Treatment Of Metastatic Prostate Cancer Research Articles

Evolution of hormonal therapy for prostate cancer.

Prostate cancer (PCa) is the most common malignancy after skin cancer in men in Australia. Its management varies according to tumour stage. Due to the significant dependence on androgen receptor signalling, agents that interfere with this pathway (most commonly medical castration in the form of androgen deprivation therapy [ADT]) are the mainstay treatment of advanced disease. This review provides a contemporary update on ADT, withfurther discussion of emerging novel therapies for primary care. ADT is currently indicated for the treatment of metastatic prostate cancer, disease recurrence following attempted local curative therapy, as well as combined use with radiotherapy for intermediate/high-risk disease. There has been rapid development of new pharmaceuticals targeting the androgen receptor. These are reviewed historically with an emphasis placed on emerging therapies, their common side effects, and how to managethem in the general practice setting.

Homologous Recombination Repair Deficiency in Metastatic Prostate Cancer: New Therapeutic Opportunities

More than 20% of metastatic prostate cancer carries genomic defects involving DNA damage repair pathways, mainly in homologous recombination repair-related genes. The recent approval of olaparib has paved the way to precision medicine for the treatment of metastatic prostate cancer with PARP inhibitors in this subset of patients, especially in the case of BRCA1 or BRCA2 pathogenic/likely pathogenic variants. In face of this new therapeutic opportunity, many issues remain unsolved. This narrative review aims to describe the relationship between homologous recombination repair deficiency and prostate cancer, the techniques used to determine homologous recombination repair status in prostate cancer, the crosstalk between homologous recombination repair and the androgen receptor pathway, the current evidence on PARP inhibitors activity in metastatic prostate cancer also in homologous recombination repair-proficient tumors, as well as emerging mechanisms of resistance to PARP inhibitors. The possibility of combination therapies including a PARP inhibitor is an attractive option, and more robust data are awaited from ongoing phase II and phase III trials outlined in this manuscript.

Current state of theranostics in metastatic castrate-resistant prostate cancer.

Prostate cancer remains one of the leading causes of cancer-related death in the world. There have been significant advances in chemotherapy, hormonal therapy and targeted therapy options for patients with castrate-resistant disease. However, these systemic treatments are often associated with unwanted toxicities. Targeted therapy with radiopharmaceuticals has become of key interest to limit systemic toxicity and provides a more precision oncology approach to treatment. Strontium-89, Samarium-153 EDTMP and Radium-223 have been trialled with mixed results. Strontium-89 and Samarium-153 EDTMP have shown benefits in palliating metastatic bone pain but with no impact on survival outcomes. Early therapeutic radiopharmaceuticals targeting PSMA that were developed were beta-emitting agents, but recently alpha-emitting agents are being investigated as potentially superior options. Radium-223 is the first alpha-particle emitter therapeutic agent approved by the FDA, with phase III trial evidence showing benefits in overall survival and delay in symptomatic skeletal events for patients. Recently, 177-Lutetium-PSMA-617 has demonstrated significant survival advantages in pre-treated metastatic castrate-resistant cancer patients in a number of phase II and III studies. Furthermore, 225-Actinium-PSMA-617 also showed promise even in patients pre-treated with 177-Lutetium-PSMA-617. Hence, there has been an explosion of radiopharmaceutical treatment options for patients with prostate cancer. This review explores past and current theranostic capacities in the radiopharmaceutical treatment of metastatic castrate-resistant prostate cancer.

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

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

Preclinical efficacy of a PSMA-targeted actinium-225 conjugate (225Ac-macropa-pelgifatamab) - a targeted alpha therapy for prostate cancer.

Initially, prostate cancer responds to hormone therapy but eventually resistance develops. Beta emitter-based PSMA (prostate-specific membrane antigen)-targeted radionuclide therapy is approved for the treatment of metastatic castration-resistant prostate cancer. Here we introduce a targeted alpha therapy (TAT) consisting of the PSMA antibody pelgifatamab covalently linked to a macropa chelator and labeled with actinium-225 and compare its efficacy and tolerability with other TATs. The in vitro characteristics and in vivo biodistribution, antitumor efficacy, and tolerability of 225Ac-macropa-pelgifatamab (225Ac-pelgi) and other TATs were investigated in cell line- and patient-derived prostate cancer xenograft models. The antitumor efficacy of 225Ac-pelgi was also investigated in combination with the androgen receptor inhibitor darolutamide. Actinium-225-labeling of 225Ac-pelgi was efficient already at room temperature. Potent in vitro cytotoxicity was seen in PSMA-expressing (LNCaP, MDA-PCa-2b, and C4-2) but not in PSMA-negative (PC-3 and DU-145) cell lines. High tumor accumulation was seen for both 225Ac-pelgi and 225Ac-DOTA-pelgi in the MDA-PCa-2b xenograft model. In the C4-2 xenograft model, 225Ac-pelgi showed enhanced antitumor efficacy with a T/Cvolume (treatment/control) ratio of 0.10 compared with 225Ac-DOTA-pelgi, 225Ac-DOTA-J591, and 227Th-HOPO-pelgifatamab (227Th-pelgi) (all at 300 kBq/kg) with T/Cvolume ratios of 0.37, 0.39, and 0.33, respectively. 225Ac-pelgi was less myelosuppressive than 227Th-pelgi. 225Ac-pelgi showed dose-dependent treatment efficacy in the patient-derived KuCaP-1 model and strong combination potential with darolutamide in both cell line- (22Rv1) and patient-derived (ST1273) xenograft models. These results provide a strong rationale to investigate 225Ac-pelgi in patients with prostate cancer. A clinical phase 1 study has been initiated (NCT06052306).

PDIA2 has a dual function in promoting androgen deprivation therapy induced venous thrombosis events and castrate resistant prostate cancer progression.

Androgen deprivation therapy (ADT) is the first line of treatment for metastatic prostate cancer (PCa) that effectively delays the tumor progression. However, it also increases the risk of venous thrombosis event (VTE) in patients, a leading cause of mortality. How a pro-thrombotic cascade is induced by ADT remains poorly understood. Here, we report that protein disulfide isomerase A2 (PDIA2) is upregulated in PCa cells to promote VTE formation and enhance PCa cells resistant to ADT. Using various in vitro and in vivo models, we demonstrated a dual function of PDIA2 that enhances tumor-mediated pro-coagulation activity via tumor-derived extracellular vehicles (EVs). It also stimulates PCa cell proliferation, colony formation, and xenograft growth androgen-independently. Mechanistically, PDIA2 activates the tissue factor (TF) on EVs through its isomerase activity, which subsequently triggers a pro-thrombotic cascade in the blood. Additionally, TF-containing EVs can activate the Src kinase inside PCa cells to enhance the AR signaling ligand independently. Androgen deprivation does not alter PDIA2 expression in PCa cells but enhances PDIA2 translocation to the cell membrane and EVs via suppressing the clathrin-dependent endocytic process. Co-recruitment of AR and FOXA1 to the PDIA2 promoter is required for PDIA2 transcription under androgen-deprived conditions. Importantly, blocking PDIA2 isomerase activity suppresses the pro-coagulation activity of patient plasma, PCa cell, and xenograft samples as well as castrate-resistant PCa xenograft growth. These results demonstrate that PDIA2 promotes VTE and tumor progression via activating TF from tumor-derived EVs. They rationalize pharmacological inhibition of PDIA2 to suppress ADT-induced VTE and castrate-resistant tumor progression.

Impact of disease volume on survival efficacy of triplet therapy for metastatic hormone-sensitive prostate cancer: a systematic review, meta-analysis, and network meta-analysis.

Triplet therapy, androgen receptor signaling inhibitors (ARSIs) plus docetaxel plus androgen-deprivation therapy (ADT), is a novel guideline-recommended treatment for metastatic hormone-sensitive prostate cancer (mHSPC). However, the optimal selection of the patient most likely to benefit from triplet therapy remains unclear. We performed a systematic review, meta-analysis, and network meta-analysis to assess the oncologic benefit of triplet therapy in mHSPC patients stratified by disease volume and compare them with doublet treatment regimens. Three databases and meeting abstracts were queried in March 2023 for randomized controlled trials (RCTs) evaluating patients treated with systemic therapy for mHSPC stratified by disease volume. Primary interests of measure were overall survival (OS). We followed the PRISMA guideline and AMSTAR2 checklist. Overall, eight RCTs were included for meta-analyses and network meta-analyses (NMAs). Triplet therapy outperformed docetaxel plus ADT in terms of OS in both patients with high-(pooled HR: 0.73, 95%CI 0.64-0.84) and low-volume mHSPC (pooled HR: 0.71, 95%CI 0.52-0.97). There was no statistically significant difference between patients with low- vs. high-volume in terms of OS benefit from adding ARSI to docetaxel plus ADT (p = 0.9). Analysis of treatment rankings showed that darolutamide plus docetaxel plus ADT (90%) had the highest likelihood of improved OS in patients with high-volume disease, while enzalutamide plus ADT (84%) had the highest in with low-volume disease. Triplet therapy improves OS in mHSPC patients compared to docetaxel-based doublet therapy, irrespective of disease volume. However, based on treatment ranking, triplet therapy should preferably be considered for patients with high-volume mHSPC while those with low-volume are likely to be adequately treated with ARSI + ADT.

Abstract CT224: Preliminary efficacy and safety results from the (TATCIST) trial: A PSMA-directed targeted alpha therapy with FPI-2265 (225Ac-PSMA-I&amp;T) for the treatment of metastatic castration-resistant prostate cancer (mCRPC)

Abstract INTRODUCTION: Targeted α therapy (TAT) in mCRPC is a rapidly advancing class of radiotherapeutics that can effectively deliver potent and local radiation selectively to cancer cells while sparing the surrounding normal cells. Retrospective studies of 225Ac PSMA-RLT (radioligand therapy), have shown promise in pts with mCRPC, where activity correlates with disease characteristics and prior therapies. FPI-2265 (225Ac-PSMA-I&amp;T) consists of a small-molecule PSMA-targeting ligand coupled with a 225Ac radionuclide. Here we present the initial results from TATCIST, an ongoing, open-label, single-arm study (NCT05219500) to evaluate the efficacy and safety of FPI-2265 in pts with mCRPC that was initiated as an investigator-sponsored study then converted into an industry-sponsored trial with more stringent eligibility criteria. METHODS: Eligible pts are required to have progressive mCRPC with PSMA-positive PET. Prior radioligand therapy is permitted. Pts with skeletal metastases presenting as a superscan were excluded upon protocol amendment and excluded from this analysis. Four doses of FPI-2265 at 100 kBq/kg (±10%) are administered at 8-week intervals; de-escalation in cycle 2 and beyond is allowed. Proportion of pts with PSA ≤50%, maximum %PSA decrease, and safety and tolerability of FPI-2265 were assessed. RESULTS: At the time of the data cut (30Jan2024) 30 pts have received ≥1 dose FPI-2265, with 25 pts having ≥12 weeks follow up. For this analysis, 21 pts were evaluable for safety and 20 pts were evaluable for PSA response: 4 pts with superscan were excluded and 1 pt was excluded due to uninterpretable PSA data. In general, pts were heavily pretreated in terms of prior lines of therapy. Most pts (17/21 [81%]) had received a prior taxane, including 8 pts who received ≥2 lines of taxanes. Eight pts received prior 177Lu PSMA-RLT (Lu). PSA50 was achieved in 10/20 pts (50%); In a subset of pts with the baseline PSMA SUVmean &amp;gt;6 (n=13 overall; post-Lu, n=6), PSA50 was achieved in 9 pts (69%). Treatment-related adverse events (TRAEs) included dry mouth (18/21 [86%]), fatigue (10/21 [48%]) dry eye (6/21 [28%]), and anemia (6/21 [28%]). All were Grade 1-2 in severity, expect anemia Grade 3 which was observed in (5/21 [24%]). Other Grade 3 TRAEs included decreased platelet count (3/21 [14%]). No Grade 4 or 5 TRAEs were reported. Dry mouth was primarily Grade 1 (13/21 [62%]) with only 5 patients (24%) experiencing Grade 2 dry mouth; there were no related discontinuations. CONCLUSION: Preliminary efficacy and safety data as of 30Jan24 suggest that FPI-2265 is active in heavily pretreated pts with progressive mCRPC, including pts who received prior Lu therapy. Higher PSMA SUVmean was associated with improved PSA responses, Safety and tolerability were consistent with other published studies of 225Ac-PSMA-RLTs. These initial results support further investigation of FPI-2265 and a new phase 2/3 trial will begin enrolling soon. Citation Format: Ebrahim S. Delpassand, Mohammad Jawed Hashmi, Julia Kazakin, Omer Nawaz, Gabriella Garufi, Joanne Schindler, Luke Nordquist. Preliminary efficacy and safety results from the (TATCIST) trial: A PSMA-directed targeted alpha therapy with FPI-2265 (225Ac-PSMA-I&amp;T) for the treatment of metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT224.

Genomic profiling and clinical utility of circulating tumor DNA in metastatic prostate cancer: SCRUM-Japan MONSTAR SCREEN project

BackgroundCirculating tumor DNA (ctDNA) testing has emerged as a novel tool for cancer precision medicine. This study investigated the genomic profiling and clinical utility of ctDNA in metastatic prostate cancer.MethodsThis is a nation-wide prospective observational study. Patients treated with systemic treatment for metastatic castration-sensitive prostate cancer (mCSPC) and metastatic castration-resistant prostate cancer (mCRPC) were included. ctDNA was analyzed using FoundationOne Liquid®CDx at enrollment. In a subset of patients, ctDNA after disease progression and tissue prior to the initiation of treatment were examined using FoundationOne Liquid®CDx and FoundationOne®CDx, respectively.ResultsThe frequency of AR alterations and homologous recombination repair (HRR) defect was higher in mCRPC compared with mCSPC. Tumor mutational burden was correlated between tissue and ctDNA at pre-treatment, as well as ctDNA between at pre-treatment and at post-treatment. Patients with HRR defect were associated with shorter time to castration resistance in androgen deprivation therapy/combined androgen blockade, but not in androgen receptor pathway inhibitor, compared with patients without HRR defect in mCSPC. Time to treatment failure in patients with AR amplification or AR mutation was shorter compared with patients without AR alterations in mCRPC.ConclusionsThis study revealed valuable findings for the clinical care of metastatic prostate cancer. Especially, predictive factors such as HRR defect in mCSPC should be validated in the future.

Targeted interleukin-2 enhances the in vivo anti-cancer activity of Pluvicto™.

Pluvicto™ ([177Lu]Lu-PSMA-617), a radioligand therapeutic targeting prostate-specific membrane antigen (PSMA), has been recently approved for the treatment of metastatic castration-resistant prostate cancer (mCRPR). The drug suffers from salivary gland and kidney uptake that prevents its dose escalation to potentially curative doses. In this work, we sought to potentiate the in vivo anti-cancer activity of Pluvicto™ by combining it with L19-IL2, a clinical-stage investigational medicinal product based on tumor-targeted interleukin-2. We established a new PSMA-expressing model (HT-1080.hPSMA) and validated it using a fluoresceine analogue of PSMA-617 (compound 1). The HT-1080.hPSMA model was used to study the saturation and tumor retention of Pluvicto™ (compound 2) and to run combination therapy studies with L19-IL2. To complement our understanding of the mechanism of action of this novel combination, we conducted proteomics experiments on tumor samples after therapy with Pluvicto™ alone or in combination with the immunocytokine. High, selective, and long-lived tumor uptake was observed for Pluvicto™ (2) in the novel HT-1080.hPSMA model. Therapy studies in HT-1080.hPSMA tumor-bearing mice revealed that the combination of Pluvicto™ (2) plus L19-IL2 mediated curative and durable responses in all animals. Potent in vivo anti-cancer activity was observed solely for the combination modality, at doses that were well tolerated by treated animals. Proteomics studies indicated that L19-IL2 boosts the activation of the immune system in animals pre-treated with Pluvicto™. The therapeutic efficacy of Pluvicto™ at low radioactive doses can be effectively enhanced by the combination with L19-IL2. Our findings warrant further clinical exploration of this novel combination modality.

Recomendaciones de tratamiento en el cáncer de próstata hormonosensible metastásico: selección de pacientes

The standard treatment for metastatic hormone-sensitive prostate cancer (mHSPC) is now a combination of androgen deprivation therapy plus an androgen receptor-targeted therapy (abiraterone, apalutamide, enzalutamide or darolutamide), with or without chemotherapy (docetaxel). The selection of suitable patients for each therapeutic approach has become a determining factor to ensure efficacy and minimize side effects. This article combines recent clinical evidence with the accumulated experience of experts in medical oncology, radiation oncology and urology, to provide a comprehensive view and therapeutic recommendations for mHSPC.

Tolerability of Olaparib Combined with Abiraterone in Patients with Metastatic Castration-resistant Prostate Cancer: Further Results from the Phase 3 PROpel Trial

BackgroundThe PROpel study (NCT03732820) demonstrated a statistically significant progression-free survival benefit with olaparib plus abiraterone versus placebo plus abiraterone in the first-line metastatic castration-resistant prostate cancer (mCRPC) setting, irrespective of homologous recombination repair mutation status. ObjectiveWe report additional safety analyses from PROpel to increase clinical understanding of the adverse-event (AE) profiles of olaparib plus abiraterone versus placebo plus abiraterone. Design, setting, and participantsA randomised (1:1), double-blind, placebo-controlled trial was conducted at 126 centres in 17 countries (October 2018–January 2020). Patients had mCRPC and no prior systemic mCRPC treatment. InterventionOlaparib (300 mg bid) or placebo with abiraterone (1000 mg od) plus prednisone/prednisolone (5 mg bid). Outcome measurements and statistical analysisThe data cut-off date was July 30, 2021. Safety was assessed by AE reporting (Common Terminology Criteria for Adverse Events v4.03) and analysed descriptively. Results and limitationsThe most common AEs (all grades) for olaparib plus abiraterone versus placebo plus abiraterone were anaemia (46.0% vs 16.4%), nausea (28.1% vs 12.6%), and fatigue (27.9% vs 18.9%). Grade ≥3 anaemia occurred in 15.1% versus 3.3% of patients in the olaparib plus abiraterone versus placebo plus abiraterone arm. The incidences of the most common AEs for olaparib plus abiraterone peaked early, within 2 mo, and were managed typically by dose modifications or standard medical practice. Overall, 13.8% versus 7.8% of patients discontinued treatment with olaparib plus abiraterone versus placebo plus abiraterone because of an AE; 3.8% versus 0.8% of patients discontinued because of anaemia. More venous thromboembolism events were observed in the olaparib plus abiraterone arm (any grade, 7.3%; grade ≥3, 6.8%) than in the placebo plus abiraterone arm (any grade, 3.3%; grade ≥3, 2.0%), most commonly pulmonary embolism (6.5% vs 1.8% for olaparib plus abiraterone vs placebo plus abiraterone). ConclusionsOlaparib plus abiraterone has a manageable and predictable safety profile. Patient summaryThe PROpel trial showed that in patients who had not received any previous treatment for metastatic castration-resistant prostate cancer, olaparib combined with abiraterone was more effective in delaying progression of the disease than abiraterone alone. Most side effects caused by combining olaparib with abiraterone could be managed with supportive care methods, by pausing olaparib administration for a short period of time and/or by reducing the dose of olaparib.

Symptoms and quality of life among men starting treatment for metastatic castration-resistant prostate cancer – a prospective multicenter study

BackgroundMen with metastatic castration-resistant prostate cancer (mCRPC) have an incurable disease. Along with prolonging life, symptom management is one of the main goals with treatment. This is also important from a palliative care perspective where the life prolonging outcomes should be balanced with quality of life (QoL) in this late phase. It is also essential in symptom management to view different dimensions of symptoms, for example how severe or distressing symptoms are, to support best QoL. Therefore, more knowledge is needed about the symptom experience when these treatments are initiated and thus the aim of this study was to describe different dimensions of symptoms in men with mCRPC starting their first-line of life-prolonging treatment, and to describe the association between symptom burden and QoL.MethodsBaseline data from a prospective longitudinal study of 143 men with mCRPC starting their first-line life-prolonging treatment were used. Symptoms were measured using the Memorial Symptom Assessment Scale (MSAS) and global QoL was measured by the EORTC QLQ C-30. Data was analyzed using descriptive- and multivariable linear regression analyses.ResultsOn average, the men had more than 10 symptoms (range 0–31 of 33). 50% or more reported sweats, lack of energy, pain, problems with sexual activity and sexual desire. The symptoms they reported as most severe, or most distressing were not always the ones that were reported as most frequent. There was an association between QoL and physical symptoms, and also between QoL, and analgesic use and prostate-specific antigen (PSA) values.ConclusionEven if some men with mCRPC report many symptoms, the dimensions of severity and distress levels vary, and the most frequent symptoms was not always the most burdensome or distressing. There was an association between high physical symptom burden and QoL, suggesting that it is not the number of symptoms that affects QoL but rather the subjective perceived impact of the physical symptoms experienced. The knowledge of how men with mCRPC experience and perceive their symptoms may help health care professionals in symptom management aiming to improve QoL, which is a cornerstone in integrating early palliative care.

Abstract 6033: Preclinical evaluation of an actinium-225 labeled PSMA-targeting small molecule (225Ac-PSMA-Trillium (BAY 3563254)) for the treatment of metastatic castration resistant prostate cancer (mCRPC)

Abstract PSMA is a clinically validated target for the treatment of mCRPC. Since the linear energy transfer and degree of induced DNA damage of alpha particles far exceeds that of beta particles, several investigational PSMA-targeted small molecules labeled with the alpha-emitter actinium-225 (225Ac) have shown encouraging clinical signs of efficacy. However, xerostomia is often found as a dose-limiting side effect, presumably due to low levels of PSMA expression and efficient uptake of small molecules in salivary glands. To reduce these unwanted side effects a PSMA-targeted radioligand comprising a triad of important features was investigated. It consists of a high-affinity PSMA binder for specific tumor-targeting; a customized albumin-binding moiety designed to prolong plasma residence time and increase the therapeutic index by improving tumor uptake while reducing salivary gland uptake; and a chelator for efficient complexation of 225Ac. From a series of compounds containing the same high-affinity PSMA-targeting moiety, but different chain lengths and albumin-binding domains, compound RPS-072 containing a PEG-3 and PEG-8 chain and an iodobenzyl moiety as albumin-binder was selected for further evaluation (J Nucl Med 2019; 60:656-663). This compound was the basis for the PSMA-Trillium with a DOTA chelator for imaging applications in humans (NCT05773703) or a macropa chelator for 225Ac labeling resulting in 225Ac-PSMA-Trillium. In vitro preclinical characterization of 225Ac-PSMA-Trillium was performed to test affinities for PSMA and albumin. In a SPR assay, Kd was measured as 4.88x1011 M, Kon as 1.4x107 1/Ms and Koff as 6.6x10-4 1/Ms. 225Ac-PSMA-Trillium demonstrated good stability up to 48 h and induced potent in vitro cytotoxicity in the LNCaP subclone C4-2 (0.114 kBq/ml). In vivo biodistribution of 225Ac-PSMA-Trillium showed consistent with the albumin binding property a relatively slow pharmacokinetics profile with 5 % ID/g still in the blood after 24 h and tumor accumulation peaking at ~ 20 % ID/g after 5-7 days. Tumor penetration was investigated using autoradiography which demonstrated fast, homogeneous, and even distribution across the tumor within 15 mins after injection. This property was also reflected by strong therapeutic efficacy in several PrCa models. In the LNCaP model a tumor growth inhibition was observed at a single dose dependent efficacy at 150 kBq/kg and 300 kBq/kg and increased the time to reach 400 mm3 by 35 days for the 300 kBq/kg group. In the androgen independent PDX KuCaP-1 model, a single dose of 250 kBq/kg 225Ac-PSMA-Trillium induced strong tumor growth inhibition over the course of 35 days. A first-in-human trial with 225Ac-PSMA-Trillium is anticipated to start in the first half of 2024. Citation Format: Sabine Zitzmann-Kolbe, Alex Papple, Thorsten Poethko, Ingrid Moen, Christoph Schatz, Shawn Hillier, John W. Babich, Alan Cuthbertson, Urs B. Hagemann. Preclinical evaluation of an actinium-225 labeled PSMA-targeting small molecule (225Ac-PSMA-Trillium (BAY 3563254)) for the treatment of metastatic castration resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6033.

Abstract 6285: Defining androgen receptor function and the effects of PARP inhibition in BRCA1/2-deficient vs. proficient prostate cancer

Abstract Mutation or loss of the tumor suppressor genes BRCA1 and BRCA2 promotes the development of aggressive prostate cancer with poor outcomes and a high risk of metastatic relapse. Approximately 15% of metastatic prostate tumors are BRCA1/2-deficient. These tumors are frequently resistant to standard-of-care treatments that block androgen receptor (AR) function, although the mechanisms underlying this effect remain unclear. PARP inhibitors are synthetically lethal with BRCA1/2-deficiency and are commonly used as a late-line treatment in metastatic prostate cancer; however, both preclinical and clinical data have provided conflicting results on whether PARP inhibitors can be effective in BRCA1/2-proficient prostate tumors. BRCA1, BRCA2, PARP-1, and PARP-2 all have proposed roles in regulating transcription and the chromatin landscape. We therefore hypothesized that loss of BRCA1, BRCA2, and/or inhibition of PARP modulates AR function through changes in global chromatin structure and transcriptional pathways. We used patient-derived xenograft models and next-generation sequencing techniques to profile AR function in BRCA1/2-deficient vs. proficient prostate tumors. We found that loss of BRCA1 and BRCA2 is associated with chromatin accessibility changes, and differentially accessible regions correlate with DNA binding motifs for AR and AR cofactors. ChIP-seq for AR in these tumors demonstrated that BRCA1/2-deficiency is associated with an altered AR cistrome and a global decrease in AR genomic binding. Corresponding RNA-seq data confirmed a downregulated androgen response in BRCA1/2-deficient tumors. In cell line models, inhibition of PARP1 and PARP1/2 inhibited AR-driven transcription. Combining PARP inhibition with either androgen deprivation or the AR antagonist enzalutamide dampened the growth-inhibitory effects of PARP inhibitor treatment. Together, these results indicate that BRCA1/2-deficiency and PARP inhibition modulate AR function in prostate cancer. Citation Format: Nicole A. Traphagen, Esme Wheeler, Rong Li, Xintao Qiu, Myles Brown. Defining androgen receptor function and the effects of PARP inhibition in BRCA1/2-deficient vs. proficient prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6285.

Abstract 6962: Shed Trop2 drives prostate cancer progression and Trop2 is a novel tissue prognostic biomarker and a candidate urinary marker for prostate cancer

Abstract Distinguishing indolent from clinically significant localized prostate cancer and treatment of metastatic prostate cancer are two major clinical challenges in prostate cancer. The development of novel predictive biomarkers will help with risk stratification, and influence clinical decision-making between treatment and active surveillance, leading to a decrease in over or under-treatment of patients with prostate cancer. Here, we report that Trop2, an oncogenic transmembrane surface protein, is a prognostic tissue biomarker for clinically significant prostate cancer by utilizing the Canary Prostate Cancer Tissue Microarray (CPCTA) cohort composed of over 1100 patients from a multi-institutional study. We demonstrate that higher Trop2 expression is correlated with worse clinical features and elevated Trop2 expression at radical prostatectomy predicts worse overall survival in men undergoing radical prostatectomy. Additionally, we detected shed Trop2 in urine from men with clinically significant prostate cancer. We further define the functional role of shed Trop2 on metastasis in prostate cancer and identify that shed Trop2 increases cell migration, invasion, metastatic colonization, and spontaneous metastasis in vitro and in vivo. Proteomic profiling reveals that shed Trop2 modulates a set of proteins associated with invasion, migration, mTOR signaling, and epithelial-to-mesenchymal transition. shed Trop2 binds to EGFR and results in the activation of the EGFR-PI3K-AKT-mTOR pathway in prostate cancer. Our study reveals the new function of shed Trop2 in driving prostate cancer progression and identifies Trop2 as a novel tissue prognostic biomarker and a candidate non-invasive marker for prostate cancer that could be used to optimize treatment decision-making. Citation Format: Shiqin Liu, Sarah Hawley, Christian Kunder, En-Chi Hsu, Michelle Shen, Merve Aslan, Fernando J. Marques, Chung S. Lee, Abel Bermudez, Lennart Westphalen, Heidi Auman, Lisa F. Newcomb, Daniel W. Lin, Peter S. Nelson, Ziding Feng, Maria S. Tretiakova, Lawrence D. True, Funda Vakar-Lopez, Peter R. Carroll, Jeffry Simko, Martin E. Gleave, Dean A. Troyer, Jesse K. McKenney, Donna Peehl, Sharon J. Pitteri, James D. Brooks, Michael A. Liss, Tanya Stoyanova. Shed Trop2 drives prostate cancer progression and Trop2 is a novel tissue prognostic biomarker and a candidate urinary marker for prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6962.

Abstract 1904: Preclinical development of MGC026, a glycan-linked, exatecan-based antibody-drug conjugate (ADC) targeting B7-H3 for solid cancer

Abstract Introduction: Antibody-drug conjugates (ADCs) have emerged as an important class of therapeutic agents for the treatment of cancer. A duocarmycin-based B7-H3-targeted DNA-alkylating ADC, vobramitamab duocarmazine (vobra duo), has shown encouraging clinical activity in the treatment of metastatic castration-resistant prostate cancer. Given the broad spectrum of tumor indications addressable by targeting B7-H3, we developed MGC026, an ADC incorporating a B7-H3-targeting antibody and a novel glycan-linked topoisomerase 1 inhibitor (TOP1i). With distinct mechanisms of action, vobra duo and MGC026 can address different cancers, tumor stages, or be used in combination with alternate agents to enhance their clinical utility. Methods: MGC026 is comprised of the cleavable linker-payload, bicyclononyne carbamoyl sulfamide Val-Ala-PABC exatecan (SYNtecan E™) site-specifically conjugated at asparagine 297 of the heavy chain through enzymatic glycan remodeling and metal-free click chemistry, using Synaffix’s GlycoConnect™ technology. In vivo efficacy studies were conducted in immunodeficient mice with human tumor cell-line or patient-derived xenografts to identify the spectrum of MGC026-sensitive tumors and the relationship between exposure and antitumor activity. A toxicology study was conducted in cynomolgus monkeys in which MGC026 was administered by 15-minute IV infusion once every three weeks. Pharmacokinetic (PK) analysis and detailed toxicology evaluation was performed. Results: MGC026 demonstrated specific, dose-dependent in vivo antitumor activity toward B7-H3-positive tumor xenografts representing lung, pancreatic, and prostate cancers, head and neck squamous cell carcinoma, and melanoma. Additionally, MGC026 demonstrated antitumor activity toward B7-H3-positive patient-derived xenograft models of lung and prostate cancer, with additional indications under investigation. MGC026, administered to cynomolgus monkeys at dose levels of 10, 30, and 50 mg/kg every 3 weeks for a total of 3 doses, exhibited approximate dose-proportional PK and high stability in circulation. MGC026 was well tolerated, with no lung toxicity observed, and the highest dose level tested (50 mg/kg) was declared as the highest non-severely toxic dose. Conclusions: MGC026 exhibited a favorable preclinical profile, with potent in vivo activity toward B7-H3-expressing tumor xenografts representing a range of cancer indications. MGC026 was tolerated in cynomolgus monkeys, a relevant toxicology model, at exposure levels exceeding those required for antitumor activity. These data support clinical development of MGC026 for the treatment of B7-H3-expressing solid cancers. Citation Format: Juniper A. Scribner, Jennifer G. Brown, Thomas Son, Linda Jin, Carroll McKenzie, Viktoriya Nam, Curtis Bush, Dienis Quinonez, James Tamura, Sergey Gorlatov, Hua Li, Shelley Butler, Ezio Bonvini, Deryk Loo. Preclinical development of MGC026, a glycan-linked, exatecan-based antibody-drug conjugate (ADC) targeting B7-H3 for solid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1904.

Evaluation of two-dimensional total bone uptake (2D-TBU) and bone scan index (BSI) extracted from active bone metastatic burden on the bone scintigraphy in patients with radium-223 treatment.

Radium-223 is a first alpha-emitting radionuclide treatment for metastatic castration-resistant prostate cancer (mCRPC) patients with bone metastases. Although the spread-based bone scan index (BSI) and novel index of the intensity-based two-dimensional total bone uptake (2D-TBU) from bone scintigraphy may provide useful input in radium-223 treatment, they have not been evaluated in detail yet. This study aimed to fill this gap by evaluating BSI and 2D-TBU in patients treated with radium-223. Twenty-seven Japanese patients with mCRPC treated with radium-223 were retrospectively analyzed. The patients were evaluated via blood tests and bone scans at baseline and 3 cycles intervals of treatment. BSI and 2D-TBU were analyzed via VSBONE BSI in terms of correlations, response to radium-223 treatment, association with treatment completion, and the Kaplan-Meier survival analysis was performed. Nineteen patients (70.4%) completed six cycles of radium-223 treatment, whereas eight patients (29.6%) did not complete the treatment regimen. A significant difference in baseline BSI and 2D-TBU was observed between these groups of patients. Both BSI and 2D-TBU were highly correlated (r = 0.96, p < 0.001). Univariate analysis showed an association between radium-223 completion in median BSI and 2D-TBU values (p = 0.015) and completion percentage differences (91.7% vs. 45.5%; p = 0.027). The Kaplan-Meier product limit estimator showed that the median overall survival was 25.2 months (95% CI 14.0-33.6 months) in the completion group and 7.5 months (95% CI 3.3-14.2 months) in the without completion group (p < 0.001). The overall survival based on median cutoff levels showed a significant difference in 2D-TBU (p = 0.007), but not in BSI (p = 0.15). The 2D-TBU may offer advantages over BSI in classifying patients towards radium-223 treatment based on the degree of progression of bone metastases. This study supports the importance of preliminary assessment of bone metastasis status using BSI and 2D-TBU extracted from VSBONE BSI for radium-223 treatment decisions.

Bilateral Choroidal Detachments following Novel CAR T-Cell Immunotherapy Regimen.

To describe a vision-threatening adverse event of a novel CAR T-cell immunotherapy for metastatic prostate cancer. Observational Case Report. 77-year-old male with history of metastatic prostate cancer and pulmonary embolism enrolled in a clinical trial investigating the use of CAR T-cell immunotherapy for treatment of metastatic prostate cancer presented with a subjective left temporal visual disturbance. The patient was found to have bilateral extensive choroidal detachments on examination. OCT macula demonstrated no intraretinal fluid or supraretinal fluid in both eyes. B-scan of both eyes redemonstrated choroidal detachments in both eyes and no retinal detachment in either eye. The patient was initiated on a topical and systemic steroid regimen and experienced symptomatic and clinical improvement. We exhibit a case of bilateral choroidal detachments secondary to systemic reaction to a novel immunotherapy for metastatic cancer successfully treated with systemic and topical steroids. Close follow up may be required for patients receiving similar novel immunotherapeutic regimens.

Three- and Seven-month Prostate-specific Antigen Levels as Prognostic Markers for Overall Survival in Metastatic Hormone-sensitive Prostate Cancer: Results from SWOG S1216, a Phase 3 Randomized Trial of Androgen Deprivation Plus Orteronel or Bicalutamide

BackgroundA robust decrease in prostate-specific antigen (PSA) in response to androgen deprivation therapy (ADT) has been evaluated as a prognostic factor in patients with metastatic hormone-sensitive prostate cancer (mHSPC) since 2006, but the treatment of mHSPC has since evolved to include intensified therapy. ObjectiveWe assessed the association of PSA levels at 3 (PSA-3mo) and 7 (PSA-7mo) mo with overall survival (OS) in patients with mHSPC treated with ADT combined with either bicalutamide or orteronel in the S1216 phase 3 clinical trial. Design, setting, and participantsPSA responses to treatment of patients in the S1216 trial were categorized as: complete response (CR) if PSA was ≤0.2 ng/ml, partial response if PSA was >0.2 and ≤4 ng/ml, and no response (NR) if PSA was >4 ng/ml. Outcome measurements and statistical analysisA Cox analysis (adjusted for treatment arm and three stratification factors: performance status, severity of disease, and early vs late induction) was used for OS association. While PSA-7mo association was a prespecified objective, PSA-3mo association was also evaluated. Results and limitationsA total of 1251 and 1231 patients from the S1216 study were evaluable for PSA-3mo and PSA-7mo, respectively. A PSA-7mo CR was associated with improved OS compared with NR (HR: 0.20; p < 0.0001). A PSA-3mo CR showed a similar association to NR (HR: 0.34; p < 0.0001). The association of a PSA response with survival did not differ by treatment arm at either time point. ConclusionsThe PSA-3mo and PSA-7mo responses were strongly associated with OS; taken with other emerging prognostic biomarkers, these markers may allow for early identification of patients at the highest risk of death, aid with counseling in clinical practice, and permit design of future clinical trials targeting these patients. Patient summaryA low prostate-specific antigen level at 3 or 7 mo after starting treatment for metastatic hormone-sensitive prostate cancer predicts longer survival regardless of the first treatment given with androgen deprivation therapy.