Don A. Gabriel

Lenalidomide after stem-cell transplantation for multiple myeloma

BACKGROUND Data are lacking on whether lenalidomide maintenance therapy prolongs the time to disease progression after autologous hematopoietic stem-cell transplantation in patients with multiple myeloma. METHODS Between April 2005 and July 2009, we randomly assigned 460 patients who were younger than 71 years of age and had stable disease or a marginal, partial, or complete response 100 days after undergoing stem-cell transplantation to lenalidomide or placebo, which was administered until disease progression. The starting dose of lenalidomide was 10 mg per day (range, 5 to 15). RESULTS The study-drug assignments were unblinded in 2009, when a planned interim analysis showed a significantly longer time to disease progression in the lenalidomide group. At unblinding, 20% of patients who received lenalidomide and 44% of patients who received placebo had progressive disease or had died (P<0.001); of the remaining 128 patients who received placebo and who did not have progressive disease, 86 crossed over to lenalidomide. At a median follow-up of 34 months, 86 of 231 patients who received lenalidomide (37%) and 132 of 229 patients who received placebo (58%) had disease progression or had died. The median time to progression was 46 months in the lenalidomide group and 27 months in the placebo group (P<0.001). A total of 35 patients who received lenalidomide (15%) and 53 patients who received placebo (23%) died (P=0.03). More grade 3 or 4 hematologic adverse events and grade 3 nonhematologic adverse events occurred in patients who received lenalidomide (P<0.001 for both comparisons). Second primary cancers occurred in 18 patients who received lenalidomide (8%) and 6 patients who received placebo (3%). CONCLUSIONS Lenalidomide maintenance therapy, initiated at day 100 after hematopoietic stem-cell transplantation, was associated with more toxicity and second cancers but a significantly longer time to disease progression and significantly improved overall survival among patients with myeloma. (Funded by the National Cancer Institute; ClinicalTrials.gov number, NCT00114101.).

Hypercoagulation and thrombophilia in liver disease

Summary.  A complex balance exists between endogenous procoagulants and the anticoagulant system in liver disease patients. Hypercoagulable events occur in cirrhosis patients despite the well‐known bleeding diathesis of liver disease. These events may be clinically evident, such as in portal vein thrombosis or pulmonary embolism, but these conditions may also be a silent contributor to certain disease states, such as portopulmonary hypertension or parenchymal extinction with liver atrophy as well as thrombosis of extracorporeal circuits in dialysis or liver assist devices. Moreover, liver disease‐related hypercoagulability may contribute to vascular disease in the increasingly common condition of non‐alcoholic fatty liver disease. Despite the incidence of these problems, there are few widely accessible and practical laboratory tests to evaluate the risk of a hypercoagulable event in cirrhosis patients. Furthermore, there is little research on the use of commonly accepted anticoagulants in patients with liver disease. This article is a result of an international symposium on coagulation disorders in liver disease and addresses several areas of specific interest in hypercoagulation in liver disease. Critical areas lacking clinical information are highlighted and future areas of research interest are defined with an aim to foster clinical research in this field.

Thrombotic and cardiovascular complications related to nonionic contrast media during cardiac catheterization: Analysis of 8,517 patients

The incidence of major complications associated with nonionic contrast media has not been defined in a large study. Accordingly, cardiovascular complications, especially thrombotic events, were prospectively evaluated in 8,517 consecutive patients undergoing diagnostic cardiac catheterization with either iopamidol (n = 6,293) or iohexol (n = 2,224). Thrombotic events were defined as coronary embolus, coronary occlusion, transient ischemic attack or stroke occurring at the time of catheterization. Thrombotic events occurred in 15 patients (0.18%). Coronary thrombus or embolus occurred in 7 patients, a thromboembolus from the ventricular catheter occurred in 1 patients and transient ischemic attack or stroke occurred in 7 patients. Six of 15 patients with thrombotic events were premedicated with heparin. Thrombotic events were unusual in that they tended to occur in clusters within short time intervals. On 1 occasion, a thrombus was observed in the catheter tip before embolization. Other cardiovascular complications were similarly low with an incidence of ventricular tachycardia/fibrillation of 0.1%, profound bradycardia of 0.2% and prolonged angina of 0.3%. There were 2 deaths unrelated to thrombotic events. Although the clinical thrombotic events associated with nonionic contrast have an unusual temporal clustering and may result in major complications, the overall incidence (0.18%) of these thrombotic complications with nonionic contrast agents is quite similar to that reported with ionic contrast media.

Coagulopathy of Acute Liver Failure

Coagulopathy is an essential component of the acute liver failure (ALF) syndrome and reflects the central role of liver function in hemostasis. ALF is a syndrome characterized by the development of hepatic encephalopathy and coagulopathy within 24 weeks of the onset of acute liver disease. Coagulopathy in this setting is a useful prognostic tool in ALF and a dynamic indicator of the hepatic function. If severe, it can be associated with bleeding and is commonly a major obstacle to the performance of invasive procedures in patients with ALF. This review focuses on the epidemiology, pathophysiology, presentation, evaluation, and management of coagulopathy in ALF.

Comparison of Granulocyte Colony-Stimulating Factor (G-CSF)-Mobilized Peripheral Blood Progenitor Cells and G-CSF-Stimulated Bone Marrow as a Source of Stem Cells in HLA-Matched Sibling Transplantation

HLA-identical bone marrow or stem cell transplantation from a sibling is the preferred treatment for patients with chronic myelogenous leukemia, bone marrow failure syndromes, relapsed acute leukemia, and specific inborn errors of metabolism. Several groups have shown that granulocyte colony-stimulating factor (G-CSF)--mobilized peripheral blood progenitor cells (PBPCs) obtained from HLA-matched siblings are effective in reconstitution of marrow function after marrow ablative conditioning therapy. To evaluate whether G-CSF treatment before bone marrow harvest leads to enhanced recovery of PBPC counts and recovery from limited graft-versus-host disease (GVHD), we assessed the outcome of a sequential cohort of patients treated identically and then given either G-CSF--mobilized PBPCs or G-CSF--stimulated bone marrow from HLA-identical siblings. We show that the time to neutrophil engraftment is identical in the 2 cohorts, whereas platelet engraftment is earlier with the use of PBPCs. The incidence of acute GVHD was decreased, and that of chronic GVHD significantly decreased, in the group receiving bone marrow. Overall survival was not different between the 2 groups. Thus, G-CSF--stimulated bone marrow offers a source of stem cells that allows for early neutrophil engraftment with a decreased risk of GVHD.

Role of procoagulant microparticles in mediating complications and outcome of acute liver injury/acute liver failure†‡

Microparticles (MPs), membrane fragments of 0.1‐1.0 μm, are derived from many cell types in response to systemic inflammation. Acute liver failure (ALF) is a prototypical syndrome of systemic inflammatory response syndrome (SIRS) associated with a procoagulant state. We hypothesized that patients with ALF develop increased procoagulant MPs in proportion to the severity of systemic complications and adverse outcome. Fifty patients with acute liver injury (ALI), 78% of whom also had hepatic encephalopathy (HE; ALF), were followed until day 21 after admission. MPs were characterized by Invitrox Sizing, Antigen Detection and Enumeration, a light‐scattering technology that can enumerate MPs as small as 0.15 μm, and by flow cytometry. Procoagulant activity was assessed by a functional MP‐tissue factor (MP‐TF) assay. Sixteen patients (32%) died and 27 (54%) recovered without liver transplantation (LT). Total MPs (0.15‐1.0 μm) were present in nearly 19‐fold higher concentrations in ALI/ALF patients, compared to healthy controls (P < 0.0001). MP‐TF assays revealed high procoagulant activity (9.05 ± 8.82 versus 0.24 ± 0.14 pg/mL in controls; P = 0.0008). MP concentrations (0.28‐0.64 μm) were higher in patients with the SIRS and high‐grade HE, and MPs in the 0.36‐0.64‐μm size range increased in direct proportion to SIRS severity (P < 0.001) and grade of HE (P < 0.002). Day 1 MPs (0.28‐0.64 μm) correlated with laboratory predictors of death/LT (higher phosphate and creatinine; lower bicarbonate), and day 1 and 3 MPs were higher in patients who died or underwent LT, compared to spontaneous survivors (P ≤ 0.01). By flow cytometry, 87% of patients had circulating CD41+ MPs, indicating platelet origin. Conclusion: Highly procoagulant MPs of specific size ranges are associated with the SIRS, systemic complications, and adverse outcome of ALI/ALF. MPs may contribute to the multiorgan system failure and high mortality of ALF. (HEPATOLOGY 2013;)

Recombinant human factor VIIa (rFVIIa) can activate factor FIX on activated platelets

Summary.  The studies reported here show that factor (F)VIIa can activate factor (F)IX on activated platelets in the absence of tissue factor. Both FIX and FIXa bind to the activated platelet surface with a Kd of 8 nM and 2 nM, respectively. With factor (F)VIIIa, FIXa binds more tightly to platelets (Kd 0.6 nM). At rFVIIa concentrations < 100 nm, no direct binding to the activated platelet surface can be detected with electrophoretic light scattering. However, in the presence of FIX, rFVIIa binding to platelets at concentrations as low as 10 nm rFVIIa can be detected. This is reflected by a decrease in the FIX Kd from 8 to 1.6 nM. When rFVIIa is added to activated platelets in the presence of both FIX and FVIIIa, the Kd for FIX decreases to 0.6, suggesting that rFVIIa activates FIX on the surface of activated platelets in the absence of tissue factor. The activation of FIX by FVIIa on activated platelets can also be demonstrated by a functional assay for FIXa. These data show that pharmacological doses of rFVIIa result in the direct activation of FIX by rFVIIa to form additional tenase complexes ultimately resulting in improved thrombin generation. These results may explain, at least in part, the mechanism of action of rFVIIa in hemorrhagic conditions seen in otherwise normal patients who develop an acquired coagulopathy due to trauma, surgery or a variety of other events in which rFVIIa has been found to be effective.

Analyzing fibrin clot structure using a microplate reader.

Fibrin clot structure studies are often performed using optical methods. For example, the clots fiber structure can be assessed by measuring light scattering as a function of wavelength. From these measurements, one can calculate the mass/length ratio (μ), a relative measure of fibrin thickness. Fiber thickness has important functional correlates in terms of clot stability and resistance to fibrinolysis. Typically, measurements to calculate mass/length ratios are carried out on high-end spectrophotometers. However, limitations of this instrument include the large sample volume required and the inability to read multiple samples at one time. To circumvent these limitations, a plate-reading spectrophotometer is more commonly used to monitor clot formation; increases in absorbance indicate clot formation, while decreases indicate clot lysis. However, it is unclear whether plate-reading spectrophotometers can be used to quantitatively evaluate fibrin fiber structure. In the current study, we compared spectrophotometric analysis of fibrin gels on single-sample and plate-reading spectrophotometers. Results show that a plate-reading spectrophotometer does not give accurate measurements of the fiber mass/length ratio. However, the plate-reading spectrophotometer can provide a qualitative measure of fiber structure for both purified fibrinogen and plasma. We suggest that plate-reading spectrophotometers can provide a convenient, rapid, and inexpensive means of analyzing fibrin clot structure.

Platelet and fibrin modification by radiographic contrast media.

The effect of the radiographic contrast agents, iopamidol and diatrizoate, on fibrin assembly and structure as well as platelet surface charge was studied. Increasing the iopamidol concentration from 0 to 4.5 mM prolongs the fibrin gelation time from 20 to 105 seconds (an anticoagulant effect) and reduces the fibrin fiber mass/length ratio from 3.2 x 10(12) to 0.5 x 10(12) Da/cm (i.e., produces very thin fibrin fibers). Ultraviolet difference spectroscopy of fibrinogen showed both a 15-nm shift in the ultraviolet difference maximum for iopamidol (suggesting binding) and a perturbation of the aromatic amino acid side chain region for fibrinogen (suggesting a conformational change in fibrinogen) as the concentration of iopamidol was increased from 0 to 9 mg/ml. Binding of iopamidol to fibrinogen was also shown by affinity chromatography using a Sepharose-fibrinogen column. Electrophoretic quasi elastic light scattering was used to show platelet interaction with iopamidol as reflected in a reduction in the platelet electrophoretic mobility from 2.0 to 0.5 (microns-cm)/(V-sec) as the concentration of iopamidol was increased from 0 to 4.5 mM. In addition, the ionic radiopaque contrast agent, Renografin, was also studied and found to inhibit fibrin monomer assembly. Although iopamidol is not shown to be thrombogenic, iopamidol does appear to reduce platelet surface charge, bind fibrinogen, and modify fibrin clot structure.

Insights into the inhibition of platelet activation by omega-3 polyunsaturated fatty acids: Beyond aspirin and clopidogrel

OBJECTIVES We sought to examine the effects of escalating doses of omega-3 polyunsaturated fatty acid (PUFA) supplements on platelet function using light transmission aggregometry (LTA) and electrophoretic quasi-elastic light scattering technology (EQELS). BACKGROUND PUFA may inhibit platelet function through fatty acid substitution in the platelet membrane by changing the surface charge density and causing decreased production of thromboxane A2. EQELS can measure platelet surface charge density and determine whether the platelet is in resting or activated state. METHODS A total of 30 volunteers were divided in 3 groups of 10 as follows: Group A, no antiplatelet agent; Group B, daily aspirin only, and Group C, daily aspirin and clopidogrel. All patients received escalating doses of omega-3PUFA from 1 to 8 g daily over 24 weeks. Platelet function was measured by template bleeding time, LTA, and EQELS at baseline and at 6, 12, 18 and 24 weeks. RESULTS Mean bleeding time increased in a dose-dependent manner with escalating omega-3 PUFA doses. LTA confirmed expected antiplatelet effects of aspirin and clopidogrel, but did not detect any additional antiplatelet effects of omega-3 PUFA. EQELS showed a significant increase in the negative resting platelet charge compared to baseline and an attenuated response to arachidonic acid mediated platelet activation. No bleeding events were observed. CONCLUSIONS In this pilot study we were able to successfully measure platelet surface charge variation as a measure of omega-3 PUFA effect on platelets. Our results suggest that omega-3 PUFA increase the total platelet surface charge and, therefore, attenuate platelet activation, even among patients taking aspirin or aspirin plus clopidogrel. Further studies are needed to determine the clinical significance of these measured effects and EQELS results.