Antitumour activity of docetaxel following treatment with the CYP17A1 inhibitor abiraterone: clinical evidence for cross-resistance?

Evaluation of Second-Line Treatment for Castration-Resistant Prostate Cancer following the Administration of Upfront Androgen Receptor Signaling Inhibitors

This study evaluated the effects of docetaxel and androgen receptor signaling inhibitors as second-line treatments in patients with castration-resistant prostate cancer after androgen receptor signaling inhibitors as first-line treatment. This study retrospectively evaluated the clinical outcomes of second-line treatment with docetaxel or androgen receptor signaling inhibitor in patients with castration-resistant prostate cancer who received first-line treatment with androgen receptor signaling inhibitors. Clinical backgrounds and outcomes were compared between docetaxel and androgen receptor signaling inhibitors as second-line treatment. Of 59 patients, 21 (35.6%) and 38 (64.4%) received docetaxel and androgen receptor signaling inhibitors as second-line treatment after first-line treatment with androgen receptor signaling inhibitors, respectively. In the second-line setting, the median progression-free survival was longer with androgen receptor signaling inhibitor than with docetaxel (17 versus 6 months, P=0.014). In the first-line setting, the median progression-free survival was longer with androgen receptor signaling inhibitors than with docetaxel (32 versus 25 months, P=0.014); however, no significant difference was found in the overall survival. Multivariate analysis revealed that there was no significant association between second-line treatment and survival, and first-line treatment with abiraterone was identified as a prognostic factor for progression-free survival. Subgroup analysis showed that the abiraterone-enzalutamide sequence was more effective than the other three sequences for progression-free survival and overall survival. This study suggests that second-line treatment with an androgen receptor signaling inhibitor for castration-resistant prostate cancer after androgen receptor signaling inhibitors as first-line treatment may be more beneficial, particularly with abiraterone as the upfront treatment.

Second-line treatment options in metastatic castration-resistant prostate cancer after progression on first-line androgen-receptor targeting therapies: A systematic review and Bayesian network analysis

OBJECTIVE

To summarize and indirectly compare the efficacy and safety of different second-line systematic therapies after first-line androgen-receptor targeting therapies (ARTs) for biomarker-unselected metastatic castration-resistant prostate cancer (mCRPC) patients.

METHODS

Studies published in English up to May 2023 were identified in PubMed, Web of Science and ASCO-GU 2023. Studies accessing the efficacy and safety of second-line systematic therapies after first-line ARTs for biomarker-unselected mCRPC patients were eligible for current systematic review and network meta-analysis (NMA).

RESULTS

Thirty-two studies with 5388 patients and 10 unique treatment modalities met our inclusion criteria. Current evidence suggested that docetaxel (DOC) combined with the same ART as first-line (ART1) (ART1 + DOC) were associated with significantly improved PSA response, PSA progression-free survival (PFS) and clinical or radiographic PFS (rPFS) compared with other reported second-line systematic therapies, including DOC. An increase in toxicity was observed with ART1 + DOC. Our NMA indicated that DOC monotherapy was only inferior to ART1 + DOC in improvement disease outcomes. The incidence of toxicity between patients received second-line DOC and an alternative ART (ART2) was similar.

CONCLUSION

The available evidence reviewed in our work suggested a clinical benefit of DOC nomotherapy and DOC plus ART1 as the second-line systematic therapy for biomarker-unselected mCRPC patients progressed on a first-line ART. More studies and RCTs are needed to evaluate the optimal second-line treatments for mCRPC patients with one prior first-line ART.

Significant reduction in burden of metastatic disease by intermittent docetaxel therapy in a patient with castration-resistant prostate cancer

Intermittent docetaxel therapy (IDT) is rarely used nowadays as a treatment option for men with metastatic castration-resistant prostate cancer (mCRPC) because of the widespread availability of androgen receptor axis-targeted therapy, which is less toxic. Therefore, there is limited information available on whether IDT has a clinical benefit in the treatment of men with mCRPC. This report describes the case of a 66-year-old man with a diagnosis of cT2N1M0 prostate cancer who underwent neoadjuvant combined androgen blockade and whole-pelvis radiation therapy. However, the tumor had progressed to mCRPC with metastasis to the bladder and a left pelvic lymph node within 2 years. Docetaxel had been administered as first-line chemotherapy, and the patient achieved a complete response in terms of the bladder metastasis. Docetaxel was stopped after 15 cycles. When a durable response had been maintained for more than 2 years, during which only androgen deprivation therapy was administered, the patient was switched to observation only. However, his prostate-specific antigen level gradually increased. Abiraterone was started as second-line therapy, during which there was a rapid increase in the PSA level. Computed tomography revealed further enlargement of the left pelvic lymph node, bladder metastasis, metastasis to the left common iliac lymph nodes, and several disseminated nodules around the bladder. Docetaxel was reintroduced as IDT for third-line therapy, and a complete response was achieved for all metastases, with the exception of the metastasis in the left pelvic lymph node. Thus far, the patient has survived for more than 7 years after starting docetaxel as first-line therapy for mCRPC. IDT is potentially useful in a subgroup of patients with mCRPC and could achieve long-term survival. Comprehensive genomic profiling may help physicians to select patients with mCRPC who are more likely to benefit from docetaxel than other systemic therapy.

A Phase 1/2 multicenter trial of DKN-01 as monotherapy or in combination with docetaxel for the treatment of metastatic castration-resistant prostate cancer (mCRPC)

BACKGROUND

Dickkopf-related protein 1 (DKK1) is a Wingless-related integrate site (Wnt) signaling modulator that is upregulated in prostate cancers (PCa) with low androgen receptor expression. DKN-01, an IgG4 that neutralizes DKK1, delays PCa growth in pre-clinical DKK1-expressing models. These data provided the rationale for a clinical trial testing DKN-01 in patients with metastatic castration-resistant PCa (mCRPC).

METHODS

This was an investigator-initiated parallel-arm phase 1/2 clinical trial testing DKN-01 alone (monotherapy) or in combination with docetaxel 75 mg/m2 (combination) for men with mCRPC who progressed on ≥1 AR signaling inhibitors. DKK1 status was determined by RNA in-situ expression. The primary endpoint of the phase 1 dose escalation cohorts was the determination of the recommended phase 2 dose (RP2D). The primary endpoint of the phase 2 expansion cohorts was objective response rate by iRECIST criteria in patients treated with the combination.

RESULTS

18 pts were enrolled into the study-10 patients in the monotherapy cohorts and 8 patients in the combination cohorts. No DLTs were observed and DKN-01 600 mg was determined as the RP2D. A best overall response of stable disease occurred in two out of seven (29%) evaluable patients in the monotherapy cohort. In the combination cohort, five out of seven (71%) evaluable patients had a partial response (PR). A median rPFS of 5.7 months was observed in the combination cohort. In the combination cohort, the median tumoral DKK1 expression H-score was 0.75 and the rPFS observed was similar between patients with DKK1 H-score ≥1 versus H-score = 0.

CONCLUSION

DKN-01 600 mg was well tolerated. DKK1 blockade has modest anti-tumor activity as a monotherapy for mCRPC. Anti-tumor activity was observed in the combination cohorts, but the response duration was limited. DKK1 expression in the majority of mCRPC is low and did not clearly correlate with anti-tumor activity of DKN-01 plus docetaxel.

Impact of DNA damage repair alterations on prostate cancer progression and metastasis

Prostate cancer is among the most common diseases worldwide. Despite recent progress with treatments, patients with advanced prostate cancer have poor outcomes and there is a high unmet need in this population. Understanding molecular determinants underlying prostate cancer and the aggressive phenotype of disease can help with design of better clinical trials and improve treatments for these patients. One of the pathways often altered in advanced prostate cancer is DNA damage response (DDR), including alterations in BRCA1/2 and other homologous recombination repair (HRR) genes. Alterations in the DDR pathway are particularly prevalent in metastatic prostate cancer. In this review, we summarise the prevalence of DDR alterations in primary and advanced prostate cancer and discuss the impact of alterations in the DDR pathway on aggressive disease phenotype, prognosis and the association of germline pathogenic alterations in DDR genes with risk of developing prostate cancer.

Radium-223 for patients with metastatic castration-resistant prostate cancer with asymptomatic bone metastases progressing on first-line abiraterone acetate or enzalutamide: A single-arm phase II trial

PURPOSE

The paper aims to evaluate the efficacy and safety of ²²³Ra in patients who progressed after first-line androgen deprivation therapy.

PATIENTS AND METHODS

EXCAAPE (NCT03002220) was a multicentre, single-arm, open-label, non-controlled phase IIa trial in 52 patients with metastatic castration-resistant prostate cancer and asymptomatic bone metastases who have progressed on abiraterone acetate or enzalutamide, up to six doses of ²²³Ra (55 kBq/kg of body weight per month). The primary end-point was radiographic progression-free survival (rPFS). Secondary end-points included rPFS based on androgen receptor splice variant 7 (AR-V7) expression in circulating tumour cells (CTCs), overall survival, and safety.

RESULTS

Median rPFS was 5.5 months (95% CI 5.3-5.5). Median rPFS of patients with AR-V7(-) CTCs was longer than that of patients with AR-V7(+) CTCs (5.5 versus 2.2 months, respectively; P = 0.056). Median overall survival was 14.8 months (95% CI 11.2-not reached) and was significantly greater for AR-V7(-) patients than for AR-V7(+) patients (14.8 months versus 3.5 months, respectively; P < 0.01). ²²³Ra was well tolerated; anaemia and thrombocytopenia were the most common grade 3/4 adverse events (5.8% and 11.5%, respectively).

CONCLUSIONS

²²³Ra seems to be a reasonable treatment for patients with metastatic castration-resistant prostate cancer and asymptomatic bone metastases progressing on novel hormonal therapy and had an acceptable safety profile.

Pembrolizumab Plus Docetaxel and Prednisone in Patients with Metastatic Castration-resistant Prostate Cancer: Long-term Results from the Phase 1b/2 KEYNOTE-365 Cohort B Study

BACKGROUND

Patients with metastatic castration-resistant prostate cancer (mCRPC) frequently receive docetaxel after they develop resistance to abiraterone or enzalutamide and need more efficacious treatments.

OBJECTIVE

To evaluate the efficacy and safety of pembrolizumab plus docetaxel and prednisone in patients with mCRPC.

DESIGN, SETTING, AND PARTICIPANTS

The trial included patients with mCRPC in the phase 1b/2 KEYNOTE-365 cohort B study who were chemotherapy naïve and who experienced failure of or were intolerant to ≥4 wk of abiraterone or enzalutamide for mCRPC with progressive disease within 6 mo of screening.

INTERVENTION

Pembrolizumab 200 mg intravenously (IV) every 3 wk (Q3W), docetaxel 75 mg/m² IV Q3W, and prednisone 5 mg orally twice daily.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoints were safety, the prostate-specific antigen (PSA) response rate, and the objective response rate (ORR) according to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) by blinded independent central review (BICR). Secondary endpoints included time to PSA progression; the disease control rate (DCR) and duration of response (DOR) according to RECIST v1.1 by BICR; ORR, DCR, DOR, and radiographic progression-free survival (rPFS) according to Prostate Cancer Working Group 3-modified RECIST v1.1 by BICR; and overall survival (OS).

RESULTS AND LIMITATIONS

Among 104 treated patients, 52 had measurable disease. The median time from allocation to data cutoff (July 9, 2020) was 32.4 mo, during which 101 patients discontinued treatment, 81 (78%) for disease progression. The confirmed PSA response rate was 34% and the confirmed ORR (RECIST v1.1) was 23%. Median rPFS and OS were 8.5 mo and 20.2 mo, respectively. Treatment-related adverse events (TRAEs) occurred in 100 patients (96%). Grade 3-5 TRAEs occurred in 46 patients (44%). Seven AE-related deaths (6.7%) occurred (2 due to treatment-related pneumonitis). Limitations of the study include the single-arm design and small sample size.

CONCLUSIONS

Pembrolizumab plus docetaxel and prednisone demonstrated antitumor activity in chemotherapy-naïve patients with mCRPC treated with abiraterone or enzalutamide for mCRPC. Safety was consistent with profiles for the individual agents. Further investigation is warranted.

PATIENT SUMMARY

We evaluated the efficacy and safety of the anti-PD-1 antibody pembrolizumab combined with the chemotherapy drug docetaxel and the steroid prednisone for patients with metastatic prostate cancer resistant to androgen deprivation therapy , and who never received chemotherapy. The combination showed antitumor activity and manageable safety in this patient population. This trial is registered on ClinicalTrials.gov as NCT02861573.

Cross-Resistance Among Sequential Cancer Therapeutics: An Emerging Issue

Over the past two decades, cancer treatment has benefited from having a significant increase in the number of targeted drugs approved by the United States Food and Drug Administration. With the introduction of targeted therapy, a great shift towards a new era has taken place that is characterized by reduced cytotoxicity and improved clinical outcomes compared to traditional chemotherapeutic drugs. At present, targeted therapies and other systemic anti-cancer therapies available (immunotherapy, cytotoxic, endocrine therapies and others) are used alone or in combination in different settings (neoadjuvant, adjuvant, and metastatic). As a result, it is not uncommon for patients affected by an advanced malignancy to receive subsequent anti-cancer therapies. In this challenging complexity of cancer treatment, the clinical pathways of real-life patients are often not as direct as predicted by standard guidelines and clinical trials, and cross-resistance among sequential anti-cancer therapies represents an emerging issue. In this review, we summarize the main cross-resistance events described in the diverse tumor types and provide insight into the molecular mechanisms involved in this process. We also discuss the current challenges and provide perspectives for the research and development of strategies to overcome cross-resistance and proceed towards a personalized approach.

The role of chemotherapy in metastatic prostate cancer

PURPOSE OF REVIEW

To summarize the role of chemotherapy and offer some guidance regarding the selection of chemotherapy in mPC.

RECENT FINDINGS

Patients with mHSPC have varied prognoses with testosterone suppression alone (androgen deprivation therapy, ADT) and differential responses to docetaxel with ADT. Patients with de novo and metachronous high-volume disease have a robust survival benefit with the addition of docetaxel to hormonal therapies. Patients with synchronous low-volume disease have a more modest survival benefit from docetaxel and there is no evidence of survival benefit with docetaxel in patients with metachronous low-volume disease. Integration of biomarkers may refine treatment selection regardless of volume of disease. Docetaxel and cabazitaxel also impart an OS benefit in patients with metastatic castration-resistant prostate cancer (mCRPC). The choice of chemotherapy in mCRPC depends on treatment received in mHSPC setting. Docetaxel remains the first line chemotherapy in castration-resistant patients who have not received it in mHSPC followed by cabazitaxel, otherwise cabazitaxel can be deployed without docetaxel retreatment.

SUMMARY

Chemotherapy is a key class of therapy for selected patients with mHSPC and mCRPC.

A Phase Ib/II Study of the CDK4/6 Inhibitor Ribociclib in Combination with Docetaxel plus Prednisone in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Ribociclib, a CDK4/6 inhibitor, demonstrates preclinical antitumor activity in combination with taxanes. We evaluated the safety and efficacy of ribociclib plus docetaxel in a phase Ib/II study in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients had chemotherapy-naïve mCRPC with progression on ≥ 1 androgen receptor signaling inhibitor (ARSI). The phase II primary endpoint was 6-month radiographic progression-free survival (rPFS) rate, with an alternative hypothesis of 55% versus 35% historical control. Circulating tumor cells (CTC) were collected at baseline and genomically profiled.

RESULT

Forty-three patients were enrolled (N = 30 in phase II). Two dose-limiting toxicities were observed (grade 4 neutropenia and febrile neutropenia). The recommended phase II dose (RP2D) and schedule was docetaxel 60 mg/m2 every 21 days plus ribociclib 400 mg/day on days 1-4 and 8-15 with filgrastim on days 5-7. At the RP2D, neutropenia was the most common grade ≥ 3 adverse event (37%); however, no cases of febrile neutropenia were observed. The primary endpoint was met; the 6-month rPFS rate was 65.8% [95% confidence interval (CI): 50.6%-85.5%; P = 0.005] and median rPFS was 8.1 months (95% CI, 6.0-10.0 months). Thirty-two percent of evaluable patients achieved a PSA50 response. Nonamplified MYC in baseline CTCs was associated with longer rPFS (P = 0.052).

CONCLUSIONS

The combination of intermittent ribociclib plus every-3-weeks docetaxel demonstrated acceptable toxicity and encouraging efficacy in ARSI-pretreated mCRPC. Genomic profiling of CTCs may enrich for those most likely to derive benefit. Further evaluation in a randomized clinical trial is warranted.

The emerging role of cross-resistance between taxanes and AR-targeting therapy in metastatic prostate cancer

Background:

To date, the number of prostate cancer ranked first among newly diagnosed malignant tumors in men from multiple countries. Localized prostate cancer could be controlled by curative therapy. However, for patients with metastatic prostate cancer (mPC), the prognosis is poor. As among first-line treatments of systemic therapies for mPC, docetaxel and androgen receptor (AR)-targeted therapies have been widely used. However, mPC patients inevitably developed resistance to the current therapy. More importantly, there is a cross-resistance between docetaxel-based chemotherapy and AR-targeting therapy during the treatment process, which could impair the overall survival benefits without proper administration.

Objective:

Therefore, it is urgent to elucidate the mechanism of cross-resistance and explore the optimal sequential strategy.

Methods:

Here, in this review, we systematically reviewed and summarised the updated literature on clinical evidence and mechanistic research of treatment resistance in mPC.

Results:

Emerging evidence indicated that AR splice variants, AR overexpression or mutations, AR nuclear translocation, as well as AR signaling reactivation collectively contributed to the cross-resistance. With the current understanding of cross-resistance, multiple solutions are promising for improving the benefits, including refining the sequencing of available therapies for mPC, in combination with potential targeted inhibitors or immune checkpoint inhibitors. Further studies are needed to explore the combination of emerging strategies and eventually control the progression of prostate cancer.

Conclusions:

This review defined the mutual and unique resistant mechanism of these treatments, which might help to focus and accelerate therapeutic research that may ultimately improve clinical outcomes for patients with prostate cancer.

Level of evidence:

Not applicable

Sequencing of Systemic Therapies in the Management of Advanced Prostate Cancer in India: a Delphi-Based Consensus

INTRODUCTION

With the availability of an increasing number of therapeutic options for advanced prostate cancer (APC), optimal sequencing and combination of therapies have emerged to be the areas of challenges. In the Indian context, there is a dearth of consensus recommendations to guide clinicians regarding optimal sequencing of therapy in APC management. A Delphi-based consensus regarding optimal therapy sequencing in APC management was developed by an expert panel of medical oncologists from across India.

METHODS

An expert scientific committee of 11 medical oncologists and an expert panel of 53 medical oncologists from India constituted the panel for the Delphi consensus. In the first phase, a questionnaire with 41 clinical statements was developed in several critical controversial areas in APC treatment. In the second phase, 29 clinical statements were reworked and sent to eight experts to obtain their opinions on best practices. The consensus ratings were based on a 9-point Likert scale. Based on the overall response, statements with a mean score of ≥ 7 with 1 outlier were considered as "consensus."

RESULTS

Degarelix was the preferred androgen deprivation therapy (ADT). While ADT plus docetaxel was the preferred option for metastatic castrate-sensitive/naïve prostate cancer patients with high-volume disease, ADT with abiraterone was the preferred choice for low-volume disease. Docetaxel was the preferred first-line treatment option in men who received ADT alone in the castrate-sensitive/naïve setting. For patients progressing on or after docetaxel for metastatic castrate-resistant prostate cancer (without prior abiraterone or enzalutamide), the experts reached a consensus on the use of enzalutamide as the preferred second-line treatment option. No consensus was reached for the third-line treatment options.

CONCLUSION

This article is intended to serve as a guide to help clinicians discuss with their patients as part of the shared and multidisciplinary decision-making for improved APC management in India.

Chemotherapy in metastatic castration-resistant prostate cancer: Current scenario and future perspectives

Taxanes - docetaxel and cabazitaxel - are the most active chemotherapy drugs currently used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, despite a good initial response and survival benefit, nearly all patients eventually develop resistance, which is an important barrier to long-term survival. Resistance to taxanes is also associated with cross-resistance to androgen receptor signaling inhibitors (ARSIs). Unfortunately, other than platinum-based treatments, which have demonstrated some benefit in a subset of patients with Aggressive Variant Prostate Cancer (AVPC), few therapeutic options are available to patients progressing to taxanes. Hence, more research is required to determine whether platinum-based chemotherapy will confer a survival benefit in mCRPC, and the identification of predictive biomarkers and the clinical evaluation of platinum compounds in molecularly selected patients is an urgent but unmet clinical need. The present review focuses on the current status of chemotherapy treatments in mCRPC, interactions with androgen deprivation therapy (ADT) and novel ARSIs, and the main mechanisms of resistance. We will examine the impact of platinum-based treatments in mCRPC and summarize the known predictive biomarkers of platinum response. Finally, future approaches and avenues will be discussed.

Finding the optimal treatment sequence in metastatic castration-resistant prostate cancer-a narrative review

Over the last two decades, there has been significant progress in the treatment of metastatic prostate cancer. Multiple treatments with diverse mechanisms of action have improved clinical outcomes for patients with metastatic castration-resistant prostate cancer (mCRPC) including taxane chemotherapy, immunotherapy, potent androgen receptor pathway inhibitors (ARPI), and radiopharmaceuticals (radium-223). As these treatments have entered standard clinical practise, clinicians have been challenged on how to optimally select and sequence them as the landmark studies establishing their efficacy had control arms with placebo or minimally effective therapy and there is a paucity of prospective trials examining treatment sequencing. More recently, the situation has been further complicated as the earlier up-front use of docetaxel and ARPI with standard gonadal testosterone inhibition has been shown to impart substantial improvements in disease control and survival for patients with castration sensitive prostate cancer. As new therapies enter into clinical practise such as the inhibitors of Poly (ADP-Ribose) Polymerase and Prostate Specific Membrane Antigen (PSMA)-targeted therapy, how to optimally select and sequence available treatments will be a continued dilemma in the absence of validated predictive biomarkers. This review will summarize the literature supporting the use of each active agent in mCRPC. We will propose a framework which will guide the selection of appropriate agents based on prior therapies, disease characteristics and biomarkers.

Prognostic role of the duration of response to androgen deprivation therapy in patients with metastatic castration resistant prostate cancer treated with enzalutamide or abiraterone acetate

BACKGROUND

Our retrospective study aims to evaluate the prognostic role of duration of response to androgen deprivation therapy (ADT) in metastatic castration resistant prostate cancer (mCRPC) patients treated with enzalutamide (E) or abiraterone acetate (AA).

MATERIALS AND METHODS

Data about ADT start and duration were available in 255 (82%) of 311 patients treated with AA or E. Patients were divided in three groups according to ADT response (group 1 [G1]: <12 months; group 2 [G2]: 12-36 months; group 3 [G3]: >36 months). Outcome measures were progression-free survival (PFS) and overall survival (OS).

RESULTS

Patients with longer ADT response had better OS (median 17.3 months G1, 19.9 months G2, 31.6 months G3; HR G3 vs G1 0.41, 95% CI 0.25-0.64; p = 0.001) and better PFS (median 5.9 months G1, 8.8 months G2, 11.7 months G3; HR G3 vs G1 0.41, 95% CI 0.41-0.27; p < 0001). In docetaxel-naive patients, median OS was 18.8 in G1, 35.2 in G2, and not reached in G3 (HR G3 vs G1 0.33, 95% CI 0.14-0.78; p = 0.038), median PFS was 7 months G1, 9.3 months G2, and 20 months G3 (HR G3 vs G1 0.31, 95% CI 0.15-0.62; p = 0.003). In postdocetaxel patients, median OS was 13.1 months in G1, 17.2 months in G2, and 21.4 months in G3 (HR G3 vs G1 0.52, 95% CI 0.29-0.94; p = 0.082), while median PFS was 5.2 months in G1, 6.8 months in G2, and 8.3 months in G3 (HR G3 vs G1 0.54, 95% CI 0.32-0.91; p = 0.067).

CONCLUSIONS

Duration of ADT response is an independent prognostic factor of outcome with AA or E.

Prognostic role of docetaxel-induced suppression of free testosterone serum levels in metastatic prostate cancer patients

To date, only few data concerning the biologically active, free form of testosterone (FT) are available in metastatic prostate cancer (mPC) and the impact of FT on disease, therapy and outcome is largely unknown. We retrospectively studied the effect of docetaxel on FT and total testosterone (TT) serum levels in 67 mPC patients monitored between April 2008 and November 2020. FT and TT levels were measured before and weekly during therapy. The primary endpoint was overall survival (OS). Secondary endpoints were prostate-specific antigen response and radiographic response (PSAR, RR), progression-free survival (PFS), FT/TT levels and safety. Median FT and TT serum levels were completely suppressed to below the detection limit during docetaxel treatment (FT: from 0.32 to < 0.18 pg/mL and TT: from 0.12 to < 0.05 ng/mL, respectively). Multivariate Cox regression analyses identified requirement of non-narcotics, PSAR, complete FT suppression and FT nadir values < 0.18 pg/mL as independent parameters for PFS. Prior androgen-receptor targeted therapy (ART), soft tissue metastasis and complete FT suppression were independent prognostic factors for OS. FT was not predictive for treatment outcome in mPC patients with a history of ART.

Beyond Frontline Therapy with Abiraterone and Enzalutamide in Metastatic Castration-Resistant Prostate Cancer: A Real-World US Study

BACKGROUND

Real-world evidence suggest that next generation hormonal agents (NHAs) abiraterone and enzalutamide were preferred as first-line (1L) therapies for metastatic castration-resistant prostate cancer (mCRPC) in the United States (US) pre-2020, with chemotherapies, particularly docetaxel, being preferred in subsequent lines (2L+). This real-world study described patient characteristics, treatment patterns, time on treatment (ToT) and overall survival (OS) among patients with mCRPC treated with 2L and 3L docetaxel post-NHAs in the mCRPC setting.

METHODS

Adults with confirmed adenocarcinoma mCRPC diagnosis and ≥1 month of follow-up post-diagnosis were selected from a US electronic health record-derived oncology de-identified database (01/2013-03/2019). Based on the observed line of therapy sequences post-mCRPC diagnosis, patients who received NHA therapy in 1L and docetaxel therapy in 2L were included in the 2L docetaxel cohort, and patients who received NHA therapy in both 1L and 2L and docetaxel therapy in 3L were included in the 3L docetaxel cohort. ToT and OS were evaluated using Kaplan-Meier analysis.

RESULTS

Among 5,213 patients with mCRPC, 278 and 166 were included in the 2L and the 3L docetaxel cohorts, respectively (median age: 73 years for both cohorts). ADT was the most used class of medication pre-mCRPC (>75%). For the 2L cohort, the most common sequence post-mCRPC was 1L abiraterone → 2L docetaxel (52.5%), while the median ToT and OS post-2L start were 4.1 and 10.5 months, respectively; for the 3L cohort, the most common sequence post-mCRPC was 1L abiraterone → 2L enzalutamide → 3L docetaxel (67.5%), while the median ToT and OS post-3L start were 3.8 and 8.7 months, respectively.

CONCLUSIONS

This real-world study provides novel data on patients treated with docetaxel post-NHAs in a mCRPC setting and highlights the critical unmet need for developing more effective treatment options in this population.

Cross-resistance and drug sequence in prostate cancer

The treatment landscape of advanced prostate cancer has widely expanded over the past years with androgen receptor signaling inhibitors (ARSIs) and taxane chemotherapy moving to earlier disease stages in the treatment of prostate cancer. With the increasing use of ARSIs in earlier disease stages, cross-resistance between treatments has emerged, which is a dominant impediment in current clinical practice. To overcome cross-resistance in the treatment of prostate cancer, it is of paramount importance to decipher the mechanisms of cross-resistance between ARSIs and between ARSIs and chemotherapy. Here, molecular mechanisms of resistance to the available therapies including androgen receptor (AR) splice variants, AR overexpression, AR mutations and glucocorticoid receptor upregulation are described. Based on these underlying mechanisms, clinical data of cross-resistance between ARSIs and chemotherapy have been reported. Only recently these data have been confirmed in prospective randomized trials. From these studies, it has become clear that sequential ARSI treatment has no place in the treatment of advanced prostate cancer due to emerging drug resistance. In addition, based on prospective evidence, we argue that it is worth considering an early switch to cabazitaxel treatment in case of lack of benefit on docetaxel regimen after an ARSI treatment. Based on these new insights from randomized trials, several recommendations for treatment sequence are proposed.

Cabazitaxel versus abiraterone or enzalutamide in metastatic castration-resistant prostate cancer: post hoc analysis of the CARD study excluding chemohormonal therapy for castrate-naive disease

Background

In the CARD study (NCT02485691), cabazitaxel significantly improved clinical outcomes versus abiraterone or enzalutamide in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel and the alternative androgen-signalling-targeted inhibitor. However, some patients received docetaxel or the prior alternative androgen-signalling-targeted inhibitor in the metastatic hormone-sensitive (mHSPC) setting. Therefore, the CARD results cannot be directly translated to a Japanese population.

Methods

Patients (N = 255) received cabazitaxel (25 mg/m² IV Q3W, prednisone, G-CSF) versus abiraterone (1000 mg PO, prednisone) or enzalutamide (160 mg PO) after prior docetaxel and progression ≤12 months on the alternative androgen-signalling-targeted inhibitor. Patients who received combination therapy for mHSPC were excluded (n = 33) as docetaxel is not approved in this setting in Japan.

Results

A total of 222 patients (median age 70 years) were included in this subanalysis. Median number of cycles was higher for cabazitaxel versus androgen-signalling-targeted inhibitors (7 versus 4). Clinical outcomes favoured cabazitaxel over abiraterone or enzalutamide including, radiographic progression-free survival (rPFS; median 8.2 versus 3.4 months; P < 0.0001), overall survival (OS; 13.9 versus 11.8 months; P = 0.0102), PFS (4.4 versus 2.7 months; P < 0.0001), confirmed prostate-specific antigen response (37.0 versus 14.4%; P = 0.0006) and objective tumour response (38.9 versus 11.4%; P = 0.0036). For cabazitaxel versus androgen-signalling-targeted inhibitor, grade ≥ 3 adverse events occurred in 55% versus 44% of patients, with adverse events leading to death on study in 2.7% versus 5.7%.

Conclusions

Cabazitaxel significantly improved outcomes including rPFS and OS versus abiraterone or enzalutamide and are reflective of the Japanese patient population. Cabazitaxel should be considered the preferred treatment option over abiraterone or enzalutamide in this setting.

Preclinical Models in Prostate Cancer: Resistance to AR Targeting Therapies in Prostate Cancer

Prostate cancer is an androgen-driven tumor. Different prostate cancer therapies consequently focus on blocking the androgen receptor pathway. Clinical studies reported tumor resistance mechanisms by reactivating and bypassing the androgen pathway. Preclinical models allowed the identification, confirmation, and thorough study of these pathways. This review looks into the current and future role of preclinical models to understand resistance to androgen receptor-targeted therapies. Increasing knowledge on this resistance will greatly improve insights into tumor pathophysiology and future treatment strategies in prostate cancer.

Cost-effectiveness analysis of cabazitaxel for metastatic castration resistant prostate cancer after docetaxel and androgen-signaling-targeted inhibitor resistance

Background

The aim of our study was to evaluate the cost-effectiveness of cabazitaxel versus abiraterone or enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with docetaxel who had progression within 12 months while receiving an alternative inhibitor (abiraterone or enzalutamide) from a US payer’s perspective.

Methods

To conduct the cost-effectiveness analysis, a Markov decision model was established. Three health states (progression-free survival (PFS), progressive disease (PD) and death) were included, and the incremental cost-effectiveness ratio (ICER) was regarded as the primary endpoint. The willingness-to-pay (WTP) threshold was set at $100,000.00/quality-adjusted life year (QALY), and discounted rates were set at 3% annually. Efficacy data were derived from the CARD trial and Weibull distribution curves were modeled to fit the survival curves. The robustness of the analysis was tested with a series of one-way sensitivity analyses and probabilistic sensitivity analyses.

Results

Overall, the incremental effectiveness and cost of cabazitaxel versus androgen-signaling-targeted inhibitors (ASTIs) were 0.16 QALYs and $49,487.03, respectively, which yielded an ICER of $309,293.94/QALY. Our model was mostly sensitive to the duration of PFS in the cabazitaxel group, cost of cabazitaxel and utility of the PFS state. At a WTP threshold of $100,000.00/QALY, cabazitaxel was the dominant strategy in 0% of the simulations.

Conclusions

Cabazitaxel is unlikely to be a cost-effective treatment option compared with ASTIs in patients with mCRPC previously treated with docetaxel who had progression within 12 months while receiving ASTIs.

Cost-Effectiveness Assessment of Monitoring Abiraterone Levels in Metastatic Castration-Resistant Prostate Cancer Patients

OBJECTIVES

Abiraterone acetate is registered for the treatment of metastatic castration-sensitive and resistant prostate cancer (mCRPC). Treatment outcome is associated with plasma trough concentrations (C_min) of abiraterone. Patients with a plasma C_min below the target of 8.4 ng/mL may benefit from treatment optimization by dose increase or concomitant intake with food. This study aims to investigate the cost-effectiveness of monitoring abiraterone C_min in patients with mCRPC.

METHODS

A Markov model was built with health states progression-free survival, progressed disease, and death. The benefits of monitoring abiraterone C_min followed by a dose increase or food intervention were modeled via a difference in the percentage of patients achieving adequate C_min taking a healthcare payer perspective. Deterministic and probabilistic sensitivity analyses were performed to assess uncertainties and their impac to the incremental cost-effectiveness ratio (ICER).

RESULTS

Monitoring abiraterone followed by a dose increase resulted in 0.149 incremental quality-adjusted life-years (QALYs) with €22 145 incremental costs and an ICER of €177 821/QALY. The food intervention assumed equal effects and estimated incremental costs of €7599, resulting in an ICER of €61 019/QALY. The likelihoods of therapeutic drug monitoring (TDM) with a dose increase or food intervention being cost-effective were 8.04%and 81.9%, respectively.

CONCLUSIONS

Monitoring abiraterone followed by a dose increase is not cost-effective in patients with mCRPC from a healthcare payer perspective. Monitoring in combination with a food intervention is likely to be cost-effective. This cost-effectiveness assessment may assist decision making in future integration of abiraterone TDM followed by a food intervention into standard abiraterone acetate treatment practices of mCRPC patients.

[Systemic treatment of advanced prostate cancer]

In recent years there have been substantial changes in the therapeutic landscape for systemic treatment of advanced prostate cancer (PCa), which resulted in a multitude of novel treatment options for different stages of the disease. In the current narrative review currently available treatment options for metastatic hormone-sensitive PCa as well as nonmetastatic castration-resistant PCa are presented. In addition, current treatment sequence options and targeted treatment in the stage of metastatic castration-resistant PCa are highlighted.

Efficacy of cabazitaxel and the influence of clinical factors on the overall survival of patients with castration-resistant prostate cancer: A local experience of a multicenter retrospective study

AIM

To date, the optimal sequencing of life-prolonging therapies for patients with metastatic castration-resistant prostate cancer (mCRPC) remains unclear owing to a lack of prospective trials. This study aimed to evaluate the efficacy and safety of cabazitaxel (CBZ) treatment and examine the prognostic factors for oncological outcomes in patients with mCRPC who received CBZ after docetaxel (DOC).

METHODS

This multi-institutional retrospective study included 44 patients with mCRPC who received CBZ. All enrolled patients had histologically confirmed prostate cancer (PCa) with distant metastases and had received DOC before CBZ administration. The primary endpoint was the oncological outcomes, including the overall (OS) and progression-free survival (PFS). The secondary endpoints were adverse events due to CBZ and rates of ≥30% reduction in prostate-specific antigen (PSA) levels.

RESULTS

The median follow-up period was 9.2 months (range, 0.2-34 months). During this time, 34 patients (77%) died of PCa. The median OS and PFS were 12.2 (range, 0.2-34 months) and 1.4 months (range, 0.4-17 months), respectively. According to the PSA decline rate, patients who achieved a ≥30% reduction in PSA levels had significantly longer OS than those who showed a <30% reduction in PSA levels (P = 0.002). Regarding the number of cycles of CBZ, patients who received ≥4 cycles of CBZ showed significantly longer OS than those who received <4 cycles of CBZ (P < 0.001). Patients who had visceral metastasis showed significantly shorter OS than those without visceral metastasis (P = 0.012).

CONCLUSION

This study demonstrated that CBZ was effective and safe in Japanese local patients in a real-world setting. Patients with mCRPC who received ≥4 cycles of CBZ showed a ≥30% reduction in the serum PSA levels, and did not have visceral metastasis might achieve longer OS.

Preclinical studies show using enzalutamide is less effective in docetaxel-pretreated than in docetaxel-naïve prostate cancer cells

Anti-androgen therapy with Enzalutamide (Enz) has been used as a therapy for castration resistant prostate cancer (CRPC) patients after development of resistance to chemotherapy with Docetaxel (Doc). The potential impacts of Doc-chemotherapy on the subsequent Enz treatment, however, remain unclear. Here we found the overall survival rate of patients that received Enz was significantly less in patients that received prior Doc-chemotherapy than those who had not. In vitro studies from 3 established Doc resistant CRPC (DocRPC) cell lines are consistent with the clinical findings showing DocRPC patients had decreased Enz-sensitivity as well as accelerated development of Enz-resistance via enhanced androgen receptor (AR) splicing variant 7 (ARv7) expression. Mechanism dissection found that Doc treatment might increase the generation of ARv7 via altering the MALAT1-SF2 RNA splicing complex. Preclinical studies using in vivo mouse models and in vitro cell lines proved that targeting the MALAT1/SF2/ARv7 axis with small molecules, including siMALAT1, shSF2, and shARv7 or ARv7 degradation enhancers: Cisplatin or ASC-J9®, can restore/increase the Enz sensitivity to further suppress DocRPC cell growth. Therefore, combined therapy of Doc-chemotherapy with anti-ARv7 therapy, including Cisplatin or ASC-J9®, may be developed to increase the efficacy of Enz to further suppress DocRPC in patients.

Abiraterone vs. docetaxel for metastatic hormone-sensitive prostate cancer: A microsimulation model

INTRODUCTION

Our aim was to determine whether androgen deprivation therapy (ADT) with abiraterone acetate (AA) or ADT with docetaxel chemotherapy (DC) resulted in improved quality-adjusted life years (QALYs) among men with de novo metastatic castration-sensitive prostate cancer (mCSPC) and the cost effectiveness of the preferred strategy using decision analytic techniques.

METHODS

A microsimulation model with a lifetime time horizon was constructed. Our primary outcome was QALYs. Secondary outcomes included cost, incremental cost effectiveness ratio (ICER), unadjusted overall survival (OS), rates of second- and third-line therapy, and adverse events. A systematic literature review was used to generate probabilities and utilities to populate the model. The base case was a 65-year-old patient with de novo mCSPC.

RESULTS

A total of 100 000 microsimulations were generated. Initial AA resulted in a gain of 0.45 QALYs compared to DC (3.36 vs. 2.91 QALYs) with an ICER of $276 251.82 per QALY gained with initial AA therapy. Median crude OS was 51 months with AA and 48 months with DC. Overall, 46.6% and 42.6% of patients received second-line therapy and 8.7% and 7.9% patients received third-line therapy in the AA and DC groups, respectively. Grade 3/4 adverse events were experienced in 17.6% of patients receiving initial AA and 22.3% of patients receiving initial DC.

CONCLUSIONS

Although ADT with AA results in a gain in QALYs and crude OS compared to DC, AA therapy is not a cost-effective treatment strategy to apply uniformly to all patients. The availability of AA as a generic medication may help to close this gap. The ultimate choice should be based on patient and tumor factors.

Clinical outcomes of abiraterone acetate and predictors of its treatment duration in metastatic castration-resistant prostate cancer: Real-world experience in the Southeast Asian cohort

It is of much interest to understand the efficacy of abiraterone acetate (AA) in routine clinical practice. We assessed the clinical outcome of AA in patients with metastatic castration-resistant prostate cancer (mCRPC) and determined clinical factors associated with AA treatment duration in real-world setting. This real-world cohort consisted of 93 patients with mCRPC treated with AA in Thailand (58.1%) and Malaysia (41.9%). Primary endpoints were overall survival (OS) and biochemical progression-free survival (bPFS). Secondary endpoints were predictors associated with AA treatment duration evaluated with Cox proportional hazards regression. Around 74% were chemotherapy-naïve. The median AA treatment duration was 10 months (IQR 5.6-17.1). Malaysians had a relatively lower median OS and bPFS (OS 17.8 months; 95% CI 6.4-29.1, bPFS 10.4 months; 95% CI 8.8-12.0) compared to Thais (OS 27.0 months; 95% CI 11.3-42.7, bPFS 14.0 months; 95% CI 5.8-22.2), although it did not achieve statistical significance (P > .05). Patients with longer AA treatment duration (>10 months) had lower risk of death and longer bPFS, compared to those with shorter AA treatment duration (≤10 months) (hazard ratio [HR] 0.10, 95% CI 0.05-0.22 and HR 0.13, 95% CI 0.06-0.25, respectively). Multivariable analysis showed that PSA at AA initiation, presence of PSA response and chemotherapy-naive were independently associated with AA duration (P < .05). Abiraterone acetate is well-tolerated in the Southeast Asian cohort with comparable survival benefits to other Asian populations in real-world setting. Lower PSA levels at AA initiation, presence of PSA response, and chemotherapy-naive were significant in determining AA treatment duration.

Impact of taxanes on androgen receptor signaling

The development and progression of metastatic castration-resistant prostate cancer is the major challenge in the treatment of advanced prostate cancer. The androgen receptor signaling pathway remains active in metastatic castration-resistant prostate cancer. Docetaxel and cabazitaxel are the first- and second-line chemotherapy, respectively, for patients with metastatic castration-resistant prostate cancer. These two taxanes, in general, function by (i) inhibiting mitosis and inducing apoptosis and (ii) preventing microtubule-dependent cargo trafficking. In prostate cancer, taxanes have been reported to inhibit the nuclear translocation and activity of the androgen receptor. However, whether this is attainable or not clinically remains controversial. In this review, we will provide a comprehensive view of the effects of taxanes on androgen receptor signaling in prostate cancer.

Docetaxel Rechallenge in Patients with Metastatic Prostate Cancer: A Comprehensive Review

BACKGROUND

Recent years have witnessed a huge shift in the management and prognosis of metastatic prostate cancer with the advent of new-generation anti-hormonal treatments. Docetaxel, which was initially approved in the castrate-resistant prostate cancer setting, has been approved in the earlier course of the disease as it is still castrate sensitive.

SUMMARY

Apart from cabazitaxel and in the absence of other effective chemotherapies, docetaxel rechallenge (DR) in patients with proved sensitivity to docetaxel in the earlier stage of the disease remains a possible option. Unfortunately, the pivotal trials rarely reported on the outcomes of docetaxel retreatment which seems a plausible option in patients initially responding to docetaxel and maintaining a minimum progression-free interval of 3-6 months. In this review, a summary of the clinical evidence and potential concerns for the use of DR in patients with metastatic prostate cancer will be presented. Key Messages: Pivotal trials of docetaxel in metastatic castrate-sensitive prostate cancer as well as metastatic castrate-resistant prostate cancer have not reported on the outcomes of DR except in the GETUG-AFU 15 trial where the outcomes were disappointing. Based on the published retrospective data, DR may be effective in patients who initially responded to docetaxel and maintained a progression-free interval exceeding 6 months.

Role of CYP3A5 in Modulating Androgen Receptor Signaling and Its Relevance to African American Men with Prostate Cancer

Androgen receptor signaling is crucial for prostate cancer growth and is positively regulated in part by intratumoral CYP3A5. As African American (AA) men often carry the wild type CYP3A5 and express high levels of CYP3A5 protein, we blocked the wild type CYP3A5 in AA origin prostate cancer cells and tested its effect on androgen receptor signaling. q-PCR based profiler assay identified several AR regulated genes known to regulate AR nuclear translocation, cell cycle progression, and cell growth. CYP3A5 processes several commonly prescribed drugs and many of these are CYP3A5 inducers or inhibitors. In this study, we test the effect of these commonly prescribed CYP3A5 inducers/inhibitors on AR signaling. The results show that the CYP3A5 inducers promoted AR nuclear translocation, downstream signaling, and cell growth, whereas CYP3A5 inhibitors abrogated them. The observed changes in AR activity is specific to alterations in CYP3A5 activity as the effects are reduced in the CYP3A5 knockout background. Both the inducers tested demonstrated increased cell growth of prostate cancer cells, whereas the inhibitors showed reduced cell growth. Further, characterization and utilization of the observation that CYP3A5 inducers and inhibitors alter AR signaling may provide guidance to physicians prescribing CYP3A5 modulating drugs to treat comorbidities in elderly patients undergoing ADT, particularly AA.

Prostate-specific membrane antigen in circulating tumor cells is a new poor prognostic marker for castration-resistant prostate cancer

The aim of this study is to elucidate the clinical significance of prostate-specific membrane antigen (PSMA) expression in circulating tumor cells (CTCs) from castration-resistant prostate cancer (CRPC) patients. We analyzed a total of 203 CTC samples from 79 CRPC patients to investigate the proportion of positive mRNA expressions at different treatment phases. Among them, we elected to focus on specimens from 56 CRPC patients who progressed on therapy and were subsequently provided a new treatment (treatment-switch cohort). In this cohort, we investigated the association between PSMA expression in CTCs and treatment response. CTCs were detected in 55/79 patients and median serum PSA in CTC-positive patients was 67.0 ng/ml. In the treatment-switch cohort of 56 patients, 20 patients were positive for PSMA in CTCs. PSMA expression was inversely associated with percentage of change in prostate-specific antigen (PSA). The median PSA progression-free survival and overall survival were significantly shorter in the PSMA-positive cohort. Furthermore, PSMA expression was predictive of poorer treatment response, shorter PSA progression-free survival and overall survival. PSMA expression in circulating tumor cells may be a novel poor prognostic marker for CRPC.

Cabazitaxel versus Abiraterone or Enzalutamide in Metastatic Prostate Cancer

BACKGROUND

The efficacy and safety of cabazitaxel, as compared with an androgen-signaling-targeted inhibitor (abiraterone or enzalutamide), in patients with metastatic castration-resistant prostate cancer who were previously treated with docetaxel and had progression within 12 months while receiving the alternative inhibitor (abiraterone or enzalutamide) are unclear.

METHODS

We randomly assigned, in a 1:1 ratio, patients who had previously received docetaxel and an androgen-signaling-targeted inhibitor (abiraterone or enzalutamide) to receive cabazitaxel (at a dose of 25 mg per square meter of body-surface area intravenously every 3 weeks, plus prednisone daily and granulocyte colony-stimulating factor) or the other androgen-signaling-targeted inhibitor (either 1000 mg of abiraterone plus prednisone daily or 160 mg of enzalutamide daily). The primary end point was imaging-based progression-free survival. Secondary end points of survival, response, and safety were assessed.

RESULTS

A total of 255 patients underwent randomization. After a median follow-up of 9.2 months, imaging-based progression or death was reported in 95 of 129 patients (73.6%) in the cabazitaxel group, as compared with 101 of 126 patients (80.2%) in the group that received an androgen-signaling-targeted inhibitor (hazard ratio, 0.54; 95% confidence interval [CI], 0.40 to 0.73; P<0.001). The median imaging-based progression-free survival was 8.0 months with cabazitaxel and 3.7 months with the androgen-signaling-targeted inhibitor. The median overall survival was 13.6 months with cabazitaxel and 11.0 months with the androgen-signaling-targeted inhibitor (hazard ratio for death, 0.64; 95% CI, 0.46 to 0.89; P = 0.008). The median progression-free survival was 4.4 months with cabazitaxel and 2.7 months with an androgen-signaling-targeted inhibitor (hazard ratio for progression or death, 0.52; 95% CI, 0.40 to 0.68; P<0.001), a prostate-specific antigen response occurred in 35.7% and 13.5% of the patients, respectively (P<0.001), and tumor response was noted in 36.5% and 11.5% (P = 0.004). Adverse events of grade 3 or higher occurred in 56.3% of patients receiving cabazitaxel and in 52.4% of those receiving an androgen-signaling-targeted inhibitor. No new safety signals were observed.

CONCLUSIONS

Cabazitaxel significantly improved a number of clinical outcomes, as compared with the androgen-signaling-targeted inhibitor (abiraterone or enzalutamide), in patients with metastatic castration-resistant prostate cancer who had been previously treated with docetaxel and the alternative androgen-signaling-targeted agent (abiraterone or enzalutamide). (Funded by Sanofi; CARD ClinicalTrials.gov number, NCT02485691.).

Orally Bioavailable Androgen Receptor Degrader, Potential Next-Generation Therapeutic for Enzalutamide-Resistant Prostate Cancer

PURPOSE

Androgen receptor (AR)-targeting prostate cancer drugs, which are predominantly competitive ligand-binding domain (LBD)-binding antagonists, are inactivated by common resistance mechanisms. It is important to develop next-generation mechanistically distinct drugs to treat castration- and drug-resistant prostate cancers.

EXPERIMENTAL DESIGN

Second-generation AR pan antagonist UT-34 was selected from a library of compounds and tested in competitive AR binding and transactivation assays. UT-34 was tested using biophysical methods for binding to the AR activation function-1 (AF-1) domain. Western blot, gene expression, and proliferation assays were performed in various AR-positive enzalutamide-sensitive and -resistant prostate cancer cell lines. Pharmacokinetic and xenograft studies were performed in immunocompromised rats and mice.

RESULTS

UT-34 inhibits the wild-type and LBD-mutant ARs comparably and inhibits the in vitro proliferation and in vivo growth of enzalutamide-sensitive and -resistant prostate cancer xenografts. In preclinical models, UT-34 induced the regression of enzalutamide-resistant tumors at doses when the AR is degraded; but, at lower doses, when the AR is just antagonized, it inhibits, without shrinking, the tumors. This indicates that degradation might be a prerequisite for tumor regression. Mechanistically, UT-34 promotes a conformation that is distinct from the LBD-binding competitive antagonist enzalutamide and degrades the AR through the ubiquitin proteasome mechanism. UT-34 has a broad safety margin and exhibits no cross-reactivity with G-protein-coupled receptor kinase and nuclear receptor family members.

CONCLUSIONS

Collectively, UT-34 exhibits the properties necessary for a next-generation prostate cancer drug.

[Treatment situation in metastastic Castration Naive Prostate Cancer (mCRPC) and the implications on clinical routine]

There is an ongoing change of paradigm in the treatment of metastatic prostate cancer (mPC). Taxan-based chemotherapy demonstrated a prolonged survival of patients in several randomized phase III trials. This is true in the situation of metastatic castration-resistent prostate cancer (mCRPC) as well as in the hormone-naïve stage (metastatic castration-naive PC [mCNPC]). In patients with mCNPC, treatment with docetaxel in combination with androgen deprivation therapy (ADT) prolonged the median total survival time by 15 months in comparison to ADT alone. Comparable results were obtained by the endocrine combination treatment with ADT/abiraterone. With the current data in mind it seems to be useful to discuss the value of early combination therapy with ADT/docetaxel or ADT/abiraterone as well as the impact on further treatment options in the mCRPC setting and to define criteria for treatment decisions in clinical practice.

The role of ketoconazole in current prostate cancer care

Ketoconazole is a nonselective steroid 17α-hydroxylase/17,20 lyase (CYP17A1) inhibitor that has been used, off-label, as a second-line therapy for castration-resistant prostate cancer (CRPC). The drug has shown clinical efficacy without survival benefit. Despite not improving survival, ketoconazole has beneficial characteristics, such as its low cost, a relatively favourable toxicity profile compared with chemotherapy, and its efficacy both before and after chemotherapy. The approval of several new, highly effective treatments, including abiraterone acetate, enzalutamide, and apalutamide, warrants re-evaluation of the role of ketoconazole and other classic agents in achieving the optimal timing and sequencing of available agents to prolong survival and maintain patients' quality of life. In the current CRPC treatment landscape, we believe that ketoconazole can be considered in patients with nonmetastatic CRPC and in those with metastatic CRPC who do not respond to, tolerate, or have access to chemotherapy and other standard therapeutic options.

Sequencing strategies in the new treatment landscape of prostate cancer

Over the last 10 years, a number of new agents approved for the treatment of metastatic castration-resistant prostate cancer have led to a significant improvement in overall survival. The addition of new agents to androgen deprivation therapy has also allowed a paradigmatic change in the treatment of metastatic hormone-sensitive prostate cancer by improving overall survival in comparison with androgen deprivation therapy alone. Furthermore, recent data concerning the efficacy of three different androgen receptor-targeting agents in patients with nonmetastatic castration-resistant prostate cancer have opened up new scenarios for future patients' management. Defining the best sequencing strategies for men with prostate cancer is a currently unmet medical need, and choosing treatment is often challenging for clinicians because of the lack of direct comparisons of the available agents. The aim of this paper is to provide a comprehensive review of the literature concerning current sequencing strategies for prostate cancer patients.

Pantoprazole Affecting Docetaxel Resistance Pathways via Autophagy (PANDORA): Phase II Trial of High Dose Pantoprazole (Autophagy Inhibitor) with Docetaxel in Metastatic Castration-Resistant Prostate Cancer (mCRPC)

BACKGROUND

Enhancing the effectiveness of docetaxel for men with metastatic castration-resistant prostate cancer (mCRPC) is an unmet clinical need. Preclinical studies demonstrated that high-dose pantoprazole can prevent or delay resistance to docetaxel via the inhibition of autophagy in several solid tumor xenografts.

MATERIALS AND METHODS

Men with chemotherapy-naive mCRPC with a prostate-specific antigen (PSA) >10 ng/mL were eligible for enrolment. Men received intravenous pantoprazole (240 mg) prior to docetaxel (75 mg/m²) every 21 days, with continuous prednisone 5 mg twice daily. Primary endpoint was a confirmed ≥50% decline of PSA. The trial used a Simon's two-stage design.

RESULTS

Between November 2012 and March 2015, 21 men with a median age of 70 years (range, 58-81) were treated (median, 6 cycles; range, 2-11). Men had received prior systemic therapies (median, 1; range, 0-3), and 14 had received abiraterone and/or enzalutamide. PSA response rate was 52% (11/21), which did not meet the prespecified criterion (≥13/21 responders) to proceed to stage 2 of the study. At interim analysis with a median follow-up of 17 months, 18 (86%) men were deceased (15 castration-resistant prostate cancer, 2 unknown, 1 radiation complication). Of the men with RECIST measurable disease, the radiographic partial response rate was 31% (4/13). The estimated median overall survival was 15.7 months (95% confidence interval [CI], 9.3-19.6) and median PFS was 5.3 months (95% CI, 2.6-12.9). There were no toxic deaths, and all adverse events were attributed to docetaxel.

CONCLUSION

The combination of docetaxel and pantoprazole was tolerable, but the resultant clinical activity was not sufficient to meet the ambitious predefined target to warrant further testing.

IMPLICATIONS FOR PRACTICE

To date, no docetaxel combination regimen has reported superior efficacy over docetaxel alone in men with metastatic castration-resistant prostate cancer (mCRPC). The PANDORA trial has demonstrated that the combination of high dose pantoprazole with docetaxel is tolerable, but the clinical activity was not sufficient to warrant further testing. The chemotherapy standard of care for men with mCRPC remains docetaxel with prednisone. Future studies of autophagy inhibitors will need to measure autophagy inhibition accurately and determine the degree of autophagy inhibition required to produce a meaningful clinical response.

Impact of new systemic therapies on overall survival of patients with metastatic castration-resistant prostate cancer in a hospital-based registry

BACKGROUND

In 2004, docetaxel was shown to prolong the overall survival (OS) of patients with metastatic castration-resistance prostate cancer (mCRPC). Since 2010, five new systemic therapies have been shown to prolong OS in men with mCRPC. We sought to evaluate the aggregate impact of these newer therapies on the OS of patients with mCRPC.

METHODS

Two cohorts of patients diagnosed with mCRPC between 2004 and 2007, treated with drugs used in the limited treatment era only (A), and between 2010 and 2013, treated also with newer therapies (B), were identified from the Dana-Farber Cancer Institute database. The analysis endpoint was OS within 5 years after mCRPC diagnosis. Kaplan-Meier method assessed time-to-event distributions with median (95% confidence interval (CI)). A piece-wise regression model assessed the association between endpoint and treatment cohorts with estimate of hazard ratio (HR) with 95% CI within two time segments in univariate and multivariable analyses adjusting for relevant covariates.

RESULTS

Compared to cohort A (n = 318), cohort B (n = 272) patients in newer therapy era demonstrated an OS advantage (2.8 vs. 2.2 years) with a 41% decreased risk of death (HR = 0.59; 95% CI, 0.47-0.74; P < 0.0001), and a 3-year OS rate of 46% vs. 33%. This benefit was accentuated (median OS 2.7 vs. 2.1 years; HR = 0.46; 95% CI, 0.32-0.67; P < 0.0001) in patients who initially presented with de-novo metastatic disease (de-novo). On multivariable analysis, longer OS was associated with cohort B vs. A and performance status 0 vs. 1.

CONCLUSIONS

Using a single-institution registry, mCRPC patients treated since 2010 had a significant survival improvement vs. those treated before 2010. Although the median survival was only modestly improved and less than predicted when simply adding each newer drug survival advantage, the cumulative benefit from the new therapies was more pronounced in longer-term survivors and de-novo patients.

Cabazitaxel inhibits prostate cancer cell growth by inhibition of androgen receptor and heat shock protein expression

PURPOSE

Cabazitaxel, a semi-synthetic taxane of the third generation, inhibits prostate cancer (PC) cell growth by affecting the microtubule architecture. Since cabazitaxel has also been demonstrated to inhibit androgen receptor (AR) functionality, AR and AR-associated heat shock protein (HSP) expressions in the presence of cabazitaxel were characterized.

METHODS

AR and HSP expressions were assessed via Western blotting utilizing a PC-cell-line in vitro system incubated with cabazitaxel.

RESULTS

Incubation experiments with 0.3 nM cabazitaxel exhibited significantly reduced levels of AR and the AR-associated factors HSP90α, HSP40, and HSP70/HSP90 organising protein. Furthermore, expression of the anti-apoptotic factor HSP60 was suppressed. In contrast to other anticancer compounds, cabazitaxel did not alter the cytoprotective chemoresistance factor HSP27.

CONCLUSIONS

Despite the deregulation of microtubule organisation, cabazitaxel has been shown to suppress the expression of HSP. Very notably, and may be as a result of down-regulated HSP, cabazitaxel additionally inhibits the expression of the AR in AR-positive PC cells. Thus, cabazitaxel bears an additional anti-proliferative activity which is at least in part specific for PC cells.

Enzalutamide therapy for advanced prostate cancer: efficacy, resistance and beyond

The androgen receptor drives the growth of metastatic castration-resistant prostate cancer. This has led to the development of multiple novel drugs targeting this hormone-regulated transcription factor, such as enzalutamide – a potent androgen receptor antagonist. Despite the plethora of possible treatment options, the absolute survival benefit of each treatment separately is limited to a few months. Therefore, current research efforts are directed to determine the optimal sequence of therapies, discover novel drugs effective in metastatic castration-resistant prostate cancer and define patient subpopulations that ultimately benefit from these treatments. Molecular studies provide evidence on which pathways mediate treatment resistance and may lead to improved treatment for metastatic castration-resistant prostate cancer. This review provides, firstly a concise overview of the clinical development, use and effectiveness of enzalutamide in the treatment of advanced prostate cancer, secondly it describes translational research addressing enzalutamide response vs resistance and lastly highlights novel potential treatment strategies in the enzalutamide-resistant setting.

Precision medicine applications in prostate cancer

Aided by developments in diagnostics and therapeutics, healthcare is increasingly moving toward precision medicine, in which treatment is customized to each individual. We discuss the relevance of precision medicine in prostate cancer, including gene targets, therapeutics and resistance mechanisms. We foresee precision medicine becoming an integral component of prostate cancer management to increase response to therapy and prolong survival.

Intra versus Inter Cross-resistance Determines Treatment Sequence between Taxane and AR-Targeting Therapies in Advanced Prostate Cancer

Current treatments for castration resistant prostate cancer (CRPC) largely fall into two classes: androgen receptor (AR)-targeted therapies such as the next-generation antiandrogen therapies (NGAT), enzalutamide and abiraterone, and taxanes such as docetaxel and cabazitaxel. Despite improvements in outcomes, patients still succumb to the disease due to the development of resistance. Further complicating the situation is lack of a well-defined treatment sequence and potential for cross-resistance between therapies. We have developed several models representing CRPC with acquired therapeutic resistance. Here, we utilized these models to assess putative cross-resistance between treatments. We find that resistance to enzalutamide induces resistance to abiraterone and vice versa, but resistance to neither alters sensitivity to taxanes. Acquired resistance to docetaxel induces cross-resistance to cabazitaxel but not to enzalutamide or abiraterone. Correlating responses with known mechanisms of resistance indicates that AR variants are associated with resistance to NGATs, whereas the membrane efflux protein ABCB1 is associated with taxane resistance. Mechanistic studies show that AR variant-7 (AR-v7) is involved in NGAT resistance but not resistance to taxanes. Our findings suggest the existence of intra cross-resistance within a drug class (i.e., within NGATs or within taxanes), whereas inter cross-resistance between drug classes does not develop. Furthermore, our data suggest that resistance mechanisms differ between drug classes. These results may have clinical implications by showing that treatments of one class can be sequenced with those of another, but caution should be taken when sequencing similar classed drugs. In addition, the development and use of biomarkers indicating resistance will improve patient stratification for treatment. Mol Cancer Ther; 17(10); 2197-205. ©2018 AACR.

Sequencing of Taxanes and New Androgen-targeted Therapies in Metastatic Castration-resistant Prostate Cancer: Results of the International Multicentre Retrospective CATS Database

BACKGROUND

The optimal sequence of life-extending therapies in metastatic castration-resistant prostate cancer (mCRPC) is unknown.

OBJECTIVE

To evaluate outcomes among mCRPC patients treated with docetaxel (DOC), cabazitaxel (CABA), and a novel androgen receptor-targeted agent (ART; abiraterone acetate or enzalutamide) according to three different sequences.

DESIGN, SETTING, AND PARTICIPANTS

Data from 669 consecutive mCRPC patients were retrospectively collected between November 2012 and October 2016.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was the prostate-specific antigen (PSA) response (decrease ≥50% from baseline) to each therapy. Secondary endpoints included best clinical benefit, time to PSA progression, radiological progression-free survival (rPFS), overall survival (OS), and toxicity.

RESULTS AND LIMITATIONS

A total of 158 patients received DOC→CABA→ART (group 1), 456 received DOC→ART→CABA (group 2), and 55 received ART→DOC→CABA (group 3). At baseline, PSA progression only and Gleason <8 were more common in group 3. PSA response on DOC was lower in group 3 than in other groups (p=0.02) and PSA response on CABA was higher in the second than in the third line (p=0.001). In Group 3, rPFS on ART (6.6 mo) and DOC (9.2 mo) was also shorter than in the other groups. OS calculated from the first life-extending therapy reached 34.8, 35.8, and 28.9 mo in groups 1, 2 and 3, respectively (p=0.007). Toxicity was comparable between the arms. The main limitations of the trial are its retrospective design and the low number of patients in group 3.

CONCLUSIONS

In this retrospective trial, sequencing of DOC, CABA, and one ART, was associated with median OS of up to 35.8 mo. CABA seemed to retain its activity regardless of treatment sequence. DOC activity after ART appeared to be reduced, but the data are insufficient to conclude that cross-resistance occurs.

PATIENT SUMMARY

The order of drugs administered to patients with metastatic castration-resistant prostate cancer could impact their efficacy, with cabazitaxel appearing to retain its activity whatever the therapeutic sequence.

Baseline prostate-specific antigen levels following treatment with abiraterone acetate as a prognostic factor in castration-resistant prostate cancer

The aim of the present study was to investigate the prognostic factors associated with progression-free survival (PFS) and overall survival (OS) times in patients with castration-resistant prostate cancer (CRPC) who received treatment with abiraterone acetate (AA) in routine clinical settings. A total of 93 patients treated with AA between September 2014 and February 2017 were selected and their medical records were analyzed retrospectively. The median PFS time of docetaxel (DTX)-naïve patients was 171 days, and that of post-DTX patients was 56 days. The OS time of DTX-naïve patients did not reach the median. The median OS time of post-DTX patients was 761 days. Multivariate analyses identified baseline prostate-specific antigen (PSA) level prior to treatment with AA and the PSA response rate as independent prognostic factors for PFS time, and baseline PSA prior to treatment with AA as the only independent prognostic factor for OS time. The results of the present study indicate that the baseline PSA level prior to treatment with AA is a notable prognostic factor in patients with CRPC.

HepaCAM inhibits the malignant behavior of castration-resistant prostate cancer cells by downregulating Notch signaling and PF-3084014 (a γ-secretase inhibitor) partly reverses the resistance of refractory prostate cancer to docetaxel and enzalutamide in vitro

Castration-resistant prostate cancer (CRPC) continues to be a major challenge in the treatment of prostate cancer (PCa). The expression of hepatocyte cell adhesion molecule (HepaCAM), a novel tumor suppressor, is frequently downregulated or lost in PCa. Overactivated Notch signaling is involved in the development and progression of PCa, including CRPC. In this study, we found that the activities of Notch signaling were elevated, while HepaCAM expression was decreased in CRPC tissues compared with matched primary prostate cancer (PPC) tissues. In addition, HepaCAM negativity was found to be associated with a worse progression-free survival (PFS). Furthermore, the overexpression of HepaCAM induced by transfection with a HepaCAM overexpression vector (Ad-HepaCAM) exerted antitumor effects by decreasing the proliferation, and suppressing the invasion and migration of bicalutamide-resistant (Bica-R) cells and enzalutamide-resistant (Enza-R) cells. Importantly, we found that the antitumor effects of HepaCAM on the resistant cells were associated with the downregulation of Notch signaling. Moreover, we revealed that PF-3084014 (a γ-secretase inhibitor) re-sensitized Enza-R cells to enzalutamide, and sequential dual-resistant (E+D-R) cells to docetaxel. Additionally, the findings of this study demonstrated that the use of PF-3084014 alone exerted potent antitumor effect on the resistant cells in vitro. On the whole, this study indicates that HepaCAM potentially represents a therapeutic target and PF-3084014 may prove to a promising agent for use in the treatment of refractory PCa.

Optimizing the treatment of metastatic castration-resistant prostate cancer: a Latin America perspective

Prostate cancer is a significant burden and cause of mortality in Latin America. This article reviews the treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC) and provides consensus recommendations to assist Latin American prostate cancer specialists with clinical decision making. A multidisciplinary expert panel from Latin America reviewed the available data and their individual experience to develop clinical consensus opinions for the use of life-prolonging agents in mCRPC, with consideration given to factors influencing patient selection and treatment monitoring. There is a lack of level 1 evidence for the best treatment sequence or combinations in mCRPC. In this context, consensus recommendations were provided for the use of taxane-based chemotherapies, androgen receptor axis-targeted agents and targeted alpha therapy, for patients in Latin America. Prostate-specific antigen (PSA) changes alone, during treatment, should be treated with caution; PSA may not be a suitable biomarker for radium-223. Bone scans and computed tomography are the standard imaging modalities in Latin America. Imaging should be prompted during treatment where symptomatic decline and/or significant worsening of laboratory evaluations are reported, or where a course of therapy has been completed and another antineoplastic agent is under consideration. Recommendations and guidance for treatment options in Latin America are provided in the context of country-level variable access to approved agents and technologies for treatment monitoring. Patients should be treated with the purpose of prolonging overall survival and preserving quality of life through increasing the opportunity to administer all available life-prolonging therapies when appropriate.

Systemic immune-inflammation index predicts the combined clinical outcome after sequential therapy with abiraterone and docetaxel for metastatic castration-resistant prostate cancer patients

OBJECTIVE

To compare the antitumor effect of abiraterone (AA) followed by docetaxel-prednisone (DP) or vice versa in metastatic castration-resistant prostate cancer (mCRPC) patients, and explored factors that might predict combined PSA-PFS, combined rPFS and OS.

PATIENTS AND METHODS

We retrospectively analyzed mCRPC patients treated with sequential therapy using DP followed by AA or vice versa. Patients who had received enzalutamide or cabazitaxel were excluded. The primary outcome measure was overall survival (OS). The combined PSA progression-free survival (PSA-PFS), combined radiographic PFS (rPFS), and OS of AA-to-DP were compared to the reverse sequence using Kaplan-Meier curves with log-rank statistics. Univariable and multivariable Cox regression analyses were performed to determine prognostic factors that were associated with combined PSA-PFS, combined rPFS and OS.

RESULTS

A total of 104 mCRPC patients who began treatment between 2013 and 2017 were identified: 42 were in the DP-to-AA group and 62 were in the AA-to-DP group. There was no significant difference of baseline clinical characteristics between AA-to-DP and DP-to-AA group. In addition, there was no significant difference in combined PSA-PFS (AA-to-DP: 12.5 [11.4-13.6] vs DP-to-AA: 13.2 [10.9-15.5] months [P = 0.127]), combined rPFS (AA-to-DP: 12.2 [10.9-13.4] vs DP-to-AA: 11.2 [8.9-13.5] months [P = 0.183]) and OS (AA-to-DP: 23.3 [19.7-26.9] vs DP-to-AA: 22.9 [22.1-23.7] months [P = 0.213]) between the two treatment sequences in Kaplan-Meier analysis. In multivariate Cox regression analysis, high systematic Immune-Inflammation Index (SII) level, which was calculated by P (platelet) × N (neutrophil)/L(lymphocyte), remained significant predictors of OS, combined rPFS and combined PSA-PFS.

CONCLUSION

In this study, we did not observe differences in clinical outcomes based on alternative sequencing of AA and DP in mCRPC patients. The ability to tolerate side effects and patient preference may be used to determine the treatment sequencing. In addition, high pretreatment SII level is a negative independent prognosticator of survival outcomes in mCRPC with sequential therapy using DP followed by AA or vice versa, which might guide clinicians select the best treatment.

Abiraterone acetate and its use in the treatment of metastatic prostate cancer: a review

Abiraterone acetate, which targets enzymatic complexes playing a central role in steroidogenesis, demonstrated to increase survival significantly in both chemo-naive and docetaxel pretreated, becoming one of the drugs of choice for metastatic castration-resistant prostate cancer. More recently, this agent in combination to androgen deprivation therapy demonstrated to be efficacious also in metastatic castration-sensitive prostate cancer. The present review is aimed to outline the clinical development of abiraterone acetate, the pivotal trials which led to its approval for the clinical practice, new evidence about its efficacy in metastatic castration-sensitive prostate cancer, its place in the therapeutic landscape of prostate cancer and future directions of development.