OSLO, Norway, April 28 /PRNewswire/ -- Affitech AS, the human antibody therapeutics company, announced today that preclinical data on two fully human anti-PS (phosphatidylserine) antibodies were presented by its collaboration partner Peregrine Pharmaceuticals at the 100th Annual Meeting of the American Association for Cancer Research (AACR) 2009 held during April 18 - 22, 2009 in Denver, CO. The preclinical studies of PGN635 and PGN632 provided further confirmatory evidence that the anti-tumor effects observed with anti-PS antibodies reflect their immunomodulatory mechanism of action, including their ability to stimulate the immune system. Additionally, PGN635 demonstrated encouraging signs of efficacy in a preclinical model of prostate cancer. Both antibodies were isolated using Affitech's unique MBAS (Molecule Based Antibody Screening) method for selection and improvement of fully human antibodies from large libraries.
The researchers from Peregrine, Affitech and UT Southwestern Medical Center confirmed previous observations that in vitro, anti-PS antibodies stimulate the tumor microenvironment to recruit monocytes and other immune cells to the tumor with resulting anti-tumor effects, most likely via cell-mediated mechanisms such as antibody-dependent cell-mediated cytotoxicity (ADCC). Their data further defined the role of anti-PS antibodies in mediating tumor cell cytotoxicity and the tumor microenvironment, showing that the anti-PS antibody induced a sequential release of cytokines and beta-chemokines and stimulated enhanced macrophage recruitment to tumors. Furthermore, the researchers showed that in vitro, PGN635 induced antibody-dependent death of endothelial cells, the same cell type found in the tumor vasculature, a key target of anti-PS cancer therapy. The studies also demonstrated the anti-tumor potential of PGN635 in vitro and in a number of animal cancer models. Specifically, in a mouse model of prostate cancer, treatment with a mouse equivalent of PGN635 significantly retarded the growth of tumors by more than 90%.
In a separate study, researchers from UT Southwestern Medical Center (Peregrine's academic collaborators) and Affitech demonstrated in in vitro studies that immature dendritic cells cultured in the presence of PGN632 exhibited a significant increase in the production of inflammatory cytokines and chemokines. PGN632 also induced an increase in the expression of cell-surface molecules that are indicative of mature dendritic cells and that assist in antigen presentation functions, as well as in stimulating T-cell proliferation.
"These results demonstrate the efficiency and robustness of Affitech's range of antibody discovery platforms which include CBAS (Cell Based Antibody Screening) in addition to MBAS. They are being applied with increasing success to build proprietary oncology pipelines for both collaborators such as Peregrine and for ourselves," said Dr Martin Welschof, CEO of Affitech AS.
Commenting on the research progress of the antibodies and Peregrine's collaboration with Affitech, Steven King, President and CEO of Peregrine Pharmaceuticals said, "As leaders in the development of anti-PS antibodies for both oncology and anti-viral applications, we are delighted with these promising data for our fully human anti-PS antibodies from Affitech. They are the result of our well-established and highly productive collaboration and we look forward to continuing success in this and other projects."
For more information on Peregrine's anti-PS programs, visit http://www.peregrineinc.com
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