Drug Delivery Systems Employing 1,6-Elimination:  Releasable Poly(ethylene glycol) Conjugates of Proteins

Abstract

Using lysozyme as a representative protein substrate that loses its activity when PEGylation takes place on the epsilon-amino group of lysine residues, various amounts of a novel releasable PEG linker (rPEG) were conjugated to the protein. rPEG-lysozyme conjugates were relatively stable in pH 7.4 buffer for over 24 h. However, regeneration of native protein from the rPEG conjugates occurred in a predictable manner during incubation in high pH buffer or rat plasma, as demonstrated by enzymatic activity and structural characterization. The rates of regeneration were also correlated with PEG number: native lysozyme was released more rapidly from the monosubstituted conjugate than from the disubstituted conjugate, suggesting possible steric hindrance to the approach of cleaving enzymes. Recovery of normal activity and structure for the regenerated native lysozyme was shown by a variety of assays.

Reversible PEGylation of peptide YY3‐36 prolongs its inhibition of food intake in mice

“…They suffer, however, from major potential drawbacks. For example, reliance on enzymatic detachment of PEGs from conjugates by serum proteases and/or esterases as a rate determining step [21][22][23] might not yield desirable pharmacokinetic profiles in vivo and may be subject to fluctuations due to changes in enzyme availability. Similarly, disulfide-bonded conjugates are not cleaved in the non-reducing environment of body fluids [24].…”

Prolonging the Action of Protein and Peptide Drugs by a Novel Approach of Reversible Polyethylene Glycol Modification

“…by employing detachable PEG chains) have been reported (11)(12)(13)(14)(15). They suffer, however, from major disadvantages including their dependence on enzymatic hydrolysis as the rate-determining step of PEG-parent molecule dissociation (11)(12)(13), potentially making the behavior of the molecules unpredictable and their utilization impractical because of steric considerations and inappropriate enzyme availability. An additional disadvantage is the nonspecific PEGylation of undesired protein/peptide functional moieties (e.g.…”

Modulating the pharmacokinetics of therapeutic antibodies

“…Here, the bioactivity, previously lost upon conjugation, is restored over time (Greenwald 2001;Lee et al 2001;Zalipsky et al 2007;Filpula and Zhao 2008). However, this technology has not been applied to antibodies as generally, antibody immuno-reactivity is preserved upon polymer conjugation.…”