CRM1 regulates androgen receptor stability and impacts DNA repair pathways in prostate cancer, independent of the androgen receptor

Among the known nuclear exportins, CRM1 is the most studied prototype. Dysregulation of CRM1 occurs in many cancers, hence, understanding the role of CRM1 in cancer can help in developing synergistic therapeutics. The study investigates how CRM1 affects prostate cancer growth and survival. It examines the role of CRM1 in regulating androgen receptor (AR) and DNA repair in prostate cancer. Our findings reveal that CRM1 influences AR mRNA and protein stability, leading to a loss of AR protein upon CRM1 inhibition. Furthermore, it highlights the involvement of HSP90 alpha, a known AR chaperone, in the CRM1-dependent regulation of AR protein stability. The combination of CRM1 inhibition with an HSP90 inhibitor demonstrates potent effects on decreasing prostate cancer cell growth and survival. The study further explores the influence of CRM1 on DNA repair proteins and proposes a strategy of combining CRM1 inhibitors with DNA repair pathway inhibitors to decrease prostate cancer growth. Overall, the findings suggest that CRM1 plays a crucial role in prostate cancer growth, and a combination of inhibitors targeting CRM1 and DNA repair pathways could be a promising therapeutic strategy.

Abstract 4345: Molecular pathology studies reveal PD1+ CD8 T cell density correlates with response to supraphysiological testosterone treatment in pre-treatment biopsies and MYC mRNA and protein correlate with response after treatment

While most patients with metastatic prostatic adenocarcinoma respond initially, nearly all develop resistance to multiple lines of androgen deprivation therapies. This is related to overexpression of the androgen receptor (AR), which is frequently driven by AR amplification. In some patients, increased AR renders tumor cells sensitive to high dose androgens which paradoxically inhibits their growth. Bipolar Androgen Therapy (BAT) was introduced in which patients with castration resistant prostate cancer (CRPC) are treated intermittently with high dose testosterone. This produces biochemical and objective responses, and may re-sensitize prostate cancer to subsequent second generation AR inhibitors. This study utilizes samples from a recently performed clinical trial for patients with CRPC that included sequential biopsies of soft tissue metastases before BAT and after 3 cycles of BAT and before patients were treated with nivolumab.Tumor cells were present in FFPE blocks for both the pretreatment and C4D1 time points for 24 of the patients. These FFPE samples were stained using a recently validated iterative multiplex IHC assay containing 6 antibodies including: CD3 (T cells), CD4 (Helper T Cells), CD8 (Cytotoxic T Cells), PD1 (T Cell Checkpoint), FOXP3 (T-Reg cells), and Keratin 8 (epithelial cell marker). Biopsy slides were scanned after each round of staining and whole slide scans were imported into the HALO image analysis where they underwent color deconvolution, image registration and fusion. Regions of tumor were demarcated manually, and computerized automated image analysis was used to determine cell densities for 8 cell phenotypes (total CD3+, CD3+CD4+, CD3+CD8+, CD3+CD4+Foxp3+, CD3+CD4+PD1+, CD3+CD8+PD1+, CD3+CD4+PD1-, CD3+CD8+PD1-). There was a higher density of CD3+CD8+PD1+ cells in the pretreatment biopsies of men who responded (R) (to BAT) as compared with those who did not respond (NR)(p=0.015 Wilcoxon rank-sum test; mean 92.7 [R] vs 13.9 [NR]). The difference in R vs. NR was less and not significant in the CD3+CD8+PD1- population. There was a trend towards a higher density of CD3+CD4+PD1+ cells in the pretreatment samples in responders, but less so in the CD3+CD4+PD1- population. In the C4D1 biopsies, only CD3+ total cells were significantly higher in the R vs. NR (P=0.02), but the other phenotypes were not. We conclude that increased density of CD3+C8+PD1+, but not CD3+CD8+PD1- cells was present in pre-treatment biopsies in responders as compared with non-responders to BAT. These results indicate that men who are likely to respond to high dose testosterone treatment harbor tumors that are immunologically distinct prior to treatment than those men unlikely to respond. Additional spatial analysis and comparisons with RNAseq data will be presented.

Citation Format: Carolina Gomes Alexandre, Jessica Hicks, Tracy Jones, John T Isaacs, Kiara Bowers, Alyza Skist, Laura Sena, Jennifer Meyers, Emmanuel Antonarakis, David Sanin, Hanfei Qi, Samuel Denmeade, Mark Markowski, Srinivasan Yegnasubramanian, Angelo De Marzo. Molecular pathology studies reveal PD1+ CD8 T cell density correlates with response to supraphysiological testosterone treatment in pre-treatment biopsies and MYC mRNA and protein correlate with response after treatment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4345.

Phase II Randomized Study of Salvage Radiation Therapy Plus Enzalutamide or Placebo for High-Risk Prostate-Specific Antigen Recurrent Prostate Cancer After Radical Prostatectomy: The SALV-ENZA Trial

PURPOSE

We sought to investigate whether enzalutamide (ENZA), without concurrent androgen deprivation therapy, increases freedom from prostate-specific antigen (PSA) progression (FFPP) when combined with salvage radiation therapy (SRT) in men with recurrent prostate cancer after radical prostatectomy (RP).

PATIENTS AND METHODS

Men with biochemically recurrent prostate cancer after RP were enrolled into a randomized, double-blind, phase II, placebo-controlled, multicenter study of SRT plus ENZA or placebo (ClinicalTrials.gov identifier: NCT02203695). Random assignment (1:1) was stratified by center, surgical margin status (R0 v R1), PSA before salvage treatment (PSA ≥ 0.5 v < 0.5 ng/mL), and pathologic Gleason sum (7 v 8-10). Patients were assigned to receive either ENZA 160 mg once daily or matching placebo for 6 months. After 2 months of study drug therapy, external-beam radiation (66.6-70.2 Gy) was administered to the prostate bed (no pelvic nodes). The primary end point was FFPP in the intention-to-treat population. Secondary end points were time to local recurrence within the radiation field, metastasis-free survival, and safety as determined by frequency and severity of adverse events.

RESULTS

Eighty-six (86) patients were randomly assigned, with a median follow-up of 34 (range, 0-52) months. Trial arms were well balanced. The median pre-SRT PSA was 0.3 (range, 0.06-4.6) ng/mL, 56 of 86 patients (65%) had extraprostatic disease (pT3), 39 of 86 (45%) had a Gleason sum of 8-10, and 43 of 86 (50%) had positive surgical margins (R1). FFPP was significantly improved with ENZA versus placebo (hazard ratio [HR], 0.42; 95% CI, 0.19 to 0.92; P = .031), and 2-year FFPP was 84% versus 66%, respectively. Subgroup analyses demonstrated differential benefit of ENZA in men with pT3 (HR, 0.22; 95% CI, 0.07 to 0.69) versus pT2 disease (HR, 1.54; 95% CI, 0.43 to 5.47; Pinteraction = .019) and R1 (HR, 0.14; 95% CI, 0.03 to 0.64) versus R0 disease (HR, 1.00; 95% CI, 0.36 to 2.76; Pinteraction = .023). There were insufficient secondary end point events for analysis. The most common adverse events were grade 1-2 fatigue (65% ENZA v 53% placebo) and urinary frequency (40% ENZA v 49% placebo).

CONCLUSION

SRT plus ENZA monotherapy for 6 months in men with PSA-recurrent high-risk prostate cancer after RP is safe and delays PSA progression relative to SRT alone. The impact of ENZA on distant metastasis or survival is unknown at this time.

PSA provocation by bipolar androgen therapy may predict duration of response to first-line androgen deprivation: Updated results from the BATMAN study

BACKGROUND

Previously, we reported results from the Phase II BATMAN study (Bipolar Androgen Therapy for Men with Androgen-ablation Naïve prostate cancer). This study (NCT01750398) was designed to evaluate the safety and efficacy of a treatment regimen consisting of a 6-month lead in-phase of androgen deprivation therapy (ADT) followed by alternating 3-month intervals of bipolar androgen therapy (BAT) and ADT alone. Here we report > 5-year follow-up related to the duration of subsequent ADT, response to first-line androgen receptor inhibitors, safety, and survival in men with castration-sensitive prostate cancer treated on the BATMAN study.

METHODS

Univariate Cox regression was utilized to compare overall survival between Responders who achieved a prostate-specific antigen (PSA) level of <4 ng/ml and Non-Responders who achieved a PSA level of ≥4 ng/ml after BAT/ADT. Kaplan-Meier method and Cox regression were used to assess progression-free (PFS) and overall survival (OS) on BAT and on subsequent abiraterone or enzalutamide and on the association between PSA peak during BAT and each time to event outcome.

RESULTS

Over median follow-up of 95 months, the median PFS on ADT for the entire cohort was 47.8. Median OS has not been reached (NR). Median OS for Non-Responders is 43 months versus NR (not reached) for responders (hazard ratio [HR]: 0.176, p = 0.002). Post-BAT, the PSA50 and PSA90 responses to abiraterone or enzalutamide were 94.4% and 66.7%, respectively and median PFS was 20.6 months. Patients with peak PSA level of ≥9 ng/ml after BAT had median PFS of 20.6 months versus NR for those having PSA < 9 ng/ml (HR: 0.122, p < 0.001). Median OS was 79.6 months for patients with PSA peak of ≥9 ng/ml versus NR for those having PSA peak of <9 ng/ml (HR: 0.409, p = 0.131).

CONCLUSION

The use of BAT as part of first-line hormonal therapy strategy does not induce adversely affect long-term survival or induce any significant long-term adverse sequelae in patients with prostate cancer. Cycling BAT may extend the duration of ADT response and enhance response to subsequent androgen ablative therapies. The magnitude of BAT-provoked increase in PSA may predict duration of ADT response and warrants further study.

Abstract 653: Molecular pathology of metastatic prostatic adenocarcinoma treated with bipolar androgen therapy (BAT) reveals a correlation between MYC mRNA and protein

Molecular analysis of tissue samples from metastatic cancer lesions can improve our understanding of drug response and resistance. Since prostate cancer cells initially require androgen signaling through the androgen receptor (AR) for proliferation, the treatment of metastatic prostate cancer involves surgical or chemical castration. While most patients respond initially, nearly all develop acquired resistance to combined androgen blockade using both first and second line agents. This resistance is often related to overexpression of AR, which is frequently driven by AR gene amplification. In some patients, this increased AR appears to render tumor cells sensitive to high dose androgens in a manner that paradoxically inhibits their growth. Bipolar Androgen Therapy (BAT) was introduced several years ago at our institution in which patients with castration resistant prostate cancer (CRPC) are treated intermittently with high dose testosterone. Prior clinical trials have shown that BAT can produce biochemical and objective responses, and may re-sensitize prostate cancer to subsequent second generation AR inhibitors. To define the mechanism(s) by which BAT results in tumor regression, we performed a clinical trial (NCT03554317) for patients with CRPC that included biopsies of soft tissue metastases before BAT and after 3 cycles of BAT (C4D1). Up to four tissue cores were taken per biopsy with two cores for formalin fixation and paraffin embedding (FFPE) and the others snap frozen. Histologically viable tumor cells were present for both the pretreatment and C4D1 time points for 24 of the 42 enrolled patients. The FFPE samples were stained for H&E and by IHC for AR, MYC and Ki67. MYC and Ki67 IHC stained slides were subjected to quantitative image analysis using HALO software (Indica Labs). Adequate frozen tumor tissue was available for laser capture microdissection and adequate amounts of RNA were obtained from 15 patients with paired pretreatment and C4D1 biopsies. RNAseq libraries were prepared using the NuGEN Ovation RNA-Seq System V2 and barcoded libraries were sequenced to an average depth of &gt; 100 million reads per sample on an Illumina NovaSeq. Gene expression values were obtained with RSEM using Star aligner with GRCh38 (human). When comparing the C4D1 samples to the pretreatment samples, there were marked decreases in tumor MYC protein levels in approximately half of the treated patients, which was associated with decreased Ki67, decreased tumor volume, and prolonged progression-free survival on BAT. Using an image analysis computed H-SCORE for MYC, there was a strong correlation between MYC protein levels and MYC mRNA using RNAseq (r=0.81, p = 2.3 x 10-7). This indicates that MYC protein levels correlate with MYC mRNA and that reductions of MYC protein by BAT are likely related to reductions of MYC mRNA in clinical metastatic tissue samples.

Citation Format: Carolina Gomes Alexandre, Tracy Jones, Jessica L. Hicks, John T. Isaacs, Anuj Gupta, Alyza Skaist, Laura Sena, Jennifer Meyers, Emmanuel Antonarakis, Mark Markowski, Samuel Denmeade, Srinivasan Yegnasubramanian, Angelo Michael De Marzo. Molecular pathology of metastatic prostatic adenocarcinoma treated with bipolar androgen therapy (BAT) reveals a correlation between MYC mRNA and protein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 653.

Bipolar androgen therapy (BAT): A patient's guide

Bipolar androgen therapy (BAT) is a new treatment concept for men whose prostate cancer has become resistant to standard hormone-blocking therapy. Over the past decade, we have performed a series of clinical studies testing BAT in asymptomatic men with castration-resistant prostate cancer. The key findings from these clinical studies are that BAT (a) can be safely administered to asymptomatic patients with metastatic castrate-resistant prostate cancer; (b) does not produce symptomatic disease progression; (c) produces sustained prostate-specific antigen and objective responses in 30%-40% of patients; and (d) can resensitize and prolong response to subsequent antiandrogen therapy. The concept of BAT has generated significant interest from men with prostate cancer, their families, and their physicians. Here we provide a "Patient's Guide" that answers questions about BAT in a form that is accessible to patients, their families, and physicians. Our goal is to provide information to help patients make the most informed decisions they can regarding their prostate cancer treatment.

Abstract 2410: Supraphysiological androgens induce ferroptotic cell death in prostate cancer cells

Castration resistant prostate cancer (CRPC) first manifests as a sustained rise in the androgen-responsive gene, PSA, consistent with reactivation of a functioning androgen receptor (AR) axis. This observation led to the development of “second-line” therapies aimed at further blocking androgen/AR signaling. Unfortunately, resistance to these agents can also develop quickly. Paradoxically, several studies have suggested that the growth of AR-positive human CRPC cell lines may be inhibited by supraphysiologic levels of testosterone (SupT). These studies suggested that the adaptive reliance on AR signaling by CRPC cells becomes a therapeutic liability that can be exploited through the administration of SupT, which we termed as bipolar androgen therapy (BAT). Understanding how BAT works at the molecular and cellular levels might help in rationally combining BAT with other agents to achieve increased efficacy and tumor responses. Our data indicates that SupT induces autophagy mediated degradation of ferritin in prostate cancer (PCa) cells. Degradation of ferritin results in increase in labile iron pool increasing lipid peroxidation. Our data further indicates that SupT distinctly induces ferroptosis, a nonapoptotic regulated form of cell death induced by the accumulation of labile iron. Ferroptosis is thought to have tumor suppressing capabilities by clearing tumor cells via immune system activation. BAT has been discussed as a potential therapy for prostate cancer, but further research is needed to understand its full potential. Future combination of BAT with existing immunotherapeutics including immune checkpoint blockade may prove beneficial for treatment of CRPC.

Citation Format: Rajendra Kumar, Kavya Boyapati, Naiju Thomas, Deven Topiwala, Suthicha Kanacharoen, Olutosin Owoyemi, Max Coffey, Michael Carducci, Mark C. Markowski, Emmanuel S. Antonarakis, Drew Pardoll, Samuel Denmeade, Sushant K. Kachhap. Supraphysiological androgens induce ferroptotic cell death in prostate cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2410.

Abstract 5953: Regulation of androgen receptor stability by nuclear export protein CRM1

Import of ligand-bound androgen receptor (AR) into the nucleus occurs with the help of nuclear importin. Past studies have identified a nuclear export signal (NES) in AR. CRM1 (also called XPO1 or Exportin1) is a well-studied exportin that exports proteins and RNA from the nucleus to the cytoplasm. GTP-bound active Ran, CRM1, and the cargo protein form a ternary complex that is exported through the nuclear pore complex. Previous experimental data indicate that RanGTP plays a vital role in Prostate cancer (PCa) progression. Our analyses further suggest that patients who have overexpression of CRM1 and/or Ran have significantly decreased survival. These results indicate that nucleocytoplasmic transport is essential for prostate cancer progression and inhibiting CRM1 could selectively inhibit cancer cell growth. We demonstrate that CRM1 does not affect the nuclear export of AR protein. However, quite surprisingly, we provide novel evidence that CRM1 binds to AR mRNA and is also required for AR protein stability. Inhibiting CRM1 using CRM1 inhibitor results in a dose-dependent rapid loss of AR and AR-V7 splice variants in PCa cells. This observation opens up an entirely new avenue to therapeutically regulate AR signaling using CRM1 inhibitors.

Citation Format: Naiju Thomas, Rajendra Kumar, Deven Topiwala, Kavya Boyapati, Suthicha Kanacharoen, Michael Carducci, Samuel Denmeade, Sushant K. Kachhap. Regulation of androgen receptor stability by nuclear export protein CRM1 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5953.

An IL-2 proaerolysin fusion toxin that selectively eliminates regulatory t cells to enhance antitumor immune response

BACKGROUND

Recent success with immune-checkpoint inhibitors in some tumor types has highlighted the power of the immune system to control and eradicate human cancer cells. However, these therapies have demonstrated a limited activity in prostate cancer, which has a more immunosuppressive microenvironment that can be because of the presence of a variety of inhibitory cell types, such as myeloid-derived suppressor cells, mesenchymal stem cells, and regulatory T cells (Tregs). One strategy to improve the efficacy of immune-based therapies for prostate cancer is to selectively eliminate these immunosuppressive cells within the tumor microenvironment.

METHODS

We developed and characterized a chimeric protein consisting of the cytokine IL-2 fused to binding mutant of the highly toxic bacterial toxin proaerolysin (ie IL2-R336A).

RESULTS

The IL2-R336A fusion protein selectively kills immunosuppressive Tregs that express the IL-2 receptor while having little to no effect on cells negative for this target. IL2-R336A depleted Tregs in both tumor bearing and nontumor bearing mice. Tumor bearing mice vaccinated with a GMCSF-expressing CT-26 GVAX vaccine had reduced tumor growth when given IL2-R336A before vaccination. IL2-R336A also enhanced immune response to a model hemagglutinin antigen (HA) in HA-tolerized mice.

CONCLUSION

These results suggest that this IL2-R336A toxin may be a useful in improving the therapeutic efficacy of antitumor vaccines by enhancing the immune response against target tumor antigens.

Abstract 517: Supraphysiological androgens activate innate immune signaling in prostate cancer

Castration resistance prostate cancer (CRPC) first manifests as a sustained rise in the androgen-responsive gene, PSA, consistent with reactivation of a functioning androgen receptor (AR) axis. This observation led to the development of “second-line” therapies aimed at further blocking androgen/AR signaling. Unfortunately, resistance to these agents can also develop quickly. Paradoxically, several studies have suggested that the growth of AR-positive human CRPC cell lines may be inhibited by supraphysiologic levels of testosterone (SupT). These studies suggested that the adaptive reliance on AR signaling by CRPC cells becomes a therapeutic liability that can be exploited through the administration of SupT, which we termed as bipolar androgen therapy (BAT). Understanding how BAT works at the molecular and cellular levels might help in rationally combining BAT with other agents to achieve increased efficacy and tumor responses. Our data indicates that SupT induces DNA double strand breaks (DSBs) in prostate cancer (PCa) cells. Unrepaired DSBs induced by SupT are routed for specialized autophagic degradation, termed nucleophagy. We further show that SupT-induced autophagosomal DNA can activate cytoplasmic DNA sensing pathways and downstream innate immune signaling. Based on our findings, we propose that BAT engages the immune system to inhibit tumor growth. Future combination of BAT with existing immunotherapeutics including immune checkpoint blockade may prove beneficial for treatment of CRPC.

Citation Format: Janet Mendonca, Olutosin Owoyemi, Marc Rosen, Michael Carducci, Mark Markowski, Emmanuel Antonarakis, Drew Pardoll, Samuel Denmeade, Sushant K. Kachhap. Supraphysiological androgens activate innate immune signaling in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 517.

A phase II randomized trial of Observation versus stereotactic ablative RadiatIon for OLigometastatic prostate CancEr (ORIOLE)

Background

We describe a randomized, non-blinded Phase II interventional study to assess the safety and efficacy of stereotactic ablative radiotherapy (SABR) for hormone-sensitive oligometastatic prostate adenocarcinoma, and to describe the biology of the oligometastatic state using immunologic, cellular, molecular, and functional imaging correlates. 54 men with oligometastatic prostate adenocarcinoma will be accrued. The primary clinical endpoint will be progression at 6 months from randomization with the hypothesis that SABR to all metastases will forestall progression by disrupting the metastatic process. Secondary clinical endpoints will include local control at 6 months post-SABR, toxicity and quality of life, and androgen deprivation therapy (ADT)-free survival (ADT-FS). Further fundamental analysis of the oligometastatic state with be achieved through correlation with investigational ¹⁸F–DCFPyL PET/CT imaging and measurement of circulating tumor cells, circulating tumor DNA, and circulating T-cell receptor repertoires, facilitating an unprecedented opportunity to characterize, in isolation, the effects of SABR on the dynamics of and immunologic response to oligometastatic disease.

Methods/design

Patients will be randomized 2:1 to SABR or observation with minimization to balance assignment by primary intervention, prior hormonal therapy, and PSA doubling time. Progression after 6 months will be compared using Fisher’s exact test. Hazard ratios and Kaplan-Meier estimates of progression free survival (PFS), ADT free survival (ADT-FS), time to locoregional progression (TTLP) and time to distant progression (TTDP) will be calculated based on an intention-to-treat. Local control will be assessed using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria. Withdrawal from the study prior to 6 months will be counted as progression. Adverse events will be summarized by type and grade. Quality of life pre- and post- SABR will be measured by Brief Pain Inventory.

Discussion

The ORIOLE trial is the first randomized, non-blinded Phase II interventional study in the North America evaluating the safety and efficacy of SABR in oligometastatic hormone-sensitive prostate cancer. Leading-edge laboratory and imaging correlates will provide unique insight into the effects of SABR on the oligometastatic state.

Trial registrations

ClinicalTrials.gov Identifier: NCT02680587.

URL of Registry: https://clinicaltrials.gov/show/NCT02680587

Date of Registration: 02/08/2016.

Date of First Participant Enrollment: 05/23/2016.

Mipsagargin, a novel thapsigargin-based PSMA-activated prodrug: results of a first-in-man phase I clinical trial in patients with refractory, advanced or metastatic solid tumours

Background:

Mipsagargin (G-202; (8-O-(12-aminododecanoyl)-8-O-debutanoyl thapsigargin)-Asp-γ-Glu-γ-Glu-γ-GluGluOH)) is a novel thapsigargin-based targeted prodrug that is activated by PSMA-mediated cleavage of an inert masking peptide. The active moiety is an inhibitor of the sarcoplasmic/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) pump protein that is necessary for cellular viability. We evaluated the safety of mipsagargin in patients with advanced solid tumours and established a recommended phase II dosing (RP2D) regimen.

Methods:

Patients with advanced solid tumours received mipsagargin by intravenous infusion on days 1, 2 and 3 of 28-day cycles and were allowed to continue participation in the absence of disease progression or unacceptable toxicity. The dosing began at 1.2 mg m⁻² and was escalated using a modified Fibonacci schema to determine maximally tolerated dose (MTD) with an expansion cohort at the RP2D. Plasma was analysed for mipsagargin pharmacokinetics and response was assessed using RECIST criteria.

Results:

A total of 44 patients were treated at doses ranging from 1.2 to 88 mg m⁻², including 28 patients in the dose escalation phase and 16 patients in an expansion cohort. One dose-limiting toxicity (DLT; Grade 3 rash) was observed in the dose escalation portion of the study. At 88 mg m⁻², observations of Grade 2 infusion-related reaction (IRR, 2 patients) and Grade 2 creatinine elevation (1 patient) led to declaration of 66.8 mg m⁻² as the recommended phase II dose (RP2D). Across the study, the most common treatment-related adverse events (AEs) were fatigue, rash, nausea, pyrexia and IRR. Two patients developed treatment-related Grade 3 acute renal failure that was reversible during the treatment-free portion of the cycle. To help ameliorate the IRR and creatinine elevations, a RP2D of 40 mg m⁻² on day 1 and 66.8 mg m⁻² on days 2 and 3 with prophylactic premedications and hydration on each day of infusion was established. Clinical response was not observed, but prolonged disease stabilisation was observed in a subset of patients.

Conclusions:

Mipsagargin demonstrated an acceptable tolerability and favourable pharmacokinetic profile in patients with solid tumours.

Abstract 2067: Attacking prostate cancer with a prodrug-doped cellular Trojan horse

Prostate cancer is the second leading cause of cancer-related deaths in American men. Despite considerable advances in prostate cancer research, there is a major need for a systemic delivery platform that efficiently targets anti-cancer drugs to sites of disseminated prostate cancer while minimizing host toxicity. Human mesenchymal stem cells (MSCs) are excellent candidates for cell-based drug delivery since they display tropism towards cancer sites and clinical studies have demonstrated that hundreds of millions of allogeneic human MSCs can be safely administered intravenously without adverse effects in a variety of pathological settings. Furthermore, we have previously documented that MSCs can be detected in radical prostatectomy tissue from men with prostate cancer. In this proof-of-concept study, human MSCs were loaded with poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating the macromolecule G114, a thapsigargin-based prostate specific antigen (PSA)-activated prodrug. G114-loaded MPs were successfully internalized by MSCs without impacting MSC viability, followed by sustained release of G114 as an intact prodrug from loaded cells. Moreover, G114 released from G114 MP-loaded MSCs is selectively toxic to the PSA-secreting prostate cancer cell line, LNCaP. Finally, G114 MP-loaded MSCs inhibited tumor growth when co-inoculated with CWR22 prostate cancer xenografts, suggesting that cell-based delivery of G114 does not compromise potency of the prodrug in vitro or in vivo. We envision that this MSC-based platform may be developed into an effective, systemic ‘Trojan Horse’ therapy for the targeted delivery of therapeutic agents to sites of metastatic prostate cancer.

Citation Format: Nathaniel Brennen, Oren Levy, Edward Han, David Marc Rosen, Juliet Musabeyezu, Helia Safaee, Sudhir Ranganath, Jessica Ngai, Martina Heinelt, Sandrine Billett, Neil Bhowmick, Samuel Denmeade, Jeffrey Karp, John Isaacs. Attacking prostate cancer with a prodrug-doped cellular Trojan horse. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2067.

Abstract 699: Mesenchymal stem cells (MSC) as cell-based vectors for PSA-activated proaerolysin to sites of prostate cancer

Mesenchymal stem cells (MSC) traffic to sites of inflammation, such as those commonly found at sites of prostate and other cancers. Using multi-parameter flow cytometry, our group has shown that MSCs represent 0.01-1.1% of the total cells present at sites of primary prostate cancer (PCa). Allogeneic MSCs have been safely administered to &gt;1000 patients in over 350 clinical trials worldwide for a variety of diseases. Coupled with their ability to evade the immune system, this suggests that allogeneic MSCs can be used as cell-based delivery vectors for anti-cancer agents.

Towards this goal, a method has been developed to load MSCs with PLGA microparticles (MP) encapsulating PSA-activated proaerolysin. Proaerolysin is a highly potent (low pM) bacterial pore-forming toxin that selectively kills PSA-expressing cells in a proliferation-independent manner, which is critical due to the low proliferative index of PCa. Proaerolysin has been modified using site-directed mutagenesis to replace the wildtype activation domain with a PSA cleavage sequence. Though prodrug delivery will be enriched at cancer sites using MSC ‘Trojan horses’, entrapment in non-malignant tissue, such as the lung, following systemic administration is expected and must be addressed; here, using a prodrug strategy. Importantly, enzymatically active PSA is only present in the prostate and at sites of PCa, including metastases. Circulating PSA is inactive due to covalent binding to serum protease inhibitors. Therefore, toxicity to non-target tissues will be minimized through both selective delivery and prodrug activation.

The prodrug is released from the MPs in a controlled manner over at least a 1 week period in vitro. Hemolysis assays in the presence of MP-conditioned supernatant demonstrated that MP fabrication does not neutralize drug toxicity. Furthermore, incubation of LNCaP (PSA+) and PC3 (PSA-) cells with MP-conditioned supernatant demonstrates selective toxicity to PSA-expressing cells at low nM concentrations. MP internalization by MSCs has been confirmed using both flow cytometry and confocal microscopy. Chitosan-modification of the MPs permitted increased loading of MSCs (100 ug/mL of MPs). For long-term development, preclinical studies such as these have raised the question of tumor homing efficiency in humans. Therefore, an ongoing FDA-approved first-in-man pre-prostatectomy clinical trial to quantify the number of systemically-delivered allogeneic MSCs that traffic to sites of primary PCa has been initiated. BEAMing (digital PCR) technology will be used to accurately quantify donor MSCs based on differential SNP profiles (detection threshold: ≥0.01%). Data from this trial will be used to determine the amount of prodrug-loaded MPs necessary to deliver per MSC to achieve a therapeutic effect. This data will subsequently be used in ongoing animal studies to model clinical relevance in efficacy studies prior to further translation.

Citation Format: W. Nathaniel Brennen, Oren Levy, Sudhir Ranganath, Michael Schweizer, Marc Rosen, Sandrine Billet, Neil Bhowmick, Samuel Denmeade, Jeffrey Karp, John Isaacs. Mesenchymal stem cells (MSC) as cell-based vectors for PSA-activated proaerolysin to sites of prostate cancer. [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 699. doi:10.1158/1538-7445.AM2014-699

Abstract 16: Mutational analysis of PSA reveals its zymogen intrinsic activity

Prostate-specific antigen (PSA) is a well-known biomarker of prostatic abnormality. It is a serine protease that is expressed at high concentrations with high enzymatic activity in the prostatic tumor microenvironment. Recommendations by the US preventive task against PSA-based screening for prostate cancer, has confounded the role played by PSA in prostate cancer. Thus, to more accurately differentiate between clinically significant and insignificant prostate cancer, there has been a new focus on understanding the composition of PSA in serum to identify new potential PSA-based biomarkers. In this regard, we generated a series of PSA-derived mutants that would reliably represent zymogen, conformationally active, or enzymatically active states. Here we present a description of our methodology and a characterization of the isolated recombinant proteins.

Starting with the PSA wildtype cDNA (WT), site-directed mutagenesis was used to generate a panel of recombinant variants, including those that prohibited cleavage of the PSA prodomain (R24A), disabled its enzymatic activity (S213A), facilitated the conversion to active conformation by using a cell surface protease (FR) and auto-processed by its intrinsic activity (QY). FLAG and HIS epitopes were placed on the N- and C-terminals respectively to facilitate the harvesting of purified enzyme. The HEK293T cell line was used to express the variants into serum-free media prior to subsequent purification. Biochemical methods were employed to determine the purity and structural composition of the proteins. Finally, the proteolytic activity of the isolated proteins was examined using a PSA-selective fluorogenic substrate, known PSA-cleavable proteins, and physiologically relevant inhibitors.

A novel panel of PSA variants was successfully purified and characterized. The zymogen form of PSA was shown to exhibit enzymatic activity, and this intrinsic activity was further evident in its potential to self-activate the PSA_QY variant, which exhibited the greatest enzymatic activity of all the variants. As predicted, the catalytic serine at residue 213 proved essential for enzymatic function, with all activity extinguished even in the context of a conformationally active protein. We further show that both enzymatic activity and active conformation is necessary for inhibitor binding.

We have analyzed the zymogen, active conformation, or enzymatically active states of PSA, and have found the zymogen form to have enzymatic activity. These data suggest that different forms of PSA may potentially have different biological functions. These PSA variants will prove useful for a variety of applications, including structure/function studies, improved standards for biomarker development, and in depth investigations into the role PSA plays in reproduction and disease.

Citation Format: Niquiche M. Sangster-Guity, Samuel Denmeade, Simon Williams. Mutational analysis of PSA reveals its zymogen intrinsic activity . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 16. doi:10.1158/1538-7445.AM2013-16

The change of PSA doubling time and its association with disease progression in patients with biochemically relapsed prostate cancer treated with intermittent androgen deprivation

BACKGROUND

We sought to determine the change of PSA doubling time (PSADT) and its association with disease progression during intermittent androgen deprivation (IAD) therapy for prostate cancer.

METHODS

Data were retrospectively analyzed in 96 patients with biochemically relapsed prostate cancer (BRPC) treated with IAD since 1995. IAD consisted of LHRH-agonists ± antiandrogen given usually at PSA threshold (ng/ml) of 10-20, for 6-9 months. Cycles were repeated until the development of castration resistance. Mixed effects model was used to study PSADT change over cycles. Multivariate cox regression model was used to identify outcome-associated variables.

RESULTS

Patients received a mean of 2.8 treatment cycles over a mean follow-up time of 71 months. Fifty-seven (59%) remain on treatment and 39 (41%) developed PSA refractoriness (n = 8) or positive scans (n = 31). First off treatment interval PSADT (median 2.3 months) was significantly shorter than the baseline (median 7.34) but remained stable in subsequent cycles. Off treatment interval PSADT adjusted for testosterone recovery (median 3.7) was significantly longer than that based on all PSA determinations (median 2). Factors associated with disease progression were pre-treatment PSADT (≥6 vs. <6), first off treatment interval PSADT (≥3 vs. <3), and PSA nadir during the first treatment interval (<0.1 vs. ≥0.1).

CONCLUSIONS

During IAD for BRPC, PSADT becomes shorter, and is associated with testosterone recovery. PSADT before treatment and during the first off treatment interval is associated with disease progression. If prospectively validated these data may guide treatment with IAD and clinical trial design.

Lenalidomide in nonmetastatic biochemically relapsed prostate cancer: results of a phase I/II double-blinded, randomized study

PURPOSE

To evaluate the safety and activity of 6 months of treatment with lenalidomide at 5 or 25 mg/d in nonmetastatic biochemically relapsed prostate cancer.

EXPERIMENTAL DESIGN

Sixty men with non-castrate, nonmetastatic, biochemically relapsed prostate cancer were stratified by prostate-specific antigen (PSA) doubling time, surgery/radiation therapy, prior androgen deprivation therapy (ADT), and randomized to lenalidomide 5 mg (n = 26) or 25 mg/d (n = 34) for 3 weeks repeated monthly for 6 months or until dose-limiting toxicity or disease progression. Toxicity was evaluated monthly, and PSAs and X-rays/scans every 6 months. Study size was determined to detect a progression rate of 40% at 6 months in either arm with 85% power (compared with a rate of 80% in the population receiving no treatment). Changes in PSA slopes were calculated using the regression of the log PSA for each patient before and during the initial 6 months and compared by t test.

RESULTS

Baseline variables were balanced between arms. Grade 3/4 toxicity rates were 12% (n = 3) with 5 mg and 29% (n = 10) with 25 mg (P = 0.1), most commonly neutropenia (five patients, all on 25 mg). Two patients per arm had thromboembolic events. The change in PSA slope was greater with 25 mg versus 5 mg [-0.172 (-0.24 to -0.11) versus -0.033 (-0.11 to 0.04); P = 0.005]. With a mean follow-up of 31.4 months (range 14-44), five patients on 25 mg and one patient on 5 mg remain on the study.

CONCLUSIONS

Lenalidomide has acceptable toxicity and is associated with long-term disease stabilization and PSA declines. Randomized studies evaluating conventional clinical disease end points in this patient population are planned.

HIF-1alpha and calcium signaling as targets for treatment of prostate cancer by cardiac glycosides

Prostate cancer possesses its unique feature of low proliferation rate and slow growth. Ca(2+)-induced apoptosis is not dependent on cell cycle progression and targeting this pathway could circumvent the problems encountered using current cytotoxic chemotherapies for prostate cancer. Hypoxia-inducible factor 1alpha (HIF-1alpha) is another novel cancer drug target and inhibitors of hypoxia-response pathway are being developed. Digoxin and other cardiac glycosides, known inhibitors of the alpha-subunit of sarcolemmal Na(+)K(+)-ATPase, were recently found to block tumor growth via the inhibition of HIF-1alpha synthesis. Thus, cardiac glycosides disrupt two important cellular pathways and, therefore, may be useful as an anticancer therapy. This review will focus on HIF-1alpha and calcium signaling as novel cancer drug targets in prostate cancer. The possible application of digoxin and other cardiac glycosides in cancer therapeutics especially in prostate cancer is discussed.

A Thapsigargin Prodrug Produces Sustained Growth Inhibition and Substantial Regression of Human Breast Cancers In Vivo with Minimal Host Toxicity

Background: Thapsigargin (TG) is a cytotoxic natural product isolated in high yields from the plant Thapsia garganica. In the NCI 60 Cancer Cell Line screen, TG has a GI50 of ∼10-10 M which compares favorably with agents such as paclitaxel (10-8 M) and doxorubicin (10-7 M) in this assay. TG is a non-cell type specific cytotoxin that kills cells in a proliferation independent manner via its potent inhibition of a critical intracellular protein, the Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase (SERCA) pump. Sustained inhibition of the SERCA pump by TG produces an elevation of intracellular calcium to micromolar levels which induces apoptosis via activation of the ER stress response and release of apoptotic factors from the mitochondria. TG has no therapeutic index in vivo with an LD100 of 0.2 mg/kg.Methods: In order to create a theraputic index that would allow for sytemic therapy of human breast cancer we generated prodrugs by coupling water soluble acidic amino acid containing peptides to a potent analog of thapsigargin, (12Aminododecanoyl)-8-O debutanoylthapsigargin (12ADT). In addition to solubilization, the peptide also serves to mask the cytotoxicity of the TG analog until it is released by specific active proteases present within tumor sites. One of these prodrugs (G202) was selected for further in vivo evaluation based on its solubility and ability to be hydrolyzed by the carboxypeptidase Prostate-Specific Membrane Antigen (PSMA). PSMA is membrane protein that is highly expressed by normal and malignant prostate epithelial cells. PSMA, however, is also expressed by the neovasculature within most solid tumors, but not by normal tissue vasculature. In this study we evaluated the toxicity and efficacy of this PSMA-activated thapsigargin prodrug against human MCF-7 breast cancer xenografts.Results: In preliminary studies with prostate cancer xenografts we determined that a single intravenous dose of 56 mg/kg G202 formulated in propylene glycol/Solutol could be administered safely without acute toxicity. Mice bearing MCF-7 xenografts were thus treated with one, two or three doses of 56 mg/kg G202. Three doses produced significant tumor regressions and prolonged growth inhibition but was associated with toxicity whereas a single dose of G202 had no discernible toxicity but produced only transient growth inhibition. In contrast, two consecutive doses of G202 produced only transient weight loss and resulted in significant tumor regression and sustained growth inhibition, with complete responses observed in a subset of animals. High levels (∼5 μM) of the active drug 12ADT-Asp were measurable in the tumor tissue 96 hrs post injection while negligible hydrolysis of G202 was observed in plasma. Discussion: The effectiveness of G202 against a panel of ER positive and negative breast cancer xenografts is currently being evaluated. On the basis of this encouraging preliminary data continued clinical development of G202 as therapy for metastatic breast cancer appears warranted.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5074.

Lack of an effect of high dose isoflavones in men with prostate cancer undergoing androgen deprivation therapy

PURPOSE

The profound hypogonadism due to androgen deprivation therapy for prostate cancer results in complications such as sexual dysfunction, poor quality of life, vasomotor symptoms and altered cognition. Since estrogen is associated with cardiovascular risks, phytoestrogens are being increasingly evaluated as a potential treatment for these adverse effects. We evaluated the effects of high dose isoflavones, equivalent to that consumed by Asian populations, on the aforementioned consequences of androgen deprivation therapy.

MATERIALS AND METHODS

A total of 33 men undergoing androgen deprivation therapy for prostate cancer were enrolled in this randomized, double-blind, placebo controlled, 12-week pilot trial. Participants were randomly assigned to receive 20 gm soy protein containing 160 mg total isoflavones (17) vs taste matched placebo, that is 20 gm whole milk protein (16). The study was performed at a tertiary care center in the United States.

RESULTS

At baseline the groups were well matched in demographic parameters, sleep quality, cognition and overall quality of life. However, men in the isoflavone group had a higher baseline prevalence of hot flashes and poor intercourse satisfaction compared to those on placebo. At 12 weeks there were no significant differences between the 2 groups in any outcome measure.

CONCLUSIONS

This pilot study of high dose isoflavones in androgen deprived men showed no significant improvement in cognition, vasomotor symptoms or any other aspect of quality of life measures compared to placebo. Future studies should use variable doses of isoflavones for a longer period before ruling out beneficial isoflavone effects in this population.

A randomized double blind phase I-II study to determine the tolerability/efficacy of two different doses of lenalidomide (L), CC- 5013, in biochemically relapsed (BR) prostate cancer (PC) patients (pts) (M0) after local treatment (LT)

5130

Background: BR following LT is common in PC with no defined standard treatment. Lenalidomide (L) is an immunomodulatory agent with anti-angiogenic and direct antitumor effects. Methods: This trial was designed to evaluate a dose-effect relationship of L in BR PC. Pts were randomized to either 5 or 25 mg/day(d), PO, d 1–21 (28-d cycles); then stratified by PSADT (< 3, 3–8.9, ≥ 9 mos), LT and prior ADT. Eligible pts had: rising PSA (≥1 ng/mL), M0 disease, testosterone > 150 ng/mL, adequate bone marrow, renal, and hepatic function. Baseline and Q 2 mos PSA's were processed after Q 6 mos of L, along with CT and bone scan. Toxicity exams were Q mo. Primary endpoints are safety and progression after 6 mo of L (defined by a confirmed ↑ in PSA > 25% over the baseline value or mets). Secondary endpoints are changes of slopes in PSA related to pharmacokinetics (pk). A sample size of 30 pts/arm provides an 85% power to detect a PSA progression rate of 40% (compared to 80% predicted ) with a Type I error = 0.05 (Fishers exact test). Results: 59 pts were entered July 20, 2006-December 31, 2008. Pooled data from the 2 arms: median: age 64 (50–81), ECOG PS 0, baseline PSA 9.3 ng/ml (1.3–92.8 ng/ml). 16 pts had PSADT <3 mos, 26 from 3–8.9 mos, and 17 ≥ 9 mos. Median: F/U on all 59 pts is 351 + d (9 +-887+d); # cycles = 6 (1–30). Thus far, 44/59 pts completed 6 cycles of L (1 had PD, 6 stopped L due to toxicity, 8 too early). 22 /44 who completed 6 mos of L remained on L > 6 mos ( 7+-30+ mos); including 7 pts ≥ 24 mos. Of 44 pts, blinded evaluation of PSA's at 6 mos: 4 pts had ≥ 50% ↓, 22 had stable PSA,17 had PD, 1 too early . Rash was DLT. Other Gr toxicities: appendicitis, abd pain, neck pain, venous thrombolic disease, fatigue, pruritus. Conclusions: Preliminary data prior to unblinding the study treatment arms, from pooled data, suggest that L may be administered > 6 mos with acceptable toxicity, and is associated with PSA declines and long term stabilization in pts with BR. Supported by a grant from Celgene Corporation. Data coordination infrastructure is supported by the Prostate Cancer Foundation and The James Stine research fund.

[Table: see text]

Phase I trial with a combination of docetaxel and 153Sm- EDTMP in patients (pts) with castration-resistant metastatic prostate cancer (mCRPC)

5155

Background: Bone targeted therapy holds great promise for improving outcomes in mCRPC. Preclinical data strongly supported biological synergism of docetaxel (Tax) and 153Sm-EDTMP (Sm) in mCRPC. Concurrent Tax and Sm regimens were reported feasible and tolerable in phase I studies. This study was designed to evaluate toxicity and preliminary efficacy of 2 cycles (12 wks/cycle, C) of concomitant standard dose/schedule of Sm plus Q3 wks schedule of Tax in mCRPC. Methods: mCRPC pts with progressive bone metastases were treated in 4 cohorts ( CH). Previous Tax and palliative RT to bone was admissible. Dose escalation of Tax was implemented if no DLT was observed in the preceding CH. Tax doses (on days 1, 22, per 12 wk cycle) were given as follows: CH 1- 50mg/m2 (C1 and 2); CH 2–75mg/m2 (C1) and 50mg/m2 (C2); CH3 - 75mg/m2 (C1 and 2) and CH4 ( Tax day 1, 22, 43 per 12 wk C) 75mg/m2 (C1 and 2). Sm was administered on days 2 (Q12 wks X 2) at dose of 1 mCi/kg/cycle (max. of 2 cycles). Disease status was assessed (with bone /CT scans and PSA) after every cycle. Results: Thirteen pts with progressive bone metastases were enrolled. Three had prior Tax and 3 had prior palliative radiation. Thirteen pts received total 20 cycles in 4 cohorts. Toxicity was primarily hematological. There were total 34 episodes Grade 3/4 neutropenia with a median 7 (range 7 -14) days to recovery to ≤ grade1. Tax dose was reduced to 50% in 2 CH4 pts at C2. Only 1 DLT G3 thrombocytopenia occurred on cohort 4 with duration of 9 wks. Median baseline PSA was 100.4 ng/ml (range 8.6 - 1064), 9/13 (69%) pts had PSA>50% decrease. Median time to disease progression was 147 days (range 72 days - 10 months+); 6/13 (46%) pts had stable/improved bone scans at 6 months and 8/8 (100%) symptomatic pts had improvement in pain. Conclusions: Concurrent 6-month administration of 2 and possibly 3 full dose /standard schedule of Tax with 2 full doses of Sm is feasible with reversible bone marrow suppression. The combination may provide additional clinical benefits for mCRPC pts with extensive bone metastasis.

No significant financial relationships to disclose.

Phase II multicenter study of abiraterone acetate (AA) plus prednisone therapy in docetaxel-treated castration-resistant prostate cancer (CRPC) patients (pts): Impact of prior ketoconazole (keto)

5048

Background: AA is a potent blocker of CYP17, required for synthesis of testosterone in the testes, adrenals, and prostate tissue. Study objectives included confirming AA antitumor activity and safety in multicenter setting, describing changes in ECOG PS, and comparing keto-naïve pts to keto-exposed pts. Methods: The 58 pts had progressive, metastatic CRPC and had failed hormonal therapy and up to two cytotoxic regimens, including docetaxel. AA (1,000 mg QD) and prednisone (5mg BID) were administered daily, the registration trial regimen. 56/58 pts had available data. Results: Baseline demographics: median age - 69.0 (44–86) yrs; median PSA - 151.00 (10.0–3846.0) ng/mL; ECOG 0 (n = 23), 1 (n = 30), 2 (n = 2), missing (n = 1); median prior hormonal therapies were 4 and chemo 1; 24 pts had prior keto, 32 pts were keto-naïve and 2 pts had no data on keto exposure. 45% pts had total maximal PSA decline ≥50%. Total maximal PSA decline (≥30%, ≥50% and ≥90%) in prior keto vs. keto-naïve pts was observed respectively, in: 10 (42%) vs. 20 (63%) pts; 8 (33%) vs. 17 (53%); 1 (4%) vs. 10 (31%). From 32 pts with ECOG 1 or 2, 16 pts (50%, 95% CI 32–68) improved (PS 1 to 0 in 14 pts, PS 2 to 1 in 1 pt; PS 2 to 0 in 1 pt); 39 pts (64% of total 58 pts) maintained PS. Median time to PSA progression was 169 days (95% CI 82–200): keto-naïve-198 days, prior keto-99 days. The majority of AA-related adverse events (AEs) were grade 1–2. No AA-related grade 4 AE was noted. Conclusions: Abiraterone acetate was well-tolerated and produced anti-tumor activity in heavily pretreated pts, as evidenced by PSA declines and improved PS. Incidence of mineralocorticoid-related AEs (HTN or hypokalemia) was reduced with the addition of low-dose prednisone. The keto-naïve post-docetaxel CRPC population was selected for the ongoing phase III pivotal study to confirm these results.

[Table: see text]

Phase I trial of docetaxel (D) plus samarium153 (Sm 153) in patients (pts) with hormone refractory prostate cancer (HRPC)

15547

Background: Bone targeted approaches hold great promise for improving outcomes in HRPC. Docetaxel (D) and samarium 153 (Sm153 ) have individually demonstrated a clinical benefit and preclinical data strongly support biological synergism in HRPC. Preclinical data suggests that 24 hour after a dose of D, there is maximum G2M arrest. This results in the accumulation of cells in the most radiosensitive phase of the cell cycle. This phase I trial was designed to evaluate toxicity and preliminary efficacy of combined D and Sm153 administered sequentially in advanced HRPC. Methods: HRPC pts progressing after anti-androgen withdrawal; = 2 prior chemotherapy regimens; acceptable bone marrow, renal and hepatic function were eligible. Planned D treatment in 4 cohorts (N=3/cohort) includes: Cohort 1: D 50mg/m2 IV on days 1, 22, 91, and 112; cohort 2: D 75mg/m2 IV on days 1 and 22 followed by 50mg/m2 IV on days 91 and 112; cohort 3: D 75mg/m2 IV on days 1 and 22 followed by 75mg/m2 IV on days 91 and 112; cohort 4: D 75 mg/m2 IV on days 1, 22, 42, 91, 112, and 133. Sm 153 (1.0 mi/Kg) is administered IV days 2 and 92 of each cycle. Cycles are repeated Q 12 wks (max 2 cycles). The endpoint for this trial is dose limiting toxicity and maximal tolerated dose. Results: From 5/11/05 - 1/7/07 ten pts were enrolled. Median: age 69.5 yrs (range 58–76), ECOG performance status 1 (range 0–1), baseline PSA 76.65 ng/ml (range 9.6–1064 ng/ml ), prior hormonal manipulations 3 (range1–6). Three pts had prior taxotere and 3 pts had prior palliative RT. All had bone metastases and 2 also had soft tissue disease. Five pts completed 2 cycles of treatment as planned. Five pts had 1 cycle (one pt is on treatment, 3 pts had PD and 1 had prolonged grade 1 thrombocytopenia =3 wks). Nine of 10 pts had reversible grade 3 / 4 neutropenia (1 pt had reversible episode of neutropenia with fever). Seven of 7 symptomatic pts had improvement in pain. Four of 10 of pts had a 50 % decline in PSA level lasting = 4 weeks; no soft tissue disease responses. Conclusions: Our preliminary data suggest that Q 3 wk D and Q 3 month Sm153 may be administered simultaneously at full doses in extensively pretreated HRPC pts, with acceptable toxicity and significant activity. This study is supported by a grant from sanofi- aventis and Sm153 is provided by Cytogen.

No significant financial relationships to disclose.

A phase II evaluation of imatinib mesylate (G) in stage M0 prostate cancer (PC) patients (pts) on hormonal therapy (HT) with evidence of biochemical relapse

14612

Background: Imatinib mesylate (Gleevec, G) is a potent inhibitor of the tyrosine kinases and other signaling mediated events. Preclinical models suggest that G inhibits platelet derived growth factor (PDGF) and stem cell factor (SCF) which are important for prostate cancer growth. This trial was designed to evaluate the safety and efficacy of G in PCA pts on HT with stage M0 disease. Methods: Eligible PCA pts included: stage M0 disease with rising PSA levels while on hormonal therapy, no prior chemotherapy. Planned treatment included G 400 mg PO BID given up to a maximum of 12 months. The statistical endpoint for this trial was the% of pts with a ↓ in prostate specific antigen (PSA) ≥ 50% lasting ≥ 4 wks. A 2 stage trial was designed where the study would terminate if the% of pts meeting the endpoint was not convincingly > 30% with 5% chance for error. Pts with a > 50% rise in PSA from baseline were removed from study. Follow-up included monthly toxicities and PSA (specimens frozen/stored until completion of each 3 months of therapy). Results: From 10/1/02–10/11/04, nine pts were enrolled. Pt characteristics included median: age of 67 years (range 52–80), ECOG performance status of 0 (range 0–1), baseline PSA of 29.6 ng/ml (range 2.69–39.52), # prior hormonal manipulations of 3 (1–5). Prior local therapies included: 1 status post (s/p) RP alone, 2 s/p RT alone, 2 s/p neoadjuvant HT plus RP, 2 s/p neoadjuvant HT plus RT. Two pts had no prior local therapy. Two pts had prior salvage RT, 1 had prior palliative RT. Eight of 9 pts evaluable for response and toxicity. One patient never received treatment. None of the pts had a decline 50% decline in PSA level lasting ≥ 4 weeks. Three of 8 pts (38%) had rapid increases in PSA and 4/8 pts (50%) developed metastatic disease after 3 months of therapy. Only one pt completed 12 months of planned therapy. Grade 3/4 toxicities included: fatigue (25%), rash (25%), arthralgias (12.5%), peripheral edema (25%), depression (12.5%), necessitating dose delays and/or discontinuation of G in 4/8 pts (50%). Conclusions: These data suggest significant toxicity and low clinical benefit. Further evaluation of Gleevec in this pt population is not warranted.

No significant financial relationships to disclose.

A phase II trial of temozolomide and IFN-alpha in patients with advanced renal cell carcinoma

The combination of temozolomide (TEM) and interferon-alpha (IFN-alpha) previously demonstrated a 30% response rate in metastatic melanoma. A single institution, phase II trial evaluating the efficacy of TEM/IFN in patients with advanced renal cell carcinoma (RCC) was conducted. Safety and tumor response were the main outcomes. Eligible patients received 200 mg/m(2)/day TEM orally on days 1-5 every 28 days, with IFN 2.5 million U/m(2)/day subcutaneously (s.c.) three alternate days/week for days 1-15 first cycle, then 5 million U/m(2)/day s.c. 3 alternate days/week throughout each 28-day cycle. Efficacy was evaluated every 8 weeks, and dose-limiting toxicities (DLTs) were treated with dose reductions of the culprit drug. Sixteen patients (ages 37-67) were initially enrolled. Of the 14 evaluable patients, there was one minor response. Best response was stable disease, with 7 patients remaining on study for > or =6 months. Five were alive for more than 2 years, and 2 remain alive at 45 and 50 months after enrollment. DLTs included TEM-induced myelosuppression and IFN-induced fever/chills. Other toxicities were mild to moderate (grades 1-3). The combination of TEM/IFN proved quite tolerable. This regimen appears inactive in terms of response in this population with poor prognosis, but the patients with stable disease > or =6 months remain of interest.

Thapsigargin analogues for targeting programmed death of androgen-independent prostate cancer cells

A number of analogues of thapsigargin, a selective inhibitor of the sarco-endoplasmic reticulum Ca2+-ATPases have been synthesized. In all of the prepared analogues the butanoyl residue at O-8 has been replaced with a residue containing an aromatic amine. The amine can be used as an anchoring point for attaching a peptide group sensitive to the proteolytic enzyme, prostate specific antigen, secreted by prostate cancer cells. Like thapsigargin, the analogues are capable of elevating the cytoplasmic Ca2+ concentration approximately sevenfold when tested at effective cytotoxic doses. The analogues in which the 8-O-butanoyl group has been replaced with 3-(4-aminophenyl)propanoyl or 4-aminocinnamoyl were found potently to induce programmed cell death of the prostate cancer cells.