TRIUMPH: phase II trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer harboring germline homologous recombination repair gene mutations.

BACKGROUND: The activity of PARP inhibitors (PARPi) in patients with homologous recombination repair (HRR) mutations and metastatic castration-resistant prostate cancer has been established. We hypothesized that the benefit of PARPi can be maintained in the absence of androgen deprivation therapy (ADT) in an HRR-mutated population. We report the results of a phase II clinical trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer (mHSPC). METHODS: This was a multi-center, single-arm phase II trial (NCT03413995) for patients with asymptomatic, mHSPC. Patients were required to have a pathogenic germline mutation in an HRR gene for eligibility. All patients received rucaparib 600 mg by mouth twice daily, without androgen deprivation. The primary endpoint was a confirmed PSA50 response rate. RESULTS: Twelve patients were enrolled, 7 with a BRCA1/2 mutation and 5 with a CHEK2 mutation. The confirmed PSA50 response rate to rucaparib was 41.7% (N = 5/12, 95% CI: 15.2-72.3%, one-sided P = .81 against the 50% null), which did not meet the pre-specified efficacy boundary to enroll additional patients. In patients with measurable disease, the objective response rate was 60% (N = 3/5), all with a BRCA2 mutation. The median radiographic progression-free survival on rucaparib was estimated at 12.0 months (95% CI: 8.0-NR months). The majority of adverse events were grade ≤2, and expected. CONCLUSION: Rucaparib can induce clinical responses in a biomarker-selected metastatic prostate cancer population without concurrent ADT. However, the pre-specified efficacy threshold was not met, and enrolment was truncated. Although durable responses were observed in a subset of patients, further study of PARPi treatment without ADT in mHSPC is unlikely to change clinical practice.

Association of PARP inhibitor treatment on the prevalence and progression of clonal hematopoiesis in patients with advanced prostate cancer.

BACKGROUND: Poly ADP-ribose polymerase (PARP) inhibitors are approved for the treatment of some men with advanced prostate cancer. Rare but serious side effects include myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). The impact of PARP inhibitors on clonal hematopoiesis (CH), a potential precursor lesion associated with MDS and AML, is incompletely understood in prostate cancer. We hypothesized that PARP inhibitors would increase CH prevalence and abundance. METHODS: We prospectively enrolled participants with advanced prostate cancer treated with PARP inhibitors. The presence of CH was assessed from leukocytes using an ultra-deep error-corrected dual unique molecular identifiers sequencing method targeting 49 genes most commonly mutated in CH and myeloid malignancies. Variant allele frequencies (VAF) of ≥0.5% were considered clinically significant. Blood samples were collected before and after PARP inhibitor treatment. RESULTS: Ten men were enrolled; mean age of 67 years. Six patients had Gleason 7 disease, and four had Gleason ≥8 disease at diagnosis. Nine had localized disease at diagnosis, and eight had prior treatment with radiation. The mean time between pre- and post-treatment blood samples was 11 months (range 2.6-31 months). Six patients (60%) had CH identified prior to PARP inhibitor treatment, three with multiple clones. Of 11 CH clones identified in follow-up, 5 (45%) appeared or increased after treatment. DNMT3A, TET2, and PPM1D were the most common CH alterations observed. The largest post-treatment increase involved the PPM1D gene. CONCLUSION: CH alterations are frequently found after treatment with PARP inhibitors in patients with prostate cancer and this may be one mechanism by which PARP inhibitors lead to increased risk of MDS/AML.

Bipolar androgen therapy plus nivolumab for patients with metastatic castration-resistant prostate cancer: the COMBAT phase II trial.

Cyclic high-dose testosterone administration, known as bipolar androgen therapy (BAT), is a treatment strategy for patients with metastatic castration-resistant prostate cancer (mCRPC). Here, we report the results of a multicenter, single arm Phase 2 study (NCT03554317) enrolling 45 patients with heavily pretreated mCRPC who received BAT (testosterone cypionate, 400 mg intramuscularly every 28 days) with the addition of nivolumab (480 mg intravenously every 28 days) following three cycles of BAT monotherapy. The primary endpoint of a confirmed PSA50 response rate was met and estimated at 40% (N = 18/45, 95% CI: 25.7-55.7%, P = 0.02 one-sided against the 25% null hypothesis). Sixteen of the PSA50 responses were achieved before the addition of nivolumab. Secondary endpoints included objective response rate (ORR), median PSA progression-free survival, radiographic progression-free survival (rPFS), overall survival (OS), and safety/tolerability. The ORR was 24% (N = 10/42). Three of the objective responses occurred following the addition of nivolumab. After a median follow-up of 17.9 months, the median rPFS was 5.6 (95% CI: 5.4-6.8) months, and median OS was 24.4 (95% CI: 17.6-31.1) months. BAT/nivolumab was well tolerated, resulting in only five (11%) drug related, grade-3 adverse events. In a predefined exploratory analysis, clinical response rates correlated with increased baseline levels of intratumoral PD-1 + T cells. In paired metastatic tumor biopsies, BAT induced pro-inflammatory gene expression changes that were restricted to patients achieving a clinical response. These data suggest that BAT may augment antitumor immune responses that are further potentiated by immune checkpoint blockade.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression.

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type-specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by 2 orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Vascular Expression of Prostate-specific Membrane Antigen (PSMA) in MiTF Family Translocation Renal Cell Carcinoma and Related Neoplasms.

Multiple studies have demonstrated prostate-specific membrane antigen (PSMA) expression in the neo-vasculature of non-prostate tumors including clear cell renal cell carcinoma (ccRCC). However, PSMA expression in rare renal tumors including MiTF family translocation renal cell carcinoma has not been previously characterized. We examined PSMA expression by immunohistochemistry in a series of MiTF family translocation renal cell carcinomas as well as in several genetically related tumors including alveolar soft part sarcoma and PEComas with TFE3 rearrangements. PSMA expression was also studied in several cases of ccRCC and papillary RCC. Overall, PSMA immunohistochemistry was performed in 61 samples from 58 patients. Vascular PSMA expression was seen with the highest frequency in ccRCC [88% (14/16)] (38% focal, 50% diffuse). Translocation RCC (tRCC) demonstrated the second highest frequency of PSMA expression [71% (22/28)] (57% focal, 14% diffuse), followed by alveolar soft part sarcoma [50% (4/8)] (38% focal, 12% diffuse). No PSMA expression was seen in PEComas with TFE3 rearrangement (0/3) or papillary RCC (0/6). PSMA expression was only present in tumor-associated neo-vasculature. A patient with oligometastatic tRCC underwent 68 Ga-PSMA-11 PET imaging which detected multiple putative metastatic lesions not detected on conventional computed tomography imaging performed 2 weeks prior, supporting the potential utility of PSMA imaging in tRCC. These findings have potential implications for the utility of PSMA guided diagnostic and therapeutic agents in both common and uncommon renal cell carcinoma subtypes as well as genetically related mesenchymal neoplasms.

Predicting Prostate Cancer Molecular Subtype With Deep Learning on Histopathologic Images.

Microscopic examination of prostate cancer has failed to reveal a reproducible association between molecular and morphologic features. However, deep-learning algorithms trained on hematoxylin and eosin (H&E)-stained whole slide images (WSI) may outperform the human eye and help to screen for clinically-relevant genomic alterations. We created deep-learning algorithms to identify prostate tumors with underlying ETS-related gene (ERG) fusions or PTEN deletions using the following 4 stages: (1) automated tumor identification, (2) feature representation learning, (3) classification, and (4) explainability map generation. A novel transformer-based hierarchical architecture was trained on a single representative WSI of the dominant tumor nodule from a radical prostatectomy (RP) cohort with known ERG/PTEN status (n = 224 and n = 205, respectively). Two distinct vision transformer-based networks were used for feature extraction, and a distinct transformer-based model was used for classification. The ERG algorithm performance was validated across 3 RP cohorts, including 64 WSI from the pretraining cohort (AUC, 0.91) and 248 and 375 WSI from 2 independent RP cohorts (AUC, 0.86 and 0.89, respectively). In addition, we tested the ERG algorithm performance in 2 needle biopsy cohorts comprised of 179 and 148 WSI (AUC, 0.78 and 0.80, respectively). Focusing on cases with homogeneous (clonal) PTEN status, PTEN algorithm performance was assessed using 50 WSI reserved from the pretraining cohort (AUC, 0.81), 201 and 337 WSI from 2 independent RP cohorts (AUC, 0.72 and 0.80, respectively), and 151 WSI from a needle biopsy cohort (AUC, 0.75). For explainability, the PTEN algorithm was also applied to 19 WSI with heterogeneous (subclonal) PTEN loss, where the percentage tumor area with predicted PTEN loss correlated with that based on immunohistochemistry (r = 0.58, P = .0097). These deep-learning algorithms to predict ERG/PTEN status prove that H&E images can be used to screen for underlying genomic alterations in prostate cancer.

Test-retest repeatability of organ uptake on PSMA-targeted 18 F-DCFPyL PET/CT in patients with prostate cancer.

OBJECTIVES: We evaluated 18 F-DCFPyL test-retest repeatability of uptake in normal organs. METHODS: Twenty-two prostate cancer (PC) patients underwent two 18 F-DCFPyL PET scans within 7 days within a prospective clinical trial (NCT03793543). In both PET scans, uptake in normal organs (kidneys, spleen, liver, and salivary and lacrimal glands) was quantified. Repeatability was determined by using within-subject coefficient of variation (wCOV), with lower values indicating improved repeatability. RESULTS: For SUVmean , repeatability was high for kidneys, spleen, liver, and parotid glands (wCOV, range: 9.0%-14.3%) and lower for lacrimal (23.9%) and submandibular glands (12.4%). For SUVmax , however, the lacrimal (14.4%) and submandibular glands (6.9%) achieved higher repeatability, while for large organs (kidneys, liver, spleen, and parotid glands), repeatability was low (range: 14.1%-45.2%). CONCLUSION: We found acceptable repeatability of uptake on 18 F-DCFPyL PET for normal organs, in particular for SUVmean in the liver or parotid glands. This may have implications for both PSMA-targeted imaging and treatment, as patient selection for radioligand therapy and standardized frameworks for scan interpretation (PROMISE, E-PSMA) rely on uptake in those reference organs.

Safety and clinical efficacy of immune checkpoint inhibition and stereotactic body radiotherapy in patients with spine metastasis.

OBJECTIVE: Immunotherapy, particularly immune checkpoint inhibitors (ICIs), has revolutionized the treatment of patients with many tumor histologies. Simultaneously, stereotactic body radiotherapy (SBRT) provides excellent local control (LC) and plays an important role in the management of spine metastasis. Promising preclinical work suggests the potential therapeutic benefit of combining SBRT with ICI therapy, but the safety profile of combined therapy is unclear. This study aimed to evaluate the toxicity profile associated with ICI in patients receiving SBRT and, secondarily, whether ICI administration sequence with respect to SBRT affects LC or overall survival (OS) outcomes. METHODS: The authors retrospectively reviewed patients with spine metastasis treated with SBRT at an academic center. Patients who received ICI at any point during their disease course were compared to those with the same primary tumor types who did not receive ICI by using Cox proportional hazards analyses. Primary outcomes were long-term sequelae, including radiation-induced spinal cord myelopathy, esophageal stricture, and bowel obstruction. Secondarily, models were created to evaluate OS and LC in the cohort. RESULTS: Two hundred forty patients who received SBRT to 299 spine metastases were included in this study. The most common primary tumor types were non-small cell lung cancer (n = 59 [24.6%]) and renal cell carcinoma (n = 55 [22.9%]). One hundred eight patients received at least 1 dose of ICI, with the most common regimen being single-agent anti-PD-1 (n = 80 [74.1%]), followed by combination CTLA-4/PD-1 inhibitors (n = 19 [17.6%]). Three patients experienced long-term radiation-induced sequelae: 2 had esophageal stricture and 1 had bowel obstruction. No patients developed radiation-induced myelopathy. There was no association between receipt of ICI and development of any of these adverse events (p > 0.9). Similarly, ICI was not significantly associated with either LC (p = 0.3) or OS (p = 0.6). In the entire cohort, patients who received ICI prior to beginning SBRT had worse median survival, but ICI sequence with respect to SBRT was not significantly prognostic of either LC (p > 0.3) or OS (p > 0.07); instead, baseline performance status was most predictive of OS (HR 1.38, 95% CI 1.07-1.78, p = 0.012). CONCLUSIONS: Treatment regimens that combine ICIs before, concurrent with, and after SBRT for spine metastases are safe, with minimal risk for increased rates of long-term toxicity.

Bipolar Androgen Therapy Followed by Androgen Receptor Inhibition as Sequential Therapy for Prostate Cancer.

Inhibition of androgen receptor (AR) signaling has been the mainstay of treatment of advanced prostate cancer (PCa) for the past 80 years. Combination and sequential AR-inhibiting therapies are highly effective palliative therapy, but they are not curative. All patients eventually develop resistance to primary castrating therapy [ie, castration-resistant PCa (CRPC)]. At this point, they are treated with subsequent lines of secondary AR inhibitory therapies. However, resistance to these agents also develops and patients progress to a state we have termed complete androgen inhibition-resistant PCa. This phase of the disease is associated with poor prognosis. At this point, treatment shifts to non-hormonal cytotoxic therapies (eg, chemotherapy and radiopharmaceuticals). However, the majority of PCas remain addicted to signaling through AR throughout the course of the disease. Resistant PCa cells adaptively upregulate AR activity, despite castration and AR inhibitors, via mechanisms such as AR overexpression, gene amplification, mutation, and expression of ligand-independent variants to permit sustained liganded and non-liganded AR signaling. Studies dating back nearly 30 years indicate that high expression of AR induced by prolonged castration becomes a vulnerability of CRPC cells in vitro and in mouse xenografts to supraphysiologic androgen (SPA), which induces cell death and growth arrest in this context. Based on these studies, we developed a counterintuitive treatment called bipolar androgen therapy (BAT) for patients with CRPC, in which SPA is administered intermittently to result in cycling of serum testosterone from the polar extremes of supraphysiologic to near-castrate levels. This rapid cycling is intended to disrupt the adaptive of AR regulation associated with chronic exposure to high or low levels of testosterone, while simultaneously targeting the spectrum of AR expression present in heterogeneous CRPC tumors. We have now tested BAT in >250 patients with CRPC. Here we present a review of these clinical studies, which have demonstrated collectively that BAT can be safely given to men with CRPC, improves quality of life, and produces therapeutic responses in ~30% of patients. As expected, resistance to BAT is associated with adaptive downregulation of AR expression. Intriguingly, this downregulation is associated with restoration of sensitivity to subsequent AR inhibitor therapies.

Multi-timepoint imaging with PSMA-targeted [18F]F-Florastamin PET/CT: lesion detection and comparison to conventional imaging.

OBJECTIVE: The aims of this study were to investigate the utility of [18F]F-Florastamin, a novel prostate-specific membrane antigen (PSMA)-targeted PET radiotracer with facile radiochemistry, relative to the conventional imaging for the detection of sties of disease and evaluate the effect of multi-timepoint imaging with [18F]F-Florastamin PET on lesion detectability. METHODS: Eight prostate cancer patients with known or suspected recurrence who underwent [18F]F-Florastamin PET/CT at 1-h and 2-h imaging time-points were included in this prospective pilot study. [18F]F-Florastamin PET images were interpreted visually and quantitatively at both time points and compared with CIM. RESULTS: [18F]F-Florastamin PET was superior to CT in the detection of active osseous metastases and small-sized metastatic lymph nodes that do not fall under the anatomic imaging size criteria for metastasis. Multi-timepoint imaging showed a significant reduction in the blood pool, bone marrow and muscular uptake, and increase in liver uptake over time. There is a significant improvement in tumor-to-background ratio (TBR) at the 2-h imaging time-point (P = 0.04). The mean percentage change in TBR at 2-h was 21% (SD = 0.31). CONCLUSIONS: [18F]F-Florastamin is a promising new radioligand for PSMA-targeted PET with suitable lesion detectability and high TBR at both time points.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression.

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Role of bromodomain and extraterminal (BET) proteins in prostate cancer.

INTRODUCTION: The bromodomain and extraterminal (BET) family of proteins are epigenetic readers of acetylated histones and are critical activators of oncogenic networks across many cancers. Therapeutic targeting of BET proteins has been an attractive area of clinical development for metastatic castration-resistant prostate cancer. In recent years, many structurally diverse BET inhibitors have been discovered and tested. Preclinical studies have demonstrated significant antiproliferative activity of BET inhibitors against prostate cancer. However, their clinical success as monotherapies has been limited by treatment-associated toxicities, primary and acquired drug resistance, and a lack of predictive biomarkers of benefit. AREAS COVERED: This review provides an overview of advancements in BET inhibitor design, preclinical research, and conclusions from clinical trials in prostate cancer. We speculate on incorporating BET inhibitors into combination regimens with other agents to improve the therapeutic index of BET inhibition in treating prostate cancer. EXPERT OPINION: The therapeutic potential of BET inhibitors for prostate cancer has been demonstrated in preclinical studies. However, further research is needed to identify biomarkers that can predict sensitivity to BET inhibitors and to develop novel, highly selective inhibitors to reduce toxicities. Finally, BET inhibitors are likely to hold the most clinical potential in combination with other agents.

Lack of repeatability of radiomic features derived from PET scans: Results from a 18 F-DCFPyL test-retest cohort.

OBJECTIVES: PET-based radiomic metrics are increasingly utilized as predictive image biomarkers. However, the repeatability of radiomic features on PET has not been assessed in a test-retest setting. The prostate-specific membrane antigen-targeted compound 18 F-DCFPyL is a high-affinity, high-contrast PET agent that we utilized in a test-retest cohort of men with metastatic prostate cancer (PC). METHODS: Data of 21 patients enrolled in a prospective clinical trial with histologically proven PC underwent two 18 F-DCFPyL PET scans within 7 days, using identical acquisition and reconstruction parameters. Sites of disease were segmented and a set of 29 different radiomic parameters were assessed on both scans. We determined repeatability of quantification by using Pearson's correlations, within-subject coefficient of variation (wCOV), and Bland-Altman analysis. RESULTS: In total, 230 lesions (177 bone, 38 lymph nodes, 15 others) were assessed on both scans. For all investigated radiomic features, a broad range of inter-scan correlation was found (r, 0.07-0.95), with acceptable reproducibility for entropy and homogeneity (wCOV, 16.0% and 12.7%, respectively). On Bland-Altman analysis, no systematic increase or decrease between the scans was observed for either parameter (±1.96 SD: 1.07/-1.30, 0.23/-0.18, respectively). The remaining 27 tested radiomic metrics, however, achieved unacceptable high wCOV (≥21.7%). CONCLUSION: Many common radiomic features derived from a test-retest PET study had poor repeatability. Only Entropy and homogeneity achieved good repeatability, supporting the notion that those image biomarkers may be incorporated in future clinical trials. Those radiomic features based on high frequency aspects of images appear to lack the repeatability on PET to justify further study.

Phase II Randomized Study of Salvage Radiation Therapy Plus Enzalutamide or Placebo for High-Risk Prostate-Specific Antigen Recurrent Prostate Cancer After Radical Prostatectomy: The SALV-ENZA Trial.

PURPOSE: We sought to investigate whether enzalutamide (ENZA), without concurrent androgen deprivation therapy, increases freedom from prostate-specific antigen (PSA) progression (FFPP) when combined with salvage radiation therapy (SRT) in men with recurrent prostate cancer after radical prostatectomy (RP). PATIENTS AND METHODS: Men with biochemically recurrent prostate cancer after RP were enrolled into a randomized, double-blind, phase II, placebo-controlled, multicenter study of SRT plus ENZA or placebo (ClinicalTrials.gov identifier: NCT02203695). Random assignment (1:1) was stratified by center, surgical margin status (R0 v R1), PSA before salvage treatment (PSA ≥ 0.5 v < 0.5 ng/mL), and pathologic Gleason sum (7 v 8-10). Patients were assigned to receive either ENZA 160 mg once daily or matching placebo for 6 months. After 2 months of study drug therapy, external-beam radiation (66.6-70.2 Gy) was administered to the prostate bed (no pelvic nodes). The primary end point was FFPP in the intention-to-treat population. Secondary end points were time to local recurrence within the radiation field, metastasis-free survival, and safety as determined by frequency and severity of adverse events. RESULTS: Eighty-six (86) patients were randomly assigned, with a median follow-up of 34 (range, 0-52) months. Trial arms were well balanced. The median pre-SRT PSA was 0.3 (range, 0.06-4.6) ng/mL, 56 of 86 patients (65%) had extraprostatic disease (pT3), 39 of 86 (45%) had a Gleason sum of 8-10, and 43 of 86 (50%) had positive surgical margins (R1). FFPP was significantly improved with ENZA versus placebo (hazard ratio [HR], 0.42; 95% CI, 0.19 to 0.92; P = .031), and 2-year FFPP was 84% versus 66%, respectively. Subgroup analyses demonstrated differential benefit of ENZA in men with pT3 (HR, 0.22; 95% CI, 0.07 to 0.69) versus pT2 disease (HR, 1.54; 95% CI, 0.43 to 5.47; Pinteraction = .019) and R1 (HR, 0.14; 95% CI, 0.03 to 0.64) versus R0 disease (HR, 1.00; 95% CI, 0.36 to 2.76; Pinteraction = .023). There were insufficient secondary end point events for analysis. The most common adverse events were grade 1-2 fatigue (65% ENZA v 53% placebo) and urinary frequency (40% ENZA v 49% placebo). CONCLUSION: SRT plus ENZA monotherapy for 6 months in men with PSA-recurrent high-risk prostate cancer after RP is safe and delays PSA progression relative to SRT alone. The impact of ENZA on distant metastasis or survival is unknown at this time.

Androgen receptor activity in prostate cancer dictates efficacy of bipolar androgen therapy through MYC.

Testosterone is the canonical growth factor of prostate cancer but can paradoxically suppress its growth when present at supraphysiological levels. We have previously demonstrated that the cyclical administration of supraphysiological androgen (SPA), termed bipolar androgen therapy (BAT), can result in tumor regression and clinical benefit for patients with castration-resistant prostate cancer. However, predictors and mechanisms of response and resistance have been ill defined. Here, we show that growth inhibition of prostate cancer models by SPA required high androgen receptor (AR) activity and were driven in part by downregulation of MYC. Using matched sequential patient biopsies, we show that high pretreatment AR activity predicted downregulation of MYC, improved clinical response, and prolonged progression-free and overall survival for patients on BAT. BAT induced strong downregulation of AR in all patients, which is shown to be a primary mechanism of acquired resistance to SPA. Acquired resistance was overcome by alternating SPA with the AR inhibitor enzalutamide, which induced adaptive upregulation of AR and resensitized prostate cancer to SPA. This work identifies high AR activity as a predictive biomarker of response to BAT and supports a treatment paradigm for prostate cancer involving alternating between AR inhibition and activation.

Clinical management and outcomes of HIV-positive patients newly diagnosed with prostate cancer: a single institution experience.

INTRODUCTION: 10-year outcomes in patients living with HIV who are diagnosed with prostate cancer are unknown. METHODS: 52 patients living with HIV were diagnosed with prostate cancer. Disease-free survival stratified by clinical, pathologic, and HIV characteristics were examined. RESULTS: No difference in disease-free survival was observed based on prostate cancer treatment modality, CD4 count, or HIV viral load. CONCLUSIONS: Prostate cancer outcomes in patients living with HIV are favorable irrespective of treatment modality.

Clinical Efficacy of Bipolar Androgen Therapy in Men with Metastatic Castration-Resistant Prostate Cancer and Combined Tumor-Suppressor Loss.

Bipolar androgen therapy (BAT) relies on oscillating levels of serum testosterone as a way to treat patients with metastatic castration-resistant prostate cancer (mCRPC). Aggressive-variant prostate cancers typically require combination chemotherapy and are frequently associated with loss-of-function mutations in tumor suppressor genes. Here we report clinical outcomes after BAT among patients with mCRPC harboring pathogenic alterations in at least two of three genes: TP53, PTEN, and RB1. In this setting, BAT induced a meaningful PSA50 response rate, progression-free survival and overall survival, particularly in patients without prior chemotherapy. Patient summary: Bipolar androgen therapy, in which drugs are used to raise testosterone levels and then allow them to decrease again in a cycle, may be a safe and effective treatment for prostate cancer that is resistant to testosterone suppression and has mutations in tumor suppressor genes. A randomized study comparing this approach to chemotherapy is needed to confirm the findings.

A Phase Ib/II Study of Sabizabulin, a Novel Oral Cytoskeleton Disruptor, in Men with Metastatic Castration-resistant Prostate Cancer with Progression on an Androgen Receptor-targeting Agent.

PURPOSE: Sabizabulin, an oral cytoskeleton disruptor, was tested in a phase Ib/II clinical study in men with metastatic castration-resistant prostate cancer (mCRPC). PATIENTS AND METHODS: The phase Ib portion utilized a 3+3 design with escalating daily oral doses of 4.5-81 mg and increasing schedule in 39 patients with mCRPC treated with one or more androgen receptor-targeting agents. Prior taxane chemotherapy was allowed. The phase II portion tested a daily dose of 63 mg in 41 patients with no prior chemotherapy. Efficacy was assessed using PCWG3 and RECIST 1.1 criteria. RESULTS: The MTD was not defined in the phase Ib and the recommended phase II dose was set at 63 mg/day. The most common adverse events (>10% frequency) at the 63 mg oral daily dosing (combined phase Ib/II data) were predominantly grade 1-2 events. Grade ≥3 events included diarrhea (7.4%), fatigue (5.6%), and alanine aminotransferase/aspartate aminotransferase elevations (5.6% and 3.7%, respectively). Neurotoxicity and neutropenia were not observed. Preliminary efficacy data in patients treated with ≥1 continuous cycle of 63 mg or higher included objective response rate in 6 of 29 (20.7%) patients with measurable disease (1 complete, 5 partial) and 14 of 48 (29.2%) patients had PSA declines. The Kaplan-Meier median radiographic progression-free survival was estimated to be 11.4 months (n = 55). Durable responses lasting >2.75 years were observed. CONCLUSIONS: This clinical trial demonstrated that chronic oral daily dosing of sabizabulin has a favorable safety profile with preliminary antitumor activity. These data support the ongoing phase III VERACITY trial of sabizabulin in men with mCRPC.