PEGylated therapeutic proteins for haemophilia treatment: a review for haemophilia caregivers.

PEGylation is the technology involving the covalent attachment of polyethylene glycol (PEG) to a protein-, peptide- or small-molecule drug to improve their pharmacokinetic, pharmacodynamic and immunological profiles, and thus, enhance the therapeutic effect. Today, PEGylation of proteins is a well-established technology and is being used in the treatment of a variety of clinical disorders. Several PEGylated coagulation proteins for haemophilia A and B are under development with the goal of prolonging the circulation half-life of factor VIII (FVIII) or factor IX. The prolongation of half-life, resulting in less frequent injections can provide significant benefits in improving the quality of life of subjects with haemophilia and improvement in adherence to treatment. A review of published literature on PEGylated therapeutic products currently approved for human use and a discussion of a PEGylated recombinant FVIII molecule (BAY 94-9027, Bayer HealthCare, Berkeley, CA, USA) currently being investigated in the pivotal clinical trial prior to registration is provided. Available safety information of PEGylated proteins containing high molecular weight PEG does not indicate any safety concerns to date, following long-term (chronic) use in animal models or patients. Chronic use of currently available PEGylated products has been shown to be safe, paving the way for chronic use of PEGylated coagulation products in persons with haemophilia.

Learning and memory of rats after long-term administration of low doses of parathion.

A set of four learning and memory tests (Morris Maze I for reference memory, Morris Maze II for working memory, one-way active avoidance, and passive avoidance) were employed to address the questions whether parathion impaired cognitive functions after low, long-term exposure and could cause persistent changes in cognition. Motor activity and general behavior were investigated in a functional observational battery. Parathion was administered in rat food in low doses which caused no clinical symptoms and no or borderline brain acetylcholinesterase inhibition. Parathion doses of 0.5, 2, or 8 ppm in rat food produced the averaged uptake of 24, 100, or 400 microg/kg body weight per group per day in male rats and 36, 152, or 550 microg/kg per day in female rats in week 13. Learning tests were performed in weeks 1 to 4 and 10 to 14, as well as 30 to 34 weeks after the end of treatment, when the male and female rats were about 13 months old. Low doses of parathion given daily for 13 weeks had no cumulative or adverse effects on learning and memory, either during treatment or after the extended treatment-free period, in any of the tests. A significant improvement of learning compared to control observed in the Morris Water Maze I during the first week of treatment (males dose group 0.5 ppm) shows that parathion can improved cognitive functions in rats. Results of the study indicate that adverse effects changing learning and memory in animals may occur only at higher doses of organophosphates, at which the peripheral and brain acetylcholinesterases are inhibited to a greater extent than those in the present study.

Subchronic toxicity of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats.

2,3,7,8-Tetrabromodibenzo-p-dioxin (2,3,7,8-TBDD) was administered daily to male and female rats for 91 days by gavage. Ten male and 10 female rats per group received 0.01, 0.1, 1, 3, or 10 micrograms 2,3,7,8-TBDD/kg body weight per dose per day, solubilised in arachis oil. At 1 microgram/kg per day and above, body weight gain was dose-dependently reduced by treatment. Animals in the 3 and 10 micrograms/kg dose groups showed symptoms of wasting syndrome. Fifty percent of the animals in the 3 micrograms/kg dose-group died and all animals of the highest dose (10 micrograms/kg) died or had to be killed in extremis. Hematological investigations indicated changes--mainly in the 1 and 3 micrograms/kg dose-groups--in hemoglobin content, packed cell volume and number of thrombocytes. The prothrombin-time was markedly prolonged after 3 micrograms/kg in week 13. Clinical chemistry performed at the end of treatment revealed an increase in plasma alkaline phosphatase (APh), aspartate aminotransferase, ASAT and alanine aminotransferase, ALAT (females only) in the highest surviving dose-group (3 micrograms/kg). Marginal changes of APh and ASAT were seen in rats in the 1 microgram/kg dose-group. In the same animals, total bilirubin was elevated. Triglycerides were reduced mainly at 1 and 3 micrograms/kg. Serum thyroxin was reduced, beginning with a marginal change at 0.1 micrograms/kg, triiodothyronine was elevated, starting with a dose of 1 microgram/kg. Thymus weights were reduced in rats of the 1, 3 and 10 micrograms/kg dose-groups. Histopathological analysis showed atrophy of the lymphatic tissue in thymus and spleen. Investigations of the liver indicated peliosis hepatis after treatment with 3 or 10 micrograms/kg. Activities of microsomal enzymes (ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase, aryl hydrocarbon hydroxylase, UDP-glucuronyltransferase) investigated in liver, lung and kidney were dose-dependently elevated after 13 weeks of treatment. At a dose of 3.0 micrograms/kg, activities were below those of the dose 1.0 microgram/kg, probably due to liver toxicity. The induction ratio of kidney was generally higher than in liver and lung. No signs of treatment-related toxicity were observed in the 0.01 and 0.1 micrograms/kg groups after the subchronic administration of 2,3,7,8-TBDD by gavage.

Toxicity of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats after single oral administration.

Five male and female rats per dose-group received 2,3,7,8-tetrabromodibenzo-p-dioxin (2,3,7,8-TBDD) once on the first day of the study. Doses of 10, 33, 100, or 300 micrograms 2,3,7,8-TBDD/kg body wt. and the vehicle control were administered by gavage. About 20% of 2,3,7,8-TBDD was excreted via feces. Severe body weight retardation was observed in the 100 and 300 micrograms/kg dose-groups. Most animals in the 300 micrograms/kg dose-group and the females receiving 100 micrograms/kg showed emaciation, rough coat and a poor health (wasting syndrome). Of the animals dosed with 300 micrograms/kg, 3 males and all females died. After 100 micrograms 2,3,7,8-TBDD/kg 3 females died. Measured 4 weeks after dosing, triiodothyronine (T3) was increased and thyroxin (T4) was reduced dose dependently in serum. A dose-dependent decrease in thymus weights was observed at necropsy and histological examinations showed that thymus and spleen were depleted of mature lymphocytes. An increase in liver-to-body weight ratio was observed in all dose-groups. The histological examination revealed hypertrophy of centrilobular hepatocytes in the liver of animals treated with 100 micrograms/kg, which was less severe at the 33 micrograms/kg dose. Hypertrophic hepatocytes were also detected in some animals at the lowest dose. Induction of enzyme activities of the mixed function oxidases ethoxycoumarin O-deethylase (ECOD), ethoxyresorufin O-deethylase (EROD) and aryl hydrocarbon hydroxylase (AHH) in liver tissue differed for each of the three enzymes. Two days after administration, enzyme activities were increased but did not differ substantially between dose-groups. Twenty-eight days after dosing the increase in activity after 10 micrograms/kg was largest and the EROD of the 100 micrograms/kg dose-group in females was close to that of the control. This inverse dose-response relationship may be due to impaired liver cell function at higher doses.