Kohli, Manish

Abstract We identified resistance mechanisms to abiraterone acetate/prednisone (AA/P) in patients with metastatic castration-resistant prostate cancer (mCRPC) in the Prostate Cancer Medically Optimized Genome-Enhanced Therapy (PROMOTE) study. We analyzed whole-exome sequencing (WES) and RNA-sequencing data from 83 patients with metastatic biopsies before (V1) and after 12 weeks of AA/P treatment (V2). Resistance was determined by time to treatment change (TTTC). At V2, 18 and 11 of 58 patients had either short-term (median 3.6 months; range 1.4–4.5) or long-term (median 29 months; range 23.5–41.7) responses, respectively. Nonresponders had low expression of TGFBR3 and increased activation of the Wnt pathway, cell cycle, upregulation of AR variants, both pre- and posttreatment, with further deletion of AR inhibitor CDK11B posttreatment. Deletion of androgen processing genes, HSD17B11, CYP19A1 were observed in nonresponders posttreatment. Genes involved in cell cycle, DNA repair, Wnt-signaling, and Aurora kinase pathways were differentially expressed between the responder and non-responder at V2. Activation of Wnt signaling in nonresponder and deactivation of MYC or its target genes in responders was detected via SCN loss, somatic mutations, and transcriptomics. Upregulation of genes in the AURKA pathway are consistent with the activation of MYC regulated genes in nonresponders. Several genes in the AKT1 axis had increased mutation rate in nonresponders. We also found evidence of resistance via PDCD1 overexpression in responders. Implications: Finally, we identified candidates drugs to reverse AA/P resistance: topoisomerase inhibitors and drugs targeting the cell cycle via the MYC/AURKA/AURKB/TOP2A and/or PI3K_AKT_MTOR pathways.

e17036 Background: Elevated serum CGA is associated with an intrinsic or treatment-related neuroendocrine differentiation in men with mCRPC. We previously demonstrated that elevated serum CGA was negatively associated with OS in men with mCRPC. Fluctuations in serum CGA during mCRPC therapy is not well known. We analyzed the impact of (i) rising serum CGA and (ii) baseline CGA/PSA ratio during treatment to identify associations with AA therapy. Methods: Between June 2013 and August 2015, 92 men with mCRPC were enrolled in a prospective trial (“PROMOTE”; NCT#01953640) with uniform serum processing performed prior to initiating abiraterone acetate/prednisone (AA/P) and serially after 12 weeks of AA/P treatments. Serum CGA was measured using a homogenous automated immunofluorescent assay. Patients (pts) receiving proton pump inhibitors or with abnormal renal function were excluded due to possible false elevations of serum CGA (n = 21 excluded). All patients underwent a composite response assessment at 12-weeks with imaging/PSA/QOL questionnaires. Kaplan Meier estimates, and Cox Regression models were used to calculate association with time-to-treatment failure (TTF) analyses, defined as time from treatment initiation to AA/P discontinuation based on disease progression (BlueSky Statistics, Chicago, IL, USA). Results: Of the 71 eligible pts, 67/71 had paired baseline and 12-week CGA and 70/71 pts had a baseline and a 12-week PSA available. The median baseline CGA was 83.0ng/ml (range: 53.0 - 127.0 ng/ml), median baseline PSA was 14.4 ng/ml (range: 6.4-40.2 ng/ml), and the median TTF was 10 months (range: 6-25 months). The median CGA after 12 weeks of AA/P was 98.0 ng/ml (58.0 -148.0 ng/ml) and we observed a CGA rise in 41/67 (61.2%) pts. An increase in chromogranin was associated with a lower risk of treatment failure (HR: 0.52, p = 0.0181). The median CGA/PSA ratio was 7.8 (2.6 -16.0). An elevated pretreatment CGA/PSA ratio above the median was associated with a lower risk of treatment failure (HR: 0.54 p value = 0.0185). Conclusions: We show that an increasing chromogranin on AA/P and an elevated baseline CGA/PSA in pts with mCRPC were associated with a favorable response to AA/P. Further studies are needed to assess if rising CGA during therapy reflects neuroendocrine differentiation and may indicate a sign of treatment effect targeting the androgen susceptible cells. Clinical trial information: NCT#01953640.

TPS5107 Background: Despite a growing number of treatment options for first line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Androgen receptor (AR) signaling inhibition increases genomic instability with double-strand DNA breaks & co-inhibition of AR & PARP induces synthetic lethality in multiple preclinical models. Homologous recombination repair (HRR) gene aberrations do not appear to be necessary for this synergy as demonstrated in a ph 3 clinical trial of abiraterone & olaparib where this combination improved radiographic progression-free survival (rPFS) in HRR-wild-type pts compared with abiraterone alone. A ph 1b trial has since shown that enzalutamide plus rucaparib has acceptable safety profile & no significant drug-drug interactions (S-DDI). Methods: CASPAR/A031902 (NCT04455750) is a ph 3 study in which 984 pts will be randomized 1:1 to enzalutamide plus rucaparib or placebo. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted-exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue available). Treatment will be continued until disease progression & crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or nonmeasurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, & no medications with S-DDI with enzalutamide/rucaparib. Hierarchical co-primary endpoints are rPFS & overall survival (OS). The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 & 21 months in control & combination arms, respectively) & 80% power to detect an HR of 0.80 in OS (median OS of 32 & 40 months, respectively). Key secondary endpoints are rPFS & OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; & differences in adverse events & quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF) & EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA-based testing for alterations in HRR genes. Enrollment to CASPAR began in July 2021 & the study is available for participation to all US-NCTN sites with a projected enrollment of 3 years. Support: U10CA180821, U10CA180882, U24CA196171; U10CA180888. Clinical trial information: NCT04455750.

PURPOSE Orteronel (TAK-700) is a nonsteroidal 17,20-lyase inhibitor suppressing androgen synthesis. We evaluated the clinical benefit of orteronel when added to androgen deprivation therapy (ADT) in patients with newly diagnosed metastatic hormone-sensitive prostate cancer. METHODS In this open-label randomized phase III study, patients with metastatic hormone-sensitive prostate cancer were randomly assigned 1:1 to ADT with orteronel (300 mg oral twice daily; experimental arm) or ADT with bicalutamide (50 mg oral once daily; control arm). The primary objective was the comparison of overall survival (OS), targeting a 33% improvement in median survival. A stratified log-rank test with a one-sided P ≤ .022 would indicate statistical significance. Secondary end points were progression-free survival (PFS), prostate-specific antigen (PSA) level at 7 months (≤ 0.2 v 0.2 to ≤ 4 v > 4 ng/mL), and adverse event profile. RESULTS Among 1,279 patients included in the analysis, 638 were randomly assigned to the ADT plus orteronel arm and 641 to the control arm. The median age was 68 years; 49% had extensive disease. After a median follow-up of 4.9 years, there was a significant improvement in PFS (median 47.6 v 23.0 months, hazard ratio 0.58; 95% CI, 0.51 to 0.67; P < .0001) and PSA response at 7 months ( P < .0001), but not in OS (median 81.1 v 70.2 months, hazard ratio 0.86; 95% CI, 0.72 to 1.02; P = .040, one-sided). More grade 3/4 adverse events occurred in the experimental versus the control arms (43% v 14%). Postprotocol life-prolonging therapy was received by 77.4% of patients in the control arm and 61.3% of patients in the orteronel arm. CONCLUSION The study did not meet the primary end point of improved OS with orteronel. The lack of correlation of PFS and PSA response with OS raises concerns over assumption of their consistent surrogacy for OS in the context of extensive postprotocol therapy in this setting.

TPS194 Background: Despite a growing number of treatment options for first line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Androgen receptor (AR) signaling inhibition increases genomic instability with double-strand DNA breaks & co-inhibition of AR & PARP induces synthetic lethality in multiple preclinical models. Homologous recombination repair (HRR) gene aberrations do not appear to be necessary for this synergy as demonstrated in a ph 2 clinical trial of abiraterone & olaparib where this combination improved radiographic progression-free survival (rPFS) in HRR-wild-type pts compared with abiraterone alone. A ph 1b trial has since shown that enzalutamide plus rucaparib has acceptable safety profile & no significant drug-drug interactions (S-DDI). Methods: CASPAR/A031902 (NCT04455750) is a ph 3 study in which 984 pts will be randomized 1:1 to enzalutamide plus rucaparib or placebo. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted-exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue available). Treatment will be continued until disease progression & crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or nonmeasurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, & no medications with S-DDI with enzalutamide/rucaparib. Hierarchical co-primary endpoints are rPFS & overall survival (OS). The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 & 21 months in control & combination arms, respectively) & 80% power to detect an HR of 0.80 in OS (median OS of 32 & 40 months, respectively). Key secondary endpoints are rPFS & OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; & differences in adverse events & quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF) & EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA-based testing for alterations in HRR genes. Enrollment to CASPAR began in July 2021 & the study is available for participation to all US-NCTN sites with a projected enrollment of 3 years. Support: U10CA180821, U10CA180882, U24CA196171; U10CA180888; Clovis Oncology; http://acknowledgments.alliancefound.org Clinical trial information: NCT04455750.

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

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

5060 Background: Tumor-associated calcium signal transducer 2 (TROP-2, TACSTD2) is a transmembrane glycoprotein that is highly expressed in many epithelial cancers. Overexpression of TROP-2 is postulated to mediate cancer cell growth, invasion, and is associated with more aggressive disease. TROP-2 has emerged as a therapeutic target for antibody-drug conjugates in clinical trials including sacituzumab govitecan and DS-1062. Here, we evaluated the expression of TROP-2 in tumor biopsies and circulating tumor cells (CTCs) in men with metastatic castration resistant prostate cancer (mCRPC) to evaluate TROP-2 as a clinically relevant target. Methods: RNA-seq data from the SU2C-PCF database and PROMOTE clinical trial (NCT#01953640) was assessed for TACSTD2 and androgen receptor (AR) splice variant ( AR_V7/AR_V9) expression. Prostate cancer ChIP-seq data was analyzed to identify binding of the AR to the TROP-2 promoter. EpCAM and TROP-2 captured CTCs were isolated from patients with mCRPC using the VERSA (Versatile Exclusion-based Rare Sample Analysis) platform and assessed for splice variant, neuroendocrine (NE), and AR-regulated gene signatures, in addition to CTC enumeration and TROP-2 protein expression. Results: TROP-2 expression was detectable in 90% of patients, in both bone and visceral metastatic biopsies (SUC2-PCF). Although TROP-2 low biopsies were infrequent (10%), 58% of these samples showed high levels of NE markers, as compared with 5% in all other patients. In the PROMOTE study, elevated TROP-2 gene expression was significantly higher in biopsies with high AR_V7 expression than in those with low (p = 0.04) or negative (p <.01) AR_V7 expression. ChIP-seq data demonstrated binding of AR at the TROP-2 promoter as well as at a potential enhancer site upstream, suggesting that TROP-2 expression can be regulated by AR activity. Splice variants and NE gene signatures were expressed in CTCs captured with both EpCAM and TROP-2, although markedly different gene expression profiles between EpCAM and TROP-2 CTCs were observed in a subset of patients with neuroendocrine prostate cancer. Detection of AR_V7 from TROP-2 CTCs corresponded to shorter overall survival in 20 patients with mCRPC. TROP-2 protein expression was identified on EpCAM captured CTCs, although patients exhibited a wide degree of both intra- and inter-patient heterogeneity. Conclusions: Our findings demonstrate that TROP-2 is highly expressed in mCRPC, and is reduced in a subset of patient tumors expressing neuroendocrine markers. In the PROMOTE clinical trial with abiraterone acetate, TROP-2 AR variant expression correlated with increased TROP-2 expression. Binding of the AR to the TROP-2 promoter and potential enhancer was observed in prostate cancer cell lines and biopsies. These results indicate TROP-2 is a high value a biomarker and therapeutic target mCRPC.

5001 Background: Tak is an oral selective nonsteroidal 17, 20-lyase inhibitor that blocks the synthesis of gonadal and adrenal androgens. We evaluated the clinical benefit of Tak with ADT in pts with newly diagnosed mHSPC. Methods: Pts with mHSPC with a Zubrod performance status (PS) of 0-2 and a PSA of ≥ 2 ng/ml were randomized 1:1 to ADT+Tak (300 mg twice daily) or ADT+Bic (50 mg daily). Stratification factors included PS (0-1 vs ≥2), extent of disease (minimal vs extensive), and receipt of ADT prior to registration (yes vs no). The primary endpoint was overall survival (OS). Secondary endpoints were progression free survival (PFS; based on PSA, imaging or clinical progression), PSA at 7 months (≤0.2 vs 0.2 < PSA; ≤-4 vs. > 4 ng/ml) and adverse event (AE) profile. With 2.75 yrs to accrue 1,186 eligible pts and 3 additional yrs of follow-up, we would have 90% power to determine a 33% improvement in OS from 54 to 72 mos (1-sided α = 0.025). A final analysis was pre-specified after 523 deaths using a 1-sided α = 0.022 to account for interim analyses. Results: Between 3/2013 and 7/2017, 1,313 pts were randomized and 1,279 were included in the intention-to-treat (ITT) analysis (32 pts were ineligible and 2 pts withdrew consent). Median age was 68 yrs and 10% of subjects were Black. Median PSA was 30 ng/mL (range 2-6710) and 49% of pts had extensive disease. After a median follow-up of 4.9 yrs, PFS and PSA response were significantly improved with Tak over Bic but no significant improvement in OS was observed (Table). More grade 3/4 AEs occurred in Tak vs. Bic arms (43% vs. 14%), and included hypertension (20% vs. 5%) and fatigue (5% vs. 2%). Five pts in Tak and 1 pt in the Bic arm had grade 5 AE. Conclusions: Despite clinically meaningful improvement in various outcome measures with Tak+ADT over Bic+ADT in this representative population of mHSPC, the improvement in OS did not meet the pre-specified criteria for statistical significance. The median OS of 70 mos in the control arm (standard ADT) was higher than that reported in contemporary phase 3 trials in this setting, and 16 mos higher than originally estimated. This trial sets a new landmark for survival estimates when pts with mHSPC have access to multiple approved subsequent life-prolonging therapies. Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819, U10CA180820; U10CA180821; and in part by Millennium Pharmaceuticals, Inc. (Takeda Pharmaceutical Company LTD) Clinical trial information: NCT01809691. [Table: see text]

PURPOSE Multiple large clinical trials have investigated adjuvant tyrosine kinase inhibitors (TKIs) to reduce the risk of cancer recurrence and progression to metastasis in high-risk renal cell carcinoma. We sought to maintain living and interactive evidence on this topic, until a high level of certainty is reached for key clinical outcomes such that further updates become unnecessary and unlikely to change clinical practice. METHODS We created a living interactive evidence synthesis platform to maintain a continuously updated meta-analysis on TKI monotherapy in adjuvant renal cell carcinoma. We implemented an automated search strategy with weekly updates to identify randomized phase 2 and 3 clinical trials. Study selection, appraisal, and data extraction were done in duplicate. Cumulative meta-analysis was performed using Analyzer Module in Living Interactive Evidence platform. For each outcome (overall survival [OS], disease-free survival [DFS], and all-cause and treatment-related adverse events), we assessed certainty of evidence using GRADE approach and conducted trial sequential analysis. RESULTS This final update includes five randomized trials including recently updated data from PROTECT trial. Meta-analysis shows that adjuvant TKI monotherapy offers no benefit in OS (hazard ratio, 1.01; 95% CI, 0.91 to 1.12, high certainty) or DFS (hazard ratio, 0.92; 95% CI, 0.86 to 1.00, high certainty) and significantly increases adverse event risk. Lack of benefit was consistent across subgroups including highest-risk patients (test for subgroup differences: P = .32). Optimal information size criteria were met, and there was high certainty of evidence for lack of DFS and OS benefit for adjuvant TKIs. CONCLUSION There is no guidance on when to stop maintaining a living review. In this example, we used trial sequential analysis and high certainty of evidence (future clinical trials unlikely to change current conclusions) as a benchmark to conclude a living review in view of convincing evidence.