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author:("kwan, Hau C.")
1.  Ticlopidine-, Clopidogrel-, and Prasugrel-Associated Thrombotic Thrombocytopenic Purpura: A 20-Year Review from the Southern Network on Adverse Reactions (SONAR) 
Thienopyridine-derivatives (ticlopidine, clopidogrel, and prasugrel) are the primary antiplatelet agents. Thrombotic thrombocytopenic purpura (TTP) is a rare drug-associated syndrome, with the thienopyridines being the most common drugs implicated in this syndrome. We reviewed 20 years of information on clinical, epidemiologic, and laboratory findings for thienopyridine-associated TTP. Four, 11, and 11 cases of thienopyridine-associated TTP were reported in the first year of marketing of ticlopidine (1989), clopidogrel (1998), and prasugrel (2010), respectively. As of 2011, the FDA received reports of 97 ticlopidine-, 197 clopidogrel-, and 14 prasugrel-associated TTP cases. Severe deficiency of ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) was present in 80% and antibodies to 100% of these TTP patients on ticlopidine, 0% of the patients with clopidogrel-associated TTP (p < 0.05), and an unknown percentage of patients with prasugrel-associated TTP. TTP is associated with use of each of the three thienopyridines, although the mechanistic pathways may differ.
doi:10.1055/s-0032-1328894
PMCID: PMC3804561  PMID: 23111862
thrombotic thrombocytopenic purpura; ticlopidine; clopidogrel; prasugrel; adverse event
3.  Ticlopidine- and clopidogrel-associated thrombotic thrombocytopenic purpura (TTP): review of clinical, laboratory, epidemiological, and pharmacovigilance findings (1989–2008) 
Thrombotic thrombocytopenic purpura (TTP) is a fulminant disease characterized by platelet aggregates, thrombocytopenia, renal insufficiency, neurologic changes, and mechanical injury to erythrocytes. Most idiopathic cases of TTP are characterized by a deficiency of ADAMTS13 (a disintegrin and metalloprotease, with thrombospondin-1-like domains) metalloprotease activity. Ironically, use of anti-platelet agents, the thienopyridine derivates clopidogrel and ticlopidine, is associated with drug induced TTP. Data were abstracted from a systematic review of English-language literature for thienopyridine-associated TTP identified in MEDLINE, EMBASE, the public website of the Food and Drug Administration, and abstracts from national scientific conferences from 1991 to April 2008. Ticlopidine and clopidogrel are the two most common drugs associated with TTP in FDA safety databases. Epidemiological studies identify recent initiation of anti-platelet agents as the most common risk factor associated with risks of developing TTP. Laboratory studies indicate that most cases of thienopyridine-associated TTP involve an antibody to ADAMTS13 metalloprotease, present with severe thrombocytopenia, and respond to therapeutic plasma exchange (TPE); a minority of thienopyridine-associated TTP presents with severe renal insufficiency, involves direct endothelial cell damage, and is less responsive to TPE. The evaluation of this potentially fatal drug toxicity can serve as a template for future efforts to comprehensively characterize other severe adverse drug reactions.
doi:10.1038/ki.2008.613
PMCID: PMC3500614  PMID: 19180126
drug-associated TTP; epidemiology; ADAMTS13
4.  Two Mechanistic Pathways for Thienopyridine-Associated Thrombotic Thrombocytopenic Purpura 
Objectives
We sought to describe clinical and laboratory findings for a large cohort of patients with thienopyridine-associated thrombotic thrombocytopenic purpura (TTP).
Background
The thienopyridine derivatives, ticlopidine and clopidogrel, are the 2 most common drugs associated with TTP in databases maintained by the U.S. Food and Drug Administration (FDA).
Methods
Clinical reports of TTP associated with clopidogrel and ticlopidine were identified from medical records, published case reports, and FDA case reports (n = 128). Duration of thienopyridine exposure, clinical and laboratory findings, and survival were recorded. ADAMTS13 activity (n = 39) and inhibitor (n = 30) were measured for a subset of individuals.
Results
Compared with clopidogrel-associated TTP cases (n = 35), ticlopidine-associated TTP cases (n = 93) were more likely to have received more than 2 weeks of drug (90% vs. 26%), to be severely thrombocytopenic (84% vs. 60%), and to have normal renal function (72% vs. 45%) (p < 0.01 for each). Compared with TTP patients with ADAMTS13 activity >15% (n = 13), TTP patients with severely deficient ADAMTS13 activity (n = 26) were more likely to have received ticlopidine (92.3% vs. 46.2%, p < 0.003). Among patients who developed TTP >2 weeks after thienopyridine, therapeutic plasma exchange (TPE) increased likelihood of survival (84% vs. 38%, p < 0.05). Among patients who developed TTP within 2 weeks of starting thienopyridines, survival was 77% with TPE and 78% without.
Conclusions
Thrombotic thrombocytopenic purpura is a rare complication of thienopyridine treatment. This drug toxicity appears to occur by 2 different mechanistic pathways, characterized primarily by time of onset before versus after 2 weeks of thienopyridine administration. If TTP occurs after 2 weeks of ticlopidine or clopidogrel therapy, therapeutic plasma exchange must be promptly instituted to enhance likelihood of survival.
doi:10.1016/j.jacc.2007.04.093
PMCID: PMC3167088  PMID: 17868804
5.  Particulate Matter-Induced Lung Inflammation Increases Systemic Levels of PAI-1 and Activates Coagulation Through Distinct Mechanisms 
PLoS ONE  2011;6(4):e18525.
Background
Exposure of human populations to ambient particulate matter (PM) air pollution significantly contributes to the mortality attributable to ischemic cardiovascular events. We reported that mice treated with intratracheally instilled PM develop a prothrombotic state that requires the release of IL-6 by alveolar macrophages. We sought to determine whether exposure of mice to PM increases the levels of PAI-1, a major regulator of thrombolysis, via a similar or distinct mechanism.
Methods and Principal Findings
Adult, male C57BL/6 and IL-6 knock out (IL-6−/−) mice were exposed to either concentrated ambient PM less than 2.5 µm (CAPs) or filtered air 8 hours daily for 3 days or were exposed to either urban particulate matter or PBS via intratracheal instillation and examined 24 hours later. Exposure to CAPs or urban PM resulted in the IL-6 dependent activation of coagulation in the lung and systemically. PAI-1 mRNA and protein levels were higher in the lung and adipose tissue of mice treated with CAPs or PM compared with filtered air or PBS controls. The increase in PAI-1 was similar in wild-type and IL-6−/− mice but was absent in mice treated with etanercept, a TNF-α inhibitor. Treatment with etanercept did not prevent the PM-induced tendency toward thrombus formation.
Conclusions
Mice exposed to inhaled PM exhibited a TNF-α-dependent increase in PAI-1 and an IL-6-dependent activation of coagulation. These results suggest that multiple mechanisms link PM-induced lung inflammation with the development of a prothrombotic state.
doi:10.1371/journal.pone.0018525
PMCID: PMC3073968  PMID: 21494547
6.  Plasminogen activator activity in cultures from human tissues. An immunological and histochemical study 
Journal of Clinical Investigation  1969;48(9):1740-1753.
Human tissues and cells from pre- and postnatal life were cultivated and studied for plasminogen activator activity. Cultures were obtained from kidney, renal blood vessels, ureter, bladder, lung, and heart. Local activator activity of cells was demonstrated by histochemical techniques. Activator released by cells into the supernatant culture media was assayed by fibrin plate techniques and was investigated for immunological identity using specific antisera to an activator of human origin, urokinase (UK).
Plasminogen activator was produced in primary cultures where cells retain specific functions and generally reflect the enzyme pattern of the tissues of origin. Cells from fetal and adult sources were found to yield activator antigenically identical to UK, as well as activator activity which differed from that of UK in immunoassays and which may represent tissue type activator. Such activity was released after injury or death of cells while UK was produced in cultures containing live, metabolizing cells.
Primary cultures of kidney confirmed that this organ is a rich source of UK and demonstrated, in addition, that UK is produced from the early stages of gestation and in increasing amounts thereafter. However, primary cultures also demonstrated that the ability to produce UK is not limited to the kidney but is a function of cells which are distributed widely in body tissues. Thus, activator antigenically identical to UK accumulated progressively after many refeedings in culture supernates of fetal lung and ureter, as well as in supernates of renal blood vessels of adults. These findings indicate continuous formation of UK by the cultured cells and, furthermore, provide evidence of UK production in blood vessels. In cultures from other tissues, particularly those from fetal heart and adult lung and bladder, investigation of activator was hindered by inhibitory activity which accumulated in the supernates. Such activity was derived from cells in culture and was directed selectively against UK, indicating that inhibitor as well as UK are produced by cells of various organs of the body.
Plasminogen activator also was produced by serially propagated cells, diploid and heteroploid. However, only diploid cell lines retained activator activity of the original tissues and continued to produce activator antigenically identical to UK. In contrast, heteroploid line appeared to have lost the ability to form UK by yielded activator activity that differed from that of UK in immunoassays. Serially propagated cells thus provide an additional tool for in vitro study of plasminogen activator and may facilitate investigation of the fibrinolytic system in man.
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PMCID: PMC535746  PMID: 5822582

Results 1-6 (6)