Polyethylene Glycol-Like Brush Polymer Conjugate of a Protein Drug Does Not Induce an Antipolymer Immune Response and Has Enhanced Pharmacokinetics than Its Polyethylene Glycol Counterpart.

Protein therapeutics, except for antibodies, have a short plasma half-life and poor stability in circulation. Covalent coupling of polyethylene glycol (PEG) to protein drugs addresses this limitation. However, unlike previously thought, PEG is immunogenic. In addition to induced PEG antibodies, ≈70% of the US population has pre-existing anti-PEG antibodies. Both induced and preexisting anti-PEG antibodies result in accelerated drug clearance, reduced clinical efficacy, and severe hypersensitivity reactions that have limited the clinical utility of uricase, an enzyme drug for treatment for refractory gout that is decorated with a PEG corona. Here, the authors synthesize a poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) conjugate of uricase that decorates the protein with multiple polymer chains to create a corona to solve these problems. The resulting uricase-POEGMA is well-defined, has high bioactivity, and outperforms its PEG counterparts in its pharmacokinetics (PK). Furthermore, the conjugate does not induce anti-POEGMA antibodies and is not recognized by anti-PEG antibodies. These findings suggest that POEGMA conjugation may provide a solution to the immunogenicity and antigenicity limitations of PEG while improving upon its PK benefits. These results transcend uricase and can be applied to other PEGylated therapeutics and the broader class of biologics with suboptimal PK.

Multivalent Albumin-Neonatal Fc Receptor Interactions Mediate a Prominent Extension of the Serum Half-Life of a Therapeutic Protein.

Human serum albumin (HSA) has been used to extend the serum half-life of therapeutic proteins owing to its exceptionally long serum half-life via the neonatal Fc receptor (FcRn)-mediated recycling mechanism. In most cases, only one HSA molecule was conjugated to a therapeutic protein, leading to a limited extension of the serum half-life. In this study, we hypothesized that conjugation of multiple HSA molecules to a therapeutic protein significantly further extends the serum half-life via multivalent HSA-FcRn interactions. We chose urate oxidase (Uox), a tetrameric therapeutic protein used for the treatment of gout, as a model. In previous studies, only one HSA molecule was site-specifically conjugated to one Uox because of poor conjugation yield of the relatively slow bio-orthogonal chemistry, strain-promoted azide-alkyne cycloaddition (SPAAC). To increase the number of HSA molecules conjugated to one Uox, we employed the faster bio-orthogonal chemistry, inverse electron demand Diels-Alder reaction (IEDDA). We site-specifically introduced the phenylalanine analog with a fast-reacting tetrazine group (frTet) into position 174 of each subunit of Uox. We then achieved site-specific HSA conjugation to each subunit of Uox via IEDDA, generating Uox conjugated to four HSA molecules (Uox-HSA4), with a small portion of Uox conjugated to three HSA molecules (Uox-HSA3). We characterized Uox-HSA4 as well as Uox variants conjugated to one or two HSA molecules prepared via SPAAC (Uox-HSA1 or Uox-HSA2). The enzyme activity of all three Uox-HSA conjugates was comparable to that of unmodified Uox. We found out that an increase in HSA molecules conjugated to Uox (multiple albumin-conjugated therapeutic protein) enhanced FcRn binding and consequently prolonged the serum half-life in vivo. In particular, the conjugation of four HSA molecules to Uox led to a prominent extension of the serum half-life (over 21 h), which is about 16-fold longer than that of Uox-WT.

Pharmacokinetics of Polyethylene Glycol-Modified Canine Uricase Following Single and Multiple Intravenous Injections in Cynomolgus Monkeys.

BACKGROUND AND OBJECTIVE: Polyethylene glycol-modified canine uricase (PEG-UHC) prepared with a lower-molecular-weight (5 kDa) PEG is used to treat gout. This study investigated the comparative pharmacokinetics of single and multiple doses of PEG-UHC administered intravenously and a single dose of uricase (UHC) administered intravenously in cynomolgus monkeys. METHODS: A noncompartmental model was used to fit the plasma drug concentration-time curve and calculate the pharmacokinetic parameters of PEG-UHC, which were compared with those obtained for UHC at the equivalent dose (2 mg/kg). To study the pharmacokinetics after multiple dose administration, cynomolgus monkeys were administered five intravenous injections of PEG-UHC (0.5 mg/kg), with one injection performed every 15 days. RESULTS: The area under the curve (AUC) and the maximum plasma concentration (Cmax) of PEG-UHC were positively correlated with dose, whereas plasma half-life (t1/2) and clearance (CL) did not change significantly with increasing dose, suggesting that these pharmacokinetic characteristics are linear. Intravenous PEG-UHC exhibited an average t1/2 that was 125.79 times longer and an AUC0-t that was 64.45 times larger than the corresponding values for UHC at the same dose (2 mg/kg), while the CL of PEG-UHC was 1/72.73 times the CL of intravenous UHC. The plasma drug concentration reached a steady state after five injections, and the t1/2 values following the first and last drug administration did not differ significantly. CONCLUSION: Our data show that PEG-UHC is markedly superior to UHC in terms of duration of action, and that the pharmacokinetics of PEG-UHC in cynomolgus monkeys are linear. Sequential administration of PEG-UHC did not accelerate drug clearance. Our findings provide the basis for future clinical studies of PEG-UHC.

A minimal physiologically based pharmacokinetic model that predicts anti-PEG IgG-mediated clearance of PEGylated drugs in human and mouse.

Circulating antibodies that specifically bind polyethylene glycol (PEG), a polymer routinely used in protein and nanoparticle therapeutics, have been associated with reduced efficacy and increased adverse reactions to some PEGylated therapeutics. In addition to acute induction of anti-PEG antibodies (APA) by PEGylated drugs, typically low but detectable levels of APA are also found in up to 70% of the general population. Despite the broad implications of APA, the dynamics of APA-mediated clearance of PEGylated drugs, and why many patients continue to respond to PEGylated drugs despite the presence of pre-existing APA, remains not well understood. Here, we developed a minimal physiologically based pharmacokinetic (mPBPK) model that incorporates various properties of APA and PEGylated drugs. Our mPBPK model reproduced clinical PK data of APA-mediated accelerated blood clearance of pegloticase, as well as APA-dependent elimination of PEGyated liposomes in mice. Our model predicts that the prolonged circulation of PEGylated drugs will be compromised only at APA concentrations greater than ~500 ng/mL, providing a quantitative explanation to why the effects of APA on PEGylated treatments appear to be limited in most patients. This mPBPK model is readily adaptable to other PEGylated drugs and particles to predict the precise levels of APA that could render them ineffective, providing a powerful tool to support the development and interpretation of preclinical and clinical studies of various PEGylated therapeutics.

Polypeptides with High Zwitterion Density for Safe and Effective Therapeutics.

The commonly used "stealth material" poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti-PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high-dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase-PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase-PEG conjugates.

Bioengineered robust hybrid hydrogels enrich the stability and efficacy of biological drugs.

Biological drugs are exquisitely tailored components offering the advantages of high specificity and efficacy that are considered safe for treating diseases. Nevertheless, the effectiveness of biological drugs is limited by their inherent short biological half-life and poor stability in vivo. Herein, we engineered a novel delivery platform based on hybrid injectable hydrogels, in which pH- and temperature-responsive biodegradable copolymers were site-specifically coupled to the sulfhydryl group of human serum albumin, which effectively enhances the stability and circulation half-life of the biological drug, recombinant uricase enzyme (Uox). The albumin ligand conjugated to the Uox allowed specific-binding of the enzyme within the protein shell, and the synthetic polymers effectively shield the protein-enzyme complex. Such close confinement exhibits strong resistance towards various physical, chemical and therapeutically relevant stressors such as temperature, pH and proteases. Subcutaneous administration of Uox-loaded bioengineered hybrid hydrogel improved the pharmacokinetics by prolonging its circulation half-life. As a consequence, the bioengineered hybrid hydrogel normalized the serum uric acid level in hypoxanthine/potassium oxonate-induced hyperuricemia mice, and no obvious side effects were observed in the major organs. The characteristic of the bioengineered hydrogel networks applicable to a variety of biological drugs by simple mixing that unlock the possibility of adapting biological drugs to therapeutic applications.

Nanocapsules of therapeutic proteins with enhanced stability and long blood circulation for hyperuricemia management.

Among a broad spectrum of medical treatments, protein therapeutics holds tremendous opportunities for the treatment of metabolic disorders, cancer, autoimmune diseases and etc. Broad adaption of protein therapeutics, however, still remain challenging, not only because of poor protein stability, but they also experience fast clearance after administrated and elicit immune responses, resulting in undesirable biodistribution and short blood residence time. In this study, we demonstrate a novel protein delivery method via encapsulating therapeutic proteins within thin shells of poly(N-vinylpyrrolidone) (PVP), which leads to significantly improved protein stability, reduced macrophage uptake, prolonged circulation time and reduced immunogenicity. Exemplified with urate oxidase (UOx), the enzyme used for hyperuricemia treatment, as-formed UOx nanocapsules, n(UOx), exhibits enhanced stability, more significant therapeutic effects, and a more than 10-fold improvement in circulation time when compared with native UOx. This technology not only demonstrates the use of UOx nanocapsules for hyperuricemia management, but also provides a general approach for a broad spectrum of therapeutic proteins for in vivo applications.

Sampling on ice will not yield reliable uric acid monitoring in rasburicase-treated patients.

OBJECTIVES: Rasburicase is administered to prevent hyperuricemia and counteract the consequences of tumour lysis syndrome (TLS). The benefit of monitoring uric acid (UA) concentrations in rasburicase-treated patients is questionable as spuriously low values are most frequently encountered. The manufacturer recommends a cold sample handling procedure to arrest ex vivo uricolysis. Contrariwise, it was recently considered that the temperature does not significantly affects rasburicase uricolysis. We here present a thorough investigation on rasburicase kinetics in clinical samples. DESIGN AND METHODS: UA was spiked in sera from rasburicase-treated patients at varying concentrations, divided in three fractions for incubation at 4°C, 22°C or 37°C and measured at fix time points. The Michaelis-Menten constant (Km) and activation energy (Eact) were estimated by linear regression and the Arrhenius equation, respectively. Additionally, UA concentrations retrieved in sera of rasburicase-treated patients were retrospectively studied (3.5years period). RESULTS: Although uricolysis increased at a higher temperature, incubation at 4°C did not arrest uricolysis entirely. The yielded Km of 128µmol/L highlights that maximum uricolytic activity is reached at UA concentrations lower than those observed for TLS patients. Furthermore, the Eact of 27kJ/mol corresponds to only a modest logarithmic decrease of the uricolytic capacity by 4-5% per -1°C. In routine practise, 'negative' UA concentrations were observed during 88.5% of the rasburicase therapy episodes, even when samples were stored at 4°C. CONCLUSION: In contrast to manufacturer's guidelines, simple cooling of the sample will not arrest the temperature-dependent uricolysis provoked by rasburicase and therefore not yield reliable UA monitoring.

Prediction of Therapeutic Effect of Rasburicase on Hyperuricemia Associated with Chemotherapy Based on Theoretical Model.

Rasburicase has a strong and fast effect for reducing blood levels of uric acid. However, there have been no reports of theoretical analysis for the rational dose and interval of administration. Thus we constructed a pharmacokinetic and pharmacodynamic model to determine changes in uric acid level after rasburicase administration at various doses and regimens. The time courses of uric acid level predicted using our model were in good agreement with observed data, indicating adequate performance for our model. The therapeutic effects after a single infusion at various rates of generation of uric acid were predicted. The maximum effect was not a large difference, in spite of the generation rate. Then, the therapeutic effects of repeated administrations were predicted. The effect did not change when rasburicase was administered at more than the usual dose. Besides, as the administration interval increased, the difference between minimum and maximum level of uric acid became greater. However, in all doses and regimens, adequate therapeutic effects were obtained. In conclusion, the model was found useful for predicting therapeutic effect of rasburicase and individually determining rational dosage regimen of rasburicase.

[The Pharmacokinetics and Pharmacodynamics of Intravenous Uricase Multivesicular Liposomes].

OBJECTIVE: To determine and compare the pharmacokinetics and pharmacodynamics of uricase-multivesicular liposomes (UOMVLs) with free uricase (UOX) in rats. METHODS: UOMVLs were prepared by the double emulsion method and confirmed with its entrapment efficiency, size and Zeta potential. Twelve healthy rats were randomly divided into two groups: one with i. v. injection of UOMVLs, and the other with i. v. injection of UOX. Their serum activity of uricase was assayed. The pharmacokinetic parameters were calculated using software DAS 2. 1. 1. Another 24 male SD rats were enrolled, the rat model of hyperuricemia was established with hypoxanthine and potassium oxonate, while normal group (n=6) was set as control. Injection of UOMVLs (1 mL, 0. 47 U/mL), UOX (1 mL, 0. 47 U/mL) and nothiy were given 1 h later in UOMVLs group (n=6), UOX group (n=6) and model group (n=6), and their serum uric acid levels were determined 1, 2, 3, 5, 7, 9, 12, 24, 36, 48 h after the establishment of hyperuricemia model. RESULTS: The entrapment efficiency of UOMVLs was (63. 75 ± 3. 65) %, with an average particle size of (22. 56 ± 1. 70) µm and Zeta potential of (-41. 81±6. 59) mV. The pharmacokinetic parameters of UOMVLs and UOX were as follows, respectively: area under time-concentration curve from 0 to infinity time (AUC0-∞) (498. 83 ± 58. 85) U/L . h and (28. 49 ± 9. 95) U/L . h; time to peak concentration (Tmax) (1. 00±0. 00) h and (0. 00±0. 00) h; peak concentration (Cmax) (73. 04±6. 35) U/L and (31. 00±6. 03) U/L; elimination half-life (t1/2) (3. 49±0. 80) h and (1. 17±0. 33) h. The relative bioavailability of UOMVLs was (1 750. 90±206. 56) %. UOMVLs decreased serum uric to normal in 9 h; whereas it took 48 h for the UOX group and the model group to return to normal. CONCLUSION: UOMVLs can prolong tmax and t1/2 and improve the relative bioavailability. UOMVLs decrease serum uric acid levels in rats with hyperuricemia more effectively than UOX.

Site-specific albumination of a therapeutic protein with multi-subunit to prolong activity in vivo.

Albumin fusion/conjugation (albumination) has been an effective method to prolong in vivo half-life of therapeutic proteins. However, its broader application to proteins with complex folding pathway or multi-subunit is restricted by incorrect folding, poor expression, heterogeneity, and loss of native activity of the proteins linked to albumin. We hypothesized that the site-specific conjugation of albumin to a permissive site of a target protein will expand the utilities of albumin as a therapeutic activity extender to proteins with a complex structure. We show here the genetic incorporation of a non-natural amino acid (NNAA) followed by chemoselective albumin conjugation to prolong therapeutic activity in vivo. Urate oxidase (Uox), a therapeutic enzyme for treatment of hyperuricemia, is a homotetramer with multiple surface lysines, limiting conventional approaches for albumination. Incorporation of p-azido-l-phenylalanine into two predetermined positions of Uox allowed site-specific linkage of dibenzocyclooctyne-derivatized human serum albumin (HSA) through strain-promoted azide-alkyne cycloaddition (SPAAC). The bio-orthogonality of SPAAC resulted in the production of a chemically well-defined conjugate, Uox-HSA, with a retained enzymatic activity. Uox-HSA had a half-life of 8.8 h in mice, while wild-type Uox had a half-life of 1.3 h. The AUC increased 5.5-fold (1657 vs. 303 mU/mL x h). These results clearly demonstrated that site-specific albumination led to the prolonged enzymatic activity of Uox in vivo. Site-specific albumination enabled by NNAA incorporation and orthogonal chemistry demonstrates its promise for the development of long-acting protein therapeutics with high potency and safety.

Pharmacokinetics and pharmacodynamics of pegloticase in patients with end-stage renal failure receiving hemodialysis.

AIMS: Phase 3 trial data indicate that treatment of chronic tophaceous gout with pegloticase, a recombinant uricase conjugated to polyethylene glycol, does not reduce estimated glomerular filtration rate in chronic kidney disease (CKD) patients and that pegloticase therapeutics are independent of CKD stages 1 - 4. We determined the pharmacokinetics/pharmacodynamics of pegloticase after a single-dose in non-gout subjects with stage 5 CKD receiving hemodialysis. METHODS: In this open-label phase 1 study, 12 subjects received a single intravenous dose of pegloticase 8 mg 3 hours prior to hemodialysis. Blood samples for determination of serum pegloticase concentrations and serum uric acid (SUA) levels were collected immediately predose and at regular intervals before, during, and after hemodialysis. RESULTS: Mean serum pegloticase concentrations remained stable and were unaffected by dialysis sessions. Mean SUA fell to undetectable levels within 3 hours and remained undetected for up to 72 hours postdose. CONCLUSION: Our findings indicate no significant effect of hemodialysis on either the stability of serum pegloticase concentrations after a single dose or the capacity of pegloticase to lower SUA. No new safety signals were detected. Administration of pegloticase in patients with comorbid chronic tophaceous gout and endstage renal failure requiring hemodialysis appears feasible.

Urate crystal degradation for treatment of gout: a nanoparticulate combination therapy approach.

The objective of the present work was to develop polymeric nanoparticles of uricase and aceclofenac (NSAID) and to incorporate them into gel, for delivering drugs to synovial joints, for effective treatment of Gout. Nanoparticles containing uricase and aceclofenac were prepared by double emulsion solvent evaporation method and emulsion solvent evaporation, using PLGA (50:50) as carrier, respectively. Process parameters were optimized using Taguchi L4 orthogonal array and L9 array, respectively. The formulations were characterized for particle size, entrapment efficiency, surface charge, in vitro drug release, ex vivo drug permeation, and urate crystal degradation activity. The particle size and entrapment efficiency for optimized batch was found to be 228.8 nm and 81.26% for uricase nanoparticles and 288.5 nm and 85.36% for aceclofenac nanoparticles, respectively. The developed nanoparticles formulations displayed zero order and Higuchi release kinetics with non-Fickian diffusion, respectively. The in vivo studies were performed in rabbit model. Topical application of gel containing polymeric uricase nanoparticles alone and a combination of both, uricase nanoparticles and aceclofenac nanoparticles in rabbit model test groups, provided complete removal of urate crystals and inflammation within 40 and 25 days of treatment, respectively. The combination treatment therapy resulted in effective treatment of gout due to degradation of crystals and anti-inflammatory response.

Pharmacodynamic analysis of intravenous recombinant urate oxidase using an indirect pharmacological response model in healthy subjects.

AIM: Pharmacodynamic analysis of intravenous recombinant urate oxidase produced by Escherichia coli was performed in healthy subjects using a pharmacokinetic/pharmacodynamic (PK/PD) model. METHODS: A randomized, single-blind, placebo-controlled study was performed in 40 healthy Chinese subjects (4 groups of 10 subjects each, placebo 4:1 ratio) who received infusions of uricase (single doses of 0.1, 0.2, and 0.3 mg/kg; multiple doses of 0.2 mg·kg(-1)·d(-1) for 7 d). PK profiles were determined through plasma uricase activity, and PD profiles were established using uric acid levels in plasma and urine. The plasma PD parameter was estimated as changes in plasma uric acid levels as the effect in the indirect response model. Adverse events were also monitored. RESULTS: A two-compartment PK model with constant iv input and first-order output was used to describe the kinetic process of plasma uricase. The low value (2.8 U/L) of drug concentration that achieved 50% of maximum effect (EC50) indicated that low plasma uricase concentrations were sufficient to produce pharmacological effects. A strong relationship (r(2)=0.9991) between the mean uric acid concentration in blood and the mean uric acid excretion rate in urine in the range of 11 to 30 h after single dosing was found. Infusions of uricase were well tolerated in all subjects. CONCLUSION: The PK/PD model predicted the effective dose to be 0.1 mg/kg in healthy subjects. The excretion rate of uric acid in urine may be used as a new index for pharmacological effects in further clinical trials.

Induced and pre-existing anti-polyethylene glycol antibody in a trial of every 3-week dosing of pegloticase for refractory gout, including in organ transplant recipients.

INTRODUCTION: Pegloticase, a PEGylated recombinant porcine uricase, is approved for treating refractory gout at a dose of 8 mg intravenous (IV) every 2 weeks. However, during phase 1 testing, pharmacokinetics supported less frequent dosing. Also, single doses of pegloticase unexpectedly induced antibodies (Ab) that bound to polyethylene glycol (PEG). We have conducted a phase 2 trial to evaluate every 3-week dosing, and to further define the Ab response to pegloticase. Organ transplant recipients were included, as they are prone to severe gout that is difficult to manage, and because treatment to prevent graft rejection might influence the immune response to pegloticase. METHODS: Plasma uricase activity (pUox), urate concentration (pUA), and clinical response were monitored during up to 5 infusions in 30 patients, including 7 organ transplant recipients. Depending on whether pUA <6 mg/dL was achieved and maintained, patients were classified as non (NR), persistent (PR), or transient (TR) responders. Ab to pegloticase and 10 kDa mPEG were monitored by enzyme linked immunosorbent assay and specificity was further defined. RESULTS: We observed 17 PR, 12 TR, and 1 NR; 21 patients (16 PR, 5 TR) received all 5 infusions. Over the 15-week trial, pUA in PR averaged 1.0 ± 0.4 mg/dL; T½ for pUox was approximately 13 days, and area under the curve after dose 5 was approximately 30% higher than after dose 1. PR showed clinical benefit and in some, tophi resolved. In 11 of 12 TR, pUox fell rapidly and hyperuricemia recurred before dose 2. In all TR and NR, loss of response to pegloticase was accompanied by Ab to PEG, which was pre-existing in half of those who had no prior exposure to pegloticase. No PR, and 1 one out of 7 organ transplant recipients, had a sustained Ab response to pegloticase. CONCLUSIONS: Every 3-week dosing is effective and may enhance the utility of pegloticase for treating refractory gout. Ab to PEG, which were pre-existing or induced by treatment, caused rapid loss of efficacy and increased the risk of infusion reactions. Organ transplant recipients can benefit from pegloticase, and may be less prone than non-recipients to developing anti-PEG Ab. Investigation of immunosuppressive strategies to minimize anti-PEG Ab is warranted. TRIAL REGISTRATION: ClincalTrials.gov identifier: NCT00111657.

Enzyme-entrapped mesoporous silica for treatment of uric acid disorders.

Gout is an abnormality in the body resulting in the accumulation of uric acid mainly in joints. Dissolution of uric acid crystals into soluble allantoin by the enzyme uricase might provide a better alternative for the treatment of gout. This work aims to investigate the feasibility of a transdermal patch loaded with uricase for better patient compliance. Mesoporous silica (SBA-15) was chosen as the matrix for immobilisation of uricase. Highly oriented mesoporous SBA-15 was synthesized, characterized and uricase was physisorbed in the mesoporous material. The percentage adsorption and release of enzyme in borate buffer was monitored. The release followed linear kinetics and greater than 80% enzyme activity was retained indicating the potential of this system as an effective enzyme immobilization matrix. The enzyme permeability was studied with Wistar rat skin and human cadaver skin. It was found that in case of untreated rat skin 10% of enzyme permeated through skin in 100 h. The permeation increased by adding permeation enhancer (combination of oleic acid in propylene glycol (OA in PG)). The permeation enhancement was studied under two concentrations of OA in PG (1%, 5%) in both rat and human cadaver skin and it was found that 1% OA in PG showed better result in rat skin and 5% OA in PG showed good results in human cadaver skin.

Pegloticase for treating refractory chronic gout.

Gout is a metabolic disorder of excess uric acid accumulation that manifests clinically as inflammatory arthritis, chronic arthropathy and the formation of deposits of uric acid known as tophi. A primary objective of gout management is to reduce the excess urate burden by regular use of drugs that reduce serum urate levels. Conventional urate-lowering drugs available in the U.S. are allopurinol, febuxostat and probenecid. Some patients are intolerant to or unresponsive to urate-lowering therapies and, therefore, are said to have refractory gout. Recently, a polyethylene glycol-conjugated uricase, pegloticase, was approved for treating refractory gout. In recent clinical trials, pegloticase normalized plasma urate levels, reduced the size of tophi, and improved functional status and quality of life in patients with refractory disease. Immunogenicity to pegloticase is associated with loss of urate-lowering response and the risk of infusion reactions. Pegloticase is effective in treating hyperuricemia and the clinical manifestations of gout in patients who cannot be adequately managed with conventional therapy.

Characterization, efficacy, pharmacokinetics, and biodistribution of 5kDa mPEG modified tetrameric canine uricase variant.

PEGylated uricase is a promising anti-gout drug, but the only commercially marketed 10kDa mPEG modified porcine-like uricase (Pegloticase) can only be used for intravenous infusion. In this study, tetrameric canine uricase variant was modified by covalent conjugation of all accessible ɛ amino sites of lysine residues with a smaller 5kDa mPEG (mPEG-UHC). The average modification degree and PEGylation homogeneity were evaluated. Approximately 9.4 5 kDa mPEG chains were coupled to each monomeric uricase and the main conjugates contained 7-11 mPEG chains per subunit. mPEG-UHC showed significantly therapeutic or preventive effect on uric acid nephropathy and acute urate arthritis based on three different animal models. The clearance rate from an intravenous injection of mPEG-UHC varied significantly between species, at 2.61 mL/h/kg for rats and 0.21 mL/h/kg for monkeys. The long elimination half-life of mPEG-UHC in non-human primate (191.48 h, intravenous injection) indicated the long-term effects in humans. Moreover, the acceptable bioavailability of mPEG-UHC after subcutaneous administration in monkeys (94.21%) suggested that subcutaneous injection may be regarded as a candidate administration route in clinical trails. Non-specific tissue distribution was observed after administration of (125)I-labeled mPEG-UHC in rats, and elimination by the kidneys into the urine is the primary excretion route.

Pegloticase: a novel agent for treatment-refractory gout.

OBJECTIVE: To evaluate efficacy and safety of pegloticase, approved by the Food and Drug Administration in September 2010 for treatment of patients with chronic treatment-refractory gout. DATA SOURCES: Literature searches were conducted using PubMed (1948-January 2012), TOXLINE, International Pharmaceutical Abstracts (1970-January 2012), and Google Scholar using the terms pegloticase, puricase, PEG-uricase, gout, uricase, and Krystexxa. Results were limited to English-language publications. References from selected articles were reviewed to identify additional citations. STUDY SELECTION AND DATA EXTRACTION: Studies evaluating the pharmacology, pharmacokinetics, safety, and efficacy of pegloticase for the treatment of chronic treatment-refractory gout were included. DATA SYNTHESIS: Pegloticase represents a novel intravenous treatment option for patients who have chronic gout refractory to other available treatments. Pegloticase is a recombinant uricase and achieves therapeutic effects by catalyzing oxidation of uric acid to allantoin, resulting in decreased uric acid concentrations. Results of published trials demonstrate the ability of pegloticase to maintain uric acid concentrations below 7 mg/dL in patients with chronic gout. Data supporting reduction of gout flares are limited. Pegloticase is well tolerated but associated with gout flares and infusion reactions. Other adverse events include nausea, dizziness, and back pain. During Phase 3 trials, 2 patients in the pegloticase biweekly group and 1 in the monthly group experienced heart failure exacerbation; another patient in the monthly group experienced a nonfatal myocardial infarction. Providers should exercise caution before administering pegloticase to patients with cardiovascular disease. The cost burden and safety profile may limit its use in practice, in addition to limited data available to support decreases in patient-centered outcomes (eg, gouty attacks). CONCLUSIONS: Pegloticase is an effective option for patients with symptomatic gout for whom current uric acid-lowering therapies are ineffective or contraindicated.

A new practical system for evaluating the pharmacological properties of uricase as a potential drug for hyperuricemia.

The use of uricase-deficient mammals to screen formulations of engineered uricases as potential drugs for hyperuricemia involves heavy costs and presents a technical bottleneck. Herein, a new practical system was investigated to evaluate the pharmacological significance of a bacterial uricase based on its ability to eliminate uric acid in plasma in vitro, its pharmacokinetics in vivo in healthy rats, and the modeled pharmacodynamics in vivo. This uricase, before and after modification with the monomethyl ether of poly(ethylene glycol)-5000, effectively eliminated uric acid in vitro in rabbit plasma, but its action was susceptible to xanthine inhibition. After intravenous injection of the modified uricase without purification, a bi-exponential model fit well to uricase activities in vivo in the plasma of healthy rats; the half-life of the modified uricase was estimated without interference from the unmodified uricase leftover in the sample and was nearly 100-fold longer than that of the unmodified uricase. Using a model of the elimination of uric acid in vivo taking into account of uricase pharmacokinetics and xanthine inhibition, modeled pharmacodynamics supported that the half-life of uricase and its susceptibility to xanthine are crucial for the pharmacological significance of uricase. Hence, this practical system is desirable for doing preliminary screening of formulations of engineered uricases as potential drugs for hyperuricemia.