Enhanced circulating half-life and antitumor activity of a site-specific pegylated interferon-alpha protein therapeutic

Bioconjug Chem. 2008 Jan;19(1):299-305. doi: 10.1021/bc070131q. Epub 2007 Nov 20.


Recombinant interferon alpha-2 (IFN-alpha2) has proven useful for treating a variety of human cancers and viral diseases. IFN-alpha2 has a short circulating half-life in vivo, which necessitates daily or thrice weekly administration to patients. It is possible to extend the circulating half-life of IFN-alpha2 by random modification of lysine residues in the protein with polyethylene glycol (PEG); however, such preparations have heterogeneous structures and low specific activities, and may not provide optimal therapeutic benefits to patients. A long-acting, site-specific, monoPEGylated IFN-alpha2 protein has now been created by targeted attachment of a 20 kDa or a 40 kDa maleimide-PEG to a cysteine analogue of IFN-alpha2, M111C. In vitro bioactivities of the purified 20 kDa and 40 kDa PEG-M111C proteins were within 2- to 3-fold of those of wild type IFN-alpha2 and 7- to 10-fold better than that of a 40 kDa PEG IFN-alpha2 protein created using nontargeted, amine-PEGylation methodology. The 20 kDa and 40 kDa PEG-M111C proteins demonstrated 26- to 38-fold longer half-lives, respectively, than IFN-alpha2 following subcutaneous administration to rats. The 20 kDa PEG M111C protein inhibited growth of human NIH:OVCAR-3 cells transplanted into nude mice by >90%, as measured by tumor size, tumor weight, and number of animals with detectable tumors at necropsy, and was significantly more effective than a comparable dose of IFN-alpha2. These data extend our previous findings that bioactivity of IFN-alpha2 can be largely preserved by targeted attachment of PEG moieties to nonessential sites in the protein and provide evidence that site-specific PEGylated IFN-alpha2 proteins possess enhanced tumoricidal properties in vivo.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antineoplastic Agents / blood*
  • Antineoplastic Agents / pharmacokinetics
  • Antineoplastic Agents / pharmacology*
  • Binding Sites
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cysteine
  • Half-Life
  • Humans
  • Interferon-alpha / blood*
  • Interferon-alpha / chemistry
  • Interferon-alpha / pharmacokinetics
  • Interferon-alpha / pharmacology*
  • Mice
  • Mice, Nude
  • Polyethylene Glycols / chemistry*
  • Recombinant Proteins / blood
  • Recombinant Proteins / pharmacokinetics
  • Recombinant Proteins / pharmacology
  • Sensitivity and Specificity
  • Transplantation, Heterologous


  • Antineoplastic Agents
  • Interferon-alpha
  • Recombinant Proteins
  • Polyethylene Glycols
  • Cysteine