Treatment Of Advanced Prostate Cancer Research Articles

Discovery of ARD-2051 as a Potent and Orally Efficacious Proteolysis Targeting Chimera (PROTAC) Degrader of Androgen Receptor for the Treatment of Advanced Prostate Cancer.

We report the discovery of ARD-2051 as a potent and orally efficacious androgen receptor (AR) proteolysis-targeting chimera degrader. ARD-2051 achieves DC50 values of 0.6 nM and Dmax >90% in inducing AR protein degradation in both the LNCaP and VCaP prostate cancer cell lines, potently and effectively suppresses AR-regulated genes, and inhibits cancer cell growth. ARD-2051 achieves a good oral bioavailability and pharmacokinetic profile in mouse, rat, and dog. A single oral dose of ARD-2051 strongly reduces AR protein and suppresses AR-regulated gene expression in the VCaP xenograft tumor tissue in mice. Oral administration of ARD-2051 effectively inhibits VCaP tumor growth and causes no signs of toxicity in mice. ARD-2051 is a promising AR degrader for advanced preclinical development for the treatment of AR+ human cancers.

Fibroblast-derived exosomal microRNA regulates NKX3-1 expression in androgen-sensitive, androgen receptor-dependent prostate cancer cells.

Androgen deprivation therapy (ADT) targeting androgen production and androgen receptor (AR) signaling is the primary antihormonal therapy in the treatment of advanced prostate cancer (PCa). However, no clinically established molecular biomarkers have been identified to predict the effectiveness of ADT before starting ADT. The tumor microenvironment of PCa contains fibroblasts that regulate PCa progression by producing multiple soluble factors. We have previously reported that AR-activating factor-secreted fibroblasts increase the responsiveness of androgen-sensitive, AR-dependent PCa cells to ADT. Thus, we hypothesized that fibroblast-derived soluble factors may affect cancer cell differentiation by regulating cancer-related gene expression in PCa cells and that the biochemical characteristics of fibroblasts may be used to predict the effectiveness of ADT. Here, we investigated the effects of normal fibroblasts (PrSC cells) and three PCa patient-derived fibroblast lines (pcPrF-M5, -M28, and -M31 cells) on the expression of cancer-related genes in androgen-sensitive, AR-dependent human PCa cells (LNCaP cells) and three sublines showing different androgen sensitivities and AR dependencies. The mRNA expression of the tumor suppressor gene NKX3-1 in LNCaP cells and E9 cells (which show low androgen sensitivity and AR dependency) was significantly increased by treatment with conditioned media from PrSC and pcPrF-M5 cells but not from pcPrF-M28 and pcPrF-M31 cells. Notably, no upregulation of NKX3-1 was observed in F10 cells (AR-V7-expressing, AR-independent cells with low androgen sensitivity) and AIDL cells (androgen-insensitive, AR-independent cells). Among 81 common fibroblast-derived exosomal microRNAs that showed 0.5-fold lower expression in pcPrF-M28 and pcPrF-M31 cells than in PrSC and pcPrF-M5 cells, miR-449c-3p and miR-3121-3p were found to target NKX3-1. In only LNCaP cells, the NKX3-1 mRNA expression was significantly increased by transfection of an miR-3121-3p mimic but not that of the miR-449c-3p mimic. Thus, fibroblast-derived exosomal miR-3121-3p may be involved in preventing the oncogenic dedifferentiation of PCa cells by targeting NKX3-1 in androgen-sensitive, AR-dependent PCa cells.

Abstract A077: MicroRNA drivers of resistance to androgen deprivation therapy in prostate cancer

Abstract INTRODUCTION: Prostate cancer is the most prevalent malignancy affecting Western males. It is initially an androgen-dependent disease: androgens bind to the androgen receptor and drive expression of genes that promote proliferation and evasion of apoptosis. Despite reduced androgen dependence in advanced prostate cancer, androgen receptor signalling remains a key driver of growth. Androgen deprivation therapy (ADT) is therefore a first line treatment approach and works well initially, but resistance inevitably develops. Abiraterone and Enzalutamide are drugs widely used in ADT and are androgen synthesis and androgen receptor signalling inhibitors respectively. The shortage of other treatment options means acquired resistance to these drugs is a major clinical problem. MicroRNAs (miRs) are important mediators of post-transcriptional gene regulation and show altered expression in cancer. Several have been linked to the development of resistance to ADT. Manipulation of such miRs may be a pathway to breakthrough treatments for advanced prostate cancer. This study aimed to validate ADT resistance-implicated miRs and their clinically relevant targets. MATERIALS AND METHODS: Small RNA-sequencing of Abiraterone- and Enzalutamide-resistant C42 prostate cancer cells identified subsets of miRs dysregulated as compared to parental cells. Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) was used to validate altered expression of candidate ADT resistance-implicated miRs 195-5p, 497-5p and 29a-5p in ADT-resistant and -responsive prostate cancer cell lines, patient-derived xenografts (PDXs) and primary prostate cancer explants. RESULTS AND DISCUSSION: This study suggests a possible role for miR-497-5p in the development of ADT resistance in prostate cancer. MiR-497-5p expression was increased in ADT-resistant versus ADT-responsive prostate cancer cells. Importantly, miR-497-5p expression was also increased in Enzalutamide-treated, castrated (ADT-mimicking) PDXs versus intact PDXs. MiR-195-5p was also elevated in ADT-resistant versus -responsive prostate cancer cells, while there was a drop in miR-29a-5p expression. Candidate clinically relevant targets of miR-497-5p in prostate cancer were identified by mining AGO-PAR-CLIP-seq data sets and may include AVL9 and FZD6. CONCLUSION: In summary, this study identified microRNAs that are implicated in prostate cancer resistance to androgen deprivation therapy and could represent novel therapeutic targets for advanced disease. Citation Format: Philippa C. Saunders, Claire Fletcher. MicroRNA drivers of resistance to androgen deprivation therapy in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A077.

Abstract PR010: First-in-class TRPV6 inhibitors for the treatment of prostate cancer

Abstract TRPV6, a calcium channel, is an oncochannel that is overexpressed in epithelial cancers including prostate cancer. We have developed a novel series of first-in-class small molecule TRPV6 inhibitors for the treatment of advanced prostate cancer. Our preclinical candidate QED-203 has been shown to inhibit calcium influx at low nM potency in TRPV6 cellular assays (FLIPR, electrophysiology), and has low nM potency in a TRPV6-driven NFAT assay (NFAT luciferase reporter). Inhibition of TRPV6 with our TRPV6 inhibitors or by siRNA knockdown causes changes in genes related to NFAT and WNT signalling, ER stress and the cell cycle (RNAseq and qPCR analysis), and causes cell cycle arrest, decreased proliferation and apoptosis in prostate cancer cells (demonstrated via imaging and FACS analysis). Importantly, QED-203 demonstrates potency in enzalutamide resistant cell lines (in vitro proliferation inhibition) and has superior potency over enzalutamide and darolutamide [androgen receptor targeting agents (ARTA)] in prostate cancer cell lines with clinically relevant AR mutations or the ARV7 splice variant. The ARV7 variant in particular is represented in a significant portion of patients no longer responding to ARTA SoC interventions. QED-203 has high bioavailability with a pharmacokinetic profile amenable to once-a-day oral dosing. QED-203 is well tolerated in rodents and has similar in vivo efficacy (tumour growth and PSA inhibition) to enzalutamide in a castrated LNCaP mouse model of prostate cancer. We have also shown QED-203 target engagement in rodents by demonstrating a change in calcium levels in the urine, and have observed changes in genes consistent with a TRPV6-specific mode of action in xenograft tumours (demonstrated via qPCR). QED-203 targets a novel, non-hormonal mechanism in prostate cancer, and could be used to treat prostate cancer patients who have developed resistance to AR therapies, where there is a large unmet need. Citation Format: Kimberley Beaumont, Rebecca Pouwer, Raphael Rahmani, Matthew McLachlan, Claire Levrier, Rebecca Farrow, Mei Yeh, Therese Johnson, Malika Kumarasiri, Hasanthi Wijesekera, Grant Stuchbury, Terrie-Anne Cock, Andrew Harvey, Gregory Monteith, Brian Dymock. First-in-class TRPV6 inhibitors for the treatment of prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr PR010.

Abstract PR008: Molecular determinants of prostate cancer lineage plasticity

Abstract Androgen deprivation therapy (ADT) has been an effective treatment for advanced prostate cancer (PCa) for decades because PCa retains the lineage specific dependence of normal prostate tissue on androgen receptor (AR) signaling. Unfortunately, nearly all patients will progress through ADT with castrate resistant prostate cancer (CRPC). CRPC is typically associated with reactivation of AR signaling despite ADT. However with widespread clinical deployment of potent AR signaling inhibitors, an increasing fraction of CRPCs (~20) are now observed to lose AR signaling activity and show gene expression patterns consistent with alternative lineage states. These lineage variants share clonal origin with the pre-existing adenocarcinoma, so some PCa cells have sufficient plasticity to reprogram to an AR independent lineage state like neuroendocrine prostate cancer (NEPC) that is recalcitrant to available therapies. The molecular determinants of prostate cancer lineage plasticity are incompletely defined, and this knowledge gap has hindered development of diagnostic and therapeutic approaches necessary to identify and treat prostate cancer lineage plasticity. We present results from experiments testing the contribution of EZH2 and NOTCH signaling to prostate cancer lineage plasticity and NEPC reprogramming. EZH2 expression is elevated in advanced PCa, particularly NEPC, suggesting it drives lineage reprogramming. However, using genetically engineered mice and organoids we find that EZH2 is not required for NEPC reprogramming that occurs in some PCa cells in the absence of the RB1 and TP53 tumor suppressor genes. EZH2 deficiency does alter multi-lineage prostate cancer plasticity, biasing development towards lineage variants observed clinically including amphicrine and double negative prostate cancer. In contrast, data from clinical specimens indicates NOTCH signaling activity declines in NEPC compared to AR+ CRPC. NOTCH signaling suppresses NEPC development in both organoids and genetically engineered mice, and loss of NOTCH signaling is required to maintain the NEPC lineage state. Constitutive NOTCH signaling biases PCa development towards unique lineage variants including AR positive metastatic PCa with luminal differentiation. These results identify EZH2 and NOTCH signaling as molecular determinants of PCa lineage plasticity and NEPC reprogramming with implications for ongoing efforts to target these molecules for PCa therapy. Citation Format: Kristine Wadosky, Sheng-Yu Ku, Yanqing Wang, Xiaojing Zhang, Jie Wang, Jianmin Wang, Himisha Beltran, David W. Goodrich. Molecular determinants of prostate cancer lineage plasticity [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr PR008.

Abstract A012: Adaptive and non-adaptive gene expression responses in prostate cancer during androgen deprivation

Abstract Development of novel and efficient treatments for advanced prostate cancer (PCa) requires better understanding of the cellular mechanisms behind the transition to castration resistant prostate cancer (CRPC). We created long-term cell cultures to model the development of castration resistance. Using a low passage VCaP cells as an initial model, we first created a highly testosterone-dependent PCa cell line (VCaP-T) and then a subclone cell line developing the ability to grow at low testosterone concentration (VCaP-CT). Adaptation to low testosterone was solely due to long term culturing and experimental work confirmed for example higher AR expression and antiandrogen resistance in VCaP-CT compared to VCaP-T. With the developed models we aimed to uncover persistent and adaptive responses to testosterone level and to identify genes that potentially contribute to transition and proliferation of the castration resistant cells through androgen receptor (AR) regulation. Expression levels were measured using RNA-seq. We defined AR-associated genes as the ones with changes due to testosterone depletion in VCaP-T (418 genes) and further adaptive genes as the ones that restored expression level in VCaP-CT (134 genes). Interestingly, we identified 151 genes that were non-AR-associated in VCaP-T but gained the association in VCaP-CT cells. Genes gaining the AR-association were also hypothesized to be important for CRPC progression and castration resistant cells. We validated and assessed the clinical significance of the model and the findings using The Cancer Genome Atlas Prostate Adenocarcinoma data and multivariate Cox regression analysis. Expressions of 47 AR-associated or association gaining genes were statistically significant markers for progression-free survival. These included genes related to immune response, adhesion and transport. Genes ABCC5, SPRED3, TMPRSS11F, SPARC, SLC1A1, SATB1, PDGFRB and C1QTNF6 showed strong evidence being associated with tumor stage and aggressiveness in addition to progression-free survival. Taken together, we identified and validated multiple genes being linked with progression of prostate cancer and proposed several novel risk genes. These findings increase knowledge on mechanisms of castration resistance and may open new possibilities for treatments. Identified genes have potential to be used as biomarkers or therapeutic targets after further studies. Citation Format: Reetta Nätkin, Pasi Pennanen, Heimo Syvälä, Merja Bläuer, Juha Kesseli, Teuvo L.J. Tammela, Matti Nykter, Teemu J. Murtola. Adaptive and non-adaptive gene expression responses in prostate cancer during androgen deprivation [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A012.

Abstract B019: A synthetic lethal screen for Snail-induced enzalutamide resistance identifies JAK/STAT signaling as a therapeutic vulnerability in prostate cancer

Abstract Despite substantial improvements in the treatment landscape of prostate cancer, the evolution of hormone therapy-resistant and metastatic prostate cancer remains a major cause of cancer-related death globally. The mainstay of treatment for advanced prostate cancer is targeting of androgen receptor signaling, including androgen deprivation therapy plus second-generation androgen receptor blockade (e.g., enzalutamide, apalutamide, darolutamide), and/or androgen synthesis inhibition (abiraterone). While these agents have significantly prolonged the lives of patients with advanced prostate cancer, the evolution of resistance to these treatments in nearly universal. This therapy resistance is mediated by diverse mechanisms, including both androgen receptor-dependent mechanisms, such as androgen receptor mutations, amplifications, alternatively spliced isoforms, and structural rearrangements, as well as non-androgen receptor-mediated mechanisms, such as lineage plasticity toward neuroendocrine-like or epithelial-mesenchymal transition (EMT)-like lineages. Our prior work identified the EMT transcriptional regulator Snail as critical to hormonal therapy resistance and commonly detected in human metastatic prostate cancer. In the current study, we sought to interrogate the actionable landscape of EMT-mediated hormone therapy-resistant prostate cancer to identify synthetic lethality and collateral sensitivity approaches to treating this aggressive disease state. Using a combination of high-throughput drug screens and multi-parameter phenotyping by confluence imaging, ATP production, and phenotypic plasticity reporters of EMT, we identified candidate synthetic lethalities to Snail-mediated EMT in prostate cancer. These analyses identified multiple actionable targets, such as XPO1, PI3K/mTOR, aurora kinases, c-MET, polo-like kinases, and JAK/STAT as synthetic lethalities in Snail+ prostate cancer. We validated these targets in a subsequent validation screen in an LNCaP-derived model of resistance to sequential androgen deprivation and enzalutamide. This follow-up screen provided validation of inhibitors of JAK/STAT and PI3K/mTOR as therapeutic vulnerabilities for Snail+ and enzalutamide-resistant prostate cancer. Citation Format: Kathryn E. Ware, Beatrice C. Thomas, Pelumi Olawuni, Maya U. Sheth, Nathan Hawkey, Yeshwanth M, Brian C. Miller, Katherine J. Vietor, Mohit Kumar Jolly, So Young Kim, Andrew J. Armstrong, Jason A. Somarelli. A synthetic lethal screen for Snail-induced enzalutamide resistance identifies JAK/STAT signaling as a therapeutic vulnerability in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B019.

Association of Androgen Deprivation Therapy with Metabolic Disease in Prostate Cancer Patients: An Updated Meta-Analysis.

Androgen deprivation therapy (ADT), a backbone treatment for advanced prostate cancer (PC), is known to have a variety of metabolic side effects. We conducted an updated meta-analysis to quantify the metabolic risks of ADT. We searched PubMed, Web of Science, and Scopus in May of 2022 for studies investigating the risk of metabolic syndrome (MetS), diabetes, and hypertension from ADT in PC patients using keywords. Only full-length studies with a control group of PC patients not on ADT were included. All results compatible with each outcome domain in each included study were sought. For included studies, relative risk (RR) was pooled using a random effects model and a trim-fill approach was used to adjust for publication bias. 1,846 records were screened, of which 19 were found suitable for data extraction. Five studies, including 891 patients, were evaluated for MetS as an outcome, with the random effects model showing a pooled RR of 1.60 ([95% Confidence Interval (CI), 1.06-2.42]; P=0.03) for patients on ADT while twelve studies, including 336,330 patients, examined diabetes as an outcome, and the random effects model showed a RR of 1.43 ([95% CI, 1.28-1.59]; P< 0.01). After adjustment for publication bias, ADT was associated with a 25% increased risk for diabetes but was not associated with MetS. 4 studies, including 7,051 patients, examined hypertension as an outcome, and the random effects model showed a RR of 1.30 ([95% CI, 1.08-1.55]; P=0.18) in ADT patients. In patients with PC, ADT was not associated with MetS and the association with diabetes was not as strong as previously reported. Our novel meta-analysis of hypertension showed that ADT increased the risk of hypertension by 30%. These results should be understood in the context of collaborating care between a patient's oncologist and primary care provider to optimize care.

Perioperative safety and outcomes following radical prostatectomy in setting of locally advanced, node positive, and metastatic prostate cancer.

e17108 Background: Historically, definitive surgical management with radical prostatectomy (RP) has only been considered an option for the treatment of localized prostate cancer (PCa). However, recent data may suggest a role for RP in advanced PCa treatment. Currently, there is limited data on the safety and perioperative outcomes of RP in this setting. Here, we aim to compare the perioperative outcomes of RP for locally advanced, node positive, and metastatic PCa using the American College of Surgeons National Surgical Quality Improvement Project (NSQIP) new procedure targeted database. Methods: RP procedures performed between 2019-2020 were identified. Patients were stratified to compare the effect of locally advanced disease (T3-4), node-positivity (N+), and metastasis (M+) against patients with localized (T1-2 N0 M0) PCa. Baseline demographics and 30-day outcomes, including operative time, hospital length-of-stay, 30-day mortality, readmissions, reoperations, major complications, minor complications, and surgery-specific complications, were compared between groups. Results: Pathologic staging data was available for 9,276 RPs. Baseline demographics were comparable. There was a slightly higher rate of minor-complications in the locally-advanced cohort, but no significant difference in major-complications, 30-day-mortality, readmissions, or rectal injuries. In comparison, while node-positivity was associated with longer operative time, LOS, and incidence of 30-day renal failure, it was not associated with a higher rate of any major, minor or surgery-specific complication. Similarly, RP for metastatic cases appeared to be comparably safe to those with M0 disease, although they were associated with a slightly higher rate of bleeding, prolonged-NG-tube use, and ureteral obstruction. Conclusions: RP for patients with locally advanced, node positive, and metastatic prostate cancer appears to be safe, and is not associated with significantly higher rates of 30-day mortality or major complications compared to localized prostate cancer. Given the previously demonstrated survival benefit in treating the primary tumor in advanced disease with radiation therapy, there may be a role for the RP in treating advanced PCa. Further studies are needed to better characterize the risks and benefits of surgery in these patients.

Assessing racial differences in time to treatment escalation following androgen-deprivation therapy among veterans with prostate cancer.

5078 Background: Androgen deprivation therapy (ADT) is standard care first-line (1L) systemic treatment for advanced and metastatic prostate cancer (PC). Currently, there are no population-level studies assessing the duration of 1L ADT and time to treatment escalation (chemotherapy [CT], novel hormonal therapy [NHT], or non-steroidal antiandrogen [NSAA]). Methods: We performed a retrospective population-level analysis to assess the association between race and time to treatment escalation after ADT in the Veterans Affairs Health Care System. From 2001-2021, 164,477 patients (pt) diagnosed with PC and treated with ADT alone were identified. Baseline demographic and clinical characteristics were sorted by race: Non-Hispanic White (NHW), Non-Hispanic Black (NHB), Hispanic, Other and compared among groups using chi square tests for categorical variables and Kruskal-Wallis tests for continuous variables. The primary outcome was time from ADT to treatment escalation, defined as receipt of NHT, NSAA, or CT. Men with no evidence of treatment escalation were censored at time of death or most recent visit. We estimated 5-year event rates by race using Kaplan-Meier (KM) analyses. Univariable and multivariable Cox proportional hazards models were used to test the association between race and time to treatment escalation with time of ADT as time zero. Multivariable models were adjusted for age, year, time from PC diagnosis to ADT, Charlson Comorbidity Index and BMI at ADT start along with PSA, testosterone level, and receipt of radiation therapy (RT) prior to ADT. Results: NHB were youngest (p&lt;0.001), started ADT in more recent years (p&lt;0.001), had the highest pre-ADT PSA (p&lt;0.001) and testosterone levels (p&lt;0.001), the most comorbidities (p&lt;0.001), and the highest rate of RT prior to ADT (p&lt;0.001) relative to other groups. During a median (Q1, Q3) follow-up of 55.2 (25.0, 102.4) months, 31,288 pt (19%) had treatment escalation, of which 12,093 (39%) were NHTs, 14,842 (47%) were NSAAs, 3,895 (12%) were CT and 458 (2%) were other 2nd line therapies. Compared to NHW, NHB had significantly lower rate of treatment escalation in univariable (HR=0.89, 95% CI=0.87-0.92) and multivariable analysis (HR=0.82, 95% CI=0.80-0.84). KM estimates at 5-year for the percent free from escalation was 80.5 (80.2-80.8%) in NHW vs. 83.0 (82.6-83.4%) in NHB. Rate of treatment escalation was similar for Hispanics and other races compared to NHW, with 5-year KM estimates of 81.0 (80.3-81.7%) and 81.0 (80.0-82.0%) for Hispanics and other races, respectively. Conclusions: This study assessing racial differences in time to treatment escalation of men receiving 1L ADT found that NHB had a significantly lower rate of treatment escalation. Whether this decreased rate of treatment escalation among NHB men represents improved outcomes (i.e. lower risk of progression) or undertreatment requires further study.

CO209 Association between Baseline Bone Mineral Density Testing and the Risk of Fractures in Men Initiating Androgen Deprivation Therapy: Population-Based Study

Androgen deprivation therapy (ADT) is a staple of advanced prostate cancer (PCa) treatment, however several side-effects are associated with its long-term use. Notably, loss of bone mineral density (BMD) is accelerated which increases fracture risk. Although guidelines recommend BMD testing when initiating ADT to properly assess baseline fracture risk, there is scarce data to support this recommendation in the PCa patient population. The objective was to examine the association between baseline BMD testing (bBMDT) and the risk of fractures in men initiating ADT for PCa.

Validation of an LC-MS/MS method for simultaneous quantification of abiraterone, enzalutamide and darolutamide in human plasma

Currently, several oral androgen receptor signalling inhibitors are available for the treatment of advanced prostate cancer. Quantification of plasma concentrations of these drugs is highly relevant for various purposes, such as Therapeutic Drug Monitoring (TDM) in oncology. Here, we report a liquid chromatography/tandem mass spectrometric (LC–MS/MS) method for the simultaneous quantification of abiraterone, enzalutamide, and darolutamide. The validation was performed according to the requirements of the U.S. Food and Drug Administration and European Medicine Agency. We also demonstrate the clinical applicability of the quantification of enzalutamide and darolutamide in patients with metastatic castration-resistant prostate cancer.

Prostate cancer and bone: clinical presentation and molecular mechanisms.

Prostate cancer (PCa) is an increasingly prevalent health problem in the developed world. Effective treatment options exist for localized PCa, but metastatic PCa has fewer treatment options and shorter patient survival. PCa and bone health are strongly entwined, as PCa commonly metastasizes to the skeleton. Since androgen receptor signaling drives PCa growth, androgen-deprivation therapy whose sequelae reduce bone strength constitutes the foundation of advanced PCa treatment. The homeostatic process of bone remodeling - produced by concerted actions of bone-building osteoblasts, bone-resorbing osteoclasts, and regulatory osteocytes - may also be subverted by PCa to promote metastatic growth. Mechanisms driving skeletal development and homeostasis, such as regional hypoxia or matrix-embedded growth factors, may be subjugated by bone metastatic PCa. In this way, the biology that sustains bone is integrated into adaptive mechanisms for the growth and survival of PCa in bone. Skeletally metastatic PCa is difficult to investigate due to the entwined nature of bone biology and cancer biology. Herein, we survey PCa from origin, presentation, and clinical treatment to bone composition and structure and molecular mediators of PCa metastasis to bone. Our intent is to quickly yet effectively reduce barriers to team science across multiple disciplines that focuses on PCa and metastatic bone disease. We also introduce concepts of tissue engineering as a novel perspective to model, capture, and study complex cancer-microenvironment interactions.

Pharmacokinetics, safety, and antitumor activity of talazoparib monotherapy in Chinese patients with advanced solid tumors

Talazoparib, a poly(ADP-ribose) polymerase inhibitor, has demonstrated efficacy in the treatment of advanced breast and prostate cancers in Western populations. This open-label, phase 1 study investigated the pharmacokinetics, safety, and antitumor activity of talazoparib monotherapy in Chinese patients with advanced solid tumors. Molecularly unselected patients (≥18 years) with advanced solid tumors resistant to standard therapy received talazoparib (oral, 1 mg once daily). Primary endpoint was characterization of single-dose and steady-state pharmacokinetics. Secondary endpoints evaluated safety, unconfirmed objective response rate (ORR), and duration of response. The safety population comprised 15 Chinese patients (median [range] age 53.0 [31.0–72.0] years). Single-dose median time to first occurrence of maximum observed concentration was 1.9 h; concentrations then declined with a mean terminal half-life (t1/2) of 67 h. Following multiple dosing, median Tmax was approximately 1.85 h with steady state generally achieved by Day 21. Treatment-related treatment-emergent adverse events (TEAEs) occurred in 86.7% (13/15) of patients (grade 3, 20.0%; grade 4, 13.3%). Two patients (13.3%) experienced serious treatment-related TEAEs. ORR (investigator-assessed) was 6.7% (95% CI: 0.2–31.9); one patient (6.7%) had a partial response. In patients with measurable disease at baseline, the ORR was 9.1% (1/11; 95% CI: 0.2–41.3; duration of response: 114 days); stable disease was achieved by 36.4% (4/11) of patients, and 54.5% (6/11) progressed by data cut-off. In Chinese patients with advanced solid tumors, the pharmacokinetic profile of talazoparib monotherapy (1 mg/day) was consistent with other patient populations. TEAEs were generally manageable with no unexpected safety findings. (ClinicalTrials.gov: NCT04635631 [prospectively registered November 19, 2020])

A synthetic lethal screen for Snail-induced enzalutamide resistance identifies JAK/STAT signaling as a therapeutic vulnerability in prostate cancer.

Despite substantial improvements in the treatment landscape of prostate cancer, the evolution of hormone therapy-resistant and metastatic prostate cancer remains a major cause of cancer-related death globally. The mainstay of treatment for advanced prostate cancer is targeting of androgen receptor signaling, including androgen deprivation therapy plus second-generation androgen receptor blockade (e.g., enzalutamide, apalutamide, darolutamide), and/or androgen synthesis inhibition (abiraterone). While these agents have significantly prolonged the lives of patients with advanced prostate cancer, is nearly universal. This therapy resistance is mediated by diverse mechanisms, including both androgen receptor-dependent mechanisms, such as androgen receptor mutations, amplifications, alternative splicing, and amplification, as well as non-androgen receptor-mediated mechanisms, such as lineage plasticity toward neuroendocrine-like or epithelial-mesenchymal transition (EMT)-like lineages. Our prior work identified the EMT transcriptional regulator Snail as critical to hormonal therapy resistance and is commonly detected in human metastatic prostate cancer. In the current study, we sought to interrogate the actionable landscape of EMT-mediated hormone therapy resistant prostate cancer to identify synthetic lethality and collateral sensitivity approaches to treating this aggressive, therapy-resistant disease state. Using a combination of high-throughput drug screens and multi-parameter phenotyping by confluence imaging, ATP production, and phenotypic plasticity reporters of EMT, we identified candidate synthetic lethalities to Snail-mediated EMT in prostate cancer. These analyses identified multiple actionable targets, such as XPO1, PI3K/mTOR, aurora kinases, c-MET, polo-like kinases, and JAK/STAT as synthetic lethalities in Snail+ prostate cancer. We validated these targets in a subsequent validation screen in an LNCaP-derived model of resistance to sequential androgen deprivation and enzalutamide. This follow-up screen provided validation of inhibitors of JAK/STAT and PI3K/mTOR as therapeutic vulnerabilities for both Snail+ and enzalutamide-resistant prostate cancer.

Novel hormone treatment for advanced prostate cancer

The systemic treatment of advanced prostate cancer (PCa) has undergone an absolute revolution in the past decade. Numerous new substances have been approved for all stages of advanced disease and treatment has been increasingly intensified. The focus continues to be on substances with an effect on the androgen receptor axis. In this review, approved treatment options for metastatic hormone-sensitive PCa (mHSPC), non-metastatic castration-refractory PCa (nmCRPC) and metastatic castration-refractory PCa (mCRPC) are summarized. A special focus is on novel hormone therapeutic agents. Based on recent trial data, potential triple combinations for mHSPC as well as treatment sequence options and novel targeted agents for mCRPC are also highlighted.

IL-1β Is an Androgen-Responsive Target in Macrophages for Immunotherapy of Prostate Cancer.

Great attention is paid to the role of androgen receptor (AR) as a central transcriptional factor in driving the growth of prostate cancer (PCa) epithelial cells. However, the understanding of the role of androgen in PCa-infiltrated immune cells and the impact of androgen deprivation therapy (ADT), the first-line treatment for advanced PCa, on the PCa immune microenvironment remains limited. On the other hand, immune checkpoint blockade has revolutionized the treatment of certain cancer types, but fails to achieve any benefit in advanced PCa, due to an immune suppressive environment. In this study, it is reported that AR signaling pathway is evidently activated in tumor-associated macrophages (TAMs) of PCa both in mice and humans. AR acts as a transcriptional repressor for IL1B in TAMs. ADT releases the restraint of AR on IL1B and therefore leads to an excessive expression and secretion of IL-1β in TAMs. IL-1β induces myeloid-derived suppressor cells (MDSCs) accumulation that inhibits the activation of cytotoxic T cells, leading to the immune suppressive microenvironment. Critically, anti-IL-1β antibody coupled with ADT and the immune checkpoint inhibitor anti-PD-1 antibody exerts a stronger anticancer effect on PCa following castration. Together, IL-1β is an important androgen-responsive immunotherapeutic target for advanced PCa.

Genome-wide association studies in advanced prostate cancer: KYUCOG-1401-A study.

Androgen deprivation therapy (ADT) has been widely used for the treatment of advanced prostate cancer. However, prognosis and adverse events vary among patients. This study aimed to identify genetic markers able to predict the outcome of ADT. Japanese patients treated with primary ADT for advanced prostate cancer in the KYUCOG-1401 trial were enrolled as a development set. A distinct population of advanced prostate cancer cases treated with ADT was included as a validation set. Single-nucleotide polymorphisms (SNPs) associated with radiographic progression-free survival (PFS) at 1 year and adverse events including de novo diabetes mellitus, arthralgia, and de novo dyslipidemia were identified in the development set by a genome-wide association study (GWAS). The SNPs associated with radiographic PFS in the development study were then genotyped in the validation set. GWAS followed by validation identified SNPs (rs76237622 in PRR27 and rs117573572 in MTAP) that were associated with overall survival in ADT. A genetic prognostic model using these SNPs showed excellent predictive efficacy for PFS and overall survival in ADT. In addition, GWAS showed that several SNPs were associated with de novo diabetes mellitus, arthralgia, and de novo dyslipidemia in ADT. This study identified novel multiple SNPs that correlated with outcomes in ADT. Future studies on correlations affecting the therapeutic efficacy of ADT-based combination therapies would make a valuable contribution to the development of personalized medicine.

A Phase I Clinical Trial Evaluating the Safety and Dosing of Relugolix with Novel Hormonal Therapy for the Treatment of Advanced Prostate Cancer.

Androgen deprivation therapy (ADT), a cornerstone of prostate cancer treatment, is commonly co-prescribed as combination therapy. To better understand the safety and tolerability profile of relugolix, an oral non-peptide gonadotropin-releasing hormone (GnRH) receptor antagonist, in combination with abiraterone acetate (abiraterone) and apalutamide, a phase I study was undertaken. This is an ongoing, 52-week, open-label, parallel cohort study of relugolix in combination with abiraterone in men with metastatic castration-sensitive prostate cancer (mCSPC) or metastatic castration-resistant prostate cancer (mCRPC) [Part 1] and apalutamide in men with mCSPC or non-metastatic castration-resistant prostate cancer (nmCRPC) [Part 2]. Eligible patients treated with leuprolide acetate or degarelix with abiraterone or apalutamide prior to baseline, at which time they were transitioned to relugolix. Assessments included reporting of adverse events, clinical laboratory tests, vital sign measurements, electrocardiogram (ECG) parameters, and testosterone serum concentrations. In this interim report, patients completing ≥12 weeks were included. Overall, 15 men were enrolled in Part 1 and 10 in Part 2. Adverse events were mostly mild-to-moderate in intensity and were consistent with the known safety profiles of the individual medications. No transition (from prior ADT treatment)- or time-related trends in clinical laboratory tests, vital sign measurements, or ECG parameters were observed. Mean testosterone concentrations remained below castration levels. Combination therapy of relugolix and abiraterone or apalutamide was associated with a favorable safety and tolerability profile consistent with the known profiles of the individual medications. Castration levels of testosterone were maintained after transitioning to relugolix from other ADTs. ClinicalTrials.gov identifier: NCT04666129.

Abstract LB262: HSK38008: An oral AR-V7 degrader for metastatic castration-resistant prostate cancer

Abstract The androgen deprivation therapy (ADT) alone and its combination with hormone therapy that block AR signaling (e.g., enzalutamide or abiraterone) are effective treatments for advanced prostate cancer. Unfortunately, patients with truncated AR splice variants which lacking the ligand-binding domain still developed resistance to these AR-targeting compounds. The truncated AR splice variant 7 (AR-V7), which is the most clinically relevant variants, remains constitutively active as a transcription factor in 75% of the patients with mCRPC, associated with shorter PFS and OS with abiraterone or enzalutamide treatment. Therefore, AR-V7 has become a promising target for mCRPC.As a novel oral AR-V7 degrader with favorable bioavailability, HSK38008 could degrade the AR-V7 protein with DC50 of 136 nM and achieve the maximum degradation at 24h at 10 μM. In the meanwhile, HSK38008 also degrade AR with weaker IC50 of 110 nM and the maximum degradation at 48hrs at 10 μM. By validation of protease inhibitor MG341, HSK38008 could not degrade ARV7 and AR at high concentration. Compared with enzalutamide and ARV-110, HSK38008 could block the AR-V7 pathway and AR pathway in luciferase report assay with IC50 of 400 nM and 1913 nM respectively. Importantly, HSK38008 also showed significant inhibition of AR mutants (AR-T878A/S889G, T878S, H875Y, T878A) in luciferase assay but not ARV110 and enzalutamide. HSK38008 significantly inhibit the cell proliferation in AR-V7 positive cell line, e.g., 22RV1, but weak antiproliferation in AR and ARV7 positive cell line such as VCAP However, when combination with enzalutamide there is synergistic effect for the anti-proliferation in VCAP. It means the potential to use the compounds in a broader population of mCRPC.In the xenograft model, the mice which were orally given HSK38008 showed 22RV1 tumor growth inhibition in a dose-dependent manner, with the TGI = 89.8% at 10 mpk and the intratumoral AR-V7 protein degradation rate was 73%. 30 mpk of HSK38008 showed completely tumor regression. At the same time, abiraterone and ARV-110 did not show significantly tumor growth inhibition at 30 mpk. There is no influence on mice body weight at all HSK38008 dose groups, while 3 mice in the 30 mpk of ARV-110 group died during the experiment. These results indicated that HSK38008 achieved better therapeutic effects than enzalutamide and ARV-110 did in AR-V7 positive 22RV1 xenograft model.Rats were dosed with 10, 30 and 60 mg/kg HSK38008 once daily for up to 28 days via oral gavage and main study animals were necropsied on Day 29 or Day 57. No animal was found dead or moribund and no test article-related changes in clinical signs, body weights, food consumption, ophthalmologic examinations, clinical pathology parameters, sperm analysis, urinalysis, organ weights, histopathology. In conclusion, HSK38008 is a promising oral AR-V7 degrader with better efficacy than enzalutamide and ARV-110 in AR and AR-V7 positive, and potential AR mutants mCRPC. Citation Format: Ju Wang, Meilin Qian, Pangke Yan, Linli Li, Chen Zhang, Yan Yu, Lihua Tao, Pingming Tang, Yuting Liao, Xiaogang Chen, Xinfan Cheng, Jinxiong Xu, Xuemei Wan, Luchan Deng, Hongjiao Dong, Haixian Zhang, Maotao He. HSK38008: An oral AR-V7 degrader for metastatic castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB262.