Monitoring of the thromboxane A2/prostacyclin ratio in the urine of patients with retinal vascular occlusion through the low-dose-aspirin therapy using the gas chromatography/selected ion monitoring method

Phase I Trial of Pyragrel, a Novel Thromboxane Synthetase Inhibitor, to Evaluate the Safety, Tolerability, and Pharmacokinetics in Healthy Volunteers

Background and Objective: Inhibition of thrombosis and platelet aggregation through a thromboxane synthetase inhibitor proved to be an effective and promising treatment for cardiovascular and/or cerebrovascular disease (CCVD) patients. This phase I study evaluated the safety, tolerability, and pharmacokinetics of sodium pyragrel, a novel thromboxane A₂ synthetase inhibitor, in healthy volunteers.

Methods: A total of 84 healthy Chinese volunteers were enrolled in the study and randomized into one of five dosing regimens of intravenous pyragrel, which were single ascending dose (30 to 300 mg), multiple doses (pyragrel 180 mg once daily on Day 1 and Day 6, twice daily from Day 2 to Day 5), 3×3 Latin square crossover (60, 120, 240 mg), and a continuous dose (360 mg in 24 h), respectively. Plasma concentrations were determined using HPLC-MS/MS. Pharmacokinetics parameters were calculated with non-compartment analysis.

Results: The maximum plasma concentrations of pyragrel were essentially reached at the end of the 3 h infusion. The pharmacokinetic process of pyragrel and two main metabolites (BBS and BJS) is linear over the 30–300 mg dose range, with no significant accumulation on multiple doses. The urinary excretion of pyragrel accounted for more than 70% of the total drug amount. Preliminary pharmacodynamic results demonstrated that the production of urinary 11-D-HTXB₂ was time- and dose-dependently inhibited by single i.v. dose of pyragrel.

Conclusions: Pyragrel was well tolerated after single ascending doses up to 300 mg, multiple doses of 180 mg, and continuous administration of 360 mg within 24 h. No drug-related, serious adverse drug reactions occurred during the five-part study. The most common pyragrel-related adverse events (AEs) were total bilirubin (TB)/direct bilirubin (DB) elevations with a relatively low incidence rate and seemed to be dose independent. Given the acceptable safety and appropriate pharmacokinetic properties of sodium pyragrel proven in this study, continued clinical development is warranted. The study was registered at http://www.chictr.org.cn (ChiCTR-IID-16010159).

Antiplatelet therapy: aspirin resistance and all that jazz!

Platelets play a crucial role in the pathogenesis of atherosclerosis, thrombosis, and stroke. Aspirin used alone or in combination with other antiplatelet drugs has been shown to offer significant benefit to patients at high risk of vascular events. Resistance to the action of aspirin may decrease this benefit. Aspirin resistance has been defined by clinical and/or laboratory criteria; however, detection by laboratory methods prior to experiencing a clinical event will likely provide the greatest opportunity for intervention. Numerous laboratory methods with different cutoff points have been used to evaluate the resistance. Noncompliance with aspirin treatment has also confounded studies. A single assay is currently insufficient to establish resistance. Combinations of results to confirm compliance and platelet inhibition may identify "at-risk" individuals who truly have aspirin resistance. The most effective strategy for managing patients with aspirin resistance is unknown; however, studies are currently underway to address this issue.

Mass spectrometry-based quantitative analysis and biomarker discovery

Mass spectrometry-based quantitative analysis and biomarker discovery using metabolomics approach represent one of the major platforms in clinical fields including for the prognosis or diagnosis, assessment of severity and response to therapy in a number of clinical disease states as well as therapeutic drug monitoring (TDM). This review first summarizes our mass spectrometry-based research strategy and some results on relationship between cysteinyl leukotriene (cysLT), thromboxane (TX), 12-hydroxyeicosatetraenoic acid (12-HETE) and other metabolites of arachidonic acid and diseases such as atopic dermatitis, rheumatoid arthritis and diabetes mellitus. For the purpose of evaluating the role of these metabolites of arachidonic acid in disease status, we have developed sensitive determination methods with simple solid-phase extraction and applied in clinical settings. In addition to these endogenous compounds, using mass spectrometry, we have developed actually applicable quantitative methods for TDM. Representative example was a method of TDM for sirolimus, one of the immunosuppressant agents for a recipient of organ transplant, which requires rigorous monitoring of blood level. As we recognized great potential in mass spectrometry during these researches, we have become interested in metabolomics as the non-targeted analysis of metabolites. Now, established strategy for the metabolomics investigation applies to samples from cells, animals and humans to separate groups based on altered patterns of metabolites in biological fluids and to identify metabolites as potential biomarkers discriminating groups. We would be honored if our research using mass spectrometry would contribute to provide useful information in the field of medical pharmacy.

Characterization of 11-dehydro-thromboxane B2 recombinant antibody obtained by phage display technology

Recombinant monoclonal antibodies specific for 11-dehydro-thromboxane B(2) (11D-TX) were isolated from the combinatorial libraries on a pComb3 phage-display vector using a magnetic cell sorting (MACS) system. The libraries were constructed from repertories of light and heavy-chains derived from the total RNA of 11D-TX conjugated keyhole limpet haemocyanin-immunized mice. Biotinylation of 11D-TX conjugated bovine serum albumin (BSA) was performed through free thiol groups on BSA using 1-biotinamido-4-[4'-(maleimidomethyl) cyclohexanecarboxamido] butane (Biotin-BMCC). Affinity bio-panning was performed to enrich the phage display libraries against biotinylated 11D-TX conjugated BSA with the MACS system. Results indicated that the selected anti-11D-TX Fab fragments expressed by E. coli exhibited a five-fold higher affinity for BSA conjugated 11D-TX compared to BSA alone and little specificity to other related compounds as determined by the binding assay and inhibition enzyme-linked immunosorbent assay (ELISA). This is the first report of an antibody against prostaglandin produced by phage display technology and also determination of the DNA sequence of this antibody. The MACS system was shown to be a simpler and more efficient method of panning than the conventional ELISA procedure. According to our results, we concluded that the phage display technique combined with the MACS system allowed the selection of the antibody with high affinity and some specificity.

Aspirin and urinary 11-dehydrothromboxane B(2) in African American stroke patients

BACKGROUND AND PURPOSE

The aim of the study was to evaluate the relationship between daily aspirin use and urinary excretion of a stable thromboxane metabolite, 11-dehydrothromboxane B(2) (11-DTB2), in African American stroke patients.

METHODS

Subjects were a subgroup of those screened for the African American Antiplatelet Stroke Prevention Study. Subjects were within 4 months of noncardioembolic ischemic stroke and were not being treated with anticoagulants. Antithrombotic therapy at the time of urine collection varied according to the practice patterns of various attending physicians who treated the patients during their acute strokes. 11-DTB2 was measured by enzyme immunoassay in random urine samples 1 to 4 months after the stroke.

RESULTS

Eighty-seven of 92 patients enrolled were able to give a urine sample at the time of enrollment. There were 51 men and 36 women aged 36 to 87 (mean 62) years. On the basis of antithrombotic treatment before the sample collection, we divided patients into 4 groups: (1) 16 patients treated with no aspirin (no antithrombotic drugs [n=4] or ticlopidine [n=12]), (2) 21 patients treated with 81 to 325 mg aspirin per day (81 mg/d [n=2], 325 mg/d [n=19]), (3) 20 patients treated with 650 mg aspirin per day, and (4) 30 patients treated with 975 to 1300 mg aspirin per day (975 mg/d [n=2] and 1300 mg/d [n=28]). In patients taking daily aspirin at any dose, the median urinary 11-DTB2 was 783 pg/mg creatinine compared with 1386 pg/mg creatinine in patients not taking daily aspirin (P=0.01 by Wilcoxon rank sum test). In multivariate regression analysis, aspirin use remained significantly associated with lower urinary 11-DTB2 (P=0.008). There was no dose-response effect between the 3 aspirin dose groups and urinary 11-DTB2 (P=0.70).

CONCLUSIONS

In African American stroke patients, aspirin use is associated with significantly lower urinary 11-DTB2 independent of other vascular factors, and there does not appear to be a dose-response effect for aspirin doses of 325 to 1300 mg daily. The clinical significance of these finding remains to be determined.

Relationship between thromboxane/prostacyclin ratio and diabetic vascular complications

To elucidate the relationship between the thromboxane A2/prostacyclin (TXA2/PGI2) ratio and diabetic complications, the levels of 11-dehydro-thromboxane B2 and 2,3-dinor-6-keto-prostaglandin F1alpha, the urinary metabolites of thromboxane A2 and prostacyclin, were measured in diabetics by gas chromatography/selected ion monitoring. We compared the TXA2/PGI2 ratio in healthy volunteers and diabetics. The TXA2/PGI2 ratio of diabetics was significantly higher than that of healthy volunteers and we could reconfirm the hypercoagulable condition in diabetics. We also investigated the difference of TXA2/PGI2 levels in diabetics with retinopathy and neuropathy. The TXA2/PGI2 ratio of diabetics with retinopathy showed significantly higher level than without retinopathy. However, the TXA2/PGI2 ratio of diabetics with neuropathy was the same as without neuropathy. These results suggest that the TXA2/PGI2 ratio reflects the pathological conditions of diabetes, especially the change of vasculature. The monitoring and improvement of TXA2/PGI2 ratio could be useful for the prevention of diabetic vascular complications.