GTx, Inc. Collaborates with diaDexus, Inc to Develop a Diagnostic Test for High Grade PIN

MEMPHIS, Tenn., June 15, 2004—GTx, Inc., (Nasdaq: GTXI) a biopharmaceutical company dedicated to the discovery, development and commercialization of therapeutics primarily related to the treatment of serious men's health conditions, announced today that it has entered into a collaboration with diaDexus, Inc. Under the terms of the agreement GTx will provide clinical samples from its now completed Phase IIb clinical trial program which evaluated ACAPODENE™ (toremifene citrate) tablets for the reduction in the incidence of prostate cancer in men with high grade prostatic intraepithelial neoplasia (PIN), a premalignant lesion that has the potential to progress to prostate cancer. ACAPODENE™ is a nonsteroidal SERM (selective estrogen receptor modulator) that appears to block the estrogen's unwanted actions on the prostate. Information resulting from this collaboration will be evaluated for use by diaDexus for the potential purpose of developing a commercial assay or test from blood or urine to detect high grade PIN and/or prostate cancer.

"High grade PIN identifies patients who are at high risk for developing prostate cancer," stated Mitchell Steiner, M.D., CEO of GTx. "The development of assays for the accurate detection of high grade PIN could be a component in the recognition and treatment of this disease. Together with diaDexus, one of the first companies to recognize the potential of genomics to generate valuable diagnostics tests, we have the opportunity to develop products that could have a significant impact in the prevention of prostate cancer."

"We are pleased to collaborate with GTx to evaluate the potential of our novel biomarkers in detecting high grade PIN and/or prostate cancer," said Patrick Plewman, CEO of diaDexus.

About high grade PIN
High grade PIN has been established as a premalignant lesion of the prostate that has a high potential to progress to invasive prostate cancer. There are approximately 7 million men in the United States in their 40s and 50s who harbor high grade PIN. These men are thought to be at greater risk for developing prostate cancer within ten years. Unfortunately, today high grade PIN diagnosis is only detected when men are biopsied. We believe there is great need for diagnostic blood marker. This year in the United States, approximately 1,300,000 prostate biopsies will be performed to detect over 230,000 new cases of prostate cancer. High grade PIN is found in an average of 9% of prostate biopsies which represents an estimated 115,000 new cases of high grade PIN diagnosed each year. Patients who are found to have high grade PIN are at high risk of prostate cancer with up to 37% of patients being later diagnosed with prostate cancer within 1 year.

High grade PIN clinical development overview
GTx recently completed a Phase IIb clinical trial to evaluate its lead product ACAPODENE™ for the prevention of prostate cancer in high risk men. The placebo patients had a 31.2% accumulated rate of prostate cancer and a 20% reduction was seen in the accumulated rate of prostate cancer incidence for patients taking ACAPODENE™ 20mg. There was a 46% reduction in prostate cancer incidence for those men who were on ACAPODENE™ 20mg for the entire year. The placebo patients and the treated patients had similar Gleason grades indicating that ACAPODENE™ is not selecting out more aggressive tumors. ACAPODENE™ was well tolerated in all treated groups.

About ACAPODENE™
Toremifene is a nonsteroidal SERM, a small molecule that binds and selectively modulates the estrogen receptor. SERMs have been shown to block estrogen receptors in the prostate. GTx has licensed the right to develop, market and distribute toremifene citrate, the active ingredient of ACAPODENE™ tablets, worldwide in the field of prevention and treatment of prostate cancer from Orion Corporation, Finland.

About Prostate Cancer
In the United States, there is estimated to be over 230,000 new prostate cancer cases and 30,000 prostate cancer deaths this year. This makes prostate cancer the most commonly diagnosed cancer and the second leading cause of cancer-related deaths in men in the United States.

About GTx
GTx is a biopharmaceutical company dedicated to the discovery, development and commercialization of therapeutics primarily related to the treatment of serious men's health conditions. GTx's drug discovery and development programs are focused on small molecules that selectively modulate the effects of estrogens and androgens. GTx currently has two product candidates that are in human clinical trials. The company is developing ACAPODENE», its most advanced product candidate, through clinical trials for two separate indications: (1) its now completed Phase IIb clinical trial for the reduction in the incidence of prostate cancer in high risk men with precancerous prostate lesions and planned initiation of a Phase III clinical trial (2) a pivotal Phase III clinical trial for the treatment of serious side effects of advanced prostate cancer therapy. GTx is developing its second product candidate, andarine, and other specified backup compounds, with its partner, Ortho Biotech Products, L.P., a subsidiary of Johnson & Johnson. It is currently anticipated that andarine will be entering a planned Phase II clinical trial later this year. GTx retains all rights to the discovery, development, and commercialization of the rest of its SARM program including its other specific product candidates ostarine, prostarine and andromustine.

Forward Looking Statement
This press release contains forward-looking statements, including, without limitation, statements related to GTx's current and anticipated clinical trials and research and development programs. These forward-looking statements are based upon GTx's current expectations. Forward-looking statements involve risks and uncertainties. GTx's actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks that neither GTx nor its partner will be able to commercialize its product candidates if preclinical studies do not produce successful results or clinical trials do not demonstrate safety and efficacy in humans; if third parties do not manufacture the Company's product candidates in sufficient quantities and at an acceptable cost, clinical development and commercialization of its product candidates would be delayed; use of third-party manufacturers may increase the risk that the Company will not have adequate supplies of its product candidates; if third parties on whom the Company relies do not perform as contractually required or expected, the Company may not be able to obtain regulatory approval for or commercialize its product candidates; the Company is dependent upon collaborative arrangements to complete the development and commercialization of some of its product candidates, and these collaborative arrangements may place the development of its product candidates outside its control, may require it to relinquish important rights or may otherwise be on terms unfavorable to the Company; and if the Company is not able to obtain required regulatory approvals, the Company will not be able to commercialize its product candidates. The annual report filed on Form 10-K with the U.S. Securities and Exchange Commission on March 26, 2004 contains under the heading "Additional Factors That Might Affect Future Results" a more comprehensive description of these and other risks to which GTx is subject. GTx expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in its expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.