title: Pharmacokinetics and stability of the ch14.18-interleukin-2 fusion protein in mice.
abstract: The fusion protein formed from ch14.18 and interleukin-2 (ch14.18-IL-2), shown to exhibit antitumor efficacy in mouse models, consists of IL-2 genetically linked to each heavy chain of the ch14.18 chimeric anti-GD2 monoclonal antibody. The purpose of this study was to determine the pharmacokinetics of ch14.18-IL-2 in mice and assess its stability in murine serum. Following i.v. injection, the fusion protein was found to have a terminal half-life of 4.1 h. Detection of IL-2 following injection of the ch14.18-IL-2 fusion protein showed a similar half-life, indicating that the fusion protein prolongs the circulatory half-life of IL-2. Detection of human IgG1 following injection of ch14.18-IL-2 showed a terminal half-life of 26.9 h. These data suggested that the native fusion protein is being altered in vivo, resulting in a somewhat rapid loss of detectable IL-2, despite prolonged circulation of its immunoglobulin components. In vitro incubation of the ch14.18-IL-2 fusion protein in pooled mouse serum at 37 degrees C for 48 h resulted in a loss of its IL-2 component, as detected in enzyme-linked immunosorbent assay systems and in proliferation assays. Polyacrylamide gel electrophoresis and Western blot analysis of the fusion protein incubated in mouse serum at 37 degrees C indicated that the ch14.18-IL-2 is cleaved, resulting in a loss of the 67-kDa band (representing the IL-2 linked to the IgG1 heavy chain) and the detection of a band of more than 50 kDa, slightly heavier than the IgG1 heavy chain itself. This suggests that the fusion protein is being cleaved in vitro within the IL-2 portion of the molecule. These studies show that (1) ch14.18-IL-2 prolongs the circulatory half-life of IL-2 (compared to that of soluble IL-2) and (2) the in vivo clearance of the fusion protein occurs more rapidly than the clearance of the ch14.18 antibody itself, possibly reflecting in vivo cleavage within the IL-2 portion of the molecule, resulting in loss of IL-2 activity.
authors.affiliation: Department of Medicine, Medical Oncology Section, University of Wisconsin, Madison 53792, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kendra
authors.forename: J
authors.initials: J
authors.lastname: Gan
authors.forename: M
authors.initials: M
authors.lastname: Ricci
authors.forename: J
authors.initials: J
authors.lastname: Surfus
authors.forename: A
authors.initials: A
authors.lastname: Shaker
authors.forename: M
authors.initials: M
authors.lastname: Super
authors.forename: J D
authors.initials: JD
authors.lastname: Frost
authors.forename: A
authors.initials: A
authors.lastname: Rakhmilevich
authors.forename: J A
authors.initials: JA
authors.lastname: Hank
authors.forename: S D
authors.initials: SD
authors.lastname: Gillies
authors.forename: P M
authors.initials: PM
authors.lastname: Sondel
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics / Q000494:pharmacology*; D004355:Drug Stability; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007116:Immunization, Passive / Q000379:methods; D007376:Interleukin-2 / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D011993:Recombinant Fusion Proteins / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics*; D013696:Temperature; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D007376:Interleukin-2; D011993:Recombinant Fusion Proteins; C112746:dinutuximab