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CONTACTS:
LORUS THERAPEUTICS INC. CANADIAN MEDIA CONTACT: US MEDIA CONTACT:

Corporate Communications Hugh Mansfield Jennifer Taylor
Grace Tse Mansfield Communications Inc. Mansfield Communications Inc.
Tel: (416) 798-1200, ext.380 Tel: (416) 599-0024 Tel: (212) 370-5045
Email:ir@lorusthera.com Email: hugh@mcipr.com E-mail: jennifer@mcipr.com
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LORUS THERAPEUTICS DESCRIBES RESEARCH FINDINGS ON ANTISENSE
ANTI-TUMOR ACTIVITY AT 19TH ANNUAL ONCOGENE MEETING

- Company broadens its antisense pipeline -

TSE: LOR
OTC BB: LORFF

TORONTO, CANADA, JUNE 20, 2003 - Lorus Therapeutics Inc. ("Lorus") announced
today that its preclinical findings on the anti-tumor activity of thioredoxin
antisense molecules will be presented today at the 19th Annual Oncogene Meeting
at Hood College, Frederick, Maryland.

Lorus' presentation titled, "Anti-Tumor Activity of Antisense
Oligodeoxynucleotides Targeted Against Human Thioredoxin," describes the
company's study results, which will also be published in the conference meeting
book.

Thioredoxin, a molecule involved in cancer cell growth and in protection of
cancer cells from damage and death, has been implicated in tumor formation,
progression and metastasis (spread of tumor cells) by a variety of mechanisms. A
number of tumors including lung, colon, cervical, gastric and hepatocellular
carcinoma, squamous cell carcinoma, myeloma, non-Hodgkins lymphoma,
mesothelioma, and acute lymphocytic leukemia, showed elevated levels of
thioredoxin.

Expression levels of thioredoxin correlate with malignancy and with
proliferative index (a measure of the rate of cancer cell growth) and disease
prognosis. Furthermore, the over-expression of thioredoxin has been linked with
resistance to chemotherapeutic agents. Reducing the level of thioredoxin using
antisense drugs should interfere with multiple pathways that lead to cancer
progression, and as a result, there is the potential to inhibit tumor growth and
metastasis.
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Lorus' studies using human tumor cells and mouse models bearing human tumors
support this approach. A number of antisense molecules designed to target
thioredoxin were shown to significantly inhibit the growth of a variety of human
tumor cells in culture. Furthermore, these molecules inhibited the growth and
spread of human tumor cells in experimental tumor and metastasis models in mice.
Based on these studies, Lorus has chosen a lead compound that demonstrated high
anti-tumor efficacy.

"Lorus currently has two antisense therapeutics in clinical trials, GTI-2040 and
GTI-2501, and has devoted an active research program to the discovery and
evaluation of additional tumor targets amenable to antisense therapy," said Dr.
Jim Wright, chief executive officer, Lorus. "The identification of thioredoxin
antisense compounds with very promising anti-tumor activity adds significant
value to this drug discovery program."

About Lorus

Lorus is a biopharmaceutical company focused on the research and development of
cancer therapies. Lorus' goal is to capitalize on its research, pre-clinical,
clinical and regulatory expertise by developing new drug candidates that can be
used, either alone, or in combination, to successfully manage cancer. Through
its own discovery efforts and an active acquisition and in-licensing program,
Lorus is building a portfolio of promising anti-cancer drugs. Late-stage
clinical developments and marketing will be done in cooperation with strategic
pharmaceutical partners. Founded in 1986, Lorus Therapeutics Inc. is a public
company listed on the Toronto Stock Exchange under the symbol LOR, and on the
OTC BB exchange under the symbol LORFF.

Except for historical information, this press release contains forward-looking
statements, which reflect the Company's current expectation regarding future
events. These forward-looking statements involve risks and uncertainties, which
may cause actual results to differ materially from those statements. Those risks
and uncertainties include, but are not limited to, changing market conditions,
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, and other
risks detailed from time-to-time in the Company's ongoing quarterly filings,
annual information form, annual reports and 20-F filings.

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

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