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Cell Therapeutics Initiates Phase I/II Study of CT-2106

20/04/2004

Second Polyglutamate Drug Candidate, to Advance to Mid-Stage Clinical Testing Phase I results further demonstrate potential of polyglutamate technology to reduce toxicity of commonly used cancer drugs

April 20, 2004 Seattle—Cell Therapeutics, Inc. (CTI) (NASDAQ: CTIC) announced that it has initiated an international phase I/II clinical trial of the novel polyglutamate-20S-camptothecin conjugate (CT-2106) in colorectal cancer patients. The open label study combines CT-2106 with infusional 5 fluorouracil/folinic acid (5-FU/FA) in patients with metastatic colorectal cancer who have failed front-line therapy with oxaliplatinum. The first stage of the study will determine the maximum tolerated dose (MTD) of this combination, as well as, the dose limiting toxicities, safety profile, and anti-tumor activity. Once the MTD has been determined, the study will progress to a second stage where CTI will evaluate the efficacy of the drug. A total of approximately 45 patients will be treated on the study.

“The preliminary phase I trial results of CT-2106 in advanced solid tumors provide a strong indication that the product may have the ability to substantially improve the toxicity profile of standard camptothecin as we observed that typical side effects, such as gastrointestinal and bladder toxicities, were notably absent,” stated Jack W. Singer, M.D., Chief Medical Officer of CTI. “Moreover, the results showed that CT-2106 retained the potent anti-tumor activity of this class of agents.”

Camptothecins are one of the world's fastest growing classes of anti-cancer agents and are commonly used as treatment for colorectal, lung and ovarian cancer, however they are limited by severe side effects. The naturally occurring product, 20S-camptothecin is among the most potent compounds in this class of agents and was evaluated in phase I and II trials by the National Cancer Institute (NCI), but its development was discontinued due severe gastrointestinal and bladder toxicities which have not been seen with CT-2106 in phase I studies.

“To date, a total of 28 patients have been treated with CT-2106. The safety, pharmacokinetic and efficacy data from the phase I study will be presented at this year’s ASCO meeting,” said Singer. “Preliminary results have prompted our investment in advancing a broader phase II program in tumor types where camptothecins are known to be active, either alone or in combination with other agents. In addition to colorectal cancer, we plan to initiate international studies in small cell lung cancer and advanced ovarian cancer.”

CT-2106 is the second agent in CTI’s portfolio, after XYOTAX™ (paclitaxel poliglumex), to exploit the polyglutamate-conjugate technology, where an anti-cancer agent is conjugated to a naturally biodegradable poly-amino acid. The clinical experience with XYOTAX, which is completing enrollment in multiple phase III trials for non-small cell lung cancer, further confirms our preclinical work, which has shown that the polyglutamate technology has the ability to eliminate the need for toxic solubilizing agents and decrease the amount of drug exposure in normal tissues while increasing the amount of drug reaching tumor tissues.

About Cell Therapeutics, Inc. Based in Seattle, CTI is a biopharmaceutical company committed to developing an integrated portfolio of oncology products aimed at making cancer more treatable.

This announcement includes forward-looking statements that involve a number of risks and uncertainties, the outcome of which could materially and/or adversely affect actual future results. Specifically, the risks and uncertainties that could affect the development of CT-2106 include risks associated with preclinical and clinical developments in the biopharmaceutical industry in general and with CT-2106 in particular including, without limitation, the potential failure of CT-2106 to prove safe and effective for treatment of colorectal cancer, determinations by regulatory, patent and administrative governmental authorities, competitive factors, technological developments, costs of developing, producing and selling CT-2106, and the risk factors listed or described from time to time in the Company’s filings with the Securities and Exchange Commission including, without limitation, the Company’s most recent filings on Forms 10-K, 8-K, S-3, S-4, and 10-Q.

For further information please contact:

Investors Cell Therapeutics, Inc. Leah Grant T:206.282.7100F:206.272.4010
E:invest@ctiseattle.com www.cticseattle.comCell Therapeutics, Inc.

Candice Douglass T:206.272.4472 F:206.272.4010 E:media@ctiseattle.com Cell Therapeutics, Inc. (Europe)Karl Hanks T:39 026 103 5807 F:39 026 103 5601 E:karl.hanks@ctimilano.com>