-Novel drug combination enters clinical trial -

    TSX:    LOR
    AMEX:   LRP

    TORONTO, May 4 /PRNewswire-FirstCall/ - Lorus Therapeutics Inc. ("Lorus")
announced today the initiation of a clinical trial of GTI-2040 in a novel
combination with oxaliplatin and capecitabine in patients with advanced
unresectable colon cancer.
    This new study is under the direction of Dr. Stephen Shibata at the City
of Hope Comprehensive Cancer Center in Duarte California, together with Dr.
Heinz-Joseph Lenz at the University of Southern California in Los Angeles, Dr.
David Gandara at the Davis Cancer Center, University of California in
Sacramento and Dr. Mark McNamara at the City of Hope Medical Group in
Pasadena.
    A key objective of this clinical study is to establish the optimal dose
of this combination in colon cancer patients and the pharmacodynamic effects
on cellular markers of anti-tumor activity when these agents are combined.
    This trial is one of six clinical studies in a Phase II clinical program
for GTI-2040 in combination with other agents and in various tumor types
sponsored by the Cancer Therapy Evaluation Program (CTEP), a U.S. National
Cancer Institute program that sponsors clinical trials of novel compounds to
accelerate their development.
    "We are delighted with the support of the CTEP program to extend GTI-2040
development to colon cancer," said Dr. Jim Wright, CEO of Lorus Therapeutics
Inc. "Overlapping toxicities with common chemotherapy combinations can be a
limiting factor in treating advanced diseases where single-agent therapy is
rarely an option. GTI-2040 has good tolerability alone and in combination with
other drugs in clinical studies to date, which makes it an encouraging
opportunity for colon cancer therapy."
    In preclinical studies, GTI-2040 has demonstrated reduction in the size
of human adenocarcinoma tumors of the colon by 80 per cent when injected into
mice compared to those in untreated mice using the standard mouse xenograft
model. It has also demonstrated a broad spectrum of activity in vivo in
preclinical models across many tumor types, and a 65 per cent to 95 per cent
inhibition of lung metastases in two animal models.
    In similar animal models, when combined with 5-FU (the active metabolite
of capecitabine) or oxaliplatin, GTI-2040 has shown increased antitumor
activity compared to either agent alone.
    American Cancer Society data identifies colon cancer as the third most
common cancer in both men and women with an estimated 106,370 new cases and
56,730 deaths expected to occur in 2004. While advances have come from earlier
diagnosis, patients with metastatic colon cancer have achieved only modest
improvement from advances in combination chemotherapies, which illustrates the
need for new therapeutic combination strategies involving multiple targeted
therapies.
    GTI-2040 targets the R2 component of ribonucleotide reductase (RR), which
is required for DNA synthesis, and is elevated in a wide range of tumor types
where it may act as a signal molecule to enhance malignancy. It is predicted
in this study that the mechanisms of cytotoxicity of capecitabine and of
oxaliplatin, including inhibition of DNA repair, will be enhanced by this RR
blockade in these colon cancer patients.
    The chemotherapies combined with GTI-2040 in this trial, capecitabine and
oxaliplatin, are FDA approved therapies for colon cancer, the former for
first-line therapy and the latter in combination with
5-fluorouracil/Leucovorin.

    About GTI-2040
    GTI-2040 is a drug that specifically targets the R2 component of
ribonucleotide reductase, which is required for DNA synthesis and cell
proliferation. R2 has also been described as a malignant determinant that is
elevated in a wide range of tumors, and through deregulation can cooperate
with a variety of cellular cancer causing genes known as oncogenes to enhance
tumor growth and metastatic potential. GTI-2040 showed significant antitumor
activity against many different human tumors in preclinical studies. In
addition to a clinical trial in renal cell cancer, GTI-2040 is currently the
subject of a Clinical Trial Agreement with the United States National Cancer
Institute (NCI) under which GTI-2040 will be tested in combination
chemotherapy in six different clinical trials. Five of these trials have now
been initiated including treatment of metastatic breast cancer at the
University of California, Davis Cancer Center; acute myeloid leukemia at the
Ohio State University Medical Center, non-small cell lung cancer at Princess
Margaret Hospital in Toronto, Ontario, a variety of solid tumors at the
Institute of Drug development, Cancer Therapy and Research Center in San
Antonio, Texas and the colon cancer clinical study announced today. The
remaining clinical trial to be initiated with NCI sponsorship will investigate
GTI-2040 in prostate cancer.

    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 acquisition and
in-licensing program, Lorus is building a portfolio of promising anticancer
drugs. Late-stage clinical development and marketing may be done in
cooperation with strategic pharmaceutical partners. Lorus currently has three
products in human clinical trials with a pipeline of seven clinical trials in
phase II clinical trial programs and one phase III registration clinical
trial. Lorus Therapeutics Inc. is a public company listed on the Toronto Stock
Exchange under the symbol LOR, and on the American Stock Exchange under the
symbol LRP.

    Forward Looking Statements
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forward-looking statements, which reflect the Company's current expectation
and assumptions, and are subject to a number of risks and uncertainties that
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studies, the establishment of corporate alliances, the impact of competitive
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regulatory approval process, product development delays, the Company's ability
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research, operations and marketing and other risks detailed from time-to-time
in the Company's ongoing quarterly filings, annual information form, annual
reports and 40-F filings. We undertake no obligation to publicly update or
revise any forward looking statements, whether as a result of new information,
future events or otherwise.
    Lorus Therapeutics Inc.'s press releases are available through the
Company's Internet site: http://www.lorusthera.com.

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