Hau C. Kwaan

Thrombotic Thrombocytopenic Purpura Associated with Ticlopidine: A Review of 60 Cases

Thrombotic thrombocytopenic purpura is a life-threatening multisystem disease characterized by thrombocytopenia, microangiopathic hemolytic anemia, neurologic changes, progressive renal failure, and fever [1, 2]. Its frequency is estimated to be only 3.7 cases per year per 1 million persons, with mortality rates ranging from 10% to 20% [3-5]. Although the cause of thrombotic thrombocytopenic purpura is unknown, many drugs, including penicillin, antineoplastic chemotherapy agents, and oral contraceptives, have been associated with the syndrome [6]. Ticlopidine, an antiplatelet agent, has rarely been associated with thrombotic thrombocytopenic purpura [6-14]. From the time when ticlopidine was first marketed (in October 1991) through March 1995, the U.S. Food and Drug Administration received reports of 25 ticlopidine users who developed thrombotic thrombocytopenic purpura [7]. Ticlopidine is used for treatment of intermittent claudication; for prevention of thrombotic strokes; and, more recently, for patients with cardiac stents. Early clinical trials identified neutropenia with bone marrow aplasia as the most common serious side effect of ticlopidine (with an incidence of 2.4% in clinical trials), but instances of ticlopidine-associated thrombotic thrombocytopenic purpura have been infrequently described [8-14]. We describe clinical characteristics, time course until the onset of disease, response to treatment, and outcomes in 60 patients with ticlopidine-associated thrombotic thrombocytopenic purpura. Methods Cases of ticlopidine-associated thrombotic thrombocytopenic purpura were identified from five sources: 1) reports obtained from MedWatch, the U.S. Food and Drug Administrations spontaneous reporting system [n = 36]; 2) previously published case reports (n = 11) [8-14]; 3) case summaries given to us after an informal survey of 20 hematologists on ticlopidine-associated thrombotic thrombocytopenic purpura [n = 6]; 4) cases reported to us from physicians affiliated with a large therapeutic plasmapheresis program (HemaCare, Inc., Sherman Oaks, California [n = 4]); and 5) medical records of patients with thrombotic thrombocytopenic purpura who were seen by physicians at Northwestern Memorial Hospital, Chicago, Illinois (n = 3). The case definition for ticlopidine-associated thrombotic thrombocytopenic purpura included use of ticlopidine and development of thrombotic thrombocytopenic purpura as measured by the scoring system proposed by Rose and Eldor [5]. The scoring system comprises four categories: platelet count (x109/L), hemoglobin level (g/L), serum creatinine level (micromol/L), and neurologic changes. Each category is assigned a score of 0, 1, or 2 on the basis of set criteria; a total combined category score of 4 or more indicates a diagnosis of thrombotic thrombocytopenic purpura. Data Synthesis We identified 60 cases of ticlopidine-associated thrombotic thrombocytopenic purpura (Table 1). Almost two thirds of the patients were older than 60 years of age, half were male, and 72% had received ticlopidine for stroke prevention. Normal platelet counts within 2 weeks of onset of thrombotic thrombocytopenic purpura were documented in two thirds of patients for whom platelet counts before disease onset were available. Ticlopidine therapy was stopped in all patients upon diagnosis of thrombotic thrombocytopenic purpura. The most common concomitant medications were aspirin (22%), metoprolol (12%), diltiazem (15%), hydrochlorothiazide (7%), and nitroglycerin (7%). In almost all cases, ticlopidine was the only new drug prescribed in the month preceding the onset of thrombotic thrombocytopenic purpura. Ticlopidine had been prescribed for less than 2 weeks for 15% of patients and less than 1 month for 80% of patients. Table 1. Clinical Characteristics and Treatment of 60 Patients with Ticlopidine-Associated Thrombotic Thrombocytopenic Purpura In all patients, thrombotic thrombocytopenic purpura was manifested by thrombocytopenia, anemia, neurologic changes, or renal dysfunction: Platelet counts were less than 20 109/L in two thirds of patients; hemoglobin levels were less than 90 g/L in 28% of patients; neurologic changes, including focal deficits, convulsions, or coma, were seen in 75% of patients; and renal insufficiency with a serum creatinine level greater than 221 mol/L was seen in 25% of patients. Plasmapheresis was performed in 63% of patients; the rate was significantly higher among patients who were younger than 60 years of age (81% for persons <60 years of age and 54% for persons 60 years of age; P = 0.028). Overall, the survival rate for patients with thrombotic thrombocytopenic purpura was 67%. Although no patient has had relapse, none have been rechallenged with ticlopidine. Plasmapheresis was the most important predictor of death: The mortality rate was 24% among patients who underwent plasmapheresis and 50% among patients who did not undergo this procedure (P = 0.049). Discussion We described the clinical characteristics of 60 patients with ticlopidine-associated thrombotic thrombocytopenic purpura. This condition is severe: Among patients in our study, the mortality rate was 33%. The disease affected both men and women and occurred among older persons who had frequently received the drug for prevention of stroke and among younger patients who usually had received the drug after cardiac stent placement. The individual case histories of patients in our study are similar to the few cases of ticlopidine-associated thrombotic thrombocytopenic purpura cases described elsewhere [8-14]. The clinical presentation of thrombocytopenia, anemia, neurologic changes, renal dysfunction, responsiveness to treatment, and overall mortality for ticlopidine-associated thrombotic thrombocytopenic purpura that we found are similar overall to those for patients with thrombotic thrombocytopenic purpura in general [3-5]. Undergoing plasma exchange is important for patients with thrombotic thrombocytopenic purpura. In a randomized trial, Rock and colleagues [3] reported a mortality rate of 22% among persons who underwent plasma exchange compared with a mortality rate of 83% among patients who underwent plasma infusion [3]. Similarly, we found a mortality rate of 24% among patients who underwent plasma exchange compared with a mortality rate of 50% among patients who did not undergo this procedure. Our description of cases of ticlopidine-associated thrombotic thrombocytopenic purpura is limited because we used a clinical definition of the syndrome. Most of our patients had a score of 4 or more according to the scoring system of Rose and Eldor; four patients had a score of 3 and a diagnosis of thrombotic thrombocytopenic purpura made by an attending hematologist [5]. Patients were not directly seen by us, and patient information was provided by case reports (rather than hospital records) that often did not include complete records of laboratory values and clinical findings. These factors prevented us from obtaining complete clinical information on all patients. The mechanism by which ticlopidine induces the clinical manifestations of thrombotic thrombocytopenic purpura is unclear. Ticlopidine, a thienopyridine compound, alters platelet function by inhibiting the binding of adenosine 5 diphosphate to its adenylyl cyclase-coupled receptor site [15, 16]. The drug decreases clottable fibrinogen but not fibrinogen antigen [17] and decreases fibronectin [18]. A metabolite of ticlopidine rather than the parent compound is thought to be responsible for these actions [19]. It is paradoxical that a drug that inhibits platelet function is incriminated in a disorder that is manifested by platelet thrombi. This suggests that in patients who develop thrombotic thrombocytopenic purpura, a metabolite of ticlopidine with an activity very different from that of the parent compound may produce this disorder. Most physicians are aware that neutropenia, hepatic cholestasis, and thrombocytopenia are adverse effects of ticlopidine [6, 20]. One review of an estimated 10 million patient-years of ticlopidine treatment [7] identified 645 cases of aplastic anemia, bone marrow suppression, pancytopenia, and agranulocytosis, of which 102 (16%) were coded as fatal. Because hematologic side effects of ticlopidine almost always occur within the first 3 months of therapy, the U.S. Food and Drug Administration issued advisory warnings when ticlopidine was approved, advising physicians to perform complete blood counts every 2 weeks for 12 weeks. However, compliance with this recommendation is unlikely to assist in early detection of thrombotic thrombocytopenic purpura. For most patients in our study, platelet counts were within normal limits 2 weeks before the onset of thrombotic thrombocytopenic purpura. Our study raises concern about the potential for underdiagnosis and subsequent undertreatment of ticlopidine-associated thrombotic thrombocytopenic purpura. After cardiac stent placement or after saphenous vein grafting for treatment of peripheral vascular disease, patients usually receive ticlopidine for 2 to 4 weeks. Given this short period, many cardiologists do not monitor complete blood counts; consequently, thrombocytopenia associated with thrombotic thrombocytopenic purpura may go unrecognized. In our study, 12 patients developed thrombotic thrombocytopenic purpura after receiving ticlopidine for 3 weeks or less after placement of cardiac stents; 3 of these patients died. For older patients who receive ticlopidine to prevent stroke, the onset of thrombotic thrombocytopenic purpura may be insidious, with symptoms of altered neurologic function that mimic a stroke. Physicians may attribute these changes to cerebrovascular disease and may not institute plasmapheresis in a timely manner. In our study, only 60% of patients with thrombotic thrombocytopenic purpura who received ticlopidine for stroke prevention were treated with plasmapheresis. In some patie

Effect of warfarin anticoagulation on survival in carcinoma of the lung, colon, head and neck, and prostate: Final Report of VA cooperative study # 75

VA Cooperative Study #75 was established to test in a controlled, randomized trial the hypothesis that warfarin anticoagulation would favorably affect the course of certain types of malignancy. No differences in survival were observed between warfarin‐treated and control groups for advanced non‐small cell lung, colorectal, head and neck and prostate cancers. However, warfarin therapy was associated with a significant prolongation in the time to first evidence of disease progression (P = 0.016) and a significant improvement in survival (P = 0.018) for patients with small cell carcinoma of the lung, including the subgroup of patients with disseminated disease at the time of randomization (P = 0.013). A trend toward improved survival with warfarin treatment was observed for the few patients admitted to this study with non‐small cell lung cancer who had minimal disease at randomization. These results suggest that warfarin, as a single anticoagulant agent, may favorably modify the course of some, but not all, types of human malignancy, among which is small cell carcinoma of the lung. Further trials of warfarin may be indicated in patients with limited disease who have cell types that failed to respond when advanced disease was present.

The plasminogen-plasmin system in malignancy

SummaryThe study of the plasminogen-plasmin system has, in the past, contributed much to the understanding of fibrinolysis and thrombolysis. Attention is now focused on the role of the components of this system in many biologic functions. Findings of uPA, its receptor and its inhibitor in many tumor tissues and tumor cell lines, strongly implicate their involvement in tumor invasion, tumor cell proliferation and metastasis. The characteristics of the plasminogen activators, the uPA receptor and the plasminogen activator inhibitors as well as their expression and regulation in tumors and tumor cell lines are reviewed.

Expression of plasminogen activator inhibitor type 1 by human prostate carcinoma cells inhibits primary tumor growth, tumor-associated angiogenesis, and metastasis to lung and liver in an athymic mouse model.

Expression of urokinase-type plasminogen activator (uPA) by malignant cells correlates with an aggressive phenotype, including increased invasiveness, tumor-associated angiogenesis, and metastases. Plasminogen activator inhibitor type 1 (PAI-1) is undetectable in cells of some aggressive malignancies, but present in the stroma of tumor-associated microvasculature. This analysis of an athymic mouse model of prostate carcinoma further defines the role of the uPA/PAI-1/plasmin system in primary growth and metastasis. A marked increase in PAI-1 expression was induced in clones of the aggressive human prostate carcinoma line, PC-3, by stable transfection. Primary PC-3 tumors, in mice, were significantly smaller when derived from PAI-1 expressing versus control cells. PAI-1 expression reduced the density of tumor-associated microvasculature by 22-38%. Microscopic metastases were quantitated using stable expression of the chromogenic label (beta-galactosidase) in control and PAI-1 expressing cells. PAI-1 expression resulted in a significant inhibition of lung metastases, and liver metastases. Expression of PAI-1 by malignant prostate cells resulted in a less aggressive phenotype, presumably by inhibition of uPA activity, suggesting pharmacologic or molecular inhibition of uPA activity as a potential therapeutic target.

The Plasminogen Activator System and Cancer

The fibrinolytic system, more appropriately referred to as the plasminogen activator system, controls not only the intravascular fibrin deposition but also participates in a wide variety of physiologic and pathologic processes. In cancer, the components of this system are involved in tumor growth, invasion and metastasis, through their effect on angiogenesis and cell migration. These components are found in most tumors and their expression signifies not only their function but also carries a prognostic value. Their expression is in turn modulated by cytokines and growth factors, many of which are up-regulated in cancer. Though both plasminogen activators, tPA and uPA, are expressed in tumor cells, uPA with its receptor (uPAR) is mostly involved in cellular functions, while tPA with its receptor annexin II on endothelial surface regulates intravascular fibrin deposition. Among the inhibitors of fibrinolysis, PAI-1 is a major player in the pathogenesis of many vascular diseases as well as in cancer. Therapeutic intervention, either using plasminogen activators or use of experimental inhibitor agents against PAI-1, has shown encouraging results in experimental tumors but not verified clinically. Information provided in this brief review is aimed to promote greater interest in the role of the plasminogen activator system in cancer.

A peptide derived from the nonreceptor binding region of urokinase plasminogen activator (uPA) inhibits tumor progression and angiogenesis and induces tumor cell death in vivo

Urokinase plasminogen activator (uPA) plays an important role in the progression of several malignancies including breast cancer. We have identified a noncompetitive antagonist of the uPA‐uPAR interaction derived from a nonreceptor binding region of uPA (amino acids 136‐143). This 8‐mer capped peptide (Å6) inhibited breast cancer cell invasion and endothelial cell migration in a dose‐dependent manner in vitro without altering cell doubling time. Intraperitoneal administration of Å6 resulted in a significant inhibition of tumor growth and suppressed the development of lymph node metastases in several models of breast cancer cell growth and metastasis. Large areas of tumor necrosis and extensive positive staining by TUNEL were observed on histological and immunohistochemical analysis of experimental tumor sections from Å6‐treated animals. Å6 treatment also resulted in a decrease in factor VIII‐positive tumor microvessel hot‐spots. These results identify a new epitope in uPA that is involved in the uPA‐uPAR interaction and indicate that an antagonist based on this epitope is able to inhibit tumor progression by modulating the tumor microenvironment in the absence of direct cytotoxic effects in vivo.—Guo, Y., Higazi, A. A., Arakelian, A., Sachais, B. S., Cines, D., Goldfarb, R. H., Jones, T. R., Kwaan, H., Mazar, A. P., Rabbani, S. A. A peptide derived from the nonreceptor binding region of urokinase plasminogen activator (uPA) inhibits tumor progression and angiogenesis and induces tumor cell death in vivo. FASEB J. 14, 1400–1410 (2000)

Plasminogen activator inhibitor 1 may promote tumour growth through inhibition of apoptosis

Plasminogen activator inhibitor 1 (PAI-1) has been found to be a bad prognostic factor in a number of tumours but the reason has not been fully explained. The human prostate cancer cell line PC-3 and the human promyelocytic leukaemia cell line HL-60 were used in this study to determine the effect of PAI-1 on spontaneous and induced apoptosis in culture. Apoptosis was induced with camptothecin or etoposide. Addition of a stable variant of PAI-1 or wild-type PAI-1 to these cells resulted in a significant inhibition of apoptosis. In contrast, both the latent form of PAI-1 and the stable variant of PAI-1 inactivated by a specific neutralizing monoclonal antibody, or the stable variant of PAI-1 in a complex with recombinant urokinase did not inhibit apoptosis. This indicated that the inhibitory activity of PAI-1 was required for its anti-apoptotic effect but the urokinase-type plasminogen activator receptor was not involved. These findings provide an explanation for the bad prognostic correlation of high PAI-1 levels in tumours. The anti-apoptotic effect was also found in non-tumoural cells including human umbilical vein endothelial cells and the benign human breast epithelial cell line MCF-10A, suggesting that this is a novel physiologic function of PAI-1.

Clopidogrel-Associated TTP: An Update of Pharmacovigilance Efforts Conducted by Independent Researchers, Pharmaceutical Suppliers, and the Food and Drug Administration

Background and Purpose— Since the 1999 identification of clopidogrel-associated thrombotic thrombocytopenic purpura (TTP) through independent active surveillance, subsequent cases have been identified by pharmaceutical suppliers of clopidogrel and the Food and Drug Administration (FDA). For cases of clopidogrel-associated TTP reported between 1998 to 2002, we evaluated the quality and timeliness of data from 3 reporting systems-independent active surveillance (n=13), pharmaceutical suppliers (n=24), and the FDA (n=13)—and identified prognostic factors associated with mortality. Methods— This study assessed the completeness of information on TTP diagnosis, treatment response, and causality from the 3 reporting systems. In addition, predictors of mortality were identified through classification tree analysis. Results— Completeness, timeliness, and certainty of diagnosis were best for cases obtained by active surveillance, intermediate for cases reported to the pharmaceutical supplier, and poorest for cases reported directly to the FDA. Clopidogrel had been used for ≤2 weeks by 65%. The survival rate for patients with clopidogrel-associated TTP was 71.2%. Receipt of therapeutic plasma exchange within 3 days of onset of TTP increased the likelihood of survival (100% versus 27.3%, P <0.001). Conclusions— Compared with reports submitted by suppliers or the FDA, reports obtained through active surveillance provided timelier and more complete information. Clopidogrel-associated TTP often occurs within 2 weeks of drug initiation, occasionally relapses, and has a high mortality if not treated promptly.

Effects of all‐trans retinoic acid or chemotherapy on the molecular regulation of systemic blood coagulation and fibrinolysis in patients with acute promyelocytic leukemia

Summary.  We studied the pathogenesis of the bleeding disorder in acute promyelocytic leukemia by measuring procoagulant, profibrinolytic, and proinflammatory mediators in peripheral blood and bone marrow cells from 25 previously untreated patients. Patients were induced with either all‐trans retinoic acid (ATRA) or chemotherapy. Plasma levels of fibrinopeptide A (FPA), fibrin d‐dimer, thrombin antithrombin (TAT) complex, prothrombin fragment 1.2 (F1.2), urokinase‐type plasminogen activator (uPA), tissue‐type plasminogen activator (t‐PA) and plasminogen activator‐inhibitor 1 (PAI‐1) were measured before and after therapy, as was the cellular expression of the genes for tissue factor (TF) and interleukin‐1β (IL‐1β). The mean plasma levels of fibrin d‐dimer, F1.2, TAT and FPA were markedly elevated prior to therapy and declined during the first 30 days of treatment with either ATRA or chemotherapy, but more rapidly and to a greater extent in patients treated with ATRA. ATRA treatment was associated with a significant decrease in TF gene expression in bone marrow cells during the first 30 days of treatment, whereas IL‐1β gene expression, which decreased in the cells of six patients treated with either chemotherapy or ATRA, actually increased in the remaining six patients treated with either chemotherapy or ATRA. In patients with APL, treatment with either chemotherapy or ATRA rapidly ameliorates the coagulopathy, as indicated by an abrupt decline in markers of clotting activation. An increase in cytokine gene expression (e.g. IL‐1β) may provide an explanation for the persistent hypercoagulability observed in some patients with APL, regardless of therapeutic approach. Our data confirms and extends earlier observations by others that ATRA is more effective than chemotherapy alone in rapidly reducing the procoagulant burden of APL tumor cells. However, our data also suggests that cytokine expression in some patients may be accelerated by either chemotherapy or ATRA. The implications of this observation for understanding the retinoic acid syndrome will require further studies.

Plasminogen activator activity in cultures from human tissues. An immunological and histochemical study

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.