Species and sex differences in the blood clearance and immunogenicity of PEGylated uricase: A comparative 26-week toxicity study in rats and monkeys.

Low response rates and high immunogenicity were observed after repeated injections of pegloticase (Krystexxa) into gout patients during clinical trials. However, related research had not been reported in preclinical animal experiments, which has limited the development of this drug. In this study, the toxicity of mPEG-UHC was studied in rats and monkeys over a 26-week period of repeated intravenous dosing. There were no obvious toxic reactions in the tested animals, with the exception of mPEG-UHC blood clearance and immunogenicity. After repeated injections of mPEG-UHC, rapid loss of uricolytic activity (RLA) was not detected in rats, whereas RLA was observed in 44.4% of drug-treated monkeys. In these monkeys, RLA was observed in 11.1% of males and 77.8% of females, and such incidences increased with higher dosing. High titres of anti-uricase IgG antibodies were associated with RLA but did not result in any toxicity. Remission and recurrence of RLA occurred in one female monkey in the high-dose group because of suppressed and altered immune responses in this animal. The predicted incidence of RLA after repeated injections of mPEG-UHC in gout patients may be lower than that of pegloticase. In this study, the no-observed-adverse-effect levels (NOAELs) of mPEG-UHC in rats and monkeys were 32.0 mg/kg and 20.0 mg/kg, respectively. Therefore, the results showed that rats and monkeys could tolerate long-term and high-dose administrations of mPEG-UHC, and mPEG-UHC blood clearance and immunogenicity showed obvious species and sex differences. These findings will provide valuable information to direct the clinical use of mPEG-UHC.

Toxicity assessment of wearable wound sensor constituents on keratinocytes.

This research reports on the cytotoxicity of materials present in a wound biosensor on human keratinocytes (HaCaT) to evaluate the biocompatibility of the sensor for continuous wound monitoring applications. Individual and collective effects of the sensor materials, gold (Au) and silver (Ag) nanoparticles (NPs), uricase enzyme (UOx), ferrocene carboxylic acid (FCA), multi-walled carbon nanotubes (MWCNTs) and poly vinyl alcohol-based polymer (PVA-SbQ) on HaCaT were studied. The toxicology profiles of these materials were derived from cell viability, mitochondrial activity retention and apoptotic behavior studies. At the concentrations present in the sensor, the cell viability studies showed minimal toxicity for Au and Ag NPs, UOx and FCA (cell viability >75%), while MWCNTs and PVA-SbQ exhibited excellent biocompatibility towards keratinocytes (cell viability >90%). Resazurin assay confirmed minimal impairment of mitochondrial activity at lower concentrations for all the materials (mitochondrial activity >0.7). The caspase-3/7 apoptotic assay showed no pronounced apoptotic behavior caused by the materials. The material mixtures studied were Au/UOx/FCA/PVA-SbQ, Ag/UOx/FCA/PVA-SbQ, and MWCNTs/UOx/FCA/PVA-SbQ. A higher toxicity profile was observed for the heterogeneous material mixtures as a result of the cumulative effect of the individual materials. However, the biosensor itself was seen to exhibit lower toxicity (~5%) compared to the material mixtures, due to the protective PVA-SbQ capping over the biosensor. This work establishes the biocompatibility of the reported wound sensor for human measurements with minimal toxic effects on human keratinocytes.

Recombinant urate oxidase (rasburicase) in the prevention and treatment of malignancy-associated hyperuricemia in pediatric and adult patients: results of a compassionate-use trial.

To confirm the efficacy of recombinant urate oxidase (rasburicase) and to establish its safety profile, we reviewed the data on 173 children and 72 adults with malignancy who were treated with this new uricolytic agent in a compassionate-use trial. Rasburicase (0.20 mg/kg) was administered intravenously daily for 1 to 7 days and could be given every 12 h for the initial 72 h. Subsequent courses were allowed at a later date. Rasburicase produced a dramatic decrease in uric acid concentrations in all patients whether they received it for prophylaxis (n = 79) or treatment (n = 166) (P < 0.001 in all comparisons between the levels at diagnosis and those after treatment). The median post-treatment levels were 0.5 to 0.7 mg/dl. Repeated administrations were also effective in all 11 evaluable patients. Four children and five adults had mild adverse reactions that were drug related or of unknown etiology. In two of the children, the adverse events occurred during the second course. Rasburicase is highly effective and safe in the prophylaxis or treatment of malignancy- or chemotherapy-associated hyperuricemia in children and adults.

Urate oxidase in the prophylaxis or treatment of hyperuricemia: the United States experience.

Nonrecombinant urate oxidase (Uricozyme, Sanofi-Synthélabo, Inc, Paris, France) is a highly effective uricolytic agent, but its use is associated with hypersensitivity reaction manifested mainly by bronchospasm in approximately 5% of patients. Recently, several multi-institutional studies have evaluated the efficacy and safety of a recombinant urate oxidase (rasburicase). In a phase I/II study, all 131 patients with newly diagnosed acute lymphoblastic leukemia (ALL) or stage III/IV non-Hodgkin's lymphoma (NHL) experienced rapidly decreased plasma uric acid concentrations after receiving recombinant urate oxidase. Serum creatinine levels also decreased significantly. Toxicity was negligible, and none of the patients required dialysis. In a phase III trial, children with newly diagnosed ALL or stage III/IV NHL were stratified and randomized to receive recombinant urate oxidase or allopurinol. Results showed that the 27 patients who received recombinant urate oxidase had a significantly lower plasma uric acid concentration and a more rapid decline in serum creatinine level than did the 25 who took allopurinol. One patient in the recombinant urate oxidase group had hemolysis of unknown cause, and one in the allopurinol group required hemofiltration for hyperphosphatemia. To further assess the safety profile of recombinant urate oxidase, the data on 245 patients (173 children and 72 adults) who received this agent in a compassionate-use program were reviewed retrospectively. The drug produced dramatic decreases in uric acid concentrations in all patients. Nine patients (four children and five adults) had mild adverse reactions that were drug-related or of unknown etiology. These data suggest that recombinant urate oxidase is safe and effective in the prophylaxis and treatment of hyperuricemia associated with malignancy or chemotherapy.

Control of hyperuricemia in subjects with refractory gout, and induction of antibody against poly(ethylene glycol) (PEG), in a phase I trial of subcutaneous PEGylated urate oxidase.

PEG-modified recombinant mammalian urate oxidase (PEG-uricase) is being developed as a treatment for patients with chronic gout who are intolerant of, or refractory to, available therapy for controlling hyperuricemia. In an open-label phase I trial, single subcutaneous injections of PEG-uricase (4 to 24 mg) were administered to 13 such subjects (11 had tophaceous gout), whose plasma uric acid concentration (pUAc) was 11.3 +/- 2.1 mg/dl (mean +/- SD). By day seven after injection of PEG-uricase, pUAc had declined by an average of 7.9 mg/dl and had normalized in 11 subjects, whose mean pUAc decreased to 2.8 +/- 2.2 mg/dl. At doses of 8, 12, and 24 mg, the mean pUAc at 21 days after injection remained no more than 6 mg/dl. In eight subjects, plasma uricase activity was still measurable at 21 days after injection (half-life 10.5 to 19.9 days). In the other five subjects, plasma uricase activity could not be detected beyond ten days after injection; this was associated with the appearance of relatively low-titer IgM and IgG antibodies against PEG-uricase. Unexpectedly, these antibodies were directed against PEG itself rather than the uricase protein. Three PEG antibody-positive subjects had injection-site reactions at 8 to 9 days after injection. Gout flares in six subjects were the only other significant adverse reactions, and PEG-uricase was otherwise well tolerated. A prolonged circulating life and the ability to normalize plasma uric acid in markedly hyperuricemic subjects suggest that PEG-uricase could be effective in depleting expanded tissue stores of uric acid in subjects with chronic or tophaceous gout. The development of anti-PEG antibodies, which may limit efficacy in some patients, is contrary to the general assumption that PEG is non-immunogenic. PEG immunogenicity deserves further investigation, because it has potential implications for other PEGylated therapeutic agents in clinical use.