Todd DeVries

Humoral Immune Response against Nontargeted Tumor Antigens after Treatment with Sipuleucel-T and Its Association with Improved Clinical Outcome

Purpose: Antitumor activity of cancer immunotherapies may elicit immune responses to nontargeted (secondary) tumor antigens, or antigen spread. We evaluated humoral antigen spread after treatment with sipuleucel-T, an immunotherapy for asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC), designed to target prostatic acid phosphatase (PAP; primary antigen). Experimental Design: Serum samples from patients with mCRPC enrolled in the placebo-controlled phase III IMPACT study (evaluable n = 142) were used to assess humoral antigen spread after treatment with sipuleucel-T. Immunoglobulin G (IgG) responses to self-antigens (including tumor antigens) were surveyed using protein microarrays and confirmed using Luminex xMAP. IgG responses were subsequently validated in ProACT (n = 33), an independent phase II study of sipuleucel-T. Association of IgG responses with overall survival (OS) was assessed using multivariate Cox models adjusted for baseline prostate-specific antigen (PSA) and lactate dehydrogenase levels. Results: In patients from IMPACT and ProACT, levels of IgG against multiple secondary antigens, including PSA, KLK2/hK2, K-Ras, E-Ras, LGALS8/PCTA-1/galectin-8, and LGALS3/galectin-3, were elevated after treatment with sipuleucel-T (P < 0.01), but not control. IgG responses (≥2-fold elevation posttreatment) occurred in ≥25% of patients, appeared by 2 weeks after sipuleucel-T treatment, and persisted for up to 6 months. IgG responses to PSA and LGALS3 were associated with improved OS in sipuleucel-T–treated patients from IMPACT (P ≤ 0.05). Conclusions: Sipuleucel-T induced humoral antigen spread in patients with mCRPC. IgG responses were associated with improved OS in IMPACT. The methods and results reported may identify pharmacodynamic biomarkers of clinical outcome after sipuleucel-T treatment, and help in clinical assessments of other cancer immunotherapies. Clin Cancer Res; 21(16); 3619–30. ©2015 AACR. See related commentary by Hellstrom and Hellstrom, p. 3581

A Randomized Phase II Trial of Sipuleucel-T with Concurrent versus Sequential Abiraterone Acetate plus Prednisone in Metastatic Castration-Resistant Prostate Cancer

Purpose: This phase II open-label study evaluated the effect of concurrent or sequential administration of abiraterone acetate plus prednisone (AA + P) on sipuleucel-T manufacture and immune responses in metastatic castration-resistant prostate cancer (mCRPC) patients. Experimental Design: mCRPC patients received sipuleucel-T followed by AA + P 1 day (concurrent) or 10 weeks (sequential) after the first sipuleucel-T infusion. AA + P treatment continued for 26 weeks. The primary endpoint was cumulative antigen presenting cell (APC) activation, and secondary endpoints included cumulative APC number and total nucleated cell counts. Additional endpoints included in vivo peripheral immune responses to sipuleucel-T (T-cell responses, T-cell proliferation, humoral responses, and antigen spread) as well as safety. Results: Sixty-nine mCRPC patients were enrolled, with 35 and 34 patients randomized to the concurrent and sequential arms, respectively. Ex vivo APC activation was significantly greater at the second and third infusions compared with baseline in both arms (P < 0.05), indicative of an immunologic prime-boost effect. In both arms, sipuleucel-T product parameter profiles and peripheral immune responses were consistent with previously conducted sipuleucel-T phase III trials. Antigen spread was similarly observed in both arms and consistent with the other immunologic endpoints. Conclusions: These data suggest that sipuleucel-T can be successfully manufactured during concurrent administration of AA + P without blunting immunologic effects or altering immune parameters that correlate with sipuleucel-Ts clinical benefit. Combination of these agents was well tolerated, with no new safety signals emerging. Clin Cancer Res; 21(17); 3862–9. ©2015 AACR.

A Transient Increase in Eosinophils Is Associated with Prolonged Survival in Men with Metastatic Castration- Resistant Prostate Cancer Who Receive Sipuleucel-T

McNeel and colleagues demonstrate that a transient increase in eosinophil counts following sipuleucel-T treatment was associated with therapy-induced immune responses and longer prostate cancer survival, suggesting this could be prospectively evaluated as a biomarker in clinical trials. Sipuleucel-T is an autologous cellular immunotherapy used to treat asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). Traditional short-term indicators of clinical response commonly used with chemotherapy have not correlated with survival in patients treated with sipuleucel-T. This retrospective study aimed to evaluate laboratory parameters as possible early biomarkers associated with clinical benefit following sipuleucel-T treatment. Patients treated with sipuleucel-T from three randomized, controlled, phase III clinical trials in mCRPC were considered: IMPACT (NCT00065442; n = 512), D9901 (NCT00005947; n = 127), and D9902A (NCT01133704; n = 98). Patients from these trials were included in this study if their samples were analyzed by the central laboratory and if data were available from baseline and ≥1 posttreatment time point (n = 377). We found that sipuleucel-T treatment was associated with a transient increase in serum eosinophil count at week 6 that resolved by week 14 in 28% of patients (105 of 377). This eosinophil increase correlated with induced immune response, longer prostate cancer–specific survival [HR, 0.713; 95% confidence interval (CI), 0.525–0.970; P = 0.031], and a trend in overall survival (HR, 0.753; 95% CI, 0.563–1.008; P = 0.057). Median serum globulin protein levels also increased transiently, which was associated with antigen-specific antibody responses; however, this finding did not correlate with longer survival. We conclude that transient increases in eosinophils at week 6 may be a useful, objective, short-term indicator of global immune activation and survival benefit with sipuleucel-T in patients with mCRPC. This observation warrants prospective evaluation in future clinical trials. Cancer Immunol Res; 2(10); 988–99. ©2014 AACR.

Combining Immunotherapy and Radiation for Prostate Cancer

Radiotherapy has conventionally been viewed as immunosuppressive, which has precluded its use in combination with immunotherapy for prostate and other cancers. However, the relationship between ionizing radiation and immune reactivity is now known to be more complex than was previously thought, and data on the use of radiotherapy and immunotherapy are accumulating. Herein, we review this topic in the light of recently available data in the prostate cancer setting. Recent research has shown no significant lymphopenia in patients undergoing radiotherapy for high-risk adenocarcinoma of the prostate. In addition, emerging evidence suggests that radiotherapy can have immunostimulatory effects, and that tumor cell death, coupled with related changes in antigen availability and inflammatory signals, can affect lymphocyte and dendritic cell activation. Initial studies have focused on combinations of tumor irradiation and immunotherapy, such as the autologous cellular immunotherapy sipuleucel-T and the monoclonal antibody ipilimumab, in metastatic castration-resistant prostate cancer. These combinations appear to have clinical promise, and further investigation of the potentially synergistic combination of radiotherapy and immunotherapy is continuing in clinical trials.

Clonotypic Diversification of Intratumoral T Cells Following Sipuleucel-T Treatment in Prostate Cancer Subjects

Sipuleucel-T is an autologous cellular therapy for asymptomatic, or minimally symptomatic, metastatic castrate-resistant prostate cancer, designed to stimulate an immune response against prostate cancer. In a recent clinical trial (NCT00715104), we found that neoadjuvant sipuleucel-T increased the number of activated T cells within the tumor microenvironment. The current analysis examined whether sipuleucel-T altered adaptive T-cell responses by expanding pre-existing T cells or by recruiting new T cells to prostate tissue. Next-generation sequencing of the T-cell receptor (TCR) genes from blood or prostate tissue was used to quantitate and track T-cell clonotypes in these treated subjects with prostate cancer. At baseline, there was a significantly greater diversity of circulating TCR sequences in subjects with prostate cancer compared with healthy donors. Among healthy donors, circulating TCR sequence diversity remained unchanged over the same time interval. In contrast, sipuleucel-T treatment reduced circulating TCR sequence diversity versus baseline as measured by the Shannon index. Interestingly, sipuleucel-T treatment resulted in greater TCR sequence diversity in resected prostate tissue in sipuleucel-T-treated subjects versus tissue of nonsipuleucel-T-treated subjects with prostate cancer. Furthermore, sipuleucel-T increased TCR sequence commonality between blood and resected prostate tissue in treated versus untreated subjects with prostate cancer. The broadening of the TCR repertoire within the prostate tissue supports the hypothesis that sipuleucel-T treatment facilitates the recruitment of T cells into the prostate. Our results highlight the importance of assessing T-cell response to immunotherapy both in the periphery and in tumor tissue. Cancer Res; 76(13); 3711-8. ©2016 AACR.

Sequencing of Sipuleucel-T and Androgen Deprivation Therapy in Men with Hormone-Sensitive Biochemically Recurrent Prostate Cancer: A Phase II Randomized Trial

Purpose: STAND, a randomized, phase II, open-label trial (NCT01431391), assessed sequencing of sipuleucel-T (an autologous cellular immunotherapy) with androgen deprivation therapy (ADT) in biochemically recurrent prostate cancer (BRPC) patients at high risk for metastasis. Experimental Design: Men with BRPC following prostatectomy and/or radiotherapy, a PSA doubling time ≤12 months, and no metastasis were enrolled. Patients were randomized (34/arm) to sipuleucel-T followed by ADT (started 2 weeks after sipuleucel-T completion), or ADT followed by sipuleucel-T (started 12 weeks after ADT initiation); ADT continued for 12 months in both arms. The primary endpoint was PA2024-specific T-cell response [enzyme-linked immunospot (ELISPOT)] over time. Results: PA2024-specific ELISPOT responses over time were similar between groups, except at week 6, where responses were higher with sipuleucel-T→ADT versus ADT→sipuleucel-T (P = 0.013). PA2024-specific T-cell proliferation responses, averaged across time points, were approximately 2-fold higher with sipuleucel-T→ADT versus ADT→sipuleucel-T (P = 0.001). PA2024-specific cellular and humoral responses and prostatic acid phosphatase–specific humoral responses increased significantly versus baseline (P < 0.001) and were maintained for 24 months (both arms). Median time-to-PSA recurrence was similar between arms (21.8 vs. 22.6 months, P = 0.357). Development of a PA2024-specific humoral response correlated with prolonged time-to-PSA progression (HR, 0.22; 95% CI, 0.08–0.67; P = 0.007). Sipuleucel-T with ADT was generally well tolerated. Conclusions: Sipuleucel-T→ADT appears to induce greater antitumor immune responses than the reverse sequence. These results warrant further investigation to determine whether this sequence leads to improved clinical outcomes, as well as the independent contribution of ADT alone in terms of immune activation. Clin Cancer Res; 23(10); 2451–9. ©2016 AACR.

A randomized phase II, open-label study of sipuleucel-T with concurrent or sequential abiraterone acetate (AA) in metastatic castrate-resistant prostate cancer (mCRPC).

114 Background: Sipuleucel-T and AA are both FDA approved for mCRPC. Given that androgen deprivation therapy is immunostimulatory, increased suppression of the androgen axis with AA could provide synergy in combination with sipuleucel-T; however, AA is given with prednisone (P), which may be immunosuppressive. In order to evaluate the impact of concurrent AA + P on product characteristics, a study of sipuleucel-T with concurrent or sequential AA + P was undertaken. METHODS Pts aged ≥18 yrs with asymptomatic or minimally symptomatic mCRPC, and ECOG PS 0/1 were randomized (1:1) to sipuleucel-T (3 infusions at approx 2-week intervals) with up to 26 weeks of AA + P (AA 1000mg QD + P 5mg BID) starting 1 day after the first sipuleucel-T infusion (concurrent arm) or at week 10 (sequential arm). The primary endpoint was cumulative CD54 upregulation (measure of antigen presenting cell activation); secondary and tertiary endpoints included CD54+cell and total nucleated cell (TNC) counts (measures of product potency), safety and efficacy. RESULTS 29 pts have been enrolled. 16 pts in the concurrent arm (A) and 13 pts in the sequential arm (B) have completed sipuleucel-T treatment at the time of this interim analysis (7 Sept 2012). 27/29 pts received all 3 infusions of sipuleucel-T; 2 pts (both arm A) received only 1 infusion due to insufficient TNC count (n=1) and disease progression 8 days after randomization (n=1). No significant differences in median cumulative CD54 upregulation (31.6 vs 36.6) and CD54+ count (1.9 vs 2.1 x109) were observed between arms A and B, respectively. Increased CD54 upregulation with the 2nd and 3rd treatments were indicative of a prime boost effect in both arms. Similarly, the TNC profile over time was similar for both arms. The overall incidence of adverse events (AEs) was similar in arms A (81%) and B (77%). Common all-grade AEs included muscle spasms (31% vs 23%), oral paresthesia (19% vs 31%), chills (31% vs 8%) and cough (19% vs 15%). CONCLUSIONS These data suggest that sipuleucel-T can be manufactured during treatment with AA + P with product potency and prime boost similar to that of sipuleucel-T alone. CLINICAL TRIAL INFORMATION NCT01487863.

Survival Outcomes of Sipuleucel-T Phase III Studies: Impact of Control-Arm Cross-Over to Salvage Immunotherapy

Control-arm patients from three prostate cancer clinical trials of sipuleucel-T (an autologous APC–based therapy) received APC therapy from their cryopreserved cells. Overall survival may have increased, which suggests that APC therapy may be more robust than estimated. Sipuleucel-T is an autologous cellular immunotherapy for asymptomatic/minimally symptomatic metastatic castrate-resistant prostate cancer (CRPC). After disease progression, control-arm patients on three double-blind, randomized phase III sipuleucel-T trials were offered, in nonrandomized open-label protocols, APC8015F, an autologous immunotherapy made from cells cryopreserved at the time of control manufacture. These exploratory analyses evaluated potential effects on survival outcomes associated with such treatment. Of 249 control-treated patients, 165 (66.3%) received APC8015F. We explored the effects of APC8015F on the overall survival (OS; Cox regression) of control-arm patients and treatment effects of sipuleucel-T versus control adjusted for APC8015F treatment [iterative parameter estimation model (IPE)]. The median time to first APC8015F infusion was 5.2 months (range, 1.8–33.1) after randomization and 2.2 months (0.5–14.6) after progression. After disease progression, median survival was longer for APC8015F-treated versus control-only treated patients [20.0 vs. 9.8 months; HR, 0.53; 95% confidence interval (CI), 0.38–0.74; P < 0.001]; however, baseline characteristics were more favorable for APC8015F-treated patients. Multivariate regression analyses identified lactate dehydrogenase, alkaline phosphatase, hemoglobin, ECOG status, age, and number of bone metastases as potential (P < 0.1) independent predictors of postprogression survival. After adjusting for these predictors, APC8015F (HR, 0.78; 95% CI, 0.54–1.11; P = 0.17) treatment trended toward improved survival. Estimated median OS benefit for sipuleucel-T versus control adjusted for APC8015F treatment was 3.9 months if APC8015F had no effect and was 8.1 months if APC8015F was equally as effective as sipuleucel-T. Exploratory analyses indicate that APC8015F treatment may have extended patient survival, suggesting the sipuleucel-T OS advantage in CRPC may be more robust than previously estimated. Cancer Immunol Res; 3(9); 1063–9. ©2015 AACR.

An analysis to quantify the overall survival (OS) benefit of sipuleucel-T accounting for the crossover in the control arm of the IMPACT study.

144 Background: Sipuleucel-T is an autologous cellular immunotherapy approved for the treatment of asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer (mCRPC). Our previous analyses on the effect of salvage crossover treatment with a product constructed from previously frozen cells (APC8015F) on OS in the control arms of mCRPC studies of sipuleucel-T suggested a positive treatment effect with salvage therapy (George DJ et al. JCO 2011;29:abstr 139). To quantify how treatment with APC8015F might have impacted the OS of the IMPACT study, we performed an exploratory analysis adjusting for the potential bias that salvage APC8015F might have had in estimating the OS advantage of sipuleucel-T. METHODS After objective disease progression, patients (pts) in the control arm were offered 3 infusions of APC8015F, an autologous immunotherapy made from cells cryopreserved at the time of control generation. A rank-preserving structural failure time (RPSFT) model, as previously described, was applied to adjust the sipuleucel-T treatment effect. RESULTS In the 512-pt IMPACT study, there was a 4.1-month median improvement in OS (25.8 vs 21.7 months) for sipuleucel-T compared to control (HR=0.78; 95% CI: 0.61, 0.98; p=0.032). 109/171 (64%) of control pts received APC8015F; other post-progression interventions were balanced. Median OS was 23.8 months for control pts receiving APC8015F and 11.6 months for control pts not receiving APC8015F. Using the RPSFT model, and assuming APC8015F was equally as effective as sipuleucel-T, the estimate of median OS for control was 18.0 months (HR=0.60, 95% CI: 0.41, 0.95), representing a 7.8-month median improvement in OS in favor of sipuleucel-T. Results from extensions of the RPFST model, where APC8015F is assumed to have less treatment effect than sipuleucel-T, will be presented. CONCLUSIONS Adjusting for a positive effect of APC8015F in the control arm resulted in a sipuleucel-T OS treatment benefit in the IMPACT study ranging from 4.1 to 7.8 months. These results support a greater treatment effect of sipuleucel-T than reported in the IMPACT study and should be factored into future studies without APC8015F crossover.

HER2 expression in patients (pts) with surgically resected urothelial cancer at high risk of recurrence screened for the phase II randomized, open-label trial of DN24-02, an autologous cellular immunotherapy targeting HER2.

292 Background: HER2 overexpression has been suggested as a poor prognostic factor in pts with high-risk urothelial carcinoma (UC). Published data note a wide range of HER2 overexpression in UC, with some reports showing <10% of cases and others exhibiting >50% of cases with ≥2+ HER2 expression by immunohistochemistry (IHC). NeuACT (N10-1; NCT01353222) is a phase 2 trial to determine whether DN24-02, an autologous cellular immunotherapy targeting HER2 based on the same platform used for sipuleucel-T, given as adjuvant therapy following surgical resection can prolong survival (Bajorin, et al. ASCO 2012). Here we report preliminary data for HER2 expression on primary tumor and positive lymph node samples from this study. METHODS Trial eligibility criteria include surgical resection of a primary UC, with either ≥pT2 or pN+ staging, and HER2 expression ≥1+ IHC. Surgical specimens are screened for HER2 expression by central pathology laboratory review and HER2 positivity is scored using the Dako HercepTest scoring system. RESULTS As of August 2012, tumor specimens from 61 pts have been screened for HER2 expression. Of these pts, 49 (80%; 95% CI: 68-89%) had a HER2 expression score of ≥1+ in the primary tumor, with 27 (44%) having ≥2+ score and 3 (5%) having a 3+ score. Twenty-three pts (38%) also had HER2 expression levels evaluated in tumor from involved lymph nodes. A total of 20 (87%; 95% CI: 66-97%) of these pts had a HER2 expression score of ≥1+ in the lymph nodes, with 12 (52%) having a ≥2+ score and 3 (15%) having a 3+ score. Two pts had primary tumor samples that expressed HER2 but were negative for HER2 expression in the lymph nodes submitted for analysis. CONCLUSIONS Although preliminary, a high frequency (≥80%) of HER2 expression score of ≥1+ in primary tumor and lymph node samples was observed. These data highlight the prevalence of HER2 protein expression in high-risk UC. Furthermore, the HER2 expression data are consistent with previously published data in pts with invasive UC. CLINICAL TRIAL INFORMATION NCT01353222.