P. S. Suresh

Review of bioanalytical assays for the quantitation of various HDAC inhibitors such as vorinostat, belonistat, panobinostat, romidepsin and chidamine.

Histone deacetylase inhibitors (HDAC inhibitors) are used to treat malignancies such as cutaneous T cell lymphoma and peripheral T cell lymphoma. Only four drugs are approved by the US Food and Drug Administration, namely vorinostat, romidepsin, panobinostat and belinostat, while chidamide has been approved in China. There are a number of bioanalytical methods reported for the measurement of HDAC inhibitors in clinical (human plasma and serum) and preclinical (mouse plasma, rat plasma, urine and tissue homogenates, etc.) studies. This review covers various HDAC inhibitors such as vorinostat, romidepsin, panobinostat, belinostat and chidamide. In addition to providing a comprehensive review of the available methods for the above mentioned HDAC inhibitors, it also provides case studies with perspectives for chosen drugs. Based on the review, it is concluded that the published methodologies using either HPLC or LC-MS/MS are well suited for the quantification of HDAC inhibitors in various biological fluids to delineate pharmacokinetic data.

A highly sensitive LC-MS/MS method for the determination of S-citalopram in rat plasma: application to a pharmacokinetic study in rats

A highly sensitive, rapid assay method has been developed and validated for the estimation of S-citalopram (S-CPM) in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive-ion mode. The assay procedure involves a simple liquid-liquid extraction of S-CPM and phenacetin (internal standard, IS) from rat plasma with t-butyl methyl ether. Chromatographic separation was operated with 0.2% formic acid:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Symmetry Shield RP(18) column with a total run time of 3.0 min. The MS/MS ion transitions monitored were 325.26 → 109.10 for S-CPM and 180.10 → 110.10 for IS. Method validation and pre-clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.5 ng/mL and the linearity was observed from 0.5 to 5000 ng/mL. The intra- and inter-day precisions were in the range of 1.14-5.56 and 0.25-12.3%, respectively. This novel method has been applied to a pharmacokinetic study and to estimate brain-to-plasma ratio of S-CPM in rats.

Synergy effect in the photocatalytic degradation of textile dyeing waste water by using microwave combustion synthesized zinc oxide supported activated carbon

Zinc oxide nanoparticle supported activated carbon (ZSAC) was successfully prepared using a cost effective microwave irradiation method. The earned UV light sensitive ZSAC composites were characterized using powder X-ray diffraction (XRD), high resolution scanning electron microscopy with energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The optical properties of ZSAC composites were investigated using UV–Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy, which exposed prolonged light absorption in UV light region and hold better charge separation capability, respectively as compared to pure ZnO. The photocatalytic activity was tested by the degradation of textile dye waste water (TDW) under UV light irradiation. Chemical oxygen demand of TDW was calibrated before and after the photocatalysis experiment under UV light to evaluate the mineralization of wastewater. The results demonstrated that ZSAC composites showed imposing photocatalytic enrichment over pure ZnO and commercial TiO2 (Degussa P25). The coordinated blending of the oxygen vacant sites, structural defects of ZnO along with electron transmission capacity and presence of surface oxygen on AC has led to the lasting light absorption, delayed charge recombination, and sustenance, which favor the enrichment of the photocatalytic activity of ZSAC.

Development of an LC‐MS/MS method for determination of bicalutamide on dried blood spots: application to pharmacokinetic study in mice

A rapid and highly sensitive assay method has been developed and validated for the estimation of bicalutamide (BCL) on mouse dried blood spots (DBS) using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative-ion mode. The assay procedure involves a simple liquid extraction of BCL and tolbutamide (internal standard, IS) from mouse blood DBS cards using tert-butyl methyl ether. Chromatographic separation was achieved with 5 mm ammonium acetate (pH 6.5)-acetonitrile (35:65, v/v) at a flow rate of 0.60 mL/min on an Atlantis dC18 column with a total run time 3.0 min. The MS/MS ion transitions monitored were 428.80 → 254.70 for BCL and 269.00 → 169.60 for IS. Method validation was performed as per regulatory guidelines. A linear response function was observed from 0.92 to 1911 ng/mL for BCL in mouse blood. The intra- and inter-day precisions were in the ranges of 1.86-12.5 and 3.19-10.8%, respectively. This novel DBS method has been applied to a pharmacokinetic study in mice.

Photocatalytic degradation of textile dyeing wastewater through microwave synthesized Zr-AC, Ni-AC and Zn-AC

Abstract The novel zirconium oxide, nickel oxide and zinc oxide nanoparticles supported activated carbons (Zr-AC, Ni-AC, Zn-AC) were successfully fabricated through microwave irradiation method. The synthesized nanoparticles were characterized using XRD, HR-SEM, XPS and BET. The optical properties of Zr-AC, Ni-AC and Zn-AC composites were investigated using UV-Vis diffuse reflectance spectroscopy. The photocatalytic efficiency was verified in the degradation of textile dyeing wastewater (TDW) in UV light irradiation. The chemical oxygen demand (COD) of TDW was observed at regular intervals to calculate the removal rate of COD. Zn-AC composites showed impressive photocatalytic enrichment, which can be ascribed to the enhanced absorbance in the UV light region, the effective adsorptive capacity to dye molecules, the assisted charge transfer and the inhibited recombination of electron-hole pairs. The maximum TDW degradation (82% COD removal) was achieved with Zn-AC. A possible synergy mechanism on the surface of Zn-AC was also designed. Zn-AC could be reused five times without exceptional loss of its activity.

A concise review of the bioanalytical methods for the quantitation of sitagliptin, an important dipeptidyl peptidase-4 (DPP4) inhibitor, utilized for the characterization of the drug

Inhibition of dipeptidyl peptidase-4 (DPP4) is an emerging therapeutic approach for treating type 2 diabetes and has revolutionized the concept of diabetes management. Sitagliptin is the first approved orally active, potent, selective and nonpeptidomimetic DPP4 inhibitor. Incidence of hypoglycemia and weight gain is negligible with sitagliptin treatment. It is used as monotherapy or in combination with other anti-diabetic drugs to treat type 2 diabetes. There are numerous bioanalytical methods published for the analysis of sitagliptin in preclinical and clinical samples. This review focuses on the various HPLC and LC-MS/MS methods that have been used to analyze sitagliptin in various biological matrices. A small section is devoted to the bioanalysis of other DPP4 inhibitors such as vildagliptin, saxagliptin and linagliptin. This review provides key information in a concise manner regarding sample processing options, chromatographic/detection conditions and validation parameters of the chosen methods for sitagliptin and other DPP4 inhibitors.

Quantitation of VEGFR2 (vascular endothelial growth factor receptor) inhibitors – review of assay methodologies and perspectives

The introduction of small-molecule tyrosine kinase VEGFR2 (vascular endothelial growth factor receptor) inhibitors has added another dimension in the treatment of several oncology indications as they offer a unique mechanism. The VEGFR2 inhibitors have demonstrated superior benefits in treating certain types of cancer, such as renal cell carcinoma and hepatocellular carcinoma, as a monotherapy option. Many of the approved VEGFR2 inhibitors have also shown promise when used in combination with other anticancer agents. There are numerous bioanalytical methods published for the analysis of VEGFR2 inhibitors in preclinical and clinical samples. This review covers VEGFR2 inhibitors such as sunitinib, sorafenib, pazopanib and JI-101. In addition to providing a comprehensive review of the available methods for the above-mentioned VRGFR2 inhibitors, it also provides information on assays that can simultaneously measure multiple tyrosine kinase inhibitors, including VEGFR2 molecules. Based on the review, the published methodologies using LC/MS-MS or HPLC-UV are adequate for the quantification of the VEGFR2 inhibitors and can easily be established in a modern day bioanalytical laboratory. The availability of a plethora of assays for multiple tyrosine kinase inhibitors makes it easy to analyze a panel of compounds to support either therapeutic drug monitoring and/or clinical pharmacokinetics.

Sensitive LC-MS/MS Method for the Simultaneous Determination of Bendamustine and its Active Metabolite, γ-Hydroxybendamustine in Small Volume Mice and Dog Plasma and its Application to a Pharmacokinetic Study in Mice and Dogs

A highly sensitive, specific and rapid LC-ESI-MS/MS method has been developed and validated for the simultaneous quantification of bendamustine (BM) and γ-hydroxybendamustine (HBM) in small volume (20 µL) mice and dog plasma using phenacetin as an internal standard (IS) as per regulatory guidelines. Both the analytes and IS were extracted from mice and dog plasma using a liquid-liquid extraction method. Chromatography was achieved on Atlantis dC18 column using an isocratic mobile phase (0.2% formic acid:acetonitrile, 25:75) at a flow rate of 0.40 mL/min. The total chromatographic run time was 3.0 min and the elution of BM, HBM and IS occurred at ~1.2, 1.2 and 2.0 min, respectively. A linear response function was established 0.11-518 ng/mL for both the analytes in mice and dog plasma. The intra- and inter-day accuracy and precisions were in the range of 3.46-12.9 and 3.63-8.23%; 1.15-9.00 and 7.86-9.49% for BM and HBM, respectively in mice plasma and 2.15-6.49 and 1.73-13.1%; 4.35-13.9 and 4.33-10.5% for BM and HBM, respectively in dog plasma. This novel method has been applied to a pharmacokinetic study in mice and dogs.

Determination of ulixertinib in mice plasma by LC–MS/MS and its application to a pharmacokinetic study in mice

A sensitive, specific and rapid LC-ESI-MS/MS method has been developed and validated for the quantification of ulixertinib in mice plasma using phenacetin as an internal standard (I.S.) as per regulatory guidelines. Sample preparation was accomplished through a protein precipitation procedure with acetonitrile:methanol mixture. Chromatographic separation was performed on Atlantis dC18 column using a binary gradient using mobile phase A (0.2% formic acid in water) and B (acetonitrile) at a flow rate of 0.60mL/min. Elution of ulixertinib and I.S. occurred at ∼1.07 and 1.20min, respectively. The total chromatographic run time was 2.5min. A linear response function was established in the concentration range of 1.58-2054ng/mL. The intra- and inter-day accuracy and precisions were in the range of 2.11-11.8 and 5.80-11.4%, respectively. This novel method has been applied to a pharmacokinetic study in mice.

Infusion Rate Dependent Pharmacokinetics of Bendamustine with Altered Formation of γ-hydroxybendamustine (M3) Metabolite Following 30- and 60-min Infusion of Bendamustine in Rats

Bendamustine is an alkylating agent administered as 1 h intravenous infusion in the clinic for the treatment of malignant haematological cancers. The aim of the study was to evaluate the pharmacokinetics of bendamustine and its key cytochrome P 450 (CYP) 1A2 mediated γ-hydroxybendamustine (M3) metabolite after 30- and 60-min intravenous infusion of bendamustine in rats. 2 groups were assigned to receive bendamustine either as 30- or 60-min infusion and doses were normalized to 15 mg/kg for the sake of statistical evaluation. Serial pharmacokinetic samples were collected and were analysed for the circulatory levels of bendamustine and its M3 metabolite. Standard pharmacokinetic parameters were generated for bendamustine and its M3 metabolite. Regardless of the intravenous regimens, Cmax coincided with end of infusion for both bendamustine and its M3 metabolite. Immediately after stoppage of infusion, a rapid decline in the plasma levels occurred for both bendamustine and M3 metabolite. The Cmax and AUC0-∞ parameters for bendamustine after 60-min infusion were 1.90 and 1.34-fold higher; while CL was lower by 1.32-fold as compared to the 30-min infusion. In contrast, the Cmax and AUC0-∞ after 30-min infusion for the M3 metabolite was 2.15- and 2.78-fold greater; while CL was 2.32-fold lower when compared to the 60-min infusion. However, T1/2 and Vz values were similar between the 2 intravenous treatments for bendamustine or the M3 metabolite. The data unequivocally confirmed the existence of differential pharmacokinetics of bendamustine and its M3 metabolite as the function of the duration of intravenous infusion.