Activity In mCRPC Research Articles

Randomized Phase II Study of Durvalumab with or without Tremelimumab in Patients with Metastatic Castration Resistant Prostate Cancer.

Programmed death-ligand 1 (PD-L1) is overexpressed by dendritic cells in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing on androgen receptor pathway inhibitors. We tested whether checkpoint blockade could enhance antitumor activity in mCRPC. In a multicenter open-label non-comparative randomized phase II study, patients with mCRPC treated with £ 1 prior cytotoxic chemotherapy, with measurable disease and progression on abiraterone and/or enzalutamide were randomized to durvalumab (D) 1500mg IV Q4 weeks ± 4 doses of tremelimumab (T) 75mg IV. The primary endpoint was objective response (OR) by iRECIST using a Simon 2-stage design. Correlative testing included PD-L1/CD8 immunohistochemistry on baseline tumour biopsies and deep targeted sequencing of plasma cell-free DNA. 52 patients were enrolled. Median age was 70 years (range, 50-83 years) and 52% had prior taxane therapy for mCRPC. In stage 1, 13 patients were randomized to D with no OR observed. D+T advanced to stage 2 with 39 patients enrolled (receiving a median 3 cycles, range 1-53). D+T related adverse events (AEs) were mainly £ grade 2 but led to discontinuation in 7 patients . There were seven OR (19.4% [95% confidence interval: 8.2-36.0%]; intention to treat (ITT) 17.9% [95% confidence interval: 7.5-33.5%]). Five responding tumours were PD-L1 positive and two exhibited DNA damage repair defects. Responses were observed without high tumour mutational burden or other genomic indices of immunotherapy sensitivity. D+T is active in mCRPC but patient selection remains a challenge. Further studies to develop predictive biomarkers are warranted.

Carboplatin in metastatic castration-resistant prostate cancer patients with molecular alterations of the DNA damage repair pathway: the PRO-CARBO phase II trial.

DNA damage repair genes are altered in 20-35% of metastatic castration-resistant prostate cancer (mCRPC). Poly-ADP (Adénosine Diphosphate)-ribose polymerase inhibitors (PARPi) showed significant activity for these selected tumors, especially with homologous recombination repair (HRR) deficiency. These alterations could also predict platinum sensitivity. Although carboplatin was inconclusive in unselected mCRPC, the literature suggests an anti-tumoral activity in mCRPC with HHR gene alterations. We aimed to assess the efficacy of carboplatin monotherapy in mCRPC patients with HRR deficiency. This prospective multicenter single-arm two-stage phase II addressed mCRPC men with HRR somatic and/or germline alterations, pretreated with ⩾2 taxane chemotherapy regimens and one androgen receptor pathway inhibitor. Prior PARPi treatment was allowed. Enrolled patients received intravenous carboplatin (AUC5) every 21 days for 6-9 cycles. The primary endpoint was the best response rate according to adapted PCWG3 guidelines: radiological response (RECIST 1.1 criteria) and/or biological response [⩾50% prostate-specific antigen (PSA) decline]. A total of 15 out of 16 enrolled patients started carboplatin treatment. Genomic alterations were identified for BRCA2 (n = 5), CDK12 (n = 3), ATM (n = 3) CHEK2 (n = 2), CHEK1 (n = 1), and BRCA1 (n = 1) genes. Objective response (partial biological response + stable radiological response) was achieved in one patient (6.7%), carrying a BRCA2 mutation and not pre-treated with PARPi; stable disease was observed for five patients (33.5%). Among seven patients (46.7%) with previous PARPi treatment, four patients (57.1%) had a stable disease. The median progression-free and overall survivals were 1.9 [95% confidence interval (95% CI), 1.8-9.5] and 8.6 months (95% CI, 4.3-19.5), respectively. The most common severe (grade 3-4) treatment-related toxicities were thrombocytopenia (66.7%), anemia (66.7%), and nausea (60%). Overall, 8 (53.3%) patients experienced a severe hematological event. The study was prematurely stopped as pre-planned considering the limited activity of carboplatin monotherapy in heavily pre-treated, HHR-deficient mCRPC patients. Larger experience is needed in mCRPC with BRCA alterations. NCT03652493, EudraCT ID number 2017-004764-35.

A phase 1/2 study of combination olaparib and radium-223 in men with metastatic castration-resistant prostate cancer with bone metastases (COMRADE): A trial in progress.

TPS5110 Background: Radium-223, an α-emitting radioisotope inducing DNA double-stranded breaks leading to cell death has demonstrated improvement in overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC) with bone metastases. PARP inhibitors prevent the repair of DNA single-stranded breaks and have demonstrated clinical efficacy as monotherapy in mCRPC patients harboring alterations in the homologous recombination repair (HRR) pathway and in combination with androgen receptor signaling inhibitors irrespective of DNA repair mutation status. In preclinical models, PARP inhibitors have shown efficacy as radio sensitizing agents. We designed a phase 1/2 trial to identify the recommended phase 2 dose (RPD2) of olaparib and radium-223 and test the hypothesis that radium-223 + olaparib will demonstrate anti-tumor activity in mCRPC irrespective of homologous recombination repair deficiency (HRD) status (NCT03317392). Methods: This open-label, multicenter, phase 1/2 study evaluates the dosing, safety and efficacy of olaparib with radium-223 in men with mCRPC with bone metastases. The phase 1 component used a 3+3 dose escalation design to determine the olaparib recommended phase 2 dose (RP2D) + fixed dose radium-223 (55 kBq/kg IV every 4 weeks x 6). The phase 1 portion has completed accrual (n = 12) and demonstrated that the RP2D of olaparib is 200 mg by mouth twice daily when combined with standard dose radium-223. The phase 2 component of the study which was activated in 1/2021 is an open-label, randomized trial (1:1) evaluating olaparib + radium-223 compared to radium-223 alone. The inclusion criteria include patients with mCRPC with any number of prior therapy lines for mCRPC and ≥2 bone metastases by imaging and at least 1 lesion which has not been treated with prior radiation. Patients with visceral metastases or malignant lymphadenopathy ( > 4 cm in short diameter) are excluded. The primary endpoint for phase 2 is radiographic progression-free survival (rPFS) per PCWG3 guidelines for bone metastases and RECIST v1.1 for non-bone disease. The integrated biomarker is Oncopanel assay to determine HRR status. A key secondary endpoint will evaluate rPFS in biomarker positive and negative patients. Other secondary endpoints include time to PSA progression, PSA response, time to subsequent therapy, time to first skeletal event, and OS. Exploratory endpoints include WES/WTS of baseline biopsy tissue, assessment of RAD51 IHC and correlation with outcomes, ctDNA assessment and correlation with responses, evaluation of changes in the tumor immune microenvironment, and quality of life assessment. Target accrual is 133 patients. Clinical trial information: NCT03317392 .

Final results from phase I study of PSCA-targeted chimeric antigen receptor (CAR) T cells in patients with metastatic castration resistant prostate cancer (mCRPC).

5019 Background: Chimeric antigen receptor (CAR)-engineered T cell therapies are being pursued for the treatment of mCRPC. Prostate Stem Cell Antigen (PSCA) is highly expressed on the surface membrane in mCRPC and with limited expression on normal tissues. We are completing a phase I study of PSCA-targeted 4-1BB-co-stimulated CAR T cell therapy in mCRPC. Methods: CAR T cells were manufactured at City of Hope’s cGMP facility. Patients (pts) were required to have disease progression after at least 1 androgen receptor targeted therapy but there was no limit on other prior treatments. The primary objective was to define the dose limiting toxicities (DLT) as well as to describe preliminary bioactivity and activity. CAR T persistence and cytokine levels were evaluated by flow cytometry and Luminex. Circulating tumor cells (CTC) were measured by an unselected assay (Kuhn). Results: 14 pts were treated, median age 69, median baseline PSA 88. 12(86%) had previously been treated with chemotherapy; 9 received two taxanes and 3 docetaxel only. 79% of screened pts had PSCA expression >2+ in >80% of cancer cells. Two of 6 pts encountered DLT (grade 3 cystitis) at 100M + lymphodepletion (LD) chemotherapy. The protocol was amended to reduce the LD dose to 300 mg/m2 cyclophosphamide D1-3. No DLTs occurred in 5 pts treated in the modified LD 100M cohort. Cytokine release syndrome (CRS), best response by RECIST, CAR T cell expansion and persistence are presented by dose level in the table. CAR T expansion was greater with LD than without. PSA declines were seen, as well as radiographic improvement, though RECIST response was limited to stable disease (SD) by concurrent bone metastases. Cytokine peaks were higher in patients with anti-tumor effect noted. CTC decreases in both marrow and peripheral blood were seen, associated with PSA declines. Conclusions: PSCA-CAR T cells have anti-cancer activity in mCRPC with DLT of cystitis. LD was required for greater expansion and activity; lower dose LD improved toxicity without clear negative impact on expansion. Clinical trial information: NCT03873805 . [Table: see text]

Abstract 1822: IFN-γ and TRAIL involvement in androgen signaling-mediated NK cell killing of prostate cancer cells and further enhancement by NKG2A checkpoint inhibition with monalizumab

Abstract Although blocking the androgen receptor (AR) pathway is a core treatment strategy in early prostate cancer, most patients progress to metastatic castration-resistant prostate cancer(mCRPC). Immunotherapy with PD-1/PD-L1 inhibition has limited activity in mCRPC. AR signaling modulates CD8+ T cells and antitumor immune responses in mCRPC. In a companion presentation (Schwermann et al., submitted AACR 2023), we demonstrate that AR blockade activates NK cell killing of prostate cancer (PC) cells. We hypothesize this activation requires IFN-γ and TRAIL pathways. We investigated the mechanisms of AR inhibitors (ARi)enzalutamide (Enza) and darolutamide (Daro) on the antitumor function of NK cells and potential enhancement with checkpoint inhibitors. Material and Methods: We performed ATP-based CellTiterGlo viability assays to investigate the effects of Enza and Daro on PC cells (LNCap, 22Rv1 [ARv7mutation], DU145, PC3 [AR-]) and NK-92 cells. We performed co-culture experiments with PC, NK, and T cells, at a 1:1 ratio, using IFN-γ blocking mAb (10 μg/ml), RIK-2 (TRAIL blocking mAb- 10 μg/ml) and analyzed immune cell-mediated tumor cell killing (ImageXpress Confocal HT). The NK cell immune checkpoint inhibitor monalizumab that targets NKG2A was combined with ARi. Results: Co-cultures of PC plus NK-92 cells with ARi significantly increased immune-mediated PCkilling within 24hrs (control[C]: 20%±1.9; Enza: 40%±4.3; Daro: 36%±3.72, p=0.0001). This immune enhancement effect was abolished by IFN-γ mAb. The combination of TRAIL inhibitory mAb with Enza decreased NK immune-mediated killing by 16±2.4% ([C]: 40%±4.3; Enza+RIK-2:25.6%±2.1, p=0.002). Treatment of PC cells plus NK cells with Enza, IFN-γ mAb, and TRAIL-blocking RIK-2 significantly reduced NK cell-mediated killing of PCs (control[C]: 20%±1.9, [T]:3.2%±2.6, p=0.003). ARi immune enhancement effect was increased by NKG2A blockade with monalizumab ([C]: 31.2%±3.1, [T]: 43.92%±4.52, p=0.0045). Conclusions: ARi promotes NK cell killing of PC cells via IFN-γ gamma and TRAIL. NK cell activation is enhanced by the combination of ARi and the checkpoint inhibitor monalizumab. Validation of these results in patient-derived organoids paired with tumor samples from patients with PC is ongoing to further understand the innate immune response and direct novel therapeutic strategies. Citation Format: Maximilian Schwermann, Lindsey Carlsen, Kelsey E. Huntington, Lanlan Zhou, Andrew George, Praveen Srinivasan, Vida Tajiknia, Arielle De La Cruz, Andre De Souza, Anthony E. Mega, Howard P. Safran, Benedito A. Carneiro, Wafik S. El-Deiry. IFN-γ and TRAIL involvement in androgen signaling-mediated NK cell killing of prostate cancer cells and further enhancement by NKG2A checkpoint inhibition with monalizumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1822.

Phase 2 study (AARDVARC) of AZD4635 in combination with durvalumab and cabazitaxel in patients (pts) with progressive metastatic castrate-resistant prostate cancer (mCRPC).

173 Background: Pts with mCRPC who progress on docetaxel and new hormonal agents (NHAs) have few therapeutic options. In the CARD study of cabazitaxel, 35.7% of pts had PSA responses and 36.5% of pts had tumor responses. While immune checkpoint inhibitors have limited single-agent activity in mCRPC, the combination of the adenosine 2A receptor antagonist, AZD4635, with durvalumab may improve response to chemotherapy. This study assessed AZD4635 in combination with durvalumab (Arm A) or with durvalumab + cabazitaxel (Arm B) in pts with mCRPC. We report interim analysis results from Arm B (Arm A to be reported elsewhere). Methods: Eligible pts had histologically confirmed mCRPC, disease progression ≤6 months prior to enrollment, and were previously treated with docetaxel and 1 NHA. Pts received AZD4635 75 mg PO QD + durvalumab 1500 mg IV Q3W + cabazitaxel Q3W (dosed per locally approved label) for up to 10 cycles. The primary endpoint was radiographic progression-free survival (rPFS), by RECIST v1.1 (soft tissue) or PCWG3 (bone). Secondary endpoints included safety, pharmacokinetics, confirmed PSA50 response, and objective response rate by RECIST v1.1. A futility analysis was planned based on PSA50 responses (confirmed + unconfirmed) after approximately 30 pts were treated. Results: As of August 10, 2021, 28 pts received AZD4635 + durvalumab + cabazitaxel, and 21 pts were still on treatment. Most common adverse events (AEs) possibly related to treatment were nausea (50.0%), diarrhea (46.4%), asthenia, and vomiting (each 28.6%). Treatment-related febrile neutropenia occurred in 7.1% pts. Twelve (42.9%) pts had a serious AE possibly related to treatment. One AE possibly related to treatment led to death (myositis). Exposures of cabazitaxel and/or durvalumab did not change when combined with AZD4635. Median rPFS was 4.4 months (95% CI: 4.2–not calculable) with low percent maturity. Of 28 PSA-evaluable pts, 8 (28.6%) had PSA50 responses (4 confirmed). There were 5 unconfirmed partial responses by RECIST v1.1. Conclusions: Although efficacy data are immature, enrollment was stopped for futility. Safety of the combination was consistent with the known safety profiles of the individual agents. Clinical trial information: NCT04089553 .

A phase II single-arm trial of niraparib in platinum-sensitive metastatic castration-resistant prostate cancer with DNA repair defects (PLATPARP).

TPS291 Background: Platinum-based chemotherapy, either as monotherapy or in combination with taxanes, is increasingly used for patients with metastatic castration-resistant prostate cancer (mCRPC) harboring germline and/or somatic homologous recombination repair gene mutations (HRRm). However, clinical responses with platinum-based therapy are often of limited duration and limited by cumulative toxicities. The PARP inhibitor (PARPi) olaparib is approved for the treatment of mCRPC patients with pathogenic HRRm after progression on enzalutamide or abiraterone. Importantly, sensitivity to platinum-based chemotherapy may predict improved clinical outcomes with PARPi, and ‘maintenance’ PARPi strategies are routinely used in patients with advanced ovarian and pancreatic malignancies with HRRm with initial clinical response to platinum chemotherapy. We hypothesize that maintenance niraparib, a PARPi with demonstrated activity in mCRPC with HRRm, will prolong clinical responses to platinum-based chemotherapy with acceptable toxicity in mCRPC patients harboring germline and/or somatic HRRm. Methods: We are conducting an open-label, single-arm, phase II study to evaluate the clinical benefit of maintenance niraparib in biomarker-defined, platinum-sensitive mCRPC patients. Eligible subjects harbor a pathogenic germline and/or somatic mutation in BRCA1/2, ATM, FANCA, CDK12, RAD51B, RAD54L, PALB2, CHEK2, HDAC2, or BRIP1 and have received at least 3 cycles (or minimum 9 weeks) of platinum-based chemotherapy for the treatment of mCRPC per investigator discretion. Following ³4 weeks since completion of chemotherapy, subjects without evidence of clinical or radiographic disease progression receive investigational treatment with maintenance niraparib (starting dose 200 mg daily). The primary objective is an improvement in 6 month PFS rate (PFS6) (H0: PFS6 rate 25%; H1: PFS6 rate 50%; power 0.77 with one-sided α = 0.05). Serial plasma samples are obtained for correlative analyses of markers of response and/or resistance to maintenance niraparib. Eight of a planned total of 18 subjects have enrolled (N=3 germline BRCA2; N=2 somatic BRCA2; N=1 germline PALB2; N=1 germline ATM; N=1 germline CHEK2). This study incorporates a novel, combined genetic and clinical patient-selection approach for PARPi therapy to optimize clinical outcomes. Clinical trial information: NCT04288687 .

Phase II trial evaluating olaparib maintenance in patients with metastatic castration resistant prostate cancer (mCRPC) after docetaxel treatment, reaching partial or stable response: SOGUG-IMANOL study.

168 Background: Prostate cancer is the second most common cancer in men. A number of important systemic therapies have been developed to treat mCRPC and now comprise the current therapeutic landscape. Docetaxel became the first systemic therapy to improve survival in these men in a randomized study demonstrating superiority versus mitoxantrone (18.9 months versus 16.5, p=0,004). But, inexorably, after stopping, disease progresses. Methods: A prospective phase II trial was designed to test Olaparib maintenance efficacy, in terms of progression free survival (PFS), in patients with mCRPC with DNA-repair defects that have achieved partial or complete response after being treated with systemic therapy (at least six cycles of docetaxel). Results: 134 mCRPC patients were included since Feb-2018 to Nov-2020 and were tested for DDR alterations. 19.4% of patients had somatic mutations (30.8% BRCA2, 3.8% BRCA1, 19.2% ATM, 7.7% CHEK2, 7.7% PALB2). 53,8% received Olaparib maintenance treatment, with a median follow-up of 23.3 months. Median age was 73 years. Median basal PSA was 17 ng/dL. 100% were metastatic (14.3% de novo and 85.7% relapsed after primary treatment), 78.6% had bone metastasis, 35.7% visceral and 35.7% adenopathies. 42.9% had previous treatment with abiraterone and 35.7% with enzalutamide. 46.2% received at least 8 cycles of docetaxel. 7.1% achieved a partial response and 92.9% a disease stabilization. Response to Olaparib treatment was 14.3% partial response, 71.4% stabilization and 7.1% disease progression.14.3% had a PSA50 decrease. Median duration of response was 8.27 months. Median PFS was 10.1 months. Median PSA-PFS was 3.5 months. G3/4 adverse events were 21.4% asthenia,14.3% anemia and 7.1% neutropenia. Conclusions: Olaparib maintenance after at least six cycles of docetaxel shows promising activity in mCRPC with DDR alterations, with an acceptable toxicity profile. Our pathogenic mutations percentage (19,4%) is in line with previous publications. Clinical trial information: NCT03434158 .

The Andrographolide Analogue 3A.1 Synergizes with Taxane Derivatives in Aggressive Metastatic Prostate Cancers by Upregulation of Heat Shock Proteins and Downregulation of MAT2A-Mediated Cell Migration and Invasion.

Conventional treatment with taxanes (docetaxel-DTX or cabazitaxel-CBZ) increases the survival rates of patients with aggressive metastatic castration-resistant prostate cancer (mCRPC); however, most patients acquire resistance to taxanes. The andrographolide analog, 19-tert-butyldiphenylsilyl-8,7-epoxy andrographolide (3A.1), has shown anticancer activity against various cancers. In this study, we investigated the effect of 3A.1 alone and in combination with DTX/CBZ against mCRPC and their mechanism of action. Exposure to 3A.1 alone exhibited a dose- and time-dependent antitumor activity in mCRPC. Chou-Talalay's combination index (CI) values of all 3A.1 + TX combinations were less than 0.5, indicating synergism. Co-treatment of 3A.1 with TX reduced the required dose of DTX and CBZ (P < 0.05). Caspase assay (apoptosis) results concurred with in vitro cytotoxicity data. RNA sequencing (RNAseq), followed by ingenuity pathway analysis (IPA), identified that upregulation of heat-shock proteins (Hsp70, Hsp40, Hsp27, and Hsp90) and downregulation of MAT2A as the key player for 3A.1 response. Furthermore, the top treatment-induced differentially expressed genes (DEGs) belong to DNA damage, cell migration, hypoxia, autophagy (MMP1, MMP9, HIF-1α, Bag-3, H2AX, HMOX1, PSRC1), and cancer progression pathways. Most importantly, top downregulated DEG MAT2A has earlier been shown to be involved in cell migration and invasion. Furthermore, using in silico analysis on the Cancer Genome Atlas (TCGA) database, this study found that MAT2A and highly co-expressed (r > 0.7) genes, TRA2B and SF1, were associated with worse Gleason score and nodal metastasis status in prostate adenocarcinoma patients (PRAD-TCGA). Immunoblotting, comet, and migration assays corroborated these findings. These results suggest that 3A.1 may be useful in increasing the anticancer efficacy of taxanes to treat aggressive PCa. SIGNIFICANCE STATEMENT: The andrographolide analogue, 19-tert-butyldiphenylsilyl-8,7-epoxy andrographolide (3A.1), showed anticancer activity against metastatic castration-resistant and neuroendocrine variant prostate cancers (mCRPC/NEPC). Additionally, 3A.1 exhibited synergistic anticancer effect in combination with standard chemotherapy drugs docetaxel and cabazitaxel in mCRPC/NEPC. Post-treatment gene expression studies revealed that heat shock proteins (Hsp70, Hsp40, Hsp27, and Hsp90) and MAT2A are important in the mechanism of 3A.1 action and drug response. Furthermore, DNA damage, cell migration, hypoxia, and autophagy were crucial pathways for the anticancer activity of 3A.1.

577O PRINCE: Interim analysis of the phase Ib study of 177Lu-PSMA-617 in combination with pembrolizumab for metastatic castration resistant prostate cancer (mCRPC)

177Lu-PSMA-617 (Lu-PSMA-617) is a radiolabelled small-molecule with established efficacy and safety in mCRPC, that delivers β radiation to tumours expressing PSMA. Pembrolizumab, an anti-programmed death 1 inhibitor, has modest single agent anti-tumour activity in mCRPC. We hypothesise that β radiation can induce tumour cell death that is potentially immunogenic, and that addition of pembrolizumab to Lu-PSMA-617 can improve responses. PRINCE aimed to evaluate the safety and efficacy of the combination of Lu-PSMA-617 and pembrolizumab. mCRPC patients (pts) with high PSMA expression without discordant FDG avid disease on paired PSMA and FDG PET/CT scans received up to 6 cycles of Lu-PSMA-617 (6-8 GBq) every 6 weeks in conjunction with 200mg of pembrolizumab every 3 weeks for up to 2 years. Co-primary endpoints were safety and 50% PSA response rate (PSA50-RR). Secondary endpoints included PSA-progression-free survival (PSA-PFS), radiographic PFS (rPFS) and overall survival (OS). 37 pts (median age 72 years; prior docetaxel 73%; prior androgen receptor targeted agent 100%) received a median of 4 cycles of Lu-PSMA-617 and 8 doses of pembrolizumab. Median follow up was 38 weeks. PSA50-RR was 73% (27/37 [95% CI: 56-86]) and 7/9 (78%) pts with RECIST measurable disease had a partial response. rPFS and PSA-PFS at 24 weeks were 64% (95% CI: 45-79) and 68% (95% CI: 50-81) respectively. Common treatment related adverse events (TRAE) (≥10%) were mainly Grade (G) 1-2 and included xerostomia (76%), fatigue (43%), diarrhoea (11%), rash (22%), nausea (24%), elevated ALT (11%), pruritus (19%), and bone pain (11%). Haematologic TRAE included G2-3 anaemia (8%), G1-2 thrombocytopenia (14%), and G1 neutropenia (3%). G3 immune related AEs affecting one pt each included mucosal pemphigus, myasthenia gravis, optic neuritis, pancreatitis, pneumonitis, nephritis, amylase elevation, type 1 diabetes, and colitis in 2 pts. 4 (11%) pts discontinued treatment due to toxicity. The combination of Lu-PSMA-617 and pembrolizumab had promising activity. Toxicities were consistent with those of single agent Lu-PSMA-617 and pembrolizumab.

Abstract 1355: A novel andrographolide analogue (3A.1) synergizes with Taxane derivatives in aggressive metastatic prostate cancers through upregulation of heatshock proteins and downregulation of MAT2A-mediated cell migration and invasion

Abstract BACKGROUND: Prostate cancer (PCa) is the 2nd leading cause of non-cutaneous cancer deaths among men in the USA with many progressing to aggressive metastatic castration resistant PCa (mCRPC; PCa unresponsive to androgen deprivation). Conventional treatment with taxanes (TX; docetaxel (DTX) or cabazitaxel (CBZ)) increases survival rates only slightly. The andrographolide analog, 19-tert-butyldiphenylsilyl-8,7-epoxy andrographolide (3A.1) has shown anticancer activity against various cancers. In this study, we investigated the effect of 3A.1 alone and in combination with DTX and CBZ against models of aggressive PCa. METHODS: Androgen receptor negative (AR-ve) mCRPC cell lines were treated with CBZ, DTX and 3A.1 as single-agent or combination over a broad concentration range, and in vitro cytotoxicity was determined. Chou-Talalay's combination index (CI) theorem was used to determine synergism and predicted dose reduction of taxanes. Post-treatment effect of single-agent and combination regimens on gene expression profile (GEP) was assessed using mRNA sequencing. Differentially expressed genes (DEGs) and molecular pathways involved in 3A.1 mechanism of action and drug synergy were identified using DESeq2, edgeR and Ingenuity pathway analysis (IPA). Protein expression of top DE genes was confirmed by immunoblotting. Cell cycle analysis, scratch/wound healing, and COMET assays were used to functionally validate the top treatment-associated genes. RESULTS: Exposure to 3A.1 alone exhibited a dose- and time-dependent antitumor activity in mCRPC. CI values of all 3A.1+ TX combinations were less than 0.5, indicating synergism. Co-treatment of 3A.1 with TX reduced the required dose of DTX by 9.5 to 18-folds (p&amp;lt;0.05), and CBZ by 3 to 14-folds (p&amp;lt;0.05). Our caspase 3/7 assay (apoptosis) results agreed with in vitro cytotoxicity data. RNAseq followed by IPA analysis identified that the top treatment-induced DEGs belong to cell migration, growth, apoptosis (MMP1, HSPB1, PSRC1), protein ubiquitination (HNRNPH2, HSPA1A/HSPA1B), and DNA repair (H2BC4, 11) pathways, along with cancer progression. Most importantly, our top downregulated DEG was MAT2A which has earlier been shown to be involved in cell migration and invasion. Our analysis using Immunoblotting, COMET, and Wound healing/Scratch (cell migration) assays corroborated with these findings. Finally, using in silico analysis on the TCGA (The Cancer Genome Atlas) database, we found that MAT2A and highly co-expressed (r&amp;gt;0.7) genes, TRA2B and SF1, were associated with worser Gleason score and nodal metastasis status in prostate adenocarcinoma patients (PRAD-TCGA). CONCLUSION: These results suggest that 3A.1 may be useful in increasing the anticancer efficacy of taxanes to treat aggressive prostate cancer. Citation Format: Taraswi Mitra Ghosh, Teeratas Kansom, Suman Mazumder, Joshua Davis, Ahmed Alnaim, Aedan Bird, P Opanasopit, Amit K. Mitra, Robert Arnold. A novel andrographolide analogue (3A.1) synergizes with Taxane derivatives in aggressive metastatic prostate cancers through upregulation of heatshock proteins and downregulation of MAT2A-mediated cell migration and invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1355.

Biomarker analysis of phase (Ph) IB trial of radium-223 (Rad) and niraparib (Nira) in patients (Pts) with metastatic castrate-resistant prostate cancer (mCRPC) (NiraRad).

5036 Background: Rad is an alpha particle emitter that causes DNA double strand breaks and has been FDA-approved for use in mCRPC pts with bone metastases. PARP-1 activity critically supports androgen receptor (AR) activity in mCRPC and potentiates AR-dependent DNA damage response pathways that promote prostate cancer cell survival. Nira is a potent and selective PARP-1/2 inhibitor that has shown single agent clinical activity in mCRPC. We previously reported the safety of targeting the PARP-1/AR axis with Nira in combination with Rad. Herein we describe the results of an exploratory biomarker analysis. Methods: The primary objective of NiraRad is to determine the optimum Ph II dose of Nira plus Rad (55 kBq/kg of body weight IV every 4 weeks (wks) x 6) in pts with and without prior chemotherapy (docetaxel). Pts were enrolled to one of three dose levels of Nira (100, 200, or 300 mg PO daily). All cohorts were combined for exploratory biomarker analysis using Nanostring PanCancer Driver and Immune Pathways panels and the nSolver Advanced analysis module was performed on blood obtained from 23 pts at baseline, cycle (C) 1 day (D) 15, and C3D15. A favorable response was defined as any PSA reduction at week 12 or treatment (tx) duration &gt; 18 wks, the median time on tx in the cohort of pts analyzed. A threshold of &gt; 2 fold (X) differentially expressed genes was used. Results: Of the 23 pts with biomarker data, 7 (30%) experienced PSA reductions and 11 (48%) received tx for &gt; 18 wks, 6 of which also had PSA reductions. Exploratory analysis revealed that the PI3K/Ras, MAPK, and transcriptional misregulation pathways were differentially regulated in pts who had favorable responses. The top downregulated gene, PAX5, which has been shown to promote prostate cancer growth, was decreased at C1D15 (2.7X, p &lt; 0.01) and C3D15 (4.8X, p &lt; 0.001) in pts with tx duration &gt; 18 wks and at baseline in pts who had PSA reductions (3.1X, p &lt; 0.05). Immune pathways analysis suggested downregulation of immunosuppressive B-cell (plasma cell) and upregulation of NK and T cell pathways in pts with tx duration &gt; 18 wks. Conclusions: Previously Nira and Rad have been shown to have acceptable tolerability in mCRPC pts. This exploratory analysis suggests potential response biomarkers that warrant further investigation. Managed by: the Prostate Cancer Clinical Trials Consortium; Funded by: Janssen Pharmaceuticals and Bayer Healthcare Pharmaceuticals, Inc. Clinical trial information: NCT03076203.

A phase 1/2 study of olaparib and radium-223 in men with metastatic castration-resistant prostate cancer (mCRPC) with bone metastases (COMRADE): Results of the phase 1 study.

e17020 Background: Radium-223 is an α-emitting radioisotope that induces DNA double-stranded breaks leading to cell death and has improved survival in mCRPC. In preclinical models, PARP inhibitors have shown efficacy as radiosensitizing agents. We designed a phase 1/2 trial to test the hypothesis that radium-223 + olaparib will demonstrate anti-tumor activity in mCRPC irrespective of homologous recombination repair deficiency (HRD) status. Methods: This is an open label, multi-center, phase 1/2 study (NCT03317392) evaluating the dosing, safety and efficacy of radium-223 + olaparib. Eligible patients (pts) had mCRPC with ≥2 bone metastases without visceral metastases or lymphadenopathy &gt; 4 cm. There was no limit on prior therapy. All pts had a baseline biopsy. The phase 1 used a 3+3 dose escalation design with fixed dose radium-223 (55 kBq/kg IV every 4 weeks x 6). Dose level 1 (DL1) was olaparib 200 mg PO BID; DL2 was olaparib 300 mg PO BID. The primary objective was to determine the recommended phase 2 dose (RP2D) and safety. The dose limiting toxicities (DLT) evaluation period was 2 cycles (1 cycle=28 days). Secondary endpoints included radiographic progression-free survival (rPFS) defined by PCWG3 criteria, PSA response (50% decline from baseline), and alkaline phosphatase response (30% decline from baseline). Results: 12 pts were enrolled on the phase 1. Median age was 68 (range 59-81) years. Median prior lines of CRPC therapies was 2 (1-5), including 3 (25%) who had received prior chemotherapy and 100% a prior novel hormone therapy. 6 pts were enrolled at DL1. 1 patient experienced a DLT outside the DLT evaluation period. 3 pts had grade (G) 3-4 treatment-related adverse events (TrAE) including G3 anemia (n=2) and G3 thrombocytopenia (n=1). No patient underwent dose reductions at DL1. 6 pts were enrolled at DL2. 1 patient experienced a DLT outside the DLT evaluation period. 2 pts had G3-4 TrAE including G3 anemia and G4 lymphocytopenia (n=1) and G3 stroke (n=1). 5 underwent dose reductions at DL2. There were no G5 events. Reason for treatment discontinuation is in the table below. After review of safety data, the safety monitoring committee deemed the RP2D of olaparib at 200 mg BID when combined with radium-223. Overall, PSA response and alkaline phosphatase response were 16.7% (n=2, 1 at DL1, 1 at DL2) and 67% (n=8, 3 at DL1, 5 at DL2), respectively. Median follow-up was 6.5 (range 2.8, 11.8) months, and 6-month rPFS was 57% (95% CI: 25%, 80%). Conclusions: We demonstrate that olaparib can be safety combined with radium-223 with RP2 dose of 200 mg BID. The phase 2 study of radium-223 +/- olaparib is accruing (target 120 pts). Outcomes by HRD status will be presented. Clinical trial information: NCT03317392. [Table: see text]

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]

A phase II single-arm study of pembrolizumab with enzalutamide in men with metastatic castration-resistant prostate cancer progressing on enzalutamide alone

BackgroundCheckpoint inhibitors can induce profound anticancer responses, but programmed cell death protein-1 (PD-1) inhibition monotherapy has shown minimal activity in prostate cancer. A published report showed that men with prostate...

First-in-human phase I study of ARV-110, an androgen receptor (AR) PROTAC degrader in patients (pts) with metastatic castrate-resistant prostate cancer (mCRPC) following enzalutamide (ENZ) and/or abiraterone (ABI).

3500 Background: Proteolysis Targeting Chimera (PROTAC) protein degraders induce selective degradation of targeted proteins by engaging the ubiquitin proteasome system. ARV-110 is an orally bioavailable PROTAC that specifically degrades AR ≥ 95% and achieves anti-tumor activity in ENZ-naïve and -resistant prostate cancer xenograft models. Methods: To define the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of ARV-110, pts with ≥ 2 prior therapies for mCRPC, including ENZ and/or ABI, received ARV-110 orally once daily. Dose escalation is per 3+3 design. Endpoints include dose limiting toxicities (DLTs), adverse events (AEs), pharmacokinetics (PK), biomarkers (e.g., AR mutation analysis), RECIST and PSA response. Results: By January 2020, 18 pts were dosed: 35 mg (N = 3), 70 mg (N = 4), 140 mg (N = 8), 280 mg (N = 3). 12 pts received both ENZ and ABI; 14 received prior chemotherapy. 1 of 18 pts experienced a DLT (280 mg) of Grade (Gr) 4 elevated AST/ALT followed by acute renal failure while taking rosuvastatin (ROS). A 2nd pt had Gr 3 AST/ALT with ROS that resolved off ROS, permitting ARV-110 retreatment. ROS plasma concentrations demonstrated significant increases concurrent with AST/ALT elevations in both pts. Subsequently, ROS was prohibited without further ≥Gr 2 AST/ALT AEs. No other related Gr 3/4 AEs were reported. ARV-110 PK was generally dose proportional and at 140 mg reached levels associated with preclinical anti-tumor activity. 15 pts were evaluable for PSA response (excludes 1 pt stopped after 1 dose for early progression and 2 pts initiated 2 weeks before cutoff, all at 140 mg). Of these, 8 pts initiated dosing at ≥140 mg. 2 pts achieved confirmed PSA declines of &gt;50%, both at 140 mg. Prior therapy in both pts included ENZ and ABI, chemotherapy, bicalutamide and radium-223 plus other regimens. 1 pt had 2 AR mutations known to confer ENZ resistance. The 2nd pt also achieved an unconfirmed RECIST partial response (confirmatory scan pending). Both responses were ongoing at data cutoff (8+ and 21+ weeks of treatment). Conclusions: To date, ARV-110 has an acceptable safety profile. Concurrent ROS is now prohibited. MTD has not yet been established; determination of RP2D continues. ARV-110 demonstrates antitumor activity in mCRPC after ENZ/ABI with 2 ongoing confirmed PSA responses, one of which was associated with tumor reduction. Updated data for this first PROTAC in clinical testing will be presented. Clinical trial information: NCT03888612 .

Phase III study of pembrolizumab (pembro) plus docetaxel and prednisone for enzalutamide (enza)- or abiraterone acetate (abi)–pretreated patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): KEYNOTE-921.

TPS262 Background: Docetaxel is an established treatment for pts with mCRPC. Pembro, a PD-1 inhibitor, showed single-agent antitumor activity in mCRPC. In the phase 1b/2 KEYNOTE-365 study (NCT02861573), docetaxel + pembro and prednisone showed activity in pts treated with abi or enza for mCRPC, warranting further evaluation. Methods: KEYNOTE-921 (NCT03834506) is a phase 3 trial to evaluate efficacy and safety of pembro + docetaxel and prednisone in chemotherapy-naive pts who progressed with enza or abi therapy for mCRPC. An estimated 1000 pts will be randomly assigned 1:1 to receive docetaxel 75 mg/m2 IV every 3 weeks (Q3W) + prednisone/prednisolone orally 5 mg twice daily (BID) and pembrolizumab 200 mg IV Q3W or docetaxel 75 mg/m2 IV Q3W + prednisone/prednisolone 5 mg orally BID + placebo IV Q3W. Treatment will be stratified by previous next-generation hormone agent (abi or enza) and metastases location (bone only, liver, other). Adults (≥18 years) with histologically or cytologically confirmed mCRPC who progressed with androgen deprivation therapy (or postbilateral orchiectomy) ≤6 months of screening, have ECOG PS 0 or 1, and have adequate organ function are eligible. Pts must have experienced either progression after ≥8 weeks (≥14 weeks for bone progression) or intolerance after ≥4 weeks of abi or enza (but not both) in a chemotherapy-naive mCRPC state. Pts will be required to provide tissue for biomarker analysis. Responses will be assessed by CT or MRI and radionuclide bone imaging per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by blinded independent central review (BICR) Q9W during the first year and Q12W thereafter. Treatment will continue with docetaxel and prednisone for up to 10 cycles and with pembro for up to 35 cycles or until disease progression, unacceptable toxicity, or consent withdrawal. Primary end points are rPFS by BICR and OS. Secondary end points are time to initiation of subsequent anticancer therapy or death, PSA response rate, time to PSA progression, ORR and DOR per PCWG3-modified RECIST v1.1 assessed by BICR, and safety. Accrual began May 2, 2019. Clinical trial information: NCT03834506.

Phase III study of pembrolizumab (pembro) plus olaparib versus enzalutamide (enza) or abiraterone acetate (abi) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) who progressed on chemotherapy: KEYLYNK-010.

TPS256 Background: Pembro, a PD-1 inhibitor, and olaparib, a PARP inhibitor, have some single-agent antitumor activity in mCRPC. The phase 1b/2 KEYNOTE-365 study (NCT02861573) showed promising activity with pembro and olaparib in pts with mCRPC unselected for homologous recombination deficiency, warranting further investigation. Methods: KEYLYNK-010 (NCT03834519) is a phase 3 trial to evaluate efficacy and safety of pembro + olaparib in molecularly unselected enza- or abi-pretreated pts with mCRPC who progressed with taxane chemotherapy. An estimated 780 pts will be randomly assigned 2:1 to receive pembro 200 mg IV every 3 wk plus olaparib 300 mg orally twice daily or abi 1000 mg orally once daily + prednisone/prednisolone 5 mg orally twice daily (enza-pretreated pts) or enza 160 mg/day orally (abi-pretreated pts). Stratification will be by prior treatment (abi/enza) and measurable disease (yes/no). Adults (≥18 y) with histologically confirmed mCRPC who progressed on androgen deprivation therapy ≤6 mo of screening, and an ECOG PS of 0 or 1 are eligible. Pts previously received either abi or enza (but not both) as well as 1 docetaxel-based regimen. Pts are required to provide tumor tissue for biomarker analysis. Responses will be assessed by CT/MRI and radionuclide bone imaging per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by blinded independent central review (BICR) every 9 wk during the first year and every 12 wk thereafter. Treatment will continue with up to 2 y of pembro (35 cycles) and olaparib or abi/enza until disease progression, unacceptable toxicity, or consent withdrawal. Primary end points are OS and rPFS. Secondary end points are time to initiation of subsequent anticancer therapy; ORR, and DOR per PCWG3-modified RECIST v1.1 by BICR; time to PSA progression; time to first symptomatic skeletal event; time to radiographic soft tissue progression; time to pain progression; and safety. Exploratory end points are identification of molecular (genomic, metabolic, or proteomic) biomarkers indicative of response. Accrual began May 2, 2019. Clinical trial information: NCT03834519.

LBA51 - CCTG IND 232: A phase II study of durvalumab with or without tremelimumab in patients with metastatic castration resistant prostate cancer (mCRPC)

BackgroundPD-L1 is overexpressed by dendritic cells of mCRPC patients (pts) progressing on androgen receptor antagonist therapy. Anti-PD-1 agents lead to infrequent but durable responses. We tested the hypothesis that dual checkpoint blockade of CTLA-4 with tremelimumab (T) and PD-L1 with durvalumab (D) enhances immune mediated activity in mCRPC. MethodsIn this multicenter randomized phase II study, mCRPC pts (measurable disease, prior abiraterone and/or enzalutamide, no more than one taxane for mCRPC) were randomized to D 1500mg IV Q4 weeks +/- 4 doses of T 75mg IV. The primary endpoint was ORR (RECIST1.1 and iRECIST) using a Simon 2-stage design. Key secondary endpoints were PSA response rate (RR) and time to progression (TTP). A treatment arm would be considered of interest if≥4 ORs (null 5% or less, alt 20% or more). Correlative testing was done for PD-L1/CD8 IHC on mandatory tumour biopsies and 74-gene panel (∼1Mb) sequencing of plasma cell-free DNA (cfDNA) both collected at baseline. Results52 pts were enrolled: median age 70 yrs (50-83), ECOG 0/1 (13/39 pts), taxane for CRPC (25 pts/48%). Table below shows details of responses. In stage 1, 13 pts were randomized to D with 0% ORR. D+T advanced to stage 2 with a total of 39 pts enrolled who received a median of 3 cycles (1-27). D+T related AEs were mainly grade 2 or less: fatigue (46%), anorexia (28%), rash (24%), diarrhea (23%), nausea/vomiting (21/18%) and thyroid dysfunction (15%). Most common grade 3/4 AEs: LFTs (8%) and diarrhea (8%). Six pts discontinued treatment due to AEs. There were no grade 5 AEs. There were six ORs (16% (95% CI: 6-32); OR median duration not reached, longest ongoing 25mos+ with PSA < 0.2ng/ml); all six remain on D, and pain improved in three of four pts. Correlation with full cfDNA panel to be presented.TableLBA51TableDurvalumabDurvalumab + TremelimumabORR0% (95% CI, 0-25%) 0/1316% (95% CI, 6-32%) 6/37PD-L1≥1%0/35/13 (38%)<1%0/91/19 (5%)TMB , 11 mts/Mb ctDNA≥0/11/2 (50%)<0/84/30 (13%)CD8 density median≥0/55/16 (31%)<0/71/14 (7%)PSA RR0% (0-25%) 0/1316% (6-32%) 6/37TTP, median (95% CI), mos2.1 (1.4, 2.6)2.6 (1.8, 2.8) ConclusionsBased on prespecified criteria, D did not show sufficient clinical activity, but further studies incorporating patient selection by biomarkers are warranted for D+T. Clinical trial identificationNCT02788773. Legal entity responsible for the studyCanadian Cancer Trials Group (CCTG). FundingAstraZeneca. DisclosureS.J. Hotte: Research grant / Funding (institution): AstraZeneca. E. Winquist: Honoraria (self): AstraZeneca. K.N. Chi: Advisory / Consultancy: AstraZeneca. S. Sridhar: Advisory / Consultancy: AstraZeneca. U. Emmenegger: Research grant / Funding (institution): AstraZeneca. C. Canil: Advisory / Consultancy: AstraZeneca. A.R. Hansen: Research grant / Funding (institution): AstraZeneca. L.K. Seymour: Research grant / Funding (institution): AstraZeneca. All other authors have declared no conflicts of interest.

895TiP - A phase I study of AMG 160, a half-life extended bispecific T cell engager (HLE BiTE) immuno-oncology therapy targeting PSMA, in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

895TiP - A phase I study of AMG 160, a half-life extended bispecific T cell engager (HLE BiTE) immuno-oncology therapy targeting PSMA, in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)