Comparison of an assumption-free Bayesian approach with Optimal Sampling Schedule to a maximum a posteriori Approach for Personalizing Cyclophosphamide Dosing.

STUDY OBJECTIVE: Variable metabolism, dose-dependent efficacy, and a narrow therapeutic target of cyclophosphamide (CY) suggest that dosing based on individual pharmacokinetics (PK) will improve efficacy and minimize toxicity. Real-time individualized CY dose adjustment was previously explored using a maximum a posteriori (MAP) approach based on a five serum-PK sampling in patients with hematologic malignancy undergoing stem cell transplantation. The MAP approach resulted in an improved toxicity profile without sacrificing efficacy. However, extensive PK sampling is costly and not generally applicable in the clinic. We hypothesize that the assumption-free Bayesian approach (AFBA) can reduce sampling requirements, while improving the accuracy of results. DESIGN: Retrospective analysis of previously published CY PK data from 20 patients undergoing stem cell transplantation. In that study, Bayesian estimation based on the MAP approach of individual PK parameters was accomplished to predict individualized day-2 doses of CY. Based on these data, we used the AFBA to select the optimal sampling schedule and compare the projected probability of achieving the therapeutic end points. MEASUREMENTS AND MAIN RESULTS: By optimizing the sampling schedule with the AFBA, an effective individualized PK characterization can be obtained with only two blood draws at 4 and 16 hours after administration on day 1. The second-day doses selected with the AFBA were significantly different than the MAP approach and averaged 37% higher probability of attaining the therapeutic targets. CONCLUSIONS: The AFBA, based on cutting-edge statistical and mathematical tools, allows an accurate individualized dosing of CY, with simplified PK sampling. This highly accessible approach holds great promise for improving efficacy, reducing toxicities, and lowering treatment costs.

Reductive stress in young healthy individuals at risk of Alzheimer disease.

Oxidative stress is a hallmark of Alzheimer disease (AD) but this has not been studied in young healthy persons at risk of the disease. Carrying an Apo ε4 allele is the major genetic risk factor for AD. We have observed that lymphocytes from young, healthy persons carrying at least one Apo ε4 allele suffer from reductive rather than oxidative stress, i.e., lower oxidized glutathione and P-p38 levels and higher expression of enzymes involved in antioxidant defense, such as glutamylcysteinyl ligase and glutathione peroxidase. In contrast, in the full-blown disease, the situation is reversed and oxidative stress occurs, probably because of the exhaustion of the antioxidant mechanisms just mentioned. These results provide insights into the early events of the progression of the disease that may allow us to find biomarkers of AD at its very early stages.

Validation of a novel approach for dose individualization in pharmacotherapy using gabapentin in a proof of principles study.

STUDY OBJECTIVE: To demonstrate the premise of individualized dosing charts (IDCs) as a clinical-bedside decision-support tool to individualize dosage regimens for drugs in which the interpatient variability is controlled by the pharmacokinetic (PK) behavior of the patient, to calculate the optimal sampling schedule (OSS), which minimizes the number of blood samples per patient. The approach is illustrated with available PK data for gabapentin. DESIGN: Retrospective proof of principles study using gabapentin PK data from a published clinical trial. PATIENTS: Nineteen subjects in a trial designed to uncover the importance of the genetic contributions to variability in gabapentin absorption, renal elimination, and transport; subjects were monitored for 36 hours after administration of a single dose of gabapentin 400 mg, and plasma concentrations were determined at 14 time points. MEASUREMENTS AND MAIN RESULTS: When the PK profiles were different between subjects, the IDCs are dramatically different from each other and from the IDC for an "average" patient representing the patient population. The dose amount and dosing interval must be adjusted to maximize the probability of staying within the target concentration range. An optimal sampling methodology based on the assumption-free Bayesian approach is used to distinguish the PK profile of an individual patient from the patient population. In the case of gabapentin, only two optimally selected test blood samples, at 1.5 and 6 hours after administration of a single doses, were necessary. The average sensitivity and the average specificity of the OSS was 99% and 96%, respectively. CONCLUSION: IDCs display the risk of a patient violating the target concentration range for any dosage regimen. They can be used as a clinical-bedside decision-support tool in a patient-physician partnership to decide on a dose amount and dosing interval that are medically acceptable while practical and convenient to ensure compliance. By using the assumption-free Bayesian approach and the OSS, the number of samples required from a new patient to individualize the dosage regimen can be reduced significantly while preserving high levels of sensitivity and specificity. Prospective studies are being planned to validate the encouraging results. This approach can be extended to any drug if PK data and a target concentration range are available for either therapeutic drug monitoring or target concentration intervention.

An experimental comparative study of dexamethasone, melatonin and tacrolimus in noise-induced hearing loss.

CONCLUSION: The calcineurin inhibitor tacrolimus (TCR) and the pineal gland hormone and antioxidant melatonin (MLT) have been shown to possess otoprotective properties against noise-induced hearing loss (NIHL). In contrast, dexamethasone (DXM) was not effective as an otoprotective agent against NIHL. Further studies are needed to understand the exact molecular mechanisms involved. OBJECTIVE: Exposure to noise pollution and use of audio devices for long periods of time at high volume is known to cause hearing loss or NIHL. Our goal was to evaluate the effectiveness of various known compounds such as the anti-inflammatory DXM, the antioxidant MLT and the immunosuppressant TCR against NIHL. MATERIALS AND METHODS: Thirty-two Wistar rats were randomly divided into groups that were then exposed to intense white noise at 120 dB SPL for 4 h. The day before and for a period of 14 days, test groups were administered one of the three compounds. The efficacy of the compounds against NIHL was determined after examining the shifts in the levels of distortion product otoacoustic emissions (DPOAEs) and changes in the threshold of auditory brainstem responses (ABRs). Cytocochleograms and determination of gene expression in whole rat cochlea were carried out at day 21. RESULTS: Treatment with DXM had no otoprotective effect, while animals treated with MLT experienced an improvement in their hearing functionality. This effect, which is probably linked to MLT's ability to reduce c-fos and TNF-alpha gene expression thereby preventing outer hair cell (OHC) loss, was even more pronounced in week 3. For its part, TCR provided protection against injury to the cochlea from week 1, eventually leading to a full recovery in hearing. The compound reduced both c-fos and TNF-alpha expression, as well as OHC loss.

Molecular signatures of vascular injury are associated with early growth of intracerebral hemorrhage.

BACKGROUND AND PURPOSE: To investigate whether molecular markers of inflammation and endothelial injury are associated with early growth of intracerebral hemorrhage (ICH). METHODS: In a multicenter prospective study, we determined concentrations of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), matrix metalloproteinase-9 (MMP-9), and cellular fibronectin (c-Fn) in blood samples obtained on admission from 183 patients with primary hemispheric ICH of <12 hours' duration. Patients had a neurological evaluation and a computed tomography (CT) scan performed at baseline and at 48+/-6 hours. Early growth of the ICH was defined as a volume increase >33% between the 2 CT examinations for ICH with a baseline volume <20 mL and >10% for ICH > or =20 mL. Clinical, radiological, and biochemical predictive factors of ICH enlargement were analyzed by logistic regression analysis. RESULTS: Fifty-four (29.5%) patients showed a relevant early growth of ICH. High leukocyte count and fibrinogen levels, low platelet count, and intraventricular bleeding were associated with early ICH growth in bivariate analyses. Plasma concentrations of IL-6 (median [quartiles]: 19.6 [13.6; 29.9] versus 15.9 [11.5; 19.8] pg/mL), TNF-alpha (13.5 [8.4; 30.5] versus 8.7 [4.7; 13.5] pg/mL), MMP-9 (153.3 [117.7; 204.7] versus 70.6 [47.8; 103.8] ng/mL), and c-Fn (8.8 [6.2; 12.5] versus 2.8 [1.6; 4.2] microg/mL) were significantly higher in patients with early growth of ICH (all P<0.001). C-Fn levels >6 microg/mL (OR, 92; 95%CI, 22 to 381; P<0.0001) and IL-6>24 pg/mL (OR, 16; 95%CI, 2.3 to 119; P=0.005) were independently associated with ICH enlargement in the logistic regression analysis. CONCLUSIONS: Molecular signatures of vascular injury and inflammatory markers in the early acute phase of ICH are associated with subsequent enlargement of the hematoma.