Design, synthesis and biological evaluation of novel 5-oxo-2-thioxoimidazolidine derivatives as potent androgen receptor antagonists

Discovery of Novel Anti-Resistance AR Antagonists Guided by Funnel Metadynamics Simulation

Androgen receptor (AR) antagonists are widely used for the treatment of prostate cancer (PCa), but their therapeutic efficacy is usually compromised by the rapid emergence of drug resistance. However, the lack of the detailed interaction between AR and its antagonists poses a major obstacle to the design of novel AR antagonists. Here, funnel metadynamics is employed to elucidate the inherent regulation mechanisms of three AR antagonists (hydroxyflutamide, enzalutamide, and darolutamide) on AR. For the first time it is observed that the binding of antagonists significantly disturbed the C-terminus of AR helix-11, thereby disrupting the specific internal hydrophobic contacts of AR-LBD and correspondingly the communication between AR ligand binding pocket (AR-LBP), activation function 2 (AF2), and binding function 3 (BF3). The subsequent bioassays verified the necessity of the hydrophobic contacts for AR function. Furthermore, it is found that darolutamide, a newly approved AR antagonist capable of fighting almost all reported drug resistant AR mutants, can induce antagonistic binding structure. Subsequently, docking-based virtual screening toward the dominant binding conformation of AR for darolutamide is conducted, and three novel AR antagonists with favorable binding affinity and strong capability to combat drug resistance are identified by in vitro bioassays. This work provides a novel rational strategy for the development of anti-resistant AR antagonists.

Length-Dependent Transition from Extended to Folded Shapes in Short Oligomers of an Azetidine-Based α-Amino Acid: The Critical Role of NH···N H-Bonds

Hydrogen bonds (H-bonds) are ubiquitous in peptides and proteins and are central to the stabilization of their structures. Inter-residue H-bonds between non-adjacent backbone amide NH and C=O motifs lead to the well-known secondary structures of helices, turns and sheets, but it is recognized that other H-bonding modes may be significant, including the weak intra-residue H-bond (called a C5 H-bond) that implicates the NH and C=O motifs of the same amino acid residue. Peptide model compounds that adopt stable C5 H-bonds are not readily available and the so-called 2.0₅-helix, formed by successive C5 H-bonds, is an elusive secondary structure. Using a combination of theoretical chemistry and spectroscopic studies in both the gas phase and solution phase, we have demonstrated that derivatives of 3-amino-1-methylazetidine-3-carboxylic acid, Aatc(Me) can form sidechain-backbone N-H···N C6γ H-bonds that accompany-and thereby stabilize-C5 H-bonds. In the capped trimer of Aatc(Me), extended C5/C6γ motifs are sufficiently robust to challenge classical 3₁₀-helix formation in solution and the fully-extended 2.0₅-helix conformer has been characterized in the gas phase. Concurrent H-bonding support for successive C5 motifs is a new axiom for stabilizing the extended backbone secondary structure in short peptides.

Catalytic Asymmetric Synthesis of Chiral Thiohydantoins via Domino Cyclization Reaction of β,γ-Unsaturated α-Ketoester and N,N'-Dialkylthiourea

The first catalytic asymmetric route to synthesize chiral thiohydantoins containing a quaternary stereogenic center has been established utilizing a chiral phosphoric acid-catalyzed domino cyclization reaction of N,N'-dialkyl thioureas with β,γ-unsaturated...

Proposal of novel potent inhibitors against androgen receptor based on ab initio molecular orbital calculations

The androgen receptor (AR), a family of nuclear receptor proteins, stimulates the transcription of androgen-responsive genes. As its abnormal activation can cause the progression of prostate cancer, numerous types of ligands for AR have been developed as promising antagonists for the treatment of prostate cancer. We previously investigated the specific interactions between AR and nine types of existing non-steroidal ligands, using molecular simulations based on molecular mechanics and ab initio fragment molecular orbital methods. The results were confirmed to be comparable to the binding affinities of these ligands observed in experiments. We here propose novel ligands as potent inhibitors against AR and investigate their binding properties to AR, using the same molecular simulations. The results indicate that the most promising ligand binds stronger to AR than the existing non-steroidal ligands, and that our proposed ligand binds strongly to a mutant-type AR, which has drug resistance to the existing non-steroidal ligands.

The design, synthesis and anti-tumor mechanism study of new androgen receptor degrader

Targeted protein degradation using small molecules is a novel strategy for drug development. In order to solve the problem of drug resistance in the treatment of prostate cancer, proteolysis-targeting chimeras (PROTAC) was introduced into the design of anti-prostate cancer derivatives. In this work, we synthesized two series of selective androgen receptor degraders (SARDs) containing the hydrophobic degrons with different linker, and then investigated the structure-activity relationships of these hybrid compounds. Most of the synthesized compounds exhibited moderate to good activity against all the cancer cell lines selected. Among them, compound A9 displayed potent inhibitory activity against LNCaP prostate cancer cell line with IC₅₀ values of 1.75 μM, as well as excellent AR degradation activity. Primary mechanism studies elucidated compound A9 arrested cell cycle at G0/G1 phase and induced a mild apoptotic response in LNCaP cells. Further study indicated that the degradation of AR was mediated through proteasome-mediated process. For all these reasons, compound A9 held promising potential as anti-proliferative agent for the development of highly efficient SARDs for drug-resistance prostate cancer therapies.

Non-Steroidal Androgen Receptor Antagonists and Prostate Cancer: A Survey on Chemical Structures Binding this Fast-Mutating Target

The Androgen Receptor (AR) pathway plays a major role in both the pathogenesis and progression of prostate cancer. In particular, AR is chiefly involved in the development of Castration-Resistant Prostate Cancer (CRPC) as well as in the resistance to the secondgeneration AR antagonist enzalutamide, and to the selective inhibitor of cytochrome P450 17A1 (CYP17A1) abiraterone. Several small molecules acting as AR antagonists have been designed and developed so far, also as a result of the ability of cells expressing this molecular target to rapidly develop resistance and turn pure receptor antagonists into ineffective or event detrimental molecules. This review covers a survey of most promising classes of non-steroidal androgen receptor antagonists, also providing insights into their mechanism of action and efficacy in treating prostate cancer.

Design, Synthesis and Evaluation of Novel Substituted (5-methyl-1H-pyrazol-3-yl)- 1,3,4-oxadiazole as Potent Androgen Receptor Antagonist

BACKGROUND

Androgen Receptor (AR) is one of the highly explored targets for the treatment of prostate cancer. The emergence of point mutation in the Ligand Binding Domain (LBD) of AR has resulted in the development of resistance against AR antagonist. The point mutation T877A, W741L and F876L confer resistance to flutamide, bicalutamide and enzalutamide respectively. There is no AR antagonist in the present clinical set up without resistance. Hence, our aim in this study is to design a novel molecule to overcome the resistance caused by point mutation.

METHODS

Here, we developed novel AR antagonist bearing (5-methyl-1H-pyrazol-3-yl)-1, 3,4-oxadiazole core by rational drug design. The test molecules 8a-h were synthesized from the corresponding dihydrazide compounds 7a-h on treatment with phosphorous oxychloride on reflux conditions. The structure of the molecules was confirmed from spectral data such as IR, 1H-NMR, HRMS and 13C-NMR. The synthesized compounds were screened for cytotoxicity in prostate cancer cell lines LNCaP-FGC and PC3. The confirmation of AR mediated activity of the test compounds was confirmed by gene expression study. The interaction of the best active ligands with mutant AR was predicted and drug design was rationalized through docking studies.

RESULTS

The test compounds 8a-h were synthesized and the structures were conformed using suitable techniques like IR, 1H-NMR, HRMS and 13C-NMR. Among the tested compounds, 8b and 8d showed potent antiproliferative activity against mutant AR cell lines. Further, these compounds significantly decreased the gene expression of prostate cancer biomarkers.

CONCLUSION

In this study, we have identified a potential hit molecule for AR antagonism that could be further developed to obtain a potent clinical candidate.

New 2-Oxoimidazolidine Derivatives: Design, Synthesis and Evaluation of Anti-BK Virus Activities in Vitro

A series of novel 2-oxoimidazolidine derivatives were synthesized and their antiviral activities against BK human polyomavirus type 1 (BKPyV) were evaluated in vitro. Bioassays showed that the synthesized compounds 1-{[(4E)-5-(dichloromethylidene)-2-oxoimidazolidin-4-ylidene]sulfamoyl}piperidine-4-carboxylic acid (5) and N-Cyclobutyl-N'-[(4E)-5-(dichloromethylidene)-2-oxoimidazolidin-4-ylidene]sulfuric diamide (4) exhibited moderate activities against BKPyV (EC₅₀ =5.4 and 5.5 μm, respectively) that are comparable to the standard drug Cidofovir. Compound 5 exhibited the same cytotoxicity in HFF cells and selectivity index (SI₅₀ ) as Cidofovir. The selectivity index of compound 4 is three times less than that of Cidofovir due to the higher toxicity of this compound. Hence, these compounds may be taken as lead compound for further development of novel ant-BKPyV agents.

Discovery and biological evaluation of darolutamide derivatives as inhibitors and down-regulators of wild-type AR and the mutants

Androgen receptor (AR) has been a target of prostate cancer (PC) for nearly six decades. Recently, downregulating or degrading AR and the mutants especially the splice variant 7 (AR-V7) lacking ligand binding domain (LBD) emerged as an advantageous therapeutic approach to overcome drug resistance. Here, the structural modification of darolutamide resulted in the discovery of dual-action AR inhibitors and down-regulators. Unlike other traditional AR antagonists targeting the AR-LBD, compounds 4k and 4b not only inhibit the activities of wt-AR and AR-F876L mutant but also downregulate the protein expression of full-length (AR-full) and AR variant 7 (AR-V7) at mRNA level. In cell proliferation assays, compounds 4k and 4b exhibited better antiproliferative activities than darolutamide and enzalutamide against AR-V7-positive 22Rv1 cells and VCaP cells. In addition, 4k demonstrated better antitumor activity than clinically used enzalutamide in castration-resistant VCaP xenograft model. Collectively, combining the activities of AR inhibition and downregulation, compound 4k is proposed as an advantageous lead compound to disrupt AR signaling and overcome resistance.

Exploring the tetrahydroisoquinoline thiohydantoin scaffold blockade the androgen receptor as potent anti-prostate cancer agents

Prostate cancer (PC) is a major cause of cancer-related male death in worldwide and the identification of new and improved potent anti-PC molecules is constantly required. A novel scaffold of tetrahydroisoquinoline thiohydantoin was rationally designed based on the enzalutamide structures and our pre-work, leading to the discovery of a series of new antiproliferative compounds. Several new analogues displayed improved androgen receptor (AR) antagonistic activity, while maintaining the higher selective toxicity toward LNCaP cells (AR-rich) versus DU145 cells (AR-deficient) compared to enzalutamide. In fact, compound 55 exhibited promising in vitro antitumor activity by impairing AR unclear translocation. More importantly, 55 showed better pharmacokinetic properties compared to the compound 1 reported in our pre-work. These results demonstrate a step towards the development of novel and improved AR antagonists.

Iminoenamine based novel androgen receptor antagonist exhibited anti-prostate cancer activity in androgen independent prostate cancer cells through inhibition of AKT pathway

Treatment by androgen receptor (AR) antagonists is one of the regimens for prostate cancer. The prolonged treatment with AR antagonist leads to the expression of point mutation in the ligand binding domain of the AR. This point mutation causes resistance to AR antagonist by converting them into an agonist. The T887A mutated AR was frequently expressed in androgen independent prostate cancer (AIPC) patients. Through literature survey and molecular modelling, we have identified a novel AR antagonist having a bulky β-iminoenamine BF2 complex scaffold. The tested and standard ligands were screened in AR positive (LNCaP, MCF-7 and MDA-MB-453), AR negative (PC3), and non-cancerous (3T3) cell lines through anti-proliferation assay. The ligand, ARA3 was the most potent molecule among all the tested ligands and was 7.6 folds selective for AR positive cell lines. The mechanism of anti-prostate cancer activity of ARA3 was confirmed by western blot, qPCR, and apoptotic assays in LNCaP (T887A positive AR) cells. Structural activity relationship was derived by correlating the in-vitro and in-silico data. Consequently, we have identified the essential functional groups that could prevent the resistance concerning mutant AR. The ARA3 induces the apoptosis in AIPC cells by preventing the AR mediated activation of AKT pathway. The bicalutamide did not induce the apoptosis because it failed to prevent the AR mediated activation of AKT.