Methoxypoly(ethylene glycol)-conjugated carboxypeptidase A for solid tumor targeting

Single enzyme nanoparticle, an effective tool for enzyme replacement therapy

The term "single enzyme nanoparticle" (SEN) refers to a chemically or biologically engineered single enzyme molecule. SENs are distinguished from conventional protein nanoparticles in that they can maintain their individual structure and enzymatic activity following modification. Furthermore, SENs exhibit enhanced properties as biopharmaceuticals, such as reduced antigenicity, and increased stability and targetability, which are attributed to the introduction of specific moieties, such as poly(ethylene glycol), carbohydrates, and antibodies. Enzyme replacement therapy (ERT) is a crucial therapeutic option for controlling enzyme-deficiency-related disorders. However, the unfavorable properties of enzymes, including immunogenicity, lack of targetability, and instability, can undermine the clinical significance of ERT. As shown in the cases of Adagen®, Revcovi®, Palynziq®, and Strensiq®, SEN can be an effective technology for overcoming these obstacles. Based on these four licensed products, we expect that additional SENs will be introduced for ERT in the near future. In this article, we review the concepts and features of SENs, as well as their preparation methods. Additionally, we summarize different types of enzyme deficiency disorders and the corresponding therapeutic enzymes. Finally, we focus on the current status of SENs in ERT by reviewing FDA-approved products.

PEG-chitosan branched copolymers to improve the biocatalytic properties of erwinia carotovora recombinant L-asparaginase

A new approach to the regulation of catalytic properties of medically relevant enzymes has been proposed using the novel recombinant preparation of L-asparaginase from Erwinia carotovora (EwA), a promising antitumor agent. New branched co-polymers of different composition based on chitosan modified with polyethylene glycol (PEG) molecules, designated as PEG-chitosan, have been synthesized. PEG-chitosan copolymers were further conjugated with EwA. In order to optimize the catalytic properties of asparaginase two types of conjugates differing in their architecture have been synthesized: (1) crown-type conjugates were synthesized by reductive amination reaction between the reducing end of the PEG-chitosan copolymer and enzyme amino groups; (2) multipoint-conjugates were synthesized using the reaction of multipoint amide bond formation between PEG-chitosan amino groups and carboxyl groups of the enzyme in the presence of the Woodward’s reagent. The structure and composition of these conjugates were determined by IR spectroscopy. The content of the copolymers in the conjugates was controlled by the characteristic absorption band of C-O-C bonds in the PEG structure at the frequency of 1089 cm-1. The study of catalytic characteristics of EwA preparations by conductometry showed that at physiological pH values the enzyme conjugates with PEG-chitosan with optimized structure and the optimal composition demonstrated 5-8-fold higher catalytic efficiency (kcat/Km) than the native enzyme. To certain extent, this can be attributed to favorable shift of pH-optima in result of positively charged amino-groups introduction in the vicinity of the active site. The proposed approach, chito-pegylation, is effective for regulating the catalytic and pharmacokinetic properties of asparaginase, and is promising for the development of prolonged action dosage forms for other enzyme therapeutics

Diethylstilbestrol glutamate as a potential substrate for ADEPT

The combination of systemic toxicity, water insolubility and a labile chemical structure has limited the clinical use of diethylstilbestrol (DES) 1 for the treatment of prostate cancer. To determine if DES could potentially be a prodrug substrate for the pre-targeting strategy known as antibody directed enzyme prodrug therapy (ADEPT), the DES-glutamate 5 was prepared. The synthesis required the activation of the bis-t-butyl glutamate ester 2 to the isocyanate 3 followed by addition of DES 1. The desired DES-glutamate 5 was water-soluble and upon incubation with carboxypeptidase G2 (CPG2) underwent carbamate cleavage to give DES 1. A control reaction in the absence of CPG2 demonstrated that the enzyme was necessary for rapid glutamate cleavage to give DES 1. HPLC analysis was required to follow the reaction of DES-glutamate 5 with CPG2. These preliminary results suggest that it may be possible to examine an ADEPT strategy for DES provided enzymatic kinetics can be measured.

PEGylation of microspheres for therapeutic embolization: Preparation, characterization and biological performance evaluation

In this study, microspheres designed for embolization, defined as GF2000-Trisacryl MS (GF-MS) and DEAE-Trisacryl MS (DEAE-MS), were originally PEGylated using (3-amino propyl) triethoxy silane as coupling agent. Indomethacin was loaded into both PEGylated and non-PEGylated DEAE-MS, displaying ion-exchange ability, through a batch process with a respective capacity of 1.2 and 0.25 g/g. The morphology of naked and PEGylated MS was evaluated by scanning electron microscopy (SEM). Both micosphere resins surface looked like orange skin, although DEAE-MS showed a slightly rougher surface due to the copolymerization process. PEGylated microspheres have a most likely swelling surface owing to the presence of PEG hydrophilic chains. The mean diameters were of about 66 and 60 microm for GF-MS and DEAE-MS, respectively. Data obtained for PEGylated MS by Fourier Transform Infrared spectroscopy (FTIR) confirmed that microspheres were successfully PEGylated. Finally, complement activation in vitro was performed to evaluate the activating capacity of different microspheres. Both PEGylated GF-MS and DEAE-MS activated the complement system of about 33% less than their corresponding naked microspheres, while loading PEGylated DEAE-MS with indomethacin almost suppressed complement activation. This inhibiting role implies that PEGylation as well as loading the microspheres with anti-inflammatory drug has a compact effect on the interaction of microspheres with blood proteins.

Modification of allergenicity and immunogenicity of formate dehydrogenase by conjugation with linear mono methoxy poly ethylene glycol: Improvement in detoxification of formate in methanol poisoning

BACKGROUND

Single bolus intravenous infusion of native formate dehydrogenase (FD), isolated from Candida boidinii was found to eliminate formate, a highly toxic metabolite in methanol poisoning. In order to prevent immunological reactions which might be produced by multiple dosing of formate dehydrogenase and to prolong the serum half life of the enzyme, the N-hydroxysuccinimidyl ester of methoxy polyethylene glycol propionic acid (mPEG-SPA 5000) was conjugated to native formate dehydrogenase.

METHOD

PEGylation reactions were run at 20 degrees C for 30 min in a reaction buffer (0.2 mol/l sodium phosphate buffer, pH 8.3). The PEGylated molecules were purified from unreacted PEG with Amicon Ultra-4 (10 K) and by Sephacryl S-300 HR gel-filtration chromatography. Unreacted formate dehydrogenase molecules were removed by DEAE Sepharose FF anion-exchange chromatography. PEG-FD enzyme molecules obtained from reacting ratio of FD/PEG of 1/40 had an enzyme activity of 68% of unmodified enzyme. Immunogenicity of PEGylated and native enzyme was evaluated by ELISA. Allergenicity was evaluated by active systemic anaphylaxis and passive cutaneous anaphylaxis tests. In vivo efficacy of PEG-FD or native FD was comparatively evaluated by single intravenous administration of PEG-FD or native FD in folate deficient methanol intoxicated albino rats along with Carbicarb buffer infusion. Methanol and formate were estimated at specific time points respectively with HPLC and fluorescence spectrophotometer.

RESULT

PEG-FD had comparatively longer half life and lower immunogenicity than native FD. PEG-FD had better in vivo efficacy than native FD in eliminating the formate.

CONCLUSION

Conjugation of mPEG-SPA 5000 with native FD reduces its immunogenicity and increases its efficacy in detoxification of formate in methanol poisoning.