 The primary objective of this phase II study is to assess the anti-cancer activity of weekly ridaforolimus administration in participants with taxane-resistant AIPC. Other objectives include evaluating experimental parameters that may predict or indicate response to mTOR inhibition, such as effects on plasma VEGF, markers of tumoral PI3KmTOR-pathway activity, and proteomic analysis. The inclusion of these evaluations in this trial may provide insight into the identification of markers that may be helpful in optimizing ridaforolimus treatment and in identifying patients with ridaforolimus-sensitive tumors. 