Benjamin Louis Maughan

Clinical Significance of Androgen Receptor Splice Variant-7 mRNA Detection in Circulating Tumor Cells of Men With Metastatic Castration-Resistant Prostate Cancer Treated With First- and Second-Line Abiraterone and Enzalutamide

Purpose We reported previously that the detection of androgen receptor splice variant-7 (AR-V7) mRNA in circulating tumor cells (CTCs) correlated with poor outcomes from the use of abiraterone and enzalutamide in patients with castration-resistant prostate cancer (CRPC). Here, we expanded our cohort size to better characterize the prognostic significance of AR-V7 in this setting. Methods We prospectively enrolled 202 patients with CRPC starting abiraterone or enzalutamide and investigated the prognostic value of CTC detection (+ v -) and AR-V7 detection (+ v -) using a CTC-based AR-V7 mRNA assay. We examined ≥ 50% prostate-specific antigen (PSA) responses, PSA progression-free survival, clinical and radiologic progression-free survival, and overall survival. We constructed multivariable models adjusting for PSA, Gleason sum, number of prior hormone therapies, prior abiraterone or enzalutamide use, prior taxane use, presence of visceral metastases, and Eastern Cooperative Oncology Group score. We also separately examined the first-line and second-line novel hormonal therapy (NHT) settings. Results Median follow-up times were 15.0, 21.7, and 14.6 months for CTC-, CTC+/AR-V7- and CTC+/AR-V7+ patients, respectively. CTC+/AR-V7+ patients were more likely to have Gleason scores ≥ 8 ( P = .05), metastatic disease at diagnosis ( P = .01), higher PSA ( P < .01), prior abiraterone or enzalutamide use ( P = .03), prior taxane use ( P = .02), and Eastern Cooperative Oncology Group ≥ 1 ( P = .01). Outcomes for the overall cohort (and separately for the first-line and second-line NHT cohorts) were best for CTC- patients, intermediate for CTC+/AR-V7- patients, and worse for CTC+/AR-V7+ patients. These correlations remained significant in multivariable models. Conclusion This expanded analysis further characterizes the importance of CTC-based AR-V7 mRNA detection in predicting outcomes in patients with CRPC receiving first- and second-line NHT and, to the best of our knowledge, is the first to suggest that this assay be interpreted using three separate prognostic categories: CTC-, CTC+/AR-V7-, and CTC+/AR-V7+.

Comparing Sequencing of Abiraterone and Enzalutamide in Men With Metastatic Castration‐Resistant Prostate Cancer: A Retrospective Study

There are no validated clinical decision tools to aid optimal treatment selection in men with metastatic castration‐resistant prostate cancer (mCRPC). Frequently, abiraterone and enzalutamide are used prior to chemotherapy in mCRPC, given the more favorable safety profiles. However, there is no published data on clinical outcomes regarding best sequencing of these two agents.

Androgen pathway resistance in prostate cancer and therapeutic implications

Introduction: Metastatic prostate cancer is an incurable disease that is treated with a variety of hormonal therapies targeting various nodes of the androgen receptor (AR) pathway. Invariably patients develop resistance and become castration resistant. Common treatments for castration-resistant disease include novel hormonal therapies, such as abiraterone and enzalutamide, chemotherapy, immunotherapy and radiopharmaceuticals. As this disease generally remains incurable, understanding the molecular underpinnings of resistance pathways is critical in designing therapeutic strategies to delay or overcome such resistance. Areas covered: This review will explore the resistance mechanisms relevant to hormonal agents, such as AR-V7 expression and others, as well as discussing new approaches being developed to treat patients with castration-resistant prostate cancer that take advantage of these new insights. A literature search was performed to identify all published clinical trials related to androgen therapy mechanisms of drug resistance in metastatic castration-resistant prostate cancer. Expert opinion: Androgen therapy resistance mechanisms are varied, and include modification of all nodes in the androgen signaling pathway. The optimal treatment for men with relapsed metastatic castration-resistant prostate cancer is uncertain at this time. The authors recommend using available clinical data to guide treatment decision making until more specific biomarkers are clinically available.

Six-month progression-free survival as the primary endpoint to evaluate the activity of new agents as second-line therapy for advanced urothelial carcinoma.

OBJECTIVE Second-line systemic therapy for advanced urothelial carcinoma (UC) has substantial unmet needs, and current agents show dismal activity. Second-line trials of metastatic UC have used response rate (RR) and median progression-free survival (PFS) as primary endpoints, which may not reflect durable benefits. A more robust endpoint to identify signals of durable benefits when investigating new agents in second-line trials may expedite drug development. PFS at 6 months (PFS6) is a candidate endpoint, which may correlate with overall survival (OS) at 12 months (OS12) and may be applicable across cytostatic and cytotoxic agents. METHODS Ten second-line phase II trials with individual patient outcomes data evaluating chemotherapy or biologics were combined for discovery, followed by external validation in a phase III trial. The relationship between PFS6/RR and OS12 was assessed at the trial level using Pearson correlation and weighted linear regression, and at the individual level using Pearson chi-square test with Yates continuity correction. RESULTS In the discovery dataset, a significant correlation was observed between PFS6 and OS12 at the trial (R(2) = 0.55, Pearson correlation = 0.66) and individual levels (82%, Қ = 0.45). Response correlated with OS12 at the individual level less robustly (78%, Қ = 0.36), and the trial level association was not statistically significant (R(2) = 0.16, Pearson correlation = 0.37). The correlation of PFS6 (81%, Қ = 0.44) appeared stronger than the correlation of response (76%, Қ = 0.17) with OS12 in the external validation dataset. CONCLUSIONS PFS6 is strongly associated with OS12 and appears more optimal than RR to identify active second-line agents for advanced UC.

Clinical Relevance of Androgen Receptor Splice Variants in Castration-Resistant Prostate Cancer

Opinion statementMetastatic castration-resistant prostate cancer (mCRPC) currently benefits from a wealth of treatment options, yet still remains lethal in the vast majority of patients. It is becoming increasingly understood that this disease entity continues to evolve over time, acquiring additional and diverse resistance mechanisms with each subsequent therapy used. This dynamic relationship between treatment pressure and disease resistance can be challenging for the managing clinician. The recent discovery of alternate splice variants of the androgen receptor (AR) is one potential mechanism of escape in mCRPC, and recognizing this resistance mechanism might be important for optimal treatment selection for our patients. AR-V7 appears to be the most relevant AR splice variant, and early clinical data suggest that it is a negative prognostic marker in mCRPC. Emerging evidence also suggests that detection of AR-V7 may be associated with resistance to novel hormonal therapy (abiraterone and enzalutamide) but may be compatible with sensitivity to taxane chemotherapy (docetaxel and cabazitaxel). Adding to this complexity is the observation that AR-V7 is a dynamic marker whose status may change across time and depending on selective pressures induced by different therapies. Finally, it is possible that AR-V7 may represent a therapeutic target in mCRPC if drugs can be designed that degrade or inhibit AR splice variants or block their transcriptional activity. Several such agents (including galeterone, EPI-506, and bromodomain/BET inhibitors) are now in clinical development.

PD-1 checkpoint inhibition: Toxicities and management

PURPOSE With the recent approval of 5 PD-1/PD-L1 inhibitors for a number of malignancies, PD-1 axis inhibition is drastically changing the treatment landscape of immunotherapy in cancer. As PD-1/PD-L1 are involved in peripheral immune tolerance, inhibition of this immune checkpoint has led to novel immune-related adverse events including colitis, hepatitis, pneumonitis, rash, and endocrinopathies among many others. MATERIALS AND METHODS In this seminar, we will analyze the incidence of immune-related adverse events for nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab. Then, we will discuss the specific management of the most common immune-mediated adverse events including colitis, hepatitis, pneumonitis, rash, endocrinopathies, nephritis, and neurologic toxicities. RESULTS Immune-related adverse events are frequently treated with immunosuppressive medication such as steroids and mycofenolate mofetil. CONCLUSIONS There are specific immune-related adverse events which are frequently seen by the treating oncologist from checkpoint inhibitors. It is essential to understand the recommended treatment options to minimize toxicity and mortality from this important class of anti-neoplastic therapies.

Exploring the optimal sequence of abiraterone and enzalutamide in patients with chemotherapy-naïve castration-resistant prostate cancer: The Kyoto-Baltimore collaboration

To evaluate and compare the efficacy of sequential treatment with abiraterone followed by enzalutamide or vice versa for castration‐resistant prostate cancer.

Emerging molecularly targeted therapies in castration refractory prostate cancer.

Androgen deprivation therapy (ADT) with medical or surgical castration is the mainstay of therapy in men with metastatic prostate cancer. However, despite initial responses, almost all men eventually develop castration refractory metastatic prostate cancer (CRPC) and die of their disease. Over the last decade, it has been recognized that despite the failure of ADT, most prostate cancers maintain some dependence on androgen and/or androgen receptor (AR) signaling for proliferation. Furthermore, androgen independent molecular pathways have been identified as drivers of continued progression of CRPC. Subsequently, drugs have been developed targeting these pathways, many of which have received regulatory approval. Agents such as abiraterone, enzalutamide, orteronel (TAK-700), and ARN-509 target androgen signaling. Sipuleucel-T, ipilimumab, and tasquinimod augment immune-mediated tumor killing. Agents targeting classic tumorogenesis pathways including vascular endothelial growth factor, hepatocyte growth factor, insulin like growth factor-1, tumor suppressor, and those which regulate apoptosis and cell cycles are currently being developed. This paper aims to focus on emerging molecular pathways underlying progression of CRPC, and the drugs targeting these pathways, which have recently been approved or have reached advanced stages of development in either phase II or phase III clinical trials.

Correlation of genomic alterations assessed by next-generation sequencing (NGS) of tumor tissue DNA and circulating tumor DNA (ctDNA) in metastatic renal cell carcinoma (mRCC): Potential clinical implications

Introduction Tumor tissue and circulating tumor DNA (ctDNA) next-generation sequencing (NGS) testing are frequently performed to detect genomic alterations (GAs) to help guide treatment in metastatic renal cell carcinoma (mRCC), especially after progression on standard systemic therapy. Our objective was to assess if GAs detected by ctDNA NGS are different from those detected by tumor tissue NGS, specifically in patients with mRCC, and if these platforms are interchangeable or complimentary. Results When controlling for genes tested by both platforms, the median mutation rate for ctDNA was similar to tissue (median 3.0 vs. 1.0, p = 0.14). However, the concordance rate between the two platforms was only 8.6%. When comparing GAs by molecular pathway, GAs in tumor tissue were more common for the DNA repair and epigenetic pathways. Materials and Methods Results of NGS testing from tumor tissue and ctDNA from 19 sequential mRCC patients were compared. GAs in each were statistically evaluated using the Wilcoxon signed-rank test. The Fischers exact test was used to compare the incidence of mutations in selected molecular pathways. Conclusions When controlling for genes tested by both platforms, similar number of GAs were detected by both tissue and ctDNA based NGS. However, there was discordance in the type of GAs detected suggesting that ctDNA NGS may be more reflective of dynamic tumor genomic heterogeneity. Hence, these two platforms may be considered complementary to each other, rather than interchangeable, for assessment of tumor GAs to guide selection of targeted clinical trial therapies.

Incidence of Immune-Related Adverse Events with Program Death Receptor-1- and Program Death Receptor-1 Ligand-Directed Therapies in Genitourinary Cancers

Program death receptor-1 (PD-1) and program death receptor-1 ligand (PD-L1) inhibitors are increasingly being used in the clinic to treat a growing number of malignancies, including many genitourinary (GU) malignancies. These immune-based therapies have demonstrated a distinct toxicity profile compared to traditional chemotherapy and the targeted therapies directed at the vascular endothelial growth factor pathway or the mammalian target of rapamycin pathway. Autoimmune toxicity targeting the skin, gastrointestinal tract, or the endocrine organs are some of the more common adverse events (AEs) noted with these therapies. Here in, we report the results of a systematic review of the incidence of toxicities in GU cancers reported in the phase II or phase III clinical trials using single-agent PD-1 or PD-L1 inhibitors. Overall, the rate of serious (grades 3–4) AEs was noted in approximately 15% of patients. The AEs noted were similar between all the agents tested, highlighting the overall class effect of these therapies. The incidence in GU cancers is similar to those seen in other malignancies. Given the widespread and high volume real-world use of these agents, it is important for oncologists to be familiar with these side effects to minimize the risks for patients while undergoing therapy.