Structure-activity relationship-guided development of retinoic acid receptor-related orphan receptor gamma (RORγ)-selective inverse agonists with a phenanthridin-6(5H)-one skeleton from a liver X receptor ligand

Design, Synthesis, and Biological Activity of Silicon-Containing Carboxamide Fungicides

Bioisosteric silicon replacement has proven to be a valuable strategy in the design of bioactive molecules for crop protection and drug development. Twenty-one novel carboxamides possessing a silicon-containing biphenyl moiety were synthesized and tested for their antifungal activity and succinate dehydrogenase (SDH) enzymatic inhibitory activity. Among these novel succinate dehydrogenase inhibitors (SDHIs), compounds 3a, 3e, 4l, and 4o possessing appropriate clog P and topological polar surface area values showed excellent inhibitory effects against Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytis cinerea, and Fusarium graminearum at 10 mg/L in vitro, and the EC50 values of 4l and 4o were 0.52 and 0.16 mg/L against R. solani and 0.066 and 0.054 mg/L against S. sclerotiorum, respectively, which were superior to those of Boscalid. Moreover, compound 3a demonstrated superior SDH enzymatic inhibitory activity (IC50 = 8.70 mg/L), exhibiting 2.54-fold the potency of Boscalid (IC50 = 22.09 mg/L). Docking results and scanning electron microscope experiments revealed similar mode of action between compound 3a and Boscalid. The new silicon-containing carboxamide 3a is a promising SDHI candidate that deserves further investigation.

Silicon switch: Carbon-silicon Bioisosteric replacement as a strategy to modulate the selectivity, physicochemical, and drug-like properties in anticancer pharmacophores

Bioisosterism is one of the leading strategies in medicinal chemistry for the design and modification of drugs, consisting in replacing an atom or a substituent with a different atom or a group with similar chemical properties and an inherent biocompatibility. The objective of such an exercise is to produce a diversity of molecules with similar behavior while enhancing the desire biological and pharmacological properties, without inducing significant changes to the chemical framework. In drug discovery and development, the optimization of the absorption, distribution, metabolism, elimination, and toxicity (ADMETox) profile is of paramount importance. Silicon appears to be the right choice as a carbon isostere because they possess very similar intrinsic properties. However, the replacement of a carbon by a silicon atom in pharmaceuticals has proven to result in improved efficacy and selectivity, while enhancing physicochemical properties and bioavailability. The current review discusses how silicon has been strategically introduced to modulate drug-like properties of anticancer agents, from a molecular design strategy, biological activity, computational modeling, and structure-activity relationships perspectives.

Facile synthesis, crystal structure, quantum calculation, and biological evaluations of novel selenenyl sulfide compounds as potential agrochemicals

BACKGROUND

In order to design compounds with fresh molecular skeleton to break through the limitation of available agrochemicals, a series of 36 novel selenenyl sulfide compounds were chemically synthesized, and their biological activities were fully evaluated against tobacco mosaic virus (TMV), 14 plant pathogenic fungi, three insect species and plant acetohydroxyacid synthase (AHAS).

RESULTS

All the target compounds were characterized by proton nuclear magnetic resonance (¹ H-NMR), carbon-13 (¹³ C)-NMR, selenium-77 (⁷⁷ Se)-NMR, and high-resolution mass spectrometry (HRMS). The crystal structure of 10j indicated that the Se-S bond was successfully constructed. Compounds 10d, 10h, 10s, 10u, 10aa, 10ac, 10ae, 10ag, and 10ai exhibited 40%, 43%, 39%, 41%, 47%, 46%, 47%, 42%, and 39% anti-TMV activities at 500 mg L^-1 , better than that of ribavirin. The median effective concentration (EC₅₀ ) against Sclerotinia sclerotiorum of 10ac was 6.69 mg L^-1 and EC₅₀ values against Physalospora piricola and Pyricularia grisea of 10z were 12.25 mg L^-1 and 15.27 mg L^-1 , respectively, superior to the corresponding values of chlorothalonil. Compounds 10c and 10v demonstrated 100% larvicidal activity against Culex pipiens pallens at 5 mg L^-1 , while 10a displayed 100% insecticidal activity against Mythimna separata at 200 mg L^-1 . Compounds 10c, 10j, and 10o showed > 60% inhibitions against plant AHAS at 10 μmol L^-1 . From the quantum calculation, highest occupied molecular orbital (HOMO) was considered as a factor that affects the anti-TMV activity.

CONCLUSION

The preliminary results suggested that more efforts should be devoted to exploring the selenenyl sulfides for the discovery of new leads of antiviral agent, fungicide, insecticide or AHAS inhibitors as potential agrochemicals for crop protection. © 2023 Society of Chemical Industry.

Review of in silico studies dedicated to the nuclear receptor family: Therapeutic prospects and toxicological concerns

Being in the center of both therapeutic and toxicological concerns, NRs are widely studied for drug discovery application but also to unravel the potential toxicity of environmental compounds such as pesticides, cosmetics or additives. High throughput screening campaigns (HTS) are largely used to detect compounds able to interact with this protein family for both therapeutic and toxicological purposes. These methods lead to a large amount of data requiring the use of computational approaches for a robust and correct analysis and interpretation. The output data can be used to build predictive models to forecast the behavior of new chemicals based on their in vitro activities. This atrticle is a review of the studies published in the last decade and dedicated to NR ligands in silico prediction for both therapeutic and toxicological purposes. Over 100 articles concerning 14 NR subfamilies were carefully read and analyzed in order to retrieve the most commonly used computational methods to develop predictive models, to retrieve the databases deployed in the model building process and to pinpoint some of the limitations they faced.

Efficient Lead Finding, Activity Enhancement and Preliminary Selectivity Control of Nuclear Receptor Ligands Bearing a Phenanthridinone Skeleton

Background: Nuclear receptors (NRs) are considered as potential drug targets because they control diverse biological functions. However, steroidal ligands for NRs have the potential to cross-react with other nuclear receptors, so development of non-steroidal NR ligands is desirable to obtain safer agents for clinical use. We anticipated that efficient lead finding and enhancement of activity toward nuclear receptors recognizing endogenous steroidal ligands might be achieved by exhaustive evaluation of a steroid surrogate library coupled with examination of structure-activity relationships (SAR). Method: We evaluated our library of RORs (retinoic acid receptor-related orphan receptors) inverse agonists and/or PR (progesterone receptor) antagonists based on the phenanthridinone skeleton for antagonistic activities toward liver X receptors (LXRs), androgen receptor (AR) and glucocorticoid receptor (GR) and examined their SAR. Results: Potent LXRβ, AR, and GR antagonists were identified. SAR studies led to a potent AR antagonist (IC₅₀: 0.059 μM). Conclusions: Our approach proved effective for efficient lead finding, activity enhancement and preliminary control of selectivity over other receptors. The phenanthridinone skeleton appears to be a promising steroid surrogate.

Novel Nonsteroidal Progesterone Receptor (PR) Antagonists with a Phenanthridinone Skeleton

The progesterone receptor (PR) plays an important role in various physiological systems, including female reproduction and the central nervous system, and PR antagonists are thought to be effective not only as contraceptive agents and abortifacients but also in the treatment of various diseases, including hormone-dependent cancers and endometriosis. Here, we identified phenanthridin-6(5H)-one derivatives as a new class of PR antagonists and investigated their structure-activity relationships. Among the synthesized compounds, 37, 40, and 46 exhibited very potent PR antagonistic activity with high selectivity for PR over other nuclear receptors. These compounds are structurally distinct from other nonsteroidal PR antagonists, including cyanoaryl derivatives, and should be useful for further studies of the clinical utility of PR antagonists.

Discovery of Retinoic Acid-Related Orphan Receptor γt Inverse Agonists via Docking and Negative Image-Based Screening

Retinoic acid-related orphan receptor γt (RORγt) has a vital role in the differentiation of T-helper 17 (TH17) cells. Potent and specific RORγt inverse agonists are sought for treating TH17-related diseases such as psoriasis, rheumatoid arthritis, and type 1 diabetes. Here, the aim was to discover novel RORγt ligands using both standard molecular docking and negative image-based screening. Interestingly, both of these in silico techniques put forward mostly the same compounds for experimental testing. In total, 11 of the 34 molecules purchased for testing were verified as RORγt inverse agonists, thus making the effective hit rate 32%. The pIC₅₀ values for the compounds varied from 4.9 (11 μM) to 6.2 (590 nM). Importantly, the fact that the verified hits represent four different cores highlights the structural diversity of the RORγt inverse agonism and the ability of the applied screening methodologies to facilitate much-desired scaffold hopping for drug design.

Palladium-catalyzed intramolecular C–H arylation of 2-halo-N-Boc-N-arylbenzamides for the synthesis of N–H phenanthridinones

A palladium catalyzed synthesis of N–H phenanthridinones was developed via C–H arylation. The protocol gives phenanthridinones regioselectively by one-pot reaction without deprotection. It exhibits broad substrate scope and affords targets in up to 95% yields. Importantly, it could be applied for the less reactive o-chlorobenzamides.

Pd(t-Bu₃P)₂/KOAc proved to be a good combination for one-pot synthesis of N–H phenanthridinones with up to 95% yield.

Identification of novel quinazolinedione derivatives as RORγt inverse agonist

Novel small molecules were synthesized and evaluated as retinoic acid receptor-related orphan receptor-gamma t (RORγt) inverse agonists for the treatment of inflammatory and autoimmune diseases. A hit compound, 1, was discovered by high-throughput screening of our compound library. The structure-activity relationship (SAR) study of compound 1 showed that the introduction of a chlorine group at the 3-position of 4-cyanophenyl moiety increased the potency and a 3-methylpentane-1,5-diamide linker is favorable for the activity. The carbazole moiety of 1 was also optimized; a quinazolinedione derivative 18i suppressed the increase of IL-17A mRNA level in the lymph node of a rat model of experimental autoimmune encephalomyelitis (EAE) upon oral administration. These results indicate that the novel quinazolinedione derivatives have great potential as orally available small-molecule RORγt inverse agonists for the treatment of Th17-driven autoimmune diseases. A U-shaped bioactive conformation of this chemotype with RORγt protein was also observed.

Progress in the medicinal chemistry of silicon: C/Si exchange and beyond

Application of silyl functionalities is one of the most promising strategies among various ‘elements chemistry’ approaches for the development of novel and distinctive drug candidates. Replacement of one or more carbon atoms of various biologically active compounds with silicon (so-called sila-substitution) has been intensively studied for decades, and is often effective for alteration of activity profile and improvement of metabolic profile. In addition to simple C/Si exchange, several novel approaches for utilizing silicon in medicinal chemistry have been suggested in recent years, focusing on the intrinsic differences between silicon and carbon. Sila-substitution offers great potential for enlarging the chemical space of medicinal chemistry, and provides many options for structural development of drug candidates.

Recent progress on nuclear receptor RORγ modulators

The retinoic acid receptor-related orphan receptor RORγ plays key roles in the development and differentiation of TH17 cells, and thus in IL-17 expression, thymocyte development and regulation of metabolism. With the recent progression into phase 2 clinical trials of both oral and topically administered inverse agonists, and with others close behind, there is significant interest in the discovery of RORγ modulators. This digest covers key developments around RORγ agonists, antagonists and inverse agonists; orthosteric and allosteric binders; and aims to summarize the available information concerning the potential utility of RORγ modulators.

Expanding the chemical space of hydrophobic pharmacophores: the role of hydrophobic substructures in the development of novel transcription modulators

Interactions between biologically active compounds and their targets often involve hydrophobic interactions, and hydrophobicity also influences the pharmacokinetic profile.

Discovery of Biaryl Amides as Potent, Orally Bioavailable, and CNS Penetrant RORγt Inhibitors

A novel series of biaryl amides was identified as RORγt inhibitors through core replacement of a starting hit 1. Structure-activity relationship exploration on the biaryl moiety led to discovery of potent RORγt inhibitors with good oral bioavailability and CNS penetration. Compounds 9a and 9g demonstrated excellent in vivo efficacy in EAE mice dose dependently with once daily oral administration.