Design, synthesis and structure-activity relationships of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as novel HIV-1 capsid inhibitors with promising antiviral activities

Design, synthesis, and antiviral activity of phenylalanine derivatives as HIV-1 capsid inhibitors

The HIV-1 Capsid (CA) is considered as a promising target for the development of potent antiviral drugs, due to its multiple roles during the viral life cycle. Herein, we report the design, synthesis, and antiviral activity evaluation of series of novel phenylalanine derivatives as HIV-1 CA protein inhibitors. Among them, 4-methoxy-N-methylaniline substituted phenylalanine (II-13c) and indolin-5-amine substituted phenylalanine (V-25i) displayed exceptional anti-HIV-1 activity with the EC₅₀ value of 5.14 and 2.57 μM respectively, which is slightly weaker than that of lead compound PF-74 (EC₅₀ = 0.42 μM). Besides, surface plasmon resonance (SPR) binding assay demonstrated II-13c and V-25i prefer to combine with CA hexamer rather than monomer, which is similar to PF-74. Subsequently, molecular dynamics simulation (MD) revealed potential interactions between representative compounds with HIV-1 CA hexamer. Overall, this work laid a solid foundation for further structural optimization to discover novel promising HIV-1 CA inhibitors.

Design, synthesis, and mechanistic investigations of phenylalanine derivatives containing a benzothiazole moiety as HIV-1 capsid inhibitors with improved metabolic stability

Further clinical development of PF74, a lead compound targeting HIV-1 capsid, is impeded by low antiviral activity and inferior metabolic stability. By modifying the benzene (region I) and indole of PF74, we identified two potent compounds (7m and 7u) with significantly improved metabolic stability. Compared to PF74, 7u displayed greater metabolic stability in human liver microsomes (HLMs) with half-life (t_1/2) 109-fold that of PF74. Moreover, mechanism of action (MOA) studies demonstrated that 7m and 7u effectively mirrored the MOA of compounds that interact within the PF74 interprotomer pocket, showing direct and robust interactions with recombinant CA, and 7u displaying antiviral effects in both the early and late stages of HIV-1 replication. Furthermore, MD simulation corroborated that 7u was bound to the PF74 binding site, and the results of the online molinspiration software predicted that 7m and 7u had desirable physicochemical properties. Unexpectedly, this series of compounds exhibited better antiviral activity than PF74 against HIV-2, represented by compound 7m whose anti-HIV-2 activity was almost 5 times increased potency over PF74. Therefore, we have rationally redesigned the PF74 chemotype to inhibitors with novel structures and enhanced metabolic stability in this study. We hope that these new compounds can serve as a blueprint for developing a new generation of HIV treatment regimens.

An overview of triazoloquinazolines: Pharmacological significance and recent developments

Nitrogen heterocyclic rings have participated to constitute most of the drugs and several pharmacologically related compounds. The existence of such hetero atoms/groups in heterocyclic systems privileged specificities in their biological objectives. Particularly, quinazoline and triazole are biologically imperative platforms known to be linked with various pharmacological activities. Some of the prominent pharmacological responses ascribed to these systems are analgesic, antiinflammatory, anticonvulsant, hypnotic, antihistaminic, antihypertensive, anticancer, antimicrobial, antitubercular, antiviral and antimalarial activities. This diversity in the pharmacological outputs for both triazole and quinazoline systems has encouraged the medicinal chemistry researchers to create several chemical routes aiming at the incorporation of two rings in one molecule named triazoloquinazoline system. This system has shown multiple potential activities against numerous targets. Correlation the specific structural features of triazoloquinazoline system with its pharmacological purposes has successively been achieved by performing several pharmacological examinations and structure-activity relationship studies. The development of triazoloquinazoline derivatives and the understanding of their pharmacological targets offer opportunities for novel therapeutics. This review mainly emphases on the medicinal chemistry aspects of triazoloquinazolines including synthesis, reactivity, biological activity and structure activity relationship studies (SARs). Moreover, this review collates literature reported by researchers on triazoquinazolines and provides detailed attention on their analogs pharmacological activities in the perspective of drug development and discovery.

Stitching Triazoles to Arenes via a Transition Metal-Free Aryne Diels-Alder/1,3-Prototropic Shift/Dehydrobromination Cascade

The 1,2,3-triazole-fused polyaromatic frameworks are traditionally obtained through transition metal-catalyzed C-H/C-X arylation of the preinstalled triazoles at a very high temperature. Herein, a transition metal-free direct synthesis via an aryne Diels-Alder/1,3-prototropic shift/dehydrobromination cascade is reported. This method gives access to triazole-fused aromatics as well as the corresponding dihydrocarbocycles under mild reaction conditions.

CDATA[Recent Advances in the Development of 1,2,3-Triazole-containing Derivatives as Potential Antifungal Agents and Inhibitors of Lanoster ol 14α-Demethylase

1,2,3-Triazole, a five-membered heterocyclic nucleus, is widely recognized as a key chromophore of great value in medicinal chemistry for delivering compounds possessing innumerable biological activities, including antimicrobial, antitubercular, antidiabetic, antiviral, antitumor, antioxidants, and anti-inflammatory activities. Mainly, in the past years, diverse conjugates carrying this biologically valuable core have been reported due to their attractive fungicidal potential and potent effects on various infective targets. Hence, hybridization of 1,2,3-triazole with other antimicrobial pharmacophores appears to be a judicious strategy to develop new effective anti-fungal candidates to combat the emergence of drug-sensitive and drug-resistant infectious diseases. Thus, the current review highlights the recent advances of this promising category of 1,2,3-triazole-containing hybrids incorporating diverse varieties of bioactive heterocycles such as conozole, coumarin, imidazole, benzimidazole, pyrazole, indole, oxindole, chromene, pyrane, quinazoline, chalcone, isoflavone, carbohydrates, and amides. It underlies their inhibition behavior against a wide array of infectious fungal species during 2015-2020.

Recent studies of nitrogen containing heterocyclic compounds as novel antiviral agents: A review

N-heterocycles are important, not only because of their abundance, but above all because of their chemical, biological and technical significance. They play an important role in biological investigation such as anticancer, antiinflammatory, antibacterial, antiviral, anti-tumor, antidiabetic, etc. In this study, we focused on examining synthesized some 5- or 6-ring N-heterocyclic compounds that showed the antiviral activity in last 5 years, and investigation of these compounds structure-activity relationship studies. This review will be useful to scientists in research fields of organic synthesis, medicinal chemistry, and pharmacology.

Rapid Optimization of the Metabolic Stability of a Human Immunodeficiency Virus Type-1 Capsid Inhibitor Using a Multistep Computational Workflow

Poor metabolic stability of the human immunodeficiency virus type-1 (HIV-1) capsid (CA) inhibitor PF-74 is a major concern in its development toward clinical use. To improve on the metabolic stability, we employed a novel multistep computationally driven workflow, which facilitated the rapid design of improved PF-74 analogs in an efficient manner. Using this workflow, we designed three compounds that interact specifically with the CA interprotomer pocket, inhibit HIV-1 infection, and demonstrate enantiomeric preference. Moreover, using this workflow, we were able to increase the metabolic stability 204-fold in comparison to PF-74 in only three analog steps. These results demonstrate our ability to rapidly design CA compounds using a novel computational workflow that has improved metabolic stability over the parental compound. This workflow can be further applied to the redesign of PF-74 and other promising inhibitors with a stability shortfall.

Design, Synthesis and Characterization of HIV-1 CA-Targeting Small Molecules: Conformational Restriction of PF74

Small molecules targeting the PF74 binding site of the HIV-1 capsid protein (CA) confer potent and mechanistically unique antiviral activities. Structural modifications of PF74 could further the understanding of ligand binding modes, diversify ligand chemical classes, and allow identification of new variants with balanced antiviral activity and metabolic stability. In the current work, we designed and synthesized three series of PF74-like analogs featuring conformational constraints at the aniline terminus or the phenylalanine carboxamide moiety, and characterized them using a biophysical thermal shift assay (TSA), cell-based antiviral and cytotoxicity assays, and in vitro metabolic stability assays in human and mouse liver microsomes. These studies showed that the two series with the phenylalanine carboxamide moiety replaced by a pyridine or imidazole ring can provide viable hits. Subsequent SAR identified an improved analog 15 which effectively inhibited HIV-1 (EC₅₀ = 0.31 μM), strongly stabilized CA hexamer (ΔTm = 8.7 °C), and exhibited substantially enhanced metabolic stability (t_1/2 = 27 min for 15 vs. 0.7 min for PF74). Metabolic profiles from the microsomal stability assay also indicate that blocking the C5 position of the indole ring could lead to increased resistance to oxidative metabolism.

An insight on medicinal aspects of novel HIV-1 capsid protein inhibitors

A capsid is the protein shell of a virus, encircling its genetic material. The HIV capsid is erected from a single protein, known as capsid protein. The capsid of HIV-1 significantly involved in many processes of the virus life cycle, which makes it as a novel target for the new inhibitors. Recently many novel HIV-1 inhibitors binding to capsid proteins have been reported successfully. Most of these inhibitors can inhibit or accelerate the disassembly or assembly of the capsid, and some of them can inhibit reverse transcription. Unfortunately, none of them are currently approved by U.S. FDA. However, GS-6207, an inhibitor binds to the NTD-CTD interface with potent antiviral activity and the long metabolic cycle, is expected to be the first approved drug targeting HIV-1 capsid. Herein, we provide a concise report focusing on the recent prospective of HIV-1 capsid inhibitors in medicinal chemistry in order to enlighten drug design.

Novel PF74-like small molecules targeting the HIV-1 capsid protein: Balance of potency and metabolic stability

Of all known small molecules targeting human immunodeficiency virus (HIV) capsid protein (CA), PF74 represents by far the best characterized chemotype, due to its ability to confer antiviral phenotypes in both early and late phases of viral replication. However, the prohibitively low metabolic stability renders PF74 a poor antiviral lead. We report herein our medicinal chemistry efforts toward identifying novel and metabolically stable small molecules targeting the PF74 binding site. Specifically, we replaced the inter-domain-interacting, electron-rich indole ring of PF74 with less electron-rich isosteres, including imidazolidine-2,4-dione, pyrimidine-2,4-dione, and benzamide, and identified four potent antiviral compounds (10, 19, 20 and 26) with markedly improved metabolic stability. Compared to PF74, analog 20 exhibited similar submicromolar potency, and much longer (51-fold) half-life in human liver microsomes (HLMs). Molecular docking corroborated that 20 binds to the PF74 binding site, and revealed distinct binding interactions conferred by the benzamide moiety. Collectively, our data support compound 20 as a promising antiviral lead.

Synthesis and antibiofilm activity of 1,2,3-triazole-pyridine hybrids against methicillin-resistant Staphylococcus aureus (MRSA)

Antibiotic-resistant bacteria are emerging at an alarming rate, posing a potential threat to human health. A series of 1,2,3-triazole-pyridine hybrids were synthesised as promising antibiofilm agents against planktonic and sessile MRSA.

1,2,3-Triazole hybrids with anti-HIV-1 activity

The human immunodeficiency virus type 1 (HIV-1) is the major etiological agent responsible for the acquired immunodeficiency syndrome (AIDS), which is a serious infectious disease and remains one of the most prevalent problems at present. Currently, combined antiretroviral therapy is the primary modality for the treatment and management of HIV/AIDS, but the long-term use can result in major drawbacks such as the development of multidrug-resistant viruses and multiple side effects. 1,2,3-Triazole is the common framework in the development of new drugs, and its derivatives have the potential to inhibit various HIV-1 enzymes such as reverse transcriptase, integrase, and protease, consequently possessing a potential anti-HIV-1 activity. This review covers the recent advances regarding the 1,2,3-triazole hybrids with potential anti-HIV-1 activity; it focuses on the chemical structures, structure-activity relationship, and mechanisms of action, covering articles published from 2010 to 2020.

HIV-1 Maturation: Lessons Learned from Inhibitors

Since the emergence of HIV and AIDS in the early 1980s, the development of safe and effective therapies has accompanied a massive increase in our understanding of the fundamental processes that drive HIV biology. As basic HIV research has informed the development of novel therapies, HIV inhibitors have been used as probes for investigating basic mechanisms of HIV-1 replication, transmission, and pathogenesis. This positive feedback cycle has led to the development of highly effective combination antiretroviral therapy (cART), which has helped stall the progression to AIDS, prolong lives, and reduce transmission of the virus. However, to combat the growing rates of virologic failure and toxicity associated with long-term therapy, it is important to diversify our repertoire of HIV-1 treatments by identifying compounds that block additional steps not targeted by current drugs. Most of the available therapeutics disrupt early events in the replication cycle, with the exception of the protease (PR) inhibitors, which act at the virus maturation step. HIV-1 maturation consists of a series of biochemical changes that facilitate the conversion of an immature, noninfectious particle to a mature infectious virion. These changes include proteolytic processing of the Gag polyprotein by the viral protease (PR), structural rearrangement of the capsid (CA) protein, and assembly of individual CA monomers into hexamers and pentamers that ultimately form the capsid. Here, we review the development and therapeutic potential of maturation inhibitors (MIs), an experimental class of anti-HIV-1 compounds with mechanisms of action distinct from those of the PR inhibitors. We emphasize the key insights into HIV-1 biology and structure that the study of MIs has provided. We will focus on three distinct groups of inhibitors that block HIV-1 maturation: (1) compounds that block the processing of the CA-spacer peptide 1 (SP1) cleavage intermediate, the original class of compounds to which the term MI was applied; (2) CA-binding inhibitors that disrupt capsid condensation; and (3) allosteric integrase inhibitors (ALLINIs) that block the packaging of the viral RNA genome into the condensing capsid during maturation. Although these three classes of compounds have distinct structures and mechanisms of action, they share the ability to block the formation of the condensed conical capsid, thereby blocking particle infectivity.

Novel HIV-1 capsid-targeting small molecules of the PF74 binding site

The PF74 binding site in HIV-1 capsid protein (CA) is a compelling antiviral drug target. Although PF74 confers mechanistically distinct antiviral phenotypes by competing against host factors for CA binding, it suffers from prohibitively low metabolic stability. Therefore, there has been increasing interest in designing novel sub-chemotypes of PF74 with similar binding mode and improved metabolic stability. We report herein our efforts to explore the inter-domain interacting indole moiety for designing novel CA-targeting small molecules. Our design includes simple substitution on the indole ring, and more importantly, novel sub-chemotypes with the indole moiety replaced with a few less electron-rich rings. All 56 novel analogs were synthesized and evaluated for antiviral activity, cytotoxicity, and impact on CA hexamer stability. Selected analogs were tested for metabolic stability in liver microsomes. Molecular modeling was performed to verify compound binding to the PF74 site. In the end, 5-hydroxyindole analogs (8,9 and 12) showed improved potency (up to 20-fold) over PF74. Of the novel sub-chemotypes, α- and β-naphthyl analogs (33 and 27) exhibited sub micromolar antiviral potencies comparable to that of PF74. Interestingly, although only moderately inhibiting HIV-1 (single-digit micromolar EC₅₀s), analogs of the 2-indolone sub-chemotype consistently lowered the melting point (T_m) of CA hexamers, some with improved metabolic stability over PF74.

Chemical profiling of HIV-1 capsid-targeting antiviral PF74

The capsid protein (CA) of HIV-1 plays essential roles in multiple steps of the viral replication cycle by assembling into functional capsid core, controlling the kinetics of uncoating and nuclear entry, and interacting with various host factors. Targeting CA represents an attractive yet underexplored antiviral approach. Of all known CA-targeting small molecule chemotypes, the peptidomimetic PF74 is particularly interesting because it binds to the same pocket used by a few important host factors, resulting in highly desirable antiviral phenotypes. However, further development of PF74 entails understanding its pharmacophore and mitigating its poor metabolic stability. We report herein the design, synthesis, and evaluation of a large number of PF74 analogs aiming to provide a comprehensive chemical profiling of PF74 and advance the understanding on its detailed binding mechanism and pharmacophore. The analogs, containing structural variations mainly in the aniline domain and/or the indole domain, were assayed for their effect on stability of CA hexamers, antiviral activity, and cytotoxicity. Selected analogs were also tested for metabolic stability in liver microsomes, alone or in the presence of a CYP3A inhibitor. Collectively, our studies identified important pharmacophore elements and revealed additional binding features of PF74, which could aid in future design of improved ligands to better probe the molecular basis of CA-host factor interactions, design strategies to disrupt them, and ultimately identify viable CA-targeting antiviral leads.

A Review on Recent Advances in Nitrogen-Containing Molecules and Their Biological Applications

The analogs of nitrogen-based heterocycles occupy an exclusive position as a valuable source of therapeutic agents in medicinal chemistry. More than 75% of drugs approved by the FDA and currently available in the market are nitrogen-containing heterocyclic moieties. In the forthcoming decade, a much greater share of new nitrogen-based pharmaceuticals is anticipated. Many new nitrogen-based heterocycles have been designed. The number of novel N-heterocyclic moieties with significant physiological properties and promising applications in medicinal chemistry is ever-growing. In this review, we consolidate the recent advances on novel nitrogen-containing heterocycles and their distinct biological activities, reported over the past one year (2019 to early 2020). This review highlights the trends in the use of nitrogen-based moieties in drug design and the development of different potent and competent candidates against various diseases.

Toward Structurally Novel and Metabolically Stable HIV-1 Capsid-Targeting Small Molecules

HIV-1 capsid protein (CA) plays an important role in many steps of viral replication and represents an appealing antiviral target. Several CA-targeting small molecules of various chemotypes have been studied, but the peptidomimetic PF74 has drawn particular interest due to its potent antiviral activity, well-characterized binding mode, and unique mechanism of action. Importantly, PF74 competes against important host factors for binding, conferring highly desirable antiviral phenotypes. However, further development of PF74 is hindered by its prohibitively poor metabolic stability, which necessitates the search for structurally novel and metabolically stable chemotypes. We have conducted a pharmacophore-based shape similarity search for compounds mimicking PF74. We report herein the analog synthesis and structure-activity relationship (SAR) of two hits from the search, and a third hit designed via molecular hybridization. All analogs were characterized for their effect on CA hexamer stability, antiviral activity, and cytotoxicity. These assays identified three active compounds that moderately stabilize CA hexamer and inhibit HIV-1. The most potent analog (10) inhibited HIV-1 comparably to PF74 but demonstrated drastically improved metabolic stability in liver microsomes (31 min vs. 0.7 min t_1/2). Collectively, the current studies identified a structurally novel and metabolically stable PF74-like chemotype for targeting HIV-1 CA.

Copper(i)-catalysed azide–alkyne cycloaddition and antiproliferative activity of mono- and bis-1,2,3-triazole derivatives

A series of mono- and bis-1,2,3-triazole derivatives were prepared via the copper(i)-catalysed azide–alkyne cycloaddition between substituted aromatic derivatives, comprising one or two terminal alkyne groups and a selection of aromatic azides.