Sequential therapy of abiraterone and enzalutamide in castration-resistant prostate cancer: a systematic review and meta-analysis

The impact of locoregional treatments for metastatic castration resistant prostate cancer on disease progression: real life experience from a multicenter cohort

BACKGROUND

Available data on medical treatment of metastatic castration resistant prostate cancer (mCRPC) support the use of more than one therapy line to delay chemotherapy. We evaluate in a longitudinal real life multicenter cohort, the oncological outcome of mCRPC patients treated with Abiraterone Acetate (AA) and Enzalutamide (EZ) in a chemo-naïve setting, who received locoregional treatments for subsequent development of oligorecurrent disease.

METHODS

We prospectively collected data on chemo-naïve mCRPC patients, who received either AA or EZ as first or second line treatment between Oct-2012 and Nov-2020 at 5 centers. High-volume disease at mCRPC onset was defined as bulky positive nodes (≥5 cm) or more than 6 bone metastases. Survival probabilities were computed at 12, 24, 48 and 60 months after treatment start. The impact of loco-regional treatments on progression free survival (PFS) were assessed with the Kaplan-Meier method and the log-rank test was applied.

RESULTS

Overall, 117 chemo-naive mCRPC patients received a first line therapy. Fifty-seven (48.7%) patients received AA and 60 (51.3%) received EZ. Eight (6.7%) patients underwent salvage chemotherapy after first line failure. Overall, 28 patients shifted to a second line therapy. Two-yr progression-free, cancer-specific and overall survival probabilities were 65.5%, 82.2% and 78.4% respectively. Since diagnosis of mCRPC, oligo progression occurred in 25 patients who received stereotactic radiation therapy (23/25, 92%) focused on metastasis (4 nodal sites and 19 bones) or salvage lymph node dissection (2/25, 8%). At Kaplan-Meier analysis, patients with low volume disease displayed higher PFS probabilities (log rank p = 0.009) and in this subgroup of patients loco-regional treatments had a significant impact on PFS (p = 0.048), while it was negligible in the whole cohort and in patients with high volume disease (p = 0.6 and p = 0.75).

CONCLUSIONS

Low-volume mCRPC patients are exposed to improved PFS and seem to benefit from locoregional treatments.

Prostate Cancer: Insights into Disease Progression and Therapeutic Challenges

Prostate cancer (PCa) is the second most common cancer and the fifth highest cause of cancer-related death among men in the world [...].

Real-world outcomes for first line next-generation hormonal agents in metastatic prostate cancer: a systematic review

Aim: This review aims to summarize published evidence on the real-world (RW) outcomes of abiraterone or enzalutamide in first-line metastatic castration-resistant prostate cancer. Materials & methods: Studies reporting on RW effectiveness, safety, economic and/or health-related quality of life outcomes were identified by systematic literature review (2011-2021, incl. Embase®, MEDLINE®) and presented in a qualitative synthesis. Risk of bias was assessed using ROBINS-I or the Molinier checklist. Results: 88 studies (n = 83,427 patients) were included. Median progression-free (40 studies) and overall survival (38 studies) ranged from 3.7 to 20.9 months and 9.8 to 45 months, respectively. Survival, safety and economic outcomes were similar across individual treatments, while limited health-related quality of life evidence suggested improvements with abiraterone. Risk of bias was moderate to high. Conclusion: RW outcomes in first-line metastatic castration-resistant prostate cancer remain poor despite treatment, highlighting an unmet need for new regimens. This review was supported by AstraZeneca and Merck Sharp & Dohme.

A role for androgen receptor variant 7 in sensitivity to therapy: Involvement of IGFBP-2 and FOXA1

Prostate cancer (PCa) is one of the leading causes of cancer-related deaths in men. Localised PCa can be treated effectively, but most patients relapse/progress to more aggressive disease. One possible mechanism underlying this progression is alternative splicing of the androgen receptor, with AR variant 7(ARV7) considered to play a major role. Using viability assays, we confirmed that ARV7-positive PCa cells were less sensitive to treatment with cabazitaxel and an anti-androgen-enzalutamide. Also, using live-holographic imaging, we showed that PCa cells with ARV7 exhibited an increased rate of cell division, proliferation, and motility, which could potentially contribute to a more aggressive phenotype. Furthermore, protein analysis demonstrated that ARV7 knock-down was associated with a decrease in insulin-like growth factor-2 (IGFBP-2) and forkhead box protein A1(FOXA1). This correlation was confirmed in-vivo using PCa tissue samples. Spearman rank correlation analysis showed significant positive associations between ARV7 and IGFBP-2 or FOXA1 in tissue from patients with PCa. This association was not present with the AR. These data suggest an interplay of FOXA1 and IGFBP-2 with ARV7-mediated acquisition of an aggressive prostate cancer phenotype.

[Management of metastatic hormone-sensitive prostate cancer - Current treatment options, criteria for prgoression and switch of therapy]

Based on convincing data with an increase in overall survival (OS), the current national and international European Guidelines (S3, ESMO, EAU) recommend a combination therapy with ADT plus Docetaxel or plus the next-generation antiandrogens abiraterone (plus prednisone/prednisolone), apalutamide or enzalutamide as standard treatment for mHSPC patients with a good performance status (ECOG 0-1). Abiraterone received approval only for use in patients with newly diagnosed (de novo) high-risk mHSPC. There is no restrictive approval status for docetaxel in mHSPC. However, the current S3 guideline differentiates in the level of recommendation with regard to tumour volume: a "strong" recommendation is given in high-volume mHSPC, while only a "may" recommendation is given for low-volume mHSPC due to inconsistent data. Apalutamide and enzalutamide are treatment options in a broad range of mHSPC patients. It can be difficult in clinical practice to determine disease progression under ongoing treatment. Generally, a rising PSA level is the first sign of progression, followed by radiographic and clinical progress. In the hormone-sensitive situation, the decision of when to change treatment can be based on the progression to castration-resistant prostate cancer as defined by the EAU guidelines; in the castration-resistant situation, it can be based on progression as per PCWG3 criteria of the Prostate Cancer Clinical Trials Working Group. At least two of the three criteria (PSA progression, radiographic progression, and clinical deterioration) should be met to determine progression and to change treatment. However, since advanced prostate cancer is a very heterogeneous disease, the decision to change treatment in clinical practice must ultimately be made on a case-by-case basis.

Examining the Effect of PARP-1 Inhibitors on Transcriptional Activity of Androgen Receptor in Prostate Cancer Cells

Since the early 1940s, androgen ablation has been the cornerstone of treatment for prostate cancer (PC). Importantly, androgen receptor (AR) signaling is vital not only for the initiation of PC, which is initially androgen-dependent, but also for castration-resistant disease. Recent studies demonstrated clear promise of the poly(ADP-ribose) polymerase 1 (PARP-1) inhibitors for targeting prostate cancer cells harboring mutations in DNA damage-repair genes. In addition, it has been established that PARP-1 inhibition suppresses growth of AR-positive prostate cancer cells in cell and animal models. Thus, prostate cancer represents a particularly promising disease site for targeting PARP-1, given that both DNA repair and AR-mediated transcription depend on PARP-1 function. Here, we describe the development and use of cell-based assay to evaluate the impact of PARP-1 inhibitors on the AR signaling in prostate cancer cells.

Efficacy of cabazitaxel in fourth or later line of therapy in metastatic castration-resistant prostate cancer: Multi-institutional real-world experience in Germany

OBJECTIVE

Since multiple oncological treatment options in metastatic castration-resistant prostate cancer (mCRPC) are available, optimal sequencing of therapies are under investigation. However, the efficacy of Cabazitaxel (CAB) in fourth and later lines of therapy is rarely investigated.

MATERIAL AND METHODS

Fifty three patients with mCRPC treated with CAB in fourth line or later were included in our retrospective study, which involved eight uro-oncology centers in Germany. Clinical and tumor characteristics, as well as PSA-response rates were analyzed. Kaplan-Meier plots addressed overall survival (OS) and progression-free survival (PFS). Logistic regression models predicted risk factors of overall mortality (OM).

RESULTS

Of 53 patients, 79% (n=42), 19% (n=10) and 2% (n=1) received CAB in fourth, fifth and sixth line. A median of 4 cycles of CAB were administered. Median PSA at start of CAB was 199ng/ml (interquartile range (IQR) 70-869). In total, 89% had bone and 40% visceral metastases prior to the start of CAB. Moreover, 30% of patients received Docetaxel in first line therapy for mCRPC. Most frequent sequence of therapy was abiraterone followed by docetaxel and followed by enzalutamide. Overall, median PSA-response rate was -20% (IQR -80 to +10%). Patients with docetaxel in first line had a significantly better median PSA-response on CAB (-80 vs. 20%, P=0.03). Median OS, radiographic PFS and overall PFS were 14.8 (Confidence interval (CI): 11.0-20.8), 3.0 (CI: 2.9-4.0) and 2.9 (CI: 2.0-3.3) months, respectively. In multivariable analyses, visceral metastases, PSA >100ng/ml, ISUP4+5 and later administration of Docetaxel were predictors of OM.

CONCLUSION

Real-world experiences indicate that favorable oncologic outcomes can be achieved with CAB especially regarding PSA-response and OS even in the fourth line or later in patients with mCRPC.

Functional roles of E3 ubiquitin ligases in prostate cancer

Prostate cancer (PCa) is a malignant epithelial tumor of the prostate gland with a high male cancer incidence. Numerous studies indicate that abnormal function of ubiquitin-proteasome system (UPS) is associated with the progression and metastasis of PCa. E3 ubiquitin ligases, key components of UPS, determine the specificity of substrates, and substantial advances of E3 ubiquitin ligases have been reached recently. Herein, we introduce the structures and functions of E3 ubiquitin ligases and summarize the mechanisms of E3 ubiquitin ligases-related PCa signaling pathways. In addition, some progresses in the development of inhibitors targeting E3 ubiquitin ligases are also included.

A Phase Ib/II Study of Sabizabulin, a Novel Oral Cytoskeleton Disruptor, in Men with Metastatic Castration-resistant Prostate Cancer with Progression on an Androgen Receptor-targeting Agent

PURPOSE

Sabizabulin, an oral cytoskeleton disruptor, was tested in a phase Ib/II clinical study in men with metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

The phase Ib portion utilized a 3+3 design with escalating daily oral doses of 4.5-81 mg and increasing schedule in 39 patients with mCRPC treated with one or more androgen receptor-targeting agents. Prior taxane chemotherapy was allowed. The phase II portion tested a daily dose of 63 mg in 41 patients with no prior chemotherapy. Efficacy was assessed using PCWG3 and RECIST 1.1 criteria.

RESULTS

The MTD was not defined in the phase Ib and the recommended phase II dose was set at 63 mg/day. The most common adverse events (>10% frequency) at the 63 mg oral daily dosing (combined phase Ib/II data) were predominantly grade 1-2 events. Grade ≥3 events included diarrhea (7.4%), fatigue (5.6%), and alanine aminotransferase/aspartate aminotransferase elevations (5.6% and 3.7%, respectively). Neurotoxicity and neutropenia were not observed. Preliminary efficacy data in patients treated with ≥1 continuous cycle of 63 mg or higher included objective response rate in 6 of 29 (20.7%) patients with measurable disease (1 complete, 5 partial) and 14 of 48 (29.2%) patients had PSA declines. The Kaplan-Meier median radiographic progression-free survival was estimated to be 11.4 months (n = 55). Durable responses lasting >2.75 years were observed.

CONCLUSIONS

This clinical trial demonstrated that chronic oral daily dosing of sabizabulin has a favorable safety profile with preliminary antitumor activity. These data support the ongoing phase III VERACITY trial of sabizabulin in men with mCRPC.

Real-world patient characteristics associated with survival of 2 years or more after radium-223 treatment for metastatic castration-resistant prostate cancer (EPIX study)

Background

The real-world EPIX study was conducted to gather information about the characteristics of patients with metastatic castration-resistant prostate cancer (mCRPC) who survived ≥2 years after treatment with the alpha-emitter radium-223.

Methods

This retrospective study of electronic health records in the US Flatiron database (NCT04516161) included patients with mCRPC treated with radium-223 between January 2013 and June 2019. Median overall survival (OS) and prostate-specific antigen (PSA) response (≥50% reduction) from start of radium-223 treatment were the primary and secondary endpoints, respectively. Patient characteristics were compared between those who survived ≥2 years versus <2 years, including a subgroup who survived <6 months.

Results

In the 1180 patients identified, median OS was 12.9 months (95% CI: 12.1–13.7), and 13% of patients with data at 6 months had a PSA response. The survival groups included 775 patients (65.7%) who survived <2 years (including 264 (22.4%) who survived <6 months) and 185 patients (15.7%) who survived ≥2 years; 220 patients (18.6%) had incomplete follow-up data and were censored. On multivariate analysis, age >75 years, Eastern Cooperative Oncology Group performance status (ECOG PS) 2–4, visceral metastases, prior symptomatic skeletal events (SSEs), and prior chemotherapy were independently prognostic of reduced OS. For patients with survival ≥2 years versus <2 years, median age was 71 versus 75 years, 4% versus 14% had ECOG PS 2–4, 4% versus 10% had visceral metastases, 38% versus 44% had prior SSEs, and 16% versus 32% had prior chemotherapy.

Conclusions

In this study of men with mCRPC treated in real-world clinical practice, median OS was consistent with that seen in the phase 3 ALSYMPCA trial. Patients who survived ≥2 years after the start of radium-223 were younger and had better ECOG PS, lower disease burden, and less use of prior chemotherapy than those who survived <2 years.

The Impact of Palliative Transurethral Resection of the Prostate on the Prognosis of Patients With Bladder Outlet Obstruction and Metastatic Prostate Cancer: A Population-Matched Study

Objective: This study aimed to evaluate the survival outcomes of patients with bladder outlet obstruction (BOO) and metastatic prostate cancer (mPCa) after having a palliative transurethral resection of the prostate (pTURP) surgery. Methods: We identified patients with mPCa between 2004 and 2016 in the Surveillance, Epidemiology, and End Results (SEER) database. Patients who received pTURP and non-surgical therapy were identified. A propensity-score matching was introduced to balance the covariate. Kaplan-Meier analysis and COX regression were conducted to evaluate the overall survival (OS) and cancer-specific survival (CSS) outcomes. Results: A total of 36,003 patients were identified; 2,823 of them were in the pTURP group and 33,180 were in the non-surgical group. The survival curves of the overall cohort showed that the pTURP group was associated with worse outcomes in both OS (HR: 1.12, 95% CI: 1.07-1.18, p < 0.001) and CSS (HR: 1.08, 95% CI: 1.02-1.15, p = 0.004) compared with the non-surgical group. The mean survival time in the overall cohort of the pTURP group was shorter than the non-surgical group in both OS [35.13 ± 1.53 vs. 40.44 ± 0.59 months] and CSS [48.8 ± 1.27 vs. 55.92 ± 0.43 months]. In the matched cohort, the pTURP group had significantly lower survival curves for both OS (HR: 1.25, 95% CI: 1.16-1.35, p < 0.001) and CSS (HR: 1.23, 95% CI: 1.12-1.35, p < 0.001) than the non-surgical group. pTURP significantly reduced the survival months of the patients (36.49 ± 0.94 vs. 45.52 ± 1.23 months in OS and 50.1 ± 1.49 vs. 61.28 ± 1.74 months in CSS). In the multivariate COX analysis, pTURP increased the risk of overall mortality (HR: 1.19, 95% CI: 1.09-1.31, p < 0.001) and cancer-specific mortality CSS (HR: 1.23, 95% CI: 1.14-1.33, p < 0.001) compared with the non-surgical group. Conclusions: For mPCa patients with BOO, pTURP could reduce OS and CSS while relieving the obstruction.

Real-world outcomes of second novel hormonal therapy or radium-223 following first novel hormonal therapy for mCRPC

Aim: To evaluate real-world clinical outcomes of radium-223 or alternative novel hormonal therapy (NHT) following first-line NHT for metastatic castration-resistant prostate cancer (mCRPC). Patients & methods: Retrospective analysis of the US Flatiron database (ClinicalTrials.gov identifier: NCT03896984). Results: In the radium-223 cohort (n = 120) versus the alternative NHT cohort (n = 226), proportionally more patients had prior symptomatic skeletal events and bone-only metastases, and first-line NHT duration was shorter. Following second-line therapy, 49 versus 39% of patients received subsequent life-prolonging therapy; of these, 47 versus 76% received taxane. Median overall survival was 10.8 versus 11.2 months. Conclusion: Real-world patients with mCRPC had similar median overall survival following second-line radium-223 or alternative NHT after first-line NHT. Many patients received subsequent therapy, with less taxane use after radium-223.

Inhibition of Scavenger Receptor Class B Type 1 (SR-B1) Expression and Activity as a Potential Novel Target to Disrupt Cholesterol Availability in Castration-Resistant Prostate Cancer

There have been several studies that have linked elevated scavenger receptor class b type 1 (SR-B1) expression and activity to the development and progression of castration-resistant prostate cancer (CRPC). SR-B1 facilitates the influx of cholesterol to the cell from lipoproteins in systemic circulation. This influx of cholesterol may be important for many cellular functions, including the synthesis of androgens. Castration-resistant prostate cancer tumors can synthesize androgens de novo to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-B1 may impact the ability of prostate cancer cells, particularly those of the castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. SR-B1 expression is elevated in CRPC models and has been linked to poor survival of patients. The overarching belief has been that cholesterol modulation, through either synthesis or uptake inhibition, will impact essential signaling processes, impeding the proliferation of prostate cancer. The reduction in cellular cholesterol availability can impede prostate cancer proliferation through both decreased steroid synthesis and steroid-independent mechanisms, providing a potential therapeutic target for the treatment of prostate cancer. In this article, we discuss and highlight the work on SR-B1 as a potential novel drug target for CRPC management.

Androgen receptor axis-targeted agents for non-metastatic castration-resistant prostate cancer impact on overall survival and safety profile: an updated systematic review and meta-analysis

INTRODUCTION

The management of non-metastatic castration-resistant prostate cancer (nmCRPC) has undergone a paradigm shift with the development of androgen receptor axis-targeted (ARAT) agents. The updated results with final overall survival (OS) data of the phase III PROSPER, SPARTAN, and ARAMIS trials have recently been reported. Therefore, we performed an updated meta-analysis and network meta-analysis to indirectly compare the efficacy and safety of currently available treatments.

EVIDENCE ACQUISITION

Multiple databases were searched for articles published before January 2021. Studies that compared OS and adverse events (AEs) in patients with nmCRPC were considered eligible.

EVIDENCE SYNTHESIS

Three studies (n=4,117) met our eligibility criteria. Formal network meta-analyses were conducted. ARAT agent is associated with significantly longer OS compared to placebo (pooled hazard ratio (HR): 0.74, 95% confidence interval (CI): 0.65-0.83, P<0.001), with similar results shown for patients with both N1 and N0 disease (pooled HR 0.61 and pooled HR 0.76, respectively). In the network meta-analysis, apalutamide, darolutamide, and enzalutamide were more effective than placebo, with similar efficacies in terms of OS. For AEs (including any AEs, grade 3 or grade 4 AEs, grade 5 AEs, serious AEs, and AEs leading to treatment discontinuation), darolutamide was shown to be likely well tolerated. Quality-of-life was preserved in treatment arms irrespective of the drug.

CONCLUSIONS

All three ARAT agents are efficacious options for the treatment of nmCRPC, whereas darolutamide appears to have the most favorable tolerability profile. These findings may facilitate individualized treatment strategies and inform future direct comparative trials.

Prognostic significance of third-line treatment for patients with metastatic castration-resistant prostate cancer: comparative assessments between cabazitaxel and other agents

BACKGROUND

Cabazitaxel has played an important role in the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC); however, several types of sequential therapy against mCRPC have been performed in routine clinical practice. The objective of this study was to investigate the impact of third-line treatment on prognostic outcomes of mCRPC patients.

METHODS

This study retrospectively analyzed the clinical outcomes of 166 patients who received 3 agents following the diagnosis of mCRPC, consisting of 81 sequentially treated with either abiraterone or enzalutamide and then docetaxel, followed by third-line cabazitaxel (group A) and 85 treated with 3 agents, including abiraterone, enzalutamide, and docetaxel (group B).

RESULTS

There were no significant differences in major characteristics at the introduction of the third-line agent between these 2 groups. The proportion of patients with prostate-specific antigen (PSA) reduction > 50% by cabazitaxel in group A was significantly greater than that by either third-line agent in group B. Both PSA progression-free survival (PFS) and overall survival (OS) following third-line therapy in group A were significantly longer than those in group B. Furthermore, OS after the diagnosis of mCRPC in group A was significantly longer than that in group B. Multivariate analysis identified independent predictors of favorable prognostic outcomes after third-line therapy as follows: high-performance status (PS), low PSA level and third-line cabazitaxel for PSA PFS, and high PS, low lactate dehydrogenase level and third-line cabazitaxel for OS.

CONCLUSIONS

The introduction of cabazitaxel as a third-line agent could markedly improve the prognostic outcomes of mCRPC patients.

Phase II Multicenter Study of Enzalutamide in Metastatic Castration-Resistant Prostate Cancer to Identify Mechanisms Driving Resistance

PURPOSE

Enzalutamide is a second-generation androgen receptor (AR) inhibitor that has improved overall survival (OS) in metastatic castration-resistant prostate cancer (CRPC). However, nearly all patients develop resistance. We designed a phase II multicenter study of enzalutamide in metastatic CRPC incorporating tissue and blood biomarkers to dissect mechanisms driving resistance.

PATIENTS AND METHODS

Eligible patients with metastatic CRPC underwent a baseline metastasis biopsy and then initiated enzalutamide 160 mg daily. A repeat metastasis biopsy was obtained at radiographic progression from the same site when possible. Blood for circulating tumor cell (CTC) analysis was collected at baseline and progression. The primary objective was to analyze mechanisms of resistance in serial biopsies. Whole-exome sequencing was performed on tissue biopsies. CTC samples underwent RNA sequencing.

RESULTS

A total of 65 patients initiated treatment, of whom 22 (33.8%) had received prior abiraterone. Baseline biopsies were enriched for alterations in AR (mutations, amplifications) and tumor suppression genes (PTEN, RB1, and TP53), which were observed in 73.1% and 92.3% of baseline biopsies, respectively. Progression biopsies revealed increased AR amplifications (64.7% at progression vs. 53.9% at baseline) and BRCA2 alterations (64.7% at progression vs. 38.5% at baseline). Genomic analysis of baseline and progression CTC samples demonstrated increased AR splice variants, AR-regulated genes, and neuroendocrine markers at progression.

CONCLUSIONS

Our results demonstrate that a large proportion of enzalutamide-treated patients have baseline and progression alterations in the AR pathway and tumor suppressor genes. We demonstrate an increased number of BRCA2 alterations post-enzalutamide, highlighting the importance of serial tumor sampling in CRPC.

Dissecting the Hormonal Signaling Landscape in Castration-Resistant Prostate Cancer

Understanding the molecular mechanisms underlying prostate cancer (PCa) progression towards its most aggressive, castration-resistant (CRPC) stage is urgently needed to improve the therapeutic options for this almost incurable pathology. Interestingly, CRPC is known to be characterized by a peculiar hormonal landscape. It is now well established that the androgen/androgen receptor (AR) axis is still active in CRPC cells. The persistent activity of this axis in PCa progression has been shown to be related to different mechanisms, such as intratumoral androgen synthesis, AR amplification and mutations, AR mRNA alternative splicing, increased expression/activity of AR-related transcription factors and coregulators. The hypothalamic gonadotropin-releasing hormone (GnRH), by binding to its specific receptors (GnRH-Rs) at the pituitary level, plays a pivotal role in the regulation of the reproductive functions. GnRH and GnRH-R are also expressed in different types of tumors, including PCa. Specifically, it has been demonstrated that, in CRPC cells, the activation of GnRH-Rs is associated with a significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic activity. This antitumor activity is mainly mediated by the GnRH-R-associated Gαi/cAMP signaling pathway. In this review, we dissect the molecular mechanisms underlying the role of the androgen/AR and GnRH/GnRH-R axes in CRPC progression and the possible therapeutic implications.

Early Prostate-Specific Antigen (PSA) Change at Four Weeks of the First-Line Treatment Using Abiraterone and Enzalutamide Could Predict Early/Primary Resistance in Metastatic Castration-Resistant Prostate Cancer

Simple Summary

Serum prostate-specific antigen (PSA) level is the most valuable biomarker in prostate cancer. This study investigates the predictive value of achieving >30% PSA decline at four weeks of first-line androgen signaling inhibitors (ASIs) using a multi-institutional cohort dataset of 254 mCRPC patients. The achievement of >30% PSA decline at four weeks is an independent predictor for overall survival (OS). Interestingly, in patients who did not achieve >30% PSA decline at four weeks—an achievement of the >30% PSA decline at 12 weeks is eventually observed in 30.9% of those patients. To identify the variables that discriminate the patient survival in 97 patients without achieving >30% PSA decline at four weeks of the first-line treatment, a multivariate analysis is conducted. The duration of androgen deprivation therapy before CRPC < 12 months and Eastern Cooperative Oncology Group Performance Status ≥ 1 are identified as independent predictors for shorter OS for those patients.

Abstract

The identification of early or primary resistance to androgen signaling inhibitors (ASIs) is of great value for the treatment of metastatic castration-resistant prostate cancer (mCRPC). This study evaluates the predictive value of prostate-specific antigen (PSA) response at dour weeks of first-line ASIs treatment for mCRPC patients. A total of 254 patients treated with ASIs (abiraterone acetate: AA and enzalutamide: Enz) at the first-line treatment are retrospectively analyzed. Patients are stratified according to the achievement of >30% PSA decline at 4 and 12 weeks from the treatment initiation. At four weeks of the treatment, 157 patients (61.8%) achieved >30% PSA decline from the baseline. Thereafter, 177 patients (69.7%) achieved >30% PSA decline at 12 weeks of the treatment. A multivariate analysis exhibits >30% PSA decline at four weeks as an independent predictor for overall survival (OS). We note that 30 of 97 (30.9%) patients who did not achieve >30% PSA decline at four weeks consequently achieved >30% PSA decline at 12 weeks, and had a comparable favorable three years OS rate as the 147 patients achieving >30% PSA decline at both 4 and 12 weeks. To identify the variables that discriminate the patient survival in 97 patients without achieving >30% PSA decline at four weeks, a multivariate analysis is performed. The duration of androgen deprivation therapy before CRPC ≤ 12 months and Eastern Cooperative Oncology Group Performance Status ≥ 1 are identified as independent predictors for shorter OS for those patients. These data offer a concept of early treatment switch after four weeks of first-line ASIs when not observing >30% PSA decline at four weeks—particularly in patients with a modest effect of ADT and poor performance status.

A Phase Ib/IIa Study of the Pan-BET Inhibitor ZEN-3694 in Combination with Enzalutamide in Patients with Metastatic Castration-resistant Prostate Cancer

PURPOSE

ZEN-3694 is a bromodomain extraterminal inhibitor (BETi) with activity in androgen-signaling inhibitor (ASI)-resistant models. The safety and efficacy of ZEN-3694 plus enzalutamide was evaluated in a phase Ib/IIa study in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients had progressive mCRPC with prior resistance to abiraterone and/or enzalutamide. 3+3 dose escalation was followed by dose expansion in parallel cohorts (ZEN-3694 at 48 and 96 mg orally once daily, respectively).

RESULTS

Seventy-five patients were enrolled (N = 26 and 14 in dose expansion at low- and high-dose ZEN-3694, respectively). Thirty (40.0%) patients were resistant to abiraterone, 34 (45.3%) to enzalutamide, and 11 (14.7%) to both. ZEN-3694 dosing ranged from 36 to 144 mg daily without reaching an MTD. Fourteen patients (18.7%) experienced grade ≥3 toxicities, including three patients with grade 3 thrombocytopenia (4%). An exposure-dependent decrease in whole-blood RNA expression of BETi targets was observed (up to fourfold mean difference at 4 hours post-ZEN-3694 dose; P ≤ 0.0001). The median radiographic progression-free survival (rPFS) was 9.0 months [95% confidence interval (CI), 4.6-12.9] and composite median radiographic or clinical progression-free survival (PFS) was 5.5 months (95% CI, 4.0-7.8). Median duration of treatment was 3.5 months (range, 0-34.7+). Lower androgen receptor (AR) transcriptional activity in baseline tumor biopsies was associated with longer rPFS (median rPFS 10.4 vs. 4.3 months).

CONCLUSIONS

ZEN-3694 plus enzalutamide demonstrated acceptable tolerability and potential efficacy in patients with ASI-resistant mCRPC. Further prospective study is warranted including in mCRPC harboring low AR transcriptional activity.

Risk stratification for the prediction of overall survival could assist treatment decision-making at diagnosis of castration-resistant prostate cancer: a multicentre collaborative study in Japan

OBJECTIVES

To assess whether a new risk stratification system according to predictors for overall survival (OS) at the diagnosis of metastatic castration-resistant prostate cancer (mCRPC) could determine treatment outcomes and assist in treatment decision-making.

PATIENTS AND METHODS

Two independent clinical cohorts of patients, treated with androgen signalling inhibitors (ASIs: abiraterone and enzalutamide) or docetaxel as a first-line treatment for mCRPC, were used in this study: a derivation cohort (196 patients with mCRPC) and an external validation cohort (211 patients with mCRPC).

RESULTS

Three independent predictors for OS, including duration of initial androgen deprivation therapy <12 months before mCRPC diagnosis, alkaline phosphatase level >350 U/dL and haemoglobin level <11 g/dL at the diagnosis of mCRPC, were defined as risk factors. Patients with zero, one and multiple risk factors were assigned to a favourable-, intermediate- and poor-risk group, respectively. The median OS values in each risk group were well separated in the derivation cohort (P < 0.001) as well as in the validation cohort (P < 0.001). Of a total of 407 patients with mCRPC, 84 were assigned to the poor-risk group with the median OS of 12 months. In this group, a trend towards longer OS favouring docetaxel compared to ASIs as the first-line treatment (medians of 17 and 12 months, respectively) was observed.

CONCLUSION

The new risk group stratification system could predict patient survival at the diagnosis of mCRPC. Given the convenience of these risk definitions, physicians may be encouraged to consider these risk groups in daily practice.

Preclinical studies of a novel snake venom-derived recombinant disintegrin with antitumor activity: A review

Snake venoms consist of a complex mixture of many bioactive molecules. Among them are disintegrins, which are peptides without enzymatic activity, but with high binding affinity for integrins, transmembrane receptors that function to connect cells with components of the extracellular matrix. Integrin-mediated cell attachment is critical for cell migration and dissemination, as well as for signal transduction pathways involved in cell growth. During tumor development, integrins play key roles by supporting cancer cell proliferation, angiogenesis, and metastasis. The recognition that snake venom disintegrins can block integrin functions has spawned a number of studies to explore their cancer therapeutic potential. While dozens of different disintegrins have been isolated, none of them as yet has undergone clinical evaluation in cancer patients. Among the best-characterized and preclinically most advanced disintegrins is vicrostatin (VCN), a recombinant disintegrin that was rationally designed by fusing 62 N-terminal amino acids derived from the disintegrin contortrostatin with 6 C-terminal amino acids from echistatin, the disintegrins from another snake species. Bacterially produced VCN was shown to target multiple tumor-associated integrins, achieving potent anti-tumor and anti-angiogenic effects in in vitro and in vivo models in the absence of noticeable toxicity. This review will introduce the field of snake venom disintegrins as potential anticancer agents and illustrate the translational development and cancer-therapeutic potential of VCN as an example.