First-line combination treatment with PARP and androgen receptor-signaling inhibitors in HRR-deficient mCRPC: Applying clinical study findings to clinical practice in the United States

INTRODUCTION

Metastatic castration-resistant prostate cancer (mCRPC) remains incurable and develops from biochemically recurrent PC treated with androgen deprivation therapy (ADT) following definitive therapy for localized PC, or from metastatic castration-sensitive PC (mCSPC). In the mCSPC setting, treatment intensification of ADT plus androgen receptor (AR)-signaling inhibitors (ARSIs), with or without chemotherapy, improves outcomes vs ADT alone. Despite multiple phase 3 trials demonstrating a survival benefit of treatment intensification in PC, there remains high use of ADT monotherapy in real-world clinical practice. Prior studies indicate that co-inhibition of AR and poly(ADP-ribose) polymerase (PARP) may result in enhanced benefit in treating tumors regardless of alterations in DNA damage response genes involved either directly or indirectly in homologous recombination repair (HRR). Three recent phase 3 studies evaluated the combination of a PARP inhibitor (PARPi) with an ARSI as first-line treatment for mCRPC: TALAPRO-2, talazoparib plus enzalutamide; PROpel, olaparib plus abiraterone acetate and prednisone (AAP); and MAGNITUDE, niraparib plus AAP. Results from these studies have led to the recent approval in the United States of talazoparib plus enzalutamide for the treatment of mCRPC with any HRR alteration, and of both olaparib and niraparib indicated in combination with AAP for the treatment of mCRPC with BRCA alterations.

SUMMARY

Here, we review the newly approved PARPi plus ARSI treatments within the context of the mCRPC treatment landscape, provide an overview of practical considerations for the combinations in clinical practice, highlight the importance of HRR testing, and discuss the benefits of treatment intensification for patients with mCRPC.

First-line talazoparib with enzalutamide in HRR-deficient metastatic castration-resistant prostate cancer: the phase 3 TALAPRO-2 trial

Preclinical evidence has suggested an interplay between the androgen receptor, which largely drives the growth of prostate cancer cells, and poly(ADP-ribose) polymerase. This association provides a rationale for their co-inhibition for the treatment of metastatic castration-resistant prostate cancer (mCRPC), an area of unmet medical need. The phase 3 TALAPRO-2 study investigated combining the poly(ADP-ribose) polymerase inhibitor talazoparib with enzalutamide versus enzalutamide alone as first-line treatment of mCRPC. Patients were prospectively assessed for tumor alterations in DNA damage response genes involved in homologous recombination repair (HRR). Two cohorts were enrolled sequentially: an all-comers cohort that was enrolled first (cohort 1; N = 805 (169 were HRR-deficient)), followed by an HRR-deficient-only cohort (cohort 2; N = 230). We present results from the alpha-controlled primary analysis for the combined HRR-deficient population (N = 399). Patients were randomized in a 1:1 ratio to talazoparib or placebo, plus enzalutamide. The primary endpoint, radiographic progression-free survival, was met (median not reached at the time of the analysis for the talazoparib group versus 13.8 months for the placebo group; hazard ratio, 0.45; 95% confidence interval, 0.33 to 0.61; P < 0.0001). Data for overall survival, a key secondary endpoint, are immature but favor talazoparib (hazard ratio, 0.69; 95% confidence interval, 0.46 to 1.03; P = 0.07). Common adverse events in the talazoparib group were anemia, fatigue and neutropenia. Combining talazoparib with enzalutamide significantly improved radiographic progression-free survival in patients with mCRPC harboring HRR gene alterations, supporting talazoparib plus enzalutamide as a potential first-line treatment for these patients. ClinicalTrials.gov Identifier: NCT03395197 .

Talazoparib plus enzalutamide in men with first-line metastatic castration-resistant prostate cancer (TALAPRO-2): a randomised, placebo-controlled, phase 3 trial

BACKGROUND

Co-inhibition of poly(ADP-ribose) polymerase (PARP) and androgen receptor activity might result in antitumour efficacy irrespective of alterations in DNA damage repair genes involved in homologous recombination repair (HRR). We aimed to compare the efficacy and safety of talazoparib (a PARP inhibitor) plus enzalutamide (an androgen receptor blocker) versus enzalutamide alone in patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

TALAPRO-2 is a randomised, double-blind, phase 3 trial of talazoparib plus enzalutamide versus placebo plus enzalutamide as first-line therapy in men (age ≥18 years [≥20 years in Japan]) with asymptomatic or mildly symptomatic mCRPC receiving ongoing androgen deprivation therapy. Patients were enrolled from 223 hospitals, cancer centres, and medical centres in 26 countries in North America, Europe, Israel, South America, South Africa, and the Asia-Pacific region. Patients were prospectively assessed for HRR gene alterations in tumour tissue and randomly assigned (1:1) to talazoparib 0·5 mg or placebo, plus enzalutamide 160 mg, administered orally once daily. Randomisation was stratified by HRR gene alteration status (deficient vs non-deficient or unknown) and previous treatment with life-prolonging therapy (docetaxel or abiraterone, or both: yes vs no) in the castration-sensitive setting. The sponsor, patients, and investigators were masked to talazoparib or placebo, while enzalutamide was open-label. The primary endpoint was radiographic progression-free survival (rPFS) by blinded independent central review, evaluated in the intention-to-treat population. Safety was evaluated in all patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov (NCT03395197) and is ongoing.

FINDINGS

Between Jan 7, 2019, and Sept 17, 2020, 805 patients were enrolled and randomly assigned (402 to the talazoparib group and 403 to the placebo group). Median follow-up for rPFS was 24·9 months (IQR 21·9-30·2) for the talazoparib group and 24·6 months (14·4-30·2) for the placebo group. At the planned primary analysis, median rPFS was not reached (95% CI 27·5 months-not reached) for talazoparib plus enzalutamide and 21·9 months (16·6-25·1) for placebo plus enzalutamide (hazard ratio 0·63; 95% CI 0·51-0·78; p<0·0001). In the talazoparib group, the most common treatment-emergent adverse events were anaemia, neutropenia, and fatigue; the most common grade 3-4 event was anaemia (185 [46%] of 398 patients), which improved after dose reduction, and only 33 (8%) of 398 patients discontinued talazoparib due to anaemia. Treatment-related deaths occurred in no patients in the talazoparib group and two patients (<1%) in the placebo group.

INTERPRETATION

Talazoparib plus enzalutamide resulted in clinically meaningful and statistically significant improvement in rPFS versus standard of care enzalutamide as first-line treatment for patients with mCRPC. Final overall survival data and additional long-term safety follow-up will further clarify the clinical benefit of the treatment combination in patients with and without tumour HRR gene alterations.

FUNDING

Pfizer.

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

BACKGROUND

Androgen deprivation therapy (ADT), a cornerstone of prostate cancer treatment, is commonly co-prescribed as combination therapy.

OBJECTIVE

To better understand the safety and tolerability profile of relugolix, an oral non-peptide gonadotropin-releasing hormone (GnRH) receptor antagonist, in combination with abiraterone acetate (abiraterone) and apalutamide, a phase I study was undertaken.

PATIENTS AND METHODS

This is an ongoing, 52-week, open-label, parallel cohort study of relugolix in combination with abiraterone in men with metastatic castration-sensitive prostate cancer (mCSPC) or metastatic castration-resistant prostate cancer (mCRPC) [Part 1] and apalutamide in men with mCSPC or non-metastatic castration-resistant prostate cancer (nmCRPC) [Part 2]. Eligible patients treated with leuprolide acetate or degarelix with abiraterone or apalutamide prior to baseline, at which time they were transitioned to relugolix. Assessments included reporting of adverse events, clinical laboratory tests, vital sign measurements, electrocardiogram (ECG) parameters, and testosterone serum concentrations. In this interim report, patients completing ≥12 weeks were included.

RESULTS

Overall, 15 men were enrolled in Part 1 and 10 in Part 2. Adverse events were mostly mild-to-moderate in intensity and were consistent with the known safety profiles of the individual medications. No transition (from prior ADT treatment)- or time-related trends in clinical laboratory tests, vital sign measurements, or ECG parameters were observed. Mean testosterone concentrations remained below castration levels.

CONCLUSIONS

Combination therapy of relugolix and abiraterone or apalutamide was associated with a favorable safety and tolerability profile consistent with the known profiles of the individual medications. Castration levels of testosterone were maintained after transitioning to relugolix from other ADTs.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04666129.

TALAPRO-2: Phase 3 study of talazoparib (TALA) + enzalutamide (ENZA) versus placebo (PBO) + ENZA as first-line (1L) treatment in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

LBA17

Background: TALAPRO-2 (NCT03395197) is the first phase 3 study to combine the poly(ADP-ribose) polymerase inhibitor TALA with the androgen receptor inhibitor ENZA. Pts unselected for genetic alterations in DNA damage repair pathways, directly or indirectly involved with homologous recombination repair (HRR), received either TALA + ENZA or PBO + ENZA as 1L treatment for mCRPC. Methods: Pts randomized 1:1 to TALA 0.5 mg or PBO (all pts received ENZA 160 mg daily) were stratified by prior abiraterone or docetaxel for castration-sensitive PC and HRR gene alteration status. Key eligibility criteria: mildly or asymptomatic mCRPC with disease progression at study entry, ECOG PS ≤1, ongoing androgen deprivation therapy, no prior life-prolonging therapy for CRPC. Primary endpoint: imaging-based progression-free survival (ibPFS) by BICR per RECIST 1.1 and PCWG3. Results: 402 pts were randomized to receive TALA + ENZA and 403 PBO + ENZA. Of these 805 pts, enrollment was informed by tumor tissue for 804 (99.9%), by tumor tissue and blood for 114 (14.2%), and by blood only for 1 (0.1%). Median ibPFS by BICR was significantly improved in the TALA + ENZA vs PBO + ENZA arm (not reached vs 21.9 months, respectively; HR, 0.63; 95% CI, 0.51–0.78; P< 0.001). ibPFS was significantly improved in HRR-deficient (HR, 0.46; 95% CI, 0.30–0.70; P< 0.001), HRR-non-deficient or unknown (HR, 0.70; 95% CI, 0.54–0.89; P= 0.004), and HRR-non-deficient pts by tumor tissue testing (HR, 0.66; 95% CI, 0.49–0.91; P= 0.009) in the TALA + ENZA vs PBO + ENZA arm. Overall survival data are immature; 30.6% (TALA) and 32.0% (PBO) pts had died; HR (0.89 [95% CI, 0.69–1.14; P= 0.35]) favored the TALA + ENZA arm. Objective response rates, PSA response ≥50%, and time to PSA progression and use of subsequent cytotoxic chemotherapy and antineoplastic therapy significantly favored the TALA + ENZA vs PBO + ENZA arm. In pts, 71.9% (TALA + ENZA) and 40.6% (PBO + ENZA) had grade 3-4 treatment-emergent adverse events (TEAEs). The most common grade ≥3 TEAEs were anemia, low neutrophil, and low platelet counts (TALA + ENZA), and hypertension, anemia, and fatigue (PBO + ENZA). TEAEs led to discontinuation of TALA in 19.1% of pts (vs PBO in 12.2%). Discontinuation rates of ENZA were 10.8% in the TALA + ENZA vs 11.0% in PBO + ENZA arm. Median time to definitive clinically meaningful deterioration in global health status/quality of life (GHS/QoL) was significantly longer with TALA + ENZA vs PBO + ENZA (30.8 vs 25.0 months, respectively; HR, 0.78; 95% CI, 0.62–0.99; P= 0.04). Conclusions: TALA + ENZA demonstrated statistically significant and clinically meaningful improvement in ibPFS over standard of care ENZA as 1L treatment in pts with mCRPC regardless of HRR status, while delaying time to worsening in GHS/QoL. There were no new safety signals; toxicity was generally manageable. Clinical trial information: NCT03395197 .

Plain language summary of the design of the TALAPRO-2 study comparing talazoparib and enzalutamide versus enzalutamide and placebo in men with metastatic castration-resistant prostate cancer

WHAT IS THIS SUMMARY ABOUT?

This summary describes the design of an ongoing research study (also known as a clinical trial) called TALAPRO-2. The TALAPRO-2 trial is testing the combination of two medicines called talazoparib and enzalutamide as a first treatment in adult men with metastatic castration-resistant prostate cancer. The study began in December 2017 and has enrolled 1037 adult men with metastatic castration-resistant prostate cancer from 26 countries.

WHAT IS METASTATIC CASTRATION-RESISTANT PROSTATE CANCER?

Metastatic castration-resistant prostate cancer is a type of cancer that has advanced beyond the prostate and continues to grow even when testosterone levels in the blood are suppressed.

WHICH MEDICINES ARE BEING TESTED?

The combination of talazoparib plus enzalutamide will be compared with enzalutamide plus placebo. Enzalutamide is approved to treat men with prostate cancer. Talazoparib is not approved to treat men with prostate cancer. A placebo does not contain any active ingredients and is also known as a sugar pill.

WHAT ARE THE AIMS OF THE TALAPRO-2 TRIAL?

The TALAPRO-2 trial will find out if combining talazoparib with enzalutamide increases the length of time the men in the study live without their cancer getting worse compared with enzalutamide plus placebo. The study will also measure how long men in the study live and any side effects the men have while they are taking the study medicines. Researchers are also testing the DNA from the tumor cells of all men in the study to find out if they have faulty DNA repair genes. Clinical Trial Registration: NCT0339519 (ClinicalTrials.gov).

Relugolix in combination with abiraterone acetate, apalutamide, or docetaxel in men with advanced prostate cancer (aPC): A phase 1, three-part, open-label, parallel-cohort study

TPS207

Background: Androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) analogs or receptor antagonists is a cornerstone of prostate cancer treatment. As disease progresses, agents with complementary mechansims are co-prescribed with ADT to suppress extra-testicular testosterone production or block androgen receptors on cancer cells. Relugolix (120 mg) is an oral non-peptide GnRH receptor antagonist approved in the US for the treatment of aPC. In the phase 3 study, relugolix maintained suppression of testosterone to castration levels in 96.7% of men for up to 48 weeks (wks), with superiority to leuprolide acetate. Relugolix was well tolerated and associated with a 54% lower risk of major adverse cardiovascular events relative to leuprolide acetate (Shore N, NEJM 2020;382;23). To formally assess the safety and tolerability of combination treatment with relugolix, a phase 1 study in men with aPC has been undertaken. Methods: This is a three-part, open-label, parallel-cohort safety and tolerability study of relugolix in combination with abiraterone acetate in men with metastatic castration-sensitive prostate cancer (mCSPC) or metastatic castration-resistant prostate cancer (mCRPC) (Part 1), apalutamide in men with mCSPC or non-metastatic catration-resistant prostate cancer (nmCRPC) (Part 2), or docetaxel in men with mCSPC or mCRPC (Part 3). Each part of the study consists of a 45-day screening period, a 12-wk primary study treatment period and a 40-wk safety extension treatment period. All of the men are required to have been treated with leuprolide acetate or a GnRH receptor antagonist (eg, degarelix) in combination with abiraterone acetate for a minimum of 12 wks, apalutamide for a minimum of 6 wks, or docetaxel for a minimum of one treatment cycle prior to the baseline (Day 1) visit. Men will be transitioned from leuprolide acetate or degarelix to relugolix (120 mg [Part 1 and 3] or 240 mg [Part 2] once daily after a single loading dose of 360 mg); on the approximate date the next analog or antagonist injection is scheduled; treatment with each combination treatment will continue as previously prescribed. Hence, the study will provide safety and tolerability of relugolix and the three different combination agents for up to 1 year and in addition, will provide safety and tolerability data as men transition from injectable leuprolide acetate or degarelix to oral treatment with relugolix. Enrollment into the study began in March 2021. A protocol amendment was approved in July 2021 to include Part 2 and Part 3 of the study and to add the 40-wk safety extension treatment period. Screening for Part 2 was initiated in August 2021 and for Part 3 it is expected to initiate in January 2022. Clinical trial information: NCT04666129.

Talazoparib plus enzalutamide in metastatic castration-resistant prostate cancer: TALAPRO-2 Phase III study design

PARP inhibitors in combination with androgen receptor-targeted therapy have demonstrated potential in the treatment of metastatic castration-resistant prostate cancer (mCRPC). Here, we describe the design and rationale of the multinational, Phase III, two-part TALAPRO-2 study comparing talazoparib plus enzalutamide versus placebo plus enzalutamide as a first-line treatment for patients with mCRPC with or without DNA damage response (DDR) alterations. This study has two co-primary end points: radiographic progression-free survival (rPFS) by blinded independent clinical review in all-comers (Cohort 1) and in patients with DDR alterations (Cohort 2). TALAPRO-2 will demonstrate whether talazoparib plus enzalutamide can significantly improve the efficacy of enzalutamide in terms of rPFS in both molecularly unselected and DDR-deficient patients with mCRPC (NCT03395197). Clinical Trial Registration: NCT03395197 (ClinicalTrials.gov).

TALAPRO-2: A phase 3 randomized study of enzalutamide (ENZA) plus talazoparib (TALA) versus placebo in patients with new metastatic castration-resistant prostate cancer (mCRPC)

TPS5089

Background: TALA blocks poly(ADP-ribose) polymerase (PARP) activity and traps PARP on single-strand DNA breaks, preventing DNA damage repair (DDR) and causing death of cells with DDR alterations (eg, BRCA1/2).a TALA is approved in multiple countries as monotherapy for germline BRCA1/2-mutated human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Olaparib and rucaparib are PARP inhibitors approved for use in mCRPC. ENZA is an androgen receptor (AR) inhibitor and an established therapy for mCRPC. As PARP activity has been shown to support AR function, inhibition of PARP is expected to increase sensitivity to AR-directed therapies. In addition, AR blockade downregulates homologous recombination repair gene transcription, which induces a “ BRCAness” phenotype. A proof-of-concept study combining olaparib and abiraterone (abi) in pts with mCRPC demonstrated improved median radiographic progression-free survival (rPFS) vs placebo plus abi (13.8 vs 8.2 months) and a tolerable safety profile. Therefore, ENZA may be efficacious regardless of DDR alterations. TALAPRO-2 (NCT03395197) is a Phase 3, 2-part study evaluating the efficacy, safety, pharmacokinetics, and patient-reported outcomes (PROs) of TALA plus ENZA in pts with mCRPC with or without DDR alterations. Methods: Enrollment goal is 1037 patients (pts; 19 pts, part 1 dose-finding [completed]; 1018 pts, part 2 placebo-controlled [ongoing; accrual completed in unselected cohort]). Key eligibility criteria: age ≥18 years; asymptomatic/mildly symptomatic mCRPC; ECOG performance status ≤1; metastatic disease (no brain metastases); and no prior life-prolonging systemic therapy for nonmetastatic CRPC or mCRPC. Prior therapies (excluding novel AR inhibitors) in the castration-sensitive (CSPC) setting are allowed. ADT must continue throughout the study. The randomized double-blind portion (part 2) will evaluate safety, efficacy, and PROs of TALA (0.5 mg once daily [QD]) + ENZA (160 mg QD) vs placebo + ENZA (160 mg QD). Pts are stratified by prior novel hormonal therapy or docetaxel for CSPC or mCSPC (yes or no) and DDR alteration status (deficient vs nondeficient/unknown). The primary endpoint is rPFS, defined as time to progression in soft tissue per RECIST v.1.1 or in bone per PCWG3 criteria by independent central review or death. The key secondary endpoint is overall survival. Efficacy is assessed radiographically every 8 weeks up to Week 25 and every 8–12 weeks thereafter. rPFS will be compared between the two arms by a one-sided stratified log-rank test. Pt recruitment is ongoing at 223 sites in 26 countries, including 32 states across the US, and Europe, Israel, South America, South Africa, and Asia-Pacific region. aDDR alterations are defined as known/likely pathogenic variants or homozygous deletions. Clinical trial information: NCT03395197.

Optimizing the management of castration-resistant prostate cancer patients: A practical guide for clinicians

BACKGROUND

Advanced prostate cancer (PC) patients, especially those with metastatic prostate cancer (mPC), often require complex management pathways. Despite the publication of clinical practice guidelines by leading urological and oncological organizations that provide a substantial and comprehensive framework, there are numerous clinical scenarios that are not always addressed, especially as new treatments become available, new imaging modalities are developed, and advances in genetic testing continue.

METHODS

A 14-member expert review panel comprised of urologists and medical oncologists were chosen to provide guidance on addressing specific topics and issues regarding metastatic castration-resistant prostate cancer (mCRPC) patients. Panel members were chosen based upon their experience and expertise in the management of PC patients. Four academic members (two urologists and two medical oncologists) of the panel served as group leaders; the remaining eight panel members were from Large Urology Group Practice Association (LUGPA) practices with proven experience in leading their advanced PC clinics. The panel members were assigned to four separate working groups, each assigned a specific mCRPC topic to review and discuss with the entire panel.

RESULTS

This article describes the practical recommendations of an expert panel on the management of mCRPC patients. The target reading audience for this publication is all providers (urologists, medical oncologists, radiation oncologists, or advanced practice providers) who evaluate and manage advanced PC patients, regardless of their practice setting.

CONCLUSION

The panel has provided recommendations for managing mCRPC with regard to specific issues: (a) biomarker monitoring and the role of genetic and molecular testing; (b) rationale, current strategies, and optimal sequencing of the various approved therapies, including hormonal therapy, cytotoxic chemotherapy, radiopharmaceuticals and immunotherapy; (c) adverse event management and monitoring; and (d) imaging advanced PC patients. These recommendations seek to complement national guidelines, not replace them, and a discussion of where the panel agreed or disagreed with national guidelines is included.

TALAPRO-2: a placebo-controlled phase III study of talazoparib (TALA) plus enzalutamide (ENZA) for patients with first-line metastatic castration-resistant prostate cancer (mCRPC)

TPS5598

Background: TALA blocks poly(ADP-ribose) polymerase (PARP) activity and traps PARP on single-strand DNA breaks, preventing DNA damage repair (DDR) and causing death of cells with DDR alterations (eg BRCA1/2).a TALA has been approved in multiple countries as monotherapy for germline BRCA1/2-mutated human epidermal growth factor receptor 2-negative advanced breast cancer. ENZA is an androgen receptor (AR) inhibitor and an established therapy for mCRPC. As PARP activity has been shown to support AR function, inhibition of PARP is expected to reduce AR signaling and increase sensitivity to AR-directed therapies. In addition, AR blockade downregulates homologous recombination repair gene transcription which induces ‘ BRCAness ’. Therefore, combining TALA with ENZA in mCRPC may be efficacious regardless of DDR alterations. TALAPRO-2 (NCT03395197) is a Phase III, 2-part study to evaluate efficacy, safety, pharmacokinetics, and patient-reported outcomes (PROs) of TALA combined with ENZA. Methods: Enrollment goal is 1037 patients (19 patients, part 1 dose-finding; 1,018 patients, part 2 placebo-controlled). Key eligibility criteria: age ≥18 years; asymptomatic/mildly symptomatic mCRPC; ECOG performance status ≤1; metastatic disease (no brain metastases); and no prior life-prolonging systemic therapy for nonmetastatic CRPC or mCRPC. Prior therapies (excluding novel AR inhibitors) in the castration-sensitive (CSPC) setting are allowed. ADT must continue throughout the study. The randomized double-blind portion (part 2) will evaluate safety, efficacy, and PROs of TALA (0.5 mg QD) + ENZA (160 mg QD) vs placebo + ENZA (160 mg QD). Patients are stratified by prior novel hormonal therapy or docetaxel for CSPC (yes or no) and DDR alteration status (deficient vs nondeficient/unknown). The primary endpoint is radiographic progression-free survival (rPFS), defined as time to progression in soft tissue per RECIST v.1.1 or in bone per PCWG3 criteria by independent review or death. The key secondary endpoint is overall survival. Efficacy will be assessed radiographically every 8 weeks up to Week 25 and every 8–12 weeks thereafter. rPFS will be compared between the two arms by a 1-sided stratified log-rank test. Patient recruitment is ongoing in multiple regions including US, Europe/Eastern Europe, Israel, South America, South Africa, and Asia-Pacific region. aDDR alterations are defined as known/likely pathogenic variants or homozygous deletions. Funding: Pfizer Inc. Clinical trial information: NCT03395197 .

Effect of Enzalutamide plus Androgen Deprivation Therapy on Health-related Quality of Life in Patients with Metastatic Hormone-sensitive Prostate Cancer: An Analysis of the ARCHES Randomised, Placebo-controlled, Phase 3 Study

BACKGROUND

In the ARCHES study in metastatic hormone-sensitive prostate cancer (mHSPC), enzalutamide plus androgen deprivation therapy (ADT) improved radiographic progression-free survival (rPFS) versus ADT alone.

OBJECTIVE

To evaluate patient-reported outcomes (PROs) to week 73.

DESIGN, SETTING, AND PARTICIPANTS

ARCHES (NCT02677896) was a randomised, double-blind, placebo-controlled, phase 3 study in mHSPC patients.

INTERVENTION

Enzalutamide (160 mg/day) plus ADT or placebo plus ADT.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

PROs were assessed at baseline, week 13, and every 12 wk until disease progression using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Prostate 25 (QLQ-PR25), Functional Assessment of Cancer Therapy-Prostate (FACT-P), Brief Pain Inventory Short Form, and EuroQoL 5-Dimensions, 5-Levels (EQ-5D-5 L) instruments. Endpoints included time to first (TTFD) and first confirmed (TTFCD) clinically meaningful deterioration (using predefined questionnaire thresholds) in health-related quality of life (HRQoL) and pain.

RESULTS AND LIMITATIONS

A total of 1150 patients received ADT plus enzalutamide (n = 574) or placebo (n = 576). Baseline PRO scores indicated high HRQoL and low pain, which was generally maintained in both groups. There were no statistically significant (nominal p > 0.05) between-group differences that occurred in both TTFD and TTFCD together for QLQ-PR25 and FACT-P scores. Enzalutamide significantly delayed TTFD in worst pain (by ∼3 mo; nominal p = 0.032), pain severity (nominal p = 0.021), and EQ-5D-5 L visual analogue scale score (nominal p = 0.0070) versus placebo (not significant for confirmed deterioration for pain outcomes). Enzalutamide delays deterioration in several HRQoL subscales and pain severity in high-volume disease.

CONCLUSIONS

Enzalutamide plus ADT enables men with mHSPC to maintain high-functioning HRQoL and low symptom burden.

PATIENT SUMMARY

This study examined the effect on health-related quality of life and pain of adding enzalutamide or placebo to androgen deprivation therapy for patients with metastatic hormone-sensitive prostate cancer. Addition of enzalutamide allowed patients to maintain their health-related quality of life.

TALAPRO-2: A placebo-controlled phase III study of talazoparib (TALA) plus enzalutamide (ENZA) for patients with first-line metastatic castration-resistant prostate cancer (mCRPC)

TPS264

Background: TALA is a poly(ADP-ribose) polymerase (PARP) inhibitor that inhibits PARP1/2 and traps PARP on DNA, preventing DNA damage repair (DDR) and causing death of cells with DDR mutations (eg BRCA1/2). TALA is approved in multiple countries for germline BRCA1/2-mutated HER2- advanced breast cancer. ENZA is an established therapy for CRPC. PARP1 activity has been shown to support AR function, suggesting that co-blockade of PARP1 may synergize with AR-directed therapy, regardless of DDR deficiency. A combination of TALA with ENZA in mCRPC may improve clinical outcomes in patients with or without DDR-deficient tumors. TALAPRO-2 (NCT03395197) is a 2-part study to evaluate efficacy, safety, pharmacokinetics, and patient (pt)-reported outcomes (PROs) of the combination. Methods: Enrollment goal is 1037 pts (19 pts, part 1 dose-finding; 1,018 pts, part 2 placebo-controlled). Key eligibility criteria: age ≥18 y, asymptomatic/mildly symptomatic mCRPC, ECOG performance status ≤1, no brain metastases, and no prior life-prolonging systemic therapy in nonmetastatic CRPC or mCRPC state. Prior docetaxel or novel hormonal therapy (excluding novel AR inhibitors) in castration sensitive (CSPC) setting is allowed. The randomized double-blind portion will evaluate safety, efficacy, and PROs of TALA (0.5 mg QD) + ENZA (160 mg QD) vs placebo + ENZA (160 mg QD). Randomization is stratified by prior NHT or docetaxel for CSPC (yes/no) and DDR mutation status (deficient vs nondeficient/unknown). The primary endpoint is radiographic progression-free survival (rPFS), defined as time to progression in soft tissue per RECIST v.1.1 or in bone per PCWG3 criteria or death. The key secondary endpoint is overall survival (OS). Efficacy will be assessed by radiography every 8 weeks up to week 25 and every 8–12 weeks thereafter. rPFS will be compared between two arms by a 1-sided stratified log-rank test. Pt recruitment is ongoing in multiple regions including US, Europe/Eastern Europe, Israel, South America, South Africa, and Asia Pacific region. This study was sponsored by Pfizer Inc. Clinical trial information: NCT03395197.

A phase III randomized, placebo-controlled, double-blind study of niraparib plus abiraterone acetate and prednisone versus abiraterone acetate and prednisone in patients with metastatic prostate cancer (NCT03748641)

TPS257

Background: Preclinical data suggest synergistic antitumor activity when the PARP inhibitor (PARPi) niraparib is combined with the androgen pathway inhibitor abiraterone acetate. (1) The addition of a PARPi to abiraterone acetate plus prednisone (AAP) showed improved radiographic progression-free survival (rPFS) vs AAP alone in patients with mCRPC regardless of DNA repair gene defect (DRD) status. (2) Interim results from a phase 1 study support safety and tolerability of niraparib 200 mg combined with AAP in patients with mCRPC. (3) The objective of this Phase 3 study is to compare the efficacy and safety of niraparib plus AAP versus AAP with placebo as first-line therapy for mCRPC. Methods: This ongoing multicenter MAGNITUDE study will open in 300 sites across 28 countries and will enroll patients with mCRPC who have not received treatment in the metastatic castrate resistant setting other than ongoing androgen deprivation therapy [ADT] and ≤4 months of AAP. The DRD positive cohort (Cohort 1, n=400) will comprise patients whose tumors have DRD, as determined by a previously validated plasma or tissue assay. The cohort without DRD (Cohort 2, n=600) will enroll patients whose tumors are not found to have DRD. Enrollment began in February 2019. The primary objective of the study is to compare radiographic progression-free survival (rPFS) as assessed by blinded independent central radiology review for patients treated with niraparib and AAP versus placebo and AAP. To test superiority of the combination vs AAP, sample sizes were estimated to provide 92% power to detect HR≤0.65 rPFS in the DRD positive cohort and 94% power to detect HR≤0.67 in rPFS in the cohort without DRD, both at a 2-tailed level of significance of 0.05. The main secondary objectives are time to symptomatic progression, time to cytotoxic chemotherapy, and overall survival. Safety and pharmacokinetic profiles will be evaluated.1) Rajendra N, et al. Cancer Res 2019;79 (13 Suppl): Abstract nr 2134. 2) Clarke N, et al. Lancet Oncol. 2018;(7):975-986. 3) Saad, et al. Ann Oncol, 2018;29 (suppl 8), mdy284.043, https://doi.org/10.1093/annonc/mdy284.043 ). Clinical trial information: NCT03748641.

Clinical and safety outcomes of TALAPRO-2: A two-part phase III study of talazoparib (TALA) in combination with enzalutamide (ENZA) in metastatic castration-resistant prostate cancer (mCRPC)

5076

Background: TALA is a dual-mechanism PARP inhibitor that inhibits PARP catalytic activity and traps PARP on DNA. ENZA is a novel hormonal therapy approved to treat castration resistant prostate cancer. TALA + ENZA may improve clinical outcomes for men with mCRPC. However, TALA, is a substrate for efflux drug transporters P-gp and BCRP. Prior to the initiation of TALAPRO-2 part 1, the in vivo effect of ENZA on exposure of P-gp and BCRP substrates, such as TALA, had not been evaluated. Methods: TALAPRO-2 part 1 was designed to determine TALA starting dose based on safety and pharmacokinetics (PK) evaluation of TALA + ENZA. Pts were ≥18 yrs of age, had ECOG PS ≤1, with no prior systemic treatment for mCRPC. The starting dose of TALA in the first 13 pts was 1 mg once daily (QD) + ENZA 160 mg QD (1 mg QD cohort). Based on safety review of prespecified target safety events and PK data, TALA dose was reduced to 0.5 mg QD; additional pts were treated with a starting dose of TALA 0.5 mg QD + ENZA 160 mg QD (0.5 mg QD cohort). Results: 19 pts were enrolled in part 1 (1 mg QD cohort, 13; 0.5 mg QD cohort, 6). The median (range) age was 71 yrs (52-82). As of the analysis cutoff date, the median treatment duration was 25 and 11 wks for the 1 mg QD and 0.5 mg QD cohorts, respectively. Treatment-emergent adverse events (TEAEs) occurred in 19 pts. The most common TEAE, anemia, occurred in 76.9% and 33.3% of pts in the 1 mg QD and 0.5 mg QD cohorts, respectively. TEAEs that led to TALA dose reduction occurred in 6 pts (46.2%) and 0 pts in the 1 mg QD and 0.5 mg QD cohorts, respectively. In the 1 mg QD cohort, target safety events were reported for 7 pts (53.8%) vs 0 in the 0.5 mg QD cohort. 92% and 100% of pts had a 50% decline from baseline in PSA in the 1 mg QD and 0.5 mg cohorts, respectively, demonstrating preliminary anti-tumor activity. PK data showed that ENZA increased TALA exposure and that TALA 0.5 mg QD + ENZA maintained similar TALA exposure to that achieved with 1 mg QD monotherapy. Conclusions: TALA 0.5 mg QD + ENZA 160 mg QD had a manageable safety profile in pts with mCRPC and will be the starting dose for the randomized portion of TALAPRO-2. Clinical trial information: NCT03395197.

TALAPRO-2: Part 2 (P2) of the placebo-controlled phase 3 study of talazoparib (TALA) with enzalutamide (ENZA) in metastatic castration-resistant prostate cancer (mCRPC)

TPS5092

Background: ENZA is approved to treat men with CRPC. TALA is a poly(ADP-ribose) polymerase (PARP) inhibitor that inhibits PARP1/PARP2 and traps PARP on DNA, preventing DNA damage repair (DDR), and causing cell death in BRCA1/2-mutated cells. TALA is approved in the US to treat germline BRCA1/2-mutated HER2- locally advanced/metastatic breast cancer. A combination of TALA with ENZA in mCRPC may improve clinical outcomes. TALAPRO-2 (NCT03395197) is a 2-part study to evaluate the efficacy, safety, pharmacokinetics and (patient) pt-reported outcomes of the combination treatment. The focus here is on P2 of TALAPRO-2. Methods: Approximately 860 pts are planned to be enrolled in P2 from multinational sites. Pts are aged ≥18 years, have asymptomatic/mildly symptomatic mCRPC, Eastern Cooperative Oncology Group performance status ≤1, no brain metastases, and have not received taxanes/novel hormonal therapy (NHT). P2 is a randomized double-blind study that will evaluate safety, efficacy, and pt-reported outcomes of TALA (0.5 mg QD) + ENZA (160 mg QD) vs placebo + ENZA (160 mg QD). Pts will be randomized to 1 of 2 treatment groups: TALA + ENZA, or matching placebo + ENZA. Randomization will be stratified by prior treatment with NHT for castration-sensitive prostate cancer (CSPC) or prior treatment with taxane-based chemotherapy for CSPC (yes/no) and DDR mutation status (deficient vs. nondeficient/unknown). The primary endpoint is radiographic progression-free survival (rPFS), defined as time to progression in soft tissue per RECIST v1.1 or in bone per PCWG3 criteria or death. The key secondary endpoint is overall survival (OS). Efficacy will be assessed by radiography every 8 weeks up to week 25 and every 8-12 weeks thereafter. The analyses of rPFS will be compared between TALA in combination with ENZA and placebo in combination with ENZA by using a 1-sided stratified log-rank test. OS will be evaluated separately in the all comers and the DDR-deficient populations. Pt recruitment is ongoing. Results: n/a. Conclusions: n/a. Clinical trial information: NCT03395197.

Health-related quality of life (HRQoL) and pain progression with enzalutamide (ENZ) in metastatic hormone-sensitive prostate cancer (mHSPC) from the ARCHES study

5044

Background: The Phase 3 ARCHES trial (NCT02677896) evaluated the efficacy and safety of ENZ + androgen deprivation therapy (ADT) vs placebo (PBO) + ADT in 1150 men with mHSPC. Here we report patient-reported outcome (PRO) data using Functional Assessment of Cancer Therapy-Prostate (FACT-P) and Brief Pain Inventory Short Form (BPI-SF). Methods: FACT-P and BPI-SF were assessed at baseline (BL), week (wk) 13, and then every 12 wks until disease progression. Longitudinal changes were assessed using mean scores and mixed-model repeated measures; lower BPI-SF scores represent less pain/interference; higher FACT-P scores represent better HRQoL. Time from BL to first deterioration in PRO score was assessed by Kaplan-Meier estimates and Cox proportional hazards models. Clinically meaningful difference was defined by change from baseline ≥10 for FACT-P total and ≥2 for worst pain/severity. Results: PRO instrument completion rates were high (88−96%) up to wk 73. At BL, men in both arms were generally asymptomatic and reported good HRQoL (FACT-P total: ENZ + ADT, 113.9; PBO + ADT, 112.7) and low pain (worst pain [item 3]: ENZ + ADT, 1.80; PBO + ADT, 1.77). HRQoL and pain scores remained stable over time and there were no clinically meaningful differences between groups in change from BL to wk 73. The proportion of men with no change or improvement in PRO scores (67–88%) was similar in both groups at all time points up to wk 73. There was no significant difference between arms for time to deterioration in FACT-P total (HR 0.90 [95% CI] (0.74, 1.09); p = 0.2998). ENZ + ADT significantly delayed time to pain progression for worst pain (HR 0.82 [0.69, 0.98]; p = 0.0322) and pain severity (HR 0.79 [0.65, 0.97]; p = 0.0209) vs PBO + ADT. Conclusions: Men with mHSPC were generally asymptomatic and had high levels of HRQoL and low levels of pain at BL, likely due to most men initiating ADT several months prior to study entry. No clinically meaningful differences in HRQoL were observed between ENZ and PBO. The prolongation in radiographic progression-free survival observed with ENZ + ADT was accompanied by a significantly prolonged time to progression of worst pain and pain severity vs PBO + ADT. Clinical trial information: NCT02677896.

TALAPRO-2: A two-part, placebo-controlled phase III study of talazoparib (TALA) with enzalutamide (ENZA) in metastatic castration-resistant prostate cancer (mCRPC)

TPS337

Background: ENZA is approved to treat men with CRPC. TALA is a poly(ADP-ribose) polymerase (PARP) inhibitor that inhibits PARP1/PARP2 and traps PARP on DNA, preventing DNA damage repair (DDR), and causing cell death in BRCA1/2-mutated cells. TALA is approved in the US to treat germline BRCA1/2-mutated HER2- locally advanced/metastatic breast cancer. A combination of TALA with ENZA in mCRPC may improve clinical outcomes. Methods: Eligible patients (pts) in parts (P) 1 and 2 of this study are aged ≥18 years; have asymptomatic/mildly symptomatic mCRPC, ECOG PS ≤1, and no brain metastases; and have not received taxanes/novel hormonal therapy (NHT). P1 is an open label study to confirm the starting dose of TALA to be given in combination with ENZA. P2 is a randomized double-blind study that will evaluate the safety, efficacy and pt reported outcomes of TALA (0.5 mg QD) + ENZA (160 mg QD) vs placebo + ENZA in 2 cohorts (C). C1: pts with mCRPC (all comers) (N = 560); C2: pts with DDR gene mutations likely to sensitize to PARP inhibition (DDR deficient) (N = 300). Randomization will be stratified by prior treatment with NHT for castration sensitive prostate cancer (CSPC) or prior treatment with taxane-based chemotherapy for CSPC (yes/no), and DDR mutation status (deficient vs. nondeficient/unknown). For P1, the primary endpoint is safety; the secondary endpoint is pharmacokinetics of TALA and ENZA. For P2, the primary endpoint is radiographic progression-free survival (rPFS), defined as time to progression in soft tissue per RECIST v1.1 or in bone per PCWG3 criteria or death and evaluated separately in all comers (C1) and DDR-deficient (DDR-deficient pts from C1 and C2 combined, N = 380 pts) populations. The key secondary endpoint is overall survival. Efficacy will be assessed by radiography every 8 weeks up to week 25 and every 8-12 weeks thereafter. P2 analysis for rPFS is powered at 90% and 85% using a 2-sided log-rank test with alpha of 0.025, respectively, in the all comers and DDR deficient populations. This study was sponsored by Pfizer Inc. Clinical trial information: NCT03395197.

Impact of enzalutamide (ENZA) vs. bicalutamide (BIC) on health-related quality of life (HRQoL) of patients (pts) with castration-resistant prostate cancer (CRPC): STRIVE study

234

Background: In STRIVE pts with CRPC (M0 n = 139; M1 n = 257), median time to 10-point decrease from baseline in FACT-P total for ENZA vs. BIC was 8.4 vs. 8.3 months (hazard ratio [HR] 0.91; 95% confidence interval [CI] 0.70, 1.19; p = 0.49). That assumed missing data was missing at random (MAR) and censored pts with no deterioration in FACT-P at last assessment. As HRQoL may worsen after progression/adverse events, for all STRIVE pts we replaced the MAR assumption with assumptions more likely to reflect clinically plausible HRQoL decline. Methods: Analyses of HRQoL decline (minimum clinically important difference or higher decrease in FACT-P vs. baseline) used a missing not at random (MNAR) assumption using a pattern mixture model (PMM) via sequential modeling with multiple imputation when imputation varies by reason of treatment discontinuation. Analysis of time to first clinically meaningful deterioration vs. baseline used a piecewise exponential survival multiple imputation model with reason-specific ∆ adjustment patterns similar to PMM analysis. Results: PMM analysis showed differences at week 61 in mean HRQoL change from baseline favoring ENZA vs. BIC for 7 of 10 scores: physical (PWB), functional, emotional (EWB), and social (SWB) well-being; FACT-P trial outcome index; FACT-G total; FACT-P total (all clinically meaningful except PWB). In the piecewise exponential survival imputation model, ENZA had a significantly lower risk of first deterioration in FACT-P total (0.76 [0.60, 0.95]), FACT-G total (0.66 [0.52, 0.83]), Prostate Cancer Subscale (PCS) pain-related (0.78 [0.62, 0.97]), SWB (0.49 [0.38, 0.64]), and EWB (0.58 [0.45, 0.75]) vs. BIC. For remaining domain scores, ENZA reduces risk of first deterioration (HR < 1) but the 95% CI includes 1 (which means not significant); sensitivity analysis showed similar results. Conclusions: In STRIVE pts, declines in all FACT-P scores were smaller for ENZA vs. BIC up to week 61. Comparison of change from baseline at week 61 favored ENZA for 7 of 10 scores (6 clinically meaningful). ENZA had a significantly lower risk of first deterioration in FACT-P or FACT-G total, PCS pain-related, EWB, and SWB. Clinical trial information: NCT01664923.

Pharmacokinetic (PK) subgroup results from the phase 2 pharmacodynamic and bioequivalence study of abiraterone acetate fine particle formulation (AAFP) in patients with metastatic castration-resistant prostate cancer (mCRPC): The STAAR study

176

Background: AAFP, a novel formulation, showed therapeutic equivalence to originator abiraterone acetate (OAA) in the Phase 2 STAAR study (Stein et al. Urologic Oncol). A patient-subgroup analysis compared steady-state PK parameters between AAFP and OAA. Methods: This multicenter, open-label, active-controlled study enrolled men with progressive mCRPC treated 1:1 with 500 mg AAFP tablets QD + 4 mg methylprednisolone BID, or 1000 mg OAA tablets QD + 5 mg prednisone BID for 9 days. Study drug was taken 2 hours post morning meal. On day 9, plasma abiraterone blood samples were collected at predose, 0.25, 0.5, 1, 2, 4, 6, 8, 10, and 24 hr time points. Results: PK samples were evaluable for 13 of 14 patients (n=5, AAFP; n=8, OAA). Mean age was 67.4 and 73.3 years, respectively. Twelve patients completed the 12-week study without clinical disease progression. One OAA patient died from MI in week 4. PK parameters (AUC, Cmax, Cmin), were numerically lower but not statistically significantly different for those treated with AAFP vs OAA (Table). Conclusions: Clinical benefit in this subgroup of patients was consistent with the overall study results. High PK variability was observed in both groups. PK parameters were not statistically different between AAFP and OAA. 24-hour PK Parameters at Steady State Clinical trial information: NCT02737332. [Table: see text]

Overall survival and immune responses with sipuleucel-T and enzalutamide: STRIDE study

246

Background: STRIDE (NCT01981122) is the first study comparing concurrent (con) vs sequential (seq) enzalutamide (enz) with sipuleucel-T (sip-T) in patients (pts) with metastatic castration-resistant prostate cancer. Pts were followed until death or for 3 years. Methods: Fifty-two pts were randomized 1:1 to 3 sip-T infusions and enz started 2 wks before (n = 25, con) or 10 wks after (n = 27, seq) sip-T. Enz was continued for 52 wks or until disease progression (DP)/toxicity. Time to clinical outcomes was estimated by Kaplan-Meier analysis. Results: Median age (years): con 66; seq 72 (p = 0.01). Baseline characteristics and laboratory values were similar between arms. K-M estimated median follow up: 40.2 months. Clinical trial information: NCT01981122. Conclusions: Long-term follow-up suggests sip-T+enz is well-tolerated with no new safety concerns. Though not powered for such, con vs seq rx did not result in differences in OS or DP; differences in PSA responses cannot be excluded. Larger studies could better evaluate the clinical impact of combining immunotherapy with hormonal agents.[Table: see text]

Enzalutamide Versus Bicalutamide in Castration-Resistant Prostate Cancer: The STRIVE Trial

PURPOSE

Enzalutamide, a potent oral androgen receptor inhibitor, improves survival in men with metastatic castration-resistant prostate cancer (CRPC) before and after chemotherapy. Bicalutamide, a nonsteroidal antiandrogen, is widely used to treat men with nonmetastatic or metastatic CRPC. The efficacy and safety of these drugs were compared in this randomized, double-blind, phase II study of men with CRPC.

PATIENTS AND METHODS

A total of 396 men with nonmetastatic (n = 139) or metastatic (n = 257) CRPC were randomly assigned to enzalutamide 160 mg per day (n = 198) or bicalutamide 50 mg per day (n = 198). Androgen deprivation therapy was continued in both arms. The primary end point was progression-free survival (PFS).

RESULTS

Enzalutamide reduced the risk of progression or death by 76% compared with bicalutamide (hazard ratio [HR], 0.24; 95% CI, 0.18 to 0.32; P < .001). Median PFS was 19.4 months with enzalutamide versus 5.7 months with bicalutamide. Enzalutamide resulted in significant improvements in all key secondary end points: time to prostate-specific antigen progression (HR, 0.19; 95% CI, 0.14 to 0.26; P < .001); proportion of patients with a ≥ 50% prostate-specific antigen response (81% v 31%; P < .001); and radiographic PFS in metastatic patients (HR, 0.32; 95% CI, 0.21 to 0.50; P < .001). Beneficial effects with enzalutamide were observed in both nonmetastatic and metastatic subgroups. The observed adverse event profile was consistent with that from phase III enzalutamide trials.

CONCLUSION

Enzalutamide significantly reduced risk of prostate cancer progression or death compared with bicalutamide in patients with nonmetastatic or metastatic CRPC.