The first objective was to determine the appropriate dose to use in evaluation of the male C57BL/6 mice. Doses at 1, 10, 50 and 100 mg/day were evaluated and the 10 mg/day dose wa s found to be most appr opriate given that it achieved a serum concentration of 20 ug/ml, consistent with serum levels in humans. Therefore, that was the dose evaluated in male C57BL/6 mice. ( Figure 6A ) It was confirmed that enzalutamide at 10 mg/day had a significant decrease in the weight of the genitourinary organs after 14 days of dosing, demonstrating the physio logic effects of enzalutamide at 10 mg/day dose level. Figure 6B ) Figure 6. Enzalutamide mediates a reduction in genitourinary (GU) weight. (A) Concentration of Enzalutamide in plasma of mice on Enzalutamide daily diet. Male C57BL/6 mice (n=3) were treated with Enzalutamide at different calculated target daily doses (0, 1, 10, 50, and 100mg) for 14 days. On day 15, blood was collected and Enzalutamide concentration in the plasma was determined. (B) Exposure to Enzalutamide causes reduction of GU weight. Male C57BL/6 mice (n=7) were not treated (open circles) or treated with Enzalutamide (closed circles) for 14 days. On day 15, mice were sacrificed and their GU and were harvested and weighed. All experiments were done three times with similar results. Statistical analyses were done by Student’s t-test From an immunologic standpoint, complete blood counts and Fluorescence-activated cell sorting analysis of immune cell subpopulations were foun d to be unchanged. Furthermore, functional analysis based on mixed lymphocyte response and CD3-induced proliferation assays of CD4 cells demonstrated no significant differences. In addition, similar to previous studies with hormonal therapies, enzalutamide treatment was associated with increased thymic weights and increased T-cell excision circles, consistent w ith the production of new T-cells from the thymus. (Figure 7 ) This series of experiment s (publication pending) provide s evidence that enzalutamide likely will not diminish the quantity or functionality of immune cells and may even enhance thymic production of naïve T-cells, allowing fo r potential immune stimulation by a therapeutic cancer vaccine such as PSA-TRICOM. Figure 7 .A. Enzalutamide mediates an enlargement of thymus and an increase in T-cell Receptor Excision Circles (TREC) levels. (A) . Male C57BL/6 mice (n=7) were not treated (open circles) or treated with Enzalutamide (closed circles) for 14 days. On day 15, mice were sacrificed, and their thymi harvested and weighed. (B). Enzalutamide significantly increases T-cell Excision Circle (TREC) levels in male mice. Male C57BL/6 mice (n=7) were not treated (open circles) or treated with Enzalutamide (closed circles) for 14 days. On day 15, 100ng of DNA from blood was collected and TREC levels were quantified by RT-PCR in triplicate. Results were normalized against the cons tant gene segment of TCRA, which serves as endogenous reference gene.