AR staining profiles of normal prostate, primary PCa and CRPC.

<p>(<b>A</b>) IHC staining for N- and C-terminal AR in normal prostate (NP) (a and b), hyperplastic prostate (HP) (c and d) and primary PCa (e-h) (magnification x200). (<b>B</b>) Comparison of AR staining profiles among normal prostate, hyperplastic prostate and primary PCa. (<b>C</b>) Comparison of AR staining profiles between primary PCa and metastatic CRPC.</p

Expression of AR variants and AR regulated proteins in metastatic CRPC.

<p>(<b>A</b>) IHC staining for N-terminal AR (a), C-terminal AR (b), PSA (c), PSMA (d), TMPRSS2 (e), AKT-1 (f), Ki-67(g), Negative control (h) on a metastatic CRPC tissue (magnification x200, insert x400). (<b>B</b>) PSA, PSMA, TMPRSS2 and AKT-1 staining profiles of CRPC.</p

The heterogeneity of AR expression in individual patients.

<p>Multiple metastatic sites of 42 CRPC patients had been analyzed by IHC using 2 AR antibodies. The staining results were summarized as N+C+ (blue), N+C↓ (orange) and N-C- (red). LN = lymph node; L =  lumbar vertebra; R. =  right; L. =  left; T =  thoracic vertebra.</p

Clinical data of 42 CRPC patients^*.

<p>*All 42 patients had castrate resistant prostate cancer at the time of autopsy, defined by the presence of a rising serum PSA following medical or surgical castration. All patients' tissues were obtained at autopsy under University of Washington Medical Center Prostate Cancer Donor Rapid Autopsy Program.</p

Comparison of IHC with RT-PCR results in PCa Metastases.

<p>+Intense expression, ±Limited/weak expression, − No expression.</p

Antibodies used in this study.

<p>Antibodies used in this study.</p

A phase I study of niclosamide in combination with enzalutamide in men with castration-resistant prostate cancer

<div><p>Background</p><p>Niclosamide, an FDA-approved anti-helminthic drug, has activity in preclinical models of castration-resistant prostate cancer (CRPC). Potential mechanisms of action include degrading constitutively active androgen receptor splice variants (AR-Vs) or inhibiting other drug-resistance pathways (e.g., Wnt-signaling). Published pharmacokinetics data suggests that niclosamide has poor oral bioavailability, potentially limiting its use as a cancer drug. Therefore, we launched a Phase I study testing oral niclosamide in combination with enzalutamide, for longer and at higher doses than those used to treat helminthic infections.</p><p>Methods</p><p>We conducted a Phase I dose-escalation study testing oral niclosamide plus standard-dose enzalutamide in men with metastatic CRPC previously treated with abiraterone. Niclosamide was given three-times-daily (TID) at the following dose-levels: 500, 1000 or 1500mg. The primary objective was to assess safety. Secondary objectives, included measuring AR-V expression from circulating tumor cells (CTCs) using the AdnaTest assay, evaluating PSA changes and determining niclosamide’s pharmacokinetic profile.</p><p>Results</p><p>20 patients screened and 5 enrolled after passing all screening procedures. 13(65%) patients had detectable CTCs, but only one was AR-V+. There were no dose-limiting toxicities (DLTs) in 3 patients on the 500mg TID cohort; however, both (N = 2) subjects on the 1000mg TID cohort experienced DLTs (prolonged grade 3 nausea, vomiting, diarrhea; and colitis). The maximum plasma concentration ranged from 35.7–82 ng/mL and was not consistently above the minimum effective concentration in preclinical studies. There were no PSA declines in any enrolled subject. Because plasma concentrations at the maximum tolerated dose (500mg TID) were not consistently above the expected therapeutic threshold, the Data Safety Monitoring Board closed the study for futility.</p><p>Conclusions</p><p>Oral niclosamide could not be escalated above 500mg TID, and plasma concentrations were not consistently above the threshold shown to inhibit growth in CRPC models. Oral niclosamide is not a viable compound for repurposing as a CRPC treatment.</p><p>Clinical trial registry</p><p>Clinicaltrials.gov: <a href="https://clinicaltrials.gov/ct2/show/NCT02532114" target="_blank">NCT02532114</a></p></div

AR splice variant detection using AdnaTest.

<p>AR splice variant detection using AdnaTest.</p

Study flow diagram.

<p>*All screen failures were due to undetectable androgen receptor splice variants, which were mandated to be present under protocol version 1. Protocol version 2 removed this criterion. MTD, maximum tolerated dose; TID, three times daily; PO, by mouth; DSMB, data safety monitoring committee.</p