Pharmacokinetic profile of defibrotide in patients with renal impairment.

Hepatic veno-occlusive disease, also called sinusoidal obstruction syndrome (VOD/SOS), is an unpredictable, potentially life-threatening complication of hematopoietic stem cell transplant conditioning. Severe VOD/SOS, generally associated with multiorgan dysfunction (pulmonary or renal dysfunction), may be associated with >80% mortality. Defibrotide, recently approved in the US, has demonstrated efficacy treating hepatic VOD/SOS with multiorgan dysfunction. Because renal impairment is prevalent in patients with VOD/SOS, this Phase I, open-label, two-part study in adults examined the effects of hemodialysis and severe or end-stage renal disease (ESRD) on defibrotide pharmacokinetics (PK). Part 1 compared defibrotide PK during single 6.25 mg/kg doses infused with and without dialysis. Part 2 assessed defibrotide plasma PK after multiple 6.25 mg/kg doses in nondialysis-dependent subjects with severe/ESRD versus healthy matching subjects. Among six subjects enrolled in Part 1, percent ratios of least-squares mean and 90% confidence intervals (CIs) on dialysis and nondialysis days were 109.71 (CI: 97.23, 123.78) for maximum observed plasma concentration (Cmax); 108.39 (CI: 97.85, 120.07) for area under the concentration-time curve to the time of the last quantifiable plasma concentration (AUC0-t); and 109.98 (CI: 99.39, 121.70) for AUC extrapolated to infinity (AUC0-∞). These ranges were within 80%-125%, indicating no significant effect of dialysis on defibrotide exposure/clearance. In Part 2, defibrotide exposure parameters in six subjects with severe/ESRD after multiple doses (AUC0-t, 113 µg·h/mL; AUC over dosing interval, 113 µg·h/mL; Cmax, 53.8 µg/mL) were within 5%-8% of parameters after the first dose (AUC0-t, 117 µg·h/mL; AUC0-∞, 118 µg·h/mL; Cmax, 54.9 µg/mL), indicating no accumulation. Defibrotide peak and extent of exposures in those with severe/ESRD were ~35%-37% and 50%-60% higher, respectively, versus controls, following single and multiple doses. One adverse event (vomiting, possibly drug-related) was reported. These findings support defibrotide prescribing guidance stating no dose adjustment is necessary for hemodialysis or severe/ESRD.

Stimulation of endogenous prostacyclin protects the reperfused pig myocardium from ischemic injury.

Several attempts have been undertaken to reduce the severity of ischemic myocardial injury by exogenous administration of eicosanoids and by modification of endogenous eicosanoid production. The present study investigates whether defibrotide, a compound that stimulates endogenous prostacyclin (PGI2), has a beneficial effect in experimental ischemic myocardial injury. Anesthetized, open-chest minipigs were subjected to 1 h of coronary artery occlusion, followed by 3 h of reperfusion. Defibrotide (32 mg/kg x h) or its vehicle were infused i.v. throughout the experiment. Defibrotide increased cardiac PGI2 formation 3- to 4-fold greater than control (P < .05). Thromboxane levels remained unchanged. Irreversible ischemic injury, as identified by negative tetrazolium staining, amounted to 44 +/- 6% of the area at risk in pigs receiving vehicle but was reduced to 23 +/- 4% by defibrotide (P < .05). This reduced tissue injury in defibrotide-treated pigs was associated with improved functional recovery (left ventricular pressure, + dP/dtmax), during early reperfusion. Recovery did not occur in vehicle-treated pigs. Collagen (2 micrograms/ml)-induced platelet aggregation ex vivo was increased in vehicle-treated pigs during ischemia and reperfusion, but not in animals treated with defibrotide. Polymorphonuclear neutrophil leukocyte accumulation in the ischemic border zone was reduced from 59 +/- 17 cells/mm2 in vehicle-treated pigs to 17 +/- 9 cells/mm2 by defibrotide (P < .05). Pretreatment of the animals with indomethacin (3 mg/kg) prevented the reduction of infarct size and polymorphonuclear neutrophil leukocyte infiltration by defibrotide. Indomethacin increased infarct size in vehicle- and defibrotide-treated pigs by 71 and 59%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatography determination of polydeoxyribonucleotides in plasma: its application to the determination of defibrotide's pharmacokinetics in the rabbit.

We describe an HPLC method for the determination of whole polydeoxyribonucleotides in animal plasma. This method was compared to a colorimetric method, which evaluates the sugar moiety of polydeoxyribonucleotides, and to an agarose gel electrophoresis method, which evaluates the whole polydeoxyribonucleotides as does the HPLC method, and was found to give results very close to those obtained with these two other methods. A pharmacokinetic study of the antithrombotic, profibrinolytic, polydeoxyribonucleotidic drug defibrotide was carried out by evaluating the plasma drug levels by these three methods. The pharmacokinetic parameters calculated from the data are very similar.

Cardioprotective effects of defibrotide in acute lethal and nonlethal myocardial ischemia in the cat.

We evaluated the effects of defibrotide (D), a natural profibrinolytic and antithrombotic agent with endogenous PGI2-stimulating properties, on acute lethal and nonlethal myocardial ischemia (L-AMI and NL-AMI) in the cat. The coronary artery was occluded at 12-14 mm from its origin. In L-AMI, 12 of 15 control cats developed ventricular fibrillation and died; D (32 mg kg-1, bolus intravenously plus infusion) provided total protection against death and showed protective effects on plasma and myocardial creatine phosphokinase (CPK), hemodynamics and ECG. In NL-AMI, pretreatment of cats with D at the same dosage (intravenous infusion) reduced AMI-ST segment increases and AMI changes in hemodynamics. AMI-induced changes in lactate adenosine triphosphate and CPK in ischemic tissues were prevented by D. The beneficial effects of D in NL-AMI could be partly attributed to its stimulatory effect on vascular PGI2 release; the mechanism of the impressive protection by D observed in L-AMI has still to be elucidated.

Defibrotide is antithrombotic and thrombolytic against rabbit venous thrombosis.

Defibrotide (D) is a polydeoxyribonucleotide of mammalian origin that has no anticoagulant activity or hemodynamic effects but has considerable profibrinolytic and antithrombotic activities under several experimental conditions. In this paper the dynamics of D's antithrombotic effects after oral administration and D's thrombolystic activity after intravemous infusion on venous collagen-induced thrombosis in the rabbit are reported. D administered orally (12.5, 25 or 50 mg kg-1), from 0 to 360 min before thrombus induction, was able to impede thrombus formation in the first 2 h of growth. There is a linear correlation between the dose of D and peak activity and a correlation, described by a power function, between the dose and the area under the experimental inhibition curve. D infused intravenously (20, 31.7 or 50 mg kg-1 h-1 X 6 h) into rabbits with 24-hour-old thrombi, had significant and impressive dose-related thrombolytic activity. There is a direct relationship between the thrombolytic effect and plasma levels. In this experimental model, urokinase infused intravenously (750, 1,500 or 3,000 IU kg-1 h-1) had the same thrombolytic activity as D; heparin (76 IU kg-1 h-1) was completely ineffective and PGI2 showed a modest activity at 60 nmol kg-1 h-1. The antithrombotic and thrombolytic activities of D may be partly due to its ability to promote release of plasminogen activator factor and of prostacyclin from vascular tissue.

Pharmacokinetics of defibrotide in healthy volunteers.

A pharmacokinetic study of defibrotide, an antithrombotic polydeoxyribonucleotide extract, was performed in 5 healthy volunteers after rapid intravenous injection at three different doses: 0.5, 4 and 16 mg/kg. Defibrotide was given to 2 additional healthy volunteers by slow perfusion of 600 mg over 6 h, after a 200-mg intravenous bolus injection. The blood levels of defibrotide were determined by a method supplied by Crinos (detection of 6-desoxyribose). A one-compartment model was used to describe the kinetics of the drug in plasma. All the most important pharmacokinetic parameters (i.e. elimination constant, half-life, AUC and volume of distribution) were dose dependent. The half-lives were 9.8 min at 0.5 mg/kg, 14.2 min at 4 mg/kg and 21.1 min at 16 mg/kg. The dose-response curves for elimination indicated saturation. During slow infusion following the bolus injection a steady state was reached at 90-120 min, with a blood level of 10-15 micrograms/ml.

[Chromatin breakdown in the white blood cells of rats during irradiation and in combined radiation injury under cystamine protection]. / Raspad khromatina kletok beloi krovi krys pri obluchenii i kombinirovannom radiatsionnom porazhenii v usloviiakh zashchity tsistaminom.

The polydeoxyribonucleotide (PDN) level in leukocytes of peripheral blood of rats treated with cystamine adequately reflects the severity and outcome of radiation sickness. Preventive application of cystamine against the combined effect of ionizing radiation and heat decreased the PDN level in white blood cells but did not influence the survival of animals.

Salmon and human calcitonin-like peptides in man.

Calcitonin-like peptides have been identified in the serum of normal subjects and of medullary thyroid carcinoma (MTC) patients. Using specific homologous radioimmunoassays (RIA) in combination with reversed-phase high performance liquid chromatography and gel permeation chromatography under denaturing conditions, we have recognized major components which coeluted with human calcitonin-(1-32), PDN-21, a carboxyl-terminal flanking peptide derived from the calcitonin mRNA sequence, and salmon calcitonin-(1-32). An additional 12000 molecular weight peak possibly represents a human calcitonin-PDN-21 polyprotein. In both the human calcitonin-(1-32) (normal value less than 0.043 ngEq/ml; MTC 140 +/- 80 ngEq/ml, mean value +/- SEM) and the PDN-21 (normal value less than 0.050 ngEq/ml; MTC 33.6 +/- 16.5 ngEq/ml) RIAs, serum levels were increased in MTC patients. Circulating levels of the salmon calcitonin-like peptide were indistinguishable between normal subjects (0.038 +/- 0.006 ngEq/ml) and MTC patients (0.037 +/- 0.011 ngEq/ml).

[Chromatin degradation of rat peripheral blood leukocytes in the first 3 days after combined radiation injury]. / Issledovanie raspada khromatina leikotsitov perifericheskoi krovi krys v pervye troe sutok posle kombinirovannogo radiatsionnogo porazheniia.

A study was made of chromatin degradation in rat peripheral blood leukocytes 4, 24 and 72 h following the effect of radiation delivered separately and in a combination with burn. Irrespective of the radiation dose a maximum content of products of chromatin degradation was registered 72 h following the effects. The additional trauma (burn of 15% of a body) did not markedly influence the post-irradiation degradation of white blood cell DNP.

Conformation of DNA in chromatin core particles containing poly(dAdT)-poly(dAdT) studied by 31 P NMR spectroscopy.

We have prepared semi-synthetic chromatin core particles from a complex of chicken erythrocyte inner histones (H2A, H2B, H3 and H4) with double-stranded poly(dAdT).poly(dAdT) and studied the conformation of the phosphodiester backbone using 31P NMR at 109.3 MHz. At 20 degrees C, the core particle spectrum is fit well by a single Lorenzian distribution with a line width of 110 Hz. This signal is significantly broader than that for the 145 base pair poly(dAdT).poly(dAdT) alone; the latter consists of two resonances, approximately equal in intensity, with average line width 41 Hz. Major changes in the spectrum ensue on heating the core particle preparation. In conjunction with other results (1) these data suggest four states for the core particle at increasing temperatures. Additionally, analysis of the spectrum of the unmelted core particle and its differences from protein-free DNA of the same length suggests that the conformation of the phosphodiester backbone and/or its interactions with histones along the length of the core particle DNA segment may not be uniform.