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SEATTLE--([ BUSINESS WIRE ])--May 16, 2012--Dendreon Corporation (NASDAQ:[ DNDN ]) today announced the following PROVENGE (sipuleucel-T) data will be presented at the American Society of Clinical Oncology (ASCO) Annual Meeting American Society of Clinical Oncology (ASCO) Annual Meeting taking place June 1-5, 2012 in Chicago, Illinois.

"This analysis of prostate tissue from patients participating in the Phase 2 NeoACT trial demonstrated increased T-cells at the rims of prostate cancer tumors, which supports an immune-mediated mechanism of action for PROVENGE"

• aOverall Survival (OS) Benefit with Sipuleucel-T by Baseline PSA; An Exploratory Analysis from the Phase 3 IMPACT Trial,a abstract #4684. General Poster Session, Genitourinary Cancer from 8:00 a.m. to 12:00 p.m. CT on Sunday, June 3, 2012.
• aEvaluation of Immune Activation Following Neoadjuvant Sipuleucel-T in Subjects with Localized Prostate Cancer,a abstract #2563. General Poster Session, Genitourinary Cancer from 8:00 a.m. to 12:00 p.m. CT on Monday, June 4, 2012.
• aNeoadjuvant Sipuleucel-T in Localized Prostate Cancer: Effects on Immune Cells within the Prostate Tumor Microenvironment,a abstract #2564. General Poster Session, Genitourinary Cancer from 8:00 a.m. to 12:00 p.m. CT on Monday, June 4, 2012.
• aCorrelation of Increased Eosinophil Count Following Sipuleucel-T Treatmentwith Outcome in Patients (pts) with Metastatic Castrate-Resistant Prostate Cancer (mCRPC),a abstract #4650. General Poster Session, Genitourinary Cancer from 8:00 a.m. to 12:00 p.m. CT on Sunday, June 3, 2012.

aThese data presented at ASCO continue to support the overall survival benefit of PROVENGE and its mechanism of action,a said Mark Frohlich, MD, executive vice president and chief medical officer.

Abstract #4684: Overall Survival (OS) Benefit with Sipuleucel-T by Baseline PSA; An Exploratory Analysis From the Phase 3 IMPACT Trial

In the pivotal Phase 3 IMPACT trial, a pre-specified subgroup analysis for baseline prognostic variables showed treatment effects consistently favoring PROVENGE. For patients whose baseline PSA was below the median PSA level, PROVENGE trended to demonstrate a greater treatment effect (HR=0.685 vs. 0.865). In this most recent sub analysis, researchers further sub-divided baseline PSA into quartiles to evaluate potential treatment effect patterns. This exploratory analysis included all randomized patients from the IMPACT study (n=512). Patients were categorized by baseline PSA quartile, ECOG PS, and by median for other baseline prognostic variables (i.e., LDH, PAP, ALP in bone-only disease, and hemoglobin [Hgb]). Median overall survival and hazard ratio were estimated using Kaplan-Meier and Cox models, respectively.

Results showed that an increasing baseline PSA quartile was associated with markers of advanced disease. A consistent treatment effect was seen in all subsets and there was a trend toward an increased magnitude of treatment benefit in patients with a lower baseline PSA. Results for other baseline prognostic variables also suggested a trend toward greater benefit in subjects with better prognostic features. However, results for baseline Hgb indicated an opposite trend.

aThe results of this analysis, although not adequately powered for significance, support an overall survival benefit with PROVENGE across PSA quartiles,a said Gerald Chodak, MD, Midwest Prostate and Urology Health Center, Weiss Memorial Hospital. aThe trend in greater magnitude of benefit in patients with lower baseline PSA suggests that patients with less advanced disease may benefit more from treatment with PROVENGE, and supports the use of PROVENGE early in the natural history of men with asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer.a

Abstract #2563: Evaluation of Immune Activation Following Neoadjuvant Sipuleucel-T in Subjects with Localized Prostate Cancer

In this open-label, Phase 2 NeoACT (NEOadjuvant Active Cellular immunoTherapy) study, patients with localized prostate cancer received three infusions of PROVENGE at approximately two-week intervals, beginning six to seven weeks prior to radical prostatectomy. PROVENGE is not currently indicated for neoadjuvant treatment of localized prostate cancer. Following radical prostatectomy, subjects were randomized 1:1 to receive / not receive a PROVENGE booster infusion 12 weeks post-radical prostatectomy. Cellular composition, antigen presenting cell (APC) activation, cytokines, and T and B cell activation were profiled before and after each culture with PA2024, the fusion protein containing prostatic acid phosphatase used to generate PROVENGE.

Of the 42 enrolled study patients, 38 received all three infusions of PROVENGE, and 15 patients received a booster infusion. Consistent with PROVENGE in mCRPC, CD54 upregulation (APC activation) was greater at the second and third infusions relative to the first (P<0.001). The expression of early T cell activation markers (CD134, CD137, CD278 and CD279) were increased in pre-culture cells obtained after the first infusion, and further increased after culture. Activated mature B cells (CD20+CD27+IgD+CD86+) increased following culture in all three products (P<0.01); memory B cells (CD20+CD27+IgD-CD86+) were progressively increased following the first infusion (P<0.05 third vs. first product). TNF-', IFN- were secreted at higher levels during culture of the second and third products (all P<0.001). The observed increases in CD54 upregulation, early T cell activation markers, and memory and activated mature B cells were maintained at booster treatment.

Results from this analysis support further evaluation of PROVENGE in the neoadjuvant setting based on the enhanced immune activity demonstrated in this analysis.

aThese data are exciting because PROVENGE in the neoadjuvant setting also resulted in enhanced immune system activation that was consistent with boosting of an immune response primed with the first infusion,a said Lawrence Fong, MD, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center. aImmune activation was maintained at the booster infusion three months following initial treatment with PROVENGE. Additional studies are warranted to further examine the importance of PROVENGE as a neoadjuvant treatment option for men with localized prostate cancer.a

Abstract #2564: Neoadjuvant Sipuleucel-T in Localized Prostate Cancer: Effects on Immune Cells within the Prostate Tumor Microenvironment

In addition, a second analysis, evaluated treatment with PROVENGE prior to radical prostatectomy in patients with localized prostate cancer. This analysis assessed the presence of lymphocytes by immunohistochemistry (IHC) in radical prostatectomy tissue following treatment with PROVENGE and compared it to prostate biopsy tissue obtained prior to treatment.

At the time of abstract submission, IHC analysis had been completed in 32 patients. Significant increases (>3-fold) in CD3⁺ and CD4⁺ T-cells populations were observed at the tumor rim between the interface of benign and malignant tissue when compared with the pretreatment biopsy tissue (ANOVA post hoc Newman-Keuls test: P<0.0001, both).

aThis analysis of prostate tissue from patients participating in the Phase 2 NeoACT trial demonstrated increased T-cells at the rims of prostate cancer tumors, which supports an immune-mediated mechanism of action for PROVENGE,a said Lawrence Fong, MD, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center.

Abstract #4650: Correlation of Increased Eosinophil Count Following Sipuleucel-T Treatment with Outcome in Patients (pts) with Metastatic Castrate-Resistant Prostate Cancer (mCRPC)

This exploratory analysis assessed the potential correlation between increased eosinophils (white blood cells), and overall survival, prostate cancer-specific survival, and immune response following treatment with PROVENGE. Data from three Phase 3 trials in patients with mCRPC (Studies D9901, D9902A, and IMPACT) were evaluated and the analysis included complete blood counts performed at baseline and at weeks 2-34 following treatment with PROVENGE.

In patients who were treated with PROVENGE, an increase in eosinophil counts were observed by week 6 and decreased to nearly baseline by week 14, while the eosinophil counts in the control arm remained consistent. Of the 377 patients treated with PROVENGE and eligible for analysis, 105 (27.9%) had eosinophilia. Baseline disease characteristics associated with eosinophilia were indicative of better prognosis (i.e., longer Halabi predicted survival [P=0.007], lower PSA [P=0.033], higher Hgb [P<0.001], and no prior docetaxel [P=0.012]). In univariate analyses, eosinophilia correlated with improved overall survival (HR=0.75; 95%CI: 0.56a"1.01; P=0.057) and prostate cancer-specific survival (HR=0.71; 95%CI: 0.53a"0.97; P=0.031). The magnitude of eosinophilia positively correlated with antigen-specific humoral responses (P a0.039 for wks 6, 14 and 26) and elevations in the cytokines at wk 6 (IL2 [P=0.011], IL5 [P=0.038] and TARC [P=0.001]). AEs occurring more frequently (P<0.05) in pts with eosinophilia were infusion-related: pyrexia (33.3 v 21.3%) and nausea (19.0 v 10.7%). No cases of hypereosinophilic syndrome were reported.

The analysis suggests that increases in eosinophils after treatment with PROVENGE correlated with improved overall survival and prostate cancer-specific survival. Larger increases in eosinophil counts were associated with humoral responses and Th2-type cytokine production. The analysis supports further studies to evaluate eosinophilia measurement as a potential biomarker for PROVENGE response.

aThese study findings are interesting and suggest that looking at eosinophil count could give insight into how a patient may respond to treatment with PROVENGE,a said Douglas McNeel, MD, University of Wisconsin, Madison.

PROVENGE Indication and Important Safety Information

PROVENGE is an autologous cellular immunotherapy indicated for the treatment of asymptomatic or minimally symptomatic metastatic castrate resistant (hormone refractory) prostate cancer.

PROVENGE is intended solely for autologous use and is not routinely tested for transmissible infectious diseases.

The safety evaluation of PROVENGE was based on 601 prostate cancer patients in four randomized clinical trials who underwent at least one leukapheresis. The most common adverse events (incidence greater-than or equal to 15%) are chills, fatigue, fever, back pain, nausea, joint ache, and headache. Serious adverse events reported in the PROVENGE group include acute infusion reactions (occurring within 1 day of infusion) and cerebrovascular events. In controlled clinical trials, severe (Grade 3) acute infusion reactions were reported in 3.5% of patients in the PROVENGE group. Reactions included chills, fever, fatigue, asthenia, dyspnea, hypoxia, bronchospasm, dizziness, headache, hypertension, muscle ache, nausea, and vomiting. No Grade 4 or 5 acute infusion reactions were reported in patients in the PROVENGE group.

To fulfill a post marketing requirement and as a part of the company's ongoing commitment to patients, Dendreon will conduct a registry of approximately 1500 patients to further evaluate a small potential safety signal of cerebrovascular events. In four randomized clinical trials of PROVENGE in prostate cancer patients, cerebrovascular events were observed in 3.5% of patients in the PROVENGE group compared with 2.6% of patients in the control group.

For more information on PROVENGE, please see the full prescribing information at [ http://www.provenge.com ] or call 1-877-336-3736.

AboutDendreon

Dendreon Corporationis a biotechnology company whose mission is to target cancer and transform lives through the discovery, development, commercialization and manufacturing of novel therapeutics. The Company applies its expertise in antigen identification, engineering and cell processing to produce active cellular immunotherapy (ACI) product candidates designed to stimulate an immune response in a variety of tumor types. Dendreon's first product, PROVENGE (sipuleucel-T), was approved by the FDA inApril 2010. Dendreonis exploring the application of additional ACI product candidates and small molecules for the potential treatment of a variety of cancers. The Company is headquartered inSeattle, Washingtonand is traded on theNASDAQ Global Marketunder the symbol DNDN. For more information about the Company and its programs, visit [ http://www.dendreon.com ].

This news release contains forward-looking statements that are subject to risks and uncertainties.Factors that could affect these forward-looking statements include, but are not limited to, developments affectingDendreon's business and prospects, including progress on the commercialization efforts for PROVENGE.Information on the factors and risks that could affectDendreon's business, financial condition and results of operations are contained inDendreon's public disclosure filings with theU.S. Securities and Exchange Commission, which are available at[ www.sec.gov ].Dendreon cautions investors not to place undue reliance on the forward-looking statements contained in this press release.All forward-looking statements are based on information currently available toDendreonon the date hereof, andDendreonundertakes no obligation to revise or update these forward-looking statements to reflect events or circumstances after the date of this press release, except as required by law.