Lorus publishes key findings on the antitumor mechanism of action for Virulizin(R)

" The article will also be published in print in an upcoming
issue of the Journal. CAMBRIDGE, Mass.

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Lorus Therapeutics Inc.

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Furthermore , the cytotoxic activity of NK cells was abolished when
macrophages were depleted, or when IL-12 was neutralized with an IL-12
specific antibody in mice, indicating the direct involvement of IL-12 from
macrophages in the induction of NK cells by Virulizin(R).

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Lorus currently
has three products in human clinical trials with a pipeline of eight clinical
trials in phase II clinical trial programs and one phase III registration
clinical trial.Phil, Hybridon's Chief
Executive Officer and Chief Scientific Officer, will present an overview of
the Company and an update on the discovery and drug development programs at
the Rodman + Renshaw Techvest 2nd Annual Global Healthcare Conference in
Paris, France.
The presentation will take place on Wednesday, May 4, 2005 at 10:30 a.

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, Hybridon , Inc.
(Amex: HBY) announced today that Sudhir Agrawal, D.

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Virulizin(R) is a registered trademark of Lorus
Therapeutics Inc. is developing novel therapeutics based on synthetic nucleic
acid chemistry for the treatment of cancer, asthma/allergies, and infectious
diseases.

dosage healthlink

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The results currently appear online in the international journal Cancer
Immunology, Immunotherapy in an article entitled , "Virulizin(R), a novel
immunotherapy agent, activates NK cells through induction of IL-12 expression
in macrophages.

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local time.

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IL-12 was significantly increased in
macrophages isolated from Virulizin(R)-treated mice.

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About Hybridon
Hybridon, Inc.

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"The results of this study are an important addition to earlier findings
that have examined the roles of NK cells, Macrophages , and most recently at
the meeting of the American Society of Clinical Oncology, a presentation on
the production of IL-17 in the Virulizin(R) pathway," said Dr. Jim Wright, CEO
of Lorus Therapeutics . is a public company listed on the
Toronto Stock Exchange under the symbol LOR, and on the American Stock
Exchange under the symbol LRP.

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For more information
please visit our website at http:/ /www.

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To further investigate the critical role of NK cells in the antitumor
activity and interaction of macrophages and NK cells in the network of the
immune system, Lorus conducted studies to verify the involvement of
macrophages in Virulizin(R)-induced NK cell antitumor activity.
It was found that IL-12, a key NK cell stimulatory factor, was involved
in NK cell activation in vivo. The results indicate
that Virulizin(R) induces macrophage IL-12 production, which in turn induces
NK cell-mediated antitumor activity.

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Virulizin(R) stimulates the host's intrinsic antitumor immunity and
activates the innate immune system. Through its own discovery efforts and an
acquisition and in-licensing program, Lorus is building a portfolio of
promising anticancer drugs.hybridon.com.

digeorge immunity

Virulizin(R), Lorus' lead anticancer drug candidate, is in a fully
enrolled pivotal Phase III clinical trial for the treatment of pancreatic
cancer.
The study demonstrates that NK cells play a crucial role in the antitumor
activity of Virulizin(R), as NK cells isolated from Virulizin (R)-treated mice
had increased cytotoxicity against NK-sensitive cells and human melanoma
cells , but not against NK-insensitive cells. NK cell-mediated antitumor activity
appears to rely on the activation of macrophages by Virulizin(R), further
enhancing tumor killing effects. These
forward -looking statements involve risks and uncertainties, including, but not
limited to, changing market conditions, the Company's ability to obtain patent
protection and protect its intellectual property rights, commercialization
limitations imposed by intellectual property rights owned or controlled by
third parties, intellectual property liability rights and liability claims
asserted against the Company, the successful and timely completion of clinical
studies, the establishment of corporate alliances, the impact of competitive
products and pricing, new product development, uncertainties related to the
regulatory approval process, product development delays, the Company's ability
to attract and retain business partners and key personnel, future levels of
government funding, the Company's ability to obtain the capital required for
research, operations and marketing and other risks detailed from time-to-time
in the Company's ongoing quarterly filings, annual information forms , annual
reports and 40-F filings.

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('Lorus'), a biopharmaceutical company specializing in the development and
commercialization of pharmaceutical products and technologies for the
management of cancer, has published peer-reviewed results from the Company's
studies on the mechanism of Virulizin (R)-mediated anticancer activity. Previous studies have shown that
Virulizin(R) induces the antitumor activity of macrophages, and that Natural
Killer (NK) cells play a role in the antitumor efficacy of Virulizin(R).lorusthera.com.

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Virulizin(R) has produced promising efficacy and safety data in
several Phase I/II clinical trials in Canada and the USA.

Forward Looking Statements

Except for historical information, this press release contains forward-
looking statements, which reflect the Company's current expectation and
assumptions, and are subject to a number of risks and uncertainties that could
cause actual results to differ materially from those anticipated. Hybridon's proprietary IMO drug candidates are designed to modulate
immune responses through Toll-like receptors, the body 's first line of defense
against disease.

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In addition, the level of IL-12 beta was also
substantially elevated in the serum of mice treated with Virulizin(R). We undertake no obligation to publicly update or
revise any forward-looking statements, whether as a result of new information,
future events or otherwise.

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About Lorus

Lorus is a biopharmaceutical company focused on the development and
commercialization of cancer therapies. Late-stage clinical development and marketing may
be done in cooperation with strategic pharmaceutical partners.m. The Company's nucleic acid chemistry expertise has also
generated a portfolio of partnered products and intellectual property ,
creating the potential for long-term value for Hybridon.

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Lorus' goal is to capitalize on its
research , preclinical, clinical and regulatory expertise by developing new
drug candidates that can be used , either alone, or in combination, to
successfully manage cancer.

innate deficiency

Lorus Therapeutics Inc.'s press releases are available through the
Company's Internet site: http://www.

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The drug also has
demonstrated excellent anticancer activity in a variety of preclinical human
tumor models including pancreatic cancer, melanoma, breast cancer, ovarian
cancer and prostate cancer. Depletion of NK cells in CD -1
nude mice by an anti-NK specific antibody significantly compromised the
antitumor activity of Virulizin(R).

immune happens

- Essential role of cytokine IL-12 in stimulation of NK cell-mediated
antitumor activity -

TSX: LOR
AMEX: LRP

TORONTO, May 26 - Lorus Therapeutics Inc. Levels of IL-12 alpha and
IL-12 beta mRNA were increased in both peritoneal macrophages and in tumor
xenografts as a result of increased numbers of macrophages following
Virulizin(R) treatment .