title: PEGylation confers greatly extended half-life and attenuated immunogenicity to recombinant methioninase in primates.
abstract: Methionine depletion by recombinant methioninase (rMETase) has been demonstrated previously to be highly effective in tumor-bearing mouse models. However, the therapeutic potential of rMETase has been limited by its short plasma half-life and immunologic effects, including high antibody production in mice and monkeys and anaphylactic reactions in monkeys. To overcome these limits of rMETase, the enzyme has been coupled to methoxypolyethylene glycol succinimidyl glutarate (MEGC-PEG-5000). In this study, we evaluated the pharmacokinetics, antigenicity and toxicity of MEGC-PEG-rMETase in Macaca fascicularis monkeys using an escalating-dose strategy. Dose ranging studies at 1,000, 4,000, and 8,000 units/kg i.v. determined that a single dose of 4,000 units/kg was sufficient to reduce plasma methionine to <5 micromol/L for 12 hours. Pharmacokinetic analysis with the single 4,000 units/kg dose showed that MEGC-PEG-rMETase holoenzyme activity was eliminated with a biological half-life of 1.3 hours, and the MEGC-PEG-rMETase apoenzyme was eliminated with a biological half-life of 90 hours, an approximately 36-fold increase compared with non-PEGylated rMETase. A single dose at 2,000 units/kg of MEGC-PEG-rMETase resulted in an apoenzyme half-life of 143 hours. A seven-day i.v. administration of 4,000 units/kg every 12 hours resulted in a steady-state depletion of plasma methionine to <5 micromol/L. The only manifest toxicity was decreased food intake and slight weight loss. Red cell values and hemoglobin declined transiently during treatment but recovered after cessation of treatment. Subsequent challenges on days 29, 50 and, 71 did not result in any immunologic reactions. This result is in contrast to non-PEGylated rMETase, which elicited anaphylactic reactions in monkeys. Anti-MEGC-PEG-rMETase antibodies (at 10(-2)) were found on day 29, and these increased to 10(-3) to 10(4) on day 71, 100 to 1,000-fold less than antibodies elicited by naked rMETase. Although anti-MEGC-PEG-rMETase antibodies were produced, no neutralizing antibody was identified, and each challenge dose was effective in depleting plasma methionine levels. The results of the present study demonstrate that PEGylation greatly prolongs serum half-life of the rMETase apoenzyme and eliminated anaphylactic reactions. The results indicate a profile with respect to serum half-life, toxicity, and antigenicity that suggest clinical potential of MEGC-PEG-rMETase.
authors.affiliation: AntiCancer, Inc., San Diego, California 92111, USA.
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Yang
authors.forename: Junhua
authors.initials: J
authors.lastname: Wang
authors.forename: Quan
authors.initials: Q
authors.lastname: Lu
authors.forename: Jinbao
authors.initials: J
authors.lastname: Xu
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Takakura
authors.forename: Akio
authors.initials: A
authors.lastname: Takimoto
authors.forename: Takayuji
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Changgen
authors.initials: C
authors.lastname: Lian
authors.forename: Chunmei
authors.initials: C
authors.lastname: Chen
authors.forename: Dongdong
authors.initials: D
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shukuan
authors.initials: S
authors.lastname: Li
authors.forename: Xinghua
authors.initials: X
authors.lastname: Sun
authors.forename: Yuying
authors.initials: Y
authors.lastname: Tan
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yagi
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Frenkel
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hoffman
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood; D001835:Body Weight / Q000187:drug effects; D013437:Carbon-Sulfur Lyases / Q000097:blood / Q000276:immunology / Q000493:pharmacokinetics* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D004435:Eating / Q000187:drug effects; D006207:Half-Life; D008252:Macaca fascicularis; D008297:Male; D008715:Methionine / Q000172:deficiency / Q000378:metabolism; D011092:Polyethylene Glycols / Q000493:pharmacokinetics* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000097:blood / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D000906:Antibodies; D004337:Drug Carriers; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; D008715:Methionine; D013437:Carbon-Sulfur Lyases; C474516:PEG-methioninase; C492817:methoxypolyethylene glycol succinimidyl glutarate methioninase conjugate