TRISENOX® Highly Active in Refractory Multiple Myeloma

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TRISENOX® Highly Active in Refractory Multiple Myeloma Patients When Combined with Vitamin C and Melphalan Multiple patient case history reviews form the basis for a phase II trial of the combination known as the MAC (Melphalan, Arsenic trioxide, vitamin C) regimen

June 3, 2003 Chicago—Cell Therapeutics, Inc. (CTI) (NASDAQ:CTIC), the marketer of TRISENOX® (arsenic trioxide) injection, reported data presented at this year’s meeting of the American Society of Clinical Oncology (ASCO). Results of a case study review of seven refractory multiple myeloma patients treated with a combination of TRISENOX®, vitamin C and melphalan demonstrated that all of the patients achieved an objective response, ranging from 29 to 85 percent reduction in M-protein, with four of seven patients (57 percent) remaining free of cancer progression for a median of 34 weeks.

Two of the seven patients (29 percent) in the study had failed stem cell transplant, five (71 percent) had failed thalidomide treatment, and three (43 percent) had failed bortezomib prior to receiving the MAC regimen. All seven patients responded to therapy, with one patient achieving a near complete response (85 percent reduction in M-protein). MAC therapy resulted in a marked improvement in renal function in four out of four patients with myeloma kidney damage, two of whom were close to requiring dialysis. Responses lasted between 17 and 48 weeks.

"The high rate of response to this TRISENOX®-based MAC regimen in patients with drug-resistant multiple myeloma is very encouraging,” noted James R. Berenson, M.D., Director, Myeloma and Bone Metastasis Program at Cedars-Sinai Medical Center, who presented the encouraging results. “These results have prompted the development of a phase II, multicenter trial testing MAC therapy in 100 patients at 15 sites throughout the United States.”

Treatment Approach/Tolerability TRISENOX®, melphalan, and vitamin C was administered for 17 to 48 weeks to seven patients with advanced relapsed/refractory multiple myeloma, four who had significant kidney impairment from their disease. MAC was very well tolerated with only reversible mild cytopenias and fluid retention reported.

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About TRISENOX® TRISENOX® (arsenic trioxide) is marketed by Cell Therapeutics, Inc. (CTI) (NASDAQ: CTIC). TRISENOX® was approved for marketing in 2000 by the U.S. Food and Drug Administration to treat patients with relapsed or refractory Acute Promyelocytic Leukemia. (APL), a rare, life- threatening cancer of the blood. TRISENOX® was granted marketing authorization from the European Commission in March 2002. APL, one of eight subtypes of acute myeloid leukemia (AML), represents 10–15 percent of the more than 20,000 patients diagnosed with AML each year. TRISENOX® is currently being studied in more than 40 clinical trials in a variety of cancers.

U.S. marketing approval for TRISENOX® was granted based on results from a U.S. multicenter study in which 40 relapsed APL patients were treated with TRISENOX® 0.15 mg/kg until bone marrow remission or a maximum of 60 days. Thirty-four patients (85 percent) achieved CR. When the results for these 40 patients were combined with those for the 12 patients in a pilot trial, an overall response rate of 87 percent was observed.

WARNING: TRISENOX® should be administered under the supervision of a physician who is experienced in the management of patients with acute leukemia. Some patients with acute promyelocytic leukemia (APL) treated with TRISENOX® have experienced APL differentiation syndrome – with symptoms similar to retinoic acid-acute promyelocytic leukemia (RA-APL) syndrome. Arsenic trioxide can cause QT prolongation (which can lead to torsade de pointes) and complete atrioventricular block.

The most common adverse events associated with TRISENOX® have been generally manageable, reversible and usually did not require interruption of therapy. These have included hypokalemia, hypermagnesemia, hyperglycemia and thrombocytopenia as reported in 13 percent of the patients (n=40). Abdominal pain, dyspnea, hypoxia, bone pain and neutropenia were reported in 10 percent of these patients, while arthralgia, febrile neutropenia and disseminated intravascular coagulation were reported in eight percent of patients.

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. For additional information, please visit www.cticseattle.com.

This announcement includes forward-looking statements about preliminary data from clinical trials 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 continued development of TRISENOX® include risks associated with preclinical and clinical developments in the biopharmaceutical industry in general and with TRISENOX® in particular including, without limitation, the potential failure of TRISENOX® to prove safe and effective for treatment of multiple myeloma, determinations by regulatory, patent and administrative governmental authorities, competitive factors, technological developments, costs of developing, producing and selling TRISENOX®, 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 and 10-Q. www.cticseattle.com Page 3 of 3 TRISENOX in MM

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For further information please contact: Investors Media Cell Therapeutics, Inc. Cell Therapeutics, Inc. Leah Grant Candice Douglass T: 206.282.7100 F: 206.272.4010 T: 206.272.4472 F: 206.272.4010 E: [email protected] E: [email protected]