In vivo study of newly developed albumin-conjugated urate oxidase for gout treatment.

BACKGROUND: Exogenously providing engineered Uox with enhanced half-life is one of the important urate-lowering treatments for gout. The potential of PAT101, a recombinant human albumin (rHA)-conjugated variant, was evaluated and compared as a novel gout treatment through various in vivo studies with PAT101 and competing drugs. METHODS: PAT101 was produced by site-specific conjugation of rHA and Aspergillus flavus Uox (AfUox-rHA) through clickable non-natural amino acid (frTet) and Inverse electron demand Diels-Alder (IEDDA) reaction. In vivo pharmacokinetics, efficacy tests and in vitro immunogenetic assay were performed after single or multiple doses of PAT101 and its competitors in BALB/c mice, transgenic (TG) mice, Sprague-Dawley (SD) rats, and non-human primate (NHP). RESULTS: The half-life of PAT101 in single-dose treated TG mice was more than doubled compared to pegloticase. In SD rats with 4 weeks of repeated administration of rasburicase, only 24% of Uox activity remained, whereas in PAT101, it was maintained by 86%. In the Uox KO model, the survival rate of PAT101 was comparable to that of pegloticase. In addition, human PBMC-based CD4+/CD8+ T-cell activation analysis demonstrated that PAT101 has a lower immune response compared to the original drug, rasburicase. CONCLUSION: All results suggest that this rHA-conjugated AfUox, PAT101, can be provided as a reliable source of Uox for gout treatment.

Chemical Modification of Cysteine with 3-Arylpropriolonitrile Improves the In Vivo Stability of Albumin-Conjugated Urate Oxidase Therapeutic Protein.

3-arylpropiolonitriles (APN) are promising alternatives to maleimide for chemo-selective thiol conjugation, because the reaction product has a remarkably hydrolytic stability compared with that of thiol-maleimide reactions in vitro. However, whether cysteine modification with APN enhances stability in vivo compared to thiol-maleimide reactions remains unclear, probably due to the too short in vivo serum half-life of a protein to observe significant cleavage of thiol-maleimide/-APN reaction products. The conjugation of human serum albumin (HSA) to a therapeutic protein reportedly prolongs the in vivo serum half-life. To evaluate the in vivo stability of the thiol-APN reaction product, we prepared HSA-conjugated Arthrobacter globiformis urate oxidase (AgUox), a therapeutic protein for gout treatment. Site-specific HSA conjugation to AgUox was achieved by combining site-specific incorporation of tetrazine containing an amino acid (frTet) into AgUox and a crosslinker containing trans-cyclooctene and either thiol-maleimide (AgUox-MAL-HSA) or -APN chemistry (AgUox-APN-HSA). Substantial cleavage of the thioester of AgUox-MAL-HSA was observed in vitro, whereas no cleavage of the thiol-APN product of AgUox-APN-HSA was observed. Furthermore, the in vivo serum half-life of AgUox-APN-HSA in the late phase was significantly longer than that of AgUox-MAL-HSA. Overall, these results demonstrate that the thiol-APN chemistry enhanced the in vivo stability of the HSA-conjugated therapeutic protein.

Thermostable and Long-Circulating Albumin-Conjugated Arthrobacter globiformis Urate Oxidase.

Urate oxidase derived from Aspergillus flavus has been investigated as a treatment for tumor lysis syndrome, hyperuricemia, and gout. However, its long-term use is limited owing to potential immunogenicity, low thermostability, and short circulation time in vivo. Recently, urate oxidase isolated from Arthrobacter globiformis (AgUox) has been reported to be thermostable and less immunogenic than the Aspergillus-derived urate oxidase. Conjugation of human serum albumin (HSA) to therapeutic proteins has become a promising strategy to prolong circulation time in vivo. To develop a thermostable and long-circulating urate oxidase, we investigated the site-specific conjugation of HSA to AgUox based on site-specific incorporation of a clickable non-natural amino acid (frTet) and an inverse electron demand Diels-Alder reaction. We selected 14 sites for frTet incorporation using the ROSETTA design, a computational stability prediction program, among which AgUox containing frTet at position 196 (Ag12) exhibited enzymatic activity and thermostability comparable to those of wild-type AgUox. Furthermore, Ag12 exhibited a high HSA conjugation yield without compromising the enzymatic activity, generating well-defined HSA-conjugated AgUox (Ag12-HSA). In mice, the serum half-life of Ag12-HSA was approximately 29 h, which was roughly 17-fold longer than that of wild-type AgUox. Altogether, this novel formulated AgUox may hold enhanced therapeutic efficacy for several diseases.

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.

Temporal Control of Efficient In Vivo Bioconjugation Using a Genetically Encoded Tetrazine-Mediated Inverse-Electron-Demand Diels-Alder Reaction.

An inverse-electron-demand Diels-Alder (IEDDA) reaction using genetically encoded tetrazine variants enables rapid bioconjugation for diverse applications in vitro and in cellulo. However, in vivo bioconjugation using genetically encoded tetrazine variants is challenging, because the IEDDA coupling reaction competes with rapid elimination of reaction partners in vivo. Here, we tested the hypothesis that a genetically encoded phenylalanine analogue containing a hydrogen-substituted tetrazine (frTet) would increase the IEDDA reaction rate, thereby allowing for successful bioconjugation in vivo. We found that the in vitro IEDDA reaction rate of superfolder green fluorescent protein (sfGFP) containing frTet (sfGFP-frTet) was 12-fold greater than that of sfGFP containing methyl-substituted tetrazine (sfGFP-Tet_v2.0). Additionally, sfGFP variants encapsulated with chitosan-modified, pluronic-based nanocarriers were delivered into nude mice or tumor-bearing mice for in vivo imaging. The in vivo-delivered sfGFP-frTet exhibited almost complete fluorescence recovery upon addition of trans-cyclooctene via the IEDDA reaction within 2 h, whereas sfGFP-Tet_v2.0 did not show substantial fluorescence recovery. These results demonstrated that the genetically encoded frTet allows an almost complete IEDDA reaction in vivo upon addition of trans-cyclooctene, enabling temporal control of in vivo bioconjugation in a very high yield.

Albumin affibody-outfitted injectable gel enabling extended release of urate oxidase-albumin conjugates for hyperuricemia treatment.

Therapeutic proteins are attractive candidates for the treatment of human diseases. However, their short half-life often limits their clinical application. To overcome this problem, injectable hydrogels have been developed as depots for controlled release of therapeutic proteins, but these systems have not yet achieved the desired extended, sustained drug release profile. Our strategy herein was to implement selective and strong interactions between the hydrogels and therapeutic proteins. Specifically, we investigated whether strong and specific interactions between human serum albumin (HSA) and albumin-binding peptide (ABP) can be used to achieve extended release of urate oxidase (Uox), a therapeutic protein for hyperuricemia treatment, from pH- and temperature-sensitive injectable hydrogels consisting of poly(ethylene glycol)-poly(ß-amino ester urethane) (PEG-PAEU) copolymer. Thus, HSA was conjugated to Uox (Uox-HSA) and ABP was introduced in PEG-PAEU (PEG-PAEU-ABP). Polymers, conjugates, and hydrogels were extensively characterized for their physicochemical characteristics and in vivo efficacy in a hyperuricemia mouse model. Briefly, the hydrogels exhibited good injectability, in vitro biocompatibility and extended drug release, and in vivo gel formation and degradability. The serum half-life of the Uox-HSA loaded in PEG-PAEU-ABP hydrogels was ~96 h in mice, which was ~88, ~5.5, and ~2 times longer than that of free native Uox, free Uox-HSA, and Uox-HSA loaded in PEG-PAEU hydrogels, respectively. In the hyperuricemia mouse model, Uox-HSA loaded in PEG-PAEU-ABP hydrogels exhibited a substantially extended period of uric acid-lowering efficacy. These results clearly show that by applying ABP-HSA strong interaction to injectable hydrogels and therapeutic protein, the concentration of the therapeutic protein can be maintained for a long period in vivo, prolonging its therapeutic effect. Further, our approach can be tailored to accommodate other therapeutic proteins, which potentially expands the clinical applicability range of these systems.

Enhanced production of Dopa-incorporated mussel adhesive protein using engineered translational machineries.

Mussel adhesive proteins (MAPs) have great potential as bioglues, particularly in wet conditions. Although in vivo residue-specific incorporation of 3,4-dihydroxyphenylalanine (Dopa) in tyrosine-auxotrophic Escherichia coli cells allows for production of Dopa-incorporated bioengineered MAPs (dMAPs), the low production yield hinders the practical application of dMAPs. This low production yield of dMAPs is due to low translational activity of a noncanonical amino acid, Dopa, in E. coli cells. Herein, to enhance the production yield of dMAPs, we investigated the coexpression of Dopa-recognizing tyrosyl-tRNA synthetases (TyrRSs). To use the Dopa-specific Methanococcus jannaschii TyrRS (MjTyrRS-Dopa), we altered the anticodon of tyrosyl-tRNA amber suppressor into AUA (MjtRNATyrAUA ) to recognize a tyrosine codon (AUA). Co-overexpression of MjTyrRS-Dopa and MjtRNATyrAUA increased the production yield of Dopa-incorporated MAP foot protein type 3 (dfp-3) by 57%. Similarly, overexpression of E. coli TyrRS (EcTyrRS) led to a 72% higher production yield of dfp-3. Even with coexpression of Dopa-recognizing TyrRSs, dfp-3 has a high Dopa incorporation yield (over 90%) compared to ones prepared without TyrRS coexpression.

Comparative studies of the serum half-life extension of a protein via site-specific conjugation to a species-matched or -mismatched albumin.

Human serum albumin (HSA) has been investigated as a serum half-life extender of therapeutic proteins thanks to its unusually long serum half-life. However, in mice, the serum half-life of a HSA-conjugated protein was much shorter than that of HSA in humans, likely due to the species-dependent nature of albumin-FcRn interactions. Herein, we investigated species-dependent albumin-FcRn interactions using species-matched albumin (mouse serum albumin) and species-mismatched albumin (HSA) in non-transgenic mice. We site-specifically introduced a clickable non-natural amino acid to a target protein followed by conjugation to an albumin species via a hetero-bifunctional linker. Using in vitro binding assays, we showed that both HSA- and MSA-conjugated proteins bound mouse FcRns. Conjugation of HSA led to very limited extension of the serum half-life of sfGFP in mice (16.3 h), compared to that of HSA in transgenic mice harboring an allele of mouse FcRn knock-out and expressing humn FcRn (67 h) reported previously. These results suggest that the FcRn-mediated recycling of HSA is not effective in mice. However, conjugation of mouse serum albumin (MSA) resulted in a serum half-life of sfGFP (27.7 h) comparable to that of MSA in mice (28.8 h). Altogether, our study supported that albumin-FcRn interactions are species dependent in vivo.

Controlled Orientation of Active Sites in a Nanostructured Multienzyme Complex.

Multistep cascade reactions in nature maximize reaction efficiency by co-assembling related enzymes. Such organization facilitates the processing of intermediates by downstream enzymes. Previously, the studies on multienzyme nanocomplexes assembled on DNA scaffolds demonstrated that closer interenzyme distance enhances the overall reaction efficiency. However, it remains unknown how the active site orientation controlled at nanoscale can have an effect on multienzyme reaction. Here, we show that controlled alignment of active sites promotes the multienzyme reaction efficiency. By genetic incorporation of a non-natural amino acid and two compatible bioorthogonal chemistries, we conjugated mannitol dehydrogenase to formate dehydrogenase with the defined active site arrangement with the residue-level accuracy. The study revealed that the multienzyme complex with the active sites directed towards each other exhibits four-fold higher relative efficiency enhancement in the cascade reaction and produces 60% more D-mannitol than the other complex with active sites directed away from each other.

Site-Specific Albumination as an Alternative to PEGylation for the Enhanced Serum Half-Life in Vivo.

Polyethylene glycol (PEG) has been widely used as a serum half-life extender of therapeutic proteins. However, due to immune responses and low degradability of PEG, developing serum half-life extender alternatives to PEG is required. Human serum albumin (HSA) has several beneficial features as a serum half-life extender, including a very long serum half-life, good degradability, and low immune responses. In order to further evaluate the efficacy of HSA, we compared the extent of serum half-life extension of a target protein, superfolder green fluorescent protein (sfGFP), upon HSA conjugation with PEG conjugation side-by-side. Combination of site-specific incorporation of p-azido-l-phenylalanine into sfGFP and copper-free click chemistry achieved the site-specific conjugation of a single HSA, 20 kDa PEG, or 30 kDa PEG to sfGFP. These sfGFP conjugates exhibited the fluorescence comparable to or even greater than that of wild-type sfGFP (sfGFP-WT). In mice, HSA-conjugation to sfGFP extended the serum half-life 9.0 times compared to that of unmodified sfGFP, which is comparable to those of PEG-conjugated sfGFPs (7.3 times for 20 kDa PEG and 9.5 times for 30 kDa PEG). These results clearly demonstrated that HSA was as effective as PEG in extending the serum half-life of a target protein. Therefore, with the additional favorable features, HSA is a good serum half-life extender of a (therapeutic) protein as an alternative to PEG.