Evaluation of inhibitors of the arachidonic acid cascade with intact platelets using an on-line dilution and on-line solid phase extraction HPLC-MS method

Development and validation of a quantification method for direct oral anticoagulants from capillary blood using volumetric absorptive microsampling and online SPE-LC-MS

The number of prescriptions for new direct oral anticoagulants (DOACs) apixaban, edoxaban, rivaroxaban and dabigatran has increased exponentially in recent years, increasingly replacing the old gold standard, vitamin-K-antagonists. Due to their wide therapeutic range, therapeutic drug monitoring (TDM) is not required, although it has been proven that this could significantly reduce side effects. In order to develop a cost-efficient and simple method for the simultaneous detection of the DOACs and phenprocoumon, a new technology for sample preparation from capillary blood in the ambulant sector named VAMS® was integrated and an LC-MS detector with on-line solid phase extraction (SPE) applying a Turboflow HTLC CycloneTM 1.0x50 mm column was used. The mobile phase consisted of methanol with water (3/97 v/v) and 0.1 % ammonia solution with a flow rate of 2.5 mL/min. For the chromatographic separation, a Phenomenex LTD Kinetex 2.6 µm C18 100 Å, 100x3.0 mm column with a flow rate of 0.3 mL/min in gradient mode was utilized. The mobile phase consisted of acetonitrile, water and formic acid (A: 10:90:0.1 v/v and B: 95:05:0.1 v/v). The method was fully validated in the therapeutic range of the substances according to current guidelines. The LLOQ ranged from 3.5 µg/L for rivaroxaban to 88 µg/L for phenprocoumon and the intra-day and inter-day precision was less than 13 % and 12 %, while the accuracy was within a range of 85.7-113 % and 88.7-106 %, respectively. Samples could be stored in the Mitra® devices for at least seven days at room temperature except of dabigatran. Because the Mitras® were used, exactly 10 µL of blood could be drawn and no significant haematocrit effect was observed. A reliable, simple and cost-effective extraction and analysis LC-MS method could be developed and validated. This method is therefore applicable in ambulatory care.

Development and validation of a bioanalytical method for the quantification of methotrexate from serum and capillary blood using volumetric absorptive microsampling (VAMS) and on-line solid phase extraction (SPE) LC-MS

High-dose methotrexate is part of the polychemotherapy protocols for the treatment of Acute lymphoblastic leukaemia (ALL) with therapeutic drug monitoring (TDM) to adjust leucovorin rescue. An immunoassay is commonly used to analyse serum samples collected via venous blood sampling. However, immunoassays cannot distinguish between the parent drug and its metabolites. Besides, the blood volume required by venous blood sampling is high. Therefore, the aim of this project was to develop a fast, simple, reliable and cost-efficient micro sampling bioanalytical method using capillary blood to minimize the harm of children and to analyse both methotrexate and its metabolites. To achieve this aim, a LC-MS method with on-line solid phase extraction (SPE) for the simultaneous detection of methotrexate and its metabolites from capillary blood using volumetric-absorptive-microsampling (VAMS) technology was developed and fully validated. Besides, the method was also validated and modified for serum samples to compare the results with the immunoassay. A single-quadrupole MS detector was used for detection. Through the use of on-line SPE technology, a lower limit of quantitation of 0.03 µM for MTX and 7-OH-MTX and of 0.05 µM for DAMPA from a 10 μL capillary blood sample was achieved. The accuracy is between 90.0 and 104% and the precision between 4.7 and 12% for methotrexate and its metabolites, respectively. Because of the cross reactivity of the immunoassay a cross-validation was not successful. Besides, a correlation factor of 0.46 for MTX between plasma and whole-blood was found. A fast, simple, reliable and cost-efficient extraction and analysis LC-MS method could be developed and validated, which is applicable in ambulatory and clinical care.

N,N-Disubstituted 4-Sulfamoylbenzoic Acid Derivatives as Inhibitors of Cytosolic Phospholipase A2α: Synthesis, Aqueous Solubility, and Activity in a Vesicle and a Whole Blood Assay

BACKGROUND

Cytosolic phospholipase A2α (cPLA2α) is the key enzyme that initiates the arachidonic acid cascade through which pro-inflammatory lipid mediators can be formed. Therefore, cPLA2α is considered an interesting target for the development of anti-inflammatory drugs. Although several effective inhibitors of the enzyme have been developed, none of them has yet reached clinical application.

OBJECTIVE

Recently, we have prepared new 4-sulfamoylbenzoic acid derivatives based on a cPLA2α inhibitor found in a ligand-based virtual screening. The most effective of these compounds were now subjected to further variations in which the substitution pattern on the sulfamoyl nitrogen atom was changed..

METHODS

The new compounds were tested in vitro in a vesicle assay for cPLA2α inhibition as well as for their water solubility, metabolic stability, and selectivity towards related enzymes. In addition, they were evaluated ex vivo in a whole blood assay in which metabolites of the arachidonic acid cascade formed after activation of cPLA2α were quantified using a combined online dilution/ online solid phase extraction HPLC-MS method.

RESULTS

Inhibitors with submicromolar inhibitory in vitro potency were found with favourable water solubility and selectivity. However, their efficacy did not match that of the highly effective, known, structurally related cPLA2α inhibitor giripladib, which was also tested as a reference. One advantage of some of the new compounds compared to giripladib was their significantly improved water solubility. When analyzing the substances in the ex vivo whole blood assay, it was found that the obtained inhibition data correlated better with the in vivo results when the phorbol ester 12-Otetradecanoylphorbol- 13-acetate was used for activation of the enzyme in the blood cells instead of the calcium ionophore A23187.

CONCLUSION

New compounds with good activity towards cPLA2α and reasonable physicochemical properties were identified. Overall, the results obtained could be helpful in the development of clinically applicable inhibitors of this enzyme.

Development and validation of a bioanalytical method for the quantification of axitinib from plasma and capillary blood using volumetric absorptive microsampling (VAMS) and on-line solid phase extraction (SPE) LC-MS

For therapeutic drug monitoring (TDM) of axitinib, the new volumetric absorption microsampling technology (VAMS™) was applied to obtain capillary blood samples in an ambulatory setting and the results were compared to plasma samples as the gold standard. On-line solid phase extraction (SPE) applying a Turboflow HTLC Cyclone™ 1.0 × 500 mm column was used to reduce costs and working time. For the analytical separation, a Kinetex 2.6 µm C18 100 Å, 100 × 3.0 mm column with a flow rate of 0.3 mL/min in gradient mode was utilised. The mobile phase consisted of acetonitrile, water and formic acid (A: 05:95:0.1 v/v and B: 95:05:0.1 v/v). For the detection, a single-quadrupole MS detector was used. Through the use of on-line SPE technology, it is possible to reach a LLOQ of 0.5 µg/L from a 10 µL capillary blood sample. For lower concentrations, a MS/MS-detector coupled with the same chromatographic system was applied reaching a LLOQ of 0.04 µg/L. This newly developed method was validated with both detectors at different calibration ranges for plasma and capillary blood as matrix. The precision of the within- and between-runs was within a range of 0.6-7.8% and 1.8 - 14% CV, respectively, while the accuracy was within a range of 81.2-115% and 87.7-116%, respectively. A reliable, simple, less personnel-intensive and cost-efficient extraction and analysis LC-MS and LC-MS/MS method could be developed and validated, which is applicable in ambulatory and clinical care.