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<S>                                         <C>                                          <C>
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 ANNOUNCES NEW CLINICAL TRIAL OF
             GTI-2040 IN ACUTE MYELOID LEUKEMIA IN SPONSORSHIP WITH
                       THE U.S. NATIONAL CANCER INSTITUTE

               - Expanding the clinical development of GTI-2040 -

TSE:      LOR
OTC BB:   LORFF

TORONTO, CANADA, JULY 7, 2003 - Lorus Therapeutics Inc. ("Lorus") today
announced the United States Food and Drug Administration's approval of the
National Cancer Institute (NCI) sponsored Investigational New Drug (IND)
application for a clinical trial of its lead antisense drug, GTI-2040 in
combination with cytarabine, in patients with refractory or relapsed acute
myeloid leukemia (AML). Cytarabine is the current established drug for treating
AML patients.

The new study will be part of a Phase II clinical program to be conducted under
the sponsorship of the Division of Cancer Treatment and Diagnosis of the NCI
pursuant to a clinical trials agreement between Lorus and the NCI.

The principal investigator, Dr. Guido Marcucci at Ohio State University Medical
Center in Columbus, Ohio, selected GTI-2040 for this indication based on
positive Phase I clinical data and preclinical data that demonstrated
significant anti-tumor activity with GTI-2040 for a wide range of tumors,
including lymphoma and leukemia. Of particular interest is the potential
complementary mechanism of action of GTI-2040 when combined with cytarabine.

                                     (more)

                                    2

GTI-2040 targets the R2 component of ribonucleotide reductase, a novel malignant
determinant that can cooperate with a variety of cancer causing genes, known as
oncogenes, to enhance cancer transformation and malignant potential. R2 is an
essential component for the process that supplies deoxyribonucleotides for DNA
synthesis and cell division. Down regulation of R2 should lead to a reduced
supply of deoxyribonucleotides to tumor cells, and a dramatic inhibition of
tumor growth.

Cytarabine, a nucleoside with anti-tumor activity, inhibits DNA polymerases that
are important for DNA synthesis and repair. This cytarabine-mediated inhibition
would likely increase with inhibition or downregulation of R2, and additionally
DNA polymerase inhibition could potentiate the anti-tumor activity of GTI-2040.

AML is one of the most common types of leukemia in the western hemisphere, and
even of those patients successfully treated with current therapies, 50 to 80 per
cent experience relapse of their cancer. The development of novel targeted
combination therapies is an important concept to cancer treatment strategies,
and it is believed that this approach is crucial for developing effective new
therapeutic treatments for diseases like AML.

"GTI-2040 is currently in a Phase II clinical trial for the treatment of renal
(kidney) cell carcinoma in combination with capecitabine," said Dr. Jim Wright,
chief executive officer, Lorus. "To now advance this drug into an NCI sponsored
clinical trial for AML is a significant accomplishment for expanding the
development of GTI-2040. AML is one of six indications prioritized by the NCI
for further clinical development with Lorus' GTI-2040, and we look forward to
the results of this very promising clinical investigation of a potentially new
treatment for AML."

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
                                       3

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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