-- Antibodies invoke cell mediated tumor killing --
NEW ORLEANS, March 26 /PRNewswire/ -- AltaRex Corp. (TSE: AXO, OTC: ALXFF)
of Waltham, MA, presented today additional data further explaining its
clinical demonstration of effective T cell activation induced by its OvaRex(R)
antibody. The in vitro data give new insight into the importance of complex
formation between the Company's foreign antibodies and specific circulating
tumor associated antigens. The findings are being presented at an oral
poster session by Birgit Schultes, Ph.D., the Company's Director of
Immunology, in collaboration with Dean Mann, M.D., Head of the Division of
Immunogenetics at the University of Maryland, at the 92nd Annual Meeting of
the American Association for Cancer Research (AACR), held in New Orleans.
(Photo: http://www.newscom.com/cgi-bin/prnh/20000831/ALTREXLOGO )
The Company's results demonstrate that the uptake of AltaRex
antibody/antigen complexes by antigen presenting cells (cells that efficiently
present antigens to the immune system) is receptor mediated and results in two
important immunological responses. First, uptake of the complex is most
efficient in the presence of AltaRex's fully murine monoclonal antibodies.
Second, and most importantly, an effective T cell response is generated only
in the presence of the foreign/self complex, and not with antibody alone,
antigen alone, or complexes with humanized or chimeric antibodies. The
antibody/antigen complexes highlighted are OvaRex(R) MAb/CA 125 and
ProstaRex(TM) MAb/PSA.
In order to activate T cells, the immune system needs to process and
present antigens by professional antigen-presenting cells (APCs). The most
potent of the APCs are dendritic cells. In order to generate both a T helper
cell and a cytotoxic T lymphocyte (CTL) response, presentation of antigen-
derived peptides from antigens (e.g. CA 125, PSA) must occur simultaneously
via both major histocompatibility complex (MHC) Class I and Class II
molecules.
This data demonstrates that efficient MHC class I- and II-restricted
presentation of peptides from CA 125 and PSA can occur if they are complexed
with specific murine antibodies and taken up via receptor-mediated endocytosis
rather than through fluid phase. At the same time, immune complexes that
include murine antibodies can induce activation of dendritic cells, resulting
in up-regulation of co-stimulatory molecules (e.g. B7 and MHC Class I),
engagement of T cells and signaling events that lead to activation of the T
cell.
"This dual effect of processing into both MHC pathways and simultaneous
activation of dendritic cells makes foreign antibodies ideal as immune
modifiers to target circulating tumor associated antigens to dendritic cells,"
commented Dr. Schultes. "Systemic, low-dose administration of murine
monoclonal antibodies targeting circulating TAAs is a novel strategy to
activate potent cellular immune responses to cancer. These findings support
how and why these tumor specific immune responses are induced in clinical
settings, as reported earlier this month from the Society of Gynecologic
Oncology Meeting."
The demonstrated mechanism by which a broad antibody-mediated T cell
response is activated provides further evidence that the Company's proprietary
low-dose murine antibodies may be effective across a wide range of cancers.
The activation of T helper cells and CTLs, rather than either one alone, is
believed to be most effective for fighting chronic diseases, such as cancer.
The Company believes that this broad T cell response has been rarely achieved
by others.
Clinical results to date demonstrate that OvaRex(R) MAb, which is directed
against the cancer associated antigen CA 125, complexes with the circulating
antigen and can result in robust immune responses - both humoral (antibody)
and cellular (T cell) - against CA 125 and the cancer.
About AltaRex
AltaRex Corp. is focused on the research, development and
commercialization of antigen-targeted antibody-based cancer therapies,
utilizing monoclonal antibodies as immunotherapeutic agents for the treatment
of certain late-stage cancers. OvaRex(R) MAb targets the tumor associated
antigen CA 125 and is in the final stages of clinical evaluation for ovarian
cancer with commercialization expected in the United States, assuming timely
regulatory approval, in 2002. Clinical data reported to date evidence a
prolongation in time to relapse and/or survival in the treatment of ovarian
cancer, without the toxicities seen with chemotherapy. BrevaRex(R) MAb
targets the tumor associated antigen MUC1 and has successfully completed a
Phase I safety and immunology study. The Company plans to initiate a Phase
I/II clinical study of BrevaRex(R) MAb for the treatment of multiple myeloma
this year. ProstaRex(TM) MAb targets the tumor associated antigen PSA and has
successfully demonstrated robust immune responses in preclinical study.
Additional information about AltaRex (TSE: AXO, OTC: ALXFF) research and
development, news and events can be found on its web site at http://www.altarex.com.
Clinical information can also be found at http://www.centerwatch.com. Additional
information about ovarian cancer can be found at http://www.nci.nih.gov,
http://www.ovarian.org. and at http://www.ovariancanada.org.
This news release contains forward-looking statements that involve risks
and uncertainties, which may cause actual results to differ materially from
the statements made. For this purpose, any statements that are contained
herein that are not statements of historical fact may be deemed to be forward-
looking statements. Without limiting the foregoing, the words "believes,"
"anticipates," "plans," "intends," "expects" and similar expressions are
intended to identify forward-looking statements. Such risks and uncertainties
include, but are not limited to our need for capital and the risk that the
Company can not raise funds on a timely basis on satisfactory terms or at all,
changing market conditions, completion of clinical trials, patient enrollment
rates, uncertainty of preclinical, retrospective and early clinical trial
results, such as the preclinical results referred to above, which may not be
indicative of results that will be obtained in ongoing or future clinical
trials, the establishment of manufacturing processes and new corporate
alliances, the timely development, regulatory approval and market acceptance
of the Company's products, uncertainty as to whether patents will issue from
pending patent applications and, if issued, as to whether such patents will be
sufficiently broad to protect the Company's technology, and other risks
detailed from time-to-time in the Company's filings with the United States
Securities and Exchange Commission and Canadian securities authorities.
THE TORONTO STOCK EXCHANGE HAS NOT APPROVED OR DISAPPROVED OF THE
INFORMATION CONTAINED HEREIN.
SOURCE AltaRex Corp.
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Related links:
http://www.altarex.com
Photo Notes:
NewsCom:
http://www.newscom.com/cgi-bin/prnh/20000831/ALTREXLOGO
AP Archive: http://photoarchive.ap.org
PRN Photo Desk, 888-776-6555 or 201-369-3467
Company News On-Call:
http://www.prnewswire.com/comp/128163.html or fax,
800-758-5804, ext. 128163
CONTACT:
Sondra Henrichon, Director, Investor
Relations and Corporate Communications of AltaRex Corp.,
781-672-0138, ext. 1510, shenrichon@altarex.com; or Wayne Hendry,
Investor Relations of The Equicom Group, Inc., 416-815-0700 ext.
238, whendry@equicomgroup.com
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