RSR13 Clinical Trials Underway

Allos Begins Phase 3 Study of RSR13 in Women with Brain Metastases from Breast Cancer

February 12, 2004


-- Study Concurrent With New Drug Application Review --

-- National Breast Cancer Coalition Supports Trial Through its Clinical Trials Initiative --

WESTMINSTER, Colo., February 12, 2004 – Allos Therapeutics, Inc. (Nasdaq: ALTH) today announced that it has launched a multi-center Phase 3 randomized open label trial of RSR13 (efaproxiral) as an adjunct to whole brain radiation therapy for the treatment of brain metastases from breast cancer. The study will seek to enroll approximately 360 patients at up to 50 cancer centers across North America. The management of Allos Therapeutics will be available to discuss this announcement during its fourth quarter and year-end financial results conference call at 11 a.m. EST today.

On February 2, 2004 the U.S. Food and Drug Administration (FDA) accepted for priority review the company’s New Drug Application (NDA) to market RSR13 as an adjunct to whole brain radiation therapy for the treatment of brain metastases from breast cancer. The FDA has established a target date of June 4, 2004 to take action on the NDA.

"We are committed to expanding the body of clinical data in support of RSR13 and believe it is prudent to launch this study now, even as the FDA reviews our NDA on a priority basis,� said Michael E. Hart, President and CEO of Allos Therapeutics, Inc. “Our findings to date suggest that RSR13, when combined with whole brain radiation therapy, is an important advance in the treatment of patients with brain metastases for whom there are few therapeutic options.“

The Phase 3 study, called ENRICH (ENhancing Whole Brain Radiation Therapy In Patients with Breast Cancer and Hypoxic Brain Metastases), is designed to compare the effect of WBRT with supplemental oxygen with or without RSR13 in women with brain metastases from breast cancer. This trial will also evaluate the safety profile of RSR13 in this patient population. The design of the study calls for two interim analyses for safety and efficacy. The company has successfully completed the Special Protocol Assessment (SPA) of the ENRICH trial. Under SPA, the FDA evaluates whether the protocol for a clinical trial is adequate to meet scientific and regulatory requirements for marketing approval of the drug by the FDA.

The National Breast Cancer Coalition (NBCC) is partnering with Allos to support trial enrollment and to gain additional insight about how to improve radiation treatment for women with brain metastases from breast cancer. Through its Clinical Trials Initiative, the NBCC is mobilizing its nation-wide network of advocates to inform women about this trial. “The National Breast Cancer Coalition has long said that clinical trials which ask the right questions are absolutely necessary to arrive at the best treatments and to end breast cancer,� commented Fran Visco, President of NBCC. “We believe the ENRICH study will answer important questions, and we are committed to working with Allos to help with oversight and enrollment of patients for the trial.�

NBCC is made up of more than 600 organizations representing several million patients, professionals, families and friends. Its main goals are to increase federal funding for breast cancer research and collaborate with the scientific community to implement new models of research; improve access to high quality health care and breast cancer clinical trials for all women; and expand the influence of breast cancer advocates in all aspects of the breast cancer decision making process. Additional information about NBCC can be found at www.stopbreastcancer.org.

About RSR13

RSR13 is the first synthetic small molecule designed to “sensitize� hypoxic (oxygen-deprived) areas of tumors prior to radiation therapy by facilitating the release of oxygen from hemoglobin, the oxygen-carrying protein contained within red blood cells, and increasing the level of oxygen in tumors. The presence of oxygen in tumors is an essential element for the effectiveness of radiation therapy in the treatment of cancer. By increasing tumor oxygenation at the time of treatment, RSR13 has the potential to enhance the efficacy of standard radiation therapy. Unlike chemotherapeutics or other radiation sensitizers, RSR13 does not have to cross the blood brain barrier or enter the tumor to be effective.

Conference Call


Allos Therapeutics will host a conference call to review the company’s fourth quarter 2003 results at 11:00 a.m. EST on Thursday, February 12, 2004. The dial in number for U.S. residents to participate is 800-915-4836. International callers should dial +1-973-317-5319.


Conference Call Replay

An audio replay of the conference call will be available from 1:00 p.m. EST, February 12, 2004 until midnight February 19, 2004. To access the replay, please dial 1-800-428-6051 (US/Canada); international +1-973-709-2089; the conference ID number is 335884.


Webcast


Allos Therapeutics will hold a live webcast of the conference call. The webcast will be available from the homepage and the investor relations section of the company’s web site at www.allos.com and will be archived for 30 days.
About Allos Therapeutics, Inc.

Allos Therapeutics, Inc. is a biopharmaceutical company focused on developing and commercializing innovative drugs for improving cancer treatments. The company’s lead clinical candidate, RSR13, is a synthetic small molecule that has the potential to sensitize hypoxic (oxygen deprived) tumor tissues and enhance the efficacy of standard radiation therapy. In addition, Allos is developing PDX, an injectable small molecule chemotherapeutic agent that has a superior potency and toxicity profile relative to methotrexate and other dihydrofolate reductase, or DHFR, inhibitors. For more information, please visit the company’s web site at: www.allos.com.

This announcement contains forward-looking statements that involve risks and uncertainties. Future events may differ materially from those discussed herein due to a number of factors, including, but not limited to, risks and uncertainties related to the company’s ability to successfully complete its Phase 3 clinical trial on schedule and in accordance with regulatory requirements, adequately demonstrate the safety and efficacy of RSR13 for the treatment of brain metastases or any other type of cancer, and obtain regulatory approval for RSR13 for the treatment of brain metastases from breast cancer in the United States or any other jurisdiction, as well as other risks and uncertainties detailed from time to time in the company's SEC filings, including its Annual Report on Form 10-K for the year ended December 31, 2002, as amended. All forward-looking statements are based on information currently available to the company on the date hereof, and the company assumes no responsibility to update such statements.

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Contacts:

Monique M. Greer
VP, Corporate Communications and Investor Relations
720-540-5241
mgreer@allos.com

Lazar Partners Limited (media)
Fern Lazar
212-867-1762
flazar@lazarpartners.com








Contact: Monique Greer