Pharmacometabonomic Prediction of Busulfan Clearance in Hematopoietic Cell Transplant Recipients

Intravenous (IV) busulfan doses are often personalized to a concentration at steady state (Css) using the patient’s clearance, which is estimated with therapeutic drug monitoring. We sought to identify biomarkers of IV busulfan clearance using a targeted pharmacometabonomics approach. A total of 200 metabolites were quantitated in 106 plasma samples, each obtained before IV busulfan administration in hematopoietic cell transplant (HCT) recipients. Both univariate linear regression with false discovery rate (FDR) and pathway enrichment analyses using the Global test were performed. In the univariate analysis, glycine, <i>N-</i>acetylglycine, 2-hydroxyisovaleric acid, creatine, serine, and tyrosine were statistically significantly associated with IV busulfan clearance at <i>P</i> < 0.05, with the first three satisfying the FDR of <i>q</i> < 0.1. Using pathway enrichment analysis, the glycine, serine, and threonine metabolism pathway was statistically significantly associated with IV busulfan clearance at <i>P</i> < 0.05 and <i>q</i> < 0.1, and a pathway impact >0.1. Glycine is a component of glutathione, which is conjugated with busulfan via glutathione transferase enzymes. These results demonstrate the potential utility of pharmacometabonomics to inform IV busulfan dosing. Future studies are required to validate these findings

An open-label, non-randomized study of the pharmacokinetics of the nutritional supplement nicotinamide riboside (NR) and its effects on blood NAD+ levels in healthy volunteers

<div><p>Objectives</p><p>The co-primary objectives of this study were to determine the human pharmacokinetics (PK) of oral NR and the effect of NR on whole blood nicotinamide adenine dinucleotide (NAD+) levels.</p><p>Background</p><p>Though mitochondrial dysfunction plays a critical role in the development and progression of heart failure, no mitochondria-targeted therapies have been translated into clinical practice. Recent murine studies have reported associations between imbalances in the NADH/NAD+ ratio with mitochondrial dysfunction in multiple tissues, including myocardium. Moreover, an NAD+ precursor, nicotinamide mononucleotide, improved cardiac function, while another NAD+ precursor, nicotinamide riboside (NR), improved mitochondrial function in muscle, liver and brown adipose. Thus, PK studies of NR in humans is critical for future clinical trials.</p><p>Methods</p><p>In this non-randomized, open-label PK study of 8 healthy volunteers, 250 mg NR was orally administered on Days 1 and 2, then uptitrated to peak dose of 1000 mg twice daily on Days 7 and 8. On the morning of Day 9, subjects completed a 24-hour PK study after receiving 1000 mg NR at t = 0. Whole-blood levels of NR, clinical blood chemistry, and NAD+ levels were analyzed.</p><p>Results</p><p>Oral NR was well tolerated with no adverse events. Significant increases comparing baseline to mean concentrations at steady state (C_ave,ss) were observed for both NR (<i>p</i> = 0.03) and NAD+ (<i>p</i> = 0.001); the latter increased by 100%. Absolute changes from baseline to Day 9 in NR and NAD+ levels correlated highly (R² = 0.72, <i>p</i> = 0.008).</p><p>Conclusions</p><p>Because NR increases circulating NAD+ in humans, NR may have potential as a therapy in patients with mitochondrial dysfunction due to genetic and/or acquired diseases.</p></div

Comparisons of pre-specified endpoints between baseline (Day 1) and Day 9.

<p>Parameter values reported as mean ± standard deviation.</p

Line plots of concentrations (μM) of NAD+ and NR at Day 1 (baseline) and the average concentration at steady state (C_ave,ss).

<p>Each subject is depicted in a different color and the time points are connected by a line. The <i>p</i> value for a paired Student’s <i>t</i> test is shown in the upper left corner of each plot.</p

Comparisons of other variables of interest between Day 1 and Day 9.

<p>Parameter values reported as mean ± standard deviation.</p

Correlation between absolute changes in NAD+ concentration versus NR concentration.

<p>Each subject is plotted as a different color. The blue line shows a linear regression of the change in NAD+ given the change in NR, and the shaded area shows the 95% confidence interval of that regression.</p

Study CONSORT flowchart.

<p>Study CONSORT flowchart.</p

Comparisons of blood NR and NAD+ levels at baseline (Day 1) with trough, peak, C_ave,ss concentrations on Day 9.

<p>Values shown are mean ± standard deviation (n = 8); <i>p</i> values corrected for multiple testing using the Holm method.</p

Concentration-time curves for NR (top) and NAD+ (bottom).

<p>Each subject is depicted in a different color with time points connected by a line. The y-axis depicts NR and NAD+ concentrations in μM, and the x-axis depicts values on Day 1 (baseline) and then time post-dose in hours on Day 9. The baseline time point was collected pre-dose on Day 1 of the trial.</p

Typical ¹H NMR spectrum of an aqueous extract (in deuterated water) of a NR capsule obtained on a bruker AVANCE III 800 MHz nuclear magnetic resonance (NMR) spectrometer.

<p>NMR signals that arise from NR are labeled with the corresponding location of the hydrogen atom(s) as shown in the molecular structure of NR (inset). TSP [3-(trimethylsilyl)propionic acid-2,2,3,3-d₄ sodium salt] was used as an internal standard to quantify the amount and purity of NR in the capsules. The purity of NR was calculated based on integration of all the peaks and was in the range of 98–99%.</p