Improved circulating half-life and efficacy of an antibody-interleukin 2 immunocytokine based on reduced intracellular proteolysis.
OBJECTIVE
Previous studies showed that reducing the interaction of antibody-interleukin 2 immunocytokines with Fc receptors improved their circulating half-life in mice and increased their antitumor activity. We sought to modify sequences that would increase half-life but retain the ability to activate Fc receptor-mediated effector functions.


METHODS
Modified immunocytokines were assessed in vitro for effector function and protease sensitivity and in vivo for pharmacokinetic and antitumor activities in an syngeneic tumor regression model.


RESULTS
Single amino acid changes in the junction sequence between the antibody and interleukin-2 components had dramatic effects on circulating half-life and antitumor activity. This effect was independent of Fc receptor binding to either Fcgamma receptors or the Fc protection receptor, but was associated with changes in susceptibility to intracellular proteases.


CONCLUSIONS
We have identified modifications that dramatically improve the circulating half-life of immunocytokines based on increased resistance to intracellular degradation and thus have demonstrated how these molecules can be recycled in and out of an intracellular compartment. Use of these improved immunocytokines with highly favorable pharmacokinetic properties and retained effector functions should lead to more effective treatment of epithelial cancers.
Gillies
Stephen D
SD
Lexigen Pharmaceuticals Corp., Lexington, Massachusetts 02421-3125, USA.
Lo
Kin-Ming
KM
Burger
Christa
C
Lan
Yan
Y
Dahl
Thomas
T
Wong
Wai-Keung
WK
D000818:Animals; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism; D003110:Colonic Neoplasms / Q000276:immunology / Q000517:prevention & control; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics; D007141:Immunoglobulin Fc Fragments / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics* / Q000627:therapeutic use; D014018:Tissue Distribution; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D018796:Immunoconjugates; D007141:Immunoglobulin Fc Fragments; D007376:Interleukin-2; D011993:Recombinant Fusion Proteins; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse