Development and Characterization of the Next Generation Drug for the Direct Targeting of the FKBP52 Co-Chaperone for the Treatment of Castration Resistant Prostate Cancer
Prostate cancer is the most common cancer among American men, the third highest mortality rate. Current treatment options consist of androgen deprivation therapies, actual or chemical castration, and the use of androgen blockers called anti-androgens. Ultimately the disease advances to a hormone-independent state known as castration-resistant prostate cancer (CRPC). The folding, activation, and nuclear translocation of steroid hormone receptors requires the sequential action and cooperation of at least twelve proteins that make up four distinct complexes. At least one of these proteins, the FKBP52 cochaperone, is a promising therapeutic target for disrupting several mechanisms important in prostate cancer (PCa). FKBP52 is a positive regulator of androgen (AR), glucocorticoid (GR), and progesterone receptor (PR) hormone binding, nuclear translocation, and transcriptional activity. FKBP52 regulates multiple, distinct steps within the AR signaling pathway, some of which are independent of Hsp90. The direct targeting of FKBP52 will inhibit beta-catenin, FKBP51, and FKBP52-dependent potentiation of AR activity, including PCa cell growth, in addition to inhibiting GR and PR activity. Small molecules targeting FKBP52 would simultaneously hit multiple pathways known to having a role in PCa. Data suggest that the proline-rich loop surface that overhangs the FKBP52 PPIase pocket is important and likely represents an AR interaction surface. We aimed to identify specific PPIase binding molecules that, when docked in the pocket, reorient the proline-rich loop leading to the disruption of FKBP52 interactions. To this end, we used structure-based drug design methodology in order to identify molecules predicted to bind tightly to the FKBP52 PPIase pocket with high affinity. A primary screen of the predicted hits identified GMC1, a molecule that inhibits explicitly FKBP52-mediated AR, GR, and PR activity in reporter assays, AR-dependent gene expression in prostate cancer cells, AR-dependent proliferation of prostate cancer cells, and tumor growth in mouse xenograft models. We are currently performing hit-to-lead optimization by screening rationally designed GMC1 modifications to increase efficacy, reduce toxicity, and ensure bioavailability. Independent of GMC1, an in silico structure-based drug design identified PC257, a unique FKBP52-specific inhibitor that specifically inhibits FKBP52-mediated AR, GR, and PR activity in reporter assays, AR-dependent gene expression in a variety of prostate cancer cell lines, effectively abrogates AR-dependent proliferation in prostate cancer cells, alters full-length AR signaling and nuclear translocation in WT 22RV1 cells and inhibits tumor growth in mouse xenograft models. As a result, we have identified new leads from GMC1 SAR analysis and novel FKBP52-specific hits from the in silico screens that will be further characterized in both cellular and animal models of prostate cancer. We pursued the identification of drug combination therapies using classic anti-androgens alongside beta-blockers to increase efficacy, reduce toxicity and prolong drug resistance. We believe GMC1 and PC257 have the potential to be a first-in-class drug that directly targets the FKBP52 cochaperone for the treatment of prostate cancer, and drug combination therapy with beta-blockers will highlight the importance of current drug resistance to anti-androgens in the early stages of prostate cancer.
Biology|Molecular chemistry|Oncology|Biochemistry|Pharmaceutical sciences
Payan, Ashley Nichole, "Development and Characterization of the Next Generation Drug for the Direct Targeting of the FKBP52 Co-Chaperone for the Treatment of Castration Resistant Prostate Cancer" (2021). ETD Collection for University of Texas, El Paso. AAI28414880.