Xcyte Therapies, Inc. Presents Results of Two Clinical Trials of Xcellerated T Cells at Tandem BMT Meetings.

SEATTLE -- Xcyte Therapies, Inc. ("Xcyte") (Nasdaq:XCYT) announced today that results from two clinical trials of Xcellerated T Cells were presented at the 2005 Tandem BMT Meetings, the combined annual meeting of the American Society for Blood and Marrow Transplantation and the Center for International Blood & Marrow Transplant Research, which was held in Keystone, Colorado. Dr. John DiPersio, Chief, Division of Oncology, Washington University School of Medicine, presented data from a Phase I/II study of Xcellerated T Cells after autologous peripheral blood stem cell transplantation in patients with multiple myeloma. Dr. Ron Berenson, President and Chief Executive Officer of Xcyte Therapies, presented preliminary results from a Phase II study of Xcellerated T Cells in patients with relapsed or refractory indolent non-Hodgkin's lymphoma (NHL).

In the Phase I/II clinical trial in multiple myeloma, 36 patients were treated with a single infusion of Xcellerated T Cells three days following high-dose chemotherapy and autologous stem cell transplantation. Recovery of lymphocytes and T cells was much more rapid than previously seen in patients treated with the same therapeutic regimen without receiving Xcellerated T Cells. Response data are available for 35 patients, with a median follow-up of 13 months (range 7-23). Thirty-one (89%) patients had a significant tumor response, as measured by a 50% or greater decrease in the serum M-protein, a standard biological marker for multiple myeloma. A 90% or greater decrease in the serum M-protein was seen in 21 (60%) of the patients, including 3 patients with complete disappearance of the marker. Progression-free survival was 67% at one year and 58% at two years by Kaplan-Meier analysis. Thirty-four of the 36 treated patients are currently alive.

In the Phase II clinical trial in NHL, 27 of a planned 40 patients with small lymphocytic (n=9), mantle cell (n=5), marginal zone (n=2) and follicular cell (n=11) lymphoma have been enrolled. Patients received two infusions of Xcellerated T Cells separated by 6-8 weeks. The infusions were well tolerated and no serious adverse events related to therapy were reported in the 11 patients for whom data are available. Sustained increases in T cell counts were observed in treated patients. Early response results are available for 16 patients, 11 after one infusion and 5 after two infusions of Xcellerated T Cells. One patient had an unconfirmed complete response pending a bone marrow biopsy, 13 patients had stable disease, including two minor responses, and 2 patients had progressive disease.

"In both of these trials, the infusion of Xcellerated T Cells was well-tolerated and resulted in significant increases in circulating lymphocytes in general and T cells in particular," noted Dr. Berenson. "In the multiple myeloma trial, we remain encouraged by the number of patients who achieved a 90% or greater reduction in serum M-protein with the combination of high-dose chemotherapy, stem cell transplantation and Xcellerated T Cells, and by their progression-free survival. These results compare favorably to similar treatment without Xcellerated T Cells. However, long term follow-up is needed before we can determine our future plans in this indication. We are also encouraged by the very early results in the NHL trial, which enrolled patients with extensive prior treatment. However, only a few of these patients have completed both infusions, and more follow-up will be required to determine the significance of these findings."

Note: Certain of the statements made in this press release are forward-looking, such as those, among others, relating to the therapeutic potential of Xcellerated T Cells. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Factors that may cause such a difference include risks related to adverse clinical results as our product candidates move into and advance in clinical trials, risks inherent in early-stage development and failure by Xcyte Therapies to secure or maintain relationships with collaborators. Results obtained in early stage clinical trials may not be predictive of results obtained in larger trials intended to demonstrate the safety and efficacy of Xcellerated T Cells. More information about the risks and uncertainties faced by Xcyte Therapies is contained in our filings with the Securities and Exchange Commission. Xcyte Therapies disclaims any intention or obligation to update or revise any forward-looking statement, whether as a result of new information, future events or otherwise.

Xcyte Therapies, Inc. is a biotechnology company developing a new class of therapeutic products designed to enhance the body's natural immune responses to treat cancer, infectious diseases and other medical conditions associated with weakened immune systems. Xcyte derives its therapeutic products from a patient's own T cells, which are cells of the immune system that orchestrate immune responses and can detect and eliminate cancer cells and infected cells in the body. Xcyte uses its patented and proprietary Xcellerate(TM) Technology to generate activated T cells, called Xcellerated T Cells(TM), from blood that is collected from the patient. Activated T cells are T cells that have been stimulated to carry out immune functions. The Xcellerate(TM) Technology is designed to rapidly activate and expand the number of the patient's T cells outside of the body. Xcyte is currently conducting clinical trials of Xcellerated T Cells(TM) in patients with chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and multiple myeloma.

Xcyte(TM), Xcyte Therapies(TM), Xcellerate(TM) and Xcellerated T Cells(TM) are trademarks of Xcyte Therapies, Inc.