLC33A1 have been linked to diseases such as familial spastic paraplegia, developmental delay with premature death, and autism spectrum disorder with intellectual disability. In this study, we generated an AT-1 Tg mouse model that selectively overexpresses human AT-1 in neurons. These animals demonstrate cognitive deficits, autistic-like social behavior, aberrations in synaptic plasticity, an increased number of dendritic spines and branches, and widespread proteomic changes. We also found that AT-1 activity regulates acetyl-CoA flux, causing epigenetic modulation of the histone epitope H3K27 and mitochondrial adaptation. In conclusion, our results indicate that increased expression of AT-1 can cause an autistic-like phenotype by affecting key neuronal metabolic pathways.

Quantification of SAHA-Dependent Changes in Histone Modifications Using Data-Independent Acquisition Mass Spectrometry

Histone post-translational modifications (PTMs) are important regulators of chromatin structure and gene expression. Quantitative analysis of histone PTMs by mass spectrometry remains extremely challenging due to the complex and combinatorial nature of histone PTMs. The most commonly used mass spectrometry-based method for high-throughput histone PTM analysis is data-dependent acquisition (DDA). However, stochastic precursor selection and dependence on MS1 ions for quantification impede comprehensive interrogation of histone PTM states using DDA methods. To overcome these limitations, we utilized a data-independent acquisition (DIA) workflow that provides superior run-to-run consistency and postacquisition flexibility in comparison to DDA methods. In addition, we developed a novel DIA-based methodology to quantify isobaric, co-eluting histone peptides that lack unique MS2 transitions. Our method enabled deconvolution and quantification of histone PTMs that are otherwise refractory to quantitation, including the heavily acetylated tail of histone H4. Using this workflow, we investigated the effects of the histone deacetylase inhibitor SAHA (suberoylanilide hydroxamic acid) on the global histone PTM state of human breast cancer MCF7 cells. A total of 62 unique histone PTMs were quantified, revealing novel SAHA-induced changes in acetylation and methylation of histones H3 and H4.

Stoichiometry of site-specific lysine acetylation in an entire proteome

Acetylation of lysine ϵ-amino groups influences many cellular processes and has been mapped to thousands of sites across many organisms. Stoichiometric information of acetylation is essential to accurately interpret biological significance. Here, we developed and employed a novel method for directly quantifying stoichiometry of site-specific acetylation in the entire proteome of Escherichia coli. By coupling isotopic labeling and a novel pairing algorithm, our approach performs an in silico enrichment of acetyl peptides, circumventing the need for immunoenrichment. We investigated the function of the sole NAD(+)-dependent protein deacetylase, CobB, on both site-specific and global acetylation. We quantified 2206 peptides from 899 proteins and observed a wide distribution of acetyl stoichiometry, ranging from less than 1% up to 98%. Bioinformatic analysis revealed that metabolic enzymes, which either utilize or generate acetyl-CoA, and proteins involved in transcriptional and translational processes displayed the highest degree of acetylation. Loss of CobB led to increased global acetylation at low stoichiometry sites and induced site-specific changes at high stoichiometry sites, and biochemical analysis revealed altered acetyl-CoA metabolism. Thus, this study demonstrates that sirtuin deacetylase deficiency leads to both site-specific and global changes in protein acetylation stoichiometry, affecting central metabolism.

c-Jun N-terminal kinase regulates mGluR-dependent expression of post-synaptic FMRP target proteins

Fragile X syndrome (FXS) is caused by the loss of functional fragile X mental retardation protein (FMRP). Loss of FMRP results in an elevated basal protein expression profile of FMRP targeted mRNAs, a loss of local metabotropic glutamate receptor (mGluR)-regulated protein synthesis, exaggerated long-term depression and corresponding learning and behavioral deficits. Evidence shows that blocking mGluR signaling in FXS models ameliorates these deficits. Therefore, understanding the signaling mechanisms downstream of mGluR stimulation may provide additional therapeutic targets for FXS. Kinase cascades are an integral mechanism regulating mGluR-dependent protein translation. The c-Jun N-terminal kinase (JNK) pathway has been shown to regulate mGluR-dependent nuclear transcription; however, the involvement of JNK in local, synaptic signaling has not been explored. Here, we show that JNK is both necessary and sufficient for mGluR-dependent expression of a subset of FMRP target proteins. In addition, JNK activity is basally elevated in fmr1 knockout mouse synapses, and blocking JNK activity reduces the over-expression of post-synaptic proteins in these mice. Together, these data suggest that JNK may be an important signaling mechanism downstream of mGluR stimulation, regulating FMRP-dependent protein synthesis. Furthermore, local, post-synaptic dysregulation of JNK activity may provide a viable target to ameliorate the deficits involved in FXS. Expression of many FMRP target proteins is enhanced in FXS. Here, we evaluated the role of JNKs in FXS. We found that JNK signaling is activated upon mGluR stimulation in wild-type neurons. Conversely, JNK activity is basally elevated in fmr1 knockout. Inhibiting JNK reduced the expression of FMRP target proteins and driving JNK activity increased the expression of these proteins.

Mechanisms of Nrf2 protection in astrocytes as identified by quantitative proteomics and siRNA screening

The Nrf2 (NF-E2 related factor 2)-ARE (antioxidant response element) pathway controls a powerful array of endogenous cellular antioxidant systems and is an important pathway in the detoxification of reactive oxygen species (ROS) in the brain. Using a combination of quantitative proteomics and siRNA screening, we have identified novel protective mechanisms of the Nrf2-ARE pathway against oxidative stress in astrocytes. Studies from our lab and others have shown Nrf2 overexpression protects astrocytes from oxidative stress. However, the exact mechanisms by which Nrf2 elicits these effects are unknown. In this study, we show that induction of Nrf2 reduces levels of reactive oxygen species (ROS) produced by various oxidative stressors and results in robust cytoprotection. To identify the enzymes responsible for these effects, we used stable isotope labeling by amino acids in cell culture (SILAC) and quantitative shotgun proteomics to identify 72 Nrf2-regulated proteins in astrocytes. We hypothesized a subset of these proteins might play a critical role in Nrf2 protection. In order to identify these critical proteins, we used bioinformatics to narrow our target list of proteins and then systematically screened each candidate with siRNA to assess the role of each in Nrf2 protection. We screened each target against H2O2, tert-butyl hydroperoxide, and 4-hydroxynonenal and subsequently identified three enzymes-catalase, prostaglandin reductase-1, and peroxiredoxin-6-that are critical for Nrf2-mediated protection in astrocytes.

Anidulafungin Does Not Require Dosage Adjustment in Subjects With Varying Degrees of Hepatic or Renal Impairment

Two open-label studies assessed the effects of hepatic and renal impairment on anidulafungin pharmacokinetics. A single 50-mg dose was administered intravenously to subjects with varying degrees of hepatic or renal insufficiency or with end-stage renal disease; all were matched to normal healthy controls. Anidulafungin was well tolerated. AUC, CL, C(max), t(max), t(1/2), and V(ss) between renally impaired subjects and controls were not significantly different (P>.05), and no measurable amounts of drug were found in dialysate. The same pharmacokinetic parameters were also not affected (P>.05) by mild or moderate hepatic insufficiency, with respective mean AUCs of 50.6 +/- 11.7 microg x h/mL and 68.6 +/- 14.5 microg x h/mL, compared to 70.0 +/- 13.4 microg x h/mL in controls. Statistically significant decreases (P<05) of AUC (33% change) and C(max) (36% change) in severely hepatically impaired subjects compared to controls--most likely secondary to ascites and edema--were not clinically relevant. Anidulafungin can be safely administered to patients with any degree of hepatic or renal impairment without dosage adjustment and without regard to hemodialysis schedules.

Safety and Pharmacokinetics of Coadministered Voriconazole and Anidulafungin

There is considerable interest in combining echinocandin and triazole antifungal agents for treatment of invasive fungal infections; however, information is needed regarding the tolerability and potential for pharmacokinetic interactions. Anidulafungin is a semisynthetic echinocandin, and voriconazole is an extended-spectrum triazole. In a random sequence, 17 subjects received anidulafungin with placebo, voriconazole with placebo, and anidulafungin with voriconazole. Anidulafungin was administered intravenously: 200 mg on day 1, then 100 mg/d on days 2 through 4. Voriconazole was administered orally: 400 mg every 12 hours on day 1, then 200 mg every 12 hours on days 2 to 4. No dose-limiting toxicities or serious adverse events occurred, and all adverse events were mild and consistent with the known safety profiles of both drugs. Pharmacokinetic parameters were not affected by coadministration. The geometric mean ratio (90% confidence interval) of the combination/drug alone for AUC(SS) was 97.4% (94.9-99.9), 97.4% (92.1-103.0), and 94.4% (87.0-102.5) for anidulafungin, voriconazole, and the voriconazole metabolite, respectively.

Population Pharmacokinetic Analysis of Dalbavancin, a Novel Lipoglycopeptide

Dalbavancin is a lipoglycopeptide antibiotic in clinical development as a once-weekly treatment for serious infections. A total of 532 patients, consisting of 502 patients with skin and soft tissue infections requiring parenteral therapy and 30 patients with catheter-related bloodstream infections, was available for population pharmacokinetic analysis. The majority of patients (78.4%) received dalbavancin intravenously as a 1000-mg dose on day 1 and a single 500-mg dose on day 8. A 2-compartment model with first-order elimination provided the best fit to the data. The clearance of dalbavancin was influenced by body surface area and creatinine clearance, but together they described less than 25% of the interpatient variability. Body surface area was determined to be a predictor of the central volume of distribution. There was no evidence that the presence of metabolic substrates, inhibitors, or inducers of cytochrome P450 or selected concomitant medications influenced the clearance of dalbavancin.

Lack of Pharmacokinetic Interaction Between Anidulafungin and Tacrolimus

The safety and pharmacokinetics of anidulafungin coadministered with tacrolimus were investigated using a single-sequence, open-label design. Healthy volunteers received 5 mg tacrolimus orally on days 1 and 13 of the study. Anidulafungin (200 mg) was administered intravenously on day 4, followed by 100-mg doses on days 5 through 13. Key pharmacokinetic parameters, including C(max), AUC, t((1/2)), CL, and V(ss), were derived from concentration-time data. The 90% confidence intervals (CIs) of the ratios of mean pharmacokinetic parameters of anidulafungin plus tacrolimus to each drug alone were well within the 80% to 125% bioequivalence range, indicating no pharmacokinetic interaction. This ratio was 101.6 (90% CI: 92.77-111.22) for tacrolimus AUC(0-infinity) and 107.2 (90% CI: 105.1-109.4) for anidulafungin AUC(ss). The 2 drugs were well tolerated, and no drug-related serious adverse events were reported. Because of its lack of pharmacokinetic interaction with key immunosuppressive agents, anidulafungin is an important option for the prevention and treatment of invasive fungal infections in transplant recipients.

Assessment of the Safety and Pharmacokinetics of Anidulafungin When Administered With Cyclosporine

Anidulafungin is a novel antifungal agent of the echinocandin class that is intended for the treatment of invasive fungal disease. It is likely that anidulafungin will be coadministered with cyclosporine. In vitro studies and clinical studies were performed to evaluate the effect of anidulafungin on cyclosporine metabolism and to investigate the safety and pharmacokinetics of anidulafungin when concomitantly administered with cyclosporine. The potential for anidulafungin to inhibit the metabolism of cyclosporine was evaluated by pooled human hepatic microsomal protein fractions in vitro, incubating 3H-cyclosporine with different concentrations of anidulafungin. The safety of coadministration and the effects of cyclosporine on the pharmacokinetics of anidulafungin were assessed in a multiple-dose, open-label clinical study of 12 healthy volunteers. Subjects received a 200-mg intravenous loading dose of anidulafungin, followed by a daily 100-mg intravenous maintenance dose on days 2 through 8. An oral solution of cyclosporine (Neoral oral solution; 100 mg/mL) 1.25 mg/kg was also administered to subjects twice daily on days 5 through 8. In the in vitro study, the addition of anidulafungin had no effect on cyclosporine metabolism by human hepatic microsomal protein fractions. In the clinical study, no dose-limiting toxicities or serious adverse events occurred. A small increase in anidulafungin concentrations and drug exposure (22%) was observed after 4 days of dosing with cyclosporine and was not considered to be clinically relevant. The results support the concomitant use of anidulafungin and cyclosporine without the need for dosage adjustments of either drug.

Rat brain neuropeptidomics: tissue collection, protease inhibition, neuropeptide extraction, and mass spectrometric analysis

Due to the complexity of the mammalian central nervous system, neuropeptidomic studies in mammals often yield very complicated mass spectra that make data analysis difficult. Careful sample preparation and extraction protocols must be employed in order to minimize spectral complexity and enable extraction of useful information on neuropeptides from a given sample. Controlling post-mortem protease activity is essential to simplifying mass spectra and to identifying low-abundance neuropeptides in tissue samples. Post-mortem microwave-irradiation coupled with cryostat dissection has proven to be effective in arresting protease activity to allow detection of endogenous neuropeptides instead of protein degradation products.

Identification of astrocyte secreted proteins with a combination of shotgun proteomics and bioinformatics

Astrocytes are important regulators of normal brain function in mammals, including roles in synaptic signaling, synapse formation, and neuronal health and survival. Many of these functions are executed via secreted proteins. To analyze the astrocyte secretome, a combination of shotgun proteomics and bioinformatics was employed to analyze conditioned media from primary murine astrocyte cultures. Both two- and one-dimensional LC-MS/MS were used to analyze astrocyte secreted proteins, resulting in the identification of over 420 proteins. To refine our results, the intracellular protein contaminants were removed in silico using a cytoplasmic control. In additional rounds of refinement, putative secreted proteins were subjected to analysis by SignalP, SecretomeP, and gene ontology analysis, yielding a refined list of 187 secreted proteins. In conclusion, the use of shotgun proteomics combined with multiple rounds of data refinement produced a high quality catalog of astrocyte secreted proteins.

The Nrf2/ARE pathway as a potential therapeutic target in neurodegenerative disease

Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor known to induce expression of a variety of cytoprotective and detoxification genes. Several of the genes commonly regulated by Nrf2 have been implicated in protection from neurodegenerative conditions. Work from several laboratories has uncovered the potential for Nrf2-mediated transcription to protect from neurodegeneration resulting from mechanisms involving oxidative stress. For this reason, Nrf2 may be considered a therapeutic target for conditions that are known to involve free radical damage. Because common mechanisms of neurodegeneration, such as mitochondrial dysfunction and build-up of reactive oxygen species, are currently being uncovered, targeting Nrf2 may be valuable in combating conditions with variable causes and etiologies. Most effectively to target this protein in neurodegenerative conditions, a description of the involvement of Nrf2 and potential for neuroprotection must come from laboratory models. Herein, we review the current literature that suggests that Nrf2 may be a valuable therapeutic target for neurodegenerative disease, as well as experiments that illustrate potential mechanisms of protection.

Comparison of two-dimensional fractionation techniques for shotgun proteomics

Two-dimensional (2D) fractionation is a commonly used tool to increase dynamic range and proteome coverage for bottom-up, shotgun proteomics. However, there are few reports comparing the relative separation efficiencies of 2D methodologies using low-microgram sample quantities. In order to systematically evaluate 2D separation techniques, we fractionated microgram quantities of E. coli protein extract by seven different methods. The first dimension of separation was performed with either reversed-phase high-pressure liquid chromatography (RP-HPLC), gel electrophoresis (SDS-PAGE), or strong cation exchange (SCX-HPLC). The second dimension consisted of a standard reversed-phase capillary HPLC coupled to an electrospray ionization quadrupole time-of-flight mass spectrometer for tandem mass spectrometric analysis. The overall performance and relative fractionation efficiencies of each technique were assessed by comparing the total number of proteins identified by each method. The protein-level RP-HPLC and the high-pH RP-HPLC peptide-level separations performed the best, identifying 281 and 266 proteins, respectively. The online pH variance SCX and the SDS-PAGE returned modest performances with 178 and 139 proteins identified, respectively. The offline SCX had the worst performance with 81 proteins identified. We also examined various chromatographic factors that contribute to separation efficiency, including resolving power, orthogonality, and sample loss.

Population pharmacokinetic modeling of epoetin delta in pediatric patients with chronic kidney disease

This analysis quantifies the population pharmacokinetics of subcutaneous and intravenous epoetin delta, an epoetin produced in a human cell line, in pediatric patients with chronic kidney disease and estimates the effects of covariate factors on epoetin delta and epoetin alfa pharmacokinetic parameters. Erythropoietin serum concentration data, taken from a phase III study conducted in 60 patients aged 1 to 17 years, were best described by a 1-compartment model with first-order absorption and elimination. The typical point estimates were clearance (0.268 L/h), central volume of distribution (1.03 L), absorption rate constant (0.0554 h(-1)), and bioavailability (0.708) for a 35-kg male < or = 10 years who was predialysis and on subcutaneous epoetin delta treatment. Erythropoietin pharmacokinetic parameters were similar in pediatric patients as compared with adults when scaled by weight. The subcutaneous administration of epoetin alfa exhibited lower systemic bioavailability than subcutaneous administration of epoetin delta.

Pharmacokinetics of dalbavancin in plasma and skin blister fluid

OBJECTIVES

Dalbavancin is a novel lipoglycopeptide antibiotic in development for the treatment of complicated skin and skin structure infections (cSSSIs) caused by Gram-positive bacteria. The aim of the present study was to assess the penetration of dalbavancin into skin blister fluid.

METHODS

Nine healthy subjects (five males; ranging in age from 26 to 57 years) were administered a single 30 min intravenous infusion of dalbavancin at a dose of 1000 mg. Skin blisters were induced by application of cantharidin ointment. Plasma and blister fluid samples were collected over 7 days post-dose, and concentrations of dalbavancin were assessed by a validated LC/MS/MS assay. Pharmacokinetics were determined by non-compartmental methods, and drug penetration was assessed based on the ratio of area under the curve (AUC) in the blister fluid versus plasma for each subject.

RESULTS

The mean (SD) peak concentration of dalbavancin in plasma and blister fluid was 285 (31.1) and 67.3 (18.2) mg/L, respectively; the corresponding AUC(Day 7) values were 10 806 (1926) and 6438 (1238) mg . h/L, respectively. The mean (SD) penetration of dalbavancin into blister fluid was 59.6% (6.3%). By Day 7, the mean concentration of dalbavancin in plasma and blister fluid was 46.5 and 30.3 mg/L, respectively.

CONCLUSIONS

Dalbavancin concentrations in blister fluid remained well above the MIC90 values for pathogens commonly implicated in cSSSIs such as Staphylococcus aureus, including methicillin-resistant S. aureus (MIC90 = 0.06 mg/L) and beta-haemolytic streptococci (MIC90 = 0.03 mg/L) through Day 7. These pharmacokinetic data support the use of dalbavancin in the treatment of cSSSIs caused by susceptible Gram-positive pathogens.

Pharmacokinetics and Pharmacodynamics of epoetin delta in two studies in healthy volunteers and two studies in patients with chronic kidney disease

BACKGROUND

Epoetin delta, unlike recombinant erythropoietins, is produced in a human cell line and therefore has a human-type glycosylation profile.

OBJECTIVES

The pharmacokinetics of epoetin delta were examined in 2 studies in healthy volunteers and 2 studies in patients with chronic kidney disease.

METHODS

In study 1, 21 healthy men were randomized to receive epoetin delta 15, 40, or 100 IU/kg IV tiw or placebo for 4 weeks. In study 2, an open-label, cross-over study, 32 healthy volunteers were randomized to receive single doses of epoetin delta 75 IU/kg IV or SC. In study 3, 40 patients receiving hemodialysis were withdrawn from epoetin alfa and randomized to receive epoetin delta or epoetin alfa 50 or 100 IU/kg tiw for 4 weeks. Study 4 was a single-dose study comparing epoetin delta 150 and 300 IU/kg IV or SC in 28 hemodialysis patients.

RESULTS

In study 1, after repeated dosing (day 24) in healthy men, mean C(max) values ranged from 219.9 to 1793.0 enzyme-linked immunosorbent assay units (EU)/L; AUC from 827 to 9318 h x EU/L; C1 from 0.014 to 0.024 L/h per kg; Vd from 0.067 to 0.076 L/kg; and t(1/2) from 2.23 to 3.35 hours. There was evidence of a dose-dependent effect of epoetin delta on hemoglobin levels and hematocrit, with doses of 40 and 100 IU/kg associated with significant increases compared with 15 IU/kg (P < 0.001 for dose trend). The only adverse event occurring in > or = 10% of healthy individuals in study 1 was headache (1 [20.0%] in the epoetin delta 15 IU-kg group, 3 [60.0%] in the epoetin delta 100-IU/kg group, 2 [33.3%] in the placebo group). In study 2 in healthy volunteers, mean values for epoetin delta 75 IU/kg IV were 1771 EU/L for C(max), 10,632 h x EU/L for AUC, 0.010 L/h per kg for Cl, 0.074 L/kg for Vd, and 5.12 hours for t(1/2); the corresponding values for epoetin delta 75 IU/kg SC were 113 EU/L, 3231 h x EU/L, 0.035 L/h per kg, 0.760 L/kg, and 14.90 hours. The serum epoetin delta concentration peaked after 10.9 hours with subcutaneous administration. The most common adverse event in study 2 was back pain (10 [31.3%] individuals). In study 3 in patients receiving hemodialysis, mean values for C(max) and AUC with a single dose of epoetin delta 50 IU/kg were 1103 EU/L and 10,896 h x EU/L, respectively, and with the corresponding dose of epoetin alfa were 1354 EU/L and 9957 h x EU/L. Values for the 100-IU/kg doses were approximately double those for the 50-IU/kg doses. Values for Cl, Vd, and t(1/2) were numerically similar for epoetin delta and epoietin alfa across doses. Epoetin delta 100 IU/kg was associated with a numerically greater rate of increase in hemoglobin compared with the 50-IU/kg dose (mean, 0.025 vs -0.004, respectively); the results were similar for epoetin alfa (0.029 vs -0.001). The difference between epoetin alfa and epoetin delta was not statistically significant. The most common adverse events were related to edema (peripheral edema: 60%/50% for epoetin delta 50/100 IU/kg and 60%/60% for epoetin alfa 50/100 IU/kg; facial edema: 30%/30% and 50%/70%, respectively; generalized edema: 50%/30% and 40%/40%). In study 4 in patients receiving hemodialysis, mean C(max) values with epoetin delta 150 and 300 IU/kg IV were 3257 and 4770 EU/L, respectively; the corresponding mean values were 36,208 and 77,736 h x EU/L for AUC, 0.007 and 0.005 L/h per kg for Cl; 0.097 L/kg for Vd in both groups; and 9.9 and 13.2 hours for t(1/2). With epoetin delta 150 and 300 IU/kg SC, the respective values were 162.2 and 467.7 EU/L, 9547 and 27,888 h x EU/L, 0.026 and 0.020 L/h per kg, 1.28 and 0.78 L/kg, and 33.1 and 27.8 hours. The only adverse event occurring in > or = 10% of subjects was headache (2 [40.0%] in the epoetin delta 150-IU/kg IV group, 3 [50.0%] in the epoetin delta 300-IU/kg SC group). No neutralizing anti-erythropoietin antibodies were detected in any individual. The bioavailability of subcutaneous epoetin delta is approximately 30%, and concentrations peak later and decline more slowly than with intravenous injection. Pharmacokinetic parameters in hemodialysis patients were similar to those in healthy individuals, although AUC and t(1/2) were numerically higher (by 49% and 34%, respectively).

CONCLUSIONS

These studies in healthy volunteers and patients with chronic kidney disease indicate that the pharmacokinetics of epoetin delta are dose dependent but nonlinear, leading to dose-dependent increases in hemoglobin levels. The pharmacodynamic response to epoetin delta appeared to be as expected for an epoetin.

Distribution of radioactivity in bone and related structures following administration of [14C]dalbavancin to New Zealand white rabbits

Penetration of dalbavancin into noninfected bone and joint tissues was assessed after an intravenous dose of 20 mg/kg (of body weight) [(14)C]dalbavancin given to rabbits. Drug-derived radioactivity, determined over 14 days by either liquid scintillation counting or autoradiography, remained above the MIC for common gram-positive pathogens that cause bone and joint infections.

Rat Neuropeptidomics by LC−MS/MS and MALDI−FTMS: Enhanced Dissection and Extraction Techniques Coupled with 2D RP-RP HPLC

Recently developed sample preparation techniques employing microwave irradiation have enabled the comprehensive study of endogenous mammalian neuropeptides. These methods reduce interference from post-mortem protein degradation by deactivating proteases via heat denaturation. Alternatively, we have developed a protocol using cryostat dissection and a boiling extraction buffer to achieve a similar effect. This novel methodology greatly reduces post-mortem protein contamination and increases neuropeptide identification without the use of specialized equipment. In addition, a 2D HPLC scheme employing differential pH selectivity in the first and second dimensions has been used to enhance neuropeptidome coverage. By using our novel dissection protocol in tandem with 2D RP-RP HPLC, we were able to identify a total of 56 peptides from known neuropeptide precursors, including 17 previously unidentified peptides. The use of cryostat dissection and two-dimensional RP-RP HPLC enhances the detection of novel neuropeptides by deactivating proteases and reducing sample complexity.

Safety and pharmacokinetics of intravenous anidulafungin in children with neutropenia at high risk for invasive fungal infections

Anidulafungin is an echinocandin with activity against Candida species and Aspergillus species. Adult dosages under study are 50 mg/day for esophageal candidiasis and 100 mg/day for invasive candidiasis and aspergillosis. Little is known, however, about the safety and pharmacokinetics of anidulafungin in children. A multicenter, ascending-dosage study of neutropenic pediatric patients was therefore conducted. Patients were divided into two age cohorts (2 to 11 years and 12 to 17 years) and were enrolled into sequential groups to receive 0.75 or 1.5 mg/kg of body weight/day. Blood samples were obtained following the first and fifth doses. Anidulafungin was assayed in plasma, and pharmacokinetic parameters were determined. Safety was assessed using National Cancer Institute (NCI) common toxicity criteria. Pharmacokinetic parameters were determined for 12 patients at each dosage (0.75 mg/kg/day or 1.5 mg/kg/day). Concentrations and drug exposures were similar for patients between age cohorts, and weight-adjusted clearance was consistent across age. No drug-related serious adverse events were observed. One patient had fever (NCI toxicity grade of 3), and one patient had facial erythema, which resolved with slowing the infusion rate. Anidulafungin in pediatric patients was well tolerated and can be dosed based on body weight. Pediatric patients receiving 0.75 mg/kg/day or 1.5 mg/kg/day have anidulafungin concentration profiles similar to those of adult patients receiving 50 or 100 mg/day, respectively.

Pharmacokinetics of gemtuzumab ozogamicin as a single-agent treatment of pediatric patients with refractory or relapsed acute myeloid leukemia

Gemtuzumab ozogamicin is currently approved to treat CD33-positive acute myeloid leukemia (AML) in first relapse in patients older than age 60 years. The objective of this study was to characterize the pharmacokinetics of gemtuzumab ozogamicin in pediatric patients with relapsed or refractory AML. The study population comprised 29 subjects younger than age 18 with AML in first relapse. Dosages of 6, 7.5, and 9 mg/m(2) were administered during the study. Pharmacokinetic parameters were determined following each dose for hP67.6, total calicheamicin derivatives, and unconjugated calicheamicin derivatives. hP67.6 pharmacokinetic parameters had a consistent and statistically significant change between the first and second doses. Increases in AUC and decreases in both CL and V(ss) from the first dose to the second dose were consistent with those of the adult population. Changes between dose periods for total calicheamicin derivatives and unconjugated calicheamicin derivatives were consistent with those of hP67.6. Changes in pharmacokinetic parameters between dose periods are attributed to saturation of CD33 binding sites and diminished clearance resulting from a lower peripheral blast burden and antigen. Children receiving 9 mg/m(2) had the following hP67.6 pharmacokinetic parameters: C(max), 3.47+/-1.04 mg/L; AUC, 136 +/- 107 mg x h/L; CL, 0.12 +/- 0.15 L/h/m(2); V(ss), 6.5 +/- 5.5 L; and t(1/2), 64 +/- 44 h after their first dose. Mean pharmacokinetic values are similar to values reported in adults. Individual children demonstrated large intersubject variability, similar to adults. The pharmacokinetics of gemtuzumab ozogamicin in pediatric patients closely follow the profile and variability of adult patients.

Population pharmacokinetic analysis of anidulafungin, an echinocandin antifungal

The objective of this analysis was to describe the pharmacokinetic characteristics of anidulafungin in patients with serious fungal disease based on pharmacokinetic data collected during four recently completed or ongoing Phase II/III clinical studies. A total of 600 anidulafungin plasma samples from 225 patients across the four studies were available for analysis. Patients received daily intravenous infusions of 50, 75, or 100 mg anidulafungin, preceded by a loading dose that was twice the daily dose. The analysis population consisted of 129 patients with esophageal candidiasis, 87 with invasive candidiasis, 7 with invasive aspergillosis, and 2 with azole refractory mucosal candidiasis. A population analysis approach was used to develop a steady-state pharmacokinetic model for anidulafungin, assess the significance of possible covariates, and determine the amount of intersubject and random residual variability. A two-compartment model with first-order elimination provided the best fit to the data. The clearance of anidulafungin was influenced by weight and gender, and subjects in the invasive candidiasis study had a typical clearance that was approximately 30% higher than subjects from other studies. Weight was determined to be a predictor of the central volume of distribution. The covariates on clearance accounted for less than 20% of the intersubject variability and therefore are deemed to be of little clinical relevance. There was no evidence that the presence of rifampin or metabolic substrates, inhibitors, or inducers of cytochrome p450 influenced the clearance of anidulafungin. This indicates that dosing adjustments are not necessary when anidulafungin is administered in the presence of medications falling into these classifications.

Once-Weekly Dalbavancin versus Standard-of-Care Antimicrobial Regimens for Treatment of Skin and Soft-Tissue Infections

Dalbavancin, a novel glycopeptide with a long elimination half-life ( approximately 9-12 days), was compared to standard antimicrobial therapy for skin and soft-tissue infections (SSTIs). In a randomized, controlled, open-label, phase 2 proof-of-concept trial, adults received 1100 mg of dalbavancin (as a single intravenous infusion), 1000 mg of dalbavancin intravenously and then 500 mg intravenously 1 week later, or a prospectively defined standard-of-care regimen. A gram-positive pathogen was isolated from samples obtained from 41 (66%) of 62 patients at baseline; Staphylococcus aureus was the most prevalent species (83% of pathogens). Clinical success rates at a follow-up visit (test of cure) were 94.1% among patients treated with 2 doses of dalbavancin, 61.5% among patients treated with 1 dose of dalbavancin, and 76.2% among patients treated with a standard-of-care regimen. All treatment regimens were well tolerated; drug-related adverse reaction rates were similar across the 3 groups. These findings suggest that a regimen of 2 doses of dalbavancin administered 1 week apart is effective in the treatment of complicated, gram-positive bacterial SSTIs and warrants further study.

Licensure of gemtuzumab ozogamicin for the treatment of selected patients 60 years of age or older with acute myeloid leukemia in first relapse

This paper discusses background information and the body of clinical data that has been accumulated to demonstrate the efficacy and safety of gemtuzumab ozogamicin (Mylotarg, Wyeth Pharmaceuticals, Philadelphia, PA). Based on these data, gemtuzumab ozogamicin was approved by the United States Food and Drug Administration for the treatment of patients with CD33-positive acute myeloid leukemia in first relapse who are 60 years of age or older and who are not considered candidates for other cytotoxic chemotherapy. The recommended dosage of gemtuzumab ozogamicin is 9 mg/m2, administered as a 2-hour intravenous infusion for a total of 2 doses with 14 days between doses.

Pharmacokinetics of gemtuzumab ozogamicin, an antibody-targeted chemotherapy agent for the treatment of patients with acute myeloid leukemia in first relapse

The purpose of this study was to characterize the pharmacokinetics of gemtuzumab ozogamicin (Mylotarg; Wyeth-Ayerst Laboratories, St. Davids, PA) in patients with acute myeloid leukemia (AML) in first relapse. Gemtuzumab ozogamicin is an antibody-chemotherapeutic conjugate characterized as antibody-targeted chemotherapy, consisting of an engineered human anti-CD33 antibody (hP67.6) linked to a potent cytotoxic agent, N-acetyl-gamma calicheamicin DMH. The pharmacokinetics of gemtuzumab ozogamicin was evaluated in 59 adult AML patients in first relapse, enrolled in a phase II study. Plasma was collected following each dose at specified times, and the pharmacokinetics was characterized by measures of hP67.6, total calicheamicin derivatives, and unconjugated calicheamicin derivatives. After administration of the first 9 mg/m2 dose of gemtuzumab ozogamicin, the pharmacokinetic parameters (mean +/- SD) of hP67.6 following the first dose were as follows: peak plasma concentration, 2.86 +/- 1.35 mg/L; AUC, 123 +/- 105 mg x h/L; t 1/2, 72.4 +/- 42.0 hours; and clearance, 0.265 +/- 0.229L/h. Increased concentrations were observed after the second dose and are believed to be due to a decrease in clearance by CD33-positive blast cells, a result of the reduced tumor burden following the first dose. The concentration profiles of calicheamicin followed the same time course as hP67.6, evidence that calicheamicin remained conjugated to the antibody and delivered to leukemic cells. No relationship was found between plasma concentration and response at the recommended dose. The pharmacokinetics of gemtuzumab ozogamicin has been characterized in AML patients receiving doses at the proposed therapeutic level.

Impact of age and gender on the pharmacokinetics of gemtuzumab ozogamicin

STUDY OBJECTIVE

To determine the pharmacokinetic parameters of the components of gemtuzumab ozogamicin and to assess the possible influence of age and gender on the values.

DESIGN

Phase II, multicenter, open-label, nonrandomized, parallel study

SETTING

Hospitals and outpatient oncology clinics.

PATIENTS

Fifty-eight patients with acute myeloid leukemia in first relapse participated. Demographic data included 29 men and 29 women; 34 were younger than 60 years of age (mean age 53+/-16 yrs).

INTERVENTION

Patients received gemtuzumab ozogamicin as a single 2-hour infusion of 9 mg/m2. Serial plasma samples were collected over 10 days after the beginning of the infusion.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of components of gemtuzumab ozogamicin (hP67.6 antibody, total and unconjugated calicheamicin derivatives) were measured by validated enzyme-linked immunosorbent assays. Pharmacokinetic parameters were determined by noncompartmental methods and comparisons between groups were made by analysis of variance. No significant differences were seen between men and women or between those over 60 and those less than 60 years of age in maximum concentration, time to maximum concentration, area under the curve, clearance, or volume of distribution for components of gemtuzumab ozogamicin.

CONCLUSION

No differences occur in the pharmacokinetics of the components of gemtuzumab ozogamicin (hP67.6 or calicheamicin) based on gender or age.

Evaluating possible pharmacokinetic interactions between tobramycin, piperacillin, and a combination of piperacillin and tazobactam in patients with various degrees of renal impairment

A study was performed to further investigate the apparent instability of tobramycin when coadministered with piperacillin/tazobactam in subjects with renal impairment. Twenty-six otherwise healthy volunteers between 23 and 74 years of age were studied. Eight subjects had moderate renal impairment, 10 had mild renal impairment, and 8 had normal renal function. Each subject received single doses of piperacillin/tazobactam and tobramycin alone as well as combined doses in a randomized, three-way crossover design. The subjects with normal renal function also received combined doses of piperacillin and tobramycin. Considerable care was taken to protect against in vitro inactivation of plasma and urine samples after collection. No systematic changes in pharmacokinetic parameters were observed. It is concluded that piperacillin, either alone or with tazobactam, did not change the pharmacokinetics of tobramycin in subjects with renal impairment. The apparent in vivo inactivation of tobramycin in the presence of piperacillin or piperacillin/tazobactam reported by others may be an artifact of ex vivo inactivation.

Noninvasive measurements for studying the tumoral pharmacokinetics of platinum anticancer drugs in solid tumors

An effective methodology to determine the amount of cisplatin or carboplatin at the solid tumor site in a noninvasive manner may enable clinicians to design drug regimens based on an individual's in situ pharmacokinetics. Such noninvasive methods may allow optimization of an individual's drug exposure at the target site, as well as provide a screening measure to determine individual efficacy based on exposure to these platinated drugs. 195mPt appears to be the radionuclide of platinum most suitable for radiolabeling cisplatin or carboplatin, and an analysis is presented of the methods available for preparing such radiolabeled drugs. The use of this methodology is illustrated in detail in studies in animals, as well as some preliminary studies in humans. The animals used were Sprague Dawley rats bearing the Walker 256 carcinoma, and drug biodistribution was studied following administration of cisplatin or carboplatin radiolabeled with 195mPt. This radionuclide permitted noninvasive imaging of the drug and its metabolites at the tumor site and at selected organs. The results obtained show an ability to estimate the amount of platinated drug species in the tumor environment using a noninvasive methodology. Various compartmental models were tested, some of which could be validated experimentally. This noninvasive method is able to provide individual estimates of the active component of the drug at the target site, and is therefore a method that can be implemented in human studies.

Artificial neural networks applied to the in vitro-in vivo correlation of an extended-release formulation: initial trials and experience

Artificial neural networks applied to in vitro-in vivo correlations (ANN-IVIVC) have the potential to be a reliable predictive tool that overcomes some of the difficulties associated with classical regression methods, principally, that of providing an a priori specification of the regression equation structure. A number of unique ANN configurations are presented, that have been evaluated for their ability to determine an IVIVC from different formulations of the same product. Configuration variables included a combination of architectural structures, learning algorithms, and input-output association structures. The initial training set consisted of two formulations and included the dissolution from each of the six cells in the dissolution bath as inputs, with associated outputs consisting of 1512 pharmacokinetic time points from nine patients enrolled in a crossover study. A third formulation IVIVC data set was used for predictive validation. Using these data, a total of 29 ANN configurations were evaluated. The ANN structures included the traditional feed forward, recurrent, jump connections, and general regression neural networks, with input-output association types consisting of the direct mapping of the dissolution profiles to the pharmacokinetic observations, mapping the individual dissolution points to the individual observations, and using a "memorative" input-output association. The ANNs were evaluated on the basis of their predictive performance, which was excellent for some of these ANN models. This work provides a basic foundation for ANN-IVIVC modeling and is the basis for continued modeling with other desirable inputs, such as formulation variables and subject demographics.

The effects of anesthesia on the biodistribution of drugs in rats: a carboplatin study

PURPOSE

Anesthetics can alter the biodistribution profile of drugs and, consequently, the regional pharmacokinetics of antineoplastic drugs at the tumor site. The effect of coadministered anesthetics on the biodistribution profile of carboplatin was studied in rats.

METHODS

Female Wistar rats were used to compare the effects of ketamine/xylazine, thiopental and pentobarbital on the biodistribution of 30 mg/kg radiolabelled 195mPt-carboplatin administered intravenously, with conscious rats as the control group. Blood and urine samples were collected between 5 and 120 min.

RESULTS

The percentage values of the injected dose of platinum per ml (%ID/ml) in plasma at the final time-point were respectively, 0.557%, 0.156%, 0.115% and 0.086%, in pentobarbital-, ketamine/xylazine- and thiopental-injected rats, and in conscious animals. Following the same sequence of groups, the %ID/ml values of platinum in the cumulative urine were 0.001%, 0.619%, 0.184% and 0.118%, respectively. Urine output varied from very little in the pentobarbital group, to several milliliters in the other groups.

CONCLUSIONS

There was an increase of almost 100-fold in total platinum uptake in the kidneys, cerebrum and cerebellum of rats receiving pentobarbital over the uptake in the control rats, whereas the biodistribution profile of the thiopental group had the least variance. These results demonstrate the importance of anesthetic selection in animal pharmacokinetic studies, as it influences the biodistribution and pharmacokinetic profile of the drug being studied.