Survival outcomes of real world patients with metastatic hormone-sensitive prostate cancer who do not achieve optimal PSA response with intensified androgen deprivation therapy with docetaxel or androgen receptor pathway inhibitors

INTRODUCTION

In patients with metastatic hormone-sensitive prostate cancer (mHSPC) undergoing intensified androgen deprivation therapy (ADT), not achieving an optimal PSA response, defined as PSA nadir >0.2 ng/ml (PSAsubOR) has been associated with worse survival outcomes in clinical trials (1)(10)(11). Here, we externally evaluate, the impact of optimal PSA response on survival outcomes in these patients and provide absolute PFS and OS measures in those with PSAsubOR in the context of ADT intensification in real world setting.

METHODS

In this retrospective study, all consecutive patients with mHSPC who underwent intensified ADT treated at our institution, and whose outcomes data were available, were included. We classified patients based on their PSA nadir on treatment: those with a on treatment PSAOR (PSA nadir ≤0.2 ng/ml) versus PSAsubOR.

RESULTS

A total of 205 patients were eligible: 136 (66.3%) patients achieved PSAOR versus 69 (33.7%) patients had PSAsubOR. Patients who experienced a PSAOR had significantly improved PFS and OS from the start of intensified ADT versus who did not: PFS was not reached (NR) versus 11 months (hazard ratio (HR) 0.20, P < 0.001) and OS was NR versus 38.9 months (HR 0.21, P < 0.001). Survival outcomes were poor with PSAsubOR regardless of intensification with docetaxel or an ARPI (absolute PFS and OS measures for each group are provided in the text).

CONCLUSION

Our study is the first to explore the negative impact of PSAsubOR in patients with mHSPC undergoing intensified ADT in the real-world setting, and is the first to provide absolute PFS and OS in patients with PSAsubOR receiving ADT intensification with ARPIs or docetaxel outside of clinical trial setting. These data will aid with prognostication, patient counseling, and for designing future clinical trials for patients with PSAsubOR.

Health-related quality of life in patients with metastatic hormone-sensitive prostate cancer treated with androgen receptor signaling inhibitors: the role of combination treatment therapy

BACKGROUND

While the addition of androgen receptor signaling inhibitors (ARSIs) to androgen deprivation therapy (ADT) results in better of overall survival in patients with metastatic hormone-sensitive prostate cancer (mHSPC), information regarding health related quality of life (HR-QoL) is sparse. We aimed at summarizing current evidence on the impact of ARSIs on HR-QoL.

METHODS

We performed a systematic review of the published literature on PubMed/EMBASE, Web of Science, SCOPUS, and the Cochrane libraries between January 2011 and April 2022. We included only phase III randomized controlled trials (RCT), which were selected according to the PRISMA guidelines. We aimed at evaluating differences in HR-QoL, assessed by validated patient reported outcomes instruments. We analyzed global scores and sub-domains such as sexual functioning, urinary symptoms, bowel symptoms, pain/fatigue, emotional and social/family wellbeing. We reported data descriptively.

RESULTS

Six RCTs were included: two used enzalutamide with ADT as intervention arms (ARCHES, ENZAMET); one used apalutamide with ADT (TITAN); two abiraterone acetate and prednisone (AAP) with ADT (STAMPEDE, LATITUDE); and one darolutamide with ADT (ARASENS). Enzalutamide or AAP with ADT increase overall HR-QoL in comparison with ADT alone, ADT with first generation nonsteroideal anti-androgens or ADT with docetaxel, whereas apalutamide and darolutamide with ADT maintain HR-QoL similarly to ADT alone or ADT with docetaxel, respectively. Time to first deterioration of pain was longer with combination therapy with enzalutamide, AAP or darolutamide, but not with apalutamide. No worsening of emotional wellbeing was reported from the addition of ARSIs to ADT than ADT alone.

CONCLUSIONS

The addition of ARSIs to ADT in mHSPC tends to increase overall HR-QoL and prolong time to first deterioration of pain/fatigue compared with ADT alone, ADT with first generation nonsteroideal anti-androgens, and ADT with docetaxel. ARSIs show a complex interaction with remaining HR-QoL domains. We advocate a standardization of HR-QoL measurement and reporting to allow further comparisons.

Drug-drug interaction potential among patients with nonmetastatic castration-resistant prostate cancer (nmCRPC) treated with novel androgen receptor inhibitors

BACKGROUND

Nonmetastatic castration-resistant prostate cancer (nmCRPC) patients are often older and use concurrent medications that increase the potential for drug-drug interactions (pDDIs). This study assessed pDDI prevalence in real-world nmCRPC patients treated with apalutamide, darolutamide, or enzalutamide.

RESEARCH DESIGN AND METHODS

Castrated prostate cancer patients without metastases prior to androgen receptor inhibitor initiation were identified retrospectively via Optum Clinformatics Data Mart claims data (8/2019-3/2021). The top 100 concomitant medications were assessed for pDDIs.

RESULTS

Among 1,515 patients (mean age: 77 ± 8 years; mean Charlson Comorbidity Index: 3 ± 3), 340 initiated apalutamide, 112 darolutamide, and 1,063 enzalutamide. Common concomitant medication classes were cardiovascular (80%) and central nervous system (52%). Two-thirds of the patients received ≥5 concomitant medications; 30 (30/100 medications) pDDIs were identified for apalutamide and enzalutamide each and 2 (2/100 medications) for darolutamide. Most pDDIs had risk ratings of C or D, but four for apalutamide were rated X. Approximately 58% of the patients on apalutamide, 5% on darolutamide, and 54% on enzalutamide had ≥1 identified pDDI.

CONCLUSIONS

Results showed a higher frequency of pDDIs in patients receiving apalutamide and enzalutamide vs darolutamide. The impact of these could not be determined retrospectively. DDI risk should be carefully evaluated when discussing optimal therapy for patients with nmCRPC.

A meta-analysis on overall survival and safety outcomes in patients with nonmetastatic castration-resistant prostate cancer treated with novel hormonal agents

Several novel androgen receptor (AR)-inhibitors have been introduced for nonmetastatic castration-resistant prostate cancer (nmCRPC) treatment, with the improvement of survival outcomes which need to be balanced against the risk of adverse events. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating enzalutamide, apalutamide and darolutamide in nmCRPC patients, to assess overall survival (OS), incidence and risk of adverse drug events, adverse-events-related death and adverse-events-related treatment discontinuation. We selected three RCTs (SPARTAN, PROSPER and ARAMIS). New hormonal agents administration resulted in better OS, despite the increased risk of several any grade and grade 3-4 adverse events. In the decision-making process, careful evaluation of expected adverse events, patients' comorbidities and maintenance of quality of life are mandatory.

2,4-dienoyl-CoA reductase regulates lipid homeostasis in treatment-resistant prostate cancer

Despite the clinical success of Androgen Receptor (AR)-targeted therapies, reactivation of AR signalling remains the main driver of castration-resistant prostate cancer (CRPC) progression. In this study, we perform a comprehensive unbiased characterisation of LNCaP cells chronically exposed to multiple AR inhibitors (ARI). Combined proteomics and metabolomics analyses implicate an acquired metabolic phenotype common in ARI-resistant cells and associated with perturbed glucose and lipid metabolism. To exploit this phenotype, we delineate a subset of proteins consistently associated with ARI resistance and highlight mitochondrial 2,4-dienoyl-CoA reductase (DECR1), an auxiliary enzyme of beta-oxidation, as a clinically relevant biomarker for CRPC. Mechanistically, DECR1 participates in redox homeostasis by controlling the balance between saturated and unsaturated phospholipids. DECR1 knockout induces ER stress and sensitises CRPC cells to ferroptosis. In vivo, DECR1 deletion impairs lipid metabolism and reduces CRPC tumour growth, emphasizing the importance of DECR1 in the development of treatment resistance.

TBCRC 032 IB/II Multicenter Study: Molecular Insights to AR Antagonist and PI3K Inhibitor Efficacy in Patients with AR+ Metastatic Triple-Negative Breast Cancer

PURPOSE

Preclinical data demonstrating androgen receptor (AR)-positive (AR+) triple-negative breast cancer (TNBC) cells are sensitive to AR antagonists, and PI3K inhibition catalyzed an investigator-initiated, multi-institutional phase Ib/II study TBCRC032. The trial investigated the safety and efficacy of the AR-antagonist enzalutamide alone or in combination with the PI3K inhibitor taselisib in patients with metastatic AR+ (≥10%) breast cancer.

PATIENTS AND METHODS

Phase Ib patients [estrogen receptor positive (ER+) or TNBC] with AR+ breast cancer received 160 mg enzalutamide in combination with taselisib to determine dose-limiting toxicities and the maximum tolerated dose (MTD). Phase II TNBC patients were randomized to receive either enzalutamide alone or in combination with 4 mg taselisib until disease progression. Primary endpoint was clinical benefit rate (CBR) at 16 weeks.

RESULTS

The combination was tolerated, and the MTD was not reached. The adverse events were hyperglycemia and skin rash. Overall, CBR for evaluable patients receiving the combination was 35.7%, and median progression-free survival (PFS) was 3.4 months. Luminal AR (LAR) TNBC subtype patients trended toward better response compared with non-LAR (75.0% vs. 12.5%, P = 0.06), and increased PFS (4.6 vs. 2.0 months, P = 0.082). Genomic analyses revealed subtype-specific treatment response, and novel FGFR2 fusions and AR splice variants.

CONCLUSIONS

The combination of enzalutamide and taselisib increased CBR in TNBC patients with AR+ tumors. Correlative analyses suggest AR protein expression alone is insufficient for identifying patients with AR-dependent tumors and knowledge of tumor LAR subtype and AR splice variants may identify patients more or less likely to benefit from AR antagonists.

Orally Bioavailable Androgen Receptor Degrader, Potential Next-Generation Therapeutic for Enzalutamide-Resistant Prostate Cancer

PURPOSE

Androgen receptor (AR)-targeting prostate cancer drugs, which are predominantly competitive ligand-binding domain (LBD)-binding antagonists, are inactivated by common resistance mechanisms. It is important to develop next-generation mechanistically distinct drugs to treat castration- and drug-resistant prostate cancers.

EXPERIMENTAL DESIGN

Second-generation AR pan antagonist UT-34 was selected from a library of compounds and tested in competitive AR binding and transactivation assays. UT-34 was tested using biophysical methods for binding to the AR activation function-1 (AF-1) domain. Western blot, gene expression, and proliferation assays were performed in various AR-positive enzalutamide-sensitive and -resistant prostate cancer cell lines. Pharmacokinetic and xenograft studies were performed in immunocompromised rats and mice.

RESULTS

UT-34 inhibits the wild-type and LBD-mutant ARs comparably and inhibits the in vitro proliferation and in vivo growth of enzalutamide-sensitive and -resistant prostate cancer xenografts. In preclinical models, UT-34 induced the regression of enzalutamide-resistant tumors at doses when the AR is degraded; but, at lower doses, when the AR is just antagonized, it inhibits, without shrinking, the tumors. This indicates that degradation might be a prerequisite for tumor regression. Mechanistically, UT-34 promotes a conformation that is distinct from the LBD-binding competitive antagonist enzalutamide and degrades the AR through the ubiquitin proteasome mechanism. UT-34 has a broad safety margin and exhibits no cross-reactivity with G-protein-coupled receptor kinase and nuclear receptor family members.

CONCLUSIONS

Collectively, UT-34 exhibits the properties necessary for a next-generation prostate cancer drug.

Apalutamide and overall survival in non-metastatic castration-resistant prostate cancer

BACKGROUND

In the SPARTAN study, compared with placebo, apalutamide added to ongoing androgen deprivation therapy significantly prolonged metastasis-free survival (MFS) and time to symptomatic progression in patients with high-risk non-metastatic castration-resistant prostate cancer (nmCRPC). Overall survival (OS) results at the first interim analysis (IA1) were immature, with 104 of 427 (24%) events required for planned final OS analysis. Here, we report the results of a second pre-specified interim analysis (IA2).

METHODS

One thousand two hundred and seven patients with nmCRPC were randomized 2 : 1 to apalutamide (240 mg daily) or placebo. The primary end point of the study was MFS. Subsequent therapy for metastatic CRPC was permitted. When the primary end point was met, the study was unblinded. Patients receiving placebo who had not yet developed metastases were offered open-label apalutamide. At IA2, pre-specified analysis of OS was undertaken, using a group-sequential testing procedure with O'Brien-Fleming-type alpha spending function. Safety and second progression-free survival (PFS2) were assessed.

RESULTS

Median follow-up was 41 months. With 285 (67% of required) OS events, apalutamide was associated with an improved OS compared with placebo (HR 0.75; 95% CI 0.59-0.96; P = 0.0197), although the P-value did not cross the pre-specified O'Brien-Fleming boundary of 0.0121. Apalutamide improved PFS2 (HR 0.55; 95% CI 0.45-0.68). At IA2, 69% of placebo-treated and 40% of apalutamide-treated patients had received subsequent life-prolonging therapy for metastatic CRPC. No new safety signals were observed.

CONCLUSION

In patients with nmCRPC, apalutamide was associated with a 25% reduction in risk of death compared with placebo. This OS benefit was observed despite crossover of placebo-treated patients and higher rates of subsequent life-prolonging therapy for the placebo group.

Pharmacokinetic Profile, Safety, and Tolerability of Clascoterone (Cortexolone 17-alpha propionate, CB-03-01) Topical Cream, 1% in Subjects With Acne Vulgaris: An Open-Label Phase 2a Study

Clascoterone (cortexolone 17α-propionate, CB-03-01) 1% cream, a topical, androgen receptor (AR) inhibitor under investigation for the treatment of acne vulgaris, is rapidly metabolized to cortexolone in human plasma. The primary objectives of this study were to determine the pharmacokinetic (PK) properties and adrenal suppression potential of clascoterone topical cream, 1% in subjects with acne vulgaris. Study Design: This study was an open-label, multicenter study in 42 subjects ≥12 years of age with moderate-to-severe acne (Grade 3-4 on the Investigator’s Global Assessment [IGA]), on the face, chest and/or back. Cohort 1(>18 years of age) and Cohort 2 (12-18 years of age) applied clascoterone topical cream, 1% twice daily (BID) for 14 days. Primary safety endpoints included hypothalamic-pituitary-adrenal (HPA) axis response to cosyntropin via a Cosyntropin Stimulation Test (CST) upon screening (day 1) and at day 14 (HPA axis suppression was defined as a post-stimulation serum cortisol level <18 μg/dL at day 14); and PK evaluation including concentration-time profiles of clascoterone and cortexolone in plasma—PK parameters were determined using “non-compartmental” analysis. Secondary safety endpoints included clinical laboratory testing, local and systemic adverse events (AEs), physical examination/vital signs, and electrocardiogram (ECG). Results: 42 subjects (Cohort 1=20, Cohort 2= 22) enrolled. Cohort 1 was comprised of 15 females (15/20, 75%) and 5 males (5/20, 25%), non-Hispanic/Latino (20/20, 100%), mean age is 24.4 years. Cohort 2 was comprised of 12 females (12/22, 54.5%) and 10 males (10/22, 45.5%), non-Hispanic/Latino (21/22, 95.5%), and mean age is 15.6 years. Three subjects (3/42,7%), 1 adult and 2 adolescents, demonstrated an abnormal HPA axis response with post-stimulation serum cortisol levels ranging from 14.9 to 17.7 μg/dL at day 14. All returned to normal HPA axis function, four weeks after day 14. None showed clinical evidence of adrenal suppression. Clascoterone plasma concentrations achieved PK steady-state by day 5. Clascoterone systemic exposure was similar between both cohorts. At steady-state, plasma concentrations increased ~1.8 to 2.1 fold versus first dose with mean (coefficient of variation [CV] %) maximum plasma concentrations of 4.4 ng/mL (67%) and 4.6 ng/mL (103%) in Cohort 1 and Cohort 2, respectively. Cortexolone plasma concentrations trended below the lower limit of quantitation (0.5 ng/mL) in both cohorts. Local skin reactions (LSRs) were mostly mild, with only one moderate case of pruritus. There were nine AEs categorized as follows: definitely related (N=2), probably related (N=4), unlikely/not related (N=3), to clascoterone. Conclusion: This study demonstrates the safety and tolerability of clascoterone topical cream, 1% in adolescents and adults with acne vulgaris treated BID for 14 consecutive days. J Drugs Dermatol. 2019;18(6):563-568.

The LACOG-0415 phase II trial: abiraterone acetate and ADT versus apalutamide versus abiraterone acetate and apalutamide in patients with advanced prostate cancer with non-castration testosterone levels

BACKGROUND

Testosterone suppression is the standard treatment for advanced prostate cancer, and it is associated with side-effects that impair patients' quality of life, like sexual dysfunction, osteoporosis, weight gain, and increased cardiovascular risk. We hypothesized that abiraterone acetate with prednisone (AAP) and apalutamide, alone or in combination, can be an effective hormonal therapy also possibly decreasing castration-associated side effects.

METHODS

Phase II, open-label, randomized, efficacy trial of abiraterone acetate plus prednisone (AAP) and Androgen Deprivation Therapy (ADT) versus apalutamide versus the combination of AAP (without ADT) and apalutamide. Key eligibility criteria are confirmed prostate adenocarcinoma; biochemical relapse after definitive treatment (PSA ≥ 4 ng/ml and doubling time less than 10 months, or PSA ≥ 20 ng/ml); newly diagnosed locally advanced or metastatic prostate cancer; asymptomatic to moderately symptomatic regarding bone symptoms. Patients with other histology besides adenocarcinoma or previous use of hormonal therapy or chemotherapy were excluded.

DISCUSSION

There is an urgent need to study and validate regimens such as new hormonal agents that may add benefit to castration with an acceptable safety profile. We aim to evaluate if apalutamide in monotherapy or in combination with AAP is an effective and safety hormonal treatment that can spare patients of androgen deprivation therapy.

TRIAL REGISTRATION

This trial was registered in ClinicalTrials.gov on October 16, 2017, under Identifier: NCT02867020.

Targeting the androgen receptor and overcoming resistance in prostate cancer

PURPOSE OF REVIEW

Prostate cancer (PCa) is diagnosed in one out of every nine men and is the second leading cause of cancer death among men. Although therapies targeting the androgen receptor (AR) are highly effective, development of resistance is universal and remains a major therapeutic challenge. Nonetheless, signaling via AR is frequently maintained despite standard androgen-signaling inhibition. We review the current understanding of mechanisms of resistance as well as therapeutic approaches to improving treatment of PCa via targeting of the AR.

RECENT FINDINGS

Resistance to AR-targeting therapies may be mediated by several mechanisms, including amplification, mutation, and alternative splicing of AR; intratumoral androgen synthesis; activation of alternative signaling pathways; and in a minority of cases, emergence of AR-independent phenotypes. Recent trials demonstrate that intensification of androgen blockade in metastatic castration-sensitive PCa can significantly improve survival. Similar strategies are being explored in earlier disease states. In addition, several other cellular signaling pathways have been identified as mechanisms of resistance, offering opportunities for cotargeted therapy. Finally, immune-based approaches are in development to complement AR-targeted therapies.

SUMMARY

Targeting the AR remains a critical focus in the treatment of PCa.

An open-label, multicenter, phase Ib study investigating the effect of apalutamide on ventricular repolarization in men with castration-resistant prostate cancer

PURPOSE

Phase Ib study evaluating the effect of apalutamide, at therapeutic exposure, on ventricular repolarization by applying time-matched pharmacokinetics and electrocardiography (ECG) in patients with castration-resistant prostate cancer. Safety of daily apalutamide was also assessed.

METHODS

Patients received 240 mg oral apalutamide daily. Time-matched ECGs were collected via continuous 12-lead Holter recording before apalutamide (Day - 1) and on Days 1 and 57 (Cycle 3 Day 1). Pharmacokinetics of apalutamide were assessed on Days 1 and 57 at matched time points of ECG collection. QT interval was corrected for heart rate using Fridericia correction (QTcF). The primary endpoint was the maximum mean change in QTcF (ΔQTcF) from baseline to Cycle 3 Day 1 (steady state). Secondary endpoints were the effect of apalutamide on other ECG parameters, pharmacokinetics of apalutamide and its active metabolite, relationship between plasma concentrations of apalutamide and QTcF, and safety.

RESULTS

Forty-five men were enrolled; 82% received treatment for ≥ 3 months. At steady state, the maximum ΔQTcF was 12.4 ms and the upper bound of its associated 90% CI was 16.0 ms. No clinically meaningful effects of apalutamide were reported for heart rate or other ECG parameters. A concentration-dependent increase in QTcF was observed for apalutamide. Most adverse events (AEs) (73%) were grade 1-2 in severity. No patients discontinued due to QTc prolongation or AEs.

CONCLUSION

The effect of apalutamide on QTc prolongation was modest and does not produce a clinically meaningful effect on ventricular repolarization. The AE profile was consistent with other studies of apalutamide.

Phase 1 study of seviteronel, a selective CYP17 lyase and androgen receptor inhibitor, in women with estrogen receptor-positive or triple-negative breast cancer

PURPOSE

Seviteronel (INO-464) is an oral, selective cytochrome P450c17a (CYP17) 17,20-lyase (lyase) and androgen receptor inhibitor with in vitro and in vivo anti-tumor activity. This open-label phase 1 clinical study evaluated safety, tolerability, pharmacokinetics (PK), and activity of once-daily (QD) seviteronel in women with locally advanced or metastatic TNBC or ER+ breast cancer.

METHODS

Seviteronel was administered in de-escalating 750, 600, and 450 mg QD 6-subject cohorts. The 750 mg QD start dose was a phase 2 dose determined for men with castration-resistant prostate cancer in (Shore et al. J Clin Oncol 34, 2016). Enrollment at lower doses was initiated in the presence of dose-limiting toxicities (DLTs). The primary objective of this study was to determine seviteronel safety, tolerability, and MTD. The secondary objectives included description of its PK in women and its initial activity, including clinical benefit rate at 4 (CBR16) and 6 months (CBR24).

RESULTS

Nineteen women were enrolled. A majority of adverse events (AEs) were Grade (Gr) 1/2, independent of relationship; the most common were tremor (42%), nausea (42%), vomiting (37%), and fatigue (37%). Four Gr 3/4 AEs (anemia, delirium, mental status change, and confusional state) deemed possibly related to seviteronel occurred in four subjects. DLTs were observed at 750 mg (Gr 3 confusional state with paranoia) and 600 mg (Gr 3 mental status change and Gr 3 delirium) QD, with none at 450 mg QD. The recommended phase 2 dose (RP2D) was 450 mg QD, and at the RP2D, 4 of 7 subjects reached at least CBR16 (2 TNBC subjects and 2 ER+ subjects achieved CBR16 and CBR24, respectively); no objective tumor responses were reported.

CONCLUSIONS

Once-daily seviteronel was generally well tolerated in women with and 450 mg QD was chosen as the RP2D.

Plumbagin improves the efficacy of androgen deprivation therapy in prostate cancer: A pre-clinical study

BACKGROUND

Plumbagin is a candidate drug for the treatment of prostate cancer. Previous observations indicated that it may improve the efficacy of androgen deprivation therapy (ADT). This study evaluates the effectiveness of treatment with combinations of plumbagin and alternative strategies for ADT in mouse models of prostate cancer to support its clinical use.

METHODS

Plumbagin was administered per oral in a new sesame oil formulation. Standard toxicology studies were performed in rats. For tumor growth studies, mouse prostate cancer cell spheroids were placed on top of grafted prostate tissue in a dorsal chamber and allowed to form tumors. Mice were separated in various treatment groups and tumor size was measured over time by intra-vital microscopy. Survival studies were done in mice after injection of prostate cancer cells in the prostate of male animals. Androgen receptor (AR) levels were analyzed by Western blot from prostate cancer cells treated with plumbagin.

RESULTS

Plumbagin caused a decrease in AR levels in vitro. In mice, plumbagin at 1 mg/kg in sesame oil displayed low toxicity and caused a 50% tumor regression when combined with castration. The combination of plumbagin with various forms of chemical ADT including treatment with a GnRH receptor agonist, a GnRH receptor antagonist, or CYP17A1 inhibitors, outperformed ADT alone, increasing mouse survival compared to the standard regimen of castration alone. In contrast, the combination of plumbagin with AR antagonists, such as bicalutamide and enzalutamide, showed no improvement over AR antagonists alone. Thus, plumbagin is effective in combination with drugs that prevent the synthesis of testosterone or its conversion to dihydrotestosterone, but not with drugs that bind to AR.

CONCLUSION

Plumbagin significantly improves the effect of ADT drugs currently used in the clinic, with few side effects in mice.

Phase 1 study of darolutamide (ODM-201): a new-generation androgen receptor antagonist, in Japanese patients with metastatic castration-resistant prostate cancer

PURPOSE

This trial assessed the safety, pharmacokinetics, and efficacy of darolutamide (ODM-201), a new-generation nonsteroidal androgen receptor antagonist, in Japanese patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

In this open-label, nonrandomized, two-cohort, dose-escalating phase 1 study, Japanese patients with mCRPC were enrolled after a screening period. In the single-dose period (≈1 week), darolutamide was administered at 300 mg (Cohort 1) or 600 mg (Cohort 2) on day -5 (fasting state) and day -2 (fed condition). In the subsequent multiple-dose period (fed condition), patients received darolutamide 300 mg twice daily (Cohort 1) or 600 mg twice daily (Cohort 2) for 12 weeks. Primary endpoints: evaluate safety and pharmacokinetics of darolutamide.

RESULTS

Of 12 patients enrolled, 9 received darolutamide (Cohort 1, n = 3; Cohort 2, n = 6). All 9 patients experienced ≥1 treatment-emergent adverse event (TEAE; majority Grade 1/2). Incidence of drug-related TEAEs (DR-TEAEs) was 44% (all grades; n = 4); most common DR-TEAE was decreased appetite (22%), and 1 serious DR-TEAE (Grade 3 nausea) was observed. No Grade ≥4 DR-TEAEs or new safety signals were observed. C max and AUC (0-t last) were dose-dependent; pharmacokinetics of each dose appeared to be linear over time. Prostate-specific antigen response was observed in 11% (1/9) of patients. Compared with fasting status, geometric mean C max increased 2.5-fold after 300 mg and 2.8-fold after 600 mg; geometric mean AUC (0-t last) increased 2.5-fold after both doses under fed conditions.

CONCLUSIONS

Darolutamide was well tolerated at the examined doses in Japanese patients with mCRPC, without differences in safety and pharmacokinetics relative to Western patients.

Impact of Therapy on Genomics and Transcriptomics in High-Risk Prostate Cancer Treated with Neoadjuvant Docetaxel and Androgen Deprivation Therapy

Purpose: The combination of docetaxel chemotherapy and androgen deprivation therapy (ADT) has become a standard treatment for patients with metastatic prostate cancer. The recently accrued phase III CALGB 90203 trial was designed to investigate the clinical effectiveness of this treatment approach earlier in the disease. Specimens from this trial offer a unique opportunity to interrogate the acute molecular response to docetaxel and ADT and identify potential biomarkers.Experimental Design: We evaluated baseline clinical data, needle biopsies, and radical prostatectomy (RP) specimens from 52 (of 788) patients enrolled on CALGB 90203 at one high volume center. Pathology review, tumor and germline-targeted DNA sequencing (n = 72 genes), and expression profiling using NanoString platform (n = 163 genes) were performed to explore changes in critical prostate cancer pathways linked to aggression and resistance.Results: Three of 52 patients had only microfocal residual cancer at prostatectomy. The most common alterations included TMPRSS2-ERG fusion (n = 32), TP53 mutation or deletion (n = 11), PTEN deletion (n = 6), FOXA1 (n = 6), and SPOP (n = 4) mutation, with no significant enrichment in posttreated specimens. We did not observe AR amplification or mutations. The degree of AR signaling suppression varied among treated tumors and there was upregulation of both AR and AR-V7 expression as well as a subset of neuroendocrine and plasticity genes.Conclusions: These data support the feasibility of targeted and temporal genomic and transcriptome profiling of neoadjuvant-treated prostate cancer with limited formalin-fixed paraffin embedded tissue requirement. Characterization of the heterogeneity of treatment response and molecular outliers that arise posttreatment provides new insight into potential early markers of resistance. Clin Cancer Res; 23(22); 6802-11. ©2017 AACR.

Bypassing Drug Resistance Mechanisms of Prostate Cancer with Small Molecules that Target Androgen Receptor-Chromatin Interactions

Human androgen receptor (AR) is a hormone-activated transcription factor that is an important drug target in the treatment of prostate cancer. Current small-molecule AR antagonists, such as enzalutamide, compete with androgens that bind to the steroid-binding pocket of the AR ligand-binding domain (LBD). In castration-resistant prostate cancer (CRPC), drug resistance can manifest through AR-LBD mutations that convert AR antagonists into agonists, or by expression of AR variants lacking the LBD. Such treatment resistance underscores the importance of novel ways of targeting the AR. Previously, we reported the development of a series of small molecules that were rationally designed to selectively target the AR DNA-binding domain (DBD) and, hence, to directly interfere with AR-DNA interactions. In the current work, we have confirmed that the lead AR DBD inhibitor indeed directly interacts with the AR-DBD and tested that substance across multiple clinically relevant CRPC cell lines. We have also performed a series of experiments that revealed that genome-wide chromatin binding of AR was dramatically impacted by the lead compound (although with lesser effect on AR variants). Collectively, these observations confirm the novel mechanism of antiandrogen action of the developed AR-DBD inhibitors, establishing proof of principle for targeting DBDs of nuclear receptors in endocrine cancers. Mol Cancer Ther; 16(10); 2281-91. ©2017 AACR.

Synergy between Androgen Receptor Antagonism and Inhibition of mTOR and HER2 in Breast Cancer

The androgen receptor (AR) is widely expressed in breast cancer, and evidence suggests dependence on AR signaling for growth and survival. AR antagonists such as enzalutamide and seviteronel have shown success in preclinical models and clinical trials of prostate cancer and are currently being evaluated in breast cancer. Reciprocal regulation between AR and the HER2/PI3K/mTOR pathway may contribute to resistance to HER2- and mTOR-targeted therapies; thus, dual inhibition of these pathways may synergistically inhibit breast cancer growth. HER2+ and triple-negative breast cancer cell lines were treated with AR antagonist plus anti-HER2 mAb trastuzumab or mTOR inhibitor everolimus. Apoptosis, cell proliferation, and drug synergy were measured in vitro Pathway component genes and proteins were measured by qRT-PCR, Western blot, and reverse phase protein array. In vivo, HER2+ breast cancer xenografts were treated with enzalutamide, everolimus, trastuzumab, and combinations of these drugs. AR antagonists inhibited proliferation of both HER2+ and TNBC cell lines. Combining AR antagonist and either everolimus or trastuzumab resulted in synergistic inhibition of proliferation. Dihydrotestosterone caused increased phosphorylation of HER2 and/or HER3 that was attenuated by AR inhibition. Everolimus caused an increase in total AR, phosphorylation of HER2 and/or HER3, and these effects were abrogated by enzalutamide. Growth of trastuzumab-resistant HER2+ xenograft tumors was inhibited by enzalutamide, and combining enzalutamide with everolimus decreased tumor viability more than either single agent. AR antagonists synergize with FDA-approved breast cancer therapies such as everolimus and trastuzumab through distinct mechanisms. Treatment combinations are effective in trastuzumab-resistant HER2+ breast cancer cells in vivoMol Cancer Ther; 16(7); 1389-400. ©2017 AACR.

IAP Antagonists Enhance Apoptotic Response to Enzalutamide in Castration-Resistant Prostate Cancer Cells via Autocrine TNF-α Signaling

BACKGROUND

Castration-resistant prostate cancer (CRPC) remains incurable and identifying effective treatments continues to present a clinical challenge. Although treatment with enzalutamide, a second generation androgen receptor (AR) antagonist, prolongs survival in prostate cancer patients, responses can be limited by intrinsic resistance or acquired resistance. A potential mechanism of resistance to androgen axis inhibition is evasion of apoptosis. Inhibitor of apoptosis proteins (IAPs) are found to be overexpressed in prostate cancer and function to block apoptosis and promote survival signaling. Novel, small-molecule IAP antagonists, such as AEG40995, are emerging as a strategy to induce apoptosis and increase therapeutic response in cancer.

METHODS

Human prostate cancer cell lines LNCaP and C4-2 were treated with enzalutamide with or without addition of IAP antagonist AEG40995 and proliferation and survival were determined by MTS and clonogenic assay. Western blot was used to evaluate IAP protein expression changes and PARP-1 cleavage was assessed as indication of apoptosis. Flow cytometry was performed to analyze apoptosis in treated cells. Caspase activity was determined by luminescence assay. Quantitative real-time PCR and immunometric ELISA was used to assess TNF-α (transcript and protein levels, respectively) in response to treatment.

RESULTS

In this study, we demonstrate that IAP antagonist AEG40995 exhibits minimal effects on prostate cancer cell proliferation or survival, but rapidly degrades cIAP1 protein. Combination treatment with enzalutamide demonstrates that AEG40995 increases apoptosis and reduces proliferation and clonogenic survival in cell line models of prostate cancer. Mechanistically, we demonstrate that apoptosis in response to enzalutamide and IAP antagonist requires activation of caspase-8, suggesting extrinsic/death receptor apoptosis signaling. Assessment of TNF-α in response to combination treatment with enzalutamide and AEG40995 reveals increased mRNA expression and autocrine protein secretion. Blocking TNF-α signaling abrogates the apoptotic response demonstrating that TNF-α plays a critical role in executing cell death in response to this drug combination.

CONCLUSIONS

These findings suggest that IAP antagonists can increase sensitivity and amplify the caspase-mediated apoptotic response to enzalutamide through TNF-α signaling mechanisms. Combination with an IAP antagonist increases enzalutamide sensitivity, lowers the apoptotic threshold and may combat drug resistance in patients with prostate cancer. Prostate 77:866-877, 2017. © 2017 Wiley Periodicals, Inc.

Effects of Long-Term Flutamide Treatment During Development on Sexual Behaviour and Hormone Responsiveness in Rams

Testosterone exposure during midgestation differentiates neural circuits controlling sex-specific behaviours and patterns of gonadotrophin secretion in male sheep. Testosterone acts through androgen receptors (AR) and/or after aromatisation to oestradiol and binding to oestrogen receptors. The present study assessed the role of AR activation in male sexual differentiation. We compared rams that were exposed to the AR antagonist flutamide (Flu) throughout the critical period (i.e. days 30-90 of gestation) to control rams and ewes that received no prenatal treatments. The external genitalia of all Flu rams were phenotypically female. Testes were positioned s.c. in the inguinal region of the abdomen, exhibited seasonally impaired androgen secretion and were azospermic. Flu rams displayed male-typical precopulatory and mounting behaviours but could not intromit or ejaculate because they lacked a penis. Flu rams exhibited greater mounting behaviour than control rams and, similar to controls, showed sexual partner preferences for oestrous ewes. Neither control, nor Flu rams responded to oestradiol treatments with displays of female-typical receptive behaviour or LH surge responses, whereas all control ewes responded as expected. The ovine sexually dimorphic nucleus in Flu rams was intermediate in volume between control rams and ewes and significantly different from both. These results indicate that prenatal anti-androgen exposure is not able to block male sexual differentiation in sheep and suggest that compensatory mechanisms intervene to maintain sufficient androgen stimulation during development.

Role of the androgen receptor in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive disease with outcomes inferior to those of other breast cancer subtypes. No targeted therapies are currently approved for TNBC, and newer treatment approaches are critically needed. It is increasingly recognized that TNBC is a heterogeneous disease, and the role of androgen signaling in a subset of TNBC is emerging. Although the degree of androgen receptor (AR) expression in TNBC varies widely depending on the assay methodology, cutoff for positivity, and patient population, existing evidence suggests an association between a higher level of AR expression and improved outcomes. Despite lower pathologic complete response (pCR) rates with neoadjuvant therapy, patients with AR-dependent TNBCs have a better prognosis than those with TNBCs that are not AR-dependent. Furthermore, gene expression profiling has been used to identify a luminal androgen receptor subtype of TNBC that is dependent on AR signaling. Early clinical studies investigating agents targeting AR in advanced TNBC have produced promising results. We review herein the literature on the biology of AR in breast cancer and its prognostic and predictive role in TNBC, and we describe the results of early clinical trials with antiandrogens in this population. We also present our vision of the future development of newer therapeutic strategies in AR-dependent TNBC.

Beyond aggression: Androgen-receptor blockade modulates social interaction in wild meerkats

In male vertebrates, androgens are inextricably linked to reproduction, social dominance, and aggression, often at the cost of paternal investment or prosociality. Testosterone is invoked to explain rank-related reproductive differences, but its role within a status class, particularly among subordinates, is underappreciated. Recent evidence, especially for monogamous and cooperatively breeding species, suggests broader androgenic mediation of adult social interaction. We explored the actions of androgens in subordinate, male members of a cooperatively breeding species, the meerkat (Suricata suricatta). Although male meerkats show no rank-related testosterone differences, subordinate helpers rarely reproduce. We blocked androgen receptors, in the field, by treating subordinate males with the antiandrogen, flutamide. We monitored androgen concentrations (via baseline serum and time-sequential fecal sampling) and recorded behavior within their groups (via focal observation). Relative to controls, flutamide-treated animals initiated less and received more high-intensity aggression (biting, threatening, feeding competition), engaged in more prosocial behavior (social sniffing, grooming, huddling), and less frequently initiated play or assumed a 'dominant' role during play, revealing significant androgenic effects across a broad range of social behavior. By contrast, guarding or vigilance and measures of olfactory and vocal communication in subordinate males appeared unaffected by flutamide treatment. Thus, androgens in male meerkat helpers are aligned with the traditional trade-off between promoting reproductive and aggressive behavior at a cost to affiliation. Our findings, based on rare endocrine manipulation in wild mammals, show a more pervasive role for androgens in adult social behavior than is often recognized, with possible relevance for understanding tradeoffs in cooperative systems.

Androgen receptors and experimental bone loss - an in vivo and in vitro study

Testosterone is a sex hormone that exhibits many functions beyond reproduction; one such function is the regulation of bone metabolism. The role played by androgen receptors during testosterone-mediated biological processes associated with bone metabolism is largely unknown. This study aims to use a periodontal disease model in vivo in order to assess the involvement of androgen receptors on microbial-induced inflammation and alveolar bone resorption in experimental bone loss. The impact of hormone deprivation was tested through both orchiectomy and chemical blockage of androgen receptor using flutamide (FLU). Additionally, the direct effect of exogenous testosterone, and the role of the androgen receptor, on osteoclastogenesis were investigated. Thirty male adult rats (n=10/group) were subjected to: 1-orchiectomy (OCX); 2-OCX sham surgery; or 3-OCX sham surgery plus FLU, four weeks before the induction of experimental bone loss. Ten OCX sham-operated rats were not subjected to experimental bone loss and served as healthy controls. The rats were euthanized two weeks later, so as to assess bone resorption and the production of inflammatory cytokines in the gingival tissue and serum. In order to study the in vitro impact of testosterone, osteoclasts were differentiated from RAW264.7 cells and testosterone was added at increasing concentrations. Both OCX and FLU increased bone resorption, but OCX alone was observed to increase osteoclast count. IL-1β production was increased only in the gingival tissue of OCX animals, whereas FLU-treated animals presented a decreased expression of IL-6. Testosterone reduced the osteoclast formation in a dose-dependent manner, and significantly impacted the production of TNF-α; FLU partially reversed these actions. When taken together, our results indicate that testosterone modulates experimental bone loss, and that this action is mediated, at least in part, via the androgen receptor.

Precision medicine for prostate cancer

Metastatic castration-resistant prostate cancer remains a lethal disease despite considerable progress in systemic therapy over the past decade. The recent advances in genomic sequencing have improved the molecular classification of prostate cancer. The translation of genomic data into clinically relevant prognostic and predictive biomarkers to guide therapy is still in its infancy and therapies for castration-resistant prostate cancer are still used empirically. We discuss these genomic aberrations in more detail, focusing on androgen receptor signaling, ETS transcription factor gene rearrangements and PTEN loss. The incorporation of this genomic data within early phase clinical trials is evolving and may prove significant in advancing personalized care in prostate cancer.

Mechanisms of acquired resistance to androgen receptor targeting drugs in castration-resistant prostate cancer

After initial response to androgen receptor (AR) targeting drugs abiraterone or enzalutamide, most patients develop progressive disease and therefore, castration resistant prostate cancer remains a terminal disease. Multiple mechanisms underlying acquired resistance have been postulated. Intratumoral androgen synthesis may resume after abiraterone treatment. A point mutation in the ligand-binding domain of AR may confer resistance to enzalutamide. Emergence of AR splice variants lacking the ligand-binding domain may mediate resistance to abiraterone and enzalutamide. Steroid receptors such as glucocorticoid receptor may substitute for AR. Drugs with novel mechanisms of action or combination therapy, along with biomarkers for patient selection, may be needed to improve the therapy of castration resistant prostate cancer.

Peripheral androgen receptors sustain the acrobatics and fine motor skill of elaborate male courtship

Androgenic hormones regulate many aspects of animal social behavior, including the elaborate display routines on which many species rely for advertisement and competition. One way that this might occur is through peripheral effects of androgens, particularly on skeletal muscles that control complex movements and postures of the body and its limbs. However, the specific contribution of peripheral androgen-muscle interactions to the performance of elaborate behavioral displays in the natural world has never been examined. We study this issue in one of the only natural physiological models of animal acrobatics: the golden-collared manakin (Manacus vitellinus). In this tropical bird, males compete with each other and court females by producing firecracker-like wing- snaps and by rapidly dancing among saplings over the forest floor. To test how activation of peripheral androgen receptors (AR) influences this display, we treat reproductively active adult male birds with the peripherally selective antiandrogen bicalutamide (BICAL) and observe the effects of this manipulation on male display performance. We not only validate the peripheral specificity of BICAL in this species, but we also show that BICAL treatment reduces the frequency with which adult male birds perform their acrobatic display maneuvers and disrupts the overall structure and fine-scale patterning of these birds' main complex wing-snap sonation. In addition, this manipulation has no effect on the behavioral metrics associated with male motivation to display. Together, our findings help differentiate the various effects of peripheral and central AR on the performance of a complex sociosexual behavioral phenotype by indicating that peripheral AR can optimize the motor skills necessary for the production of an elaborate animal display.

Androgen receptor antagonist impairs courtship but not aggressive behavior in the monogamous cichlid, Amatitlania nigrofasciata

Androgens, specifically 11-ketotestosterone, are hypothesized to be important in the expression of pre-spawning behaviors such as courtship and aggression in many teleost species. This experiment attempted to elucidate the roles of androgens in the expression of pre-spawning courtship and aggression in male convict cichlids (Amatitlania nigrofasciata). In a laboratory experiment, males were treated with either the androgen receptor antagonist flutamide or blank control and subsequently exposed to social conditions to stimulate inter-sexual courtship or intra-sexual aggression. Males treated with flutamide expressed significantly fewer courtship behaviors than control males but did not differ from control males in pre-spawning intra-sexual aggression. In a field experiment, males treated with flutamide expressed significantly less courtship behavior than males given blank capsules or unmanipulated control males, but did not differ from either set of control males in aggression towards conspecifics or overall aggression to con- and heterospecifics. These data suggest that androgens mediate pre-spawning courtship behavior but not pre-spawning aggression in this species.

Role of androgen receptor in progression of LNCaP prostate cancer cells from G1 to S phase

Background

The androgen receptor (AR) plays a critical role in the proliferation of prostate cancer cells. However, its mechanism of action in proliferation remains unknown. An understanding of the mechanism of AR action in proliferation may lead to the development of effective strategies for the treatment of prostate cancer.

Methodology/Principal Findings

In this study we report that pulse treatment of synchronized LNCaP cells with Casodex, an AR-antagonist, for 4 hours in mid-G₁ phase was sufficient to prevent cells from entering S phase. Since the assembly of pre-replication complex (pre-RC) in G₁ is required for the progression of cells from G₁ to S phase, the effect of Casodex during mid-G₁ suggested that the role of AR in proliferation might be to regulate the assembly of pre-RC. To test this possibility, we investigated the interaction between AR and Cdc6, an essential component of pre-RC in LNCaP cells. AR co-localized and co-immunoprecipitated with Cdc6, and Casodex treatment disrupted this interaction. AR-immunoprecipitate (AR-IP) also contained cyclin E and cyclin A, which play a critical role in pre-RC assembly and cell cycle entry into S phase, and DNA polymerase-α, PCNA, and ribonucleotide reductase, which are essential for the initiation of DNA synthesis. In addition, in cells in S phase, AR co-sedimented with components of the DNA replication machinery of cells that entered S phase.

Conclusions/Significance

Together, these observations suggest a novel role of AR as a component of the pre-RC to exert control over progression of LNCaP cells from G₁ to S phase through a mechanism that is independent of its role as a transcription factor.

Synergistic activity of the mTOR inhibitor ridaforolimus and the antiandrogen bicalutamide in prostate cancer models

Although androgen ablation therapy is the foundation of current prostate cancer treatment, most patients ultimately develop castration-resistant disease. One proposed mechanism to account for androgen receptor (AR) activity in the castrate environment is via crosstalk with other signaling pathways. Specifically, reciprocal interactions between the AKT/mTOR and AR pathways have been implicated in prostate cancer progression. Here, we used the potent inhibitor ridaforolimus to target mTOR signaling alone and in combination with AR blockade by bicalutamide to examine the effect of abrogating these signaling pathways. Ridaforolimus treatment inhibited the proliferation of all six prostate cancer cell lines examined with the greatest sensitivity associated with loss of PTEN and elevated AKT/mTOR pathway activity. Dual inhibition of the AR and mTOR signaling pathways provided further benefit with the ridaforolimus-bicalutamide combination producing synergistic antiproliferative effects in prostate cancer cells in vitro when compared with each agent alone. Pharmacodynamic analysis confirmed that combination treatment resulted in full inhibition of each of the respective pathways. Importantly, the ridaforolimus-bicalutamide combination exhibited potent antitumor activity with parallel reductions in plasma PSA levels in vivo. Taken together, ridaforolimus exhibited potent antiproliferative and antitumor activity in prostate cancer models and the addition of bicalutamide represents a potentially effective combination strategy for patient therapy.

Biological properties of androgen receptor pure antagonist for treatment of castration-resistant prostate cancer: optimization from lead compound to CH5137291

BACKGROUND

Castration-resistant prostate cancer (CRPC) is still dependent on androgen receptor (AR) signaling. We previously reported that a novel nonsteroidal AR pure antagonist, CH4933468, which is a thiohydantoin derivative with a sulfonamide side chain, provided in vitro proof of concept but did not in vivo.

METHODS

We developed other derivatives, CH5137291, CH5138514, and CH5166623, and their pharmacological properties were compared with CH4933468 and bicalutamide. Agonist/antagonist activities in AR-mediated transactivation, cell proliferation against LNCaP and LNCaP-BC2, and AR translocation were evaluated. Agonist metabolite was monitored in liver microsomes and in pharmacokinetics experiments. Antitumor activities in CRPC xenograft models were examined using LNCaP-BC2 and VCaP-CRPC.

RESULTS

All CH compounds completely inhibited AR-mediated transactivation and proliferation of LNCaP and LNCaP-BC2. In contrast bicalutamide showed a partial inhibition of AR-mediated transactivation and a proliferation of LNCaP-BC2. AR translocation to nucleus was inhibited by CH compounds, but stimulated by bicalutamide. In the LNCaP-BC2 xenograft model, however, only CH5137291 showed significant inhibition of plasma PSA level and antitumor activity. The other three CH compounds were metabolized to their core structure which had agonist activity. CH5137291 also exhibited antitumor activity in a VCaP-CRPC xenograft model, but bicalutamide did not.

CONCLUSIONS

The molecular mechanism of the CH compounds, inhibition of AR translocation, was different from bicalutamide and this action could contribute to AR pure antagonist activity. Agonist metabolite diminished the antitumor activity of AR pure antagonist. CH5137291 exhibited antitumor activity in LNCaP-BC2 and VCaP-CRPC xenograft models, suggesting that the compound has potential for the treatment of CRPC.

Inhibition of androgen receptor functions by gelsolin FxxFF peptide delivered by transfection, cell-penetrating peptides, and lentiviral infection

BACKGROUND

Prostate cancer (PC) growth is dependent on the androgen-androgen receptor (AR) axis. Because current androgen ablation therapies of PC lead to resistance, novel approaches to block AR activity are urgently needed.

METHODS

We inhibited AR function beyond the level of hormone binding by blockade of the coactivator groove in the ligand-binding domain (LBD) using a high-affinity gelsolin FxxFF peptide. Following peptide selection, the effect of the gelsolin FxxFF peptide on AR functions was determined in Hep3B cells that were transiently transfected with pM-peptide expression vectors or were incubated with synthetic gelsolin FxxFF peptide coupled to the TAT cell-penetrating peptide. Lentiviruses expressing the gelsolin FxxFF peptide were used to study endogenous AR target gene expression in LNCaP cells.

RESULTS

pM-Gelsolin FxxFF efficiently interfered with AR N/C interaction and specifically inhibited AR-regulated reporter gene activity. The peptide did not inhibit progesterone receptor (PR) and glucocorticoid receptor (GR) activity, nor constitutively active gene promoters. The peptide also specifically blocked in vitro interactions of AR LBD with peptides. Like the gelsolin FxxFF peptide expressed by an expression vector, synthetic TAT-gelsolin FxxFF peptide efficiently blocked AR N/C interaction and inhibited full-length AR-regulated reporter gene activity. It hardly affected PR and GR activity, but the effect on constitutively active promoters was variable. Lentiviral gelsolin FxxFF peptide inhibited expression of KLK2 and NDRG1, but hardly affected PSA and TMPRSS2.

CONCLUSIONS

Our results show that the AR coactivator groove may function as a target to overcome therapeutic failure that arises during current androgen ablation therapies.

Anti-androgenic activities of environmental pesticides in the MDA-kb2 reporter cell line

Pesticides have been suspected to act as endocrine disruptive compounds (EDCs) through several mechanisms of action, however data are still needed for a number of currently used pesticides. In the present study, 30 environmental pesticides selected from different chemical classes (azole, carbamate, dicarboximide, organochlorine, organophosphorus, oxadiazole, phenylureas, pyrazole, pyrimidine, pyrethroid and sulfonylureas) were tested for their ability to alter in vitro the transcriptional activity of the androgen receptor in the MDA-kb2 reporter cell line. The responsiveness of the system was checked by using a panel of reference ligands of androgen and glucocorticoid receptors. When tested alone at concentrations up to 10 μM, none of the studied pesticides were able to induce the reporter gene after a 18 h exposure. Conversely, co-exposure experiments with 0.1 nM dihydrotestosterone (DHT) allowed identifying 15 active pesticides with IC(50) ranging from 0.2 μM for vinclozolin to 12 μM for fenarimol. Fipronil and bupirimate were here newly described for their AR antagonistic activity.