[177Lu]Lu-PSMA-617 plus enzalutamide in patients with metastatic castration-resistant prostate cancer (ENZA-p): an open-label, multicentre, randomised, phase 2 trial

BACKGROUND

Enzalutamide and lutetium-177 [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 both improve overall survival in patients with metastatic castration-resistant prostate cancer. Androgen and PSMA receptors have a close intracellular relationship, with data suggesting complementary benefit if targeted concurrently. In this study, we assessed the activity and safety of enzalutamide plus adaptive-dosed [177Lu]Lu-PSMA-617 versus enzalutamide alone as first-line treatment for metastatic castration-resistant prostate cancer.

METHODS

ENZA-p was an open-label, randomised, controlled phase 2 trial done at 15 hospitals in Australia. Participants were men aged 18 years or older with metastatic castration-resistant prostate cancer not previously treated with docetaxel or androgen receptor pathway inhibitors for metastatic castration-resistant prostate cancer, gallium-68 [68Ga]Ga-PSMA-PET-CT (PSMA-PET-CT) positive disease, Eastern Cooperative Oncology Group performance status of 0-2, and at least two risk factors for early progression on enzalutamide. Participants were randomly assigned (1:1) by a centralised, web-based system using minimisation with a random component to stratify for study site, disease burden, use of early docetaxel, and previous treatment with abiraterone acetate. Patients were either given oral enzalutamide 160 mg daily alone or with adaptive-dosed (two or four doses) intravenous 7·5 GBq [177Lu]Lu-PSMA-617 every 6-8 weeks dependent on an interim PSMA-PET-CT (week 12). The primary endpoint was prostate-specific antigen (PSA) progression-free survival, defined as the interval from the date of randomisation to the date of first evidence of PSA progression, commencement of non-protocol anticancer therapy, or death. The analysis was done in the intention-to-treat population, using stratified Cox proportional hazards regression. This trial is registered with ClinicalTrials.gov, NCT04419402, and participant follow-up is ongoing.

FINDINGS

162 participants were randomly assigned between Aug 17, 2020, and July 26, 2022. 83 men were assigned to the enzalutamide plus [177Lu]Lu-PSMA-617 group, and 79 were assigned to the enzalutamide group. Median follow-up in this interim analysis was 20 months (IQR 18-21), with 32 (39%) of 83 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 16 (20%) of 79 patients in the enzalutamide group remaining on treatment at the data cutoff date. Median age was 71 years (IQR 64-76). Median PSA progression-free survival was 13·0 months (95% CI 11·0-17·0) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 7·8 months (95% CI 4·3-11·0) in the enzalutamide group (hazard ratio 0·43, 95% CI 0·29-0·63, p<0·0001). The most common adverse events (all grades) were fatigue (61 [75%] of 81 patients), nausea (38 [47%]), and dry mouth (32 [40%]) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and fatigue (55 [70%] of 79), nausea (21 [27%]), and constipation (18 [23%]) in the enzalutamide group. Grade 3-5 adverse events occurred in 32 (40%) of 81 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 32 (41%) of 79 patients in the enzalutamide group. Grade 3 events that occurred only in the enzalutamide plus [177Lu]Lu-PSMA-617 group included anaemia (three [4%] of 81 participants) and decreased platelet count (one [1%] participant). No grade 4 or 5 events were attributed to treatment on central review in either group.

INTERPRETATION

The addition of [177Lu]Lu-PSMA-617 to enzalutamide improved PSA progression-free survival providing evidence of enhanced anticancer activity in patients with metastatic castration-resistant prostate cancer with risk factors for early progression on enzalutamide and warrants further evaluation of the combination more broadly in metastatic prostate cancer.

FUNDING

Prostate Cancer Research Alliance (Movember and Australian Federal Government), St Vincent's Clinic Foundation, GenesisCare, Roy Morgan Research, and Endocyte (a Novartis company).

Patient satisfaction with telehealth consultations in medical oncology clinics: A cross-sectional study at a metropolitan centre during the COVID-19 pandemic

INTRODUCTION

The coronavirus disease 2019 (COVID-19) pandemic has resulted in a widespread adoption of telehealth (phone and video consultations) in cancer care worldwide. The aim of this study was to determine patient satisfaction with telehealth consultations with their medical oncologist at a tertiary cancer centre in Sydney, Australia.

METHODS

Patients who attended a routine telehealth appointment at the medical oncology outpatient clinic were recruited to complete a questionnaire containing 16 items, each on a 5-point Likert scale regarding satisfaction levels in various aspects of telehealth and their willingness to continue telehealth after the pandemic. Patients were also invited to provide suggestions for improvement.

RESULTS

In total, 150 patients were invited to participate, and 103 valid questionnaires were returned. Median age was 63 years (range: 25-90), 49% of patients were male, 63% of patients had advanced cancer and 81% were on active treatment. In total, 95% of participants indicated that they were satisfied (score ≥4) with telehealth. 82% of participants preferred to continue telehealth consultations after the coronavirus disease 2019 pandemic, but ideally with a mix of telehealth and in-person consultations. Phone appointments (vs. video, p < 0.002), patients with advanced cancer (vs. early, p < 0.036) and pre-chemotherapy/immunotherapy/targeted therapy treatment reviews (vs. follow-up appointments, p < 0.001) were significantly associated with a willingness to continue telehealth.

DISCUSSION

Patients were overwhelmingly satisfied with telehealth during the study period and were willing to continue telehealth for some appointments beyond the coronavirus disease 2019 pandemic. More research into the effectiveness, safety and implementation of telehealth to compliment traditional face-to-face services for patient-centred cancer care is required.

Characterizing prostate cancer risk through multi-ancestry genome-wide discovery of 187 novel risk variants

The transferability and clinical value of genetic risk scores (GRSs) across populations remain limited due to an imbalance in genetic studies across ancestrally diverse populations. Here we conducted a multi-ancestry genome-wide association study of 156,319 prostate cancer cases and 788,443 controls of European, African, Asian and Hispanic men, reflecting a 57% increase in the number of non-European cases over previous prostate cancer genome-wide association studies. We identified 187 novel risk variants for prostate cancer, increasing the total number of risk variants to 451. An externally replicated multi-ancestry GRS was associated with risk that ranged from 1.8 (per standard deviation) in African ancestry men to 2.2 in European ancestry men. The GRS was associated with a greater risk of aggressive versus non-aggressive disease in men of African ancestry (P = 0.03). Our study presents novel prostate cancer susceptibility loci and a GRS with effective risk stratification across ancestry groups.

Multi-Omic Integration of Blood-Based Tumor-Associated Genomic and Lipidomic Profiles Using Machine Learning Models in Metastatic Prostate Cancer

PURPOSE

To determine prognostic and predictive clinical outcomes in metastatic hormone-sensitive prostate cancer (mHSPC) and metastatic castrate-resistant prostate cancer (mCRPC) on the basis of a combination of plasma-derived genomic alterations and lipid features in a longitudinal cohort of patients with advanced prostate cancer.

METHODS

A multifeature classifier was constructed to predict clinical outcomes using plasma-based genomic alterations detected in 120 genes and 772 lipidomic species as informative features in a cohort of 71 patients with mHSPC and 144 patients with mCRPC. Outcomes of interest were collected over 11 years of follow-up. These included in mHSPC state early failure of androgen-deprivation therapy (ADT) and exceptional responders to ADT; early death (poor prognosis) and long-term survivors in mCRPC state. The approach was to build binary classification models that identified discriminative candidates with optimal weights to predict outcomes. To achieve this, we built multi-omic feature-based classifiers using traditional machine learning (ML) methods, including logistic regression with sparse regularization, multi-kernel Gaussian process regression, and support vector machines.

RESULTS

The levels of specific ceramides (d18:1/14:0 and d18:1/17:0), and the presence of CHEK2 mutations, AR amplification, and RB1 deletion were identified as the most crucial factors associated with clinical outcomes. Using ML models, the optimal multi-omics feature combination determined resulted in AUC scores of 0.751 for predicting mHSPC survival and 0.638 for predicting ADT failure; and in mCRPC state, 0.687 for prognostication and 0.727 for exceptional survival. The models were observed to be superior than using a limited candidate number of features for developing multi-omic prognostic and predictive signatures.

CONCLUSION

Using a ML approach that incorporates multiple omic features improves the prediction accuracy for metastatic prostate cancer outcomes significantly. Validation of these models will be needed in independent data sets in future.

Guidelines for genetic testing in prostate cancer: a scoping review

BACKGROUND

Genetic testing, to identify pathogenic or likely pathogenic variants in prostate cancer, is valuable in guiding treatment decisions for men with prostate cancer and to inform cancer prevention and early detection options for their immediate blood relatives. There are various guidelines and consensus statements for genetic testing in prostate cancer. Our aim is to review genetic testing recommendations across current guidelines and consensus statements and the level of evidence supporting those recommendations.

METHODS

A scoping review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension for scoping review (PRISMA-ScR) guidelines. Electronic database searches and manual searches of grey literature, including websites of key organisations were conducted. Using the Population, Concept, Context (PCC) framework, this scoping review included: men with prostate cancer or men at high risk of prostate cancer and their biological families; existing guidelines and consensus statements with supporting evidence for genetic testing of men with prostate cancer from any geographical location worldwide.

RESULTS

Of the 660 citations identified, 23 guidelines and consensus statements met the inclusion criteria for the scoping review. Based on different levels of evidence about who should be tested and how, a diverse range of recommendations were identified. There was general consensus among the guidelines and consensus statements that men with metastatic disease be offered genetic testing; however, there was less consensus in relation to genetic testing in localised prostate cancer. While there was some consensus in relation to which genes to test, recommendations varied regarding who to test, testing methods and implementation.

CONCLUSION

While genetic testing in prostate cancer is routinely recommended and numerous guidelines exist, there is still considerable lack of consensus regarding who should be tested and how they should be tested. Further evidence is needed to inform value-based genetic testing strategies for implementation in practice.

Testosterone suppression plus enzalutamide versus testosterone suppression plus standard antiandrogen therapy for metastatic hormone-sensitive prostate cancer (ENZAMET): an international, open-label, randomised, phase 3 trial

BACKGROUND

The interim analysis of the ENZAMET trial of testosterone suppression plus either enzalutamide or standard nonsteroidal antiandrogen therapy showed an early overall survival benefit with enzalutamide. Here, we report the planned primary overall survival analysis, with the aim of defining the benefit of enzalutamide treatment in different prognostic subgroups (synchronous and metachronous high-volume or low-volume disease) and in those who received concurrent docetaxel.

METHODS

ENZAMET is an international, open-label, randomised, phase 3 trial conducted at 83 sites (including clinics, hospitals, and university centres) in Australia, Canada, Ireland, New Zealand, the UK, and the USA. Eligible participants were males aged 18 years or older with metastatic, hormone-sensitive prostate adenocarcinoma evident on CT or bone scanning with ^99mTc and an Eastern Cooperative Oncology Group performance status score of 0-2. Participants were randomly assigned (1:1), using a centralised web-based system and stratified by volume of disease, planned use of concurrent docetaxel and bone antiresorptive therapy, comorbidities, and study site, to receive testosterone suppression plus oral enzalutamide (160 mg once per day) or a weaker standard oral non-steroidal antiandrogen (bicalutamide, nilutamide, or flutamide; control group) until clinical disease progression or prohibitive toxicity. Testosterone suppression was allowed up to 12 weeks before randomisation and for up to 24 months as adjuvant therapy. Concurrent docetaxel (75 mg/m² intravenously) was allowed for up to six cycles once every 3 weeks, at the discretion of participants and physicians. The primary endpoint was overall survival in the intention-to-treat population. This planned analysis was triggered by reaching 470 deaths. This study is registered with ClinicalTrials.gov, NCT02446405, ANZCTR, ACTRN12614000110684, and EudraCT, 2014-003190-42.

FINDINGS

Between March 31, 2014, and March 24, 2017, 1125 participants were randomly assigned to receive non-steroidal antiandrogen (n=562; control group) or enzalutamide (n=563). The median age was 69 years (IQR 63-74). This analysis was triggered on Jan 19, 2022, and an updated survival status identified a total of 476 (42%) deaths. After a median follow-up of 68 months (IQR 67-69), the median overall survival was not reached (hazard ratio 0·70 [95% CI 0·58-0·84]; p<0·0001), with 5-year overall survival of 57% (0·53-0·61) in the control group and 67% (0·63-0·70) in the enzalutamide group. Overall survival benefits with enzalutamide were consistent across predefined prognostic subgroups and planned use of concurrent docetaxel. The most common grade 3-4 adverse events were febrile neutropenia associated with docetaxel use (33 [6%] of 558 in the control group vs 37 [6%] of 563 in the enzalutamide group), fatigue (four [1%] vs 33 [6%]), and hypertension (31 [6%] vs 59 [10%]). The incidence of grade 1-3 memory impairment was 25 (4%) versus 75 (13%). No deaths were attributed to study treatment.

INTERPRETATION

The addition of enzalutamide to standard of care showed sustained improvement in overall survival for patients with metastatic hormone-sensitive prostate cancer and should be considered as a treatment option for eligible patients.

FUNDING

Astellas Pharma.

Characteristics of immune-infiltrating cells in the tumor microenvironment of appendiceal cancer with peritoneal disease

217

Background: Appendiceal cancers (AC) are rare, associated with peritoneal metastases, and respond poorly to current systemic treatments. There are limited studies on the characteristics and prognostic impact of infiltrating immune cells within the tumour microenvironment (TME) of AC with peritoneal metastases. Infiltrating immune cells are associated with survival outcomes and predict the effectiveness of immunotherapies in solid tumours. Different definitions have been developed to describe infiltrating immune cells and associated structures such as tertiary lymphoid aggregates (TLS). The aim of our study was to describe the immune TME in patients with AC peritoneal metastases to understand mechanisms of sensitivity and resistance to chemoimmunotherapies. Methods: Fresh tissue was collected during cytoreductive surgery from consenting patients with AC with peritoneal disease (Jul 2020-Feb 2022). Uncultured Day 0 tissues were fixed in formalin prior to paraffin embedding (FFPE). Haematoxylin and eosin (H&E) staining was performed on sections of FFPE tissue. Sections were evaluated by light microscopy for the presence of immune cells based on morphological appearance. Patterns of infiltrating immune cells were classified based on location (peritumoural, intratumoural, perimucinous, stromal), and aggregation (none, immature, mature). Immune cells forming aggregates were counted and the diameter of aggregates measured using QuPath. Results: We evaluated 25 patients with AC peritoneal disease during the study period. Immune cells were detected in tissues from all except 3 patients; 16 cases (78 immune areas) were low grade (LG) disease of primary appendiceal mucinous neoplasms, and 6 cases (29 immune areas) were high grade (HG) from primary appendiceal adenocarcinomas (Table). Immune cell aggregates had a median diameter of 209 mm (75-491) and median cell count of 892 cells (46-6490). Conclusions: This study represents the first formal description and characterisation of infiltrating immune cells in appendiceal cancer peritoneal metastases. Perimucinous immune cells were not observed in HG disease despite presence of mucin. Intratumoural immune cells were not observed in LG disease, consistent with these tumours being more resistant to chemotherapy. We plan ongoing work correlating the immune features with clinical outcomes alongside immunohistochemical and transcriptomic characterisation of the aggregates. [Table: see text]

Updated overall survival outcomes in ENZAMET (ANZUP 1304), an international, cooperative group trial of enzalutamide in metastatic hormone-sensitive prostate cancer (mHSPC)

LBA5004

Background: The first planned interim analysis of ENZAMET, with 243 deaths after a median follow-up of 34 months, revealed a clinically meaningful overall survival benefit in mHSPC with the addition of enzalutamide to standard of care (hazard ratio 0.67, 95% CI 0.52 to 0.86, p=0.002, Davis et al, NEJM 2019). We now present updated overall survival (OS) findings from the prespecified analysis triggered to occur after 470 deaths. Methods: We randomly assigned participants (pts) with mHSPC to treatment with testosterone suppression (TS) plus either a conventional non-steroidal anti-androgen (NSAA) or enzalutamide. Stratification factors included age, volume of disease (high vs low according to the CHAARTED definition), and planned use of concurrent docetaxel assigned by the treating physician (docetaxel yes vs no). Results: We randomized 1125 pts with a median age of 69 years, including 503 in the docetaxel stratum, and 602 with high volume metastatic disease. OS results in the table below are based on 476 deaths, a median follow-up of 68 months, and a cut-off date of 19JAN2022. The hazard rate for death was 30% lower among all those assigned enzalutamide versus control (p<0.0001). Outcomes by volume status are shown (Table) as well as the subgroups of interest with M1 high or low volume disease at diagnosis selected for concurrent docetaxel. Conclusions: Enzalutamide added to TS, compared with an active comparator of NSAA, provided clinically meaningful improvements in OS for the combined overall cohort, which persisted with an additional 3 years of follow-up. The benefits were more pronounced in pts with low volume disease, and were also seen in the subgroup with M1 high volume mHSPC despite the relatively high survival with TS+docetaxel+NSAA. ENZAMET was led by ANZUP Cancer Trials Group and the University of Sydney NHMRC Clinical Trials Centre, with funding support from Astellas. Clinical trial information: NCT02446405. [Table: see text]

Outcomes of appendiceal cancer treated at a state peritonectomy service

3629

Background: Appendiceal cancers (AC) are rare with varied prognosis. Nomenclature refined by the WHO 2019 classification is: appendiceal mucinous neoplasms (AMNs), adenocarcinomas (AA) including mucinous (MAC), not otherwise specified (ANOS), signet ring (SRC) and goblet cell (GCA), and neuroendocrine tumours (NET). Cytoreductive surgery and heated intraperitoneal chemotherapy (CRS+HIPEC) is the definitive treatment. The role of chemotherapy remains unclear with conflicting outcomes and there is need to delineate the optimal regimen in different disease settings. The aim of this study was to evaluate AC treatment and clinical outcomes by the WHO 2019 classification and analyse the impact of perioperative chemotherapy. Methods: We reviewed prospective data from the database at an Australian state peritonectomy service, Apr 2017-Dec 2021. Variables included demographics, tumour characteristics, treatment details and survival outcomes. Analysis was by the Kaplan-Meier method using the log-rank test for statistical comparison (SPSSv27). Results: 115 patients (of 207 referred) with confirmed AC proceeded to CRS. Histopathology comprised 49 AMNs (43%), 62 (63%) AA, 3 SRCs and 1 NET. The mean age was 56y (21-78), 53% female. 94% had CRS+HIPEC (Mitomycin 85%). 70% had cytoreductive score 0. The median peritoneal cancer index was 23 (0-39). 20 (17%) had localised (M0) disease, 10 acellular mucin (M1a) and 85 (74%) metastases (M1b/c). 71% were lymph node negative (N0). 40% had chemotherapy (oxaliplatin/5-fluorouracil 57%). 8 of 15 who had molecular testing had a KRAS mutation. Median follow-up was 26m (1.9-167). The table shows univariate survival analysis. Conclusions: This is the first study evaluating outcomes of perioperative chemotherapy for AC in a cohort of patients since the WHO 2019 classification. MAC have worse survival compared to ANOS, but similar to GCAs. Peritoneal acellular mucin has a similarly improved prognosis to patients with no peritoneal disease compared to those with cellular disease. Chemotherapy demonstrated worse survival compared to no chemotherapy, also seen in the literature and likely influenced by selection of more aggressive disease. There is a need to develop biomarkers and better treatments to improve the survival of these patients. Further multivariate analysis for prognostic and predictive factors is planned.[Table: see text]

DASL-HiCaP: Darolutamide augments standard therapy for localized very high-risk cancer of the prostate (ANZUP1801)—A randomized phase 3, double-blind, placebo-controlled trial of adding darolutamide to androgen deprivation therapy and definitive or salvage radiation

TPS5103

Background: Radiation therapy (RT), plus androgen deprivation therapy (ADT) with a luteinizing hormone releasing hormone analog (LHRHA), is standard of care for men with very high-risk localized prostate cancer (PC), or with very high-risk features and persistent PSA after radical prostatectomy (RP). Despite this, incurable distant metastases develop within 5 years in 15% of men with very high-risk features. Darolutamide is a structurally distinct oral androgen receptor antagonist with low blood-brain-barrier penetration, a demonstrated favorable safety profile, and low potential for drug-drug interactions. Our aim is to determine the efficacy of adding darolutamide to ADT and RT in the setting of either primary definitive therapy, or salvage therapy for very high-risk PC. Methods: This study is a randomized (1:1), phase 3, placebo-controlled, double-blind trial for men planned for RT who have very high-risk localized PC on conventional imaging; or very high-risk features with PSA persistence or rise within one year following RP. The trial is stratified by: RP; use of adjuvant docetaxel; pelvic nodal involvement. 1100 participants will be randomized to darolutamide 600 mg or placebo twice daily for 96 weeks. Participants will receive LHRHA for 96 weeks, plus RT starting week 8-24 from randomization. Participants are allowed nonsteroidal antiandrogen in addition to LHRHA for up to 90 days prior to randomization. Early treatment with up to 6 cycles of docetaxel completed at least 4 weeks prior to RT is permitted. The primary endpoint is metastasis-free survival (ICECaP-validated), with secondary endpoints overall survival, PC-specific survival, PSA-progression free survival, time to subsequent hormonal therapy, time to castration-resistance, frequency and severity of adverse events, health related quality of life, fear of recurrence. Tertiary endpoints include incremental cost-effectiveness, and identification of prognostic and/or predictive biomarkers of treatment response, safety, and resistance to study treatment. Clinical trial information: NCT04136353.

Patient-derived explant model of appendiceal cancer

4160

Background: Appendiceal cancers (AC) are rare with 5-year survival of 15% for high grade (HG) adenocarcinomas and 75% for low grade (LG) mucinous neoplasms. There is limited literature on the AC tumour microenvironment (TME) in disease progression and drug resistance. Ex vivo cultures, such as patient derived explants (PDEs), have been used for other solid tumours to test anticancer agents, explore the TME, and are being developed as personalised models. The aim of our study was to develop a PDE model of AC, preserve the TME, study the biological profile of AC and test novel therapies. Methods: Fresh tissue was collected during cytoreductive surgery (CRS) from consenting patients with AC with peritoneal disease, Jul 2020-Mar 2021. Tissues from 10 patients were dissected and cultured as PDEs under varying conditions of tissue size, media, matrix support and duration (Table). Uncultured Day 0 tissues and PDEs were fixed in formalin prior to paraffin embedding (FFPE). Immunohistochemical staining was performed on sections of FFPE tissue to assess viability with antibodies against the tumour marker, Cytokeratin-20 (CK20), and cell death marker, cleaved caspase 3 (CC3). Tissue architecture was rated on a 4-point scale (MS, J-SS). Cancer cells were counted in 6 Day 0 samples and PDEs from 3 patients using QuPath v0.3.2. Apoptotic index (AI) was calculated as the proportion of cells positive for CC3 divided by the number of total CK20 positive cells. Results: The mean proportion of tumour and mucin in the tissues was 3% (0-60%) and 39% (0-95%) respectively. Day 0 samples were viable with mean AI of cancer cells 7% (0-4%). Tissue architecture was maintained, as compared to Day 0 control, for varying sizes of PDE and culture durations up to 4d. More small or medium-sized PDEs had improved architecture compared to large sized PDEs (Table). PDEs at 4d had poorer architecture compared to at 1-3d. There was improved architecture in PDEs using enriched media with support factors compared to base media, and in specimens with matrix support compared to none. The mean AI of PDE cancer cells was 21% (0-92%) and 51% of PDEs had no cancer cell death. Conclusions: This is the first study demonstrating that AC tissue is amenable to ex vivo culture as PDEs. The optimal PDE model was <10mm tissue placed on a gelatine sponge in enriched media for 1-3d. PDEs had preserved tissue architecture and viability compared to uncultured tissue. Protein expression was in keeping with the original tumour. We plan to use this model to test anticancer agents and explore the TME of AC.[Table: see text]

A phase 1 study of AMG 509 in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

TPS5101

Background: Six-transmembrane epithelial antigen of prostate 1 (STEAP1) is overexpressed on the surface of prostate cancer cells with low or no expression on normal tissue. AMG 509 is a bispecific XmAb 2+1 T-cell engager that simultaneously binds to STEAP1 on tumor cells and the CD3 complex on T cells resulting in T-cell mediated lysis of STEAP1-expressing cells. AMG 509 demonstrated significant antitumor activity in preclinical prostate cancer models. Methods: This 4-part, first-in-human study will evaluate AMG 509 in pts with mCRPC previously treated with novel hormonal therapy (NHT) and will assess the safety, tolerability, pharmacokinetics (PK), and efficacy of AMG 509 to establish the maximum tolerated dose (MTD) and/or the recommended phase 2 dose (RP2D). Part 1 is currently enrolling pts previously treated with NHT and up to 2 prior taxanes. As of 31 January 2022, 60 of up to 110 pts have been enrolled for treatment with intravenous (IV) AMG 509 with initial inpatient dosing followed by outpatient treatment. Part 2 will evaluate subcutaneous dosing of AMG 509 in the same patient population as in Part 1. Part 3 will explore AMG 509 IV dosing in chemotherapy-naïve pts who have been treated previously with one NHT and will provide additional data on the safety, PK, efficacy, pharmacodynamics, and correlative biomarkers at the MTD or RP2D determined in Part 1. Part 4 will evaluate the combination of AMG 509 with abiraterone (Part 4A) or enzalutamide (Part 4B) in pts previously treated with one NHT and up to 1 prior taxane for castration-sensitive disease. Primary outcome measures include dose-limiting toxicities, treatment-emergent and treatment-related adverse events, and change in clinical and laboratory parameters. Key secondary outcome measures include PK, objective response per RECIST 1.1, prostate-specific antigen response, progression-free survival, and overall survival. Key inclusion criteria are men ≥18 years of age with pathologically confirmed mCRPC, refractoriness to NHT, evidence of progressive disease, and ECOG performance status of 0–1. Key exclusion criteria are pure small cell or neuroendocrine carcinoma of the prostate, untreated CNS metastases or leptomeningeal disease, recent anticancer therapy or immunotherapy within 4 weeks of start of first dose not including luteinizing hormone-releasing hormone/gonadotropin-releasing hormone analogue (agonist/antagonist) therapy, radiation therapy, and a history of or current autoimmune disease or any disease requiring chronic immunosuppressive therapy. The trial is being carried out in investigative sites in North America, Australia, Asia, and Europe. The study opened in January 2020 and is recruiting pts for the dose exploration phase of Part 1; parts 2 and 4 are open for enrollment. Part 3 will be initiated once the MTD and/or RP2D have been determined in Part 1. Clinical trial information: NCT04221542.

Circulating tumour cells (CTCs) and PSMA PET correlates in the phase I PRINCE trial of 177Lu-PSMA-617 plus pembrolizumab for metastatic castration resistant prostate cancer (mCRPC)

5027

Background: The Phase I PRINCE trial (NCT03658447) is evaluating the efficacy of 177Lu-PSMA-617 plus pembrolizumab for mCRPC. The utility of serial monitoring of CTCs and PET as biomarkers of prognosis and clinical benefit of 177Lu-PSMA-617-based therapy remains unknown. Methods: 36 of 37 pts with high PSMA expression on PSMA PET underwent serial CTC collections in conjunction with PSMA PET at baseline, every 12 weeks for 48 weeks and every 24 weeks thereafter. CK+, CD45- CTCs were enumerated from 3ml of blood and stained for PSMA (Epic Sciences platform). Associations between PSMA+ CTC counts, PET molecular tumor volume (MTV), total lesional activity (TLA; MTVxSUVmean) were assessed by Spearman correlation. Cox models assessed the association of CTC and PSMA PET parameters with radiographic progression-free survival (rPFS) and PSA PFS. A subset of pre-treatment CTCs underwent single cell low-pass whole genome sequencing to characterize copy number aberrations. Results: 32/36 pt (89%) had detectable CTCs (median 7, range 0-514) with 23 (64%) being PSMA+ (median 1, range 0-224) at baseline. At w12, 23/33 (70%) had CTCs detected with 10 (30%) being PSMA+. Baseline PSMA+ CTC count and MTV were moderately correlated (rs= 0.57, p < 0.001). Of 22 evaluable pts with baseline PSMA+ CTC, 18 (82%) showed decrease by w12 with clearance in 13. This paralleled reductions in MTV (-18% med relative change, IQR: -57 to -1) and TLA (-48% med relative change, IQR: -77 to -28). Total CTC and PSMA+ CTC counts at baseline, and PET parameters were not associated with PSA PFS or rPFS. Clearance of PSMA+ CTC by w12 (13/22 pts) was associated with improved rPFS (med NR vs 3.0 mos, HR 0.23, 95%CI 0.07-0.74, p = 0.007) and PSA PFS (med 11.2 vs 3.5 mos, HR 0.28, 95%CI 0.11-0.73, p = 0.006). Persisting PSMA-neg CTCs at w12 trended to worse rPFS (med 4.1 vs 12.3 mos, p = 0.11) and PSA PFS (med 5.1 vs 12.3 mos, p = 0.07). Of pts not progressing by w12, decrease in PSA (HR 0.83 per 10% decrease, 95%CI 0.74-0.93, p < 0.001), MTV (HR 0.85 per 10% decrease, 95%CI 0.75-0.96, p = 0.008), MTV > 30% decrease (HR 0.30, 95% CI 0.08-1.08, p = 0.05) and TLA (HR 0.88 per 10% decrease, 95%CI 0.78-1.00, p = 0.04) associated with improved rPFS beyond w12. Pre-treatment CTCs (18 pts) exhibited genomic heterogeneity and frequent loss of PTEN, TP53 and RB1. Pts with compound TP53 and RB1 loss at baseline nonetheless had PSMA+ CTCs in high proportion (med 91.3% of total CTCs). Conclusions: PSMA PET-positive mCRPC is associated with high rates of PSMA+ CTCs which decline with 177Lu-PSMA-617 plus pembrolizumab in parallel with PSMA MTV/TLA. Despite imaging suitability for therapy, CTCs had heterogenous PSMA expression and genomic alterations associated with aggressive disease. Early changes in PSMA+ CTCs and MTV/TLA were associated with outcomes and may aid in determining clinical activity of LuPSMA-based therapy.

PRINCE: Phase I trial of 177Lu-PSMA-617 in combination with pembrolizumab in patients with metastatic castration-resistant prostate cancer (mCRPC)

5017

Background: The VISION and TheraP trials have established the safety and efficacy of 177Lu-PSMA-617 in mCRPC with a 50% PSA response rate (PSA50-RR) of 46% and 66% and median progression free survival (PFS) of 8.7 and 5.1 months, respectively. More effective treatments are required as disease progression remains universal. Immunotherapy has limited single-agent efficacy in mCRPC. We hypothesise that by potentially inducing immunogenic cell death, 177Lu-PSMA-617 may act synergistically with pembrolizumab, an anti-programmed death 1 inhibitor, to enhance the depth and durability of response. PRINCE is a Phase I trial evaluating the safety and efficacy of this combination. Methods: mCRPC patients with high PSMA expression (SUVmax ≥ 20 in an index lesion, SUVmax > 10 for all lesions ≥ 10mm), and no FDG+ve/PSMA-ve lesions on paired baseline PET/CT screening, received up to 6 cycles of 177Lu-PSMA-617 (starting at 8.5 GBq, reducing by 0.5 GBq with each cycle) every 6 weeks in conjunction with 200mg of pembrolizumab every 3 weeks for up to 2 years. Response evaluation was undertaken as per PCWG3 and RECIST criteria. Co-primary endpoints were safety and PSA50-RR. Secondary endpoints included PSA-PFS, radiographic PFS (rPFS), overall survival (OS), and patient reported outcomes (PROs). This analysis was undertaken after the last patient had 12 months follow-up. Results: 37 patients (median age 72 years; prior docetaxel 73%; prior androgen receptor targeted agent 100%) received a median of 5 cycles (range: 2 to 6) of 177Lu-PSMA-617 and 12 doses (range: 6 to 19) of pembrolizumab. The median follow up was 16 months. PSA50-RR was 76% (28/37 [95% CI 59-88]) and 7/10 (70%) patients with RECIST-measurable disease had a partial response. Median rPFS, PSA-PFS and OS was 11.2 months (95% CI: 5.1-14.1), 8.2 months (95% CI: 5.1-11.2) and 17.8 months (95% CI:13.4-not estimable). 12-month rPFS and OS was 38% (95% CI: 22-54) and 83% (95% CI: 67-92), respectively. Common (≥10%) treatment-related adverse events (TRAE) were mainly Grade (G) 1-2, including xerostomia (78%), fatigue (43%), pruritus (27%), nausea (27%), rash (24%), diarrhoea (14%), anorexia (16%), thrombocytopenia (16%), elevated ALT (11%), arthralgia (11%) and a flare in bone pain (11%). Haematologic TRAEs included G2-3 anaemia (8%), G1-2 thrombocytopenia (16%), and G1 neutropenia (3%). G3 immune-related AEs occurred in 10 (27%) patients with no dominant manifestation. 5 (14%) patients discontinued pembrolizumab due to toxicity. PROs including BPI-SF and FACT-P were stable throughout the study. Conclusions: The combination of 177Lu-PSMA-617 and pembrolizumab had promising activity. Toxicities were generally consistent with those of single-agent 177Lu-PSMA-617 and pembrolizumab and were not clearly augmented by combination use. No new safety concerns were observed. Clinical trial information: NCT03658447.

DASL-HiCaP: Darolutamide augments standard therapy for localized very high-risk cancer of the prostate (ANZUP1801). a randomized phase 3 double-blind, placebo-controlled trial of adding darolutamide to androgen deprivation therapy and definitive or salvage radiation

TPS284

Background: Radiation therapy (RT), plus androgen deprivation therapy (ADT) with a luteinizing hormone releasing hormone analog (LHRHA), is standard of care for men with very high-risk localized prostate cancer (PC), or with very high-risk features and persistent PSA after radical prostatectomy (RP). Despite this, incurable distant metastases develop within 5 years in 15% of men with very high-risk features. Darolutamide is a structurally distinct oral androgen receptor antagonist with low blood-brain-barrier penetration, a demonstrated favorable safety profile, and low potential for drug-drug interactions. Our aim is to determine the efficacy of adding darolutamide to ADT and RT in the setting of either primary definitive therapy, or salvage therapy for very high-risk PC. Methods: This study is a randomized (1:1), phase 3, placebo-controlled, double-blind international trial for men planned for RT who have very high-risk localized PC on conventional imaging; or very high-risk features with PSA persistence or rise within one year following RP. The trial is stratified by: RP; use of adjuvant docetaxel; pelvic nodal involvement. 1100 participants will be randomized to darolutamide 600 mg or placebo twice daily for 96 weeks in combination with SOC: LHRHA for 96 weeks, plus RT starting week 8-24 from randomization. Participants are allowed nonsteroidal antiandrogen in addition to LHRHA for up to 90 days prior to randomization. Early treatment with up to 6 cycles of docetaxel completed at least 4 weeks prior to RT is permitted. The primary endpoint is metastasis-free survival (ICECaP-validated), with secondary endpoints overall survival, PC-specific survival, PSA-progression free survival, time to subsequent hormonal therapy, time to castration-resistance, frequency and severity of adverse events, health related quality of life, fear of recurrence. Tertiary endpoints include incremental cost-effectiveness, and identification of prognostic and/or predictive biomarkers of treatment response, safety, and resistance to study treatment. Clinical trial information: NCT04136353.

Modulation of the plasma lipidomic profile with simvastatin in metastatic castration-resistant prostate cancer (mCRPC)

154

Background: Elevated circulating sphingolipids are associated with poorer outcomes across the natural history of prostate cancer (PC), including metastatic relapse in localised PC, earlier androgen deprivation failure in metastatic hormone-sensitive PC, and shorter overall survival (OS) in mCRPC. We have derived and validated a poor prognostic 3-lipid signature (3LS) [consisting of ceramide Cer(d18:1/24:1), sphingomyelin SM(d18:2/16:0) and phosphatidylcholine PC(16:0/16:0)], which was independently associated with shorter radiographic progression-free survival (rPFS) and OS in men with mCRPC commencing taxanes or androgen receptor signaling inhibitors (ARSI). Statins significantly reduce plasma levels of ceramides, sphingomyelin and cholesterol in cardiovascular disease. We hypothesised that this therapy could change the poor prognostic lipid profile of patients with mCRPC. This study assessed whether the addition of simvastatin to standard treatment for mCRPC modulates the circulating lipidomic profile. Methods: This investigator-initiated, multi-centre, single arm, pilot study enrolled men with mCRPC commencing taxanes or ARSI for disease progression, who were not on a lipid-lowering agent. Men were treated with simvastatin 40mg orally once daily for 12 weeks, commencing on day 1 of treatment for mCRPC. Plasma was taken at baseline and after 12 weeks of simvastatin, and underwent lipidomic profiling of ̃800 lipids. Differences in lipid levels between baseline and post-simvastatin samples and between those with and without the 3LS were assessed using t-tests. Results: 27 men (74% on taxanes, 26% on ARSI) were recruited between May 2018 to March 2021. 46% of the men had the poor prognostic 3LS at baseline, of whom 45% lost the 3LS after simvastatin. Comparison between all paired baseline and post-simvastatin samples showed significant reduction (p < 0.05) in free cholesterol, cholesteryl esters and some sphingolipids (sphingomyelins, hexosylceramides) with simvastatin treatment. Baseline profiles with the 3LS displayed significantly higher levels (p < 0.05) of ceramides, hexosylceramides and sphingomyelins, relative to baseline profiles without the 3LS. Men who lost the 3LS after treatment (n = 5) demonstrated significant reductions in ceramides (23-45%, p≤0.046), hexosylceramides (27-52%, p≤0.049) and sphingomyelins (28-44%, p≤0.047). These changes were not seen in men with persistent 3LS after treatment (n = 6). Conclusions: Simvastatin in addition to standard treatment for mCRPC can modulate the circulating lipidomic profile and eliminate the presence of a poor prognostic 3LS in 45% of participants with the 3LS. Further prospective randomised control studies are required to determine if modulation of the 3LS by simvastatin can improve clinical outcomes. Clinical trial information: ACTRN12617000965303.

CYCLONE 2: A phase 2/3, randomized, placebo-controlled study of abiraterone acetate plus prednisone with or without abemaciclib in patients with metastatic castration-resistant prostate cancer

TPS198

Background: Despite recent advances, nearly all patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) experience disease progression and cancer-specific mortality. Persistent or reactivated androgen receptor (AR) signaling and/or activation of pathways in cross-talk with AR signaling are key drivers of mCRPC progression. Evidence suggests that AR signaling promotes translation of D-type cyclins resulting in cyclin-dependent kinase 4 and 6 (CDK4&6) activation and cell cycle progression. Abemaciclib is an oral selective inhibitor of CDK4&6 dosed on a continuous schedule, that is FDA-approved in combination with endocrine therapy or as monotherapy to treat HR+, HER2- metastatic breast cancer pts. Preclinical studies with prostate cancer cell lines and xenograft models showed that abemaciclib induces cell cycle arrest and tumor growth inhibition. The hypothesis is that addition of abemaciclib to AR targeted therapy may be an effective treatment for mCRPC pts. Methods: CYCLONE 2 (NCT03706365) is a phase 2/3, randomized, double-blind, multicenter, placebo-controlled study to assess the safety and efficacy of abemaciclib in combination with abiraterone acetate plus prednisone (AA+P) in pts with mCRPC. CYCLONE 2 is an adaptive study which is designed in three parts. Part 1 is a 30-patient safety lead-in to determine the recommended phase 2 dose (RP2D; 150 mg or 200 mg, twice daily) of abemaciclib in combination with AA (1000 mg, once daily) + P (5 mg, twice daily). In part 2, 150 pts are randomized 1:1 to AA+P with abemaciclib at the RP2D or placebo. The study expands to enroll an additional 170 pts in Part 3 if prespecified expansion criteria are met at a planned adaptive interim analysis performed by an independent data monitoring committee (IDMC). Pts with mCRPC evidenced by radiographic and/or PSA progression during continuous ADT are eligible. Prior docetaxel for mHSPC is permitted. Systemic anti-cancer therapy for mCRPC and prior novel hormonal agents are exclusionary. The primary objective is radiographic progression free survival (rPFS; per RECIST1.1 for soft tissue and PCWG3 for bone). Secondary objectives include safety, objective response rate, duration of response, time to symptomatic and PSA progression, overall survival, and pharmacokinetics. Status: Enrollment in Part 1 & 2 is completed. Based on the recommendation from the IDMC, Part 3 was opened in June 2021 and enrolls pts from about 112 sites across 12 countries. Clinical trial information: NCT03706365.

Prognostic and predictive utility of DNA damage response (DDR) aberrations detected in cell-free DNA (cfDNA) in metastatic castration-resistant prostate cancer (mCRPC)

153

Background: The prognostic significance of DDR alterations in mCRPC remains unclear, with conflicting data from prior reports. Whether DDR alterations are predictive of outcomes with therapeutic agents other than PARP inhibitors in mCRPC is also poorly understood. With increasing use of molecular profiling in mCRPC, understanding the full prognostic and predictive utility of plasma DDR alterations is paramount. Methods: A next-generation sequencing Predicine liquid biopsy assay was used to profile cfDNA and germline DNA in 407 mCRPC patients (pts) from two independent international cohorts (n=162 Australia, n=245 US). DDR genes profiled were BRCA2, ATM, BRCA1, MLH1 and MSH2. Kaplan-Meier survival estimates and multivariable Cox regression analyses were used to assess associations between DDR alterations and clinical outcomes including PSA response rate (PSA RR), progression-free survival and overall survival (OS). Results: Median age was 74 (IQR 67-79), with median follow up 74 months and median OS 23 months. 65/407 (16%) harboured pathogenic DDR alterations, including 21 patients with ³1 alteration. Frequency of genomic aberrations are shown in the table. BRCA2 alterations were further classified as heterozygous loss (66%), homozygous loss (14%), monoallelic mutation (11%) and biallelic mutation/loss of heterozygosity (9%). Aberrations in any DDR gene, ATM, MLH1 + MSH2 or BRCA2 were associated with shorter OS on univariable analysis, but only any DDR or BRCA2 aberration remained significant upon adjusting for clinical prognosticators and ctDNA fraction (Table). Pre-treatment BRCA2 aberration was associated with significantly shorter OS and lower PSA RR compared to BRCA2 wt for pts receiving an AR pathway inhibitor (ARPI) (18 vs 32 months, p=0.006; 36 vs 60%, p=0.04 respectively) but not for taxane chemotherapy (17 vs 20 months, p=0.3; 45 vs 66, p=0.1 respectively). Conclusions: Detection of an aberration in any DDR gene or BRCA2 was an independent poor prognostic factor across 2 large independent cohorts of mCRPC patients. Intriguingly, patients with a BRCA2 alteration appeared to have worse outcomes with ARPI but not chemotherapy, suggesting predictive utility of DDR profiling. Our data collectively speak to the potential role of DDR alterations, in particular BRCA2, as prognostic and/ or predictive biomarkers in mCRPC.[Table: see text]

Age-based assessment of cell-free DNA genomic profiles in metastatic castration-resistant prostate cancer (mCRPC)

150

Background: With the evolving use of targeted therapies exploiting genomic vulnerabilities in mCRPC, screening patients for sensitizing alterations is of increasing relevance. However, the influence of age on the detection of relevant genomic alterations is incompletely understood. In this study, we compared the cell-free DNA (cfDNA) profiles of younger (age <70) versus older (age ≥70) men with mCRPC and assessed the relative prognostic impact of common genomic alterations. Methods: A next-generation sequencing-based Predicine cfDNA assay was used to profile 276 mCRPC patients from two independent international cohorts. The frequency of genomic alterations across age categories was compared using the chi-squared test, while circulating tumour DNA fraction (ctDNA%) was compared using the Mann–Whitney U test. Cox proportional hazards analysis with interaction testing was used to assess the association between age, genomic alteration and overall survival. Results: The median age of the combined cohort was 72 years (IQR 66-78), with 170 (62%) patients ≥70 years old. Despite differences in baseline characteristics (poorer performance status in older patients, higher Gleason score and de novo metastatic disease in younger patients), there was no significant difference in ctDNA% (median 22% vs 30%, p=0.6). We observed similar frequencies of genomic alterations across the 10 most commonly aberrant genes, including AR (<70 vs ≥70: 46% vs 49%, p=0.6), TP53 (40% vs 36%, p=0.6), BRCA2 (29% vs 21%, p=0.13) and PTEN (39% vs 35%, p=0.5). This similarity persisted when analysing mutations and copy number alterations in isolation. While driver alterations in both age categories were strongly associated with unfavourable outcomes (Table), an exploratory analysis revealed that copy number gain in PIK3CA may have a worse prognostic impact in younger men ( p for interaction = 0.03), with a lesser effect observed in AR gain ( p = 0.1) and MYC gain ( p = 0.1). Conclusions: The genomic profiles of pertinent alterations between younger and older men are comparable. Certain genomic alterations may carry a worse prognosis in younger men. Patients should be considered for precision medicine assessment and directed therapies, regardless of age. [Table: see text]

Phase IA/IB study of single-agent tislelizumab, an investigational anti-PD-1 antibody, in solid tumors

Background

The programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) axis plays a central role in suppressing antitumor immunity; axis dysregulation can be used by cancer cells to evade the immune system. Tislelizumab, an investigational monoclonal antibody with high affinity and binding specificity for PD-1, was engineered to minimize binding to FcγR on macrophages to limit antibody-dependent phagocytosis, a potential mechanism of resistance to anti-PD-1 therapy. The aim of this phase IA/IB study was to investigate the safety/tolerability, antitumor effects and optimal dose and schedule of tislelizumab in patients with advanced solid tumors.

Methods

Patients (aged ≥18 years) enrolled in phase IA received intravenous tislelizumab 0.5, 2, 5 or 10 mg/kg every 2 weeks; 2 or 5 mg/kg administered every 2 weeks or every 3 weeks; or 200 mg every 3 weeks; patients in phase IB received 5 mg/kg every 3 weeks. Primary objectives were to assess tislelizumab’s safety/tolerability profile by adverse event (AE) monitoring and antitumor activity using RECIST V.1.1. PD-L1 expression was assessed retrospectively with the VENTANA PD-L1 (SP263) Assay.

Results

Between May 2015 and October 2017, 451 patients (n=116, IA; n=335, IB) were enrolled. Fatigue (28%), nausea (25%) and decreased appetite (20%) were the most commonly reported AEs. Most AEs were grade 1–2 severity; anemia (4.9%) was the most common grade 3–4 AE. Treatment-related AEs led to discontinuation in 5.3% of patients. Grade 5 AEs were reported in 14 patients; 2 were considered related to tislelizumab. Pneumonitis (2%) and colitis (1%) were the most common serious tislelizumab-related AEs. As of May 2019, 18% of patients achieved a confirmed objective response in phase IA and 12% in phase IB; median follow-up duration was 13.6 and 7.6 months, respectively. Pharmacokinetics, safety and antitumor activity obtained from both phase IA and IB determined the tislelizumab recommended dose; ultimately, tislelizumab 200 mg intravenous every 3 weeks was the dose and schedule recommended to be taken into subsequent clinical trials.

Conclusions

Tislelizumab monotherapy demonstrated an acceptable safety/tolerability profile. Durable responses were observed in heavily pretreated patients with advanced solid tumors, supporting the evaluation of tislelizumab 200 mg every 3 weeks, as monotherapy and in combination therapy, for the treatment of solid tumors and hematological malignancies.

Trial registration number

NCT02407990.

Cryopreservation of human cancers conserves tumour heterogeneity for single-cell multi-omics analysis

BACKGROUND

High throughput single-cell RNA sequencing (scRNA-Seq) has emerged as a powerful tool for exploring cellular heterogeneity among complex human cancers. scRNA-Seq studies using fresh human surgical tissue are logistically difficult, preclude histopathological triage of samples, and limit the ability to perform batch processing. This hindrance can often introduce technical biases when integrating patient datasets and increase experimental costs. Although tissue preservation methods have been previously explored to address such issues, it is yet to be examined on complex human tissues, such as solid cancers and on high throughput scRNA-Seq platforms.

METHODS

Using the Chromium 10X platform, we sequenced a total of ~ 120,000 cells from fresh and cryopreserved replicates across three primary breast cancers, two primary prostate cancers and a cutaneous melanoma. We performed detailed analyses between cells from each condition to assess the effects of cryopreservation on cellular heterogeneity, cell quality, clustering and the identification of gene ontologies. In addition, we performed single-cell immunophenotyping using CITE-Seq on a single breast cancer sample cryopreserved as solid tissue fragments.

RESULTS

Tumour heterogeneity identified from fresh tissues was largely conserved in cryopreserved replicates. We show that sequencing of single cells prepared from cryopreserved tissue fragments or from cryopreserved cell suspensions is comparable to sequenced cells prepared from fresh tissue, with cryopreserved cell suspensions displaying higher correlations with fresh tissue in gene expression. We showed that cryopreservation had minimal impacts on the results of downstream analyses such as biological pathway enrichment. For some tumours, cryopreservation modestly increased cell stress signatures compared to freshly analysed tissue. Further, we demonstrate the advantage of cryopreserving whole-cells for detecting cell-surface proteins using CITE-Seq, which is impossible using other preservation methods such as single nuclei-sequencing.

CONCLUSIONS

We show that the viable cryopreservation of human cancers provides high-quality single-cells for multi-omics analysis. Our study guides new experimental designs for tissue biobanking for future clinical single-cell RNA sequencing studies.

Phase I study of AMG 509, a STEAP1 x CD3 T-cell recruiting XmAb 2+1 immune therapy, in patients with metastatic castration-resistant prostate cancer (mCRPC)

TPS183

Background: Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a cell surface antigen that is highly expressed in prostate cancer. AMG 509 is a potent bispecific XmAb 2+1 immune therapy designed to direct T effector cells to STEAP1-expressing cells. AMG 509 contains two identical humanized anti-STEAP1 Fab domains that bind STEAP1-expressing cells, an anti-CD3 scFv domain that binds T cells, and an Fc domain, engineered to lack effector function, that extends serum half-life. In preclinical studies, AMG 509 induced potent and specific T-cell-mediated lysis of STEAP1-expressing cancer models. Methods: This open-label, phase 1, first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK), and efficacy of AMG 509 in patients with relapsed/refractory mCRPC. The dose exploration phase (n=40) will estimate the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) using a Bayesian logistic regression model. The dose expansion phase (n=30) will confirm safety, PK, and pharmacodynamics at the MTD or RP2D and collect further safety, efficacy, and biomarker data. Efficacy will be assessed by prostate-specific antigen response, circulating tumor cell response, and objective tumor response per RECIST 1.1 with Prostate Cancer Working Group 3 modifications. Key inclusion criteria: men ≥18 years with histologically/cytologically confirmed mCRPC who are refractory to novel hormonal therapy (e.g., abiraterone and/or enzalutamide) and have failed 1–2 taxane regimens or are medically unsuitable for or have refused taxanes; ongoing castration with total serum testosterone ≤50 ng/dL; evidence of progressive disease; ECOG performance status 0–1; life expectancy ≥3 months; and adequate hematologic, renal, hepatic, and cardiac function. In the dose exploration phase, novel antiandrogen therapy must have been given in the metastatic setting. Key exclusion criteria: pure small cell or neuroendocrine carcinoma of the prostate; untreated CNS metastases or leptomeningeal disease; any anticancer therapy or immunotherapy, radiation therapy, or major surgery <4 weeks from first dose; history of or current autoimmune disease or any disease requiring immunosuppressive therapy (≤10 mg/d prednisone permitted); prior STEAP1-targeted therapy; infection requiring IV antimicrobials <7 days from first dose. The study opened in January 2020 and is recruiting patients. ClinicalTrials.gov: NCT04221542. 2020 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2020 ASCO Annual Meeting. All rights reserved. Clinical trial information: NCT04221542.

Plasma cell-free DNA profiling of PI3K/Akt pathway aberrations in two multi-institutional independent metastatic castration-resistant prostate cancer (mCRPC) cohorts

159

Background: Tumour tissue from metastatic castration-resistant prostate cancer (mCRPC) harbors frequent copy number variations (CNVs) in the phosphatidylinositol-3-kinase (PI3K)/Akt-signaling pathway. However, identifying CNVs in plasma cell-free DNA (cfDNA) has proven challenging. With emerging data supporting Akt inhibition in PTEN-deficient mCRPC, cfDNA assays for robustly identifying PI3K/Akt pathway aberrations including CNVs are urgently required. Methods: In this multi-institutional prospective biomarker study, we used the Predicine cfDNA assay, optimised for CNV detection, to perform targeted sequencing in 231 mCRPC patients in two independent cohorts (Australian, n = 78; US, n = 153). Kaplan-Meier survival estimates and multivariable Cox regression analysis were used to assess associations between genomic aberrations and progression-free survival (PFS) and overall survival (OS). Results: PTEN loss and PIK3CA gain were detected in 37% (85/231) and 17% (39/231) of patients, respectively. Poorer outcomes were observed in patients with PI3K/Akt pathway aberrations, including those with dual PTEN loss and PIK3CA gain (HR 2.3, 95% CI 1.2-4.4). Similarly, cumulative CNV burden in the PI3K/Akt and AR pathways (0 vs 1 vs ≥2 CNVs in Australian cohort: median OS 33.5 vs 17.2 vs 9.7 months, p< 0.001; 0 vs 1 vs ≥2 CNVs in US cohort: median OS 35.5 vs 14.3 vs 9.2 months, p< 0.001) was associated with significantly worse clinical outcomes. Notably, 21% (31/146) of PTEN-neutral patients harbored other alterations in the PI3K/Akt pathway. Conclusions: Our cfDNA assay readily detected PI3K/Akt pathway CNVs, with the prevalence of PTEN loss comparable to prior tissue sequencing studies. CNVs in the PI3K/Akt pathway were associated with deleterious clinical outcomes, especially when concurrent with AR gain. Additional PI3K/Akt pathway aberrations were found in approximately one-fifth of PTEN-neutral mCRPC. Collectively, our data demonstrate the potential utility of profiling cfDNA to facilitate and optimize patient selection for treatment with Akt inhibitors in mCRPC. [Table: see text]

DASL-HiCaP: Darolutamide augments standard therapy for localized very high-risk cancer of the prostate (ANZUP1801)—A randomized phase III double-blind, placebo-controlled trial of adding darolutamide to androgen deprivation therapy and definitive or salvage radiation

TPS266

Background: Radiation therapy (RT), plus androgen deprivation therapy (ADT) with a luteinizing hormone releasing hormone analogue (LHRHA), is standard of care for men with very high-risk localized prostate cancer (PC), or with very high- risk features and persistent PSA after radical prostatectomy (RP). Despite this, incurable distant metastases develop within 5 years in 15% of men with very high-risk features. Darolutamide is a structurally distinct oral androgen receptor antagonist with low blood-brain-barrier penetration, a demonstrated favorable safety profile and low potential for drug-drug interactions. Our aim is to determine the efficacy of adding darolutamide to ADT and RT in the setting of either primary definitive therapy, or adjuvant therapy for very high-risk PC. Methods: This study is a randomized (1:1) phase III placebo-controlled, double-blind trial for men planned for RT who have very high-risk localized PC; or very high-risk features with PSA persistence or rise within one year following RP. The trial will be stratified by: RP; use of adjuvant docetaxel; pelvic nodal involvement. 1100 participants will be randomized to darolutamide 600 mg or placebo twice daily for 96 weeks. Participants will receive LHRHA for 96 weeks, plus RT starting week 8-24 from randomisation. Participants are allowed nonsteroidal antiandrogen (up to 90 days) in addition to LHRHA up until randomisation. Early treatment with up to 6 cycles of docetaxel completed at least 4 weeks prior to RT is permitted. The primary endpoint is metastasis-free survival (ICECaP-validated), with secondary endpoints overall survival, PC-specific survival, PSA-progression free survival, time to subsequent hormonal therapy, time to castration-resistance, frequency and severity of adverse events, health related quality of life, fear of recurrence. Tertiary endpoints include incremental cost-effectiveness, and identification of prognostic and/or predictive biomarkers of treatment response, safety and resistance to study treatment. Clinical trial information: NCT04136353.

CheckMate 9KD Arm B final analysis: Efficacy and safety of nivolumab plus docetaxel for chemotherapy-naïve metastatic castration-resistant prostate cancer

12

Background: CheckMate 9KD (NCT03338790) is a phase 2 trial of nivolumab (NIVO; anti-PD-1) in combination with rucaparib, docetaxel (DOCE), or enzalutamide for patients with metastatic castration-resistant prostate cancer (mCRPC). DOCE is a standard-of-care chemotherapy for mCRPC that may potentiate antitumor immune responses, thus supporting its use in combination with NIVO, which has shown limited antitumor activity in mCRPC as monotherapy. We report final analysis results for Arm B (NIVO + DOCE) of CheckMate 9KD. Methods: Arm B enrolled patients with chemotherapy-naive mCRPC with ongoing androgen deprivation therapy and ≤ 2 prior novel antiandrogen therapies (NATs; i.e., abiraterone, enzalutamide, etc.). Patients received NIVO 360 mg + DOCE 75 mg/m2 Q3W + prednisone 5 mg BID for ≤ 10 cycles, followed by NIVO 480 mg Q4W until disease progression/unacceptable toxicity (up to 2 years). Coprimary endpoints were objective response rate (ORR) and prostate-specific antigen response rate (PSA-RR; defined as a ≥ 50% PSA reduction). Secondary endpoints included radiographic progression-free survival (rPFS), overall survival (OS), and safety. Results: Of 84 treated patients with a median age of 71 years (range: 53-88), 27% had visceral disease and 54% had measurable disease. The median number of docetaxel cycles was 8; the median number of nivolumab doses was 11. Median follow up was 15.2 months. The table displays the efficacy outcomes, which appear to show comparable ORR in patients receiving versus not receiving prior NAT. There was 1 (2.2%) complete objective response and 17 (37.8%) partial responses in 45 patients with measurable disease. Any-grade treatment-related AEs (TRAEs) occurred in 95.2% of patients, most commonly fatigue (39.3%), diarrhea (35.7%), and alopecia (34.5%). Grade 3-4 TRAEs occurred in 47.6% of patients, most commonly neutropenia (16.7%). TRAEs led to discontinuation in 29.8% of patients. The most common immune-related AEs were GI (35.7%) or skin-related (26.2%). There were 3 treatment-related deaths (1 pneumonitis related to NIVO; 2 pneumonias related to DOCE). Conclusions: NIVO + DOCE has encouraging clinical activity in patients with chemotherapy-naïve mCRPC, regardless of prior NAT, with a safety profile consistent with those of the individual agents. These outcomes support the ongoing phase 3 CheckMate 7DX trial of NIVO + DOCE vs placebo + DOCE for mCRPC (NCT04100018). Clinical trial information: NCT03338790. [Table: see text]

Trans-ancestry genome-wide association meta-analysis of prostate cancer identifies new susceptibility loci and informs genetic risk prediction

Prostate cancer is a highly heritable disease with large disparities in incidence rates across ancestry populations. We conducted a multiancestry meta-analysis of prostate cancer genome-wide association studies (107,247 cases and 127,006 controls) and identified 86 new genetic risk variants independently associated with prostate cancer risk, bringing the total to 269 known risk variants. The top genetic risk score (GRS) decile was associated with odds ratios that ranged from 5.06 (95% confidence interval (CI), 4.84-5.29) for men of European ancestry to 3.74 (95% CI, 3.36-4.17) for men of African ancestry. Men of African ancestry were estimated to have a mean GRS that was 2.18-times higher (95% CI, 2.14-2.22), and men of East Asian ancestry 0.73-times lower (95% CI, 0.71-0.76), than men of European ancestry. These findings support the role of germline variation contributing to population differences in prostate cancer risk, with the GRS offering an approach for personalized risk prediction.

Machine-assisted interpretation of auramine stains substantially increases through-put and sensitivity of microscopic tuberculosis diagnosis

Of all bacterial infectious diseases, infection by Mycobacterium tuberculosis poses one of the highest morbidity and mortality burdens on humans throughout the world. Due to its speed and cost-efficiency, manual microscopy of auramine-stained sputum smears remains a crucial first-line detection method. However, it puts considerable workload on laboratory staff and suffers from a limited sensitivity. Here we validate a scanning and analysis system that combines fully-automated microscopy with deep-learning based image analysis. After automated scanning, the system summarizes diagnosis-relevant image information and presents it to the microbiologist in order to assist diagnosis. We tested the benefit of the automated scanning and analysis system using 531 slides from routine workflow, of which 56 were from culture positive specimen. Assistance by the scanning and analysis system allowed for a higher sensitivity (40/56 positive slides detected) than manual microscopy (34/56 positive slides detected), while greatly reducing manual slide-analysis time from a recommended 5-15 min to around 10 s per slide on average.

Abstract 2076: Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis

Membranes are unique phospholipid (PL) interfaces that play a central role in cancer cell biology. However, PL composition of clinical tumors, and its dynamic regulation, remains a critical gap in the molecular profiling of this disease. Here, we used mass spectrometry-based spatial imaging and lipidomics to generate PL profiles of clinical prostate tissues upon cancer development and in patient-derived tumor explants (PDEs; n=43) cultured with the current clinical agent enzalutamide. Analysis of more than 100 PL species in tumors and matched normal tissues from 21 patients revealed a complexity of cancer-related changes in the tissue PL landscape. Phosphatidylcholine (PC)-based PLs were the most abundant PL class, and their relative abundance was increased in tumors compared to matched benign tissues. A greater proportion of monounsaturated fatty acid chains was characteristic of PLs in tumors, most evident in the PC and phosphatidylethanolamine (PE) PLs, as was striking elongation of fatty acid chains in the phosphatidylinositol (PI) and phosphatidylserine (PS) classes. The abundance of specific PL species and saturation groups was significantly associated with malignancy in both this and an independent cohort of unmatched patient tissues (n=47). Notably, the PL profile was significantly associated with the ERG molecular subtype and basal proliferative index (Ki67) in tumors. Furthermore, we identified individual PL species that were associated with the antiproliferative response to enzalutamide, in cultured PDEs. In light of these PL features, we proposed acetyl coA carboxylase (ACC) as a novel therapeutic target in prostate cancer. Indeed, blocking lipid biosynthesis and elongation in prostate tumors with an ACC inhibitor (ACCi, PF-05175157) significantly reduced tumor cell proliferation in PDE tissues (n=13), concomitant with increased pACC1 staining and a decreased proportion of longer chain PLs. Our findings suggest that the clinical PCa lipidome is not only a marker of malignant transformation and aggressiveness, but also therapeutic response to enzalutamide. Moreover, defining this unique biology identified further clinically actionable targets that may improve prostate cancer outcomes.

Citation Format: Lisa M. Butler, Chui Yan Mah, Jonas Dehairs, Andrew Vincent, Shadrack Mutuku, Xander Spotbeen, Rajdeep Das, Zeyad Nassar, Luke Selth, Paul Trim, Marten Snel, David Lynn, Lisa Horvath, Wayne Tilley, Margaret Centenera, Johannes Swinnen. Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2076.

Phase I study of AMG 509, a STEAP1 x CD3 T cell-recruiting XmAb 2+1 immune therapy, in patients with metastatic castration-resistant prostate cancer (mCRPC)

TPS5589

Background: Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a cell surface antigen that is highly expressed in prostate cancer. AMG 509 is a potent bispecific XmAb 2+1 immune therapy designed to direct T-effector cells to STEAP1-expressing cells. AMG 509 contains two identical humanized anti-STEAP1 Fab domains that bind STEAP1-expressing cells, an anti-CD3 scFv domain that binds T cells, and an Fc domain, engineered to lack effector function, that extends serum half-life. In preclinical studies, AMG 509 induced potent and specific T-cell-mediated lysis of STEAP1-expressing cancer models. Methods: This open-label, phase I, first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK), and efficacy of AMG 509 in patients with relapsed/refractory mCRPC. The dose exploration phase (n=40) will estimate the maximum tolerated dose (MTD) or recommended phase II dose (RP2D) using a Bayesian logistic regression model. The dose expansion phase (n=30) will confirm safety, PK, and pharmacodynamics at the MTD or RP2D and collect further safety, efficacy, and biomarker data. Efficacy will be assessed by prostate-specific antigen response, circulating tumor cell response, and objective tumor response per RECIST 1.1 with Prostate Cancer Working Group 3 modifications. Key inclusion criteria: men ≥18 years with histologically/cytologically confirmed mCRPC who are refractory to novel hormonal therapy (e.g., abiraterone and/or enzalutamide) and have failed 1–2 taxane regimens or are medically unsuitable for or have refused taxanes; ongoing castration with total serum testosterone ≤50 ng/dL; evidence of progressive disease; ECOG performance status 0–1; life expectancy ≥3 months; and adequate hematologic, renal, hepatic, and cardiac function. In the dose exploration phase, novel antiandrogen therapy must have been given in the metastatic setting. Key exclusion criteria: pure small-cell or neuroendocrine carcinoma of the prostate; untreated CNS metastases or leptomeningeal disease; any anticancer therapy or immunotherapy, radiation therapy, or major surgery <4 weeks from first dose; history of or current autoimmune disease or any disease requiring immunosuppressive therapy (≤10 mg/d prednisone permitted); prior STEAP1-targeted therapy; infection requiring IV antimicrobials <7 days from first dose. The study opened in January 2020 and is recruiting patients. Clinical trial information: NCT04221542 .

A phase I study of APL-501, an anti-PD-1 antibody, in patients with recurrent or advanced solid tumors

e15125

Background: APL-501 is a humanized monoclonal antibody targeting programmed cell death-1 (PD-1). APL-501 is being evaluated in patients (pts) with advanced recurrent and relapsed solid tumors who had not been previously treated with an immune checkpoint inhibitor in an ongoing 3-part Phase 1 trial (NCT03053466). Herein, we present the emerging pharmacokinetic (PK) and receptor occupancy (RO), safety and preliminary efficacy. Methods: Weight-based dose escalation (1, 3, and 10 mg/kg, Part 1) and Extension (Part 2) has been completed and the study is currently enrolling specific tumor types (MSI-H/dMMR and Carcinoma of Unknown Primary [CUP]) into the Expansion Cohorts (Part 3). Relapsed/refractory solid tumor pts were enrolled in Part 1 and Part 2. Key exclusion criteria included prior therapy targeting PD-1/PD-L1 and uncontrolled CNS metastases. APL-501 was administered IV over 1 hour every 14 days. Serum and PBMCs were collected for PK and RO analysis, respectively. RO was assessed using different T-cell markers measured by flow cytometry of PBMC. Anti-tumor activity was assessed by investigators using RECIST and irRECIST. Safety was assessed using CTCAE, v4.03. Results: As of 31 Dec 2019, 22 pts were enrolled with a mean age of 62.1 (SD: 12.2) years. ECOG PS 0/1 reported at 10/12 pts, respectively. Pts had a median number of 3 prior lines of therapy (range, 1 – 9) and median time to treatment from initial diagnosis was 30.1 months (range, 6.7 – 184.8). Across doses evaluated, APL-501 demonstrated dose proportional PK. One hundred percent (100%) RO was observed across all doses evaluated. No dose limiting toxicities were reported. Fifteen pts (68.2%) had related AEs; two pts (9.1%) had Grade ≥ 3 related AEs to APL-501. Eight pts had stable disease and two pts had partial response by RECIST (esophageal adenocarcinoma and CUP). Seven pts remained on therapy for ≥ 24 weeks. The recommended phase 2 dose (RP2D) has been determined to be 400 mg IV every 14 days (non-weight-based) based on safety and PK modeling. Conclusions: Preliminary results indicate clinical activity of APL-501 in relapsed/refractory malignant disease with a generally tolerable safety profile. The PK and RO profile, across all doses evaluated, appears comparable to marketed PD-1 inhibitors. Continued exploration of APL-501 with the RP2D in CUP and MSI-H/dMMR tumors is being planned. Clinical trial information: NCT03053466 .

Evaluation of a mainstream model of genetic testing for men with prostate cancer

1521

Background: In order to identify the ∼12% with inherited cancer predisposition, it is recommended that all men with metastatic prostate cancer (mPC) be offered testing. This has implications for treatment choices and cancer prevention in family. Limited geneticists/genetic counsellors globally present a major barrier to testing. We tested a potential solution, mainstreaming, where testing is performed by the patient’s oncologist. Methods: Men with mPC at three Australian sites were offered germline genetic testing at their medical oncology appointment. Panel testing ( ATM, BRCA1, BRCA2, BRIP1, CHEK2, EPCAM, FANCA, HOXB13, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, RAD51D and TP53) was performed on saliva/blood (Invitae). Primary outcomes were clinician and patient acceptability (modified Royal Marsden Satisfaction Questionnaires). Secondary outcomes included mutation rates and cost-effectiveness. A sample size of 44 provided 90% power, with a one-sided alpha of 5%, to distinguish a proportion of men happy with mainstreaming of 80% vs. 60% or less. Allowing for 25% drop-out, we aimed to recruit 60 men. Results: Of 66 men offered testing from April to November 2019, 63 (95%) accepted. Four pathogenic variants were identified (2 BRCA2, 1 NBN, 1 MSH6). 48 patients and eight clinicians completed questionnaires. Acceptability was high. All (48/48) patients were happy to have been tested, and 45/48 (94%) were happy to have been tested at their oncology appointment. All were happy to receive their results from their oncologist. All clinicians were satisfied mainstreaming and 88% (7/8) felt confident doing so. Mainstreaming was cost-effective, requiring 87% fewer genetic consultations than traditional genetic counselling. Conclusions: This study shows that mainstreaming of men with mPC is feasible, resource efficient and acceptable to both clinicians and patients. Widespread implementation as a new standard of care would facilitate timely access to genetic testing for men with mPC.

Phase I study of AMG 160, a half-life extended bispecific T-cell engager (HLE BiTE immune therapy) targeting prostate-specific membrane antigen, in patients with metastatic castration-resistant prostate cancer (mCRPC)

TPS5590

Background: Prostate-specific membrane antigen (PSMA) is a clinically validated therapeutic target for the imaging and treatment of mCRPC. AMG 160 is an HLE BiTE immune therapy designed to redirect T cells to cancer cells by binding to PSMA on cancer cells and CD3 on T cells. BiTE immune therapy leads to direct tumor cell killing, T-cell activation and expansion, and the creation of a pro-inflammatory tumor microenvironment. Combining AMG 160 with a PD-1 inhibitor may enhance antitumor activity by enabling sustained T-cell-dependent killing of tumor cells in the inflamed tumor microenvironment. Methods: NCT03792841 is a phase I study of AMG 160 as monotherapy (part 1) and in combination with pembrolizumab (part 2) in men with histologically/cytologically confirmed mCRPC who are refractory to a novel hormonal therapy (abiraterone, enzalutamide, and/or apalutamide) and have failed 1–2 taxane regimens (or are medically unsuitable or have refused taxanes), who have ongoing castration with total serum testosterone ≤ 50 ng/dL, and have evidence of progressive disease. Patients who received prior PSMA radionuclide therapy may be eligible. Patients with CNS metastases, leptomeningeal disease, spinal cord compression, or active autoimmune disease will be excluded. Primary objectives are to evaluate safety and tolerability and determine the maximum tolerated dose (MTD) or recommended phase II dose (RP2D) of AMG 160 given as monotherapy or in combination with pembrolizumab. Secondary objectives are to characterize pharmacokinetics and preliminary antitumor activity. Exploratory objectives include evaluation of potential pharmacodynamic and patient selection biomarkers, immunogenicity, and patient-reported pain and functional outcomes. The part 1 dose exploration will determine the MTD/RP2D of AMG 160. The part 1 dose expansion will confirm the safety and tolerability of the MTD/RP2D. The part 2 dose exploration will estimate the MTD/RP2D of AMG 160 in combination with pembrolizumab. Evaluation of preliminary antitumor activity will be based on RECIST 1.1 with Prostate Cancer Working Group 3 modifications, PSA response, CTC response, progression-free survival (radiographic and PSA), and overall survival. PSMA PET/CT and FDG PET/CT imaging will be used for evaluation of exploratory objectives. The study opened in February 2019 and is currently recruiting patients into both part 1 and part 2. Clinical trial information: NCT03792841 .

Phase I, Open-Label, Dose-Escalation/Dose-Expansion Study of Lifirafenib (BGB-283), an RAF Family Kinase Inhibitor, in Patients With Solid Tumors

PURPOSE

Lifirafenib is an investigational, reversible inhibitor of B-RAF^V600E, wild-type A-RAF, B-RAF, C-RAF, and EGFR. This first-in-human, phase I, dose-escalation/dose-expansion study evaluated the safety, tolerability, and efficacy of lifirafenib in patients with B-RAF– or K-RAS/N-RAS–mutated solid tumors.

METHODS

During dose escalation, adult patients with histologically/cytologically confirmed advanced solid tumors received escalating doses of lifirafenib. Primary end points were safety/tolerability during dose escalation and objective response rate in preselected patients with B-RAF and K-RAS/N-RAS mutations during dose expansion.

RESULTS

The maximum tolerated dose was established as 40 mg/d; dose-limiting toxicities included reversible thrombocytopenia and nonhematologic toxicity. Across the entire study, the most common grade ≥ 3 treatment-emergent adverse events were hypertension (n = 23; 17.6%) and fatigue (n = 13; 9.9%). One patient with B-RAF–mutated melanoma achieved complete response, and 8 patients with B-RAF mutations had confirmed objective responses: B-RAF^V600E/K melanoma (n = 5, including 1 patient treated with prior B-RAF/MEK inhibitor therapy), B-RAF^V600E thyroid cancer/papillary thyroid cancer (PTC; n = 2), and B-RAF^V600E low-grade serous ovarian cancer (LGSOC; n = 1). One patient with B-RAF–mutated non–small-cell lung cancer (NSCLC) had unconfirmed partial response (PR). Patients with K-RAS–mutated endometrial cancer and K-RAS codon 12–mutated NSCLC had confirmed PR (n = 1 each). No responses were seen in patients with K-RAS/N-RAS–mutated colorectal cancer (n = 20).

CONCLUSION

Lifirafenib is a novel inhibitor of key RAF family kinases and EGFR, with an acceptable risk-benefit profile and antitumor activity in patients with B-RAF^V600–mutated solid tumors, including melanoma, PTC, and LGSOC, as well as K-RAS–mutated NSCLC and endometrial carcinoma. Future comparisons with first-generation B-RAF inhibitors and exploration of lifirafenib alone or as combination therapy in patients with selected RAS mutations who are resistant/refractory to first-generation B-RAF inhibitors are warranted.

Plasma cell-free DNA (cfDNA) profiling of copy number variation (CNV) to identify poor prognostic biomarkers in metastatic castration-resistant prostate cancer (mCRPC)

176

Background: Multiple tumour tissue studies have demonstrated the prognostic utility of CNVs in mCRPC. However, accurate assessment of CNVs in plasma cfDNA remains challenging, and prognostic significance has not been well characterized. Using a large customized panel, we correlated plasma CNVs with clinical outcomes in a contemporary cohort of mCRPC patients. Methods: Deep targeted sequencing was performed using a 180-gene cfDNA panel (Predicine) in 56 patients commencing AR pathway inhibitors (enzalutamide or abiraterone; n = 34) or taxane chemotherapy (n = 22) at two Australian institutions. Kaplan-Meier estimates and Cox proportional-hazards models were used to correlate CNVs with progression-free survival (PFS) and overall survival (OS). Significant results were validated in an independent cohort (Mayo Clinic, n = 144). Results: Median follow-up was 19.4 months (mo; IQR 11.3-31.9). The most common CNVs in the Australian cohort are shown (Table). OS was significantly decreased in patients with PI3KCA gain (median 21.7 mo vs 6.6 mo, p < 0.0001), PTEN loss (24.8 mo vs 11.7 mo, p = 0.0019) and AR gain (21.7 mo vs 12.0 mo, p = 0.0083). Furthermore, all three alterations independently predicted for poor survival in multivariable analyses (MVA; Table). Findings in the independent cohort showed similar OS results in MVA: PIK3CA gain (HR 2.0, p = 0.07), PTEN loss (HR 1.7, p = 0.08) and AR gain (HR 1.7, p = 0.03). Conclusions: Sequencing of plasma cfDNA revealed that PTEN loss, and PIK3CA and AR gain are associated with inferior clinical outcomes in patients commencing contemporary systemic treatment. These data support therapeutic strategies co-targeting the PI3K and AR pathways in mCRPC.[Table: see text]

Phase I study of AMG 160, a half-life extended bispecific T-cell engager (HLE BiTE) immune therapy targeting prostate-specific membrane antigen (PSMA), in patients with metastatic castration-resistant prostate cancer (mCRPC)

TPS261

Background: AMG 160 is a novel HLE BiTE immune therapy that redirects T cells to kill tumor cells by binding to PSMA on tumor cells and CD3 on T cells. Methods: Primary objectives of this open-label, ascending, multiple-dose, phase 1 study (NCT03792841) are to evaluate safety and tolerability and determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of AMG 160 in men with mCRPC; secondary objectives are to characterize pharmacokinetics (PK) and evaluate preliminary efficacy. The dose exploration will estimate the MTD or RP2D by Bayesian logistic regression modeling. The dose expansion will assess safety, efficacy, PK, and pharmacodynamics (PD) of the selected dose and provide further safety and efficacy data. PD biomarkers and potential patient selection biomarkers will be explored. Preliminary antitumor activity will be assessed by objective response per RECIST 1.1 with PCWG3 modifications, PSA response, duration of response, time to progression, PFS (radiographic and PSA)/OS, and circulating tumor cell (CTC) response (CTC0 and CTC conversion). Imaging will include CT/MRI, bone scan, 68Ga-PSMA-11 PET/CT, and 18F-FDG PET/CT. In cycle 1, patients will be pretreated with dexamethasone before short-term IV infusion of AMG 160 and will be hospitalized for 72 h after each AMG 160 dose. Key inclusion criteria: age ≥18 y; histologically/cytologically confirmed mCRPC that progressed after novel hormone therapy; failure of 1–2 taxane-based regimens or have refused a taxane regimen; bilateral orchiectomy or continuous androgen-deprivation therapy; evidence of progressive disease; total serum testosterone ≤50 ng/dL. Key exclusion criteria: active autoimmune disease or diseases requiring immunosuppressive therapy (low-dose prednisone permitted); CNS metastases, leptomeningeal disease, or spinal cord compression; prior PSMA-targeted therapy (177Lu-PSMA-617 may be allowed). The study will enroll 30–50 patients in the dose exploration and 50 patients in the dose expansion globally. The study opened in January 2019; dose exploration is ongoing. Clinical trial information: NCT03792841.

DASL-HiCAP (ANZUP1801): The impact of darolutamide on standard therapy for localized very high-risk cancer of the prostate—A randomized phase III double-blind, placebo-controlled trial of adding darolutamide to androgen deprivation therapy and definitive or salvage radiation in very high-risk, clinically localized prostate cancer

TPS385

Background: Radiation therapy (RT), plus androgen deprivation therapy (ADT) with a luteinising hormone releasing hormone analogue (LHRHA) for at least one year, is standard of care for men with very high-risk localised prostate cancer (PC), or with very high-risk features and persistent PSA after radical prostatectomy (RP). Despite this, incurable distant metastases develop within 5 years in 15% of men with very high risk features. Darolutamide is an androgen receptor antagonist with favourable tolerability. Our aim is to determine the efficacy of adding darolutamide to ADT and RT given in the setting of either primary definitive therapy (RP or RT), or adjuvant therapy for very high-risk PC. Methods: This study is a randomised (1:1) phase III placebo-controlled, double-blind trial for men planned for RT who have very high-risk localised PC, or very high-risk features with PSA persistence or rise within one year following RP. The trial will be stratified by: use of adjuvant docetaxel; pelvic nodal involvement; RP. 1100 participants will be randomised to darolutamide 600 mg or placebo twice daily for 96 weeks. Participants will receive LHRHA for 96 weeks, plus RT starting week 8-24 from randomisation. Participants are allowed nonsteroidal antiandrogen (up to 90 days) in addition to LHRHA up until randomisation. Early treatment with 6 cycles of docetaxel completed at least 4 weeks prior to RT is permitted. The primary endpoint is metastasis-free survival, with secondary endpoints overall survival, PC-specific survival, PSA-progression free survival, time to subsequent hormonal therapy, time to castration-resistance, frequency and severity of adverse events, health related quality of life, fear of recurrence. Tertiary endpoints include incremental cost-effectiveness, and identification of prognostic and/or predictive biomarkers of treatment response, safety and resistance to study treatment. Clinical trial information: NCT04136353.

Abstract CT084: Long-term exposure (LTE) to Tislelizumab, an investigational anti-PD-1 antibody, in a first-in-human Phase I study

Background Tislelizumab (BGB-A317), an investigational monoclonal antibody with high affinity and specificity for PD-1, was engineered to minimize binding to FcγR on macrophages in order to abrogate antibody-dependent phagocytosis, a potential mechanism of resistance to anti-PD-1 therapy. Previous reports from early phase studies suggest tislelizumab was generally well tolerated and had antitumor activity in patients (pts) with advanced solid tumors. Clinical effects of tislelizumab LTE (&gt;12 mo) in pts enrolled in the first-in-human study (NCT02407990) are presented here.

Methods Patients with advanced solid tumors received IV tislelizumab 0.5, 2, 5, or 10 mg/kg Q2W, 2 or 5 mg/kg administered Q2W or Q3W, or 200 mg IV Q3W. Antitumor activity was assessed by RECIST v1.1 criteria; PD-L1 expression was retrospectively assessed with the VENTANA PD-L1 (SP263) assay.

Results As of 31 Aug 2018, 63 of the 451 pts received tislelizumab for &gt;12 mo. In these 63 pts, median age was 64 yr and 70% had received ≥1 prior systemic therapy. Tislelizumab LTE was most common in NSCLC (n=9), HCC (n=7), and bladder and ovarian (n=5 each) cancers. Four of the 5 pts who achieved CR during this study had LTE to tislelizumab (Table); all 4 pts were PD-L1+ (≥1% expression on tumor cells). Across the LTE cohort, ORR was 66.7%; PR and SD were observed in both PD-L1+ and PD-L1- tumors. The median time to CR/PR (3.7 mo) and duration of CR/PR (21.1 mo) were longer in pts with LTE than pts who responded but did not remain on treatment for &gt;12 mo (2.1 and 6.3 mo, respectively). Rash was the only treatment-related AE (TRAE) reported in ≥15% of pts. Most TRAEs were of mild or moderate severity; arthritis, diarrhea, fatigue, granuloma, hyperglycemia, and lichenoid keratosis (n=1 each) were the only grade ≥3 TRAEs reported with tislelizumab LTE.

Conclusion Tislelizumab remained well tolerated for &gt;12 mo and elicited durable responses in pts with a variety of tumor types regardless of PD-L1 status.

PD-L1+ (n=35)PD-L1- (n=22)Missing (n=6)Total (N=63)CR4004 (6.3%)PR2113438 (60.3%)SD99220 (31.7%)PD1001 (1.6%)Abbreviations: CR, complete response; PD, progressive disease; PR, partial response; SD stable disease.

Citation Format: Jayesh Desai, Benjamin Markman, Michael Friedlander, Hui Gan, Lisa Horvath, Amanda Townsend, Michael Millward, Michael Jameson, Chia-Jui Yen, Ming-Mo Hou, Jeannie Hou, John Wu, Liang Liang, Sanjeev Deva. Long-term exposure (LTE) to Tislelizumab, an investigational anti-PD-1 antibody, in a first-in-human Phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT084.

Overall survival (OS) results of a phase III randomized trial of standard-of-care therapy with or without enzalutamide for metastatic hormone-sensitive prostate cancer (mHSPC): ENZAMET (ANZUP 1304), an ANZUP-led international cooperative group trial

LBA2

Background: Testosterone suppression (TS) is the backbone of treatment for mHSPC. OS is improved by the addition of early docetaxel (DOC) or abiraterone to TS. ENZAMET assessed the effects of enzalutamide (ENZA), a potent androgen receptor (AR) inhibitor, versus a nonsteroidal anti-androgen (NSAA: bicalutamide, nilutamide, or flutamide) in addition to SOC (TS with or without DOC) in mHSPC. Methods: Men with mHSPC were randomly assigned 1:1 to receive TS plus either ENZA or NSAA. Randomization was stratified by: volume of disease (high vs low, according to CHAARTED); planned early DOC; planned anti-resorptive therapy, comorbidity score (ACE-27), and study site. The primary endpoint was overall survival. Accrual of 1100 men provided 80% power to detect a 25% reduction in the hazard of death (HR 0.75) with up to 4 interim analyses (IA), the first planned to occur after 235 deaths (50% of total information with a critical p-value threshold <0.0031 by the Lan-DeMets alpha-spending approach with O’Brien-Fleming type shape). Subgroup analyses to assess possible modulation of the treatment effect were specified a priori and included planned early docetaxel (yes vs no) and volume of disease (high vs low). Results: We randomly assigned 1125 patients from 31MAR14 to 24MAR17. The treatment groups were well balanced for all important baseline factors. Criteria for early reporting were met at the first IA (28FEB2019) after a median follow-up of 33 months. Overall survival was prolonged by ENZA (see below). At 3 years, 36% NSAA vs 64% ENZA were still on their assigned study treatment. Serious adverse events (regardless of attribution) within 30 days of study treatment occurred in 42% ENZA vs 34% NSAA, commensurate with the different durations of study treatment. Conclusions: ENZA significantly improved OS when added to SOC in mHSPC. The benefits appeared lower in those planned to receive early DOC. Results of analyses with updated follow-up triggered by this IA will be presented. Clinical trial information: NCT02446405. [Table: see text]

AB928, a novel dual adenosine receptor antagonist, combined with chemotherapy or AB122 (anti-PD-1) in patients (pts) with advanced tumors: Preliminary results from ongoing phase I studies

2604

Background: AB928, a selective, small-molecule A2aR/A2bR antagonist, potently blocks the immunosuppressive effects of high adenosine concentrations in the tumor microenvironment. Preclinically, combining adenosine receptor inhibition with either chemotherapy or anti-PD-1 resulted in greater tumor control, suggesting AB928 may have additive activity when paired with either of these agents in cancer pts. Methods: Three dose-escalation (3+3 design) studies are assessing the safety, pharmacokinetics (PK), pharmacodynamics, and clinical activity of increasing doses of AB928 (75, 150, 200 mg orally once daily) in combination with: standard pegylated liposomal doxorubicin in triple-negative breast cancer (TNBC) and ovarian cancer (OC); standard mFOLFOX6 in gastroesophageal cancer (GEC) and colorectal cancer (CRC); and AB122 (240 mg every 2 weeks) in various advanced tumors. Following identification of the recommended phase 2 dose of AB928 in combination with chemotherapy or AB122 in dose escalation, the following tumor cohorts may be expanded (15-40 pts/cohort) to further test the combinations: TNBC and OC, GEC and CRC, and renal cell carcinoma. Results: As of 01Feb2019, 9 pts were treated across the 3 studies, and time on treatment ranged from 1-182 days (table). Overall, AB928 combination therapy was well tolerated. Two pts underwent post-baseline disease assessment; both had stable disease. Preliminary data indicate that AB928 PK and adenosine receptor coverage in cancer pts are similar to what was previously assessed in healthy volunteers. AB122 PK and PD-1 coverage are equally unaffected by AB928 co-administration. Updated data, including biomarker data, will be presented at the meeting. Conclusions: Early results showed a favorable safety profile of AB928 combination therapy. All 3 studies are actively recruiting pts. Clinical trial information: NCT03719326; NCT03720678; NCT03629756. [Table: see text]

Expression of Androgen Receptor Splice Variant 7 or 9 in Whole Blood Does Not Predict Response to Androgen-Axis-targeting Agents in Metastatic Castration-resistant Prostate Cancer

In 2014, a landmark study was published demonstrating that the expression of androgen receptor splice variant (AR-V) 7 was a negative predictive biomarker for response to abiraterone acetate and enzalutamide in metastatic castration-resistant prostate cancer (mCRPC) patients. However, these results were not supported by the recently reported ARMOR3-SV phase III clinical trial, which employed an identical circulating tumour cell assay to assess AR-V7 expression. Therefore, the predictive utility of AR-V7 expression in mCRPC remains uncertain, as does any potential association between other AR-Vs and treatment response. To further investigate, we designed a highly sensitive and specific whole blood assay for detecting AR-V7 and AR-V9. We then examined for a correlation between baseline AR-V7/V9 status and treatment outcome in 37 mCRPC patients commencing abiraterone or enzalutamide. Of the patients, 24% (9/37) were AR-V-positive. Notably, prostate-specific antigen (PSA) response rates did not significantly differ between AR-V-positive (6/9) and AR-V-negative (18/28) patients (66% vs 64%, p=0.9). Likewise, median PSA progression-free survival was not significantly different between AR-V-positive and AR-V-negative patients (9.2 mo vs not reached; p=0.9). These data, which support the findings of the pivotal ARMOR3-SV clinical trial, suggest that baseline AR-V expression does not predict outcomes in mCRPC patients receiving abiraterone or enzalutamide.

PATIENT SUMMARY

Detection of androgen receptor splice variants (AR-Vs) in circulating tumour cells of advanced prostate cancer patients has been linked to resistance to abiraterone and enzalutamide. We designed a blood test to detect AR-Vs that can be performed more routinely than tests involving circulating tumour cells and found that patients with AR-Vs still benefit from these effective treatments.

FPT155-001: A phase Ia/Ib study of FPT155 (CD80-FC) in patients with advanced solid tumors

TPS42

Background: Despite recent advances in immunotherapy, many patients with advanced solid tumors are refractory to available therapies or eventually relapse. Novel immune therapies are needed with differentiated mechanisms of action that result in improved response rates and durability across a broad range of tumors. FPT155 is a first-in-class therapeutic being developed to meet this need. FPT155 is a recombinant fusion protein composed of the extracellular domain of human CD80 fused with the Fc domain of human immunoglobulin G1. It is designed to act as a potent stimulator of anti-tumor immunity through CD28 and thereby co-stimulate T cell responses only in the presence of antigenic T cell receptor (TCR) signaling. FPT155 alone does not induce spontaneous cytokine release by primary human immune cells, in contrast to a CD28 superagonist antibody that exerts TCR stimulus-independent activity. FPT155 also blocks CTLA-4 from competing for endogenous CD80, allowing CD28 signaling to prevail in T cell activation. A murine surrogate of FPT155 is a potent inhibitor of tumor growth that induces complete tumor regression in multiple tumor models, including models that are insensitive to anti-PD1 or anti-CTLA4. Methods: The FPT155-001 study is a Phase 1a/1b open-label, multicenter, dose escalation and expansion study to evaluate the safety and tolerability of FPT155 monotherapy. Phase 1a dose escalation includes an accelerated titration design followed by a standard 3+3 design until the recommended dose for Phase 1b is determined by evaluation of all available safety, pharmacokinetic (PK), and pharmacodynamic (PD) data. Eligible patients with advanced solid tumors who are refractory to all standard therapy for their malignancy will be enrolled in Phase 1a. Phase 1b dose expansion will enroll patients with select tumor types. The primary endpoint is safety in both phases. Key secondary endpoints in Phase 1a include characterization of the FPT155 PK profile and immunogenicity. Key secondary endpoints in Phase 1b include objective response rate, duration of response, progression free survival, and disease control rate. The FPT155-001 trial opened for enrollment in October 2018 and is in progress. Clinical trial information: Submitted - awaiting registration number.

Whole blood FOLH1 mRNA expression and treatment response in metastatic castration-resistant prostate cancer (mCRPC)

188

Background: Identifying predictive biomarkers for mCRPC patients receiving androgen receptor signalling inhibitors (ARSI) or chemotherapy remains an unmet clinical need. FOLH1 encodes for Prostate-Specific Membrane Antigen (PSMA), a type II glycoprotein highly expressed on prostate cancer cells. We designed a whole blood assay to detect FOLH1 mRNA, and correlated expression with clinical outcomes in patients commencing ARSI (abiraterone or enzalutamide) or chemotherapy (docetaxel or cabazitaxel). Methods: mCRPC patients commencing ARSI or chemotherapy were prospectively recruited at three Australian centres from June 2016 to July 2018. A quantitative reverse transcription polymerase chain reaction assay was used to detect FOLH1 transcript from whole blood samples collected in PAXgene® RNA tubes. Pre-treatment FOLH1 expression was correlated with PSA response rate (Fisher’s exact test) and PSA progression-free survival (PSA-PFS) (log-rank test). Results: Median follow-up was 13.6 months (IQR 9.7–19.3). In total, 88 pre-treatment samples were analysed, of which 75 (85%) were FOLH1-positive. In patients receiving ARSI, outcomes favoured FOLH1-positive patients compared to FOLH1-negative patients, with higher PSA response rates (39/60, 65% vs. 2/7, 29%; p = 0.1) and longer PSA-PFS (median 9.0 months [95% CI, 7.2-10.8] vs. 2.8 months [95% CI, 2.3-3.3]; p = 0.03). Conversely, in chemotherapy-treated patients, inferior outcomes were observed in FOLH1-positive patients compared to FOLH1-negative patients, with lower PSA response rates (4/15, 27% vs. 5/6, 83%, p = 0.05) and shorter PSA-PFS (median 2.9 months [95% CI, 2.8-3.0] vs. 4.1 months [95% CI, 3.7-4.5]; p = 0.32). Conclusions: Pre-treatment FOLH1 expression may differentiate between outcomes on ARSI vs. chemotherapy in mCRPC patients. The utility of FOLH1 as a predictive biomarker in mCRPC warrants further evaluation in larger, independent cohorts. [Table: see text]

Modulation of plasma lipidomic signature in metastatic castration-resistant prostate cancer (mCRPC)

TPS331

Background: Altered lipid metabolism and its impact on prostate cancer (PC) is increasingly recognised, in light of the association between obesity and worse PC outcomes. Our exploratory study was the first to identify baseline plasma lipidomic profiles in men with mCRPC commencing docetaxel that were associated with survival. A prognostic three-lipid signature was derived, consisting of ceramide, sphingomyelin and phosphatidylcholine (HR 4.8, 95% CI 2.06-11.1, p = 0.0003). This signature was independently prognostic when modelled with clinicopathological factors and metabolic characteristics. A key question is whether therapeutic modulation of a patient’s lipid profile is possible. Statins significantly reduce the plasma levels of ceramides, sphingomyelin and cholesterol in cardiovascular disease, suggesting that this therapy could change the poor prognostic lipid profile of mCRPC patients. This trial assesses whether addition of simvastatin to docetaxel for mCRPC can reverse the poor prognostic lipid signature with the aim of developing a precision medicine strategy for metabolic targeting. Methods: This investigator-initiated, multi-centre, open-label, single arm, pilot study enrols patients with mCRPC commencing docetaxel for disease progression, not already receiving a lipid-lowering agent. Patients are treated with simvastatin 40mg orally once daily for 12 weeks, commencing on day 1 of the first cycle of docetaxel. Blood is taken at baseline and after 12 weeks of simvastatin and the plasma lipidomic profile is determined using liquid chromatography and electrospray ionisation-tandem mass spectrometry. The lipidomic profile is classified as either good or poor prognostic as per our three-lipid signature model derived by logistic regression. The primary objective is to assess the rates of conversion from a poor prognostic lipid signature to good prognostic after simvastatin. A sample size of 60 men provides over 90% power, with a 1-sided type 1 error of 10%, to detect conversion to the good prognostic signature in 50% of patients, assuming 25% of patients have the poor prognostic signature at baseline as previously detected. To date, 6 patients have been enrolled to the trial. Clinical trial information: ACTRN12617000965303.