Novel AR/AR-V7 and Mnk1/2 Degrader, VNPP433-3β: Molecular Mechanisms of Action and Efficacy in AR-Overexpressing Castration Resistant Prostate Cancer In Vitro and In Vivo Models

Abstract

Prostate cancer (PCa) relies in part on AR-signaling for disease development and progression. Earlier, we developed drug candidate galeterone, which advanced through phase 2-clinical trials in treating castration-resistant PCa (CRPC). Subsequently, we designed, synthesized, and evaluated next-generation galeterone-analogs including VNPP433-3β which is potently efficacious against pre-clinical models of PCa. This study describes the mechanism of action of VNPP433-3β that promotes degradation of full-length AR (fAR) and its splice variant AR-V7 besides depleting MNK1/2 in in vitro and in vivo CRPC models that stably overexpresses fAR. VNPP433-3β directly engages AR within the cell and promotes proteasomal degradation of fAR and its splice variant AR-V7 by enhancing the interaction of AR with E3 ligases MDM2/CHIP but disrupting AR-HSP90 binding. Next, VNPP433-3β decreases phosphorylation of 4EBP1 and abates binding of eIF4E and eIF4G to 5′ cap of mRNA by depleting MNK1/2 with consequent depletion of phosphorylated eIF4E. Finally, RNA-seq demonstrates modulation of multiple pathways that synergistically contribute to PCa inhibition. Therefore, VNPP433-3β exerts its antitumor effect by imposing 1) transcriptional regulation of AR and AR-responsive oncogenes 2) translational regulation by disrupting mRNA-5′cap-dependent translation initiation, 3) reducing AR half-life through enhanced proteasomal degradation in vitro and AR-overexpressing tumor xenografts in vivo.

Tumor suppressive miR-99b-5p as an epigenomic regulator mediating mTOR/AR/SMARCD1 signaling axis in aggressive prostate cancer

“…Also, AR-V7 variant lacks the ligand binding domain (LBD), and therefore is resistant to the AR antagonists (i.e. abiraterone and enzalutamide), which are the currently available therapy for CRPC (55). To solve this problem, drugs/compounds that causes the degradation of both full-length AR and AR-V7 are currently under development (56).…”

VNLG-152R and its deuterated analogs potently inhibit/repress triple/quadruple negative breast cancer of diverse racial origins in vitro and in vivo by upregulating E3 Ligase Synoviolin 1 (SYVN1) and inducing proteasomal degradation of MNK1/2

“…The cells were lysed in radioimmunoprecipitation assay (RIPA) buffer supplemented with 1x protease inhibitors (Roche, Indianapolis, IN, USA), phosphatase inhibitors (Thermo Scientific, Waltham, MA, USA), 1 mmol/L EDTA and 1 mmol/L PMSF (Sigma) and immunoblotted as described earlier ( 24 , 25 ). Immunoprecipitation of MNK1 was performed as reported previously using MNK1 primary antibody ( 26 , 27 ). All fine chemicals were purchased from Sigma-Aldrich, St. Louis, MO.…”

Therapeutic Approaches to Targeting Androgen Receptor Splice Variants

“…As a result, researchers have developed a galeterone-derivative drug candidate, VNPP433-3β, effective against CRPC by targeting AR-FL and AR-Vs. VNPP433-3β promotes the degradation of full-length AR and AR-V7 while also inhibiting MNK1/2, leading to reduced phosphorylation of eIF4E and mRNA translation. Preclinical investigation with cell lines (CWR22Rv1 and LNCaP) on this novel drug compound has shown promising results [ 32 ].…”