Structure-activity relationships of a novel capsid targeted inhibitor of HIV-1 replication

Clade-Specific Alterations within the HIV-1 Capsid Protein with Implications for Nuclear Translocation

The HIV-1 capsid (CA) protein has emerged as an attractive therapeutic target. However, all inhibitor designs and structural analyses for this essential HIV-1 protein have focused on the clade B HIV-1 (NL4-3) variant. This study creates, overproduces, purifies, and characterizes the CA proteins from clade A1, A2, B, C, and D isolates. These new CA constructs represent novel reagents that can be used in future CA-targeted inhibitor design and to investigate CA proteins’ structural and biochemical properties from genetically diverse HIV-1 subtypes. Moreover, we used surface plasmon resonance (SPR) spectrometry and computational modeling to examine inter-clade differences in CA assembly and binding of PF-74, CPSF-6, and NUP-153. Interestingly, we found that HIV-1 CA from clade A1 does not bind to NUP-153, suggesting that the import of CA core structures through the nuclear pore complex may be altered for viruses from this clade. Overall, we have demonstrated that in silico generated models of the HIV-1 CA protein from clades other than the prototypically used clade B have utility in understanding and predicting biology and antiviral drug design and mechanism of action.

Design, synthesis, and mechanism study of dimerized phenylalanine derivatives as novel HIV-1 capsid inhibitors

HIV-1 capsid (CA) plays indispensable and multiple roles in the life cycle of HIV-1, become an attractive target in antiviral therapy. Herein, we report the design, synthesis, and mechanism study of a novel series of dimerized phenylalanine derivatives as HIV-1 capsid inhibitors using 2-piperazineone or 2,5-piperazinedione as a linker. The structure-activity relationship (SAR) indicated that dimerized phenylalanines were more potent than monomers of the same chemotype. Further, the inclusion of fluorine substituted phenylalanine and methoxyl substituted aniline was found to be beneficial for antiviral activity. From the synthesized series, Q-c4 was found to be the most potent compound with an EC₅₀ value of 0.57 μM, comparable to PF74. Interestingly, Q-c4 demonstrated a slightly higher affinity to the CA monomer than the CA hexamer, commensurate with its more significant effect in the late-stage of the HIV-1 lifecycle. Competitive SPR experiments with peptides from CPSF6 and NUP153 revealed that Q-c4 binds to the interprotomer pocket of hexameric CA as designed. Single-round infection assays showed that Q-c4 interferes with the HIV-1 life cycle in a dual-stage manner, affecting both pre-and post-integration. Stability assays in human plasma and human liver microsomes indicated that although Q-c4 has improved stability over PF74, this kind of inhibitor still requires further optimization. And the results of the online molinspiration software predicted that Q-c4 has desirable physicochemical properties but some properties still have some violation from the Lipinski rule of five. Overall, the dimerized phenylalanines are promising novel platforms for developing future HIV-1 CA inhibitors with considerable potential for optimization.

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.

The Role of Capsid in the Early Steps of HIV-1 Infection: New Insights into the Core of the Matter

In recent years, major advances in research and experimental approaches have significantly increased our knowledge on the role of the HIV-1 capsid in the virus life cycle, from reverse transcription to integration and gene expression. This makes the capsid protein a good pharmacological target to inhibit HIV-1 replication. This review covers our current understanding of the role of the viral capsid in the HIV-1 life cycle and its interaction with different host factors that enable reverse transcription, trafficking towards the nucleus, nuclear import and integration into host chromosomes. It also describes different promising small molecules, some of them in clinical trials, as potential targets for HIV-1 therapy.

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.

Structure, Function, and Interactions of the HIV-1 Capsid Protein

The capsid (CA) protein of the human immunodeficiency virus type 1 (HIV-1) is an essential structural component of a virion and facilitates many crucial life cycle steps through interactions with host cell factors. Capsid shields the reverse transcription complex from restriction factors while it enables trafficking to the nucleus by hijacking various adaptor proteins, such as FEZ1 and BICD2. In addition, the capsid facilitates the import and localization of the viral complex in the nucleus through interaction with NUP153, NUP358, TNPO3, and CPSF-6. In the later stages of the HIV-1 life cycle, CA plays an essential role in the maturation step as a constituent of the Gag polyprotein. In the final phase of maturation, Gag is cleaved, and CA is released, allowing for the assembly of CA into a fullerene cone, known as the capsid core. The fullerene cone consists of ~250 CA hexamers and 12 CA pentamers and encloses the viral genome and other essential viral proteins for the next round of infection. As research continues to elucidate the role of CA in the HIV-1 life cycle and the importance of the capsid protein becomes more apparent, CA displays potential as a therapeutic target for the development of HIV-1 inhibitors.

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.

Development of a pseudovirus assay and evaluation to screen natural products for inhibition of HIV-1 subtype C reverse transcriptase

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are used in the management of Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome (HIV/AIDS) in many developing country settings where HIV-1 subtype C drives the epidemic. Efforts to identify plant derived molecules with anti-HIV properties require reproducible assay systems for routine screening of selected plant compounds. Although a number of standardized HIV-1 pseudoviruses have been generated to assess infectivity, replicability or reproducibility, HIV-1 subtype C (HIV-1-C) pseudoviruses have not been comprehensively characterized to identify inhibitory plant substances.

AIM OF THE STUDY

The current study aimed at developing an HIV-1-C pseudovirus assay, and evaluate plant substances targeting reverse transcriptase (RT) activity.

MATERIALS AND METHODS

HIV-1 subtype C pseudoviruses containing a luciferase reporter gene were generated by transfection of human 293T cells. HIV-1 subtype B (HIV-1-B) wild type pseudoviruses and mutants resistant to nucleoside and non-nucleoside RT inhibitors were also generated and used as controls. Selected plant substances and the RT inhibitors Zidovudine (AZT) and Nevirapine (NVP), were used to evaluate inhibition. Pseudovirus infectivity was determined by luciferase measurement in CF2/CD4⁺/CCR5 cells, and cytotoxicity was determined using the MTT assay. AZT and NVP inhibited wild type pseudoviruses in a dose dependent manner, with IC₅₀ values in the nanomolar range.

RESULTS

Pseudoviruses harbouring RT drug resistance mutations were poorly suppressed by AZT and NVP. Catechin, obtained from Peltophorum africanum inhibited HIV-1-C and HIV-1-B pseudoviruses with selective indices of 6304 μM (IC₅₀: 0.49 μM, CC₅₀: 3089 μM) and 1343 μM (IC₅₀: 2.3 μM, CC₅₀: 3089 μM), respectively; while the methanol root crude extract of Elaeodendron transvaalense gave IC₅₀ values of 11.11 μg/ml and 16.86 μg/ml, respectively.

CONCLUSION

The developed HIV-1-C pseudovirus assay can be used to screen plant substances for RT inhibition, and may have utility in settings with limited access to high level biosafety facilities.

Design, Synthesis, and Mechanism Study of Benzenesulfonamide-Containing Phenylalanine Derivatives as Novel HIV-1 Capsid Inhibitors with Improved Antiviral Activities

The HIV-1 CA protein has gained remarkable attention as a promising therapeutic target for the development of new antivirals, due to its pivotal roles in HIV-1 replication (structural and regulatory). Herein, we report the design and synthesis of three series of benzenesulfonamide-containing phenylalanine derivatives obtained by further structural modifications of PF-74 to aid in the discovery of more potent and drug-like HIV-1 CA inhibitors. Structure-activity relationship studies of these compounds led to the identification of new phenylalanine derivatives with a piperazinone moiety, represented by compound 11l, which exhibited anti-HIV-1_NL4-3 activity 5.78-fold better than PF-74. Interestingly, 11l also showed anti-HIV-2_ROD activity (EC₅₀ = 31 nM), with almost 120 times increased potency over PF-74. However, due to the higher significance of HIV-1 as compared to HIV-2 for the human population, this manuscript focuses on the mechanism of action of our compounds in the context of HIV-1. SPR studies on representative compounds confirmed CA as the binding target. The action stage determination assay demonstrated that these inhibitors exhibited antiviral activities with a dual-stage inhibition profile. The early-stage inhibitory activity of compound 11l was 6.25 times more potent as compared to PF-74 but appeared to work via the accelerating capsid core assembly rather than stabilization. However, the mechanism by which they exert their antiviral activity in the late stage appears to be the same as PF-74 with less infectious HIV-1 virions produced in their presence, as judged p24 content studies. MD simulations provided the key rationale for the promising antiviral potency of 11l. Additionally, 11l exhibited a modest increase in HLM and human plasma metabolic stabilities as compared to PF-74, as well as a moderately improved pharmacokinetic profile, favorable oral bioavailability, and no acute toxicity. These studies provide insights and serve as a starting point for subsequent medicinal chemistry efforts in optimizing these promising HIV inhibitors.

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

HIV-1 CA is involved in different stages of the viral replication cycle, performing essential roles in both early (uncoating, reverse transcription, nuclear import, integration) and late events (assembly). Recent efforts have demonstrated HIV-1 CA protein as a prospective therapeutic target for the development of new antivirals. The most extensively studied CA inhibitor, PF-3450074 (PF-74, discovered by Pfizer), that targets an inter-protomer pocket within the CA hexamer. Herein we reported the design, synthesis, and biological evaluation of a series of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as HIV-1 CA inhibitors based on PF-74 scaffold. Most of the analogues demonstrated potent antiviral activities, among them, the anti-HIV-1 activity of 6a-9 (EC50 = 3.13 μM) is particularly prominent. The SPR binding assay of selected compounds (6a-9, 6a-10, 5b) suggested direct and effective interaction with recombinant CA proteins. The mechanism of action studies also demonstrated that 6a-9 displays the effects in both the early and late stages of HIV-1 replication. To explore the potential binding mode of the here presented analogues, 6a-9 was analyzed by MD simulation to predict its binding to the active site of HIV-1 CA monomer. In conclusion, this novel series of antivirals can serve as a starting point for the development of a new generation of HIV-1 treatment regimen and highlights the potentiality of CA as a therapeutic target.

HIV Capsid Inhibitors Beyond PF74

Human immunodeficiency virus (HIV) capsid plays important roles at multiple stages of viral replication. At the initial stages, controlled uncoating (disassembly) of the capsid ensures efficient reverse transcription of the single-stranded RNA genome, into the double-stranded DNA. Whereas at later stages, a proper assembly of capsid ensures the formation of a mature infectious virus particle. Hence, the inhibition of capsid assembly and/or disassembly has been recognized as a potential therapeutic strategy, and several capsid inhibitors have been reported. Of these, PF-3450074 (PF74) has been extensively studied. Recently reported GS-CA inhibitors (GS-CA1 and GS-6207), have shown a strong potential and appear to contain a PF74 scaffold. The location of resistance mutations and the results of structural studies further suggest that GS-CA compounds and PF74 share the same binding pocket, which is located between capsid monomers. Additionally, phenylalanine derivatives containing the PF74 scaffold show slightly enhanced capsid inhibiting activity. A comparison of capsid structures in complex with host factors and PF74, reveals the presence of common chemical entities at topologically equivalent positions. Here we present the status of capsid inhibitors that contain PF74 scaffolds and propose that the PF74 scaffold may be used to develop strong and safe capsid inhibitors.

Fluorescence Biosensor for Real-Time Interaction Dynamics of Host Proteins with HIV-1 Capsid Tubes

The human immunodeficiency virus 1 (HIV-1) capsid serves as a binding platform for proteins and small molecules from the host cell that regulate various steps in the virus life cycle. However, there are currently no quantitative methods that use assembled capsid lattices to measure host-pathogen interaction dynamics. Here we developed a single-molecule fluorescence biosensor using self-assembled capsid tubes as biorecognition elements and imaged capsid binders using total internal reflection fluorescence microscopy in a microfluidic setup. The method is highly sensitive in its ability to observe and quantify binding, to obtain dissociation constants, and to extract kinetics with an extended application of using more complex analytes that can accelerate characterization of novel capsid binders.

A HTRF based competitive binding assay for screening specific inhibitors of HIV-1 capsid assembly targeting the C-Terminal domain of capsid

Due to its multifaceted essential roles in virus replication and extreme genetic fragility, the human immunodeficiency virus type 1 (HIV-1) capsid (CA) protein is a valued therapeutic target. However, CA is as yet unexploited clinically, as there are no antiviral agents that target it currently on the market. To facilitate the identification of potential HIV-1 CA inhibitors, we established a homogeneous time-resolved fluorescence (HTRF) assay to screen for small molecules that target a biologically active and specific binding pocket in the C-terminal domain of HIV-1 CA (CA CTD). The assay, which is based on competition of small molecules for the binding of a known CA inhibitor (CAI) to the CA CTD, exhibited a signal-to-background ratio (S/B) > 10 and a Z' value > 0.9. In a pilot screen of three kinase inhibitor libraries containing 464 compounds, we identified one compound, TX-1918, as a low micromolecular inhibitor of the HIV-1 CA CTD-CAI interaction (IC₅₀ = 3.81 μM) that also inhibited viral replication at moderate micromolar concentration (EC₅₀ = 15.16 μM) and inhibited CA assembly in vitro. Based on the structure of TX-1918, an additional compound with an antiviral EC₅₀ of 6.57 μM and cellular cytotoxicity CC₅₀ of 102.55 μM was obtained from a compound similarity search. Thus, the HTRF-based assay has properties that are suitable for screening large compound libraries to identify novel anti-HIV-1 inhibitors targeting the CA CTD.

GS-CA Compounds: First-In-Class HIV-1 Capsid Inhibitors Covering Multiple Grounds

Recently reported HIV-1 capsid (CA) inhibitors GS-CA1 and GS-6207 (an analog of GS-CA1) are first-in-class compounds with long-acting potential. Reportedly, both compounds have greater potency than currently approved anti-HIV drugs. Due to the limited access to experimental data and the compounds themselves, a detailed mechanism of their inhibition is yet to be delineated. Using crystal structures of capsid-hexamers bound to well-studied capsid inhibitor PF74 and molecular modeling, we predict that GS-CA compounds bind in the pocket that is shared by previously reported CA inhibitors and host factors. Additionally, comparative modeling suggests that GS-CA compounds have unique structural features contributing to interactions with capsid. To test their proposed binding mode, we also report the design of a cyclic peptide combining structural units from GS-CA compounds, host factors, and previously reported capsid inhibitors. This peptide (Pep-1) binds CA-hexamer with a docking score comparable to GS-CA compounds. Affinity determination by MicroScale thermophoresis (MST) assays showed that CA binds Pep-1 with a ~7-fold better affinity than well-studied capsid inhibitor PF74, suggesting that it can be developed as a possible CA inhibitor.

Inhibitors of the HIV-1 capsid, a target of opportunity

PURPOSE OF REVIEW

To summarize recent advances in the discovery of chemical inhibitors targeting the HIV capsid and research on their mechanisms of action.

RECENT FINDINGS

HIV infection is critically dependent on functions of the viral capsid. Numerous studies have reported the identification of a variety of compounds that bind to the capsid protein; some of these inhibit reverse transcription and nuclear entry, steps required for infection. Other capsid-targeting compounds appear to act by perturbing capsid assembly, resulting in noninfectious progeny virions. Inhibitors may bind to several different positions on the capsid protein, including sites in both protein domains. However, the antiviral activity of many reported capsid-targeting inhibitors has not been definitively linked to capsid binding. Until recently, the low-to-moderate potency of reported capsid-targeting inhibitors has precluded their further clinical development. In 2017, GS-CA1, a highly potent capsid inhibitor, was described that holds promise for clinical development.

SUMMARY

Small molecules that bind to the viral capsid protein can be potent inhibitors of HIV infection. Capsid-targeting drugs are predicted to exhibit high barriers to viral resistance, and ongoing work in this area is contributing to an understanding of the molecular biology of HIV uncoating and maturation.

Discovery of phenylalanine derivatives as potent HIV-1 capsid inhibitors from click chemistry-based compound library

The HIV-1 capsid (CA) protein plays essential roles in both early and late stages of HIV-1 replication and is considered an important, clinically unexploited therapeutic target. As such, small drug-like molecules that inhibit this critical HIV-1 protein have become a priority for several groups. Therefore, in this study we explore small molecule targeting of the CA protein, and in particular a very attractive inter-protomer pocket. We report the design, parallel synthesis, and anti-HIV-1 activity evaluation of a series of novel phenylalanine derivatives as HIV-1 CA protein inhibitors synthesized via Cu(I)-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction. We demonstrate robust inhibitory activity over a range of potencies against the HIV-1 NL_4-3 reference strain. In particular, compound 13m exhibited the greatest potency and lowest toxicity within this new series with an EC₅₀ value of 4.33 μM and CC₅₀ value of >57.74 μM (SI > 13.33). These values are very similar to the lead compound PF-74 (EC₅₀ = 5.95 μM, CC₅₀ > 70.50 μM, SI > 11.85) in our assay, despite significant structural difference. Furthermore, we demonstrate via surface plasmon resonance (SPR) binding assays that 13m interacts robustly with recombinant HIV-1 CA and exhibits antiviral activity in both the early and late stages of HIV-1 replication. Overall, the novel parallel synthesis and structure-activity relationships (SARs) identified within this study set the foundation for further rational optimization and discovery of CA-targeting compounds with improved potency.

Discovery of Oxime Ethers as Hepatitis B Virus (HBV) Inhibitors by Docking, Screening and In Vitro Investigation

A series of oxime ethers with C₆-C₄ fragment was designed and virtually bioactively screened by docking with a target, then provided by a Friedel–Crafts reaction, esterification (or amidation), and oximation from p-substituted phenyl derivatives (Methylbenzene, Methoxybenzene, Chlorobenzene). Anti-hepatitis B virus (HBV) activities of all synthesized compounds were evaluated with HepG2.2.15 cells in vitro. Results showed that most of compounds exhibited low cytotoxicity on HepG2.2.15 cells and significant inhibition on the secretion of HBsAg and HBeAg. Among them, compound 5c-1 showed the most potent activity on inhibiting HBsAg secretion (IC₅₀ = 39.93 μM, SI = 28.51). Results of the bioactive screening showed that stronger the compounds bound to target human leukocyte antigen A protein in docking, the more active they were in anti-HBV activities in vitro.

HIV-1 Capsid Inhibitors as Antiretroviral Agents

BACKGROUND

The infectious human immunodeficiency virus (HIV) particle is characterized by a conical capsid that encloses the viral RNA genome. The capsid is essential for HIV-1 replication and plays crucial roles in both early and late stages of the viral life cycle. Early on, upon fusion of the viral and cellular membranes, the viral capsid is released into the host cell cytoplasm and dissociates in a process known as uncoating, tightly associated with the reverse transcription of the viral genome. During the late stages of viral replication, the Gag polyprotein, precursor of the capsid protein, assemble at the plasma membrane to form immature non-infectious viral particles. After a maturation step by the viral protease, the capsid assembles to form a fullerene-like conical shape characteristic of the mature infectious particle. Mutations affecting the uncoating process, or capsid assembly and maturation, have been shown to hamper viral infectivity. The key role of capsid in viral replication and the absence of approved drugs against this protein have promoted the development of antiretrovirals. Screening based on the inhibition of capsid assembly and virtual screening for molecules binding to the capsid have successfully identified a number of potential small molecule compounds. Unfortunately, none of these molecules is currently used in the clinic.

CONCLUSION

Here we review the discovery and the mechanism of action of the small molecules and peptides identified as capsid inhibitors, and discuss their therapeutic potential.

A Cell Internalizing Antibody Targeting Capsid Protein (p24) Inhibits the Replication of HIV-1 in T Cells Lines and PBMCs: A Proof of Concept Study

There remains a need for newer therapeutic approaches to combat HIV/AIDS. Viral capsid protein p24 plays important roles in HIV pathogenesis. Peptides and small molecule inhibitors targeting p24 have shown to inhibit virus replication in treated cell. High specificity and biological stability of monoclonal antibodies (mAbs) make them an attractive contender for in vivo treatments. However, mAbs do not enter into cells, thus are restricted to target surface molecules. This also makes targeting intracellular HIV-1 p24 a challenge. A mAb specific to p24 that can internalize into the HIV-infected cells is hypothesized to inhibit the virus replication. We selected a mAb that has previously shown to inhibit p24 polymerization in an in vitro assay and chemically conjugated it with cell penetrating peptides (CPP) to generate cell internalizing anti-p24 mAbs. Out of 8 CPPs tested, κFGF-MTS -conjugated mAbs internalized T cells most efficiently. At nontoxic concentration, the κFGF-MTS-anti-p24-mAbs reduced the HIV-1 replication up to 73 and 49% in T-lymphocyte and PBMCs respectively. Marked inhibition of HIV-1 replication in relevant cells by κFGF-MTS-anti-p24-mAbs represents a viable strategy to target HIV proteins present inside the cells.

Identification of a small molecule HIV-1 inhibitor that targets the capsid hexamer

The HIV-1 CA protein is an attractive therapeutic target for the development of new antivirals. An inter-protomer pocket within the hexamer configuration of the CA, which is a binding site for key host dependency factors, is an especially appealing region for small molecule targeting. Using a field-based pharmacophore derived from an inhibitor known to interact with this region, coupled to biochemical and biological assessment, we have identified a new compound that inhibits HIV-1 infection and that targets the assembled CA hexamer.