Enzalutamide in Combination with Abiraterone Acetate in Bone Metastatic Castration-resistant Prostate Cancer Patients.

BACKGROUND: It is hypothesised that cotargeting the androgen receptor (AR) and paracrine androgen biosynthesis with enzalutamide and abiraterone acetate in metastatic castration-resistant prostate cancer (mCRPC) will dissipate adaptive feedback loops observed with either agent alone. OBJECTIVE: To assess the safety, efficacy, androgen signalling/metabolome, and drug-drug interactions (DDIs) of enzalutamide with abiraterone acetate in progressive bone mCRPC (bmCRPC). DESIGN, SETTING, AND PARTICIPANTS: This open-label, single-centre interventional study was conducted in bmCRPC patients. INTERVENTION: Enzalutamide 160mg and abiraterone acetate 1000mg once daily; prednisone 5mg twice daily. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Adverse events (AEs), prostate-specific antigen (PSA) response, progression-free survival (PFS), tumour biomarker/metabolite expression, and Cmin plasma concentrations were evaluated. RESULTS AND LIMITATIONS: Sixty patients were enrolled. Common AEs independent of grade/causality included fatigue (72%), hyperglycaemia (67%), alkaline phosphatase (ALP) elevation (53%), and hot flush (43%). Grade 3 AEs included hypertension (17%), alanine aminotransferase elevation (12%), ALP elevation (5%), and arthralgia (5%). No treatment-related grade 4 AEs or deaths were reported. Median treatment-discontinuation time was 312d (95% confidence interval [CI] 196.0-483.0). Maximal PSA decline ≥50% and ≥90% occurred in 46 (77%) and 29 (48%) patients, respectively. Median PFS was 251d (95% CI 147-337). At week 9, median tumour microenvironment androgens, precursors, and nuclear AR expression decreased (p<0.001). The baseline tumour AR C/N terminal ratio of ≥80% was associated with treatment benefit. At enzalutamide steady state, abiraterone acetate Cmin was ∼23% lower (range 14.05-200.5ng/ml) than when given alone. CONCLUSIONS: Enzalutamide combined with abiraterone acetate has a manageable safety profile, without a meaningful DDI. Both agents are pharmacodynamically active with no feedback. Efficacy findings do not support significant benefit of combined treatment for unselected bmCRPC. PATIENT SUMMARY: This is the first study combining enzalutamide plus abiraterone in bone metastatic castration-resistant prostate cancer. Results show that this combination is safe.

Clinical outcomes and survival surrogacy studies of prostate-specific antigen declines following enzalutamide in men with metastatic castration-resistant prostate cancer previously treated with docetaxel.

BACKGROUND: In the AFFIRM trial, enzalutamide significantly increased overall survival (OS) for men with metastatic castration-resistant prostate cancer (mCRPC) after chemotherapy versus placebo and significantly decreased prostate-specific antigen (PSA) levels. The goal of this post hoc analysis was to associate levels of PSA decline from baseline after enzalutamide with clinical outcomes in the postchemotherapy mCRPC setting. METHODS: Men in the AFFIRM trial (n = 1199) were grouped by maximal PSA decline in the first 90 days of treatment. Kaplan-Meier estimates evaluated the association of defined PSA changes from baseline with OS, progression-free survival (PFS), radiographic PFS (rPFS), and pain response. Each PSA decline category was assessed for OS surrogacy using Prentice criteria, proportion of treatment effect explained (PTE), and proportion of variation explained. RESULTS: Men treated with enzalutamide had improved OS (hazard ratio, 0.63; P < .001) and higher rates of PSA decline (odds ratio, >19.0; P < .001) versus placebo. PSA declines of any, ≥30%, ≥50%, and ≥90% with enzalutamide were strongly associated with greater OS, PSA PFS, rPFS (P < .001), and pain response (P < .026) versus PSA increase/no decline. Any, ≥30%, and ≥50% declines in PSA resulted in the PTE range of 1.07-1.29, where treatment was no longer significant after adjustment for decline measures (P > .20). CONCLUSIONS: PSA declines of any, ≥30%, and ≥50% following enzalutamide were associated with greater clinical and pain response and improvements in PFS and OS. Surrogacy of PSA decline for OS was not fully established, possibly due to lack of PSA declines with placebo, and discordant results between PSA and imaging responses over time, and because some declines were not durable due to rapid resistance development. However, a lack of PSA decline by 90 days following enzalutamide treatment was a poor prognosis indicator in this setting. Conclusions from sensitivity analyses of maximal PSA decline from baseline over the entire treatment period are consistent with PSA declines restricted to the first 90 days. Cancer 2017;123:2303-2311. © 2017 American Cancer Society.

ASP9853, an inhibitor of inducible nitric oxide synthase dimerization, in combination with docetaxel: preclinical investigation and a Phase I study in advanced solid tumors.

PURPOSE: ASP9853 is an inhibitor of inducible nitric oxide (NO) synthase (iNOS) dimerization, which results in decreased NO production. Here, we report preclinical pharmacology of ASP9853 and the impact of ASP9853 in combination with a taxane on tumor volume in vivo. In addition, a Phase I open-label study of ASP9853 plus docetaxel was conducted to assess this combination in patients with advanced solid tumors. METHODS: The preclinical efficacy of ASP9853 in combination with a taxane was studied in tumor-bearing mice. In the clinic, patients with solid tumors that had progressed or failed to respond to previous therapies were treated with once-daily ASP9853 in combination with docetaxel once every 3 weeks to assess safety and tolerability and to determine the maximum tolerated dose (MTD) and the recommended Phase II dose (RP2D) of the combination. RESULTS: ASP9853 in combination with docetaxel showed greater tumor growth inhibition than docetaxel alone against non-small lung cancer xenografts. Twenty patients were treated with ASP9853 and docetaxel. Five patients experienced neutropenic dose-limiting toxicities. Owing to overall toxicity that limited further dose escalation, the ASP9853 concentrations predicted for efficacy, based on the preclinical data, were not achieved. Due to toxicity and lack of clear efficacy, the study was terminated without determination of MTD or RP2D. CONCLUSIONS: Inhibition of iNOS by ASP9853 in combination with docetaxel was not tolerable and resulted in the possible potentiation of neutropenia. Manipulation of the iNOS pathway, with or without chemotherapy, appears to be more complicated than initially expected.

Safety of enzalutamide in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel: expanded access in North America.

BACKGROUND: The open-label, single-arm enzalutamide expanded access program (EAP) in the United States and Canada evaluated the safety of enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC) who had previously received docetaxel. METHODS: Patients (n = 507) received enzalutamide 160 mg/day until disease progression, intolerable adverse events (AEs), or commercial availability occurred. AEs and other safety variables were assessed on day 1, weeks 4 and 12, and every 12 weeks thereafter. Data following transition to commercial drug were not collected. RESULTS: Median age was 71 years (range 43-97); 426 patients (83.9%) had a baseline ECOG score of ≤1. In addition to docetaxel, the majority of patients had received prior prostate cancer treatments such as abiraterone (76.1%) or cabazitaxel (28.6%). Median study treatment duration was 2.6 months (range 0.03-9.07). The most frequently reported reasons for discontinuation were commercial availability of enzalutamide (46.7%) and progressive disease (33.7%). A total of 88.2% of patients experienced AEs; 45.4% experienced AEs with a maximum grade of 1 or 2. Fatigue (39.1%), nausea (22.7%), and anorexia (14.8%) were the most commonly reported AEs. Seizure was reported in four patients (0.8%). The most commonly reported event leading to death was progression of metastatic prostate cancer (7.7%). CONCLUSION: In this heavily pretreated EAP population with progressive mCRPC, enzalutamide was well tolerated and the safety profile was consistent with that of the AFFIRM trial.