Liquid chromatography-mass spectrometry assay of a thiadiazole derivative in mice: application to pharmacokinetic studies

A sensitive bioanalytical method for quantitative determination of resiniferatoxin in rat plasma using ultra-high performance liquid chromatography coupled to tandem mass spectrometry and its application in pharmacokinetic study

Resiniferatoxin (RTX) is a daphnane diterpene isolated from the latex of Euphorbia resinifera O. Berg, a potent activator of transient receptor potential vanilloid 1 (TrpV1), with a potency 10³-10⁵ times greater than pure capsaicin. Intravenous administration of RTX at very low concentration improves urodynamic parameters in patients with neurogenic detrusor overactivity and also reduces bladder pain in patients. Herein, a simple, rapid, selective and sensitive method for determination of RTX with silydianin as an internal standard was developed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry with electrospray ionization source (UHPLC-ESI-MS/MS) in multiple reaction monitoring mode. The mass spectrometer was operated in positive electrospray ionization ((+) ESI) mode. Multiple reaction monitoring (MRM) mode was performed with ion pairs of m/z: 629.23→283.2 for RTX and 483.24→153.1 for IS. The limit of detection achieved in this method for RTX was 0.05 ng/mL and had good linearity in calibration range of 0.2-50 ng/mL ( r² = 0.99). Precision and accuracy values were found to be < 15% (within acceptable limit), extraction recovery (≥ 88.2%), matrix effect (≥ 89.7%) and stability were in accordance with the bioanalytical guidelines. The sensitivity of this bio-analytical method supported the successful pharmacokinetic evaluation of RTX on rat plasma (2.5 μg/kg dose; i.v.) and has demonstrated pharmacokinetic parameters V_d and AUC_0-∞ as 191.0 ± 71.31 mL/kg and 981.6 ± 137.40 min*ng/mL, respectively. The clearance was found to be 2.6 ± 0.38 mL/min/kg and half-life was 53.6 ± 23.51 min. This efficient, rapid and reliable method promises the quantification at low concentration of RTX, allowing determination of the pharmacokinetic profile, which is essential in future drug delivery and clinical application.

Improving cyclodextrin complexation of a new antihepatitis drug with glacial acetic acid

The purpose of this study was to develop and evaluate a solid nonaqueous oral dosage form for a new hepatitis C drug, PG301029, which is insoluble and unstable in water. Hydroxypropyl-β-cyclodextrin (HPβCD) and PG301029 were dissolved in glacial acetic acid. The acetic acid was removed by rotoevaporation such that the drug exists primarily in the complexed form. The stability of formulated PG301029 was determined upon dry storage and after reconstitution in simulated intestinal fluid (SIF), simulated gastric fluid (SGF), and water. Formulated PG301029 was found to be stable upon storage and can be reconstituted with water to a concentration 200 times that of the intrinsic solubility. Once reconstituted, the powder dissolves rapidly and PG301029 remains stable for 21 hours in SGF, SIF, and water. The unique use of acetic acid and HPβCD results in a solid dosage form of PG301029 that is both soluble and stable in water.

A novel and rapid LC/MS/MS assay for bioanalysis of Azurin p28 in serum and its pharmacokinetics in mice

Azurin p28 (NSC745104) is a 28 amino acid peptide fragment that inhibits proliferation of human solid and hematological malignancies in vitro and in vivo by reducing proteasomal degradation of oncogene p53. The present study aimed at developing a novel and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the bioanalysis of p28 in mouse serum, and determining Azurin p28 stability and pharmacokinetics in mice after full method validation. Both Azurin p28 and its internal standard MP-1 were separated and extracted from serum by using perchloric acid (7%, v/v) without time-consuming reconstitution. Chromatographic separation of Azurin p28 and MP-1 from the serum matrix was achieved using a C18 column with a gradient elution profile consisting of 5 mM ammonium acetate and acetonitrile, both containing formic acid. Mass analysis was conducted using positive ion electrospray ionization (ESI) and multiple reaction monitoring (MRM). It took 7.5 min to analyze one sample. The validated concentration range of the method extended from 100 to 10,000 ng/ml with accuracies of 85-115% and inter-day precision (CV) of <15%. Inter-day accuracy ranged from 96.4% to 103% and CV ranged from 4.61% to 6.90%. The average recovery of Azurin p28 from mouse serum at three concentrations (200, 1000, and 5000 ng/ml) was determined to be 96.4%. Incubation of Azurin p28 at 37 degrees C for 24h resulted in its degradation 55% in monkey serum, 41% in human serum, and 32-34% in mouse and dog serum. Intravenous administration of Azurin p28 to mice showed its t(1/2 beta) 0.23 h, clearance 1.7 l/kg/h, and volume of distribution at steady state 4.1l/kg. In conclusion, the novel and fast bioanalytical method was proven to be useful for pharmacokinetic profiling of Azurin p28.

Designer antibacterial peptides kill fluoroquinolone-resistant clinical isolates

A significant number of Escherichia coli and Klebsiella pneumoniae bacterial strains in urinary tract infections are resistant to fluoroquinolones. Peptide antibiotics are viable alternatives although these are usually either toxic or insufficiently active. By applying multiple alignment and sequence optimization steps, we designed multifunctional proline-rich antibacterial peptides that maintained their DnaK-binding ability in bacteria and low toxicity in eukaryotes, but entered bacterial cells much more avidly than earlier peptide derivatives. The resulting chimeric and statistical analogues exhibited 8-32 microg/mL minimal inhibitory concentration efficacies in Muller-Hinton broth against a series of clinical pathogens. Significantly, the best peptide, compound 5, A3-APO, retained full antibacterial activity in the presence of mouse serum. Across a set of eight fluoroquinolone-resistant clinical isolates, peptide 5 was 4 times more potent than ciprofloxacin. On the basis of the in vitro efficacy, toxicity, and pharmacokinetics data, we estimate that peptide 5 will be suitable for treating infections in the 3-5 mg/kg dose range.

Oral formulation of a novel antiviral agent, PG301029, in a mixture of gelucire 44/14 and DMA (2:1, wt/wt)

To develop an oral formulation for PG301029, a novel potent agent for the treatment of Hepatitis C virus infection, that not only has very low aqueous solubility but also degrades rapidly in water. The solubility of PG301029 was determined in water, various aqueous media, and several neat organic solvents. The stability of PG301029 was monitored at room temperature in buffers for 4 days, and in several neat organic solvents for up to 8 mo. Drug concentrations were measured by high-performance liquid chromatography (HPLC). Based on solubility and stability data, Gelucire 44/14 and DMA (N,N-dimethylacetamide) at a weight ratio of 2 to 1 were chosen as the formulation vehicle. After the vehicle was prepared, it was maintained in liquid form at approximately 40 degrees C until the PG301029 was dissolved. The final formulation product was a semisolid at room temperature. The bioavailability of the formulation was tested on 4 female BALB/c mice. PG301029 is insoluble in all tested aqueous media, while its solubility is promising in DMA. This compound is unstable in aqueous media and some organic solvents; however, it is stable in DMA. This proposed formulation is able to hold up to 10 mg/mL of drug and is stable at 4 degrees C. The shelf life for this formulation stored at 4degreesC is extrapolated to be greater than 4 years. This formulation dramatically increases the bioavailability of PG301029. This nonaqueous formulation solves the stability, solubility, and bioavailability problems for PG301029. This semisolid formulation can easily be incorporated into soft elastic capsules.

Effect of nanonization on absorption of 301029: ex vivo and in vivo pharmacokinetic correlations determined by liquid chromatography/mass spectrometry

PURPOSE

To compare Caco-2 monolayer permeability and in vivo bioavailability of microparticle with nanoparticle 301029, a thiadiazole derivative, and to determine whether nanonization could improve oral bioavailability of the poorly soluble compound.

METHODS

The mean particle size of 301029 was reduced from 7 microm to 280 nm by pearl milling. In the ex vivo assay, both microparticle and nanoparticle 301029 at the same concentration were separately added to apical side and were collected from basolateral side of Caco-2 monolayer. In the bioavailability study, the two particle sizes of 301029 were orally administered to rats, respectively, and blood samples were collected. Nanoparticle 301029 in culture medium and rat serum was detected by a liquid chomatography-mass spectrometer (LC/MS) coupled with atmospheric pressure chemical ionization (APCI).

RESULTS

Permeability rate and permeated amounts of nanoparticle 301029 across the Caco-2 monolayer were about four times higher than those of microparticle 301029. In a pharmacokinetic study, nanoparticle 301029 showed Tmax about 1 h, whereas the microparticle 301029 showed Tmax at 4 h. The Cmax and AUC of nanoparticle 301029 were 3- to 4-fold greater than those of microparticle 301029, resulting in a significant increase in oral bioavailability of 301029 as compared with microparticle 301029. The ex vivo permeability and in vivo pharmacokinetic data indicate that nanoparticle formulation improves both absorption rate and absorption extent of the poorly soluble drug.

CONCLUSIONS

Nanoparticle formulation enhances both Caco-2 monolayer permeability and rat oral bioavailability of the poorly soluble 301029. The result also demonstrates a close correlation between ex vivo Caco-2 permeability model and in vivo gastrointestinal absorption.