Symptomatic Metastatic Castration-resistant Prostate Research Articles

Decreased fracture rate by mandating bone protecting agents in the EORTC 1333/PEACEIII trial combining Ra223 with enzalutamide versus enzalutamide alone: An updated safety analysis.

5002 Background: The randomized phase III EORTC-1333-GUCG (NCT02194842) trial compares enzalutamide vs. a combination of Radium 223 and enzalutamide in asymptomatic or mildly symptomatic metastatic castration resistant prostate cancer (mCRPC) patients. The premature unblinding of ERA223 (NCT02043678) in Nov 2017 due to a significant increase in the rate of fractures in the combination of abiraterone and Ra223 arm led to the implementation of the mandatory use of bone protecting agents (BPA) in the EORTC-1333-GUCG trial. Skeletal fractures, pathological or not, are a frequent and underestimated adverse event of systemic treatment of advanced prostate cancer. Whether this mandated use of BPA (zoledronic acid or denosumab) would mitigate the risk of fractures in this patient population was unclear. An early safety analysis (Tombal, ASCO, 2019) suggested that the risk of fractures was well controlled in both arms when patients receive BPA. We present here an updated analysis of fracture incidence with longer follow-up. Methods: As of 28/01/2021, a total of 253 patients (134 after making BPA mandatory) were randomized between enzalutamide/Ra223 and enzalutamide. The fracture rate was estimated with the cumulative incidence method in the safety population of 237 (122 after making BPA mandatory) treated patients. Death in absence of fracture was analyzed as competing risk and censoring was applied at last follow-up. Results: Overall, 69.5% of enzalutamide/Ra223 patients (95.2% after making BPA mandatory) and 73.1% of enzalutamide patients (95% after making BPA mandatory) received BPA on treatment: 13.6% in the enzalutamide/Ra223 arm and 21.8% in the enzalutamide arm did not use BPA at registration, but started during protocol treatment and 55.9% and 51.3% respectively, received BPA since entry. At 36.7 months median follow-up in patients without BPA and 23.1 months median follow-up in patients receiving BPA, a total of 39 patients reported a fracture. Among them, 30 patients (20 in enzalutamide/Ra223 arm) did not receive BPA and 9 (4 in the enzalutamide/Ra223 arm) received BPA (see table). Conclusions: The updated safety analysis confirms the early fracture rate results. In the absence of BPA, the risk of fracture is increased when RA223 is added to enzalutamide. Strikingly, in both arms, the risk remains almost abolished by a preventive continuous administration of BPA, thus stressing the importance of complying to international recommendations in terms of giving BPA to mCRPC patients. This study is sponsored by EORTC and supported by Bayer and Astellas. Clinical trial information: NCT02194842. [Table: see text]

Phase Ib study assessing different sequencing regimens of atezolizumab (anti-PD-L1) and sipuleucel-T (SipT)in patients who have asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer.

e17564 Background: Combining an immune checkpoint inhibitor with a tumor vaccine may leverage complementary mechanisms of action for treatment of mCRPC. Atezolizumab, a fully human anti–PD-L1 IgG1 antibody, is an approved treatment option in multiple indications; while SipT, an autologous cellular immunotherapeutic, is approved for treatment of metastatic castrate resistant prostate cancer (mCRPC). We present a phase Ib study evaluating safety, tolerability and objective response rate of atezolizumab + SipT in patients with mCRPC (NCT03024216). Methods: Eligible patients who had asymptomatic or minimally symptomatic progressive mCRPC and met standard criteria for sipuleucel-T were randomized to receive either atezolizumab 1200 mg IV every 3 weeks for 2 doses then SipT IV every 2 weeks for a total of three infusions (Arm 1) or SipT IV every 2 weeks for a total of three infusions followed by atezolizumab 1200 mg IV every 3 weeks for 2 doses (Arm 2). The primary endpoint was safety, while secondary endpoints included objective tumor response (PCWG2 and modified RECISTv1.1 criteria) and comparing systemic immune responses after induction between the arms. Results: As of February 6, 2020, 37 pts (median follow-up 7.4 months, median age 75 yrs [range 53.0–86.0]; median number of previous treatments 4 [range 1-8], 75.7% ECOG PS = 0) were enrolled. Three patients did not complete induction therapy (1 – withdrew consent, 1 developed toxicity, and 1 progressed). There were no grade 5 toxicities attributed to study drugs and grade 4 toxicities were noted in 2 patients, 1 in each arm (Arm 1 bronchitis and Arm 2 hypotension). Eight grade 3 toxicities were noted in arm 1 (hyponatremia, pulmonary embolus x3, bone pain, hypophosphatemia, shock, tooth fracture from a fall), while 4 grade 3 toxicities were noted in arm 2 (anemia, hypertension x 2, pneumonia). None of the grade 3 or 4 SAEs were noted to be irAEs. At 6 months, there were 11 SD (7 in Arm 1 and 4 in Arm 2), 18 PD and 7 unevaluable (3 withdrew from study and 4 have yet to reach 6 month evaluation). At this time, PFS was noted to be 8.2 months in Arm 1 and 5.8 months in Arm 2 (p = 0.054). Conclusions: The safety profile of the combination of atezolizumab with sipuleucel-T appears manageable in a heavily pre-treated population and consistent with those agents administered as monotherapy. Responses were seen but no CR. Immune activation studies may shed light on which sequence is optimal. Clinical trial information: NCT03024216 .

Radium-223 therapy in symptomatic metastatic castrate resistant prostate cancer (mCRPC) – sequential use post-abiraterone/prednisolone

Radium-223 therapy in symptomatic metastatic castrate resistant prostate cancer (mCRPC) – sequential use post-abiraterone/prednisolone

Radium-223 treatment patterns in a large real-world population.

190 Background: For men with symptomatic metastatic castration resistant prostate cancer (mCRPC), radium-223 was shown to improve overall survival in the phase III, double blind ALSYMPCA trial. Despite the observed benefits, the application and practice patterns of Radium-223 outside of clinical trials are largely unknown. Here we aim to better characterize the use of radium-223 in a large and heterogeneous real-world population. We identify treatment patterns associated with radium-223 and link these patterns with time to skeletal related event (SRE) and mortality. Methods: We reviewed charts of all men with diagnosed with mCRPC in the entire Veterans Affairs (VA) system alive as of January 1, 2013 who received radiun-223. We generated Kaplan Meier curves for survival and time to SRE based on treatment patterns. We examined the association between common treatment patterns and mortality and time to SRE with Cox models. Results: We identified 318 men with bone mCRPC who received radium-223. Median age at radium start was 69 ys and median follow up was 25.3 months. Median survival was 11 months. 277 patients died during the study period (87%). 50% (158/318) completed ≤4 injections. There was a significant difference mortality among four consolidated treatment patterns (p=0.005) and but no difference SRE (p=0.10). On univariable and multivariable analysis, men who received AR target + docetaxel + radium-223 had increased mortality vs. men who received AR target + radium-223 (p=0.010 and 0.005, respectively). Multivariable analysis showed that non-black race, bone pain, SRE prior to radium, and higher PSA were all linked with worse mortality. Conclusions: We described the largest known cohort of men in the real world who received radium-223. We identified common treatment patterns with differing risk for overall mortality. Further prospective studies are needed to better understand whether differences in survival are attributed to worsening disease status requiring more aggressive therapy, lead-time bias, or true differences in treatment efficacy.

1042 - Radium 223 therapy in symptomatic metastatic castrate resistant prostate cancer - quality of life matters: Real-world outcomes from a single UK centre

1042 - Radium 223 therapy in symptomatic metastatic castrate resistant prostate cancer - quality of life matters: Real-world outcomes from a single UK centre

Randomized phase II trial of sipuleucel-T immunotherapy preceded by sensitizing radiation therapy and sipuleucel-T alone in patients with metastatic castrate resistant prostate cancer

BackgroundSipuleucel-T is an autologous cellular immunotherapy indicated for patients with asymptomatic or minimally symptomatic metastatic castration resistant prostate cancer (mCRPC). Since radiation therapy (RT) can suppress bone marrow function and immune responses, previous studies evaluating sipuleucel-T excluded patients who received RT less than or equal to 28 days prior to sipuleucel-T therapy. Recent evidence suggests that RT may act synergistically with immunotherapy to enhance and broaden antitumor immune response. MethodsPatients who met standard criteria for sipuleucel-T were randomized to receive sipuleucel-T alone (Arm A) or sipuleucel-T initiated 1 week after completing sensitizing RT to single metastatic site (Arm B). RT was delivered at 300cGy/day to 3000 cGy total. The primary endpoint was the ability to safely combine sipuleucel-T preceded by RT and generate sipuleucel-T with adequate product immune activation parameters. Secondary endpoints included the measurement of systemic immune responses to prostatic acid phosphatase (PAP), a target for sipuleucel-T immune therapy and PA20204 (recombinant fusion protein utilized in the generation of sipuleucel-T). Results51 pts were enrolled, 2 did not receive any sipuleucel-T because of vascular access problems and were excluded. 24 were treated on Arm A, 25 on Arm B. 47/49 patients received all 3 sipuleucel-T infusions. Median age was 66 yrs (range 45–90). Sipuleucel-T product parameters including: total nucleated cell (TNC) count, antigen presenting cell (APC) count were similar in both groups. Cumulative APC upregulation was higher in Arm A. 1 patient in Arm A demonstrated PSA response. Median progression free survival (PFS) was 2.46 months on Arm A and 3.65 months on Arm B (p = 0.06). Both arms showed similar increases in humoral responses to PA2024 and PAP. IFN-ƴ ELISPOT T-cell activation responses to PA20204 were observed in both arms, but were more robust in the Arm A (p = 0.028). Both arms were well-tolerated, with fatigue as the most common grade 2 adverse event (1 patient in Arm A and 3 patients in Arm B). ConclusionsSensitizing RT completed 1 week before generation of sipuleucel-T did not affect the majority of product parameters and the ability to deliver sipuleucel-T therapy. RT did not enhance the humoral and cellular responses associated with sipuleucel-T therapy.

Abstract 4046: The different immune evasion mechanisms in human prostate cancer

Abstract Cancer development is associated with a number of genetic and epigenetic alternations. Normally, these alterations are detected by the immune system in a process called immune surveillance, where cancer cell killing is mediated by cytotoxic T lymphocytes (CTL) and natural killer cells (NK cells). Yet, tumor progression and development indicate that cancer cells have acquired mechanisms to avoid immune destruction. Various immune evasion mechanisms have been reported before such as impaired antigen presentation and activation of CTL and NK cells, immunosuppression, and induction of tolerance. Although current treatment methods are shifting towards more targeted strategies in prostate cancer, such as immunotherapy, a better understanding of the cancer-immune interactions and immune evasion mechanisms is yet to be established. More immunotherapies are being developed and approved by the FDA for treating cancer. In prostate cancer, Sipuleucel-T, an autologous cellular immunotherapy, was approved by FDA for the treatment of asymptomatic or minimally symptomatic metastatic castrate resistant (hormone refractory) prostate cancer. Intensive investigation on other immunotherapies is ongoing in prostate cancer. These include blockade of negative checkpoint regulators (PD-1, CTLA4) and Ig superfamily member V-domain Ig-containing suppressor of T-cell activation (VISTA), chimeric antigen receptor-modified T (CAR-T) cells against prostate lineage-unique proteins (PLUPs), and monoclonal antibodies targeting immunoinhibitory molecules. However, the optimal choice of treatment for a prostate cancer patient needs to target their specific mechanisms of immune evasion, which are poorly studied. In this study, we will use The Cancer Genome Atlas RNA-seq data to check for immune evasion gene expression in prostate cancer patients to identify at the different mechanisms by which cancer avoids immune destruction. We will use a sequential biclustering algorithm developed by our group, to group prostate cancer patients based on their similarities in immune evasion gene expression. A similar unpublished work was done by our group on breast cancer where we identified 7 different groups of patients, each with different mechanisms or combination of evasion mechanism. We also showed that triple negative breast cancer can be immunogenic and non-immunogenic. This group-based identification of evasion mechanisms will not only provide a better understanding of the different immune evasion mechanisms in prostate cancer, but will also shed light on potential combinations of mechanism. This in turn, will help guide the choice of single and combined immunotherapeutic approches. Citation Format: Mayassa J. Bou-Dargham, Yuhang Liu, Qing-Xiang Amy Sang, Jinfeng Zhang. The different immune evasion mechanisms in human prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4046.

Randomized, multicentre phase II trial of the sequencing of radium-223 and docetaxel plus prednisone in symptomatic bone-only metastatic castration-resistant prostate cancer (mCRPC).

TPS396 Background: Currently, the challenge is to reach a consensus on the best way to sequence different therapies for mCRPC patients (pts) in terms of efficacy and tolerability. Radium223 is a novel survival-prolonging targeted-α-therapy, but timing of its use in the treatment sequence of mCRPC remains an unanswered question, given the wide availability of therapeutic options Methods: This is a prospective, multicenter, randomized phase II study in symptomatic bone-only mCRPC pts who progressed after any androgen deprivation therapy, abiraterone and/or enzalutamide. Pts will be randomized 1:1 to receive radium223 initially followed by docetaxel+prednisone at the time of progression, or docetaxel+prednisone initially followed by radium223 at progression. In both treatment arms, the second step will be optional according to clinical evolution of disease (clinical deterioration and/or development of visceral metastases); however, each patient that will not enter in the second step will be still evaluable for the objectives of the study. No stratification factor will be used for randomization. Primary endpoint is to determine the better tolerated sequencing between radium223 and docetaxel in terms of health-related quality of life after completing the sequence and separately after each treatment. Based on primary endpoint, considering a type I error 0.1, type II error 0.2, proportion of responder pts in the standard arm 0.1 and in the experimental arm of 0.4, and assuming 10% loss to follow-up, a total of 70pts (35 for each arm) will be enrolled in the study. The study duration will be 36months; 15months of accrual, and 1 year of follow-up on the last participant enrolled. Secondary endpoints are to compare overall/progression-free/total progression free survival in pts treated with sequential therapy between radium223 and docetaxel. Additional secondary objective is to identify predictive factors for radium223 therapy, including potential circulating biomarkers through the plasma collection from all enrolled pts at different timepoints and the early prognostic role of functional imaging, such as PET with choline and/or PSMA. Clinical trial information: NCT03230734.

Radium 223 Therapy in Symptomatic Metastatic Castrate Resistant Prostate Cancer – Newcastle Experience: a Quality of Life Issue

Radium 223 Therapy in Symptomatic Metastatic Castrate Resistant Prostate Cancer – Newcastle Experience: a Quality of Life Issue

Randomized phase II trial of sipuleucel-T immunotherapy preceded by sensitizing radiation therapy and sipuleucel-t alone in patients with metastatic castrate resistant prostate cancer.

222 Background: Sipuleucel-T (sip-T) is an autologous cellular vaccine indicated for patients (pts) with asymptomatic or minimally symptomatic metastatic castration resistant prostate cancer (mCRPC). Since radiation therapy (RT) can suppress the bone marrow function and immune response, previous studies evaluating sip-T excluded pts who received RT less than or equal to 28 days prior to sip-T therapy. Recent evidence suggests that RT may act synergistically with immunotherapy to enhance and broaden antitumor immune response. Methods: Pts who met standard criteria for sip-T were randomized to receive sip-T alone (Arm A) or sip-T initiated 1 week after completing sensitizing RT to single metastatic site (Arm B). RT was delivered at 300cGy/day to 3000 cGy total. The primary endpoint was the ability to safely combine sip-T preceded by RT and generate sip-T product with adequate immune activation parameters. Secondary endpoints included the measurement of immune responses to prostatic acid phosphatase (PAP) and PA20204 (recombinant fusion protein utilized in the generation of sip-T). Results: 51 pts were enrolled, 2 did not receive any sip-T because of vascular access problems and were excluded. 24 were treated on Arm A, 25 on Arm B. 47/49 pts received all 3 sip-T infusions. Median age was 66 yrs (range 45-90). Sip-T product parameters including: total nucleated cell (TNC) count, antigen presenting cell (APC) count and APC activation were similar in both groups. 2 pts on Arm A demonstrated PSA response. Median progression free survival (PFS) was 3.0 months on Arm A and 4.6 months on Arm B (p = 0.19). Both arms showed similar increases in humoral responses to PA2024 and PAP. IFN-ƴ ELISPOT T-cell activation responses to PA20204 were observed in both arms, but were more robust in the Arm A (p = 0.04). Both arms were well-tolerated, with fatigue as the most common grade 2 adverse event (1 pt in Arm A and 3 pts in Arm B). Conclusions: Sensitizing RT completed 1 week before generation of sip-T did not affect product parameters and the ability to deliver sip-T therapy. RT did not enhance the humoral and cellular responses associated with sip-T therapy. Clinical trial information: NCT01807065.

The Effect of Metformin Use during Docetaxel Chemotherapy on Prostate Cancer Specific and Overall Survival of Diabetic Patients with Castration Resistant Prostate Cancer

Docetaxel is the first line chemotherapy currently used to treat patients with symptomatic metastatic castration resistant prostate cancer. Although it provides survival benefits, it is associated with significant side effects. Novel therapeutic options are needed for patients with metastatic castration resistant prostate cancer and an approach is combining docetaxel with chemosensitizing agents. Metformin has been shown to improve the survival of patients with breast, lung and endometrial cancer receiving chemotherapy, and enhance chemotherapeutic efficacy in breast cancer and colon cancer cells. However, to our knowledge the chemosensitizing effect of metformin in prostate cancer has not been explored. Therefore, the hypothesis for our study was that diabetic patients with metastatic castration resistant prostate cancer who were administered metformin during docetaxel chemotherapy would have improved prostate cancer specific and overall survival. This retrospective cohort study used data from several Ontario administrative health care databases. Men older than 65 years diagnosed with metastatic castration resistant prostate cancer and treated with docetaxel were stratified into groups based on diabetes status and use of antidiabetic medications. We evaluated the effect of metformin use with docetaxel on prostate cancer specific survival and overall survival using Kaplan-Meier survival curves, the log rank test and multivariate Cox proportional HRs. Survival curves showed that metformin use with docetaxel did not improve prostate cancer specific survival (p = 0.9562) or overall survival (p = 0.9927). HRs showed no significant effect of metformin use with docetaxel on prostate cancer specific survival (HR = 0.96, p = 0.66) or overall survival (HR = 0.94, p = 0.39). Metformin use during docetaxel chemotherapy did not significantly improve prostate cancer specific or overall survival in diabetic patients with metastatic castration resistant prostate cancer. This study indicates that metformin may not be an effective chemosensitizer for metastatic castration resistant prostate cancer.

Abstract 1313: Characterization and isolation of antigen-responding T cells in Sipuleucel-T treated patients

Abstract Sipuleucel-T is an FDA-approved autologous cellular therapy for men with asymptomatic or minimally symptomatic metastatic castrate resistant prostate (mCRPC). Sipuleucel-T is manufactured from peripheral blood mononuclear cells (PBMCs) cultured with PA2024, a fusion antigen composed of prostatic acid phosphatase (PAP) fused to granulocyte macrophage-colony stimulating factor (GM-CSF). We have demonstrated that following three infusions this therapy results in T cell antigen specific responses directed against both PA2024 and PAP in treated patients. In this study we utilized the cellular dye Carboxyfluorescein succinimidyl ester (CSFE) and flow cytometric analysis to further characterize antigen responding T cells in Sipuleucel-T treated patients. We observed that CD4+ T cells predominate the antigen-responding T cell population following treatment, confirming our previous studies. Importantly, this approach has allowed us to also visualize a previously undetected population of antigen responding CD8+ T cells. The frequency of both of these populations is enhanced following treatment relative to baseline responses and the responding T cells display increased surface expression of the prototypical T cell activation markers CD134 and CD137 relative to non-proliferating T cells. Additionally, we are exploiting the increased surface expression of these activation markers on antigen-responding T cells to isolate these cells in an HLA and epitope-independent manner. Using this methodology we have demonstrated Sipuleucel-T is capable of inducing both CD4+ and CD8+ antigen-specific T cell responses in treated patients, and that we are capable of isolating these antigen-responding T cells specifically and with minimal manipulation. Citation Format: Jeff Pufnock, Tuyen Vu, James Trager, Nadeem Sheikh. Characterization and isolation of antigen-responding T cells in Sipuleucel-T treated patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1313. doi:10.1158/1538-7445.AM2015-1313

Abstract 2937: Localization of sipuleucel-T- expanded T cell clones into tumors of treated prostate cancer patients

Abstract Sipuleucel-T is an FDA-approved autologous cellular therapy demonstrated to prolong overall survival in subjects with asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer (mCRPC). Sipuleucel-T is generated by culturing patients' own peripheral blood mononuclear cells (PBMC) with a fusion protein of prostatic acid phosphatase and granulocyte macrophage colony stimulating factor. While antigen presenting cells take up this antigen and can prime antigen specific T cells in vivo, the majority of the cells in the sipuleucel-T product are in fact T cells. Moreover, antigen-specific T cells in the product become activated during production of sipuleucel-T, particularly for the 2nd and 3rd infusions. To examine whether T cells contained in sipuleucel-T might be homing to the site of the tumor, we used a next-generation sequencing-based method to assess T cell repertoire diversity in the blood, sipuleucel-T product, and resected tissues of patients participating in a neoadjuvant study of sipuleucel-T treatment (P07-1; NCT00715104). In this trial, patients with localized prostate cancer received sipuleucel-T prior to undergoing radical prostatectomy (RP). DNA extracted from the different samples was amplified using a multiplex PCR assay to amplify the CDR3 region of the T cell receptor spanning the variable region formed by the junction of the V, D and J segments and their associated non-templated insertions. Sequence reads were used to quantitate absolute TCR frequencies using standardized clonotype determination algorithms. We found that a subset of T cell clones was enriched in the generation of sipuleucel-T. We also found that T cell clones were expanded in patient blood after each successive infusion. When we examined the T cell clonotypes in the prostate tissues resected after sipuleucel-T treatment, we found that there were T cell clones in the prostate in common with the sipuleucel-T product. Interestingly a number of the clones present in the pre-treatment blood were reduced or lost in the blood by the second and third infusion but were present in the post-treatment prostate tissue, consistent with trafficking of the T cell clones from the peripheral circulation. These results indicate that ex vivo production of sipuleucel-T induces the expansion of certain T cell clones that are ultimately present in the prostates of patients treated prior to RP. Sipuleucel-T may therefore also function as an adoptive T cell therapy. Citation Format: Lawrence Fong, Todd DeVries, Jason Cham, Li Zhang, Mark Frohlich, James Trager, Nadeem Sheikh. Localization of sipuleucel-T- expanded T cell clones into tumors of treated prostate cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2937. doi:10.1158/1538-7445.AM2014-2937

A randomized phase II study evaluating the optimal sequencing of sipuleucel-T and androgen deprivation therapy (ADT) in biochemically recurrent prostate cancer (BRPC): Immune results.

5016 Background: ADT is a standard treatment for men with BRPC after failure of local therapy, and has immunomodulatory effects. Sipuleucel-T is an autologous cellular immunotherapy approved for asymptomatic/minimally symptomatic metastatic castrate resistant prostate cancer. The STAND trial (NCT01431391) aimed to evaluate optimal sequencing of sipuleucel-T and ADT in men with BRPC at high risk for metastases (ie PSA doubling time ≤12 mo). Methods: Men were randomized (1:1) to Arm 1: sipuleucel-T followed by ADT (2 wks after 3rd infusion); or Arm 2: ADT (3 mo lead in) followed by sipuleucel-T. All men had 3 doses of sipuleucel-T and 12 mo of ADT (45 mg leuprolide SQ at 6 mo intervals). The primary endpoint is cellular immune response (ELISPOT to PA2024 [PAP-GMCSF]). Secondary endpoints are humoral and cytokine responses, product parameters and safety. Results: 68 men were randomized. Preliminary data show higher levels of serum cytokines in Arm 2 vs Arm 1, with a pattern suggesting a mixed TH1/TH2 cellular immune response; elevations were seen in TH1 (IFNγ, IL 12), TH2 (IL 4, 5, 10, 13) and TH17 (IL 17) subsets (all P<.05). The increase in TH1 cytokines was consistent with a trend toward higher PA2024-specific ELISPOT responses 2 wk after the 3rd sipuleucel-T infusion in Arm 2 vs Arm 1 (40.5 vs 12.8 spots; P=.086), suggesting increased T cell activation in Arm 2. Antigen-specific humoral responses were induced in both arms with no differences yet observed between arms. Sipuleucel-T product parameters were roughly equivalent in both arms with APC activation data indicating a robust prime-boost effect. Conclusions: While confirmation is required, these preliminary data suggest that tumor-specific T cell responses and broad based immune responses are augmented when sipuleucel-T is given after rather than before ADT initiation. These data are consistent with preclinical studies showing that ADT enhances T cell activity, and provide preliminary evidence that combining ADT with sipuleucel-T may augment adaptive immunity. Further follow up will determine whether augmented immune responses correlate with clinical parameters (eg PSA recurrence). Clinical trial information: NCT01431391.

Preliminary safety, product parameters, and immune response assessments from a phase II randomized, open-label trial of DN24-02, an autologous cellular immunotherapy (ACI), in patients (pts) with surgically resected HER2+ urothelial cancer (UC) at high risk for recurrence.

4547^ Background: DN24-02 is a HER2-targeted ACI, consisting of antigen presenting cells (APC) cultured with BA7072, a recombinant HER2-derived antigen (HER500) linked to GM-CSF; DN24-02 is based on the same manufacturing platform as sipuleucel-T, approved for asymptomatic/minimally symptomatic metastatic castrate resistant prostate cancer. NeuACT (N10E1; NCT01353222) is an open-label, randomized phase 2 trial comparing adjuvant DN24E02 to surveillance in HER2+ UC pts at high risk of relapse following cystectomy or nephroureterectomy. The primary endpoint is overall survival. Here we report preliminary evaluation of adverse events (AE), product potency, and immune response. Methods: Pts randomized to DN24-02 underwent leukapheresis followed by infusion of DN24-02 (total of 3 infusions with 2 wk intervals). AEs were assessed at each visit. Product potency was assessed for each infusion by measuring CD54 upregulation on APCs, a marker of APC activation. Antigen-specific immune responses were evaluated by ELISA to HER500 and BA7072. Results: As of November 2012, 13 pts had received ≥1 DN24-02 infusion. The most commonly reported AEs within 1 day after DN24-02 infusion were mild–moderate chills (54%), nausea (31%) and fatigue (23%). Ten pts completed all DN24-02 infusions and were assessed for product potency. Increased median APC activation at infusions 2 and 3 compared with infusion 1 was indicative of an immunological prime-boost effect; this effect was also seen in the 7/10 pts with prior neoadjuvant chemotherapy. Median anti-BA7072 and anti-HER500 titers (IgM) were 128- and 256-fold higher at week 6 vs baseline, respectively. The emergence of IgG indicated a memory antibody phenotype. Conclusions: Preliminary data indicate that DN24-02 product potency (CD54 upregulation) is comparable to sipuleucel-T. DN24-02 appears to be well tolerated in UC. Favorable immune responses were observed, including in pts with prior neoadjuvant chemotherapy. Updated results, including preliminary T-cell immune response data, will be presented. Clinical trial information: NCT01353222.

Development of a fluorescent dual-cytokine cellular immune response assay: preliminary results from sipuleucel-T treated subjects (P4312)

Abstract In the Phase III IMPACT study evaluating sipuleucel-T, an immunotherapy for asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer, post-treatment antigen-specific cellular responses were detected using an IFNγ ELISPOT assay. While this assay is a robust readout of memory responses, it only detects one cytokine, providing minimal information of the responding cells. As clinical trial samples are limited, simultaneous detection of multiple cytokines is a pragmatic alternative that provides additional information without using more cells. The UV-fluorescent FluoroSpot assay detects multiple cytokines, providing an understanding of the phenotype of the immune response. FluoroSpot results were concordant to the ELISPOT data; antigen-specific IFNγ responses were seen after treatment in sipuleucel-T subjects, indicating treatment produced immunological memory. However, we saw that IL-2 secreting cells were maintained throughout treatment, whereas IL-5 secreting (Th2) cells decreased after the first infusion. Most importantly, the FluoroSpot assay showed the generation of polyfunctional T cells (IFNγ/IL-2 and IFNγ/IL-5) after treatment. The presence of the distinct dual cytokine functional T cell signatures supports the supposition that sipuleucel-T induces proliferative antigen-specific T cell immunological responses. The multi-analyte FluoroSpot assay may provide insight into the roles of other different cell populations after sipuleucel-T treatment.

PCN35 - Comparative Analysis Of Radium-223 Versus Placebo In Symptomatic Metastatic Castration Resistant Prostate Cancer Treated With Best Standard Of Care On Skeletal-Related Events Outcomes

PCN35 - Comparative Analysis Of Radium-223 Versus Placebo In Symptomatic Metastatic Castration Resistant Prostate Cancer Treated With Best Standard Of Care On Skeletal-Related Events Outcomes

A phase II study of linsitinib (OSI-906) in patients with asymptomatic or mildly symptomatic (non-opioid requiring) metastatic castrate resistant prostate cancer (CRPC).

197 Background: Novel agents capable of blocking AR ligand independent pathways responsible for the development of CRPC are needed. IGF-1R and its ligands (IGF-1/IGF-2) play a key role in regulating growth, resistance to apoptosis, and invasion in PCa. IGF-1R is overexpressed in PCa and mediates resistance to ADT. OSI-906 is a small molecule potent dual inhibitor of IGF-1R and insulin receptor TK activity. To determine the activity of OSI-906 in men with CRPC a Simon two-staged phase II study was conducted. Methods: Men with asymptomatic or mildly symptomatic Met CRPC were eligible. ECOG 0-1, adequate organ function, and no prior chemotherapy for CRPC were required. Pts received OSI-906 at 150mg orally twice daily on a 28-day cycle. Endpoints included PSA response at 12 wks, safety, RECIST-defined response, time to PSA progression, and OS. Correlative studies explored the impact of OSI-906 on AR signaling (androstenedione, DHEA, DHEA-sulfate, p-IGF-1R, p-IR), markers of PD (TGF-b1, IL-6, TNF-a, MCP-1), and CTC and CECs. Results: To date 18 pts have enrolled and completed 12 wks of therapy. Median age 68 (55-78); Median pre-treatment PSA was 55.23 (range 2.46-277.60); 41% of pts had bone-only disease, 29% soft-tissue only and 29% had both. Although transient PSA declines were noted, 17/18 pts discontinued therapy sec PSA progression. RECIST-defined SD was observed in 8 pts. Pts received a median of 3 cycles of therapy (range 2-6+). Most common G1/2 AEs included AST/ALT changes observed in 41 and 18% of patients respectively, fatigue (59%); prolong QT interval (35%) and nausea/vomiting (35%). No significant change in the number of CTC and CEC counts was observed. An association between pre-treatment PSA and pre-treatment CTC was observed (Spearman r=0.49, p=.04). No correlation between CTC changes and PSA progression was observed .Evaluation of other molecular markers of PD is underway. Conclusions: Treatment with OSI-906 is safe. No PSA responses or changes in CTC/CECs were noted. Markers of PD might help elucidate potential mechanisms of escape to this alternative pathway in CRPC. OSI-906 plus an AA might provide synergistic activity in this setting. Clinical trial information: NCT01533246.

Abstract B18: Combining selective toll-like receptor 9 (TLR9) agonists and GM-CSF activity for potentiating cellular activation in active cell immunotherapy (ACI).

Abstract Sipuleucel-T (Provenge®), indicated for the treatment of asymptomatic or minimally symptomatic metastatic castration resistant prostate cancer, is the first FDA-approved Active Cellular Immunotherapy (ACI). Here we describe the development of a therapeutic ACI for the treatment of renal, lung, colon, and cervical cancer. Like PROVENGE®, this new ACI utilizes a recombinant antigen consisting of carbonic anhydrase IX (CA9) linked to GM-CSF (CA9:GM-CSF). In these studies, we investigated the effects of incorporating selective TLR9 agonists on in vitro measures of ACI potency. Initially, employing a panel of proprietary TLR9 agonists, we compared the phenotype of antigen presenting cells (APC) following culture of PBMC from normal healthy donors with either CA9:GM-CSF or CA9:GM-CSF plus TLR9 agonist. While antigen derived GM-CSF activity matured APC, characterized by elevated cell surface expression of CD40, CD54, CD80 and CD86, proprietary agonists for TLR9 further enhanced expression of CD40, CD80, and CD86. By extension, stimulation via TLR9 elicited increased costimulatory capacity of CD14+ large APC in allogeneic mixed lymphocyte response assays. Elevated levels of MCP1-3 in culture supernatant were consistent with APC activation, and notably, viability of CD14+ large APC was unaffected following TLR9 stimulation within the ACI product. Interestingly, using an HLA class II restricted CA9-specific T cell hybridoma reporter assay, staggering the addition of CA9:GM-CSF prior to TLR9 agonist was important to maximize antigen uptake and peptide presentation. Collectively, antigen derived GM-CSF activity is robust at activating APC and certain TLR9 agonists strengthen this effect. Next, as determined by cell surface expression of activation markers (CD27, CD38, CD40, CD54, CD86, IgD), the potential for TLR9 agonists to activate B cells was examined. Relative to cultures supplemented with only CA9:GM-CSF, TLR9 agonists were sufficient to produce a generalized B cell activation pattern consisting of enhanced cell surface expression of CD38, CD40, CD86, and CD54; while expression of CD27 was decreased. Expression of IgD remained unchanged. Associated with the prominent pattern of B cell activation was a marked increase in the accumulation of proinflammatory Type-1 like growth factors (IFN-α, IFN-γ, CXCL9, CXCL10, CCL3, and CCL4) in response to each TLR9 agonist. Despite the degree of B cell activation, this phenotype did not correlate with cellular activation of any T cell subset; suggesting the inflammatory signature resulting from TLR9 stimulation is primarily driven by B cells and/or APC in the ACI setting. Importantly, IL-10 levels were significantly enhanced following TLR9 stimulation, raising the possibility for enhanced regulatory cell activity, but changes in the frequency of regulatory CD4+ T cells were not observed. However, continuing studies are aimed at examining whether regulatory B cell numbers may be enhanced. Thus, in the ACI product, TLR9 agonists potentiate B cell activation and represent powerful polarizers of predominantly Type 1-like cytokine responses. Overall, agonists of TLR9 are compatible with the ACI platform for potentially enhancing antigen specific immunotherapy of cancer. In current experiments, the capacity of TLR9 agonists to enhance cross-priming and generate cytotoxic T cell responses is under investigation. Citation Format: Jason Chinn, Crystal Cummings, Felecia Wagener, Shaarwari Sridhar, Kien Khuu-Duong, Xinhui Ge, Karen Yoshino, Sam Li, Lisa Martel, Chris Ramsborg, Ken Brasel, James Trager, Craig Meagher. Combining selective toll-like receptor 9 (TLR9) agonists and GM-CSF activity for potentiating cellular activation in active cell immunotherapy (ACI). [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B18.

An Analysis of Leukapheresis and Central Venous Catheter Use in the Randomized, Placebo Controlled, Phase 3 IMPACT Trial of Sipuleucel-T for Metastatic Castrate Resistant Prostate Cancer

Sipuleucel-T is an autologous cellular immunotherapy. We review the safety of the leukapheresis procedure required for sipuleucel-T preparation and complications related to venous catheter use in the randomized, placebo controlled phase 3 IMPACT (IMmunotherapy for ProstAte Cancer Trial) study (NCT 00065442). A total of 512 patients with asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer were enrolled in the study. All patients were scheduled to undergo 3 standard 1.5 to 2.0 blood volume leukapheresis procedures at 2-week intervals. Leukapheresis related adverse events and those related to venous catheter use were reviewed. Immune cell counts were examined throughout the treatment course. Of 512 enrolled patients 506 underwent 1 or more leukapheresis procedures and were included in this analysis. Adverse events were comparable between the sipuleucel-T and control arms. Leukapheresis related adverse events were primarily associated with transient hypocalcemia (39.3%). Most leukapheresis related adverse events (97%) were of mild/moderate intensity. Median white blood cell count and absolute monocyte and lymphocyte counts were stable and within normal ranges throughout the treatment course. Of all patients 23.3% had a central venous catheter placed primarily for leukapheresis. Patients with vs without a central venous catheter had a higher risk of infection potentially related to catheter use (11.9% vs 1.3%, p <0.0001) and a trend toward a higher incidence of venous vascular events potentially related to catheter use, excluding the central nervous system (5.9% vs 2.1%, p = 0.06). Adverse events related to leukapheresis are manageable and quickly reversible. The majority of patients can undergo leukapheresis without a central venous catheter. Central venous catheters are associated with an increased risk of infections and venous vascular events. Peripheral intravenous access should be used when feasible.