(mCRPC) in a randomized, placebo?controlled 125-pt Phase 2 trial.Data from the Phase 2 trial supported the design of a Phase 3 protocolthat will test the hypothesis of OS benefit, as well as expand ourunderstanding of immune system response to therapeutic cancer vac-cines.

METHODS: In the Phase 3 study, 1200 pts will be randomizedin a double-blind fashion to three arms: PROSTVAC-VF, PROSTVAC-VF�GM-CSF, or vector control Placebo, at a 1:1:1 ratio. A five-monthtreatment regimen will include a priming vaccination with PROSTVAC-V, andsix booster vaccinations with PROSTVAC-F. At the end of the treatmentduration, use of other therapies for the treatment of mCRPC is at thediscretion of the investigator. Eligible pts will have asymptomatic orminimally symptomatic mCRPC, progression despite androgen abla-tion, and be chemotherapy-naïve. The projected trial size is 400 pts perarm for at least 85% power. The primary endpoint is OS. The finalanalysis will be event-driven and will compare each active arm inde-pendently with placebo. Patients will be followed for 12 months after theprojected number of events in each arm is realized. Secondary end-point is proportion of event-free (radiological progression, pain progres-sion, chemotherapy initiation, or death) pts at 6 months after start oftreatment compared to placebo. A number of exploratory endpoints areplanned, including immune response to immunizing antigen, non-vac-cine-contained prostate antigens, tumor-associated antigens, changesin baseline biomarker levels and CTC levels, as well as characteriza-tion of T cell subpopulations.

RESULTS: The global Phase 3 PROSPECT trial is currentlyopen for enrollment.

CONCLUSIONS: This Phase 3 trial will test if a pox-viral basedimmunotherapy treatment can prolong OS in pts with asymptomatic tominimally symptomatic mCRPC.

Source of Funding: None

971SAFETY AND CHANGES IN LABORATORY PARAMETERSASSOCIATED WITH SIPULEUCEL-T IN PATIENTS WITHMETASTATIC CASTRATION-RESISTANT PROSTATE CANCER:PHASE 2 PROACT STUDY

Thomas Gardner*, Indianapolis, IN; Daniel Petrylak, New York, NY;John Corman, Seattle, WA; Simon Hall, New York, NY;Ralph Weinstein, Portland, OR; Robert Sims, Todd DeVries,Celestia Higano, Seattle, WA

INTRODUCTION AND OBJECTIVES: Sipuleucel-T is an autol-ogous cellular immunotherapy for asymptomatic or minimally symptom-atic metastatic castration-resistant prostate cancer (mCRPC). Sipuleu-cel-T prepared using the FDA-approved concentration of 10�g/mLPA2024 (PAP-GM-CSF antigen) stimulates immune responses andprolongs overall survival (OS). ProACT (P07-2; NCT00715078) is anongoing phase 2 study to evaluate immune responses and OS ofsipuleucel-T when manufactured using three different concentrations(2, 5 or 10�g/mL) of PA2024. Here we report the preliminary safetyanalysis and changes in laboratory parameters.

METHODS: Patients (pts) with asymptomatic or minimallysymptomatic mCRPC received sipuleucel-T manufactured using 2, 5 or10�g/mL PA2024 for a total of 3 infusions with 2-week intervals.Adverse events (AEs) were recorded continuously and laboratory sam-ples for assessment were taken 2, 4 and 6 months (mos) after the firstinfusion.

RESULTS: 120 pts were included in the safety analysis (2�g/mL, n�40; 5�g/mL, n�40; 10�g/mL, n�40). Baseline characteristicswere balanced across the arms. The most common AEs (occurring in�20% of pts in the total population) were fatigue (44.2%), back pain(30.8%), nausea (30.8%), arthralgia (25.8%) and chills (25.8%), with aconsistent incidence of these AEs across treatment arms. AEs occur-ring within 1 day of infusion (in �20% of pts in the total population)included fatigue (23.3%) and chills (20.8%). Treatment-related seriousAEs occurred in 4 pts (3.3%), with fatigue (n�3) and dehydration (n�2)the only events occurring in more than 1 pt. Globulin protein levels

increased significantly (p�0.05) from baseline at all time points in the5�g/mL and 10�g/mL arms and at 2 mos in the 2�g/mL arm. Signifi-cant increases in eosinophil counts from baseline were observed at 2mos in the 5�g/mL and 10�g/mL arms (p�0.05). There was nosignificant difference between treatment arms in immune responderfrequencies (any immune response at any time point).

CONCLUSIONS: Increases in globulin protein and transientincreases in eosinophil counts are consistent with previous studies,which showed that these changes in laboratory parameters positivelycorrelate with immune response and OS, respectively, and thus may besurrogates for immune response. Furthermore, these data suggest thatsipuleucel-T manufactured using 3 different concentrations of PA2024has an acceptable safety profile.

Source of Funding: Dendreon Corporation

972TREATMENT PRACTICE PATTERNS IN METASTATICCASTRATION-RESISTANT PROSTATE CANCER (MCRPC)PATIENTS PRIOR TO RECEIVING SIPULEUCEL-T: DATA FROMPROCEED

Matthew Cooperberg*, San Francisco, CA; Oliver Sartor, NewOrleans, LA; Christopher Pieczonka, Syracuse, NY;Raoul Concepcion, Nashville, TN; Vahan Kassabian, Marietta, GA;Ronald Tutrone, Baltimore, MD; James Bailen, Jeffersonville, IN;Neal Shore, Myrtle Beach, SC; Lawrence Karsh, Denver, CO;Bernard Hertzman, Cincinnati, OH; David Penson, Nashville, TN;Candice McCoy, Andrew Sandler, James Whitmore, Robert Tyler,Celestia Higano, Seattle, WA

INTRODUCTION AND OBJECTIVES: PROCEED is an ongo-ing, multicenter, Phase 4 registry enrolling patients treated with sip-uleucel-T outside of a clinical trial in community and academic oncologyand urology practices. Patients are followed for serious adverse events,overall survival, and treatments after sipuleucel-T. Here, we reportpatient baseline demographics and treatment patterns prior to receivingsipuleucel-T in PROCEED.

METHODS: PROCEED will enroll a minimum of 1500 mCRPCpatients who have been prescribed sipuleucel-T or who had their firstleukapheresis for sipuleucel-T no more than 6 months prior to informedconsent. Demographics, disease characteristics, co-morbidities, andprevious and ongoing prostate cancer treatments are recorded atbaseline.

RESULTS: As of October 2012, data are available for 825patients (Table). The median age is 72 years; 88.0% are Caucasian,10.1% African American, and 1.9% other. Median baseline PSA was18.9 ng/mL. Eastern Cooperative Oncology Group Performance Status(ECOG-PS) scores were 0 for 66.4% and 1 for 28.0% of patients anda majority of patients (51.2%) had Gleason sums of �8. A majority(73.9%) of patients received local therapy: radiation (73.1%), radicalprostatectomy (46.9%), TURP (10.8%), and cryosurgery (4.1%). 16.0%of patients received prior chemotherapy; of those, 82.6% receiveddocetaxel.

CONCLUSIONS: PROCEED provides a window into currenttreatment patterns for patients with mCRPC and will continue to yieldimportant information that can be used to track trends in patientdemographics and treatment prior to and after sipuleucel-T in men withmCRPC.

Baseline demographics/disease characteristics1

N 825

Age, yrs (range) 72.0 (66.0-78.0)

Race, %

Caucasian 88.0

African American 10.1

Other 1.9

Weight, kg (BMI) 90.3 (29.0)

LDH (units/L) 188.0

Vol. 189, No. 4S, Supplement, Monday, May 6, 2013 THE JOURNAL OF UROLOGY� e399

PSA, ng/mL

Median 18.9

Range 0.0 to 7497.3

ECOG-PS, %

0 66.4

1 28.0

2 2.2

3 0.2

Unknown 3.2

Gleason scores

Primary 4.0

Secondary 4.0

Sum 8.0

Received local therapy, % 73.92, 3

Radiation 73.1

Radical prostatectomy 46.9

TURP 10.8

Cryosurgery 4.1

Received prior hormone therapy, % 93.52, 3

LHRH4 agonist 77.8

LHRH4 antagonist 24.5

Oral anti-androgen 61.6

Orchiectomy 3.4

Received prior chemotherapy, % 16.02, 3

Docetaxel 82.6

Cabazitaxel 11.4

Other systemic, %

Denosumab 32.0

Zoledronic acid 26.51All numbers are median, unless otherwise specified; 2Data missing for 5.2% pts;3Subcategory percentages derived from main category as denominator; 4Leute-nizing hormone releasing hormone

Source of Funding: Dendreon Corporation

Prostate Cancer: Basic Research (V)

Moderated Poster Session 37

Monday, May 6, 2013 10:30 AM-12:30 PM

973A NEW STRATEGY FOR CASTRATION RESISTANT PROSTATECANCER WITH TARGETING TO FEEDBACK MECHANISM OFPI3K/AKT/MTOR PATHWAY

Yota Yasumizu*, Akira Miyajima, Takeo Kosaka,Yasumasa Miyazaki, Tokyo, Japan; Suguru Shirotake, Saitama,Japan; Eiji Kikuchi, Mototsugu Oya, Tokyo, Japan

INTRODUCTION AND OBJECTIVES: The clinical trials ofmTORC1 inhibiton in CRPC have failed to demonstarate anti-tumoreffect despite the deficit of PTEN observed in about 70% of castrationresistant prostate cancer (CRPC) with metastasis. The up-regulation ofphosphorylated Akt (pAkt) through mTORC2 is reported as one factorof mTORC1 inhibitor resistance. In this study we aimed to establish anew strategy for docetaxel resistant CRPC, with a focus on regulatorysystem in PI3K/Akt/mTOR signaling pathway.

METHODS: The efficacy of PI3K/Akt/mTOR signaling pathwayinhibition by the mTORC1 inhibitor: RAD001 and the PI3K andmTORC1/2 dual inhibitor: NVP-BEZ235 was examined in C4-2AT6cells in vivo and in vitro. C4-2AT6 cells are a new CRPC cell lineestablished by our laboratory under androgen ablation conditions andshows docetaxel resistance.

RESULTS: To examine the inhibitory effect of NVP-BEZ235 orRAD001, we performed the western blotting using C4-2AT6 cells. The

expression of pAkt and phosphorylated S6 ribosomal protein (pS6)were significantly inhibited by 50nM NVP-BEZ235. On the other hand,the expression of pAKT was not inhibited by the treatment withRAD001, although the expression of pS6 was inhibited by 10nMRAD001. Next we tested the effect of NVP-BEZ235 or RAD001 toC4-2AT6 cells by WST assay. The mean cell viability at 24 h oftreatment with 50nM NVP-BEZ235 and 10nM RAD001 was 59.2▫}6.4% and 61.2▫} 7.2%, respectively. There was no significant differ-ence between the two cell viability. The cell viability with 50nM NVP-BEZ235 and 5nM docetaxel was 41.2▫} 5.2% and the cell viability with10nM RAD001 and 5nM docetaxel was 50.1▫} 4.8%. The combinationof NVP-BEZ235 and docetaxel showed significantly higher anti-tumoreffect than the combination of RAD001 and docetaxel (p�0.05). In vivo,we assigned castrated male nude mice to 4 groups; control, NVP-BEZ235 (12.5mg/kg/day), docetaxel (2mg/kg), and NVP-BEZ235 com-bined with docetaxel. We examined the time course changes in C4-2AT6 tumor growth with NVP-BEZ235 and docetaxel. The tumorvolume of NVP-BEZ235 at day15 was 89.8▫} 9.8%, and the tumorvolume of docetaxel was 81.2▫} 6.4%, compared to the control group.While the tumor volume of combined treatment was 6.1▫} 5.5% ofcontrol. The combination therapy exhibited marked suppression oftumor growth compared to control, NVP-BEZ235 monotherapy, ordocetaxel monotherapy (p�0.05).

CONCLUSIONS: The combination of NVP-BEZ235 and do-cetaxel showed significant anti-tumor effects in CRPC, suggesting theefficacy of PI3K/mTORC1/2 dual inhibitor for regulation of PI3K/Akt/mTOR pathway in CRPC.

Source of Funding: None

974FUNCTIONAL P53 DETERMINES DOCETAXEL SENSITIVITY INPROSTATE CANCER CELLS

Chengfei Liu*, Yeizi Zhu, Wei Lou, Xubao Shi, Ralph deVere White,Allen Gao, Sacramento, CA

INTRODUCTION AND OBJECTIVES: Docetaxel is the first linetreatment for castration resistant prostate cancer (CRPC). However,docetaxel resistance rapidly develops. Identifying the critical mecha-nisms giving rise to docetaxel resistance is the major challenge inadvanced prostate cancer.

METHODS: The effects of docetaxel on human DU145, PC3,LNCaP and C4-2 prostate cancer cells were examined in cell culture,and p53 expression were analyzed by Western blot analysis. Thepotential role of p53 in docetaxel sensitivity in prostate cancer cells wastested by either p53 silencing using shRNA or p53 overexpression byintroducing wild-type p53.

RESULTS: We found that DU145 (mutant p53) and PC3 (p53null) cells were less sensitive than LNCaP and C4-2 cells expressingfunctional p53 in response to docetaxel. Docetaxel treatment inducesconsiderably higher apoptosis in LNCaP and C4-2 cells than in DU145and PC3 cells in a dose dependent manner. Docetaxel increases thelevels of ser15 phosphorylation of p53 in a dose dependent manner inboth LNCaP and C4-2 cells, while has no effect on the levels of ser15phosphorylation of p53 in DU145 cells. These results suggest that p53phosphorylation is associated with docetaxel sensitivity in prostatecancer cells. To further confirm whether p53 activation can induce cellsensitivity to docetaxel treatment, we used p53 shRNA to knock downp53 expression in C4-2 cells and determined the cells response todocetaxel treatment. Knockdown of p53 significantly down regulatedp53 phosphorylation and blocked docetaxel induced apoptotic celldeath compared to the vector control. To further confirm this observa-tion, we established a stable knock out p53 in C4-2 cells. Downregulation of p53 in the stable p53 knock out C4-2 cells significantlyinhibited docetaxel induced apoptotic cell death. We also used wild-type (WT) p53 to over express p53 in DU145 cells, and found thatexpression of WT-p53 in DU145 cells increased their sensitivity todocetaxel.

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