Niraparib plus abiraterone acetate with prednisone in patients with metastatic castration-resistant prostate cancer and homologous recombination repair gene alterations: second interim analysis of the randomized phase III MAGNITUDE trial.

BACKGROUND: Patients with metastatic castration-resistant prostate cancer (mCRPC) and BRCA alterations have poor outcomes. MAGNITUDE found patients with homologous recombination repair gene alterations (HRR+), particularly BRCA1/2, benefit from first-line therapy with niraparib plus abiraterone acetate and prednisone (AAP). Here we report longer follow-up from the second prespecified interim analysis (IA2). PATIENTS AND METHODS: Patients with mCRPC were prospectively identified as HRR+ with/without BRCA1/2 alterations and randomized 1 : 1 to niraparib (200 mg orally) plus AAP (1000 mg/10 mg orally) or placebo plus AAP. At IA2, secondary endpoints [time to symptomatic progression, time to initiation of cytotoxic chemotherapy, overall survival (OS)] were assessed. RESULTS: Overall, 212 HRR+ patients received niraparib plus AAP (BRCA1/2 subgroup, n = 113). At IA2 with 24.8 months of median follow-up in the BRCA1/2 subgroup, niraparib plus AAP significantly prolonged radiographic progression-free survival {rPFS; blinded independent central review; median rPFS 19.5 versus 10.9 months; hazard ratio (HR) = 0.55 [95% confidence interval (CI) 0.39-0.78]; nominal P = 0.0007} consistent with the first prespecified interim analysis. rPFS was also prolonged in the total HRR+ population [HR = 0.76 (95% CI 0.60-0.97); nominal P = 0.0280; median follow-up 26.8 months]. Improvements in time to symptomatic progression and time to initiation of cytotoxic chemotherapy were observed with niraparib plus AAP. In the BRCA1/2 subgroup, the analysis of OS with niraparib plus AAP demonstrated an HR of 0.88 (95% CI 0.58-1.34; nominal P = 0.5505); the prespecified inverse probability censoring weighting analysis of OS, accounting for imbalances in subsequent use of poly adenosine diphosphate-ribose polymerase inhibitors and other life-prolonging therapies, demonstrated an HR of 0.54 (95% CI 0.33-0.90; nominal P = 0.0181). No new safety signals were observed. CONCLUSIONS: MAGNITUDE, enrolling the largest BRCA1/2 cohort in first-line mCRPC to date, demonstrated improved rPFS and other clinically relevant outcomes with niraparib plus AAP in patients with BRCA1/2-altered mCRPC, emphasizing the importance of identifying this molecular subset of patients.

Deep, rapid, and durable prostate-specific antigen decline with apalutamide plus androgen deprivation therapy is associated with longer survival and improved clinical outcomes in TITAN patients with metastatic castration-sensitive prostate cancer.

BACKGROUND: The first interim analysis of the phase III, randomized, double-blind, placebo-controlled, multinational TITAN study demonstrated improved overall survival (OS) and radiographic progression-free survival (rPFS) with apalutamide added to ongoing androgen deprivation therapy (ADT) in patients with metastatic castration-sensitive prostate cancer. The final analysis confirmed improvement in OS and other long-term outcomes. We evaluated prostate-specific antigen (PSA) kinetics and the association between PSA decline and outcomes in patients with metastatic castration-sensitive prostate cancer from TITAN. PATIENTS AND METHODS: Patients received apalutamide (240 mg/day) or placebo plus ADT (1 : 1). This post hoc exploratory analysis evaluated PSA kinetics and decline in relation to rPFS (22.7 months' follow-up) and OS, time to PSA progression, and time to castration resistance (44.0 months' follow-up) in patients with or without confirmed PSA decline using a landmark analysis, the Kaplan-Meier method, and Cox proportional hazards model. RESULTS: One thousand and fifty-two patients (apalutamide, 525; placebo, 527) were enrolled. Best confirmed PSA declines (≥50% or ≥90% from baseline or to ≤0.2 ng/ml) were achieved at any time during the study in 90%, 73%, and 68% of apalutamide-treated versus 55%, 29%, and 32% of placebo-treated patients, respectively. By 3 months of apalutamide treatment, best deep PSA decline of ≥90% or to ≤0.2 ng/ml occurred in 59% and 51% of apalutamide- and in 13% and 18% of placebo-treated patients, respectively. Achievement of deep PSA decline at landmark 3 months of apalutamide treatment was associated with longer OS [hazard ratio (HR) 0.35; 95% confidence interval (CI) 0.25-0.48), rPFS (HR 0.44; 95% CI 0.30-0.65), time to PSA progression (HR 0.31; 95% CI 0.22-0.44), and time to castration resistance (HR 0.38; 95% CI 0.27-0.52) compared with no decline (P < 0.0001 for all). Similar results were observed at landmark 6 and 12 months of apalutamide treatment. CONCLUSIONS: Apalutamide plus ADT demonstrated a robust (rapid, deep, and durable) PSA decline that was associated with improved clinical outcomes, including long-term survival.

Cabazitaxel versus abiraterone or enzalutamide in poor prognosis metastatic castration-resistant prostate cancer: a multicentre, randomised, open-label, phase II trial.

BACKGROUND: Treatment of poor prognosis metastatic castration-resistant prostate cancer (mCRPC) includes taxane chemotherapy and androgen receptor pathway inhibitors (ARPI). We sought to determine optimal treatment in this setting. PATIENTS AND METHODS: This multicentre, randomised, open-label, phase II trial recruited patients with ARPI-naive mCRPC and poor prognosis features (presence of liver metastases, progression to mCRPC after <12 months of androgen deprivation therapy, or ≥4 of 6 clinical criteria). Patients were randomly assigned 1 : 1 to receive cabazitaxel plus prednisone (group A) or physician's choice of enzalutamide or abiraterone plus prednisone (group B) at standard doses. Patients could cross over at progression. The primary endpoint was clinical benefit rate for first-line treatment (defined as prostate-specific antigen response ≥50%, radiographic response, or stable disease ≥12 weeks). RESULTS: Ninety-five patients were accrued (median follow-up 21.9 months). First-line clinical benefit rate was greater in group A versus group B (80% versus 62%, P = 0.039). Overall survival was not different between groups A and B (median 37.0 versus 15.5 months, hazard ratio (HR) = 0.58, P = 0.073) nor was time to progression (median 5.3 versus 2.8 months, HR = 0.87, P = 0.52). The most common first-line treatment-related grade ≥3 adverse events were neutropenia (cabazitaxel 32% versus ARPI 0%), diarrhoea (9% versus 0%), infection (9% versus 0%), and fatigue (7% versus 5%). Baseline circulating tumour DNA (ctDNA) fraction above the cohort median and on-treatment ctDNA increase were associated with shorter time to progression (HR = 2.38, P < 0.001; HR = 4.03, P < 0.001). Patients with >30% ctDNA fraction at baseline had markedly shorter overall survival than those with undetectable ctDNA (HR = 38.22, P < 0.001). CONCLUSIONS: Cabazitaxel was associated with a higher clinical benefit rate in patients with ARPI-naive poor prognosis mCRPC. ctDNA abundance was prognostic independent of clinical features, and holds promise as a stratification biomarker.

HSD3B1 (1245A>C) germline variant and clinical outcomes in metastatic castration-resistant prostate cancer patients treated with abiraterone and enzalutamide: results from two prospective studies.

BACKGROUND: A common polymorphism (1245A>C) in the HSD3B1 gene is associated with increased de novo synthesis of androgens and worse outcomes in men treated with androgen-deprivation therapy for metastatic castration-sensitive prostate cancer. The objective of the study was to determine whether this polymorphism is associated with outcomes for metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone or enzalutamide. PATIENTS AND METHODS: A total of 547 patients treated with abiraterone or enzalutamide from two prospective cohorts were evaluated. The HSD3B1 genotype was determined by targeted sequencing and/or TaqMan single-nucleotide polymorphism genotyping. In cohort 1, patients were randomized to receive abiraterone + prednisone or enzalutamide. In cohort 2, patients received either agent according to investigator's choice. Prostate-specific antigen (PSA) response rate, time to PSA progression (TTPP), time to progression (TTP) and overall survival were determined. Associations between HSD3B1 genotypes and outcomes were evaluated via univariate Cox regression. Multivariable Cox model was used to determine the independent association of each covariate. RESULTS: The HSD3B1 variant genotype (CC) was present in 15% of patients and was associated with worse TTP [hazard ratio (HR) 1.31, 95% confidence interval (CI) 1.02-1.67, P = 0.032] and PSA response rates (48% for CC versus 62% and 65% for AA and AC, respectively [P = 0.019]), with no significant difference in TTPP (HR 1.28, 95% CI 0.99-1.66, P = 0.064). The effect of genotype was similar for treatment with abiraterone or enzalutamide with a negative test for interaction for TTPP (P = 0.997) and TTP (P = 0.749). Multivariable analysis did not show a significant association between genotype and TTP or TTPP. CONCLUSIONS: The HSD3B1 (CC) genotype was associated with shorter TTP and lower PSA response rate in patients with mCRPC treated with abiraterone or enzalutamide. However, the CC genotype did not provide prognostic information beyond that conferred by standard clinical variables, suggesting that it may not be a suitable stand-alone biomarker in mCRPC.

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.

Second-line systemic therapies for metastatic urothelial carcinoma: a population-based cohort analysis.

Introduction: Patients with urothelial carcinoma (uc) have a poor prognosis after progression on first-line cisplatin-based chemotherapy. Real-world data about second-line cytotoxic therapies are limited. We sought to characterize patients with metastatic uc who receive more than 1 line of systemic therapy and to describe their treatments and outcomes. Methods: Using BC Cancer's pharmacy database, we identified patients with documented metastatic uc who had received more than 1 line of systemic therapy. A retrospective chart review was then performed to collect clinicopathologic, treatment, and outcomes data. Results: The 51 included patients, of whom 42 were men (82%), had a median age of 65 years (range: 38-81 years). Sites of metastasis included lymph nodes (n = 30), bone (n = 7), lung (n = 9), and peritoneum (n = 2). Second-line chemotherapy regimens included gemcitabine-cisplatin [gc (n = 14)], paclitaxel (n = 24), docetaxel (n = 12), and an oral topoisomerase i inhibitor (n = 1). Median time to progression (ttp) and overall survival (os) were 2.0 and 6.83 months respectively. Compared with patients who received a different agent, patients who had experienced a prior response to first-line gc and who were re-challenged with second-line gc had a better median ttp (11.0 months vs. 6.0 months, p = 0.02) and survived longer (4.0 months vs. 1.0 months, p = 0.02). No differences in os between non-gc regimens were evident. Conclusions: In patients with metastatic uc, overall outcomes remain poor, but compared with patients receiving other agents, the subgroup of patients re-challenged with second-line gc demonstrated improved ttp. Conventional chemotherapy regimens provide only modest benefits in the second-line setting and have largely been replaced with immunotherapy.

A phase I dose-escalation study of apatorsen (OGX-427), an antisense inhibitor targeting heat shock protein 27 (Hsp27), in patients with castration-resistant prostate cancer and other advanced cancers.

BACKGROUND: Heat shock protein 27 (Hsp27) is a chaperone protein that regulates cell survival via androgen receptor and other signaling pathways, thereby mediating cancer progression. Apatorsen (OGX-427) is a 2'-methoxyethyl-modified antisense oligonucleotide that inhibits Hsp27 expression. This study evaluated the safety profile and recommended phase II dosing of apatorsen in patients with advanced cancer. PATIENTS AND METHODS: Patients with castration-resistant prostate (CRPC), breast, ovary, lung, or bladder cancer were enrolled to this phase I dose-escalation study. Apatorsen was administered i.v. weekly in 21-day cycles following 3 loading doses and over 5 dose levels (200-1000 mg). Apatorsen plasma concentrations, circulating tumor cells (CTCs) and CTC Hsp27 expression, and serum Hsp27 levels were evaluated. RESULTS: Forty-two patients were accrued, of which 52% had CRPC. Patients were heavily pretreated, with 57% having had ≥3 prior chemotherapy regimens. During the loading dose/cycle 1 and overall study period, 93% and 100% of patients (N = 42) experienced treatment-related adverse events, respectively; most were grade 1-2 and included chills, pruritus, flushing, prolonged aPTT, lymphopenia, and anemia. One patient experienced a dose-limiting toxicity at the 600 mg dose level (intracranial hemorrhage in a previously undiagnosed brain metastasis). A maximum tolerated dose was not defined. Apatorsen Cmax increased proportionally with dose. Decreases in tumor markers and declines in CTCs were observed, with a prostate-specific antigen decline >%50% occurring in 10% of patients with CRPC; 29/39 assessable patients (74%) had reductions from ≥5 CTC/7.5 ml at baseline to <5 CTC/7.5 ml post-treatment. Twelve patients had stable measurable disease as best response. CONCLUSIONS: Apatorsen was tolerated at the highest dose evaluated (1000 mg). Single-agent activity was suggested by changes in tumor markers, CTC, and stable measurable disease. Phase II studies evaluating apatorsen are underway. CLINICALTRIALSGOV ID: NCT00487786.

A prognostic index model for predicting overall survival in patients with metastatic castration-resistant prostate cancer treated with abiraterone acetate after docetaxel.

BACKGROUND: Few prognostic models for overall survival (OS) are available for patients with metastatic castration-resistant prostate cancer (mCRPC) treated with recently approved agents. We developed a prognostic index model using readily available clinical and laboratory factors from a phase III trial of abiraterone acetate (hereafter abiraterone) in combination with prednisone in post-docetaxel mCRPC. PATIENTS AND METHODS: Baseline data were available from 762 patients treated with abiraterone-prednisone. Factors were assessed for association with OS through a univariate Cox model and used in a multivariate Cox model with a stepwise procedure to identify those of significance. Data were validated using an independent, external, population-based cohort. RESULTS: Six risk factors individually associated with poor prognosis were included in the final model: lactate dehydrogenase > upper limit of normal (ULN) [hazard ratio (HR) = 2.31], Eastern Cooperative Oncology Group performance status of 2 (HR = 2.19), presence of liver metastases (HR = 2.00), albumin ≤4 g/dl (HR = 1.54), alkaline phosphatase > ULN (HR = 1.38) and time from start of initial androgen-deprivation therapy to start of treatment ≤36 months (HR = 1.30). Patients were categorized into good (n = 369, 46%), intermediate (n = 321, 40%) and poor (n = 107, 13%) prognosis groups based on the number of risk factors and relative HRs. The C-index was 0.70 ± 0.014. The model was validated by the external dataset (n = 286). CONCLUSION: This analysis identified six factors used to model survival in mCRPC and categorized patients into three distinct risk groups. Prognostic stratification with this model could assist clinical practice decisions for follow-up and monitoring, and may aid in clinical trial design. TRIAL REGISTRATION NUMBERS: NCT00638690.

A phase II study of the HDAC inhibitor SB939 in patients with castration resistant prostate cancer: NCIC clinical trials group study IND195.

BACKGROUND: SB939 is a potent oral inhibitor of class 1, 2, and 4 histone deacetylases (HDACs). These three HDAC classes are highly expressed in castration resistant prostate cancer (CRPC) and associated with poor clinical outcomes. We designed a phase II study of SB939 in men with metastatic CRPC. METHODS: Patients received SB939 60 mg on alternate days three times per week for 3 weeks on a 4-week cycle. Primary endpoints were PSA response rate (RR) and progression-free survival (PFS). Secondary endpoints included objective response rate and duration; overall survival; circulating tumor cell (CTC) enumeration and safety. Exploratory correlative studies of the TMPRSS2-ERG fusion and PTEN biomarkers were also performed. RESULTS: Thirty-two patients were enrolled of whom 88 % had received no prior chemotherapy. The median number of SB939 cycles administered was three (range 1-8). Adverse events were generally grade 1-2, with five pts experiencing one or more grade three event. One patient died due to myocardial infarction. A confirmed PSA response was noted in two pts (6 %), lasting 3.0 and 21.6 months. In patients with measurable disease there were no objective responses. Six patients had stable disease lasting 1.7 to 8.0 months. CTC response (from ≥5 at baseline to <5 at 6 or 12 weeks) occurred in 9/14 evaluable patients (64 %). CONCLUSION: Although SB939 was tolerable at the dose/schedule given, and showed declines in CTC in the majority of evaluable patients, it did not show sufficient activity based on PSA RR to warrant further study as a single agent in unselected patients with CRPC.

Activity of enzalutamide in men with metastatic castration-resistant prostate cancer is affected by prior treatment with abiraterone and/or docetaxel.

BACKGROUND: Enzalutamide and abiraterone are new androgen-axis disrupting treatments for metastatic castration-resistant prostate cancer (mCRPC). We examined the response and outcomes of enzalutamide-treated mCRPC patients in the real-world context of prior treatments of abiraterone and/or docetaxel. METHODS: We conducted a seven-institution retrospective study of mCRPC patients treated with enzalutamide between January 2009 and February 2014. We compared the baseline characteristics, PSA declines, PSA progression-free survival (PSA-PFS), duration on enzalutamide and overall survival (OS) across subgroups defined by prior abiraterone and/or docetaxel. RESULTS: Of 310 patients who received enzalutamide, 36 (12%) received neither prior abiraterone nor prior docetaxel, 79 (25%) received prior abiraterone, 30 (10%) received prior docetaxel and 165 (53%) received both prior abiraterone and prior docetaxel. Within these groups, respectively, ⩾30% PSA decline was achieved among 67, 28, 43 and 24% of patients; PSA-PFS was 5.5 (95% CI 4.2-9.1), 4.0 (3.2-4.8), 4.1 (2.9-5.4) and 2.8 (2.5-3.2) months; median duration of enzalutamide was 9.1 (7.3-not reached), 4.7 (3.7-7.7), 5.4 (3.8-8.4) and 3.9 (3.0-4.6) months. Median OS was reached only for the patients who received both prior abiraterone and docetaxel and was 12.2 months (95% CI 10.7-16.5). 12-month OS was 78% (59-100%), 64% (45-90%), 77% (61-97%) and 51% (41-62%). Of 70 patients who failed to achieve any PSA decline on prior abiraterone, 19 (27%) achieved ⩾30% PSA decline with subsequent enzalutamide. CONCLUSIONS: The activity of enzalutamide is blunted after abiraterone, after docetaxel, and still more after both, suggesting subsets of overlapping and distinct mechanisms of resistance.

Denosumab for the prevention of skeletal complications in metastatic castration-resistant prostate cancer: comparison of skeletal-related events and symptomatic skeletal events.

BACKGROUND: In a phase III trial in patients with castration-resistant prostate cancer (CRPC) and bone metastases, denosumab was superior to zoledronic acid in reducing skeletal-related events (SREs; radiation to bone, pathologic fracture, surgery to bone, or spinal cord compression). This study reassessed the efficacy of denosumab using symptomatic skeletal events (SSEs) as a prespecified exploratory end point. PATIENTS AND METHODS: Patients with CRPC, no previous bisphosphonate exposure, and radiographic evidence of bone metastasis were randomized to subcutaneous denosumab 120 mg plus i.v. placebo every 4 weeks (Q4W), or i.v. zoledronic acid 4 mg plus subcutaneous placebo Q4W during the blinded treatment phase. SSEs were defined as radiation to bone, symptomatic pathologic fracture, surgery to bone, or symptomatic spinal cord compression. The relationship between SSE or SRE and time to moderate/severe pain was assessed using the Brief Pain Inventory Short Form. RESULTS: Treatment with denosumab significantly reduced the risk of developing first SSE [HR, 0.78; 95% confidence interval (CI) 0.66-0.93; P = 0.005] and first and subsequent SSEs (rate ratio, 0.78; 95% CI 0.65-0.92; P = 0.004) compared with zoledronic acid. The treatment differences in the number of patients with SSEs or SREs were similar (n = 48 and n = 45, respectively). Among patients with no/mild pain at baseline, both SSEs and SREs were associated with moderate/severe pain development (P < 0.0001). Fewer patients had skeletal complications, particularly fractures, when defined as SSE versus SRE. CONCLUSION: In patients with CRPC and bone metastases, denosumab reduced the risk of skeletal complications versus zoledronic acid regardless of whether the end point was defined as SSE or SRE.

Improved outcomes in elderly patients with metastatic castration-resistant prostate cancer treated with the androgen receptor inhibitor enzalutamide: results from the phase III AFFIRM trial.

BACKGROUND: The randomized, double-blind phase III AFFIRM trial demonstrated that enzalutamide, an oral androgen receptor inhibitor, significantly prolonged overall survival (OS) [median 18.4 versus 13.6 months (hazard ratio, HR) 0.63 (95% confidence interval, CI, 0.53-0.75); P<0.001] compared with placebo in patients with metastatic castration-resistant prostate cancer who received prior docetaxel chemotherapy. PATIENTS AND METHODS: A post hoc analysis was carried out to assess the efficacy and safety of enzalutamide on outcomes in younger (<75 years) and elderly (≥75 years) patients in the AFFIRM population. Statistics are presented by age group (<75 years, ≥75 years) for efficacy outcomes of OS, radiographic progression-free survival (rPFS), time to prostate-specific antigen (PSA) progression, PSA response, and safety. RESULTS: OS was significantly improved with enzalutamide over placebo in patients<75 years [median not yet reached versus 13.6 months; HR 0.63 (95% CI 0.52-0.78), P<0.001] and in patients ≥75 years [median 18.2 versus 13.3 months; HR 0.61 (95% CI 0.43-0.86), P=0.004], respectively. rPFS was similarly improved in both the younger [HR 0.45 (95% CI 0.38-0.53), P<0.001] and elderly patient cohorts [HR 0.27 (95% CI 0.20-0.37), P<0.001] relative to placebo, as were time to PSA progression and PSA response. Adverse events (AEs) were similar between the two enzalutamide age groups, with the exception of an increase in patients≥75 years in the rates of all grade peripheral edema (22.1% versus 12.5%), fatigue (39.7% versus 31.6%), and diarrhea (26.6% versus 19.6%). The overall grade≥3 AE rates were low with no major difference in frequency or severity between age groups or treatment arms. Five patients were reported with seizure events; three patients<75 years and two patients ≥75 years. CONCLUSIONS: Enzalutamide significantly improves outcomes in both younger (<75 years) and elderly patients (≥75 years), with comparable safety and tolerability.

NCIC CTG IND.181: phase I study of AT9283 given as a weekly 24 hour infusion in advanced malignancies.

PURPOSE: AT9283 is a potent inhibitor of the mitotic regulators, Aurora-kinases A and B, and has shown anti-tumor activity in patients with solid and haematological malignancies. This phase I study assessed safety, tolerability, pharmacokinetic and pharmacodynamic properties of AT9283. PATIENTS AND METHODS: Patients with advanced, incurable solid tumors or non-Hodgkin's lymphoma received AT9283 as a continuous 24-hour infusion on days 1, 8 of a 21-day cycle. A 3 + 3 dose escalation design was used with a starting dose of 1.5 mg/m(2)/day. Pharmacokinetic samples were collected from all patients on cycle one, and pharmacodynamic samples were collected from 4 patients at the recommended phase II dose (RP2D). RESULTS: 35 patients were evaluable for toxicity and 32 were evaluable for response. AT9283 was well tolerated, with main toxicities being reversible dose-related fatigue, gastrointestinal disturbance, anemia, lymphocytopenia and neutropenia. The dose limiting toxicities were febrile neutropenia (two patients) and neutropenia with grade 3 infection (1 patient) at 47 mg/m(2)/day (established as the maximum tolerated dose). The RP2D was 40 mg/m(2)/day. Pharmacokinetic analyses showed AT9283 appeared to follow linear kinetics, with a mean elimination half-life of 8.2 h. Pharmacodynamic analyses showed no consistent or significant changes, but trends suggested evidence of AT9283 inhibition and anti-proliferative activity. One patient had partial response and four patients experienced RECIST stable disease (median 2.6 months). CONCLUSION: In this study, AT9283 was well tolerated. The RP2D is 40 mg/m(2)/day on days 1, 8 of a 21-day cycle. Ongoing AT9283 trials will assess efficacy and safety in solid and haematological cancers.

The future of systemic therapies for localised prostate cancer.

In the last decade, many systemic therapies have become available to improve survival in the setting of castration-resistant prostate cancer. Once effective treatments for advanced and incurable disease have been established, these agents are generally explored in the adjuvant and neoadjuvant settings to evaluate their role in increasing the chance of cure for localised disease. Clinical trials evaluating new therapies in high-risk prostate cancer can broadly be divided into two categories. Phase III (and some phase II) trials generally evaluate treatments that have already been shown to provide clinical benefit in the advanced disease setting; whereas smaller phase I (and some phase II) trials often serve as proof-of-principle assessments in the development of novel agents. The goal of this review is to provide an overview of present and ongoing clinical trials of both of these categories, evaluating the promise of systemic therapies in the setting of high-risk localised prostate cancer. We undertook a search of Ovid Medline, Embase and clinicaltrials.gov for prospective clinical studies assessing systemic therapy for early stage prostate cancer, either before or after definitive local treatment (surgery or radiation) from 2000 onwards. This resulted in 53 studies, of which 29 were deemed worthy of this overview and are presented herein, broadly divided by mechanism of action. Clearly, the arena evaluating the future of systemic therapies for localised prostate cancer will be a very active one.

Clinical activity of abiraterone acetate in patients with metastatic castration-resistant prostate cancer progressing after enzalutamide.

BACKGROUND: Abiraterone acetate and enzalutamide both improve outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Optimal sequencing for these agents and whether cross-resistance occurs is unknown. METHODS: Multicentre review of patients with mCRPC treated with abiraterone acetate and prednisone after progressing on enzalutamide. Primary objective was to determine abiraterone acetate response. RESULTS: Thirty patients identified from four North American centres. At abiraterone initiation, median age was 70 years (56-84 years); 70% had ECOG performance status of 0-1; all had prior docetaxel. Median prior enzalutamide treatment duration was 41 weeks (6-95 weeks), with 70% (21 of 30) having a ≥30% prostate-specific antigen (PSA) decline. Median abiraterone acetate treatment duration was 13 weeks (1-52). No objective radiographic responses were observed. Median abiraterone time to progression (PSA, objective or symptomatic) was 15.4 weeks [95% confidence interval (CI) 10.7-20.2]. Median overall survival was 50.1 weeks (95% CI 28.3-72.0). Three patients had a ≥30% PSA decline with abiraterone. Two of these patients had PSA progression as best response with prior enzalutamide. CONCLUSIONS: In this study of patients progressing after enzalutamide, treatment with abiraterone was associated with a modest response rate and brief duration of effect. Primary progression on enzalutamide may not preclude a response to abiraterone.

Effect of abiraterone acetate plus prednisone on the pharmacokinetics of dextromethorphan and theophylline in patients with metastatic castration-resistant prostate cancer.

PURPOSE: To assess the effect of abiraterone acetate plus prednisone on the pharmacokinetics of dextromethorphan HBr (CYP2D6 substrate) and theophylline (CYP1A2 substrate) in patients with metastatic castration-resistant prostate cancer (mCRPC). METHODS: Men with progressive metastatic mCRPC who failed gonadotropin-releasing hormone therapy and ≥1 lines of chemotherapy were enrolled. Patients received two doses of dextromethorphan HBr-30 mg (n = 18; group A) or theophylline-100 mg (n = 16; group B) under fasting conditions; one dose on cycle 1, day -8, and the other dose on cycle 1, day 8. Only patients with extensive CYP2D6 metabolizing status were assigned to group A. All patients received continuous daily oral abiraterone acetate (1,000 mg) plus prednisone (10 mg) starting on cycle 1, day 1. RESULTS: Coadministration of abiraterone acetate plus prednisone increased the systemic exposure of dextromethorphan by approximately 100%. Ratios of geometric means for maximum plasma concentration (C(max)) (275.36%) and area under plasma concentration-time curves from time 0 to 24 h (AUC(24h)) (268.14%) of dextromethorphan were outside the bioequivalence limit. The pharmacokinetics of theophylline was unaltered following coadministration of abiraterone acetate plus prednisone. Ratios of geometric means [C(max); 102.36% and AUC(24h); 108.03%] of theophylline exposure parameters were within the bioequivalence limit. The safety profile of abiraterone acetate was consistent with reported toxicities. CONCLUSION: Abiraterone acetate plus prednisone increased the exposure of dextromethorphan, suggesting a need for caution when coadministrating with known CYP2D6 substrates. The pharmacokinetics of theophylline was unaffected when coadministered with abiraterone acetate plus prednisone.

Effect of abiraterone acetate plus prednisone on the QT interval in patients with metastatic castration-resistant prostate cancer.

PURPOSE: Abiraterone is the active metabolite of the pro-drug abiraterone acetate (AA) and a selective inhibitor of CYP17, a key enzyme in testosterone synthesis, and improves overall survival in postdocetaxel metastatic castration-resistant prostate cancer (mCRPC). This open-label, single-arm phase 1b study was conducted to assess the effect of AA and abiraterone on the QT interval. METHODS: The study was conducted in 33 patients with mCRPC. Patients received AA 1,000 mg orally once daily + prednisone 5 mg orally twice daily. Electrocardiograms (ECGs) were collected in triplicate using 12-lead Holter monitoring. Baseline ECGs were obtained on Cycle 1 Day-1. Serial ECG recordings and time-matched pharmacokinetic (PK) blood samples were collected over 24 h on Cycle 1 Day 1 and Cycle 2 Day 1. Serial PK blood samples were also collected over 24 h on Cycle 1 Day 8. RESULTS: After AA administration, the upper bound of the 2-sided 90 % confidence interval (CI) for the mean baseline-adjusted QTcF change was <10 ms; no patients discontinued due to QTc prolongation or adverse events. No apparent relationship between change in QTcF and abiraterone plasma concentrations was observed [estimated slope (90 % CI): 0.0031 (-0.0040, 0.0102)]. CONCLUSIONS: There is no significant effect of AA plus prednisone on the QT/QTc interval in patients with mCRPC.