MDV3100 for the treatment of prostate cancer

Discovery and pharmacological characterization of 1,2,3,4-tetrahydroquinoline derivatives as RORγ inverse agonists against prostate cancer

The retinoic acid receptor-related orphan receptor γ (RORγ) is regarded as an attractive therapeutic target for the treatment of prostate cancer. Herein, we report the identification, optimization, and evaluation of 1,2,3,4-tetrahydroquinoline derivatives as novel RORγ inverse agonists, starting from high throughput screening using a thermal stability shift assay (TSA). The representative compounds 13e (designated as XY039) and 14a (designated as XY077) effectively inhibited the RORγ transcriptional activity and exhibited excellent selectivity against other nuclear receptor subtypes. The structural basis for their inhibitory potency was elucidated through the crystallographic study of RORγ LBD complex with 13e. Both 13e and 14a demonstrated reasonable antiproliferative activity, potently inhibited colony formation and the expression of AR, AR regulated genes, and other oncogene in AR positive prostate cancer cell lines. Moreover, 13e and 14a effectively suppressed tumor growth in a 22Rv1 xenograft tumor model in mice. This work provides new and valuable lead compounds for further development of drugs against prostate cancer.

Design, synthesis, and biological evaluation of 2-(naphthalen-1-yloxy)-N-phenylacetamide derivatives as TRPM4 inhibitors for the treatment of prostate cancer

Transient receptor potential melastatin 4 (TRPM4) is considered to be a potential target for cancer and other human diseases. Herein, a series of 2-(naphthalen-1-yloxy)-N-phenylacetamide derivatives were designed and synthesized as new TRPM4 inhibitors, aiming to improve cellular potency. One of the most promising compounds, 7d (ZX08903), displayed promising antiproliferative activity against prostate cancer cell lines. 7d also suppressed colony formation and the expression of androgen receptor (AR) protein in prostate cancer cells. Furthermore, 7d can concentration-dependently induce cell apoptosis in prostate cancer cells. Collectively, these findings indicated that compound 7d may serve as a promising lead compound for further anticancer drug development.

Design, Synthesis, and Biological Evaluation of 1-(Indolizin-3-yl)ethan-1-ones as CBP Bromodomain Inhibitors for the Treatment of Prostate Cancer

CREB (cyclic-AMP responsive element binding protein) binding protein (CBP) is a potential target for prostate cancer treatment. Herein, we report the structural optimization of a series of 1-(indolizin-3-yl)ethan-1-one compounds as new selective CBP bromodomain inhibitors, aiming to improve cellular potency and metabolic stability. This process led to compound 9g (Y08284), which possesses good liver microsomal stability and pharmacokinetic properties (F = 25.9%). Furthermore, the compound is able to inhibit CBP bromodomain as well as the proliferation, colony formation, and migration of prostate cancer cells. Additionally, the new inhibitor shows promising antitumor efficacy in a 22Rv1 xenograft model (TGI = 88%). This study provides new lead compounds for further development of drugs for the treatment of prostate cancer.

Discovery and Characterization of Benzimidazole Derivative XY123 as a Potent, Selective, and Orally Available RORγ Inverse Agonist

Receptor-related orphan receptor γ (RORγ) has emerged as an attractive therapeutic target for the treatment of cancer and inflammatory diseases. Herein, we report our effort on the discovery, optimization, and evaluation of benzothiazole and benzimidazole derivatives as novel inverse agonists of RORγ. The representative compound 27h (designated as XY123) potently inhibited the RORγ transcription activity with a half-maximal inhibitory concentration (IC50) value of 64 nM and showed excellent selectivity against other nuclear receptors. 27h also potently suppressed cell proliferation, colony formation, and the expression of androgen receptor (AR)-regulated genes in AR-positive prostate cancer cell lines. In addition, 27h demonstrated good metabolic stability and a pharmacokinetic property with reasonable oral bioavailability (32.41%) and moderate half-life (t1/2 = 4.98 h). Significantly, oral administration of compound 27h achieved complete and long-lasting tumor regression in the 22Rv1 xenograft tumor model in mice. Compound 27h may serve as a new valuable lead compound for further development of drugs for the treatment of prostate cancer.

CDK7 Inhibition Suppresses Castration-Resistant Prostate Cancer through MED1 Inactivation

Metastatic castration-resistant prostate cancer (CRPC) is a fatal disease, primarily resulting from the transcriptional addiction driven by androgen receptor (AR). First-line CRPC treatments typically target AR signaling, but are rapidly bypassed, resulting in only a modest survival benefit with antiandrogens. Therapeutic approaches that more effectively block the AR-transcriptional axis are urgently needed. Here, we investigated the molecular mechanism underlying the association between the transcriptional coactivator MED1 and AR as a vulnerability in AR-driven CRPC. MED1 undergoes CDK7-dependent phosphorylation at T1457 and physically engages AR at superenhancer sites, and is essential for AR-mediated transcription. In addition, a CDK7-specific inhibitor, THZ1, blunts AR-dependent neoplastic growth by blocking AR/MED1 corecruitment genome-wide, as well as reverses the hyperphosphorylated MED1-associated enzalutamide-resistant phenotype. In vivo, THZ1 induces tumor regression of AR-amplified human CRPC in a xenograft mouse model. Together, we demonstrate that CDK7 inhibition selectively targets MED1-mediated, AR-dependent oncogenic transcriptional amplification, thus representing a potential new approach for the treatment of CRPC. SIGNIFICANCE: Potent inhibition of AR signaling is critical to treat CRPC. This study uncovers a driver role for CDK7 in regulating AR-mediated transcription through phosphorylation of MED1, thus revealing a therapeutically targetable potential vulnerability in AR-addicted CRPC.See related commentary by Russo et al., p. 1490.This article is highlighted in the In This Issue feature, p. 1469.

Analysis of the androgen receptor-regulated lncRNA landscape identifies a role for ARLNC1 in prostate cancer progression

The androgen receptor (AR) plays a critical role in the development of the normal prostate as well as prostate cancer. Using an integrative transcriptomic analysis of prostate cancer cell lines and tissues, we identified ARLNC1 (AR-regulated long non-coding RNA 1) as an important long non-coding RNA that is strongly associated with AR signaling in prostate cancer progression. Not only was ARLNC1 induced by AR protein, ARLNC1 stabilized the AR transcript via RNA-RNA interaction. ARLNC1 knockdown suppressed AR expression, global AR signaling, and prostate cancer growth in vitro and in vivo. Taken together, these data support a role for ARLNC1 in maintaining a positive feedback loop that potentiates AR signaling during prostate cancer progression, and identifies ARLNC1 as a novel therapeutic target.

Y08060: A Selective BET Inhibitor for Treatment of Prostate Cancer

Prostate cancer is a commonly diagnosed cancer and a leading cause of cancer-related deaths. The bromodomain and extra terminal domain (BET) family proteins have emerged as potential therapeutic targets for the treatment of castration-resistant prostate cancer. A series of 2,2-dimethyl-2H-benzo[b][1,4]oxazin-3(4H)-one derivatives were designed and synthesized as selective bromodomain containing protein 4 (BRD4) inhibitors. The compounds potently inhibit BRD4(1) with nanomolar IC50 values and exhibit high selectivity over most non-BET subfamily members. One of the representative compounds 36 (Y08060) effectively suppresses cell growth, colony formation, and expression of androgen receptor (AR), AR regulated genes, and MYC in prostate cancer cell lines. In in vivo studies, 36 demonstrates a good PK profile with high oral bioavailability (61.54%) and is a promising lead compound for further prostate cancer drug development.

Molecular characterization of a novel androgen receptor transgene responsive to MicroRNA mediated post-transcriptional control exerted via 3'-untranslated region

BACKGROUND

Androgen Receptor (AR) gene is associated with Prostate cancer (PCa) and hence targeting androgen-and AR-signaling axis remains the most promising primary therapeutic option to treat the disease. The AR mRNA has a 6.8 kb long 3'-untranslated region (UTR) which harbors several experimentally validated and numerous predicted miRNA binding sites. AR 3'-UTR is likely to positively or negatively regulate AR expression by interacting with miRNAs and possibly other trans-acting auxiliary factors including 3'-UTR RNA binding proteins. In this context, systematic understanding of the regulatory role of AR 3'-UTR in intrinsic post-transcriptional control of AR gene expression is of significance to understand AR related diseases including PCa.

METHODS

In this study, we have constructed a heterologous reporter system in which Firefly luciferase and AR expression is experimentally influenced by the presence of AR 3'-UTR and its interactions with ectopically expressing miRNA.

RESULTS

The expression of AR 3'-UTR containing reporters, including the Firefly luciferase and the AR open reading frame (ORF) were repressed by the overexpression of miR-488* mimics. In addition, the AR expressed from 3'-UTR containing expression vectors was fully functional in its transactivation function as determined by a prostate specific antigen (PSA) reporter assay. Further, by using confocal microscopy we also demonstrate that AR can translocate to the nucleus upon DHT activation confirming the functional ability of AR.

CONCLUSIONS

AR transgenes with AR 3'-UTR fragments closely resemble the endogenous AR expression than any other previously characterized AR expression constructs. The 3'-UTR containing AR expression system is amiable to post-transcriptional manipulations including miRNA mediated repression of AR expression. This AR reporter system has the potential to be used in determining specificity of AR targeting miRNAs and their role in AR functional regulatory networks. Prostate 76:834-844, 2016. © 2016 Wiley Periodicals, Inc.

Targeting PI3K/Akt/mTOR signaling pathway in the treatment of prostate cancer radioresistance

The phosphatidylinositol-3-kinase/Akt and the mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is one of the most frequently activated signaling pathways in prostate cancer (CaP) and other cancers, and responsible for the survival, metastasis and therapeutic resistance. Recent advances in radiation therapy indicate that activation of this pathway is closely associated with cancer radioresistance, which is a major challenge for the current CaP radiation treatment. Therefore, targeting this pathway by inhibitors to enhance radiosensitivity has great potential for clinical benefits of CaP patients. In this review, we summarize the recent findings in the PI3K/Akt/mTOR pathway in CaP radiotherapy research and discuss the potential use of the PI3K/Akt/mTOR pathway inhibitors as radiosensitizers in the treatment of CaP radioresistance in preclinical studies to explore novel approaches for future clinical trials.

Beyond PSA: managing modern therapeutic options in metastatic castration-resistant prostate cancer

Prostate cancer remains a significant cause of cancer-related deaths in men in the United States. Significant advances in the treatment of metastatic castration-resistant prostate cancer have been made in recent years with the arrival of new therapeutic targets and options. The definition of progression of disease must be thought of in the context of clinical symptoms and radiographic evidence rather than as changes in prostate-specific antigen (PSA). Ultimately, the use of PSA criteria alone should not be used to determine the progression of disease; instead, PSA should be evaluated in combination with other clinical data.

Therapeutic targeting of BET bromodomain proteins in castration-resistant prostate cancer

Men who develop metastatic castration-resistant prostate cancer (CRPC) invariably succumb to the disease. The development and progression to CRPC following androgen ablation therapy is predominantly driven by unregulated androgen receptor (AR) signaling^1-3. Despite the success of recently approved therapies targeting AR signaling such as abiraterone^4-6 and second generation anti-androgens MDV3100 (enzalutamide)^7,8, durable responses are limited, presumably due to acquired resistance. Recently JQ1 and I-BET, two selective small molecule inhibitors that target the amino-terminal bromodomains of BRD4, have been shown to exhibit anti-proliferative effects in a range of malignancies^9-12. Here we show that AR signaling-competent CRPC cell lines are preferentially sensitive to BET bromodomain inhibition. BRD4 physically interacts with the N-terminal domain of AR and can be disrupted by JQ1^11,13. Like the direct AR antagonist, MDV3100, JQ1 disrupted AR recruitment to target gene loci. In contrast to MDV3100, JQ1 functions downstream of AR, and more potently abrogated BRD4 localization to AR target loci and AR-mediated gene transcription including induction of TMPRSS2-ERG and its oncogenic activity. In vivo, BET bromodomain inhibition was more efficacious than direct AR antagonism in CRPC xenograft models. Taken together, these studies provide a novel epigenetic approach for the concerted blockade of oncogenic drivers in advanced prostate cancer.

Detection and characterization of invasive circulating tumor cells derived from men with metastatic castration-resistant prostate cancer

The Vitatex cell-adhesion matrix (CAM) platform allows for isolation of invasive circulating tumor cells (iCTCs). Here we sought to determine the utility of prostate-specific membrane antigen (PSMA) as a metastatic castration-resistant prostate cancer (mCRPC) iCTC biomarker, to identify solitary cells and clusters of iCTCs expressing either epithelial, mesenchymal, or stem cell markers, and to explore the feasibility of iCTC epigenomic analysis. CTCs were isolated and enumerated simultaneously using the Vitatex and CellSearch platforms in 23 men with mCRPC. CAM-avid iCTCs were identified as nucleated cells capable of CAM uptake, but without detectable expression of hematopoietic lineage (HL) markers including CD45. iCTCs were enumerated immunocytochemically (ICC) and by flow cytometry. Whole-genome methylation status was determined for iCTCs using the Illumina HumanMethylation27 BeadChip. Thirty-four samples were collected for iCTC analysis. A median of 27 (range 0-800) and 23 (range 2-390) iCTCs/mL were detected by ICC and flow, respectively. In a subset of 20 samples, a median of seven CTCs/mL (range 0-85) were detected by the CellSearch platform compared to 26 by the CAM platform. iCTC clusters were observed in 17% of samples. iCTCs expressing PSMA as well as markers of EMT and stemness were detectable. The iCTC methylation profile highly resembled mCRPC. More CTCs were recovered using the CAM platform than the CellSearch platform, and the CAM platform allowed for the detection of iCTC clusters, iCTCs expressing EMT and stem-cell markers, and characterization of the iCTC methylome. Correlation with clinical data in future studies may yield further insight into the functional significance of these findings.

Novel therapeutic approaches for the treatment of castration-resistant prostate cancer

Prostate cancer is a leading cause of cancer death in men in developed countries. Once the tumor has achieved a castration-refractory metastatic stage, treatment options are limited with the average survival of patients ranging from two to three years only. Recently, new drugs for treatment of castration-resistant prostate cancer (CRPC) have been approved, and others are in an advanced stage of clinical testing. In this review we provide an overview of the new therapeutic agents that arrived in the clinical praxis or are tested in clinical studies and their mode of action including hormone synthesis inhibitors, new androgen receptor blockers, bone targeting and antiangiogenic agents, endothelin receptor antagonists, growth factor inhibitors, novel radiotherapeutics and taxanes, and immunotherapeutic approaches. Results and limitations from clinical studies as well as future needs for improvement of CRPC treatments are critically discussed.

Prostate cancer vaccines

In 2010, the US FDA approved the first therapeutic cancer vaccine for the treatment of castration refractory prostate cancer - sipuleucel-T. Prostate cancer is an ideal model for cancer vaccine development based on the ready demonstration of humoral and cellular immunity to a range of cancer antigens as well as often slow progression which means that patients who are otherwise well may have a radiologically evaluable minor progression, after conventional treatment and can undergo vaccine therapy over sufficient periods of time, so as to allow the generation of a robust antitumor response. The association of prostate cancer with one of the few serum cancer biomarkers in general use has also allowed assessment of response and risk stratification of patients. In this review, we will examine key aspects of the evolution of prostate cancer vaccines, which provides an accurate prototype for other cancers, and the challenges we face.

Role of the EpCAM (CD326) in prostate cancer metastasis and progression

Despite significant advances in surgery, radiotherapy and chemotherapy to treat prostate cancer (CaP), many patients die of secondary disease (metastases). Current therapeutic approaches are limited, and there is no cure for metastatic castration-resistant prostate cancer (CRPC). Epithelial cell adhesion molecule (EpCAM, also known as CD326) is a transmembrane glycoprotein that is highly expressed in rapidly proliferating carcinomas and plays an important role in the prevention of cell-cell adhesion, cell signalling, migration, proliferation and differentiation. Stably and highly expressed EpCAM has been found in primary CaP tissues, effusions and CaP metastases, making it an ideal candidate of tumour-associated antigen to detect metastasis of CaP cells in the circulation as well as a promising therapeutic target to control metastatic CRPC disease. In this review, we discuss the implications of the newly identified roles of EpCAM in terms of its diagnostic and metastatic relevance to CaP. We also summarize EpCAM expression in human CaP and EpCAM-mediated signalling pathways in cancer metastasis. Finally, emerging and innovative approaches to the management of the disease and expanding potential therapeutic applications of EpCAM for targeted strategies in future CaP therapy will be explored.

Systematic structure modifications of multitarget prostate cancer drug candidate galeterone to produce novel androgen receptor down-regulating agents as an approach to treatment of advanced prostate cancer

As part of our program to explore the influence of small structural modifications of our drug candidate 3β-(hydroxy)-17-(1H-benzimidazol-1-yl)androsta-5,16-diene (galeterone, 5) on the modulation of the androgen receptor (AR), we have prepared and evaluated a series of novel C-3, C-16, and C-17 analogues. Using structure activity analysis, we established that the benzimidazole moiety at C-17 is essential and optimal and also that hydrophilic and heteroaromatic groups at C-3 enhance both antiproliferative (AP) and AR degrading (ARD) activities. The most potent antiproliferative compounds were 3β-(1H-imidazole-1-carboxylate)-17-(1H-benzimidazol-1-yl)androsta-5,16-diene (47), 3-((EZ)-hydroximino)-17-(1H-benzimidazol-1-yl)androsta-4,16-diene (36), and 3β-(pyridine-4-carboxylate)-17-(1H-benzimidazol-1-yl)androsta-5,16-diene (43), with GI50 values of 0.87, 1.91, and 2.57 μM, respectively. Compared to 5, compound 47 was 4- and 8-fold more potent with respect to AP and ARD activities, respectively. Importantly, we also discovered that our compounds, including 5, 36, 43, and 47, could degrade both full-length and truncated ARs in CWR22rv1 human prostate cancer cells. With these activities, they have potential for development as new drugs for the treatment of all forms of prostate cancer.

Pain questionnaire performance in advanced prostate cancer: comparative results from two international clinical trials

PURPOSE

To compare pain assessment questionnaires commonly used in advanced prostate cancer trials and to determine the psychometric characteristics and longitudinal relationships by contrasting questionnaire data from two international phase 2 trials.

METHODS

Scores from the Present Pain Intensity (PPI) question of the McGill Pain Questionnaire, the pain intensity scale of the Brief Pain Inventory (BPI), and the Functional Assessment of Cancer Therapy-Prostate (FACT-P) were analyzed using Pearson correlation, intraclass correlation coefficient, and Cronbach's α, respectively. Concordance was evaluated with Cohen's kappa coefficient and McNemar test at baseline (n = 224) and two subsequent observations.

RESULTS

PPI and FACT-P scores were associated with the BPI score at baseline for Trials 1 and 2: PPI r = 0.66 and 0.80, respectively (P < 0.001); FACT-P (pain scale) r = -0.76 and -0.82, respectively (P < 0.001). However, concordance analysis revealed that the BPI identified pain (score > 0) at higher rates than the PPI: at baseline, BPI: 89 % (64/72) and 77 % (95/124), PPI: 68 % (49/72) and 64 % (79/124) [Trials 1 and 2, respectively; McNemar test (P < 0.001) for both studies]. The FACT-P pain scale identified pain similarly to the BPI pain intensity scale; longitudinal analysis produced comparable findings. All pain scales met standard psychometric acceptability criteria, but the BPI and FACT-P performed better than the PPI.

CONCLUSIONS

Data suggest the BPI pain intensity and FACT-P pain scales are better than the PPI question at capturing the pain experience among patients with advanced prostate cancer. Additional comparative research is needed in larger population samples.

Steroid derivatives as pure antagonists of the androgen receptor

BACKGROUND

While the androgens of testicular origin (representing about 50% of total androgens in men over 50 years) can be completely eliminated by surgical or medical castration with GnRH (gonadotropin-releasing hormone) agonists or antagonists, the antiandrogens currently available as blockers of androgen binding to the androgen receptor (AR), namely bicalutamide (BICA), flutamide (FLU) and nilutamide have too weak affinity to completely neutralize the other 50% of androgens made locally from dehydroepiandrosterone (DHEA) in the prostate cancer tissue by the mechanisms of intracrinology.

MATERIALS AND METHODS

Series of steroid derivatives having pure and potent antagonistic activity on the human and rodent AR were synthesized. Assays of AR binding and activity in carcinoma mouse Shionogi and human LNCaP cells as well as in vivo bioavailability measurements and in vivo prostate weight assays in the rat were used.

RESULTS

The chosen lead steroidal compound, namely EM-5854, has a 3.7-fold higher affinity than BICA for the human AR while EM-5855, an important metabolite of EM-5854, has a 94-fold higher affinity for the human AR compared to BICA. EM-5854 and EM-5855 are 14 times more potent than BICA in inhibiting androgen (R1881)-stimulated prostatic specific antigen (PSA) secretion in human prostatic carcinoma LNCaP cells in vitro. MDV3100 has a potency comparable to bicalutamide in these assays. Depending upon the oral formulation, EM-5854 is 5- to 10-times more potent than BICA to inhibit dihydrotestosterone (DHT)-stimulated ventral prostatic weight in vivo in the rat while MDV3100 has lower activity than BICA in this in vivo model. These data are supported by respective 40-fold and 105-fold higher potencies of EM-5854 and EM-5855 compared to BICA to inhibit cell proliferation in the androgen-sensitive Shionogi carcinoma cell model.

CONCLUSIONS

Although the present preclinical results data need evaluation in clinical trials in men, combination of the data obtained in vitro in human LNCaP cells as indicator of potency in the human prostate and the data on metabolism evaluated in vivo on ventral prostate weight in the rat, could suggest the possibility of a 70- to 140-fold higher potency of EM-5854 compared to bicalutamide (Casodex) for the treatment of prostate cancer in men.

The role of enzalutamide in the treatment of castration-resistant prostate cancer

Prostate cancer is the most common solid organ cancer affecting the male population. Men with metastatic prostate cancer treated with androgen ablation therapy often respond rapidly, with improvement in bone pain and decreases in serum prostate-specific antigen. However, almost all patients progress to the castration-resistant state and abiraterone acetate was the last treatment available with proven survival benefit. Enzalutamide (formerly MDV3100) is an androgen receptor signaling inhibitor that has been shown to improve survival in men with metastatic castration-resistant prostate cancer previously treated with chemotherapy. In this article we discuss the characteristics of enzalutamide and provide a review of its clinical development.

Steroid biosynthesis and prostate cancer

The pathways of androgen biosynthesis in human beings have been studied for decades, and the major pathways and enzymes responsible for testosterone and dihydrotestosterone synthesis are now well described. Minor or alternate pathways, which might contribute substantially to androgen production in specific states, have also emerged. Likewise, the requirement of androgen for prostate formation and growth date back over a half-century, and the dependence of prostate cancer on androgens has been known and exploited for as long. Despite the success of testicular removal or suppression, androgen receptor antagonists, and androgen synthesis inhibitors in the treatment of prostate cancer, the sources of androgen, their routes of synthesis, and the contributions of various routes remain topics of debate, particularly in castration-resistant disease when circulating androgens are very low. Here we review the major pathways of 19-carbon steroid synthesis in the adrenal and gonad, peripheral pathways to active androgens, and recent data charting flux of androgen precursors in prostate cancer. We are far from a unified understanding of androgen generation in prostate cancer, but the similarities and differences from glandular androgen synthesis that have already emerged provide important clues to designing the next generation of treatments for this common and devastating disease.

Pharmacology and clinical use of sex steroid hormone receptor modulators

Sex steroid receptors are ligand-triggered transcription factors. Oestrogen, progesterone and androgen receptors form, together with the glucocorticoid and mineralocorticoid receptors, a subgroup of the superfamily of nuclear receptors. They share a common mode of action, namely translating a hormone-i.e. a small-molecule signal-from outside to changes in gene expression and cell fate, and thereby represent "natural" pharmacological targets.For pharmacological therapy, these receptors have originally been addressed by hormones and synthetic hormone analogues in order to overcome pathologies related to deficiencies in the natural ligands. Another major use for female sex hormone receptor modulators is oral contraception, i.e. birth control.On the other side, blocking the activity of sex steroid receptors has become an established way to treat hormone-dependent malignancies, such as breast and prostate cancer.In this review, we will discuss how the experience gained from the classical pharmacology of these receptors and their molecular similarities led to new options for the treatment of gender-specific diseases and highlight recent progress in medicinal chemistry of sex hormone-modulating drugs.