In order to exploit the elevated methionine dependence of tumors for therapy, recombinant methionine alpha, gamma-lyase (rMETase) has been cloned, overexpressed and purified by our laboratory. The rMETase IC50 for a wide range of tumor cell lines of all major cancer types is significantly lower than that of normal cells tested. rMETase is active as a single agent against human tumors growing in nude mice, and is synergistic with 5-FU and CDDP. Initial Phase I clinical studies have demonstrated that a single administration of rMETase depleted serum methionine levels down to 0.1% (0.1 muM) of baseline. In order to prevent immunological reactions which might be produced by multiple dosing of rMETase, a bacterially-derived protein, and to prolong the half-life of rMETase, rMETase has been initially coupled to polyethylene glycol (PEG). Preliminary results have demonstrated that PEG- rMETase can significantly reduce antigenicity and increase serum half-life, while maintaining potency. In the present application, optimization of PEGylation will be carried out by varying the ratio of PEG linkers and rMETase as well as the length of the reaction. Five different candidate PEG linkers will be evaluated. The PEG-rMETases with the longest serum half-life and methionine depletion period will be chosen for evaluation in active systemic anaphylaxis (ASA) studies in guinea pigs. The MTD and efficacy of PEG-rMETase and the combinations of PEG-rMETase and 5-FU or CDDP will be determined with in metastatic human colon and lung cancer nude mouse models. Mouse survival time will be evaluated as the main endpoint. Pre-clinical studies including acute and sub-acute toxicity studies of PEG- rMETase and further efficacy studies on various human tumor types will be completed in Phase II.

Proposed Commercial Applications

PEG-rMETase should be useful alone or in combination with other types of widely-used anti-neoplastic agents, providing a significant commercial potential.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Small Business Innovation Research Grants (SBIR) - Phase I (R43)
Project #
5R43CA086166-02
Application #
6329112
Study Section
Special Emphasis Panel (ZCA1-SRRB-Y (J4))
Program Officer
Fu, Yali
Project Start
2000-07-01
Project End
2002-06-30
Budget Start
2001-07-01
Budget End
2002-06-30
Support Year
2
Fiscal Year
2001
Total Cost
$192,850
Indirect Cost
Name
Anticancer, Inc.
Department
Type
DUNS #
City
San Diego
State
CA
Country
United States
Zip Code
92111
Yang, Zhijian; Wang, Junhua; Lu, Quan et al. (2004) PEGylation confers greatly extended half-life and attenuated immunogenicity to recombinant methioninase in primates. Cancer Res 64:6673-8
Li, Shukuan; Yang, Zhijian; Sun, Xinghua et al. (2004) Protein carboxyl amidation increases the potential extent of protein polyethylene glycol conjugation. Anal Biochem 330:264-71
Yang, Zhijian; Sun, Xinghua; Li, Shukuan et al. (2004) Circulating half-life of PEGylated recombinant methioninase holoenzyme is highly dose dependent on cofactor pyridoxal-5'-phosphate. Cancer Res 64:5775-8
Li, Shukuan; Yang, Zhijian; Sun, Xinghua et al. (2003) A simultaneous colorimetric assay of free and protein-coupled polyethylene glycol. Anal Biochem 313:335-7
Hoffman, Robert M (2003) PEG-methioninase. Adv Exp Med Biol 519:69-79
Sun, Xinghua; Yang, Zhijian; Li, Shukuan et al. (2003) In vivo efficacy of recombinant methioninase is enhanced by the combination of polyethylene glycol conjugation and pyridoxal 5'-phosphate supplementation. Cancer Res 63:8377-83