A Structural and in Vitro Characterization of Asoprisnil: A Selective Progesterone Receptor Modulator

Abstract

Selective progesterone receptor modulators (SPRMs) have been suggested as therapeutic agents for treatment of gynecological disorders. One such SPRM, asoprisnil, was recently in clinical trials for treatment of uterine fibroids and endometriosis. We present the crystal structures of progesterone receptor (PR) ligand binding domain complexed with asoprisnil and the corepressors nuclear receptor corepressor (NCoR) and SMRT. This is the first report of steroid nuclear receptor crystal structures with ligand and corepressors. These structures show PR in a different conformation than PR complexed with progesterone (P4). We profiled asoprisnil in PR-dependent assays to understand further the PR-mediated mechanism of action. We confirmed previous findings that asoprisnil demonstrated antagonism, but not agonism, in a PR-B transfection assay and the T47D breast cancer cell alkaline phosphatase activity assay. Asoprisnil, but not RU486, weakly recruited the coactivators SRC-1 and AIB1. However, asoprisnil strongly recruited the corepressor NCoR in a manner similar to RU486. Unlike RU486, NCoR binding to asoprisnil-bound PR could be displaced with equal affinity by NCoR or TIF2 peptides. We further showed that it weakly activated T47D cell gene expression of Sgk-1 and PPL and antagonized P4-induced expression of both genes. In rat leiomyoma ELT3 cells, asoprisnil demonstrated partial P4-like inhibition of cyclooxygenase (COX) enzymatic activity and COX-2 gene expression. In the rat uterotrophic assay, asoprisnil demonstrated no P4-like ability to oppose estrogen. Our data suggest that asoprisnil differentially recruits coactivators and corepressors compared to RU486 or P4, and this specific cofactor interaction profile is apparently insufficient to oppose estrogenic activity in rat uterus.

Stabilization of protein–protein interactions by small molecules

“…It displays mostly antagonist behavior but also weak agonist effects in fluorescence polarization and mammalian twohybrid assays. Two crystal structures of asoprisnil in the ligandbinding pocket of the PR with SMRT or N-CoR, respectively, were solved showing that the molecule is, with its hydrophilic NOH group, in direct contact with the lipophilic side-chain of Leu2263 in the SMRT peptide (3.16 Å ) [96]. Hence, changing the NOH group could lead to hydrophobic interaction between co-repressor and small molecule.…”

Rational design and synthesis of novel anti-prostate cancer agents bearing a 3,5-bis-trifluoromethylphenyl moiety

“…[8][9][10][11][12] Reagents and conditions: All newly synthesised compounds were evaluated for their antiproliferative effect in an in vitro 2D monolayer assay using four human prostate cancer cell lines ( Table 1, absolute IC50 in µM). LNCaP, 5 VCaP and 22Rv1 cell lines exhibit some androgen sensitivity, whereas DU-145 is hormone-insensitive (Supporting Information, section S.3).…”

“…4 The crystal structure of the progesterone receptor in its open antagonist form (PDB ID: 2OVM) was used as template (54% sequence identity with the human AR). 5 Docking of (R)-bicalutamide, enzalutamide and of the newly designed modifications was performed in the ligand binding domain (LBD) of the AR model using Plants docking software. 6 The predicted binding mode found for the parent compounds revealed the presence of free occupational space in the model structure in proximity to helix 12.…”

Recent advances in structure of progestins and their binding to progesterone receptors

“…On the ground of PR-structure knowledge, different types of progesterone antagonists have been described 58 . These molecules have been identified by their effect as pure antagonists, which avoid the binding to the PRE (e.g.…”