Metastatic prostate cancer is treated with drugs that antagonize androgen action but most patients progress to a more aggressive form of the disease called castration-resistant prostate cancer, driven by elevated expression of the androgen receptor. Here we characterize the diarylthiohydantoins RD162 and MDV3100, two compounds optimized from a screen for non-steroidal antiandrogens that retain activity in the setting of increased androgen receptor expression. Both compounds bind to the androgen receptor with greater relative affinity than the clinically used antiandrogen bicalutamide, reduce the efficiency of its nuclear translocation and impair both DNA binding to androgen response elements and recruitment of coactivators. RD162 and MDV3100 are orally available and induce tumor regression in mouse models of castration-resistant human prostate cancer. Of the first 30 patients treated with MDV3100 in a phase I/II clinical trial, 13 of 30 (43 percent) showed sustained declines (by >50 percent) in serum levels of prostate specific antigen, a biomarker of prostate cancer. These compounds thus appear to be promising candidates for treatment of advanced prostate cancer.

The use of exosomes as a drug delivery vehicle has gained considerable interest. To establish if exosomes could be utilized effectively for drug delivery, a better understanding of their in vivo fate must be established. Through comparisons to liposomal formulations, which have been studied extensively for the last thirty years, we were able to make some comprehensive conclusions about the fate of unmodified tumor-derived exosomes in vivo. We observed a comparable rapid clearance and minimal tumor accumulation of intravenously-injected exosomes, PC:Chol liposomes, and liposomes formulated with the lipid extract of exosomes, suggesting the unique protein and lipid composition of exosomes does not appreciably impact exosomes’ rate of clearance and biodistribution. This rapid clearance along with minimal tumor accumulation of unmodified exosomes limits their use as an anti-cancer drug delivery vehicle; however, when delivered intratumorally, exosomes remained associated with tumor tissue to a significantly greater extent than PC:Chol liposomes. Furthermore, experiments utilizing mice with impaired adaptive or innate immune systems, revealed the significance of the innate immune system along with the complement protein C5 on exosomes’ rate of clearance.

Continued reliance on the androgen receptor (AR) is now understood as a core mechanism in castration-resistant prostate cancer (CRPC), the most advanced form of this disease. While established and novel AR-pathway targeting agents display clinical efficacy in metastatic CRPC, dose-limiting side effects remain problematic for all current agents. In this study, we report the discovery and development of ARN-509, a competitive AR inhibitor this is fully antagonistic to AR overexpression, a common and important feature of CRPC. ARN-509 was optimized for inhibition of AR transcriptional activity and prostate cancer cell proliferation, pharmacokinetics and in vivo efficacy. In contrast to bicalutamide, ARN-509 lacked significant agonist activity in preclinical models of CRPC. Moreover, ARN-509 lacked inducing activity for AR nuclear localization or DNA binding. In a clinically valid murine xenograft model of human CRPC, ARN-509 showed greater efficacy than MDV3100. Maximal therapeutic response in this model was achieved at 30 mg/kg/day of ARN-509, whereas the same response required 100 mg/kg/day of MDV3100 and higher steady-state plasma concentrations. Thus, ARN-509 exhibits characteristics predicting a higher therapeutic index with a greater potential to reach maximally efficacious doses in man than current AR antagonists. Our findings offer preclinical proof of principle for ARN-509 as a promising therapeutic in both castration-sensitive and castration-resistant forms of prostate cancer.

89 78.41 h) is a positron-emitting radionuclide that displays excellent potential for use in the design and synthesis of radioimmunoconjugates for immunoPET. In the current study, we report the preparation of 89 Zr-desferrioxamine B (DFO)-J591, a novel 89 Zr-labeled monoclonal antibody (mAb) construct for targeted immunoPET and quantification of prostate-specific membrane antigen (PSMA) expression in vivo. Methods: The in vivo behavior of 89 Zr-chloride, 89 Zr-oxalate, and 89 Zr-DFO was studied using PET. High-level computational studies using density functional theory calculations have been used to investigate the electronic structure of 89 Zr-DFO and probe the nature of the complex in aqueous conditions. 89 Zr-DFO-J591 was characterized both in vitro and in vivo. ImmunoPET in male athymic nu/nu mice bearing subcutaneous LNCaP (PSMA-positive) or PC-3 (PSMA-negative) tumors was conducted. The change in 89 Zr-DFO-J591 tissue uptake in response to high-and low-specific-activity formulations in the 2 tumor models was measured using acute biodistribution studies and immunoPET. Results: The basic characterization of 3 important reagents-89 Zr-chloride, 89 Zr-oxalate, and the complex 89 Zr-DFO-demonstrated that the nature of the 89 Zr species dramatically affects the biodistribution and pharmacokinetics. Density functional theory calculations provide a rationale for the observed high in vivo stability of 89 Zr-DFO-labeled mAbs and suggest that in aqueous conditions, 89 Zr-DFO forms a thermodynamically stable, 8-coordinate complex by coordination of 2 water molecules. 89 Zr-DFO-J591 was produced in high radiochemical yield (.77%) and purity (.99%), with a specific activity of 181.7 6 1.1 MBq/mg (4.91 6 0.03 mCi/mg). In vitro assays demonstrated that 89 Zr-DFO-J591 had an initial immunoreactive fraction of 0.95 6 0.03 and remained active for up to 7 d. In vivo biodistribution experiments revealed high, target-specific uptake of 89 Zr-DFO-J591 in LNCaP tumors after 24, 48, 96, and 144 h (34.4 6 3.2 percentage injected dose per gram [%ID/g], 38.0 6 6.2 %ID/g, 40.4 6 4.8 %ID/g, and 45.8 6 3.2 %ID/g, respectively). ImmunoPET studies also showed that 89 Zr-DFO-J591 provides excellent image contrast, with tumorto-muscle ratios greater than 20, for the delineation of LNCaP xenografts between 48 and 144 h after administration. Conclusion: These studies demonstrate that 89 Zr-DFO-labeled mAbs show exceptional promise as radiotracers for immunoPET of human cancers. 89 Zr-DFO-J591 displays high tumor-to-background tissue contrast in immunoPET and can be used to delineate and quantify PSMA-positive prostate tumors in vivo.

Most cancers are characterized by multiple molecular alterations, but identification of the key proteins involved in these signaling pathways is currently beyond reach. We show that the inhibitor PU-H71 preferentially targets tumor-enriched Hsp90 complexes and affinity captures Hsp90-dependent oncogenic client proteins. We have used PU-H71 affinity capture to design a proteomic approach that, when combined with bioinformatic pathway analysis, identifies dysregulated signaling networks and key oncoproteins in chronic myeloid leukemia. The identified interactome overlaps with the well-characterized altered proteome in this cancer, indicating that this method can provide global insights into the biology of individual tumors, including primary patient specimens. In addition, we show that this approach can be used to identify previously uncharacterized oncoproteins and mechanisms, potentially leading to new targeted therapies. We further show that the abundance of the PU-H71-enriched Hsp90 species, which is not dictated by Hsp90 expression alone, is predictive of the cell’s sensitivity to Hsp90 inhibition.