Treatment Of Advanced Prostate Cancer Research Articles

Survival Trend in Individuals With De Novo Metastatic Prostate Cancer After the Introduction of Doublet Therapy

Recently, life-prolonging treatments for patients with advanced prostate cancer have been introduced in clinical practice. To investigate if the introduction of doublet therapy is associated with changes in survival on a population-basis. This nationwide population-based cohort study used data from the Prostate Cancer data Base Sweden from 2008 to 2020. Men registered with de novo metastatic castration-sensitive prostate cancer (mCSPC) were included. The proportion of men with mCSPC who received doublet therapy, ie, androgen deprivation therapy plus androgen receptor pathway inhibitor drugs or chemotherapy was assessed. Standardized overall survival, taking age, comorbidity, and cancer characteristics into consideration, was estimated by use of a parametric survival model. A total of 11 382 men were included in this study (median [IQR] age, 74.0 [68-81] years). There was a shift toward less advanced prostate cancer during the study period with a decrease in median (IQR) prostate-specific antigen at diagnosis in men with mCSPC from 145 (39-571) ng/mL to 107 (27-426) ng/mL. Upfront treatment with doublet therapy in these men simultaneously increased from 1% (7 of 991) in 2016 to 44% (402 of 922) in 2020. The adjusted 5-year overall survival increased from 26% (95% CI, 25%-28%) from 2008 to 2012 to 35% (95% CI, 31%-40%) from 2017 to 2020. During the first 5 years after diagnosis, there was an increase in mean survival of 6 months, from 2.7 (95% CI, 2.6-2.8) years from 2008 to 2012 to 3.2 (95% CI, 3.1-3.1) years from 2017 to 2020. In parallel with improvements in treatment of advanced prostate cancer, a clinically meaningful increase in mean survival was observed in men with de novo mCSPC in Sweden between 2008 and 2020 in this study.

1820P Cardiovascular effects of androgen receptor signalling inhibitors in the treatment of advanced and metastatic prostate cancer: A systematic review and meta-analysis of randomised controlled trials

1820P Cardiovascular effects of androgen receptor signalling inhibitors in the treatment of advanced and metastatic prostate cancer: A systematic review and meta-analysis of randomised controlled trials

A review of strategies to overcome immune resistance in the treatment of advanced prostate cancer.

Immunotherapy has become integral in cancer therapeutics over the past two decades and is now part of standard-of-care treatment in multiple cancer types. While various biomarkers and pathway alterations such as dMMR, CDK12, and AR-V7 have been identified in advanced prostate cancer to predict immunotherapy responsiveness, the vast majority of prostate cancer remain intrinsically immune-resistant, as evidenced by low response rates to anti-PD(L)1 monotherapy. Since regulatory approval of the vaccine therapy sipuleucel-T in the biomarker-unselected population, there has not been much success with immunotherapy treatment in advanced prostate cancer. Researchers have looked at various strategies to overcome immune resistance, including the identification of more biomarkers and the combination of immunotherapy with existing effective prostate cancer treatments. On the horizon, novel drugs using bispecific T-cell engager (BiTE) and chimeric antigen receptors (CAR) technology are being explored and have shown promising early efficacy in this disease. Here we discuss the features of the tumour microenvironment that predispose to immune resistance and rational strategies to enhance antitumour responsiveness in advanced prostate cancer.

The heterogeneity and clonal evolution analysis of the advanced prostate cancer with castration resistance

BackgroundNowadays, the incidence rate of advanced and metastatic prostate cancer at the first time of diagnosis grows higher in China yearly. At present, androgen deprivation therapy (ADT) is the primary treatment of advanced prostate cancer. However, after several years of ADT, most patients will ultimately progress to castration-resistant prostate cancer (CRPC). Previous studies mainly focus on Caucasian and very few on East Asian patients.MethodsIn this study, the pre- and post-ADT tumor samples were collected from five Chinese patients with advanced prostate cancer. The whole-exome sequencing, tumor heterogeneity, and clonal evolution pattern were analyzed.ResultsThe results showed that the gene mutation pattern and heterogeneity changed significantly after androgen deprivation therapy. Tumor Mutational Burden (TMB) and Copy Number Alteration (CNA) were substantially reduced in the post-treatment group, but the Mutant-allele tumor heterogeneity (MATH), Socio-Demographic Index (SDI), Intratumor heterogeneity (ITH), and weighted Genome Instability Index (wGII) had no significant difference. According to the clone types and characteristics, the presence of main clones in five pre-and post-treatment samples, the clonal evolution pattern can be further classified into two sub-groups (the Homogeneous origin clonal model or the Heterogeneous origin clonal model). The Progression-free survival (PFS) of the patients with the “Homogeneous origin clonal model” was shorter than the “Heterogeneous origin clonal model”. The longer PFS might relate to MUC7 and MUC5B mutations repaired. ZNF91 mutation might be responsible for resistance to ADT resistance.ConclusionOur findings revealed potential genetic regulators to predict the castration resistance and provide insights into the castration resistance processes in advanced prostate cancer. The crosstalk between clonal evolution patterns and tumor microenvironment may also play a role in castration resistance. A multicenter-research including larger populations with different background are needed to confirm our conclusion in the future.

Unleashing novel horizons in advanced prostate cancer treatment: investigating the potential of prostate specific membrane antigen-targeted nanomedicine-based combination therapy.

Prostate cancer (PCa) is a prevalent malignancy with increasing incidence in middle-aged and older men. Despite various treatment options, advanced metastatic PCa remains challenging with poor prognosis and limited effective therapies. Nanomedicine, with its targeted drug delivery capabilities, has emerged as a promising approach to enhance treatment efficacy and reduce adverse effects. Prostate-specific membrane antigen (PSMA) stands as one of the most distinctive and highly selective biomarkers for PCa, exhibiting robust expression in PCa cells. In this review, we explore the applications of PSMA-targeted nanomedicines in advanced PCa management. Our primary objective is to bridge the gap between cutting-edge nanomedicine research and clinical practice, making it accessible to the medical community. We discuss mainstream treatment strategies for advanced PCa, including chemotherapy, radiotherapy, and immunotherapy, in the context of PSMA-targeted nanomedicines. Additionally, we elucidate novel treatment concepts such as photodynamic and photothermal therapies, along with nano-theragnostics. We present the content in a clear and accessible manner, appealing to general physicians, including those with limited backgrounds in biochemistry and bioengineering. The review emphasizes the potential benefits of PSMA-targeted nanomedicines in enhancing treatment efficiency and improving patient outcomes. While the use of PSMA-targeted nano-drug delivery has demonstrated promising results, further investigation is required to comprehend the precise mechanisms of action, pharmacotoxicity, and long-term outcomes. By meticulous optimization of the combination of nanomedicines and PSMA ligands, a novel horizon of PSMA-targeted nanomedicine-based combination therapy could bring renewed hope for patients with advanced PCa.

Testosterone and Peripheral Arterial Disease.

Testosterone levels in men begin declining in the early years of adulthood, with a 1-2% reduction/year. Low testosterone levels in men are associated with obesity, metabolic syndrome, diabetes mellitus, dyslipidaemia, hypertension and increased cardiovascular mortality. However, observational studies of testosterone levels in males and their relationship with peripheral arterial disease (PAD) have yielded mixed results; only some cohorts show a clear association with low free testosterone levels. This discrepancy may, in part, be due to methodological issues with estimating free testosterone but also to different effects of testosterone on the vessel wall and metabolism. While testosterone improves glycaemic control, has anti-obesity effects and induces vasodilation, it also stimulates platelet aggregation and increases the haematocrit. Androgen deprivation treatment for advanced prostate cancer may be associated with elevated cardiovascular risk, as is testosterone abuse for performance enhancement. On the other hand, judicious treatment of male hypogonadism or testosterone treatment of trans-men appears to be safe.

Estimating the Impact of the Inflation Reduction Act on the Out-of-pocket Costs for Medicare Beneficiaries With Advanced Prostate Cancer.

Combination systemic therapy for advanced prostate cancer has reduced mortality, but high out-of-pocket costs impose financial barriers for patients. The Inflation Reduction Act's $2,000 out-of-pocket spending cap for Medicare's prescription drug benefit (Part D) can potentially lower out-of-pocket spending for beneficiaries starting in 2025. This study aims to compare out-of-pocket spending for commonly prescribed regimens for advanced prostate cancer before and after implementation of the Inflation Reduction Act. Medication regimens constructed to treat metastatic, hormone-sensitive prostate cancer consisted of baseline androgen deprivation therapy with traditional chemotherapy, androgen receptor inhibitors, and androgen biosynthesis inhibitors. Using 2023 Medicare Part B prices and the Medicare Part D plan finder, we estimated annual out-of-pocket costs under current law and under the Inflation Reduction Act's redesigned standard Part D benefit. Under current law, out-of-pocket costs for Part D drugs ranged from $464 to $11,336 per year. Under the Inflation Reduction Act, annual out-of-pocket costs for 2 regimens remained unchanged: androgen deprivation therapy with docetaxel and androgen deprivation therapy with abiraterone and prednisone. However, out-of-pocket costs for regimens using branded novel hormonal therapy were significantly lower under the 2025 law with potential savings estimated to be $9,336 (79.2%) for apalutamide, $9,036 (78.7%) for enzalutamide, and $8,480 (76.5%) for docetaxel and darolutamide. The $2,000 spending cap introduced by the Inflation Reduction Act may significantly decrease out-of-pocket costs and reduce financial toxicity associated with advanced prostate cancer treatment, impacting an estimated 25,000 Medicare beneficiaries.

Sambucus nigra agglutinin as a supporter of docetaxel treatment in metastatic prostate cancer

Androgen deprivation therapy (ADT) has been the first treatment for advanced prostate cancer. Although 90% of patients initially respond to ADT, the disease inevitably progresses to castration-resistant prostate cancer (CRPC). Docetaxel was reported to provide significant benefit over other chemotherapeutics in prolonging survival in CRPC. Recently, other chemotherapeutics have been used in cases where docetaxel is insufficient or the patient develops resistance, but yet their efficacy is limited. For this reason, it is necessary to develop docetaxel-based therapy, reduce toxicity, increase treatment efficiency. It has been shown that the non-toxic plant lectin Sambucus nigra agglutinin (SNA) drives ovarian cancer cells to the apoptotic pathway. Increased sialic acid levels in prostate cancer have suggested that SNA lectin, which binds to glycan sialic acid residues, may also have an activating effect on the apoptotic pathway for prostate cancer. In order to evaluate this, docetaxel and SNA were applied to DU-145 cells alone and in combination. Arterwards XTT cytotoxicity test, RNA isolation, cDNA synthesis, gene expression analysis by real time PCR method were performed. In our study, SNA alone did not show any effect on prostate cancer cells whereas it increased the efficacy of docetaxel. Furthermore, our study showed for the first time that SNA + docetaxel has a synergistic effect on the increase in Bim and decrease in Drp1expressions. Based on the data obtained from the current study, it is thought that the use of the SNA + docetaxel combination in the treatment of metastatic prostate cancer will increase the treatment efficacy.

Real-world Outcomes and Predictive Biomarkers for 177Lutetium Prostate-specific Membrane Antigen Ligand Treatment in Metastatic Castration-resistant Prostate Cancer: A European Association of Urology Young Academic Urologists Prostate Cancer Working Group Multi-institutional Observational Study

BackgroundThe European Association of Urology guidelines include the lutetium-177 (177Lu) PSMA-617 prostate-specific membrane antigen (PSMA) ligand as a therapy option for metastatic castration-resistant prostate cancer (mCRPC). A major challenge in clinical practice is to pursue a personalized treatment approach based on robust predictive biomarkers. ObjectiveTo assess the performance of 177Lu PSMA in real-world practice and to elaborate clinical biomarkers for evaluating treatment responses. Design, setting, and participantsWe conducted a retrospective observational study including 233 patients with mCRPC treated with 177Lu PSMA in eight high-volume European centers. Outcome measurements and statistical analysisBaseline characteristics and clinical parameters during and after 177Lu PSMA treatment were documented. Correlations to treatment response were analyzed using χ2 and log-rank tests, with differences between groups with and without disease progression calculated using a Mann-Whitney U test. Univariate and multivariate-adjusted hazard ratios (HRs) were measured using Cox proportional hazards models. Results and limitationsA prostate-specific antigen (PSA) decrease of ≥30% was observed in 41.7%, 63.5%, and 77.8% of patients after the first, second, and third treatment cycle, respectively. Restaging performed via PSMA positron emission tomography-computed tomography revealed that 33.7% of patients had an imaging-based response, including two patients with a complete response, while 13.4% had stable disease. The median time to progression was 5 mo and the median time until the start of a consecutive antineoplastic therapy was 8.5 mo. Of importance, a PSA decrease ≥30% after the first two cycles of 177Lu PSMA (1 cycle: p = 0.0003; 2 cycles: p = 0.004), absolute PSA after the first three cycles (1 cycle: p = 0.011; 2 cycles: p = 0.0005; 3 cycles: p = 0.002), and a PSA doubling time >6 mo (p = 0.009) were significantly correlated to treatment response. Furthermore, gamma-glutamyl transferase ≤31 U/L at the start of 177Lu PSMA therapy was correlated with 1.5 times higher risk of progression for patients without but not with visceral metastases (p = 0.046). Conclusions177Lu PSMA is an effective treatment option in mCRPC in the real-world setting. A PSA decrease ≥30% after the first two cycles is an early marker of response that can be easily implemented in clinical practice. Patient summary177Lu PSMA is a radioactive agent approved for treatment of advanced prostate cancer. We reviewed its use outside of clinical trials for patients treated at eight European centers. We found that 177Lu PSMA is an effective treatment option in real-world practice. A PSA (prostate-specific antigen) decrease of ≥30% after the first two therapy cycles is an early indicator of response to treatment and can be used in personalizing treatments for patients.

Discovery of potent pyrrolo-pyrimidine and purine HDAC inhibitors for the treatment of advanced prostate cancer

The development of drugs for the treatment of advanced prostate cancer (PCA) remains a challenging task. In this study we have designed, synthesized and tested twenty-nine novel HDAC inhibitors based on three different zinc binding groups (trifluoromethyloxadiazole, hydroxamic acid, and 2-mercaptoacetamide). These warheads were conveniently tethered to variously substituted phenyl linkers and decorated with differently substituted pyrrolo-pyrimidine and purine cap groups. Remarkably, most of the compounds showed nanomolar inhibitory activity against HDAC6. To provide structural insights into the Structure-Activity Relationships (SAR) of the investigated compounds, docking of representative inhibitors and molecular dynamics of HDAC6-inhibitor complexes were performed. Compounds of the trifluoromethyloxadiazole and hydroxamic acid series exhibited promising anti-proliferative activities, HDAC6 targeting in PCA cells, and in vitro tumor selectivity. Representative compounds of the two series were tested for solubility, cell permeability and metabolic stability, demonstrating favorable in vitro drug-like properties. The more interesting compounds were subjected to migration assays, which revealed that compound 13 and, to a lesser extent, compound 15 inhibited the invasive behaviour of androgen-sensitive and –insensitive advanced prostate cancer cells. Compound 13 was profiled against all HDACs and found to inhibit all members of class II HDACs (except for HDAC10) and to be selective with respect to class I and class IV HDACs. Overall, compound 13 combines potent inhibitory activity and class II selectivity with favorable drug-like properties, an excellent anti-proliferative activity and marked anti-migration properties on PCA cells, making it an excellent lead candidate for further optimization.

Interdisciplinary Swiss consensus recommendations on staging and treatment of advanced prostate cancer.

The management of prostate cancer is undergoing rapid changes in all disease settings. Novel imaging tools for diagnosis have been introduced, and the treatment of high-risk localized, locally advanced and metastatic disease has changed considerably in recent years. From clinical and health-economic perspectives, a rational and optimal use of the available options is of the utmost importance. While international guidelines list relevant pivotal trials and give recommendations for a variety of clinical scenarios, there is much room for interpretation, and several important questions remain highly debated. The goal of developing a national consensus on the use of these novel diagnostic and therapeutic strategies in order to improve disease management and eventually patient outcomes has prompted a Swiss consensus meeting. Experts from several specialties, including urology, medical oncology, radiation oncology, pathology and nuclear medicine, discussed and voted on questions of the current most important areas of uncertainty, including the staging and treatment of high-risk localized disease, treatment of metastatic hormone-sensitive prostate cancer (mHSPC) and use of new options to treat metastatic castration-resistant prostate cancer (mCRPC).

Current Trends in Chemotherapy in the Treatment of Metastatic Prostate Cancer.

Prostate cancer is the second most common cancer among men. Despite advances in diagnosis and management, prostate cancer led to more than 300,000 deaths globally in 2020. Chemotherapy is a cornerstone of therapy for advanced prostate cancer and can prolong survival of patients with both castration-sensitive and castration-resistant disease. Herein, we present a comprehensive review of the data supporting implementation of chemotherapy in the modern treatment of advanced prostate cancer, with special attention to the use of chemotherapy for aggressive variant prostate cancer (e.g., neuroendocrine prostate cancer) and the combination of chemotherapy with androgen signaling inhibitors. As the field of prostate cancer research continues to rapidly evolve yielding novel agents and treatment modalities, chemotherapy continues to play an essential role in prolonging the survival of patients with advanced and metastatic prostate cancer.

Profile of Relugolix in the Management of Advanced Hormone-Sensitive Prostate Cancer: Design, Development, and Place in Therapy.

Androgen deprivation therapy, primarily via a gonadotropin-releasing hormone receptor agonist or antagonist together with or without an androgen receptor antagonist, remains the mainstay of medical treatment for advanced prostate cancer. Meanwhile, relugolix has been developed as the first orally active, non-peptide, selective antagonist for the gonadotropin-releasing hormone receptor. Previous randomized studies involving patients with prostate cancer have demonstrated comparable efficacy in androgen suppression between relugolix vs other gonadotropin-releasing hormone antagonists or agonists. This review summarizes available data on the design and development of relugolix and its therapeutic application, and discusses if relugolix represents a promising oral alternative to injectable androgen deprivation therapy. Based on current published evidence, further investigation is likely required to determine the actual clinical benefits of relugolix therapy against prostate cancer.

Combination Nanotherapeutics for the Treatment of Advanced Prostate Cancer

Combination Nanotherapeutics for the Treatment of Advanced Prostate Cancer

Relugolix (Orgovyx) for advanced prostate cancer.

The oral gonadotropin-releasing hormone (GnRH) receptor antagonist relugolix (Orgovyx – Myovant Sciences/Pfizer) has been approved by the FDA for treatment of advanced prostate cancer in adults.

Bipolar Androgen Therapy: When Excess Fuel Extinguishes the Fire.

Androgen deprivation therapy (ADT) remains the cornerstone of advanced prostate cancer treatment. However, the progression towards castration-resistant prostate cancer is inevitable, as the cancer cells reactivate androgen receptor signaling and adapt to the castrate state through autoregulation of the androgen receptor. Additionally, the upfront use of novel hormonal agents such as enzalutamide and abiraterone acetate may result in long-term toxicities and may trigger the selection of AR-independent cells through "Darwinian" treatment-induced pressure. Therefore, it is crucial to develop new strategies to overcome these challenges. Bipolar androgen therapy (BAT) is one such approach that has been devised based on studies demonstrating the paradoxical inhibitory effects of supraphysiologic testosterone on prostate cancer growth, achieved through a variety of mechanisms acting in concert. BAT involves rapidly alternating testosterone levels between supraphysiological and near-castrate levels over a period of a month, achieved through monthly intramuscular injections of testosterone plus concurrent ADT. BAT is effective and well-tolerated, improving quality of life and potentially re-sensitizing patients to previous hormonal therapies after progression. By exploring the mechanisms and clinical evidence for BAT, this review seeks to shed light on its potential as a promising new approach to prostate cancer treatment.

Lineage plasticity and treatment resistance in prostate cancer: the intersection of genetics, epigenetics, and evolution.

Androgen deprivation therapy is a cornerstone of treatment for advanced prostate cancer, and the development of castrate-resistant prostate cancer (CRPC) is the primary cause of prostate cancer-related mortality. While CRPC typically develops through a gain in androgen receptor (AR) signaling, a subset of CRPC will lose reliance on the AR. This process involves genetic, epigenetic, and hormonal changes that promote cellular plasticity, leading to AR-indifferent disease, with neuroendocrine prostate cancer (NEPC) being the quintessential example. NEPC is enriched following treatment with second-generation anti-androgens and exhibits resistance to endocrine therapy. Loss of RB1, TP53, and PTEN expression and MYCN and AURKA amplification appear to be key drivers for NEPC differentiation. Epigenetic modifications also play an important role in the transition to a neuroendocrine phenotype. DNA methylation of specific gene promoters can regulate lineage commitment and differentiation. Histone methylation can suppress AR expression and promote neuroendocrine-specific gene expression. Emerging data suggest that EZH2 is a key regulator of this epigenetic rewiring. Several mechanisms drive AR-dependent castration resistance, notably AR splice variant expression, expression of the adrenal-permissive 3βHSD1 allele, and glucocorticoid receptor expression. Aberrant epigenetic regulation also promotes radioresistance by altering the expression of DNA repair- and cell cycle-related genes. Novel therapies are currently being developed to target these diverse genetic, epigenetic, and hormonal mechanisms promoting lineage plasticity-driven NEPC.

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.