Diagnosis and management of neuroendocrine prostate cancer

BACKGROUND

Although most patients with prostate cancer (PC) respond to initial androgen deprivation therapy (ADT), castration-resistant disease invariably develops. Progression to treatment-emergent neuroendocrine PC (t-NEPC) represents a unique mechanism of resistance to androgen receptor (AR)-targeted therapy in which lineage plasticity and neuroendocrine differentiation induce a phenotypic switch from an AR-driven adenocarcinoma to an AR-independent NEPC. t-NEPC is characterized by an aggressive clinical course, increased resistance to AR-targeted therapies, and a poor overall prognosis.

METHODS

This review provides an overview of our current knowledge of NEPC, with a focus on the unmet needs, diagnosis, and clinical management of t-NEPC.

RESULTS

Evidence extrapolated from the literature on small cell lung cancer or data from metastatic castration-resistant PC (mCRPC) cohorts enriched for t-NEPC suggests an increased sensitivity to platinum-based chemotherapy. However, optimal strategies for managing t-NEPC have not been established, and prospective clinical trial data are limited. Intertumoral heterogeneity within a given patient, as well as the lack of robust molecular or clinical biomarkers for early detection, often lead to delays in diagnosis and prolonged treatment with suboptimal strategies (i.e., conventional chemohormonal therapies for mCRPC), which may further contribute to poor outcomes.

CONCLUSIONS

Recent advances in genomic and molecular classification of NEPC and the development of novel biomarkers may facilitate an early diagnosis, help to identify promising therapeutic targets, and improve the selection of patients most likely to benefit from NEPC-targeted therapies.

Olaparib for the Treatment of Patients With Metastatic Castration-Resistant Prostate Cancer and Alterations in BRCA1 and/or BRCA2 in the PROfound Trial

Olaparib improved PFS and OS across subgroups of BRCA1/2mut #prostatecancer patients in the PROFOUND phase III trial.

Olaparib plus abiraterone versus placebo plus abiraterone in metastatic castration-resistant prostate cancer (PROpel): final prespecified overall survival results of a randomised, double-blind, phase 3 trial

BACKGROUND

PROpel met its primary endpoint showing statistically significant improvement in radiographic progression-free survival with olaparib plus abiraterone versus placebo plus abiraterone in patients with first-line metastatic castration-resistant prostate cancer (mCRPC) unselected by homologous recombination repair mutation (HRRm) status, with benefit observed in all prespecified subgroups. Here we report the final prespecified overall survival analysis.

METHODS

This was a randomised, double-blind, phase 3 trial done at 126 centres in 17 countries worldwide. Patients with mCRPC aged at least 18 years, Eastern Cooperative Oncology Group performance status 0-1, a life expectancy of at least 6 months, with no previous systemic treatment for mCRPC and unselected by HRRm status were randomly assigned (1:1) centrally by means of an interactive voice response system-interactive web response system to abiraterone acetate (orally, 1000 mg once daily) plus prednisone or prednisolone with either olaparib (orally, 300 mg twice daily) or placebo. The patients, the investigator, and study centre staff were masked to drug allocation. Stratification factors were site of metastases and previous docetaxel at metastatic hormone-sensitive cancer stage. Radiographic progression-free survival was the primary endpoint and overall survival was a key secondary endpoint with alpha-control (alpha-threshold at prespecified final analysis: 0·0377 [two-sided]), evaluated in the intention-to-treat population. Safety was evaluated in all patients who received at least one dose of a study drug. This study is registered with ClinicalTrials.gov, NCT03732820, and is completed and no longer recruiting.

FINDINGS

Between Oct 31, 2018 and March 11, 2020, 1103 patients were screened, of whom 399 were randomly assigned to olaparib plus abiraterone and 397 to placebo plus abiraterone. Median follow-up for overall survival in patients with censored data was 36·6 months (IQR 34·1-40·3) for olaparib plus abiraterone and 36·5 months (33·8-40·3) for placebo plus abiraterone. Median overall survival was 42·1 months (95% CI 38·4-not reached) with olaparib plus abiraterone and 34·7 months (31·0-39·3) with placebo plus abiraterone (hazard ratio 0·81, 95% CI 0·67-1·00; p=0·054). The most common grade 3-4 adverse event was anaemia reported in 64 (16%) of 398 patients in the olaparib plus abiraterone and 13 (3%) of 396 patients in the placebo plus abiraterone group. Serious adverse events were reported in 161 (40%) in the olaparib plus abiraterone group and 126 (32%) in the placebo plus abiraterone group. One death in the placebo plus abiraterone group, from interstitial lung disease, was considered treatment related.

INTERPRETATION

Overall survival was not significantly different between treatment groups at this final prespecified analysis.

FUNDING

Supported by AstraZeneca and Merck Sharp & Dohme.

Olaparib Efficacy in Patients with Metastatic Castration-resistant Prostate Cancer and BRCA1, BRCA2, or ATM Alterations Identified by Testing Circulating Tumor DNA

PURPOSE

The phase III PROfound study (NCT02987543) evaluated olaparib versus abiraterone or enzalutamide (control) in metastatic castration-resistant prostate cancer (mCRPC) with tumor homologous recombination repair (HRR) gene alterations. We present exploratory analyses on the use of circulating tumor DNA (ctDNA) testing as an additional method to identify patients with mCRPC with HRR gene alterations who may be eligible for olaparib treatment.

PATIENTS AND METHODS

Plasma samples collected during screening in PROfound were retrospectively sequenced using the FoundationOne®Liquid CDx test for BRCA1, BRCA2 (BRCA), and ATM alterations in ctDNA. Only patients from Cohort A (BRCA/ATM alteration positive by tissue testing) were evaluated. We compared clinical outcomes, including radiographic progression-free survival (rPFS) between the ctDNA subgroup and Cohort A.

RESULTS

Of the 181 (73.9%) Cohort A patients who gave consent for plasma sample ctDNA testing, 139 (76.8%) yielded a result and BRCA/ATM alterations were identified in 111 (79.9%). Of these, 73 patients received olaparib and 38 received control. Patients' baseline demographics and characteristics, and the prevalence of HRR alterations were comparable with the Cohort A intention-to-treat (ITT) population. rPFS was longer in the olaparib group versus control [median 7.4 vs. 3.5 months; hazard ratio (HR), 0.33; 95% confidence interval (CI), 0.21-0.53; nominal P < 0.0001], which is consistent with Cohort A ITT population (HR, 0.34; 95% CI, 0.25-0.47).

CONCLUSIONS

When tumor tissue testing is not feasible or has failed, ctDNA testing may be a suitable alternative to identify patients with mCRPC carrying BRCA/ATM alterations who may benefit from olaparib treatment.

Testing for homologous recombination repair or homologous recombination deficiency for poly (ADP-ribose) polymerase inhibitors: A current perspective

Poly (ADP-ribose) polymerase inhibitors (PARPis) have demonstrated clinical activity in patients with BRCA1 and/or BRCA2 mutated breast, ovarian, prostate, and pancreatic cancers. Notably, BRCA mutations are associated with defects in the homologous recombination repair (HRR) pathway. This homologous recombination deficiency (HRD) phenotype can also be observed as genomic instability in tumour cells. Accordingly, PARPi sensitivity has been observed in various tumours with HRD, independent of BRCA mutations. Currently, four PARPis are approved by regulatory agencies for the treatment of cancer across multiple tumour types. Most indications are specific to tumours with a confirmed BRCA mutation, mutations in other HRR-related genes, HRD evidenced by genomic instability, or evidence of platinum sensitivity. Regulatory agencies have also approved companion and complementary diagnostics to facilitate patient selection for each PARPi indication. This review aims to summarise the biological basis, clinical validation, and clinical relevance of the available diagnostic methods and assays to assess HRD.

Abiraterone and Olaparib for Metastatic Castration-Resistant Prostate Cancer

Abiraterone and Olaparib for Metastatic Prostate CancerPatients with metastatic castration-resistant prostate cancer, regardless of homologous recombination repair gene mutation status, received either abiraterone and olaparib or abiraterone and placebo in the first-line setting. Imaging-based progression-free survival was 24.8 months for patients treated with abiraterone and olaparib versus 16.6 months for those receiving abiraterone alone.

Pain and health-related quality of life with olaparib versus physician's choice of next-generation hormonal drug in patients with metastatic castration-resistant prostate cancer with homologous recombination repair gene alterations (PROfound): an open-label, randomised, phase 3 trial

BACKGROUND

The PROfound study showed significantly improved radiographical progression-free survival and overall survival in men with metastatic castration-resistant prostate cancer with alterations in homologous recombination repair genes and disease progression on a previous next-generation hormonal drug who received olaparib then those who received control. We aimed to assess pain and patient-centric health-related quality of life (HRQOL) measures in patients in the trial.

METHODS

In this open-label, randomised, phase 3 study, patients (aged ≥18 years) with metastatic castration-resistant prostate cancer and gene alterations to one of 15 genes (BRCA1, BRCA2, or ATM [cohort A] and BRIP1, BARD1, CDK12, CHEK1, CHEK2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, and RAD54L [cohort B]) and disease progression after a previous next-generation hormonal drug were randomly assigned (2:1) to receive olaparib tablets (300 mg orally twice daily) or a control drug (enzalutamide tablets [160 mg orally once daily] or abiraterone tablets [1000 mg orally once daily] plus prednisone tablets [5 mg orally twice daily]), stratified by previous taxane use and measurable disease. The primary endpoint (radiographical progression-free survival in cohort A) has been previously reported. The prespecified secondary endpoints reported here are on pain, HRQOL, symptomatic skeletal-related events, and time to first opiate use for cancer-related pain in cohort A. Pain was assessed with the Brief Pain Inventory-Short Form, and HRQOL was assessed with the Functional Assessment of Cancer Therapy-Prostate (FACT-P). All endpoints were analysed in patients in cohort A by modified intention-to-treat. The study is registered with ClinicalTrials.gov, NCT02987543.

FINDINGS

Between Feb 6, 2017, and June 4, 2019, 245 patients were enrolled in cohort A and received study treatment (162 [66%] in the olaparib group and 83 [34%] in the control group). Median duration of follow-up at data cutoff in all patients was 6·2 months (IQR 2·2-10·4) for the olaparib group and 3·5 months (1·7-4·9) for the control group. In cohort A, median time to pain progression was significantly longer with olaparib than with control (median not reached [95% CI not reached-not reached] with olaparib vs 9·92 months [5·39-not reached] with control; HR 0·44 [95% CI 0·22-0·91]; p=0·019). Pain interference scores were also better in the olaparib group (difference in overall adjusted mean change from baseline score -0·85 [95% CI -1·31 to -0·39]; pnominal=0·0004). Median time to progression of pain severity was not reached in either group (95% CI not reached-not reached for both groups; HR 0·56 [95% CI 0·25-1·34]; pnominal=0·17). In patients who had not used opiates at baseline (113 in the olaparib group, 58 in the control group), median time to first opiate use for cancer-related pain was 18·0 months (95% CI 12·8-not reached) in the olaparib group versus 7·5 months (3·2-not reached) in the control group (HR 0·61; 95% CI 0·38-0·99; pnominal=0·044). The proportion of patients with clinically meaningful improvement in FACT-P total score during treatment was higher for the olaparib group than the control group: 15 (10%) of 152 evaluable patients had a response in the olaparib group compared with one (1%) of evaluable 77 patients in the control group (odds ratio 8·32 [95% CI 1·64-151·84]; pnominal=0·0065). Median time to first symptomatic skeletal-related event was not reached for either treatment group (olaparib group 95% CI not reached-not reached; control group 7·8-not reached; HR 0·37 [95% CI 0·20-0·70]; pnominal=0·0013).

INTERPRETATION

Olaparib was associated with reduced pain burden and better-preserved HRQOL compared with the two control drugs in men with metastatic castration-resistant prostate cancer and homologous recombination repair gene alterations who had disease progression after a previous next-generation hormonal drug. Our findings support the clinical benefit of improved radiographical progression-free survival and overall survival identified in PROfound.

FUNDING

AstraZeneca and Merck Sharp & Dohme.

Tumor Genomic Testing for >4000 Men with Metastatic Castration-resistant Prostate Cancer in the Phase III Trial PROfound (Olaparib)

PURPOSE

Successful implementation of genomic testing in clinical practice is critical for identification of men with metastatic castration-resistant prostate cancer (mCRPC) eligible for olaparib and future molecularly targeted therapies.

PATIENTS AND METHODS

An investigational clinical trial assay, based on the FoundationOne^®CDx tissue test, was used to prospectively identify patients with qualifying homologous recombination repair (HRR) gene alterations in the phase III PROfound study. Evaluation of next-generation sequencing (NGS) tissue test outcome against pre-analytical parameters was performed to identify key factors influencing NGS result generation.

RESULTS

4858 tissue samples from 4047 patients were tested and reported centrally. NGS results were obtained in 58% (2792/4858) of samples, equating to 69% of patients. Of samples submitted, 83% were primary tumor samples (96% were archival and 4% newly obtained). Almost 17% were metastatic tumor samples (60% were archival and 33% newly obtained). NGS results were generated more frequently from newly obtained compared with archival samples (63.9% v. 56.9%), and metastatic compared with primary samples (63.9% v. 56.2%). Although generation of an NGS result declined with increasing sample age, approximately 50% of samples aged >10 years generated results. While higher tumor content and DNA yield resulted in greater success in obtaining NGS results, other factors, including selection and preservation of samples, may also have had an impact.

CONCLUSIONS

The PROfound study demonstrates that tissue testing to identify HRR alterations is feasible and that high-quality tumor tissue samples are key to obtaining NGS results and identifying patients with mCRPC who may benefit from olaparib treatment.

347 KEYNOTE-365 cohort C: pembrolizumab + enzalutamide in patients with abiraterone acetate–pretreated metastatic castration-resistant prostate cancer (mCRPC)—data after minimum of 22 months of follow-up

Background

Previous data from cohort C of phase 1b/2 study KEYNOTE-365 (NCT02861573) showed that PD-1 inhibitor pembrolizumab + enzalutamide was well tolerated and showed antitumor activity in patients with abiraterone acetate–pretreated mCRPC. Updated data after a minimum of 22 months of follow-up are presented.

Methods

Patients in the prechemotherapy mCRPC state who were intolerant to ≥4 weeks‘ treatment with abiraterone acetate or for whom this treatment failed, had progressive disease ≤6 months before screening, and had ECOG PS 0-2 were enrolled. Patients received pembrolizumab 200 mg IV Q3W + enzalutamide 160 mg orally QD. Primary end points were PSA response rate (decrease ≥50% from baseline), confirmed ORR per RECIST v1.1 by blinded independent central review (BICR), and safety. Secondary end points were time to PSA progression; DCR (CR or PR of any duration + SD or non-CR/non-PD ≥6 months) and DOR per RECIST v1.1 by BICR; rPFS per PCWG3-modified RECIST v1.1 by BICR; and OS.

Results

Of 103 enrolled patients, 102 were treated. Median age was 70.0 years (range, 43–87); 29.4% of patients were PD-L1+; 37.3% had RECIST-measurable disease. Median follow-up (time from enrollment to data cutoff) was 40.2 months (range, 22.3–49.9). Confirmed PSA response rate in patients with baseline PSA measurement (N = 101) was 23.8%. Median time to PSA progression was 4.0 months (95% CI, 3.5–4.4). In 38 patients with measurable disease, ORR was 10.5% (2 CR; 2 PR). Median DOR was 11.8 months (4.3 to 38.3+ months); 1 patient had a response ≥12 months. DCR for the total population was 33.3%. Median (95% CI) rPFS was 6.0 months (4.1–6.3); rPFS at 12 months was 30.1%. Median (95% CI) OS was 20.1 months (16.9–25.2); OS at 12 months was 76.2%. Treatment-related AEs (TRAEs) occurred in 92.2% of patients; most common (≥20%) were fatigue (39.2%), nausea (21.6%), and rash (21.6%). Grade 3–5 TRAEs occurred in 42.2%, most commonly rash (7.8%) and fatigue (5.9%). Four patients died of AEs: 1 death was treatment-related (unknown cause).

Conclusions

After a minimum follow-up of 22 months, pembrolizumab + enzalutamide continued to show antitumor activity in abiraterone acetate–pretreated mCRPC. The safety profile of pembrolizumab + enzalutamide was generally consistent with individual profiles of each agent. There was a higher incidence than typically reported for the individual agents of all-grade (21.6%) and grade 3 (7.8%) rash, which resolved with standard-of-care treatment. The combination is being further evaluated in the phase 3 study KEYNOTE-641.

Acknowledgements

Medical writing and/or editorial assistance was provided by Matthew Grzywacz, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Funding for this research was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Trial Registration

ClinicalTrials

gov, identifier: NCT02861573

Ethics Approval

The study and the protocol were approved by the Institutional Review Board or ethics committee at each site.

351 KEYNOTE-365 cohort D: pembrolizumab plus abiraterone acetate and prednisone in patients with chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC)

Background

Treatment with abiraterone acetate + prednisone can improve outcomes in mCRPC patients with or without prior chemotherapy. Cohort D of phase 1b/2 study KEYNOTE-365 (NCT02861573) evaluated safety and efficacy of PD-1 inhibitor pembrolizumab + abiraterone acetate and prednisone in patients who had not received chemotherapy for mCRPC.

Methods

Patients were enrolled who had not received second-generation hormonal manipulation for mCRPC or failed/were intolerant to enzalutamide for mCRPC; had progressive disease ≤6 months before screening; and had ECOG PS 0/1. Patients received pembrolizumab 200 mg IV Q3W + abiraterone acetate 1000 mg orally QD and prednisone 5 mg orally BID. Primary end points: safety, PSA response rate (PSA decrease ≥50% from baseline), and confirmed ORR per RECIST v1.1 by blinded independent central review (BICR). Secondary end points: rPFS per PCWG3-modified RECIST v1.1, DCR, DOR, and OS.

Results

One hundred three patients were treated. Median (range) age was 70.0 (46–89) years, 30.1% were PD-L1+, 35.9% had RECIST-measurable disease, 18.4% had visceral disease, and 26.2% had previously received enzalutamide only. Median (range) time from enrollment to data cutoff was 17.6 (9.7–27.0) months. Confirmed PSA response rate in patients with PSA measurement at baseline (n=103) was 56.3%. For 37 patients with RECIST-measurable disease, ORR was 16.2% (1 CR; 5 PRs); 2 patients with RECIST-nonmeasurable disease had CR. In total population, 5 patients had a response ≥6 months; DCR was 44.7%. ORR for RECIST-measurable patients was 7.7% for those who previously received enzalutamide only (n=13) and 21.7% for those who had not previously received NHAs (n=23); DCR was 11.1% in all patients who previously received enzalutamide (n=27) and 57.3% in all patients who had not received NHAs (n=75). Median (95% CI) rPFS was 15.1 (9.2-NR) months; rPFS at 12 months was 54.9%. Median (95% CI) OS was NR (23.3 months-NR); OS at 12 months was 82.9%. Sixty-nine patients (67.0%) discontinued treatment, mostly because of progressive disease (37.9%). Treatment-related AEs (TRAEs) were experienced by 90.3% of patients and most common (≥15%) were ALT increase (22.3%), AST increase (17.5%), asthenia (16.5%), and diarrhea (16.5%); 36.9% experienced grade 3–5 TRAEs. There were 18.4%/12.5% grade 3 or 4 ALT/AST laboratory elevations. Five patients died of AEs; 1 was treatment related (myasthenic syndrome).

Conclusions

Pembrolizumab + abiraterone acetate and prednisone demonstrated antitumor activity in patients with chemotherapy-naive mCRPC. Safety was generally consistent with individual profiles of each agent. There was an increased incidence of grade 3–4 ALT/AST laboratory elevations.

Acknowledgements

Medical writing and/or editorial assistance was provided by Matthew Grzywacz, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Funding for this research was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Trial Registration

ClinicalTrials

gov, identifier: NCT02861573

Ethics Approval

The study and the protocol were approved by the Institutional Review Board or ethics committee at each site.

419 Pembrolizumab + lenvatinib in patients with adenocarcinoma metastatic castration-resistant prostate cancer (mCRPC) or treatment-emergent neuroendocrine mCRPC: Phase 1b/2 KEYNOTE-365 cohorts E/F

Background

Treatment of adenocarcinoma mCRPC includes abiraterone, enzalutamide, or docetaxel but is not curative, and ~20% of patients develop treatment-emergent neuroendocrine mCRPC (t-NE) after diagnosis of adenocarcinoma. Monotherapy with the PD-1 inhibitor pembrolizumab showed promising antitumor activity in the phase 2 KEYNOTE-199 trial in adenocarcinoma mCRPC. The vascular endothelial growth factor (VEGF)/fibroblast growth factor receptor (FGFR) inhibitor lenvatinib inhibits proliferation and angiogenesis in mice models. Combined PD-1 and VEGF/FGFR inhibition may have enhanced benefit in adenocarcinoma mCRPC or t-NE.

Methods

The nonrandomized, open-label, multicohort, phase 1b/2 KEYNOTE-365 study (NCT02861573) will be conducted to evaluate several pembrolizumab combination therapies in patient populations with adenocarcinoma mCRPC or t-NE. In cohorts E and F each, 40–100 adults with Eastern Cooperative Oncology Group performance status score of 0/1 who received docetaxel for mCRPC will be enrolled. Prior therapy with ≤2 next-generation hormonal agents (NHAs) and 1 other chemotherapy for mCRPC is permitted. Patients in cohort E must have confirmed adenocarcinoma of the prostate without small cell histology at study entry. Patients in cohort F must have t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review) that progressed within 6 months of starting an NHA for mCRPC or hormone-sensitive metastatic prostate cancer and progressed within 6 cycles of docetaxel for mCRPC. Both cohorts will receive pembrolizumab 200 mg intravenously every 3 weeks + oral lenvatinib 20 mg daily until disease progression, consent withdrawal, or other discontinuation event. Computed tomography or magnetic resonance imaging will be performed at screening, every 9 weeks through week 54, and every 12 weeks thereafter. Adverse events will be monitored through 30 days after discontinuation (90 days if serious) and graded per CTCAE v4.0. Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points are time to PSA progression; ORR and radiographic progression-free survival (rPFS) per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by BICR; duration of response and disease control rate per RECIST v1.1 and PCWG3-modified RECIST v1.1 by BICR; and overall survival.

Acknowledgements

Medical writing and/or editorial assistance was provided by Matthew Grzywacz, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Funding for this research was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Trial Registration

Clinicaltrials.

gov, NCT02861573

Ethics Approval

The study and the protocol were approved by the Institutional Review Board or ethics committee at each site.

418 Phase 1b/2 KEYNOTE-365 cohort I: platinum-containing chemotherapy alone or in combination with pembrolizumab for treatment-emergent neuroendocrine prostate carcinoma

Background

Treatment-emergent neuroendocrine prostate carcinoma (t-NE) can occur de novo or after diagnosis of prostate adenocarcinoma. Treatment often includes platinum-containing chemotherapy because of t-NE’s histologic similarity to small cell lung cancer. The PD-1 inhibitor pembrolizumab has shown promising efficacy and acceptable safety when combined with olaparib, docetaxel, or enzalutamide for treatment of metastatic castration-resistant prostate cancer (mCRPC) in the multicohort phase 1b/2 KEYNOTE-365 study (NCT02861573). Cohort I will be used to compare platinum-containing chemotherapy alone with chemotherapy + pembrolizumab as treatment for t-NE.

Methods

Patients who have t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review); experienced progression within 6 months of starting a next-generation hormonal agent (NHA) for mCRPC or hormone-sensitive prostate cancer and experienced progression within 6 cycles of docetaxel treatment for mCRPC; and have an Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1 are eligible. Prior therapy with ≤2 NHAs and 1 other chemotherapy for mCRPC is permitted. Patients will be randomly assigned 1:1 to receive pembrolizumab 200 mg IV on day 1 of each cycle every 3 weeks + carboplatin AUC of 5 IV on day 1 + etoposide 100 mg/m2 IV on days 1, 2, and 3 of each 21-day cycle for 4 cycles (arm 1) or the same chemotherapy regimen without pembrolizumab (arm 2); in each arm 40–100 patients will be enrolled. Pembrolizumab treatment will continue up to 2 years until disease progression, unacceptable toxicity, or withdrawal of consent. Patients will be stratified by ECOG performance status score (0 or 1). Computed tomography or magnetic resonance imaging will be performed every 9 weeks through week 54 and every 12 weeks thereafter. Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points are time to PSA progression; ORR and radiographic progression-free survival (PFS) per PCWG3-modified RECIST v1.1 by BICR; duration of response and disease control rate per RECIST v1.1 by BICR and PCWG3-modified RECIST v1.1 by BICR; and overall survival. End points will be summarized for each arm without formal hypothesis testing.

Acknowledgements

Medical writing and/or editorial assistance was provided by Matthew Grzywacz, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Funding for this research was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Trial Registration

Clinicaltrials.

gov, NCT02861573

Ethics Approval

The study and the protocol were approved by the Institutional Review Board or ethics committee at each site.

425 Pembrolizumab + vibostolimab in patients with adenocarcinoma metastatic castration-resistant prostate cancer (mCRPC) or treatment-emergent neuroendocrine mCRPC: phase 1b/2 KEYNOTE-365 cohorts G/H

Background

Frontline treatment for patients with adenocarcinoma mCRPC includes docetaxel, radium 223, or the next-generation hormonal agents (NHAs) abiraterone or enzalutamide. For patients with disease progression on these therapies, approximately 20% will develop treatment-emergent neuroendocrine mCRPC (t-NE) after diagnosis of prostate adenocarcinoma. The PD-1 inhibitor pembrolizumab showed antitumor activity when combined with olaparib in cohort A of the phase 1b/2 KEYNOTE-365 trial, and the TIGIT inhibitor vibostolimab showed antitumor activity in preclinical models. Combining PD-1 and TIGIT inhibition may have enhanced benefit in adenocarcinoma mCRPC or t-NE.

Methods

KEYNOTE-365 is a nonrandomized, open-label, multicohort study (NCT02861573) to assess several pembrolizumab combination therapies in patient populations with adenocarcinoma mCRPC or t-NE. In each of cohorts G and H, 40–100 adults with Eastern Cooperative Oncology Group performance status (ECOG PS) 0/1 who received docetaxel for mCRPC will be enrolled. Prior therapy with ≤2 NHAs and 1 other chemotherapy for adenocarcinoma mCRPC is permitted. Patients in cohort G must have adenocarcinoma of the prostate without small cell histology at study entry. Patients in cohort H must have t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review) that progressed within 6 months of starting an NHA for mCRPC or hormone-sensitive prostate cancer and progressed within 6 cycles of docetaxel for mCRPC. All patients will receive MK-7684A, a coformulation of pembrolizumab 200 mg and vibostolimab 200 mg intravenously every 3 weeks until disease progression, consent withdrawal, or other discontinuation event. Adverse events will be monitored through 30 days after discontinuation (90 days if serious) and graded per CTCAE v4.0. Computed tomography or magnetic resonance imaging will be performed at screening, every 9 weeks through week 54, and every 12 weeks thereafter. Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points are time to PSA progression, ORR and radiographic progression-free survival per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by BICR; duration of response and disease control rate per RECIST v1.1 and PCWG3-modified RECIST v1.1 by BICR; and overall survival.

Acknowledgements

Medical writing and/or editorial assistance was provided by Matthew Grzywacz, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Funding for this research was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

Trial Registration

Clinicaltrials.

gov, NCT02861573

Ethics Approval

The study and the protocol were approved by the Institutional Review Board or ethics committee at each site.

Pembrolizumab for Treatment-Refractory Metastatic Castration-Resistant Prostate Cancer: Multicohort, Open-Label Phase II KEYNOTE-199 Study

PURPOSE

Pembrolizumab has previously shown antitumor activity against programmed death ligand 1 (PD-L1)-positive metastatic castration-resistant prostate cancer (mCRPC). Here, we assessed the antitumor activity and safety of pembrolizumab in three parallel cohorts of a larger mCRPC population.

METHODS

The phase II KEYNOTE-199 study included three cohorts of patients with mCRPC treated with docetaxel and one or more targeted endocrine therapies. Cohorts 1 and 2 enrolled patients with RECIST-measurable PD-L1-positive and PD-L1-negative disease, respectively. Cohort 3 enrolled patients with bone-predominant disease, regardless of PD-L1 expression. All patients received pembrolizumab 200 mg every 3 weeks for up to 35 cycles. The primary end point was objective response rate per RECIST v1.1 assessed by central review in cohorts 1 and 2. Secondary end points included disease control rate, duration of response, overall survival (OS), and safety.

RESULTS

Two hundred fifty-eight patients were enrolled: 133 in cohort 1, 66 in cohort 2, and 59 in cohort 3. Objective response rate was 5% (95% CI, 2% to 11%) in cohort 1 and 3% (95% CI, < 1% to 11%) in cohort 2. Median duration of response was not reached (range, 1.9 to ≥ 21.8 months) and 10.6 months (range, 4.4 to 16.8 months), respectively. Disease control rate was 10% in cohort 1, 9% in cohort 2, and 22% in cohort 3. Median OS was 9.5 months in cohort 1, 7.9 months in cohort 2, and 14.1 months in cohort 3. Treatment-related adverse events occurred in 60% of patients, were of grade 3 to 5 severity in 15%, and led to discontinuation of treatment in 5%.

CONCLUSION

Pembrolizumab monotherapy shows antitumor activity with an acceptable safety profile in a subset of patients with RECIST-measurable and bone-predominant mCRPC previously treated with docetaxel and targeted endocrine therapy. Observed responses seem to be durable, and OS estimates are encouraging.

Immunopathological observations after xenogeneic liver perfusions using donor pigs transgenic for human decay-accelerating factor

BACKGROUND

Donor pigs transgenic for human decay-accelerating factor (hDAF) were used in a xenogeneic ex vivo liver perfusion model to study the effect of this modification on the development of hyperacute rejection.

METHODS

Three transgenic pigs were hepatectomized after hypothermic portal and transaortal gravity perfusion. Livers from six nontransgenic pigs served as controls. All livers were perfused for 3 hr with human blood from two donors diluted to a hematocrit of 30%. Particular importance was placed on the use of an optimal perfusion technique incorporating the floating suspension of the organs in a waterbath and intermittent external pressurization. Biochemical, physiological, and immunological parameters were assessed. Tissue specimens taken before and after perfusion were analyzed using routine histology, electron microscopy, and immunohistology.

RESULTS

Complement activation was more pronounced in the control group. AP50 and CH50 values fell to about 60% of the initial levels in control experiments, whereas they remained at 80% of the initial levels during perfusion of hDAF livers. After 180 min, pig tumor necrosis factor alpha levels were 7862+/-1645 pg/ml for unmodified livers and 2830+/-734 pg/ml in the hDAF group. Human tumor necrosis factor alpha levels were similar in both groups. Control livers showed marked morphological alterations and distinct deposition of complement factors, whereas livers expressing hDAF showed no signs of hepatocellular necrosis and almost no complement deposition beyond C3 activation.

CONCLUSIONS

These results confirm that the transgenic expression of the human complement regulatory protein hDAF reduces complement activation and prevents hyperacute rejection in a xenogeneic liver perfusion model over the 3-hr evaluation period used in this study.

Application of immunoapheresis for delaying hyperacute rejection during isolated xenogeneic pig liver perfusion

BACKGROUND

Extracorporeal liver perfusion in hepatic coma, used to eliminate toxic metabolites causing hepatic encephalopathy, is limited by the antibody (Ab) and complement-mediated hyperacute rejection of discordant xenografts. Thus, the efficacy of highly selective immunoadsorption columns to deplete xenoreactive human anti-porcine antibodies before ex vivo liver perfusion was examined in this study.

METHODS

Eighteen domestic pigs were hepatectomized according to standard techniques. The livers were ex vivo perfused for 4 hr. The perfusion protocol closely followed the physiological conditions of a human liver. Parameters of liver function and damage were analyzed. Three groups were formed differing in the treatment of the perfusate. As basic control, livers were perfused with heparinized human blood (group 1; n=6). Immunoapheresis was applied in group 3 (n=6). Immunoapheresis was performed using Ig Therasorb columns consisting of sheep-anti-human IgG Abs covalently coupled to Sepharose CL-4B. Additionally, the effect of pure Sepharose CL-4B without immobilized Ab was tested in group 2 (n=6).

RESULTS

The use of Ig Therasorb 100 columns in group 3 resulted in a reduction of IgG, IgM, and IgA in the order of 95.0%, 72.3%, and 81.5%, respectively. In group 2, IgG, IgM, and IgA were lowered by 30% to 39%. Determination of liver-specific enzymes and tolerance tests revealed a significant reduction of cellular damage and functional restrictions in group 3 compared with the control groups.

CONCLUSIONS

Immunoapheresis conducted according to this protocol appears to be an effective approach for delaying antibody-mediated hyperacute xenogeneic rejection.

Expression of human decay accelerating factor (hDAF) in transgenic pigs regulates complement activation during ex vivo liver perfusion--immunopathological findings

Ex vivo perfusions of human decay accelerating factor-expressing transgenic (n = 3), and nontransgenic (n = 6) porcine livers with human blood revealed a higher degree of organ damage in non-transgenic pig livers. Transgenic livers were protected from immunohistologically detectable complement deposition, despite corresponding IgM and IgG deposits in both groups. Complement activation and consumption of C3 and C4 turned out to be lower in transgenic pig livers. In contrast to livers of normal landrace pigs, livers from genetically manipulated pigs showed no morphological alterations after perfusion.