Galeterone and the next generation galeterone analogs, VNPP414 and VNPP433-3β exert potent therapeutic effects in castration-/drug-resistant prostate cancer preclinical models in vitro and in vivo

Abstract

These studies compared the efficacies of our clinical agent galeterone (Gal) and the FDA-approved prostate cancer drug, enzalutamide (ENZ) with two lead next generation galeterone analogs(NGGAs),VNPP414andVNPP433-3β,usingprostatecancer(PC)in vitroandin vivomodels. Antitumor activities of orally administered agents were also assessed in CWR22Rv1 tumor-bearing mice. We demonstrated that Gal and NGGAs degraded AR/AR-V7 and Mnk1/2; blocked cell cycle progression and proliferation of human PC cells; induced apoptosis; inhibited cell migration, invasion, and putative stem cell markers; and reversed the expression of epithelial-to-mesenchymal transition (EMT). In addition, Gal/NGGAs (alone or in combination) also inhibited the growth of ENZ-, docetaxel-, and mitoxantrone-resistant human PC cell lines. The NGGAs exhibited improved pharmacokinetic profiles over Gal in mice. Importantly, in vivo testing showed that VNPP433-3β (at 7.53-fold lower equimolar dose than Gal) markedly suppressed (84% vs. Gal, 47%; p < 0.01) the growthofcastration-resistantPC(CRPC)CWR22Rv1xenografttumors,withnoapparenthosttoxicity. ENZ was ineffective in this CRPC xenograft model. In summary, our findings show that targeting AR/AR-V7 and Mnk1/2 for degradation represents an effective therapeutic strategy for PC/CRPC treatment and supports further development of VNPP433-3β towards clinical investigation.