Controlled Release of Proteins from Their Poly(Ethylene Glycol) Conjugates:  Drug Delivery Systems Employing 1,6-Elimination

Greenwald, Richard B.; Yang, Kaiyong; Zhao, Hong; Conover, Charles D.; Lee, Stanford; Filpula, David

doi:10.1021/bc025652m

Cited by 79 publications

(86 citation statements)

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“…Cyclization occurs via participation of both hydroxyethyl side chains, and linker detachment releases the original lysine(s) of SS1P plus the morpholinolactone (5). DGA2 and RNL-8a linker characteristics and release mechanisms have also been described (40,41).…”

Section: Resultsmentioning

confidence: 99%

“…As shown in Chart 1, four unconventional releasable linker designs were evaluated. The bis-N-2-hydroxyethylglycine (Bicin3), diglycolic acid (DGA2), and reversible nitrogen linker (RNL-8a) linker chemistries have been recently described with regard to their mechanism of controlled release from PEGylated proteins (39)(40)(41)44). The DGA2 (fast release) and RNL-8a (slow release) linkers are both aromatic designs wherein an initial ester cleavage triggers a classical 1,6-benzyl elimination reaction which releases the original amine and results in linker degradation.…”

Section: Resultsmentioning

confidence: 99%

“…In PEGylation reactions employing releasable linkers such as DGA2, RNL-8a, and Bicin3, SS1P at 1.5-2.5 mg/mL was PEGylated in 0.05-0.1 M sodium phosphate, pH 7.6, 25°C, and purified by reported procedures (40,44). With fast stirring without creating foam, the PEG powder at 10:1 to 50:1 reaction molar ratio of PEG to SS1P was added to the SS1P solution at 1 g/min.…”

Section: Methodsmentioning

confidence: 99%

“…Although conventional PEGylation utilizes stable linkages between the polymers and the protein, recent research has investigated the potential of releasable PEGylation (rPEGylation), wherein the designed covalent linkages of the PEG strands are chemically unstable within a physiological environment and the attached polymers are detached via a controlled release mechanism (30,(39)(40)(41)(42)(43)(44). This unconventional prodrug-based PEGylation approach might have an appropriate application in immunotoxin engineering.…”

Section: Introductionmentioning

confidence: 99%

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Releasable PEGylation of Mesothelin Targeted Immunotoxin SS1P Achieves Single Dosage Complete Regression of a Human Carcinoma in Mice

et al. 2007

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Recombinant immunotoxins exhibit targeting and cytotoxic functions needed for cell-specific destruction. However, antitumor efficacy, safety, and pharmacokinetics of these therapeutics might be improved by further macromolecular engineering. SS1P is a recombinant anti-mesothelin immunotoxin in clinical trials in patients with mesothelinexpressing tumors. We have modified this immunotoxin using several PEGylation strategies employing releasable linkages between the protein and the PEG polymers, and observed superior performance of these bioconjugates when compared to similar PEG derivatives bearing permanent linkages to the polymers. PEGylated derivatives displayed markedly diminished cytotoxicity on cultured mesothelin-overexpressing A431-K5 cells; however, the releasable PEGylated immunotoxins exhibited increased antitumor activity in A431-K5 xenografts in mice, with a diminished animal toxicity. Most significantly, complete tumor regressions were achievable with single dose administration of the bioconjugates but not the native immunotoxin. Pharmacokinetic analysis of the releasable PEGylated derivatives in mice demonstrated an over 80-fold expansion of the area under the curve exposure of bioactive protein when compared to native immunotoxin. A correlation in degree of derivatization, release kinetics, and polymer size with potency was observed in vivo, whereas in vitro cytotoxicity was not predictive of efficacy in animal models. The potent antitumor efficacy of the releasable PEGylated mesothelin-targeted immunotoxins was not exhibited by similar untargeted PEG immunotoxins in this model. Since the bioconjugates can also exhibit the attributes of passive targeting via enhanced permeability and retention, this is the first demonstration of a pivotal role of active targeting for immunotoxin bioconjugate efficacy.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Releasable PEGylation of Mesothelin Targeted Immunotoxin SS1P Achieves Single Dosage Complete Regression of a Human Carcinoma in Mice

et al. 2007

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“…In one approach, the drug is covalently attached to a long-lived circulating macromolecule-such as PEG-through a linker that is slowly cleaved to release the native drug (1,2). We have recently reported such conjugation linkers that self-cleave by a nonenzymatic β-elimination reaction in a highly predictable manner, and with half-lives of cleavage spanning from hours to over a year (3).…”

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confidence: 99%

Hydrogel drug delivery system with predictable and tunable drug release and degradation rates

Ashley

Henise

Reid

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

320

288

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Many drugs and drug candidates are suboptimal because of short duration of action. For example, peptides and proteins often have serum half-lives of only minutes to hours. One solution to this problem involves conjugation to circulating carriers, such as PEG, that retard kidney filtration and hence increase plasma half-life of the attached drug. We recently reported an approach to half-life extension that uses sets of self-cleaving linkers to attach drugs to macromolecular carriers. The linkers undergo β-eliminative cleavage to release the native drug with predictable half-lives ranging from a few hours to over 1 y; however, half-life extension becomes limited by the renal elimination rate of the circulating carrier. An approach to overcoming this constraint is to use noncirculating, biodegradable s.c. implants as drug carriers that are stable throughout the duration of drug release. Here, we use β-eliminative linkers to both tether drugs to and cross-link PEG hydrogels, and demonstrate tunable drug release and hydrogel erosion rates over a very wide range. By using one β-eliminative linker to tether a drug to the hydrogel, and another β-eliminative linker with a longer half-life to control polymer degradation, the system can be coordinated to release the drug before the gel undergoes complete erosion. The practical utility is illustrated by a PEG hydrogel-exenatide conjugate that should allow once-a-month administration, and results indicate that the technology may serve as a generic platform for tunable ultralong half-life extension of potent therapeutics.click chemistry | regenerative medicine | tetra-PEG C onjugation of drugs to macromolecular carriers is a proven strategy for improving pharmacokinetics. In one approach, the drug is covalently attached to a long-lived circulating macromolecule-such as PEG-through a linker that is slowly cleaved to release the native drug (1, 2). We have recently reported such conjugation linkers that self-cleave by a nonenzymatic β-elimination reaction in a highly predictable manner, and with half-lives of cleavage spanning from hours to over a year (3). In this approach, a macromolecular carrier is attached to a linker that is attached to a drug or prodrug via a carbamate group (1; Scheme 1); the β-carbon has an acidic carbon-hydrogen bond (C-H) and also contains an electron-withdrawing "modulator" (Mod) that controls the pK a of that C-H. Upon hydroxide ion-catalyzed proton removal to give 2, a rapid β-elimination occurs to cleave the linkercarbamate bond and release the free drug or prodrug and a substituted alkene 3. The rate of drug release is proportional to the acidity of the proton, and that is controlled by the chemical nature of the modulator; thus, the rate of drug release is controlled by the modulator. It was shown that both in vitro and in vivo cleavages were linearly correlated with electron-withdrawing effects of the modulators and, unlike ester bonds commonly used in releasable linkers (2), the β-elimination reaction was not catalyzed by general bases or ser...

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PEGylation

Dhawan

Kapoor

Kapil

et al. 2011

Pharmaceutical Sciences Encyclopedia

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PEGylation involves the masking of the surface of proteins and peptides by covalent coupling with soluble PEG. It is a method for optimizing pharmacokinetic and pharmacodynamic properties of therapeutic small drug molecules such as peptides and proteins. Thus, this chapter will focus on PEGylation as the modification of the surface properties of proteins and peptide or nonpeptide molecules via covalent attachment using a chemical modifier, PEG, either alone or in combination with other moieties. PEGylation has been exploited to increase the half life ( t 1/2 ), solubility, stability and decrease of the immunogenicity, and toxicity of enzymes, proteins, peptides, and nonpeptide molecules.

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Controlled Release of Proteins from Their Poly(Ethylene Glycol) Conjugates: Drug Delivery Systems Employing 1,6-Elimination

Cited by 79 publications

References 8 publications

Releasable PEGylation of Mesothelin Targeted Immunotoxin SS1P Achieves Single Dosage Complete Regression of a Human Carcinoma in Mice

Releasable PEGylation of Mesothelin Targeted Immunotoxin SS1P Achieves Single Dosage Complete Regression of a Human Carcinoma in Mice

Hydrogel drug delivery system with predictable and tunable drug release and degradation rates

PEGylation

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