DNA damaging chemotherapy and radiation are widely used standard-of-care modalities for the treatment of cancer. Nevertheless, the outcome for many patients remains poor and this may be attributed, at least in part, to highly effective DNA repair mechanisms. Ataxia-telangiectasia mutated and Rad3-related (ATR) is a key regulator of the DNA-damage response (DDR) that orchestrates the repair of damaged replication forks. ATR is a serine/threonine protein kinase and ATR kinase inhibitors potentiate chemotherapy and radiation. The ATR kinase inhibitor VX-970 (NSC 780162) is in clinical development in combination with primary cytotoxic agents and as a monotherapy for tumors harboring specific mutations. We have developed and validated an LC–MS/MS assay for the sensitive, accurate and precise quantitation of VX-970 in human plasma. A dilute-and-shoot method was used to precipitate proteins followed by chromatographic separation with a Phenomenex Polar-RP 80 Å (4 μm, 50 × 2 mm) column and a gradient acetonitrile-water mobile phase containing 0.1% formic acid from a 50 μL sample volume. Detection was achieved using an API 4000 mass spectrometer using electrospray positive ionization mode. The assay was linear from 3–5,000 ng/mL, proved to be accurate (94.6–104.2%) and precise (<8.4% CV), and fulfilled criteria from the FDA guidance for bioanalytical method validation. This LC-MS/MS assay will be a crucial tool in defining the clinical pharmacokinetics and pharmacology of VX-970 as it progresses through clinical development.
Background:
To address multidrug resistance we developed engineered cationic antimicrobial peptides
(eCAPs). Lead eCAP WLBU2 displays potent activity against drug-resistant bacteria and effectively treats lethal bacterial
infections in mice reducing bacterial loads to undetectable levels in diverse organs.
Background:
To address multidrug resistance we developed engineered cationic antimicrobial peptides
(eCAPs). Lead eCAP WLBU2 displays potent activity against drug-resistant bacteria and effectively treats lethal bacterial
infections in mice reducing bacterial loads to undetectable levels in diverse organs.
Objective:
To support development of WLBU2, we conducted a mass balance study.
Methods:
CD1 mice were administered 10, 15, 20 and 30 mg/kg QDx5 WLBU2 or a single dose of [14C]-WLBU2 at 15
mg/kg IV. Tolerability, tissue distribution and excretion were evaluated with liquid scintillation and HPLCradiochromatography.
Results:
The maximum tolerated dose of WLBU2 is 20 mg/kg IV. We could account for greater than >96% of the
radioactivity distributed within mouse tissues at 5 and 15 min. By 24 h, only ~40-50% of radioactivity remained in the
mice. The greatest % of the dose was present in liver, accounting for ~35% of radioactivity at 5 and 15 min, and ~ 8% of
radioactivity remained at 24 h. High radioactivity was also present in kidneys, plasma, red blood cells and lungs, while
less than 0.2% of radioactivity was present in brain, fat, or skeletal muscle. Urinary and fecal excretion accounted for 12.5
and 2.2% of radioactivity at 24 h.
Conclusion:
WLBU2 distributes widely to mouse tissues and is rapidly cleared with a terminal radioactivity half-life of
22 h, a clearance of 27.4 mL/h/kg, and a distribution volume of 0.94 L/kg. At 2-100 µg-eq/g, the concentrations of 14CWLBU2 appear high enough in the tissues to account for inhibition of microbial growth.
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