TARGET: A Randomized, Noninferiority Trial of a Pretest, Patient-Driven Genetic Education Webtool Versus Genetic Counseling for Prostate Cancer Germline Testing

PURPOSE

Germline genetic testing (GT) is important for prostate cancer (PCA) management, clinical trial eligibility, and hereditary cancer risk. However, GT is underutilized and there is a shortage of genetic counselors. To address these gaps, a patient-driven, pretest genetic education webtool was designed and studied compared with traditional genetic counseling (GC) to inform strategies for expanding access to genetic services.

METHODS

Technology-enhanced acceleration of germline evaluation for therapy (TARGET) was a multicenter, noninferiority, randomized trial (ClinicalTrials.gov identifier: NCT04447703) comparing a nine-module patient-driven genetic education webtool versus pretest GC. Participants completed surveys measuring decisional conflict, satisfaction, and attitudes toward GT at baseline, after pretest education/counseling, and after GT result disclosure. The primary end point was noninferiority in reducing decisional conflict between webtool and GC using the validated Decisional Conflict Scale. Mixed-effects regression modeling was used to compare decisional conflict between groups. Participants opting for GT received a 51-gene panel, with results delivered to participants and their providers.

RESULTS

The analytic data set includes primary outcome data from 315 participants (GC [n = 162] and webtool [n = 153]). Mean difference in decisional conflict score changes between groups was -0.04 (one-sided 95% CI, -∞ to 2.54; P = .01), suggesting the patient-driven webtool was noninferior to GC. Overall, 145 (89.5%) GC and 120 (78.4%) in the webtool arm underwent GT, with pathogenic variants in 15.8% (8.7% in PCA genes). Satisfaction did not differ significantly between arms; knowledge of cancer genetics was higher but attitudes toward GT were less favorable in the webtool arm.

CONCLUSION

The results of the TARGET study support the use of patient-driven digital webtools for expanding access to pretest genetic education for PCA GT. Further studies to optimize patient experience and evaluate them in diverse patient populations are warranted.

Master Transcription Factor Reprogramming Unleashes Selective Translation Promoting Castration Resistance and Immune Evasion in Lethal Prostate Cancer

Signaling rewiring allows tumors to survive therapy. Here we show that the decrease of the master regulator microphthalmia transcription factor (MITF) in lethal prostate cancer unleashes eukaryotic initiation factor 3B (eIF3B)-dependent translation reprogramming of key mRNAs conferring resistance to androgen deprivation therapy (ADT) and promoting immune evasion. Mechanistically, MITF represses through direct promoter binding eIF3B, which in turn regulates the translation of specific mRNAs. Genome-wide eIF3B enhanced cross-linking immunoprecipitation sequencing (eCLIP-seq) showed specialized binding to a UC-rich motif present in subsets of 5' untranslated regions. Indeed, translation of the androgen receptor and major histocompatibility complex I (MHC-I) through this motif is sensitive to eIF3B amount. Notably, pharmacologic targeting of eIF3B-dependent translation in preclinical models sensitizes prostate cancer to ADT and anti-PD-1 therapy. These findings uncover a hidden connection between transcriptional and translational rewiring promoting therapy-refractory lethal prostate cancer and provide a druggable mechanism that may transcend into effective combined therapeutic strategies.

SIGNIFICANCE

Our study shows that specialized eIF3B-dependent translation of specific mRNAs released upon downregulation of the master transcription factor MITF confers castration resistance and immune evasion in lethal prostate cancer. Pharmacologic targeting of this mechanism delays castration resistance and increases immune-checkpoint efficacy. This article is featured in Selected Articles from This Issue, p. 2489.

External Validation of a Prognostic Model of Overall Survival in Men With Chemotherapy-Naïve Metastatic Castration-Resistant Prostate Cancer

PURPOSE

We have previously developed and externally validated a prognostic model of overall survival (OS) in men with metastatic, castration-resistant prostate cancer (mCRPC) treated with docetaxel. We sought to externally validate this model in a broader group of men with docetaxel-naïve mCRPC and in specific subgroups (White, Black, Asian patients, different age groups, and specific treatments) and to classify patients into validated two and three prognostic risk groupings on the basis of the model.

METHODS

Data from 8,083 docetaxel-naïve mCRPC men randomly assigned on seven phase III trials were used to validate the prognostic model of OS. We assessed the predictive performance of the model by computing the time-dependent area under the receiver operating characteristic curve (tAUC) and validated the two-risk (low and high) and three-risk prognostic groups (low, intermediate, and high).

RESULTS

The tAUC was 0.74 (95% CI, 0.73 to 0.75), and when adjusting for the first-line androgen receptor (AR) inhibitor trial status, the tAUC was 0.75 (95% CI, 0.74 to 0.76). Similar results were observed by the different racial, age, and treatment subgroups. In patients enrolled on first-line AR inhibitor trials, the median OS (months) in the low-, intermediate-, and high-prognostic risk groups were 43.3 (95% CI, 40.7 to 45.8), 27.7 (95% CI, 25.8 to 31.3), and 15.4 (95% CI, 14.0 to 17.9), respectively. Compared with the low-risk prognostic group, the hazard ratios for the high- and intermediate-risk groups were 4.3 (95% CI, 3.6 to 5.1; P < .0001) and 1.9 (95% CI, 1.7 to 2.1; P < .0001).

CONCLUSION

This prognostic model for OS in docetaxel-naïve men with mCRPC has been validated using data from seven trials and yields similar results overall and across race, age, and different treatment classes. The prognostic risk groups are robust and can be used to identify groups of patients for enrichment designs and for stratification in randomized clinical trials.

A phase 1/2 study of REGN4336, a PSMAxCD3 bispecific antibody, alone and in combination with cemiplimab in patients with metastatic castration-resistant prostate cancer

TPS284

Background: Prostate cancer is the leading cause of new cancer diagnoses and the second most common cause of cancer-related death in American men. Prognosis is especially poor for men with metastatic castration resistant prostate cancer (mCRPC). Prostate-specific membrane antigen (PSMA) is highly expressed on malignant prostate tissue but shows limited expression on normal tissue. As such, PSMA is an excellent research target for treatment of mCRPC. REGN4336 is a PSMAxCD3 bispecific antibody designed to facilitate T-cell–mediated killing of PSMA-expressing tumor cells. In preclinical models, REGN4336 demonstrated strong PSMA-dependent antitumor activity that was dose-dependent. Preclinical data also support clinical research into the combination of REGN4336 with cemiplimab (anti–programmed cell death-1) for treating mCRPC. Methods: This is an open-label, Phase 1/2, first-in-human, multicenter dose-escalation study with dose expansion evaluating safety, tolerability, pharmacokinetics (PK), and antitumor activity of REGN4336 administered subcutaneously alone and in combination with intravenous cemiplimab in patients with mCRPC (NCT05125016). Patients must have received at least two prior lines of systemic therapy approved for metastatic and/or castration-resistant disease including a second-generation anti-androgen therapy. In Module 1, REGN4336 as monotherapy is administered weekly but may be extended to once every 3 weeks following identification of the minimal pharmacologically active dose. In Module 2, REGN4336 will be administered in combination with cemiplimab (350 mg) once every 3 weeks after a 4-week REGN4336 monotherapy lead-in cycle. Study therapies are administered until disease progression, intolerable adverse events, withdrawal of consent, or a study withdrawal criterion is met. The primary objectives in dose escalation are to evaluate the safety, tolerability, PK, and recommended phase 2 dosing regimen (RP2DR) of REGN4336 alone and in-combination with cemiplimab. Expansion cohort(s) will be enrolled once RP2DRs have been determined. During the expansion phase, the primary objective is to assess clinical activity, as measured by objective response rate with REGN4336 alone or in combination with cemiplimab per modified Prostate Cancer Working Group 3 criteria. At selected sites, PSMA positron emission tomography/computed tomography scans will be performed at predefined timepoints on study. This study is currently open to enrollment. Clinical trial information: NCT03088540 .

Cabozantinib in combination with atezolizumab in non-clear cell renal cell carcinoma: Extended follow-up results of cohort 10 of the COSMIC-021 study

684

Background: In the COSMIC-021 phase 1b study (NCT03170960) evaluating cabozantinib plus atezolizumab in advanced solid tumors, this combination therapy demonstrated encouraging clinical activity in patients with advanced non-clear cell renal cell carcinoma (nccRCC) with a median follow-up of 13 mo (Pal. JCO 2021). Results after extended follow-up in nccRCC are presented. Methods: Patients with advanced nccRCC and ECOG PS 0/1 who had ≤1 prior VEGFR-targeting tyrosine kinase inhibitor (TKI) were eligible. Prior treatment with TKIs targeting MET or immune checkpoint inhibitors was not allowed. Patients received cabozantinib 40 mg PO QD plus atezolizumab 1200 mg IV Q3W until unacceptable toxicity or progression; dose reductions of cabozantinib (40 mg QD to 20 mg QD, then to 20 mg QOD) were permitted to manage adverse events. The primary endpoint was objective response rate (ORR) per RECIST v1.1 by the investigator; other endpoints included safety, duration of response (DOR), PFS, and OS. Results: The study enrolled 32 patients with nccRCC (2 from dose escalation phase, and 30 from expansion phase of the study): median age, 62 y; male, 81%; ECOG PS 0/1, 75%/25%; histology, papillary/chromophobe/clear cell/other, 47%/28%/3%/22%; sarcomatoid feature, 13%; IMDC risk favorable/intermediate/poor, 50%/41%/9%; ≥3 tumor sites, 56%; tumor sites, lung/kidney/bone/liver, 50%/25%/16%/16%; prior nephrectomy, 63%; prior VEGFR TKI, 22%; 0/1 lines of prior therapy (locally advanced/metastatic setting), 81%/19%. As of July 21, 2022, median follow-up was 37.2 mo (range 32.1–58.5) with 5 (16%) patients remaining on study treatment. ORR by investigator was 31% (all PRs) and disease control rate was 94% (Table); median DOR was 8.1 mo. Median PFS was 9.3 mo (95% CI 5.5–12.3), and median OS was not reached (95% CI 23.0–NE). PFS and OS estimates at 12 mo were 34% and 84%, respectively; 24-mo estimates were 6% and 70%. Treatment-related AEs occurred in 97% (grade 3/4, 53%); the most common AEs included diarrhea (69%), palmar-plantar erythrodysesthesia (50%), fatigue (44%), dysgeusia (41%), hypertension (31%) and nausea (31%). One grade 5 treatment-related AE of pulmonary hemorrhage occurred. Treatment-related AEs leading to discontinuation of both study treatments occurred in 13% of patients. Conclusions: Extended 3-year follow-up reinforces the encouraging clinical activity of cabozantinib plus atezolizumab in advanced nccRCC with a manageable safety profile. Clinical trial information: NCT03170960 . [Table: see text]

Preliminary results from a phase 1/2 study of co-stimulatory bispecific PSMAxCD28 antibody REGN5678 in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

154

Background: Pts with mCRPC have a poor prognosis with limited treatment options, including minimal response to immunotherapies. REGN5678 is a first-in-class, full-length anti-PSMAxCD28 bispecific costimulatory antibody designed to target prostate cancer cells and enhance T-cell activation. We report preliminary results from the dose escalation part of a first-in-human, open-label, Phase 1/2 study (NCT03972657) examining REGN5678 in combination with cemiplimab, a PD-1 blocking antibody. Methods: Pts with mCRPC had received ≥2 lines of systemic therapy in the metastatic and/or castration-resistant setting, including ≥1 second-generation anti-androgen. Pts received REGN5678 weekly at dose levels [DL] 0.1–300 mg, initially as monotherapy for 3 weeks, followed by combination with cemiplimab (350 mg Q3W) until progression or toxicity. Primary objectives are safety, tolerability, and pharmacokinetics. Preliminary efficacy measurements include decline in prostate-specific antigen (PSA) from the start of combination treatment and radiographic response from baseline. Results: At the data cutoff (DCO; July 27 2022), 35 pts had been treated. Treatment-emergent adverse events (TEAEs) ≥Grade (G)3 occurred in 54% (19/35) of pts. Cytokine release syndrome occurred in 6 pts (all G1) and there were 2 dose-limiting toxicities (both G3): pain (at 1 mg) and Guillain-Barré syndrome (at 300 mg). 4 pts (11%) experienced a ≥G3 immune-mediated adverse event (imAE; at DLs 30–300 mg). REGN5678 exposure was non-linear over the tested DLs (more than dose proportional). There were minimal signs of efficacy at lower DLs (REGN5678 0.1–10 mg), with only 1/16 pts showing a PSA decline (of 21%). More PSA declines occurred at higher DLs: 1/4 pts at 30 mg (a PSA decline of 100%), 3/8 at 100 mg (>99%, 44%, 22%), and 3/4 at 300 mg (>99%, 99%, 82%). Notably, all ≥G3 imAEs occurred in pts with PSA declines. Among pts with measurable disease and ≥1 on-treatment scan, radiographic response per RECIST 1.1 occurred in 1/3 pts at 30 mg (complete response), 1/4 at 100 mg (unconfirmed partial response [PR]), and 1/1 at 300 mg (PR confirmed after DCO). Conclusions: Preliminary data on REGN5678 plus cemiplimab in pts with mCRPC provide first evidence of clinical activity of a CD28 co-stimulatory bispecific antibody in solid tumors. Clinical activity was observed at DLs 30–300 mg. ≥G3 imAEs occurred in pts with PSA declines, suggesting a possible association. The study is ongoing to determine the maximum tolerated and recommended Phase 2 doses. Clinical trial information: NCT03972657 . [Table: see text]

HCRN GU14-188: Phase Ib/II study of neoadjuvant pembrolizumab and chemotherapy for T2-4aN0M0 urothelial cancer

448

Background: Immune checkpoint inhibition (ICI) is a standard of care therapy in metastatic urothelial carcinoma (mUC) but its role in the muscle-invasive setting remains unclear. Prior neoadjuvant ICI studies have demonstrated promising antitumor activity. We report results of a multi-institutional phase Ib/II two-stage study investigating chemo-immunotherapy in patients (pts) with cisplatin eligible or ineligible muscle-invasive UC (MIUC) (NCT02365766). Methods: Eligible pts were surgical candidates with clinical stage T2-4aN0M0 UC. Pts were enrolled on either the cisplatin eligible (CE) or cisplatin ineligible (CI) cohort. Both cohorts received 5 doses neoadjuvant pembrolizumab 200 mg every 3 weeks. CE chemo comprised four 21-day cycles of gemcitabine 1000 mg/m2 day (d) 1,8 and cisplatin 70 mg/m2 d 1 or 35 mg/m2 d 1,8. CI chemo comprised three 28-day cycles of gemcitabine 1000 mg/m2 d 1,8,15. Chemo-immunotherapy was followed by definitive surgery (radical cystectomy or nephroureterectomy). Primary endpoint was investigator assessed pathologic muscle-invasive response rate (PaIR, ≤ypT1N0) assessed at definitive surgery. Null hypothesis was PaIR rates of 23% (CE) and 18% (CI) for type I error rate 4% and power 86%. Secondary endpoints were rate of definitive surgery, ypT0 rate, 18 month (mo) relapse free survival (RFS), and 36 mo overall survival (OS). Results: 82 pts (42 CE, 40 CI) enrolled. 1 CI pt withdrew before cycle 1. 88.1% (CE) and 87.2% (CI) pts received definitive surgery, leaving 37 CE and 34 CI pts evaluable for the primary endpoint. 81% CE pts completed all 4 chemo cycles (median 4), and 92% CI pts completed all 3 chemo cycles (median 3). Median pembrolizumab treatments was 5 (range 1-6) in both cohorts. Median follow-up was 54.8 mos (CE) and 29.2 mos (CI). Median age was 64 (CE) and 73 (CI) and stage > T2 at diagnosis was 42.9% (CE) and 60% (CI). PaIR rate for evaluable CE pts was 54% (95% CI 38-69) with 41% pts (95% CI 27-57) down staged to ypT0. 18 mo RFS was 82% (95% CI 66-91) and 36 mo OS was 78.9% (95% CI 65-90). PaIR rate for evaluable CI pts was 53% (95% CI 37-69) with 41% pts (95% CI 26-58) downstaged to ypT0. 18 mo RFS was 65.1% (95% CI 48-78) and 36 mo OS was 65.7% (95% CI 47-79). Most common ≥ grade 3 toxicities were anemia (28.3%), hypertension (28.3%), and neutropenia (22.2%), with cytopenias more common in CE than CI pts. One death from post-operative sepsis occurred in cohort CE. Immune related adverse events (irAEs) ≥ grade 3 include elevated liver enzymes (3.7%), rash (2.5%), pneumonitis (2.5%), and colitis (2.5%). Conclusions: Neoadjuvant chemo-immunotherapy demonstrated significant down staging in CE and CI MIUC pts prior to definitive surgery, meeting the primary endpoint. Survival correlated with pathologic response. Further phase III studies will be necessary to confirm the efficacy and safety of these regimens. Ongoing analysis of biomarkers of response is underway. Clinical trial information: NCT02365766 .

Bispecific PSMA antibodies and CAR-T in metastatic castration-resistant prostate cancer

Prostate cancer is the most common cancer among men and the second leading cause of cancer-related deaths in men in the United States. The treatment paradigm for prostate cancer has evolved with the emergence of a variety of novel therapies which have improved survival; however, treatment-related toxicities are abundant and durable responses remain rare. Immune checkpoint inhibitors have shown modest activity in a small subset of patients with prostate cancer and have not had an impact on most men with advanced disease. The discovery of prostate-specific membrane antigen (PSMA) and the understanding of its specificity to prostate cancer has identified it as an ideal tumor-associated antigen and has revived the enthusiasm for immunotherapeutics in prostate cancer. T-cell immunotherapy in the form of bispecific T-cell engagers (BiTEs) and chimeric antigen receptor (CAR) T-cell therapy have shown exceptional success in treating various hematologic malignancies, and are now being tested in patients with prostate cancer with drug design centered on various target ligands including not just PSMA, but others as well including six-transmembrane epithelial antigen of the prostate 1 (STEAP1) and prostate stem cell antigen (PSCA). This summative review will focus on the data surrounding PSMA-targeting T-cell therapies. Early clinical studies with both classes of T-cell redirecting therapies have demonstrated antitumor activity; however, there are multiple challenges with this class of agents, including dose-limiting toxicity, 'on-target, off-tumor' immune-related toxicity, and difficulty in maintaining sustained immune responses within a complex and overtly immunosuppressive tumor microenvironment. Reflecting on experiences from recent trials has been key toward understanding mechanisms of immune escape and limitations in developing these drugs in prostate cancer. Newer generation BiTE and CAR T-cell constructs, either alone or as part of combination therapy, are currently under investigation with modifications in drug design to overcome these barriers. Ongoing innovation in drug development will likely foster successful implementation of T-cell immunotherapy bringing transformational change to the treatment of prostate cancer.

Outcomes Following Abiraterone versus Enzalutamide for Prostate Cancer: A Scoping Review

Abiraterone acetate (AA) and enzalutamide (ENZ) are commonly used for metastatic prostate cancer. It is unclear how their outcomes and toxicities vary with patient-specific factors because clinical trials typically exclude patients with significant comorbidities. This study aims to fill this knowledge gap and facilitate informed treatment decision making. A registered protocol utilizing PRISMA scoping review methodology was utilized to identify real-world studies. Of 433 non-duplicated publications, 23 were selected by three independent reviewers. ENZ offered a faster and more frequent biochemical response (30-50% vs. 70-75%), slowed progression (HR 0.66; 95% CI 0.50-0.88), and improved overall survival versus AA. ENZ was associated with more fatigue and neurological adverse effects. Conversely, AA increased risk of cardiovascular- (HR 1.82; 95% CI 1.09-3.05) and heart failure-related (HR 2.88; 95% CI 1.09-7.63) hospitalizations. Ultimately, AA was associated with increased length of hospital stay, emergency department visits, and hospitalizations (HR 1.26; 95% CI 1.04-1.53). Accordingly, total costs were higher for AA, although pharmacy costs alone were higher for ENZ. Existing data suggest that AA and ENZ have important differences in outcomes including toxicities, response, disease progression, and survival. Additionally, adherence, healthcare utilization, and costs differ. Further investigation is warranted to inform treatment decisions which optimize patient outcomes.

Abstract 4133: High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients

In the phase 2 GALAHAD study (NCT02854436), the PARP inhibitor (PARPi) niraparib, was evaluated in heavily pre-treated patients with mCRPC and DNA-repair gene defects (DRD) who progressed after androgen-receptor (AR) targeted therapy and taxane-based chemotherapy. The results showed that objective response rate (ORR) was 34.2% for patients with measurable disease having biallelic BRCA1/2 alterations (n=76). The development of BRCA reversion mutations, a type of secondary mutation that restores protein function, has been proposed as a key resistance mechanism to PARP inhibition. We aimed to evaluate the relationship between reversion mutations and treatment response in BRCA1/2 altered patients treated with niraparib in the GALAHAD study.

Thirty-three patients with biallelic BRCA alterations (excluding patients with homozygous deletions) had donated an end-of-treatment (EOT) ctDNA sample. We performed sequencing to detect reversion mutations using the Resolution Bioscience ctDx-HRD assay. Mutation patterns at baseline included splice site, nonsense, missense, and frameshift mutations, with the latter being the most common (24/33; 73%). No reversions were detected at baseline and the baseline BRCA alterations were detected at EOT for every patient. Most BRCA patients (28/33; 85%) had at least 1 reversion mutation (range: 1-38 different BRCA alterations) at EOT. Of the 28 patients with reversions, 5 were classified as low reversions: 3 patients had only one reversion mutation, 1 patient had 2 reversions at low allele frequency and 1 patient had 4 reversions at low allele frequency. Patients with reversion mutations showed better composite response (defined as ORR by RECIST 1.1, or CTC conversion to &lt;5/7.5 mL blood, or ≥50% decline in prostate specific antigen) (74.2% vs 25.8%, p=0.01) and longer duration on treatment (median 6.9 vs 3.7 mo, p&lt;0.05) compared to those without or low reversions. Additionally, patients with reversions trended to have longer median radiographic progression-free survival compared to those without or low reversions (8.1 vs 5.5 mo, p=0.12). In conclusion, the high prevalence of patients with BRCA reversion mutations and the displayed longer benefit from niraparib underscores the dependence of these tumors on BRCA mutation as an oncogenic driver and reversion mutations as a marker of secondary resistance to niraparib treatment.

Citation Format: Karen Urtishak, Gerhardt Attard, Tokuwa Kanno, Shibu Thomas, Gary E. Mason, Byron Espina, Eugene Zhu, Natalie Hutnick, Mary Guckert, Adam del Corral, Mark Li, Angela Lopez-Gitlitz, Kim Chi, William Kevin Kelly, Evan Y. Yu, Karim Fizazi, Matthew Smith. High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4133.

A phase 1/2 study of REGN4336, a PSMAxCD3 bispecific antibody, alone and in combination with cemiplimab in patients with metastatic castration-resistant prostate cancer

TPS5105

Background: Prostate cancer is the leading cause of new cancer diagnoses and the second most common cause of cancer-related death in American men. Prognosis is especially poor for men with metastatic castration resistant prostate cancer (mCRPC). Prostate-specific membrane antigen (PSMA) is highly expressed on malignant prostate tissue but shows limited expression on normal tissue. As such, PSMA is an excellent research target for treatment of mCRPC. REGN4336 is a PSMAxCD3 bispecific antibody designed to facilitate T-cell–mediated killing of PSMA-expressing tumor cells. In preclinical models, REGN4336 demonstrated strong PSMA-dependent antitumor activity that was dose-dependent. Preclinical data also support clinical research into the combination of REGN4336 with cemiplimab (anti–programmed cell death-1) for treating mCRPC. Methods: This is an open-label, Phase 1/2, first-in-human, multicenter dose-escalation study with dose expansion evaluating safety, tolerability, pharmacokinetics (PK), and antitumor activity of REGN4336 administered subcutaneously alone and in combination with intravenous cemiplimab in patients with mCRPC (NCT05125016). Patients must have received at least two prior lines of systemic therapy approved for metastatic and/or castration-resistant disease including a second-generation anti-androgen therapy. In this study, REGN4336 as monotherapy is administered weekly but may be extended to once every 3 weeks following identification of the minimal pharmacologically active dose. REGN4336 in combination with cemiplimab (350 mg) will be administered once every 3 weeks after a 4-week REGN4336 monotherapy lead-in cycle. Study therapies are administered until disease progression, intolerable adverse events, withdrawal of consent, or study withdrawal criterion is met. The primary objectives in dose escalation are to evaluate the safety, tolerability, PK, and recommended phase 2 dosing regimen (RP2DR) of REGN4336 alone and in-combination with cemiplimab. Expansion cohort(s) will be enrolled once RP2DRs have been determined. During the expansion phase, the primary objective is to assess clinical activity, as measured by objective response rate with REGN4336 alone or in combination with cemiplimab per modified Prostate Cancer Working Group 3 criteria. At selected sites, PSMA positron emission tomography/computed tomography scans will be performed at predefined timepoints on study. This study is currently open to enrollment. Clinical trial information: NCT03088540.

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

TPS5101

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

A randomized phase Ib/II study of intermittent androgen deprivation therapy plus nivolumab with or without interleukin-8 blockade in men with hormone-sensitive prostate cancer (MAGIC-8)

5082

Background: Immunotherapy has limited efficacy in castration-resistant prostate cancer. Androgen deprivation therapy (ADT) has significant immunomodulatory effects and initially induces a complex immune infiltrate before castration-resistance develops. However, ADT also recruits immunosuppressive myeloid cells to the tumor microenvironment by increasing interleukin-8 (IL-8). We conducted a phase Ib/II clinical trial of immunotherapy plus ADT in men with recurrent castration-sensitive prostate cancer (CSPC). We hypothesized that anti-PD-1 (nivolumab) +/- anti-IL-8 (BMS-986253) given at the time of castration could induce anti-tumor immune responses and decrease disease progression. Methods: MAGIC-8 was a multicenter, phase Ib/II study evaluating nivolumab +/- BMS-986253 combined with a short course of degarelix acetate in patients with recurrent CSPC and rapid PSA doubling time (≤ 12 mos). In the Phase Ib portion, patients were treated with nivolumab (480mg Q4W) for 8 wks followed by nivolumab plus degarelix for an additional 16 wks. In the phase II portion, patients were randomized 1:2 to nivolumab + degarelix (Arm A) versus nivolumab + BMS-986253 (2400mg Q2W) + degarelix (Arm B). The primary endpoints were PSA recurrence at 10 mos following randomization and safety. Key secondary endpoints included biochemical recurrence-free survival (bPFS), time to recovery of testosterone (> 150ng/dl), and bPFS after recovery of testosterone. Results: Between October 16, 2019 and March 9, 2021, 59 patients were enrolled. The first 15 patients were treated on Arm A followed by 1:2 randomization to Arm A (N = 15) versus Arm B (N = 29). Median follow up was 11.6 mos at the data cutoff (1/24/22). Patients treated on Arm A had a significantly lower rate of PSA relapse (17.39%) at 10 mos compared to historical controls (p = < 0.001), including a subgroup of patients (6.67%) with recovery of testosterone and no PSA relapse at > 2 years of follow up. Median time-to-recovery of testosterone was 12.7 mos, median bPFS was 14.0 mos and median bPFS after recovery of testosterone was 5.5 mos. In Arm B, there was no difference in PSA relapse at 10 mos (35%, p = 0.09), median time-to-recovery of testosterone, median bPFS and median bPFS after recovery of testosterone compared to historical controls. Treatment in both arms was well tolerated with a lower rate of grade 3-4 treatment-related adverse events in Arm B compared to Arm A (3.5% vs 12.9%). Conclusions: A short course of ADT plus nivolumab may decrease the rate of PSA relapse and lead to durable long-term responses after recovery of testosterone in a subset of patients. These data support further evaluation of combining nivolumab with ADT in CSPC. Although the addition of BMS-986253 did not improve rate of PSA relapse, we observed significantly less toxicity with the addition of IL-8 inhibition. Clinical trial information: NCT03689699.

Guidelines on Germline Testing for Urologic Tumor Syndromes

In the expanding precision medicine landscape, along with improvements in and the availability of testing, the use of genetics in the evaluation and treatment of patients has increased significantly. Multiple urologic cancers in different organ systems associated with an inherited gene mutation have been described. As these mutations can impact screening and treatment decisions for patients and their families, it is important for providers to be familiar with the current guidelines for germline testing. Here we summarize the current guidelines regarding germline testing for patients with suspected urologic tumor syndromes. PATIENT SUMMARY: Several cancers of the genitourinary tract can be associated with inherited genetic mutations. Knowledge of when to test for these mutations has implications for both treatment and screening of patients and their family members at risk of genitourinary cancers.

Prevalence of Fanconi anemia gene mutations among men undergoing multigene germline testing for prostate cancer: Interim results from the EMPOWeR study

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Background: Germline testing for prostate cancer (PCA) is now central to treatment, screening, and hereditary cancer management. The Fanconi anemia (FA) pathway is a key DNA repair pathway involved in PCA biology and treatment. Prevalence of FA genes BRCA2, PALB2, and BRIP1 is well-described; however, multiple other FA genes are not routinely tested, with limited prevalence data. Here we report mutation prevalence of a spectrum of FA genes among men undergoing PCA multigene testing on the Evaluation and Management for Prostate Oncology, Wellness, and Risk (EMPOWeR) study. Methods: Eligibility includes any male with PCA or at-risk for PCA. Multigene testing includes 51 genes; FA pathway genes include BRCA2, PALB2, BRIP1, FANCA, FANCB, FANCC, FANCD2, FANCE, FANCF, FANCG, FANCI, FANCL, and FANCM. Multiple additional cancer risk genes were tested. Fisher’s exact tests were conducted to compare the prevalence of FA gene mutations between participants in the EMPOWeR study vs population prevalence reported in the literature. Statistical significance level of all tests was set a priori to 0.05. Results: The current cohort includes 235 participants. Characteristics are White (83.3%), Black (13.7%), PCA diagnosis (83.4%), mean age of PCA diagnosis 61.7 + 7.69 years, Gleason score >=7 (66.2%), and T3 or higher (29.4%). Genetic results were available for 179 participants. Overall, 11.1% of participants (n=20) had a pathogenic/likely pathogenic mutation identified. Among mutation carriers, 45% (n=9) had mutations in FA genes, including FANCA (n=3), BRCA2 (n=2), FANCM (n=1), FANCD2 (n=1), PALB2 (n=1), and BRIP1 (n=1). Table shows clinical characteristics of participants with mutations in FANCA, FANCM, and FANCD2. Further mutation spectrum included: CHEK2 (n=3), NBN (n=2), MUTYH (n=2), BRCA (n=1), ATM (n=1), HOXB13 (n=1), APC (n=1). Compared to population prevalence, FA mutation prevalence was significantly higher overall (5.0% vs. 0.6%, p = 0.010) and among mutation carriers (45% vs. 0.6%, p<0.001). Conclusions: While prevalence of FA genes BRCA2, PALB2, and BRIP1 is well-described, our study supports testing a broader range of FA genes given the prevalence rates, potential implications for clinical trials, targeted therapy, inherited syndromes, and reproductive implications.[Table: see text]

Bevacizumab-induced hypertension and proteinuria: a genome-wide study of more than 1000 patients

BACKGROUND

Hypertension and proteinuria are common bevacizumab-induced toxicities. No validated biomarkers are available for identifying patients at risk of these toxicities.

METHODS

A genome-wide association study (GWAS) meta-analysis was performed in 1039 bevacizumab-treated patients of European ancestry in four clinical trials (CALGB 40502, 40503, 80303, 90401). Grade ≥2 hypertension and proteinuria were recorded (CTCAE v.3.0). Single-nucleotide polymorphism (SNP)-toxicity associations were determined using a cause-specific Cox model adjusting for age and sex.

RESULTS

The most significant SNP associated with hypertension with concordant effect in three out of the four studies (p-value <0.05 for each study) was rs6770663 (A > G) in KCNAB1, with the G allele increasing the risk of hypertension (p-value = 4.16 × 10-6). The effect of the G allele was replicated in ECOG-ACRIN E5103 in 582 patients (p-value = 0.005). The meta-analysis of all five studies for rs6770663 led to p-value = 7.73 × 10-8, close to genome-wide significance. The most significant SNP associated with proteinuria was rs339947 (C > A, between DNAH5 and TRIO), with the A allele increasing the risk of proteinuria (p-value = 1.58 × 10-7).

CONCLUSIONS

The results from the largest study of bevacizumab toxicity provide new markers of drug safety for further evaluations. SNP in KCNAB1 validated in an independent dataset provides evidence toward its clinical applicability to predict bevacizumab-induced hypertension. ClinicalTrials.gov Identifier: NCT00785291 (CALGB 40502); NCT00601900 (CALGB 40503); NCT00088894 (CALGB 80303) and NCT00110214 (CALGB 90401).

Integration of circulating tumor cell and neutrophil-lymphocyte ratio to identify high-risk metastatic castration-resistant prostate cancer patients

BACKGROUND

The neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and circulating tumor cells (CTCs) have been associated with survival in castration-resistant prostate cancer (CRPC). However, no study has examined the prognostic value of NLR and PLR in the context of CTCs.

METHODS

Baseline CTCs from mCRPC patients were enumerated using the CellSearch System. Baseline NLR and PLR values were calculated using the data from routine complete blood counts. The associations of CTC, NLR, and PLR values, individually and jointly, with progression-free survival (PFS) and overall survival (OS), were evaluated using Kaplan-Meier analysis, as well as univariate and multivariate Cox models.

RESULTS

CTCs were detected in 37 (58.7%) of 63 mCRPC patients, and among them, 16 (25.4%) had ≥5 CTCs. The presence of CTCs was significantly associated with a 4.02-fold increased risk for progression and a 3.72-fold increased risk of death during a median follow-up of 17.6 months. OS was shorter among patients with high levels of NLR or PLR than those with low levels (log-rank P = 0.023 and 0.077). Neither NLR nor PLR was individually associated with PFS. Among the 37 patients with detectable CTCs, those with a high NLR had significantly shorter OS (log-rank P = 0.024); however, among the 26 patients without CTCs, the OS difference between high- and low-NLR groups was not statistically significant. Compared to the patients with CTCs and low NLR, those with CTCs and high levels of NLR had a 3.79-fold risk of death (P = 0.036). This association remained significant after adjusting for covariates (P = 0.031). Combination analyses of CTC and PLR did not yield significant results.

CONCLUSION

Among patients with detectable CTCs, the use of NLR could further classify patients into different risk groups, suggesting a complementary role for NLR in CTC-based prognostic stratification in mCRPC.

Radiographic progression-free survival as a surrogate endpoint of overall survival in men with metastatic castrate-resistant prostate cancer

5057

Background: Radiographic progression-free survival (rPFS) is commonly used as a co-primary endpoint in randomized clinical trials in men with metastatic castrate-resistant prostate cancer (mCRPC). However, rPFS has not been established as a valid surrogate endpoint of overall survival (OS) in men with mCRPC. Here, we hypothesized that rPFS is a reliable surrogate for OS in mCRPC. We also explored whether PFS is a valid surrogate endpoint of OS at the aggregate trial level. Methods: We performed a systematic search of the literature encompassing the period January 2004-December 2020 using PubMed and clinical trials.gov to identify completed phase III trials in mCRPC post-docetaxel. Eligible trials had to be randomized phase III therapeutic trials that reported OS, PFS or rPFS. OS was measured from the date of random assignment to date of death from any cause or date of last follow-up. rPFS was defined as the time from random assignment to date of disease progression on CT and/or Tc bone scan per trial definition or death from any cause, whichever occurred first. PFS included PSA progression as a component of the composite endpoint. Trial level surrogacy was evaluated by fitting linear regression on the treatment effect of rPFS (or PFS) and OS (in other words, the weighted linear regression of the log(hazard ratio) of OS on the log(hazard ratio) of rPFS). It was pre-specified that rPFS would be considered a valid surrogate for OS if R² was 0·7 or higher. Results: We identified 33 in men with mCRPC post docetaxel approval. We assessed the association between PFS and OS in 29,456 patients from 30 trials. Overall, a moderate correlation was observed at the trial level between OS and PFS ( R2 = 0.46, 95 %CI = 0.20-0.68) in these trials. In 18 trials with 16,818 mCRPC patients where rPFS was considered as a key endpoint, a moderate correlation between the treatment effects on rPFS and OS was observed at the trial level ( R2= 0.65, 95% CI = 0.23-0.87). Conclusions: This meta-analysis demonstrates moderate correlation between treatment effects of rPFS and OS in patients with mCRPC. However, rPFS did not meet the pre-specified surrogacy threshold of 0.7. Clinical trial information: several.

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 > 18 wks, the median time on tx in the cohort of pts analyzed. A threshold of > 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 > 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 < 0.01) and C3D15 (4.8X, p < 0.001) in pts with tx duration > 18 wks and at baseline in pts who had PSA reductions (3.1X, p < 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 > 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.

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

TPS183

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

A phase I/II study of REGN5678 (Anti-PSMAxCD28, a costimulatory bispecific antibody) with cemiplimab (anti–PD-1) in patients with metastatic castration-resistant prostate cancer

TPS174

Background: Bispecific antibodies (bsAbs) are emerging as a protein-based therapeutic strategy for directing T-cell-mediated cytotoxicity in a tumor antigen-specific manner, typically by binding to both tumor antigen and the CD3 receptor on T-cells. REGN5678 is a human IgG4-based, first-in-class costimulatory bsAb designed to target prostate tumors by bridging prostate specific membrane antigen expressing tumor cells with the costimulatory receptor, CD28, on T-cells, and providing amplified T-cell receptor-CD3 complex-mediated T-cell activation within the tumor through the activation of CD28 signaling. At the tumor site, REGN5678 may synergize with PD-1 inhibitors. In mouse models, REGN5678 in combination with a PD-1 antibody has improved anti-tumor activity compared with either therapy alone (Waite JC et al. Sci Transl Med. 2020:12;549). Methods: This is an open label, Phase I/II, first-in-human study evaluating safety, tolerability, pharmacokinetics (PK), and anti-tumor activity of REGN5678 alone and in combination with cemiplimab in patients with metastatic castration resistant prostate cancer (mCRPC) who progressed after prior therapy (NCT03972657). For inclusion, patients must have received at least two prior lines of systemic therapy (in addition to androgen deprivation therapy) approved for metastatic and/or castration-resistant disease including a second-generation anti-androgen therapy. REGN5678 is administered weekly; cemiplimab (350 mg) is administered once every 3 weeks. During dose escalation, a 3-week safety lead-in of REGN5678 monotherapy will be administered prior to addition of cemiplimab. Study therapies are administered until disease progression, intolerable adverse events, withdrawal of consent, or study withdrawal criterion is met. The primary objectives in dose escalation are to evaluate safety, tolerability, and PK of REGN5678 alone and in combination with cemiplimab. Expansion cohort(s) will be enrolled once a maximum-tolerated REGN5678/cemiplimab dose is reached, or if a recommended Phase 2 dose or doses have been determined. During the expansion phase, the primary objective is to assess clinical activity, as measured by objective response rate of REGN5678 in combination with cemiplimab per modified Prostate Cancer Working Group 3 criteria. At selected sites, prostate-specific membrane antigen PET/CT scans are performed at baseline and select time points on study. This study is currently open to enrollment. Clinical trial information: NCT03972657.

Identification of prognostic and predictive biomarkers of overall survival (OS) and progression-free survival (PFS) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) treated with docetaxel, prednisone (DP) +/- bevacizumab (B) in CALGB 90401 (Alliance)

154

Background: CALGB 90401 was a phase III trial of 1050 pts with mCRPC comparing DP+B versus DP alone. While this trial did not show an improvement in OS in the overall population, there were improved PSA response, objective responses and delays in progression suggesting that subsets of men may derive benefit from this combination The purpose of this analysis was to identify and validate plasma angiokines (PAs) that are prognostic or predictive of OS and PFS benefit from bevacizumab in men with mCRPC. Methods: Baseline EDTA plasma samples from 679 consenting pts were analyzed using an optimized multiplex ELISA platform for 25 PAs related to tumor growth, angiogenesis, and inflammation. The data were randomly split into training (n = 462) and testing (n = 217) sets. The proportional hazards model was utilized to test for the prognostic and predictive importance of the PAs in predicting OS and PFS, with and without adjustment for clinical risk score. Analyses were adjusted for multiplicity using false discovery rate (FDR). Results: For the prognostic analysis, 14 PAs (angiopoeitin-2, BMP9, Chromogranin A, HER3, HGF, ICAM-1, IL6, OPN, PIGF, TIMP, TSP2, VEGFA, VEGFR1, and VEGF-R3) were prognostic of OS and 8 PAs (angiopoietin-2, HER3, ICAM-1, IL6, OPN, TIMP, VEGFA and VEGF-R3) were prognostic of PFS in the training set (FDR < 0.05). None of the PAs were statistically significant for OS or PFS when adjusting by the clinical risk score, suggesting that angiokine levels associate with clinical prognostic factors. OPN was predictive of OS in the training set but no other PAs were found to be predictive of PFS improvement with DP+B. Using the testing set, we were unable to validate that OPN is predictive of OS/PFS or any of the PAs are predictive biomarkers of the OS or PFS benefits of DP+B over DP alone in men with mCRPC. Conclusions: While PAs are prognostic for OS and PFS in univariate analysis, we were unable to validate the results in the testing set. Furthermore, we did not identify any PAs that are predictive of benefit from the addition of bevacizumab to docetaxel/prednisone with ADT in this setting. Nevertheless, these remain worthy of further evaluation as potential therapeutic targets.

Preserving Well-being in Patients With Advanced and Late Prostate Cancer

Androgen deprivation therapy, alone or in combination with androgen signaling inhibitors, is a treatment option for patients with advanced prostate cancer (PC). When making treatment decisions, health care providers must consider the long-term effects of treatment on the patient's overall health and well-being. Herein, we review the effects of these treatments on the musculoskeletal and cardiovascular systems, cognition, and fall risk, and provide management approaches for each. We also include an algorithm to help health care providers implement best clinical practices and interdisciplinary care for preserving the overall well-being of PC patients.

Urine Extracellular Vesicle GATA2 mRNA Discriminates Biopsy Result in Men with Suspicion of Prostate Cancer

PURPOSE

Prostate specific antigen has limited performance in detecting prostate cancer. The transcription factor GATA2 is expressed in aggressive prostate cancer. We analyzed the predictive value of urine extracellular vesicle GATA2 mRNA alone and in combination with a multigene panel to improve detection of prostate cancer and high risk disease.

MATERIALS AND METHODS

GATA2 mRNA was analyzed in matched extracellular vesicles isolated from urines before and after prostatectomy (16) and paired urine and tissue prostatectomy samples (19). Extracellular vesicle GATA2 mRNA performance to distinguish prostate cancer and high grade disease was tested in training (52) and validation (165) cohorts. The predictive value of a multigene score including GATA2, PCA3 and TMPRSS2-ERG (GAPT-E) was tested in both cohorts.

RESULTS

Confirming its prostate origin, urine extracellular vesicle GATA2 mRNA levels decreased significantly after prostatectomy and correlated with prostate cancer tissue GATA2 mRNA levels. In the training and validation cohort GATA2 discriminated prostate cancer (AUC 0.74 and 0.66) and high grade disease (AUC 0.78 and 0.65), respectively. Notably, the GAPT-E score improved discrimination of prostate cancer (AUC 0.84 and 0.72) and high grade cancer (AUC 0.85 and 0.71) in both cohorts when compared with each biomarker alone and PT-E (PCA3 and TMPRSS2-ERG). A GAPT-E score for high grade prostate cancer would avoid 92.1% of unnecessary prostate biopsies, compared to 61.9% when a PT-E score is used.

CONCLUSIONS

Urine extracellular vesicle GATA2 mRNA analysis improves the detection of high risk prostate cancer and may reduce the number of unnecessary biopsies.

Phase Ib/II neoadjuvant (N-) pembrolizumab (P) and chemotherapy for locally advanced urothelial cancer (laUC): Final results from the cisplatin (C)- eligible cohort of HCRN GU14-188

5047

Background: Patients (pts) with laUC who are C-eligible for N- therapy may benefit from combination chemo-immunotherapy. Cohort 1 (C1) of the GU14-188 trial is a phase 1b/2 trial designed to assess the tolerability and efficacy of N- gemcitabine (G), C, and P in pts with laUC. The current standard of care is ddMVAC with a pathologic non-muscle invasive rate (PaIR, ≤pT1N0) of ~44%. Methods: Eligible pts for C1 were surgical candidates and C-eligible with cT2-4aN0M0 bladder UC. Enrollment followed a Simon 2-stage design for H0 of interval futility which was rejected at stage 1, and fully enrolled. Phase 1b (no DLT) /2 treatments were the same: P 200mg q3wks on day 8 x5 doses; with C (70mg/m2) day 1, and G (1000mg/m2) days 1 and 8 of a 21 day cycle (cy), for 4 cy; followed by radical cystectomy (RC). Minimum criteria for evaluation of safety: 1 dose of P, and for efficacy: 2 doses P and RC. The primary endpoint of PaIR was assessed at RC and designed for 86% power with 4% significance to detect a difference from 23 to 48%. Secondary endpoints include relapse free survival and overall survival. Results: 43 pts were enrolled to C1 with a median (mdn) age 64, 63% male, 51% > cT2. Mdn per-pt doses given (attempted) for: P:5(5), C:4(4), G:8(8). The PaIR was 61.1% (95%CI 0.45, 0.75), P0 (ypT0N0) rate of 44.4%, and did not correlate with baseline PD-L1 score. Downstage to PaIR occurred in 53% of cT2, and 74% of cT3/4. Mdn time to RC from last dose was 5.3wks. Seven were not included in the primary analysis: 4 (9.3%) without RC, 1 progressed, 1 lost to f/u during C1, 1 did not receive required protocol therapy. There was 1 death on post-RC day 9 due to mesenteric ischemia. Of 4 pts who did not have RC, 3 refused and 1 due to gr4 thrombocytopenic purpura; 4pts are alive and without recurrence at mdn f/u of 32mo. One pt with presumed gr3 MI during cy 4 had a negative inpt cardiac workup and completed therapy and RC without further AE. One gr4 hyponatremia and ten gr3 events did not preclude RC (2-each thromboembolism, elevated creatinine, hyponatremia;1-each: dehydration, emesis, neutropenic fever, infection). Gr 3/4 cytopenias occurred in 57% of pts. At mdn f/u of 34.2mo (3.9-47.4), the estimated 36mo RFS, OS, and DSS is 63%, 82%, and 87%, respectively. Conclusion: Neoadjuvant GC with P in laUC has manageable toxicity and has improved pathologic outcomes compared to historic controls. Durable long-term survival in those with- and without -RC is noteworthy in this advanced cohort. KEYNOTE 866, NCT03924856, is a Phase III study of GC with perioperative P. Clinical trial information: NCT02365766 .

Examining the real-world utility of immune checkpoint inhibitors in genitourinary oncology: A single-institution retrospective

e17112

Background: Immune Checkpoint Inhibitors (ICI) are increasingly utilized for genitourinary (GU) malignancies. However, data is lacking on the efficacy of these drugs in “real-world” populations - patients who do not fit the strict clinical trial criteria, but may still benefit from therapy. We performed a retrospective analysis of patients receiving ICI at a single tertiary-care institution, with special attention to clinical trial enrollment, adverse events, progression and survival. Methods: Patients receiving ICI for GU malignancies at Thomas Jefferson University Hospital from January 2017 to January 2019 were identified. Descriptive statistics of treatment and pathologies were performed. Progression-free survival (PFS) was calculated from start of ICI to documentation of progression or last follow-up. PFS and overall survival were assessed using Kaplan Meier log-rank test, stratified by trial enrollment. Results: 111 patients were included: 37 on ICI clinical trial, 70 received ICI “off-trial” and 4 received ICI in both settings. 11 patients (10%) underwent multiple courses of ICI throughout treatment. The number of patients initiating ICI increased annually; by 2018, the number of patients initiated on ICI “off-trial” exceeded those initiating ICI “on-trial” (79% vs 21%). Treated pathology included Urothelial Carcinoma (UC; 42%), Renal Cell Carcinoma (RCC; 28%), and Prostate Adenocarcinoma (PCa; 20%). “Off-trial” ICI was more often administered later in the disease course, compared to a more even distribution of “on-trial” ICI administration. Mean PFS and OS for both cohorts can be seen in Table. Conclusions: As seen in our single-institution referral center, the use of immune checkpoint inhibitors has significantly increased – and is now more commonly used off-trial than on-trial. As their use becomes more common, their efficacy in “off-trial” populations must be further investigated. [Table: see text]

Cabozantinib in combination with atezolizumab in patients with metastatic castration-resistant prostate cancer: Results of cohort 6 of the COSMIC-021 study

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Background: Cabozantinib (C) may enhance response to immune checkpoint inhibitors (ICIs) by promoting an immune-permissive microenvironment and has shown encouraging activity in combination with ICIs in tumor types including RCC and HCC. C and atezolizumab (A) have shown low objective response rates as monotherapy in metastatic castration-resistant prostate cancer (mCRPC) (Smith JCO 2012; Kim JCO 2018). COSMIC-021 (NCT03170960), a multinational phase 1b study, is evaluating the combination of C + A in various solid tumors. We report results for Cohort 6 in mCRPC. Methods: Eligible patients (pts) were required to have radiographic progression in soft tissue after enzalutamide and/or abiraterone, measurable disease, and an ECOG PS of 0 or 1. Prior chemotherapy for mCSPC was permitted. Pts received C 40 mg PO QD and A 1200 mg IV Q3W. CT/MRI scans were performed Q6W for the first year and Q12W thereafter. The primary endpoint is ORR per RECIST 1.1. Other endpoints include safety, ORR per irRECIST, duration of response (DOR), PFS, and OS. Results are presented for the first 44 pts enrolled. Results: Median follow-up as of Dec 20, 2019 was 12.6 mo (range 5, 20) for the 44 mCRPC pts. Median age was 70 y (range 49, 90), 50% had ECOG PS 1, 34% had visceral metastases, and 61% had extrapelvic lymph node metastases. 27% had prior docetaxel and 52% had 2 prior novel hormonal therapies. The most common any grade treatment-related adverse events (TRAEs) were fatigue (50%), nausea (43%), decreased appetite (39%), diarrhea (39%), dysgeusia (34%), and PPE (32%). One grade 5 TRAE of dehydration was reported in a 90 y/o. Median duration of treatment was 6.3 mo. ORR per RECIST 1.1 among all 44 pts was 32% (2 CRs [4.5%] and 12 PRs [27%]); 21 (48%) pts had SD resulting in a disease control rate of 80% in all pts. One pt with PD per RECIST 1.1 had an irPR per irRECIST. ORR per RECIST 1.1 was 33% in 36 pts with high-risk disease (visceral and/or extrapelvic lymph node metastases). Median DOR for all pts with response per RECIST 1.1 was 8.3 mo (range 2.8, 9.8+). 17 (50%) of 34 pts with post-baseline PSA evaluation had a decrease in PSA. In 12 responders with post-baseline PSA evaluation, 8 (67%) had a PSA decrease ≥50%. Tumor PD-L1 expression will also be reported. Conclusions: The combination of C + A had a tolerable safety profile and demonstrated clinically meaningful activity with durable responses in men with mCRPC. Given the encouraging activity in these pts, especially in those with high-risk disease, further evaluation of C + A in men with mCRPC is being pursued. Clinical trial information: NCT03170960 .

Clinical outcomes and markers of treatment response in a randomized phase II study of androgen deprivation therapy with or without palbociclib in RB-intact metastatic hormone-sensitive prostate cancer (mHSPC)

5573

Background: Targeted therapies based on tumor molecular markers are not currently used in mHSPC. Palbociclib, a CDK4/6 inhibitor, blocked proliferation and promoted G1 arrest in a Rb-and Cyclin D-dependent manner in preclinical models of HSPC. We hypothesized that co-targeting AR (ADT) and cell cycle (palbociclib) would improve outcomes in mHSPC pts. Methods: mHSPC pts with Rb intact tumors based on IHC of metastatic tumor biopsy were stratified and randomized (1:2) to Arm A: ADT or Arm B: ADT+ palbociclib (125mg 3 weeks on, 1 week off). Primary endpoint was confirmed PSA RR (≤ 4 ng/mL) after 28 weeks of therapy. Secondary endpoints included safety/tolerability, PFS, PSA and radiographic RR. Metastatic biopsy and primary tumors were subjected to whole exome and transcriptomic sequencing where available. CTC’s were enumerated at various time points. Results: 72 eligible pts (median age 67 years, PSA 73ng/mL) with newly diagnosed mHSPC were registered and underwent biopsy. 97% retained RB expression (IHC). 62 pts were stratified by disease extent and early initiation of ADT, and randomized. 60 pts initiated therapy (Arm A: 20; Arm B: 40). Adverse events were reported previously. 80% of pts (Arm A: 16/20, Arm B: 32/40; p = 0.87) on both arms met primary PSA endpoint (≤4ng/mL at 28 weeks). PSA undetectable rate at 28 weeks was Arm A: 50% (10/20) and Arm B: 43% (17/40; p = 0.5). Measurable disease RR: Arm A: 89% and Arm B: 89%. 12-month biochemical PFS was Arm A 69% (95%CI: 44-85%), Arm B 74% (95%CI: 57-85%). 41 patients on trial underwent sequencing of metastatic biopsy and 10 patients had matched primary prostate tumor sequencing results. CCND1 amp, 8q gain, PTEN and KMT2C mutations were each observed in metastatic, but not paired prostate primary tumors. TP53, PIK3 pathway (PIK3CA, AKT1, PTEN) mutations and 8q gains were associated with reduced PSA PFS [HR (95%CI): 3.0 (1.2-7.2), p = 0.018; 3.2(1.03-10),p = 0.044; 4.96 (1.8-12), p = 0.001, respectively]. Pretreatment CTCs were associated with lower PSA CR (p = 0.04) and shorter PFS (12-month PFS: 58% vs. 86%, p = 0.031). Conclusions: A tissue based biomarker preselected trial is feasible in mHSPC. ADT + palbociclib did not impact outcomes. Pretreatment CTC counts, TP53 and PIK3 pathway mutations, and 8q gain may offer prognostic value in mHSPC. Support: Movember-PCF Challenge Award, Pfizer. Clinical trial information: NCT02059213 .

Video vs. in-person genetic counseling for men considering germline prostate cancer testing: A patient-choice study

1577

Background: Germline testing (GT) for prostate cancer (PCA) is rapidly increasing with higher demand for genetic counseling (GC). Alternate GC strategies need to be studied to address pretest informed consent. Here we conducted a patient-choice study of pretest video-based genetic education (VBGE) or in-person GC (IPGC) and assessed men’s preference and patient-reported outcomes from the first cohort of the Evaluation and Management for Prostate Oncology, Wellness, and Risk (EMPOWER) study. Methods: Eligibility for EMPOWER includes any male with PCA or at-risk for PCA based on family history or African American race. Men may choose pretest IPGC or VBGE. All receive results by a genetic professional. Demographics and PCA features were collected at baseline. The following outcomes and scales were assessed: baseline anxiety (GAD-7 scale), change in cancer genetics knowledge from baseline (Giri 2019), decisional conflict for GT (O’Connor 1993), and satisfaction (DeMarco 2004). Understanding of personal GT results was assessed after disclosure (Giri 2019). Descriptive statistics summarized results with counts and percentages for categorical variables and mean and standard deviation for continuous variables. Data were compared with Fisher’s exact, Chi-squared, or Wilcoxon two-sample tests, as appropriate. Mean change in cancer genetics knowledge was compared with t-tests. Significance level was set a priori at 0.05. All analyses were performed with SAS 9.4 (Cary, NC). Results: At the time of this analysis, 94 men were enrolled. Characteristics of the cohort were: White (88.3%), bachelor’s degree (67%), PCA diagnosis (93%), mean age of consent 59 years (IPGC) and 61 years (VBGE), Gleason > = 8 (32%), and > = T3 (31%). The majority preferred VBGE (77%) vs. IPGC (23%). Men who opted for IPGC had lower educational levels ( < = high school/GED) (18% IPGC vs 7% VBGE) and reported higher baseline anxiety (45% IPGC vs. 24% VBGE). Cancer genetics knowledge improved significantly with IPGC vs. VBGE (+2.5 vs +0.8; p < 0.01). No differences were observed in decisional conflict, satisfaction, or understanding of personal GT results between IPGC vs. VBGE. Both groups had high rates of GT uptake (IPGC 91%, VBGE 93%). Pathogenic mutations were identified in 15% in IPGC group and 10.4% in VBGE group. Conclusions: A substantial proportion of men opted for VBGE, and results suggest that VBGE is comparable to IPGC for men considering PCA GT. IPGC may be more suitable for men with lower knowledge of cancer genetics and greater levels or anxiety. Further study is warranted.

Phase II neoadjuvant (N-) gemcitabine (G) and pembrolizumab (P) for locally advanced urothelial cancer (laUC): Interim results from the cisplatin (C)-ineligible cohort of GU14-188

5019

Background: Patients (pts) with laUC who are C-ineligible have inferior survival compared to counterparts who receive C based N-therapy and have a pathologic response at radical cystectomy (RC). Cohort 2 (C2) of the GU14-188 trial is designed to assess the tolerability and efficacy of N- G and P in laUC pts who are C-ineligible. Methods: Eligible pts for C2 were surgical candidates and C-ineligible with cT2-4aN0M0 bladder UC or mixed histology. Enrollment followed a Simon 2-stage design for H0 of interval futility which was rejected at stage 1, and fully enrolled. Pts were treated with N- G (1000mg/m2) on days 1, 8, and 15 of a 28 day cycle (cy) for a total of 3 cy, and overlapped with P 200mg every 3wks starting on cy 1 day 8 x 5 doses. Minimum criteria for evaluation of safety: 1 dose of P, and for efficacy: 2 doses P and RC. The primary endpoint of pathologic muscle invasive response rate (PaIR, ≤pT1N0) was assessed at RC and designed for 86% power, 4% significance to detect PaIR difference from 18 to 40%. Molecular subtyping is planned. Results: 37 pts were enrolled to C2 with a median (mdn) age of 72, 70% male, 55% > cT2. C-ineligibility was due to renal function (49%), hearing (30%), neuropathy (12%). Mdn per-pt doses given (intended) for P:5(5) and G:9(9). The PaIR was 51.6% (95%CI 0.35, 0.68), P0 (ypT0N0) rate of 45.2%, and neither correlated with baseline PD-L1 score. Downstage to PaIR occurred in 57% of pts with cT2, and 47% of > cT2. Mdn time to RC from last dose was 5.6wks. Six were not included in the primary analysis: 3 (8.1%) did not have RC due to progression (RFS censored), 2 did not receive required protocol therapy, and 1 withdrew consent. At mdn follow up of 10.8mo (4-24), the estimated 12mo RFS, OS, and DSS is 74.9%, 93.8%, and 100%, respectively. Treatment related AE included grade (gr) 3/4 neutropenia (24%), anemia (13%), and platelets (5%). There were no gr 4 non-heme AE, and of 14 (36%) pts with gr 3, 12 did not preclude RC. Of these, there were 4 gr 3 investigator assessed immune related adverse events (IAirAE) of pneumonitis (5%), colitis (3%), and AST elevation (3%). Though IAirAE improved, protocol therapy was discontinued in 3 pts: 2 did not have RC due to progression. Conclusion: N- G with P in C-ineligible pts with laUC is feasible with manageable toxicity, and has a pathologic downstage rate comparable to standard of care in the C-eligible population. G and P warrants further study with component contribution as a C- free N- option in laUC. Clinical trial information: NCT02365766 .

Radium-223 (Rad) and niraparib (Nira) treatment (tx) in castrate-resistant prostate cancer (CRPC) patients (pts) with and without prior chemotherapy (chemo)

5540

Background: Despite multimodality txs such as surgery, radiotherapy, hormonal tx and chemo, metastatic CRPC (mCRPC) prognosis remains poor. Research suggests PARP-1 is a key regulator of androgen receptor (AR) signaling and transition to lethal CRPC. Nira is a safe, potent and selective PARP-1/2 inhibitor that has shown single agent clinical activity in CRPC, and Rad is an alpha particle emitter. Addition of PARP inhibition may further enhance the clinical benefit of Rad. Nira has a favorable safety profile however, data on safety, tolerability and efficacy of Nira plus radiotherapy is limited. We hypothesize that targeting the PARP-1/AR axis in combination with radiation is safe and will improve mCRPC management. Methods: This is a phase (ph) Ib dose finding study (NCT03076203) of pts with progressive mCRPC using Time-to-Event Continual Reassessment Method (TITE-CRM). The primary objective is to determine the optimum ph II dose of Nira plus Rad (55 kBq/kg of body weight) in pts with and without prior chemo. Secondary endpoints include PSA reduction at 12 weeks (wks) and radiographic progression-free survival at 6 months. Pts enrolled to one of three dose levels of Nira (100, 200, and 300 mg PO daily). After completing 6 cycles of Rad, pts continued on Nira alone until objective progression, tx intolerance or pt decision. TITE-CRM identifies the maximum tolerated dose (MTD) based on toxicities observed over 12 wks of tx. Results: Between Oct 2017 and Jan 2020, 30 pts were enrolled (15 per stratum). Median age was 70 years; ECOG performance status was 0. The MTD of Nira was 100 mg in the chemo-exposed arm and 200 mg in the chemo-naïve arm. 19 Grade ≥ 3 adverse events were possibly related to tx: lymphocyte count decrease (n = 4, 13%), neutrophil count decrease (n = 3, 10%), anemia (n = 3, 10%), hypertension (n = 3, 10%), platelet count decrease (n = 2, 7%), creatinine increase (n = 1, 3%), hydronephrosis (n = 1, 3%), nausea (n = 1, 3%), white blood cell count decrease (n = 1, 3%). Tx duration and PSA response are shown in the table. Conclusions: Nira plus Rad was determined to be safe and tolerable. The MTD of Nira was identified and is pending ph II investigation. Managed by: Prostate Cancer Clinical Trials Consortium; Funded by: Janssen Scientific Affairs and Bayer Healthcare Pharmaceuticals, Inc Clinical trial information: NCT03076203 . [Table: see text]

Effect of androgen deprivation therapy combined with nivolumab on the systemic antitumor immune response in castration-sensitive prostate cancer

e17503

Background: To date, immunotherapy has limited efficacy in castration-resistant prostate cancer. However, we previously reported that androgen deprivation therapy (ADT) has significant immunomodulatory effects and can induce a complex immune cell infiltrate before castration-resistance develops. Therefore, we designed an ongoing clinical trial to assess the effects of immunotherapy plus ADT in men with recurrent castration-sensitive prostate cancer (CSPC) (NCT03689699). We hypothesized that PD-1 blockade given at the time of castration could induce systemic anti-tumor immune responses with epitope spreading and modulate key circulating cytokine networks. Methods: 15 patients with recurrent CSPC were treated with nivolumab (480mg) every 4 weeks for 8 weeks followed by nivolumab plus degarelix for an additional 16 weeks. Sera was collected at 3 time points: pre-treatment, after nivolumab alone (8 weeks) and at completion of therapy with nivolumab plus degarelix (24weeks). To assess the therapeutic effects on systemic humoral immune responses and to evaluate for induction of epitope spreading, we analyzed treatment-induced serum IgGs against an array of self-antigens over time. We also performed a 44-parameter electrochemiluminescence assay to measure the effects of therapy on innate cytokines and the Th1/Th2 and Th17 pathways. Results: ADT combined with PD-1 blockade led to significant changes in systemic immunity including induction of humoral antigen spread with IgG responses to secondary tumor antigens including PSA, KLK2, K-Ras and modulation of key circulating cytokines. We observed a significant increase in mean levels of IFN-gamma (8.68 +/- 10.74 pg/ml vs 9.53 +/- 7.36 pg/ml), an increase in IL-10 (0.37 +/- 0.29 pg/ml vs 0.66 +/- 0.53 pg/ml) and a decrease in IL-8 (106.7 +/- 275.47 pg/ml vs 25.49 +/- 23.09 pg/ml) when comparing cytokine levels before and after nivolumab plus degarelix respectively. Conclusions: ADT plus nivolumab led to significant changes in systemic immunity and overall appeared to promote a pro-inflammatory state. This immune response also appeared tumor specific with induction of humoral responses against secondary tumor antigens. However we also observed changes in targetable immunosuppresive cytokines like interleukin-8 and are currently testing whether ADT plus combined PD-1 and IL-8 blockade can further promote robust anti-tumor immune responses in prostate cancer. Clinical trial information: NCT03689699 .

Comparative Survival of Asian and White Metastatic Castration-Resistant Prostate Cancer Men Treated With Docetaxel

There are few data regarding disparities in overall survival (OS) between Asian and white men with metastatic castration-resistant prostate cancer (mCRPC). We compared OS of Asian and white mCRPC men treated in phase III clinical trials with docetaxel and prednisone (DP) or a DP-containing regimen. Individual participant data from 8820 men with mCRPC randomly assigned on nine phase III trials to receive DP or a DP-containing regimen were combined. Men enrolled in these trials had a diagnosis of prostate adenocarcinoma. The median overall survival was 18.8 months (95% confidence interval [CI] = 17.4 to 22.1 months) and 21.2 months (95% CI = 20.8 to 21.7 months) for Asian and white men, respectively. The pooled hazard ratio for death for Asian men compared with white men, adjusted for baseline prognostic factors, was 0.95 (95% CI = 0.84 to 1.09), indicating that Asian men were not at increased risk of death. This large analysis showed that Asian men did not have shorter OS duration than white men treated with docetaxel.

Clinical outcomes in men of diverse ethnic backgrounds with metastatic castration-resistant prostate cancer

BACKGROUND

We have shown previously in multivariable analysis that black men had 19% lower risk of death than white men with metastatic castration-resistant prostate cancer (mCRPC) treated with a docetaxel and prednisone (DP)-based regimen. The primary goal of this analysis was to compare progression-free survival (PFS), biochemical PFS, ≥50% decline in prostate-specific antigen (PSA) from baseline and objective response rate (ORR) in white, black and Asian men with mCRPC treated with a DP-based regimen.

PATIENTS AND METHODS

Individual patient data from 8820 mCRPC men randomized on nine phase III trials to a DP-containing regimen were combined. Race used in the analysis was based on self-report. End points were PFS, biochemical PSA, ≥50% decline in PSA from baseline and ORR. The proportional hazards and the logistic regression models were employed to assess the prognostic importance of race in predicting outcomes adjusting for established prognostic factors.

RESULTS

Of 8820 patients, 7528 (85%) were white, 500 (6%) were black, 424 were Asian (5%) and 368 (4%) had race unspecified. Median PFS were 8.3 [95% confidence interval (CI) 8.2-8.5], 8.2 (95% CI 7.4-8.8) and 8.3 (95% CI 7.6-8.8) months in white, black and Asian men, respectively. Median PSA PFS were 9.9 (95% CI 9.7-10.4), 8.5 (95% CI 8.0-10.3) and 11.1 (95% CI 9.9-12.5) months in white, black and Asian men, respectively.

CONCLUSIONS

We observed no differences in clinical outcomes by race and ethnic groups in men with mCRPC enrolled on these phase III clinical trials with DP.

Abiraterone acetate (AA) with or without cabazitaxel (CBZ) in treatment of chemotherapy naive metastatic castration-resistant prostate cancer (mCRPC)

84

Background: Loss of retinoblastoma tumor suppressor (RB) function has been shown to lead to CRPC and is strongly associated with poor outcome. RB functions as a transcriptional repressor; as such, loss of RB causes de-repression of pro-tumorigenic gene networks, including deregulation of the androgen receptor (AR) locus, excessive AR production, and castration-resistant (ligand independent) AR activity that can bypass hormone therapy. Our hypothesis is that leveraging RB status can direct treatment decisions. The primary objective of the trial (NCT02218606) was to determine the radiographic progression free survival (rPFS) of AA/prednisone (AAP) with and without CBZ in mCRPC patients (pts) that have progressed on primary androgen deprivation therapy and no prior AR directed therapy or chemotherapy. Methods: This is a multicenter non-comparative randomized phase 2 trial. Pts were randomized 1:1 to AAP with crossover to CBZ upon AAP failure (Arm 1), or the combination of AAP + CBZ (Arm 2). Randomization was stratified by the CALGB 90401 prognostic risk groups. The primary endpoint was rPFS (time from randomization to radiographic progression or death, whichever occurs first). Arms were analyzed separately. Results: Between October 2014 and March 2019, 93 pts were accrued; 81 were randomized. Median age was 68 years and ECOG performance status was 0 or 1. Endpoints are shown in Table. Therapies were well tolerated. Conclusions: Results of AAP + CBZ (Arm 2) in chemotherapy naïve pts suggest that men may derive benefit from the earlier use of CBZ with acceptable toxicity, supporting further study of this combination in mCRPC pts. Circulating Tumor Cells are being analyzed for changes in RB/AR expression. Managed by: Prostate Cancer Clinical Trials Consortium; Funding: Sanofi US; Support: Prostate Cancer Foundation. Clinical trial information: NCT02218606. [Table: see text]

Cabozantinib (C) in combination with atezolizumab (A) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): Results of Cohort 6 of the COSMIC-021 Study

139

Background: C may enhance response to immune checkpoint inhibitors by promoting an immune-permissive microenvironment. COSMIC-021 (NCT03170960), a multinational phase 1b study, is evaluating the combination of C with A in various solid tumors. We report interim results from Cohort 6 in mCRPC. Methods: Eligible pts were required to have radiographic progression in soft tissue after enzalutamide and/or abiraterone, measurable disease, and an ECOG PS of 0 or 1. Prior chemotherapy for mCSPC was permitted. Pts received C 40 mg PO qd and A 1200 mg IV q3w. CT/MRI scans were performed q6w for 52w and q12w thereafter. Bone scans were performed q12w. The primary endpoint is ORR per RECIST 1.1. Other endpoints include safety, ORR per irRECIST, duration of response (DOR), PFS, and OS. Results: As of Oct 2019, 44 mCRPC pts were enrolled with a median follow-up of 10.6 mo (range 3.4+, 17.9). Median age was 70 y (range 49, 90), 50% had ECOG PS 1, 34% had visceral metastases, and 61% had extrapelvic lymph node metastases. 27% of pts had prior docetaxel and 52% had ≥2 prior novel hormonal therapies. The most common any grade TEAEs were fatigue (57%), nausea (48%), decreased appetite (45%), diarrhea (39%), PPE (32%), and vomiting (32%). One Grade 5 TRAE of dehydration was reported in a 90 y/o. Median duration of treatment was 5.3 mo. The ORR per RECIST 1.1 among all pts was 32% (2 CRs [4.5%] and 12 PRs [27%]); 21 (48%) pts had SD giving a disease control rate of 80% in all pts. One pt with initial PD per RECIST 1.1 had an irPR per irRECIST. ORR per RECIST 1.1 was 33% in 36 pts with high-risk clinical features (visceral and/or extrapelvic lymph node metastases). Median DOR for all pts with response per RECIST 1.1 was 8.3 mo (range 1.38+, 9.76+). In 12 responders with at least 1 post-baseline PSA evaluation, 8 (67%) had a PSA decline ≥50%. Conclusions: The combination of C+A had a tolerable safety profile and demonstrated clinically meaningful activity with durable responses in men with mCRPC. Given the encouraging activity in these pts, especially in those with visceral and/or extra pelvic lymph node metastases, further evaluation of C+A in men with mCRPC is being pursued. Clinical trial information: NCT03170960.

Niraparib in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and biallelic DNA-repair gene defects (DRD): Correlative measures of tumor response in phase II GALAHAD study

118

Background: Niraparib, a highly potent and selective poly (ADP-ribose) polymerase inhibitor (PARPi) received breakthrough designation by US FDA for treatment of pts with BRCA1,2 mutant mCRPC who progressed on taxane and androgen receptor-targeted therapy. Circulating tumor cells (CTC) detection associates with poor outcomes, with declining counts consistent with improved survival [1,2]. Methods: GALAHAD study assessed niraparib (300 mg daily) in pts with mCRPC+DRD (NCT02854436). Patients with non-measurable soft tissue disease by RECIST 1.1 were required to have a baseline CTC count ≥1 cell/7.5 mL blood. CTC response was defined as CTC conversion to <5 for pts with baseline CTC≥5 and CTC drop to 0 post-baseline for pts with ≥1 baseline CTC. Alkaline phosphatase (ALP) was collected at each monthly cycle. Results: For primary efficacy population of pts with BRCA1/2 mutations, the objective response rate (ORR) by RECIST 1.1 criteria was 41.4%. CTC response rates for this population were as high as ORR regardless of measurability (Table). Time to CTC response for each CTC responder will be shown. Radiographic progression-free survival (rPFS) durations were similar for patients with a measurable disease response and patients with CTC conversion. Median duration of treatment for responders of any type was 6.7mo (range: 2–27). DRD status, both BRCA and non- BRCA, for each responder will also be discussed. Trends in disease burden and markers of bone metabolism will also be quantitatively explored including 24% pts who were on treatment for at least one cycle who had ≥25% decreased unfractionated ALP from baseline. Conclusions: Niraparib showed clinical activity with CTC response and decline in ALP levels in mCRPC pts having biallelic BRCA mutations, which further supports its recent breakthrough designation. Clinical trial information: NCT02854436. [Table: see text]

PET imaging urothelial bladder cancer: A novel approach

443

Background: Urothelial bladder cancer (UBC) inflicts >80,000 new patients annually. Since treatment is stage-dependent, accurate staging is crucial. Conventional imaging and biopsy are often unreliable. A large number of PET tracers, developed to improve imaging, have limitations e.g. urinary excretion compromising their ability to assess the bladder lumen and invasive tumors. This study is to validate a hypothesis that high density VPAC receptors expression on UBC cell surface, can be targeted to PET image UBC, to determine loco-regional disease and metastatic lesions. Methods: Cu-64-TP3805 (4±10% mCi), with its high affinity (3.1 x 10−9M) for VPAC, was given IV to 19 UBC patients (44-80 yrs), scheduled for radical cystectomy. Those eligible for neoadjuvant chemotherapy were treated as such. Urine and blood samples were collected on the day of scan. Whole body PET/CT images acquired 60 to 90 min later and read by two physicians. Surgery was performed 1 to 4 weeks later. Imaging results were correlated with histology. Results: There were no adverse events. Urinary excretion of Cu-64-TP3805 was negligible. Blood clearance was biphasic (t ½ a = 22.3 ±2.7 min ~ 85% and t ½ β = 118.2 ± 4.9 min ~ 15%). VPAC PET bladder images were true positive (TP) in 11, true negative (TN) in 4, false positive (FP) in 1 and false negative (FN) in 3 patients with 79% sensitivity (95% CI 49%-95%), 80% specificity (95% CI 28%-100%), 92% PPV (95% CI 62%-100%), and 57% NPV (95% CI 18%-90%). Prostate images were TP in 8, TN in 6, and FP in 5 patients, with 100% sensitivity (95% CI 63%-100%), 55% specificity (95% CI 23%-83%), 62% PPV (95% CI 32%-86%), and 100% NPV (95% CI 54%-100%). The 5 FP images revealed HGPIN on re-analysis. For lymph nodes, images were TP in 1, TN in 14 and FN in 4 patients, with 25% sensitivity (95% CI 1%-81%), 100% specificity (95% CI 78%-100%), 100% PPV (95% CI 3%-100%), and 83% NPV (95% CI 59%-96%). In one patient, several lesions were seen in the spine and iliac crest. Biopsy was positive for metastasis. In smokers (N=12) there was diffused or focal tracer uptake in the lungs. In 7 non-smokers, 3 with CT depicted abnormality had tracer lung uptake and 4 did not. Conclusions: These first in human pilot study data depict Cu-64-TP3805 VPAC targeting to image UBC as worthy of further investigation.

Molecular underpinnings of RB status as a biomarker of poor outcome in advanced prostate cancer

189

Background: There is emergent and compelling evidence to support RB status as a biomarker in advanced prostate cancer. RB loss is strongly associated with poor progression-free, disease-specific, and overall survival in prostate cancer (PCa). Preclinical studies in PCa have revealed RB positive tumors are more responsive to CDK4/6 inhibitors. An ongoing randomized Phase IB/II study of enzalutamide with and without ribociclib in patients with metastatic castration-resistant, chemotherapy naïve PCa has become a pioneer trial to include a positive RB status as inclusion criteria in a PCa study (NCT02555189). Beyond CDK4/6 inhibitors, therapeutic agents that target tumor metabolism have been introduced in the clinic. Current data suggests that RB status may be crucial to understand and predict therapeutic response to these agents within tumors. Methods: The biological significance of RB loss was studied utilizing isogenic model systems and human tumor xenografts of castration resistant prostate cancer (CRPC) with and without RB deletion. The mechanism that drives aggressive tumor phenotypes was identified through comprehensive transcriptomic, cistromic, and metabolomic analysis. Novel functions of RB were identified and the response to clinically-relevant therapeutics was examined. Results: Exclusively in CRPC, RB loss results in significant rewiring of cancer cell metabolism. Functional investigation revealed a causative link between RB loss and antioxidant production sufficient to alter responsiveness to genomic insult and selected chemotherapeutics. Observed changes in response to therapeutic intervention were attributed to RB-dependent modulation of intracellular reactive oxygen species. Conclusions: RB loss is strongly associated with poor outcome in advanced PCa. Molecular investigation identified RB-dependent rewiring of cancer cell metabolism as a significant consequence of RB loss, sufficient to alter response in model systems to therapeutic strategies of clinical relevance. These studies significantly advance understanding of the means by which RB loss enhances lethal tumor phenotypes, and are of relevance for development of RB status as a clinically actionable biomarker.

The multidisciplinary clinic approach for bladder cancer treatment in the neoadjuvant therapy era

475

Background: As urologic oncology becomes increasingly complex, the coordination of optimal and efficient care to patients can be challenging. Within our institution, we initiated a multidisciplinary center (MDC) comprised of urology, oncology and radiation oncology in 1996 to help meet these needs. The positive benefits of this approach have been demonstrated in other settings, but outcomes related to bladder cancer remain unclear, especially in the era of neoadjuvant (NA) therapy. Methods: Patients with localized or node positive muscle invasive bladder cancer (MIBC) without prior treatment were obtained from available multidisciplinary appointment records, dating from 7/5/17 to 9/25/19. Charts were then retrospectively reviewed to gather demographic data, treatment data, and pathological outcomes. Results: 66 patients fitting study criteria were identified. Average age was 71.3 years. 45 (68%) patients from this cohort were deemed to be radical cystectomy (RC) candidates, with 37 RC operations completed at time of record review. Of RC-eligible patients, 35/45 (77%) had received NA therapy, either in the form of neoadjuvant chemotherapy (NAC) and/or immunotherapy (NAI). 3 patients declined RC after receiving NAC. 15 patients underwent chemoradiation treatment (23%), while 7 (11%) underwent supportive care without definitive treatment. Downstaging at RC from MIBC (<=T1) was seen in 12/37 patients (32%), with a pT0 rate of 10% (4/37). Conclusions: The coordination of care in bladder cancer remains a challenge for patients and physicians alike. We believe by utilizing a multidisciplinary approach, efficiency and quality of care increases. National database studies have reported overall utilization of neoadjuvant chemotherapy over the past 10 years, with most recent rates ranging from 14.8-20.9%. Our utilization of neoadjuvant therapy is notably higher at 77%, which also includes early adaptation of NAI in patients deemed ineligible for neoadjuvant NAC. Further studies are needed to examine a contemporary control population outside the multidisciplinary setting, however the above outcomes provide a basis for the integration of care and its positive outcomes in quality improvement.

Urothelial Cancers with Small Cell Variant Histology Have Confirmed High Tumor Mutational Burden, Frequent TP53 and RB Mutations, and a Unique Gene Expression Profile

Although predominantly urothelial, some bladder cancer and upper tract urothelial cancer (BC/UTUC) harbor histologic variants. Small cell BC (SCBC) variants comprised ˜5% of The Cancer Genome Atlas BC cohort, with a poor prognosis. We describe genomic profiles of BC/UTUC with small cell/neuroendocrine features identified in the Foundation Medicine database from June 2012 to September 2018. Of 3368 BC/UTUC samples, 3.92% (132) harbored small cell/neuroendocrine features by immunohistochemistry. Mutations were noted in: TP53 (92%), RB1 (75%), combined TP53/RB1 (72%), and TERT promoter (68%). Of the samples, 6.5% had TMB ≥ 10 mutations/Mb. RNA expression profiling of 24 pure SCBC and 51 urothelial BC (UBC) muscle-invasive samples evaluated from a separate cohort revealed a large number of differentially expressed genes with suppression of several inflammatory pathways in SCBC compared with UBC. This largest reported SCBC dataset to date confirms enrichment of signatures in SCBC similar to small cell lung cancer and describes unique gene expression compared with UBC. These findings may explain aggressive SCBC phenotype. PATIENT SUMMARY: Small cell bladder cancer (SCBC) is an aggressive subtype that microscopically resembles aggressive small cell lung cancer (SCLC). This study confirms that SCBC shares DNA changes similar to SCLC and that SCBC expresses many genes that urothelial bladder cancer does not, possibly explaining aggressive SCBC activity.

Radium-223 mechanism of action: implications for use in treatment combinations

The targeted alpha therapy radium-223 (223Ra) can prolong survival in men with castration-resistant prostate cancer (CRPC) who have symptomatic bone metastases and no known visceral metastases. Preclinical studies demonstrate that 223Ra preferentially incorporates into newly formed bone matrix within osteoblastic metastatic lesions. The emitted high-energy alpha particles induce DNA double-strand breaks that might be irreparable and lead to cell death in nearby exposed tumour cells, osteoblasts and osteoclasts. Consequently, tumour growth and abnormal bone formation are inhibited by these direct effects and by the disruption of positive-feedback loops between tumour cells and the bone microenvironment. 223Ra might also modulate immune responses within the bone. The clinical utility of 223Ra has encouraged the development of other anticancer targeted alpha therapies. A thorough understanding of the mechanism of action could inform the design of new combinatorial treatment strategies that might be more efficacious than monotherapy. On the basis of the current mechanistic knowledge and potential clinical benefits, combination therapies of 223Ra with microtubule-stabilizing cytotoxic drugs and agents targeting the androgen receptor axis, immune checkpoint receptors or DNA damage response proteins are being explored in patients with CRPC and metastatic bone disease.

Impact of in-house specialty pharmacy on access to novel androgen axis inhibitors in men with advanced prostate cancer

132

Background: Novel androgen axis inhibitors are standard of care treatments in advanced prostate cancer. The billed amounts for these medications are often very high, which may create significant financial toxicity for patients and lead to delays in treatment. Our institution implemented an in-house specialty pharmacy in 2014, that provides these medications and evaluates copay assistance options for all patients. We evaluated the program’s impact on out of pocket cost (OOP) and turnaround time (TAT). Methods: We reviewed available internal specialty pharmacy records to identify prescriptions for abiraterone or enzalutamide filled between 1/1/17 and 12/31/18. Payments were stratified by primary payment (amount reimbursed by the patient’s prescription plan based on the benefit’s design) and copayment assistance. Turnaround times (TAT) in business days were stratified by prescriptions requiring intervention (prior authorization, copayment assistance, or insufficient inventory) and clean prescriptions (those requiring no intervention). Results: One thousand for hundred seventeen prescriptions for 175 unique patients requiring abiraterone (n = 869, 61.3%) or enzalutamide (n = 548, 38.7%) were filled through the institution’s specialty pharmacy. The average amount paid by primary payer was $9,492.96 for a 30 day supply (range: $3,382.48-$12,939.84). Average quoted copay was $577.53 (range $3.08-$10,560.39). 64% of patients received copayment assistance. Average OOP cost per prescription after co-pay assistance was $100.83 (range $0-$8556.64). Three patients declined treatment due to cost (1.7% of overall). Average TAT was 2.98 days for clean prescriptions and 3.36 days for prescriptions needing intervention (p = 0.055). Conclusions: OOP cost varied significantly based on plan design and copayment assistance eligibility. The majority of patients received copayment assistance, which markedly reduced OOP cost. Cost rarely precluded access to treatment. TAT was not significantly prolonged for prescriptions requiring intervention. Further studies to determine impact of pharmacy type on access to specialty medications are indicated.

Accelerating advanced precision medicine through a harmonized data exchange platform and research consortium (PMEC)

6557

Background: Clinico-genomic data sharing is consistently identified by the global oncology community as a critical requirement to accelerate the discovery and development of new targeted therapies. However, lack of effective collaborative models, fragmented and lengthy legal contracting processes, paucity of funding, and inadequate technological platforms have historically been obstacles for effective data sharing. Methods: In 2015, 10 US academic medical centers (AMC) and Foundation Medicine Inc. (FMI) formed PMEC. Feasibility assessments included creation of a master agreement across sites and willingness to use a central IRB. Oversight and research steering committees were created within the consortium. Through a centralized, secure web-based platform, FoundationInsight, we combined and shared de-identified, harmonized comprehensive FoundationOne genomic profiling data. Research proposals mining this data warehouse are invited quarterly from participant AMCs and peer-reviewed; approved studies are executed at all sites. Results: All 10 AMCs collaborated to execute a master registry participation agreement, followed by a master IRB protocol (New England IRB # 120180008), subsequently approved by individual site IRBs. Since its launch, the PMEC database has grown, on average, 60% per year, to now house over 14,000 cases. The shared dataset covers all tumor types (most commonly lung [17.2%], gastrointestinal [13.8%] and breast [9.2%]), encompasses genomic alterations in >300 genes, and reports relevant supplementary data such as tumor mutation burden and microsatellite instability status. To date, 15 studies have been proposed and evaluated using this platform, with 2 projects currently approved and in progress. Conclusions: We demonstrated the feasibility of creating a collaborative academic consortium that facilitates data sharing and potential discovery efforts in oncology. Technology solutions can accelerate the ability of AMCs, in partnership with central labs, to share and harmonize data to advance precision medicine. This approach lays the groundwork for conducting prospective, biomarker-enriched clinical trials among participating AMCs.

A phase Ib/II study of niraparib combination therapies for the treatment of metastatic castration-resistant prostate cancer (NCT03431350)

TPS5087

Background: Assessing multiple therapies in a single clinical trial can facilitate the rapid identification of new agents for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC). Niraparib (Nirap) is a highly selective PARP inhibitor, with potent activity against PARP-1 and PARP-2 deoxyribonucleic acid (DNA)-repair polymerases. PARP inhibition may be especially lethal in tumor cells with genetic DNA damage response deficits (DRD). Based on promising preclinical and clinical data, this study is designed as a master protocol with nirap as a backbone therapy. Combination 1 assesses the safety and efficacy of nirap plus JNJ-63723283 (JNJ-283), an anti-PD-1 monoclonal antibody. Combination 2 assesses nirap plus abiraterone acetate and prednisone (AA-P). Methods: This multicenter, global, open-label study is currently open at 18 sites in 5 countries of the planned XX sites, and is enrolling patients with mCRPC who have progressed on ≥1 androgen-receptor targeted therapy for mCRPC. Enrollment at time of abstract submission was 25 for combination 1. When combined with AA-P, the RP2D has been determined to be nirap 200 mg. The recommended phase-2 dose (RP2D) of nirap plus JNJ-283 was determined in Part 1 based on the incidence of specified adverse events and PK data to be 480 mg every 4 weeks. For Part 2 of the study, patients are assigned to receive oral niraparib daily plus JNJ-283 infusions once every four weeks until disease progression, unacceptable toxicity, death, study termination. Part 2 is described in the table. Clinical trial information: NCT03431350. [Table: see text]

External validation of a prognostic model for overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC)

5022

Background: We have previously developed and externally validated a prognostic model of OS in men with mCRPC treated with docetaxel (D), which included eight predictors: opioid analgesic use, ECOG performance status, albumin, disease site, LDH, hemoglobin, PSA, and alkaline phosphatase. We have used this model to develop prognostic risk groups. We sought to externally validate this model in a broader group of men with mCRPC and in specific subgroups (White, Black, Asian patients, different age groups) and to validate the two and three prognostic risk groups in this large dataset. Methods: Data from 5,790 mCRPC men randomized on 5 phase III trials were utilized to validate the prognostic model of OS: D +/- zibotentan (ENTHUSE), D +/- lenalidomide (MAINSAIL), D +/- dasatinib (READY), D+/- custirsen (SYNERGY), and tasquinimod/placebo)). We applied the estimated parameters from the prognostic model to each of the five data sets and computed a risk score. We assessed the predictive performance of the model by computing the time-dependent area under the receiver operating characteristic curve (tAUC) and validated the two-risk (low, high) and three-risk prognostic risk groups (low, intermediate, high) that were defined by the model. Results: The tAUC for the different groups is presented in the table. Race, age, and treatment subsets had similar results. For the two prognostic risk groups, the median OS in the low and high groups were 27.6 months (95% CI = 26.6-28.7) and 13.8 months (95% CI = 13.3-14.4). For the three prognostic risk group, median OS in the low, intermediate and high groups were 29.7 months (95% CI = 28.3-31.4), 19.0 month (95% CI = 18.3-20.4) and 12.1 months (95% CI = 11.5-12.9), respectively. Conclusions: This prognostic model for OS in men with mCRPC has been validated in a larger dataset, yields similar results across race, age and treatment groups. The model is robust and can be used to identify prognostic risk groups of patients for stratification and enrichment trials. Clinical trial information: NCT00626548. [Table: see text]

FIERCE-22: Clinical activity of vofatamab (V) a FGFR3 selective inhibitor in combination with pembrolizumab (P) in WT metastatic urothelial carcinoma, preliminary analysis

4511

Background: Patients (pts) with mUC who have failed platinum-based chemotherapy have a poor prognosis. Reported response rates to immune checkpoint inhibitors (ICI) are approximately 20%. 20% of pts with mUC harbor FGFR3 mutations or fusions (M/F), which may result in lower sensitivity to ICI. V (B-701) is a fully human monoclonal antibody against FGFR3 that blocks activation of both the wildtype and genetically activated receptor. This is a Phase 1b/2 study designed to evaluate V monotherapy window followed in combination of V with P(VP) (NCT03123055). Methods: This trial enrolled mUC pts with failure to ≥ 1 prior line of chemotherapy or recurrence ≤ 12 months of (neo)adjuvant chemotherapy, measurable disease and ECOG <2. Treatment consisted of v at 25 mg/kg alone for 2 week monotherapy window followed by combination with P 200 mg q3w.during the V window paired tumor biopsy were obtained. Efficacy was assessed by investigators (RECIST 1.1). Primary objectives were safety and activity [ORR]). Results: 35 pts have received treatment (Ph1b:8, WT:20, M/F+: 7). WT patients were unselected for PD-1 status, predominately male (55%) white (95%), all had received at least 1 line of prior chemo and 60% had Bellmunt scores of > 1. The safety profile is consistent with previously reported data for P. TEAE occurring in >20% of patients were nausea, anemia, diarrhea and fatigue. Six WT patients (30%) had responses (4 confirmed responses, 1 unconfirmed), and an additional patient with an iRECIST response. Responses occurred at a median of 3.5 months. At 4+ months of follow up, 13(65%) remain on treatment @ a median of 8 cycles (range: 1-13). At 5+ months the median PFS has not been reached. Conclusions: VP combination therapy is well tolerated with an encouraging ORR and prolonged PFS in the WT cohort; greater than one would anticipate from P alone based upon historical data. We will be reporting 9+ month preliminary PFS/OS and updated OOR/DOR data. Clinical trial information: NCT03123055.

Interim results from a phase 2 study of olaparib (without ADT) in men with biochemically-recurrent prostate cancer after prostatectomy, with integrated biomarker analysis

5045

Background: Pts with biochemically-recurrent (BCR) prostate cancer after local therapy with a PSA doubling time (PSADT) of ≤6 mo are likely to develop metastases and death from their disease. We hypothesized that the PARP inhibitor olaparib would be effective as a non-hormonal therapy for biomarker-unselected pts with BCR after prostatectomy, the first study of PARP inhibition in the hormone-sensitive setting. We report pre-specified interim results from the first stage of the trial. Methods: This investigator-initiated multicenter study (NCT03047135) enrolled pts with non-metastatic BCR after prostatectomy, with a PSADT of ≤6 mo. PSA had to be ≥1.0 ng/mL, with T ≥150 ng/dL. Pts received olaparib 300 mg twice daily (without ADT), until a doubling of their PSA or metastatic progression. The primary endpoint was confirmed ≥50% PSA decline (PSA50 response). Secondary endpoints included safety, minor PSA response (1-50% reduction), and PSA progression-free survival. Integrated biomarker analyses included somatic DNA sequencing, RNA expression analysis and IHC for DNA damage markers, using prostatectomy specimens. The study was designed to enroll a biomarker-unselected population using a staged-adaptive design, with up to 50 pts. In the first stage, ≥3 PSA50 responses out of 20 pts were required to proceed to the second stage; otherwise enrichment with biomarker-selected pts would occur. Results: Between 5/2017 and 11/2018, 20 men (median age, 65) enrolled in the first stage, with a median follow-up of 6 (range, 3-16) mo. Median PSADT was 3.1 mo, and 55% had Gleason ≥8 cancers. Seven men (35%) had BRCA2/ATM mutations. Three men (15%) had PSA50 responses (all had BRCA2 muts – 2 had complete PSA responses), and 4 other men (20%) had minor PSA responses. Median PSA progression-free survival was greater in men with vs. without BRCA2/ATM muts (9 vs. 4 mo; P= 0.02). Common toxicities of olaparib included fatigue, nausea, anemia and leukopenia; 2 men required a dose reduction. Conclusions: Olaparib (without ADT) was tolerable and showed activity in hormone-sensitive BCR prostate cancer, especially in men with BRCA2 muts. Second-stage enrolment is ongoing. Clinical trial information: NCT03047135.

PSA decline and objective response rates in White (W), Black (B), and Asian men with metastatic castration-resistant prostate cancer (mCRPC)

5021

Background: We have shown previously in multivariable analysis that AA men had 19% lower risk of death than C men with metastatic castration resistant prostate cancer (mCRPC) treated with a docetaxel (D) and prednisone (P) based regimen. The primary goal of this analysis was to compare ≥50%PSA decline and objective response rate (ORR) in C men, AA men, and Asian men with mCRPC treated with a DP based regimen. Methods: Individual patient data from 8,151 mCRPC men randomized on eight phase III trials to a D containing regimen were combined. Race used in the analysis was based on self-report. The endpoints were ≥50% PSA decline from baseline defined by the PSA working group 2 and ORR (defined as complete or partial response). The logistic regression model was employed to assess the prognostic importance of race in predicting ≥50% PSA decline and ORR adjusting for treatment arm, performance status, and site of metastases. Results: Of 8,151, 7,687 (94%) patients had evaluable PSA data. Of 7,687 men, 6,535 (85%) were W, 445 (6%) were B, 395 (5%) were Asian and 312 (4%) had race unspecified. Men with race unspecified were excluded from the analysis, leaving 7,375 men. Percentage of patients who experienced PSA decline from baseline were: 64%, 58% and 62% in W, B and Asian men, respectively. In multivariable analysis adjusting for risk factors, the pooled odds ratios for PSA decline for AA vs. W were 0.9 (95% CI = 0.7-1.1, p = 0.16) and 1.0 (95% CI = 0.8-1.2, p = 0.92) for Asian vs. W. In 2,760 patients with measurable disease, the percentage of patients who had ORR were: 39%, 31% and 34% in W, B and Asian men, respectively. In multivariable analysis, the pooled odds ratios for ORR were 1.0 (95% CI = 0.7-1.4) for B vs. W and 0.9 (95% CI = 0.6-1.4) for Asian vs. W. Conclusions: There were no differences in PSA decline and ORR outcomes in W, B, or Asian men with mCRPC enrolled on these phase III clinical trials with DP. Clinical trial information: NCT00110214.