Etravirine: a second-generation NNRTI for treatment-experienced adults with resistant HIV-1 infection

Antiretroviral (ARV) Properties Dictate Long-Acting Release and Tissue Partitioning Behaviors in Multidrug Subcutaneous Implants

Subcutaneous implants can provide patients with long-acting, compliance-independent drug dosing. For this reason, subcutaneous implants have shown emerging interest in human immunodeficiency virus (HIV) prevention. However, any successful long-acting HIV-prevention device will require multidrug dosing, which poses a challenge for formulation considering the physicochemically diverse selection of antiretroviral (ARV) candidates. As a method that has shown the capacity of efficient multidrug delivery, we assessed electrospun fiber implants composed of three synergistically potent ARVs and a biodegradable polymer selected by in vitro release studies. In mice, subcutaneous electrospun fiber implants exhibit burst release of the more hydrophilic drugs maraviroc (MVC) and raltegravir (RAL), which could be reduced via simple prewash treatments of the implants. Over an extended 120 day time frame, fiber implants show drug-specific differences in release time frames and magnitudes in blood serum. However, end-point drug tissue concentrations show that the most hydrophobic drug etravirine (ETR) remains in high concentrations within the implant and in local skin tissue biopsies. Furthermore, ETR is found to be capable of significant partitioning into lymph nodes, the lower female reproductive tract, and the rectum. Topologically smooth film implants also exhibit the same drug-dependent trends. Therefore, we illustrate that drug release and drug tissue partitioning are largely dictated by drug properties. Further, we find that the properties of ETR enable significant drug quantities within the tissues most relevant to HIV protection. Evidence from this work emphasizes the need for a greater focus on drug properties and prodrug strategies to enable relevant, extended, and targeted drug release.

Indolylarylsulfones bearing phenylboronic acid and phenylboronate ester functionalities as potent HIV‑1 non-nucleoside reverse transcriptase inhibitors

To explore the chemical space around the entrance channel of the HIV-1 reverse transcriptase (RT) binding pocket, we innovatively designed and synthesized a series of novel indolylarylsulfones (IASs) bearing phenylboronic acid and phenylboronate ester functionalities at the indole-2-carboxamide as new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) through structure-based drug design. All the newly synthesized compounds exhibited excellent to moderate potency against wild-type (WT) HIV-1 with EC₅₀ values ranging from 6.7 to 42.6 nM. Among all, (3-ethylphenyl)boronic acid substituted indole-2-carboxamide and (4-ethylphenyl) boronate ester substituted indole-2-carboxamide were found to be the most potent inhibitors (EC₅₀ = 8.5 nM, SI = 3310; EC₅₀ = 6.7 nM, SI = 3549, respectively). Notably, (3-ethylphenyl)boronic acid substituted indole-2-carboxamide maintained excellent activities against the single HIV-1 mutants L100I (EC₅₀ = 7.3 nM), K103N (EC₅₀ = 9.2 nM), as well as the double mutant V106A/F227L (EC₅₀ = 21.1 nM). Preliminary SARs and molecular modelling studies are also discussed in detail.

Structural investigation of 2-naphthyl phenyl ether inhibitors bound to WT and Y181C reverse transcriptase highlights key features of the NNRTI binding site

Human immunodeficiency virus (HIV)-1 remains as a global health issue that is primarily treated with highly active antiretroviral therapy, a combination of drugs that target the viral life cycle. One class of these drugs are non-nucleoside reverse transcriptase inhibitors (NNRTIs) that target the viral reverse transcriptase (RT). First generation NNRTIs were troubled with poor pharmacological properties and drug resistance, incentivizing the development of improved compounds. One class of developed compounds are the 2-naphthyl phenyl ethers, showing promising efficacy against the Y181C RT mutation. Further biochemical and structural work demonstrated differences in potency against the Y181C mutation and binding mode of the compounds. This work aims to understand the relationship between the binding mode and ability to overcome drug resistance using macromolecular x-ray crystallography. Comparison of 2-naphthyl phenyl ethers bound to Y181C RT reveal that compounds that interact with the invariant W229 are more capable of retaining efficacy against the resistance mutation. Additional modifications to these compounds at the 4-position, computationally designed to compensate for the Y181C mutation, do not demonstrate improved potency. Ultimately, we highlight important considerations for the development of future HIV-1 drugs that are able to combat drug resistance.

Synthesis, molecular docking and biological evaluation of 2-(thiophen-2-yl)-1H-indoles as potent HIV-1 non-nucleoside reverse transcriptase inhibitors

New 2-(thiophen-2-yl)-1H-indole derivatives bearing hydrophobic substituents at the 3-position were designed, synthesized and evaluated for their inhibition of HIV-1 reverse transcriptase (RT) enzyme. Dialkylphosphites (2a-c) or trialkylphosphites (3a-c) were reacted with 2-(thiophen-2-yl)-1H-indole-3-carbaldehyde (1) yielding the corresponding α-hydroxyphosphonate adducts (7a-7c). The reaction of compound 1 with the ylidenetriphenylphosphoranes (4a-4c) proceeds via Wittig mechanism giving the corresponding ethylenes (E, 8a-c). Compounds 8b,c were equally obtained upon reacting aldehyde 1 with the appropriate dialkylphosphonates 5a,b under the Horner-Wittig reaction conditions. On the other hand, the reaction of aldehyde 1 with diethyl cyanomethylene phosphonate (5c) yielded a mixture of the E-ethylene 10 and the cyanovinyl phosphonate 11. The thioaldehyde 12 was obtained upon refluxing aldehyde 1 with the Lawesson's reagent (LR, 6a) or with the Japanese reagent (JR, 6b) in dry toluene. Upon evaluation of HIV-1 Reverse Transcriptase enzyme inhibition, compound 8b (IC₅₀ = 2.93 nM) exhibited the superior HIV-1 RT inhibition and its potency was about 3-folds that of Efavirenz (IC₅₀ = 6.03 nM). Also, compounds 9a (IC₅₀ = 4.09 nM) and 12 (IC₅₀ = 3.54 nM) showed significantly higher inhibition potency. Moreover, compounds 7b (IC₅₀ = 7.48 nM), and 8a (IC₅₀ = 4.55 nM) showed potency not significantly different from that of Efavirenz. Molecular docking experiments on these potent compounds was in accordance with the in vitro data and confirmed binding of these compounds to the enzyme through ring-stacking and hydrogen bond interactions. According to these results, the new molecules would serve as potent HIV-1 NNRTIs inhibitors.

Synthesis and biological evaluation of dihydroquinazoline-2-amines as potent non-nucleoside reverse transcriptase inhibitors of wild-type and mutant HIV-1 strains

A novel series of dihydroquinazolin-2-amine derivatives were synthesized and evaluated for their anti-HIV-1 activity in MT-4 cell cultures. All of the molecules were active against wild-type HIV-1 with EC₅₀ values ranging from 0.61 μM to 0.84 nM. The most potent inhibitor, compound 4b, had an EC₅₀ value of 0.84 nM against HIV-1 strain IIIB, and thus was more active than the reference drugs efavirenz and etravirine. Moreover, most of the compounds maintained high activity (low-micromolar EC₅₀ values) against strains bearing the reverse transcriptase (RT) E138K mutation. Compound 4b had EC₅₀ values of 3.5 nM and 66 nM against non-nucleoside reverse transcriptase inhibitor-resistant strains bearing the RT E138K and RES056 mutations. In enzyme activity assays, compound 4b exhibited an IC₅₀ value of 10 nM against HIV-1 RT. Preliminary SARs and molecular docking studies provide valuable insights for further optimization.

Pyrimidine 2,4-Diones in the Design of New HIV RT Inhibitors

The pyrimidine nucleus is a versatile core in the development of antiretroviral agents. On this basis, a series of pyrimidine-2,4-diones linked to an isoxazolidine nucleus have been synthesized and tested as nucleoside analogs, endowed with potential anti-HIV (human immunodeficiency virus) activity. Compounds 6a-c, characterized by the presence of an ethereal group at C-3, show HIV reverse transcriptase (RT) inhibitor activity in the nanomolar range as well as HIV-infection inhibitor activity in the low micromolar with no toxicity. In the same context, compound 7b shows only a negligible inhibition of RT HIV.

Discovery of novel piperidine-substituted indolylarylsulfones as potent HIV NNRTIs via structure-guided scaffold morphing and fragment rearrangement

To further explore the chemical space around the entrance channel of HIV-1 reverse transcriptase (RT), a series of novel indolylarylsulfones (IASs) bearing N-substituted piperidine at indole-2-carboxamide were identified as potent HIV NNRTIs by structure-guided scaffold morphing and fragment rearrangement. All the IASs exhibited moderate to excellent potency against wild-type HIV-1 with EC₅₀ values ranging from 0.62 μM to 0.006 μM 8 (EC₅₀ = 6 nM) and 18 (EC₅₀ = 9 nM) were identified as the most potent compounds, which were more active than NVP and DLV, and reached the same order of EFV and ETV. Furthermore, most compounds maintained high activity agaist various single HIV-1 mutants (L100I, K103N, E138K, Y181C) as well as one double mutant (F227L/V106A) with EC₅₀ values in low-micromolar to double-digit nanomolar concentration ranges. Especially, 8 displayed outstanding potency against L100I (EC₅₀ = 17 nM with a 2.8-fold resistance ratio) and 18 was relatively more potent to E138K mutant (EC₅₀ = 43 nM with a 4.7-fold resistance ratio). Preliminary SARs and molecular modeling studies were also discussed in detail, which may provide valuable insights for further optimization.

Design, Synthesis, and Evaluation of Thiophene[3,2-d]pyrimidine Derivatives as HIV-1 Non-nucleoside Reverse Transcriptase Inhibitors with Significantly Improved Drug Resistance Profiles

We designed and synthesized a series of human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTIs) with a piperidine-substituted thiophene[3,2-d]pyrimidine scaffold, employing a strategy of structure-based molecular hybridization and substituent decorating. Most of the synthesized compounds exhibited broad-spectrum activity with low (single-digit) nanomolar EC50 values toward a panel of wild-type (WT), single-mutant, and double-mutant HIV-1 strains. Compound 27 was the most potent; compared with ETV, its antiviral efficacy was 3-fold greater against WT, 5-7-fold greater against Y181C, Y188L, E138K, and F227L+V106A, and nearly equipotent against L100I and K103N, though somewhat weaker against K103N+Y181C. Importantly, 27 has lower cytotoxicity (CC50 > 227 μM) and a huge selectivity index (SI) value (ratio of CC50/EC50) of >159101. 27 also showed favorable, drug-like pharmacokinetic and safety properties in rats in vivo. Molecular docking studies and the structure-activity relationships provide important clues for further molecular elaboration.

Etravirine in CSF is highly protein bound

OBJECTIVES

Etravirine has high affinity for plasma drug-binding proteins, such as albumin and α1-acid glycoprotein, which limits the amount of unbound etravirine available to enter the CNS. The objective of this study was to compare total and unbound etravirine concentrations in CSF with plasma concentrations and the in vitro median inhibitory concentration (IC50) for wild-type HIV (0.9 ng/mL).

METHODS

Total and bound etravirine concentrations were measured in 17 CSF and plasma pairs by isotope-dilution liquid chromatography tandem mass spectroscopy, radioligand displacement and ultracentrifugation. Unbound etravirine concentrations were calculated from the bound fraction. The dynamic range of the assay was 7.8-2000 (plasma) and 0.78-200 (CSF) ng/mL.

RESULTS

Subjects were mostly middle-aged (median 43 years) white (78%) men (89%). All CSF etravirine concentrations were above the limit of quantification. Total and unbound median etravirine concentrations in CSF were 9.5 (IQR 6.4, 26.4) and 0.13 (IQR 0.08, 0.27) ng/mL, respectively. Etravirine was 96% (IQR 94.5, 97.2) protein bound in plasma and 98.4% (IQR 97.8, 98.8) in CSF. Total etravirine in CSF was 4.3% (IQR 3, 5.9) of total and 101% (IQR 76, 160) of unbound etravirine in plasma. There were no significant correlations between unbound etravirine concentrations and concentrations of albumin in plasma or CSF. Unbound etravirine concentrations in CSF did not reach the wild-type IC50 in any of the specimens.

CONCLUSIONS

Unbound etravirine may not achieve optimal concentrations to inhibit HIV replication in the CNS.

Analysis of protease and reverse transcriptase genes of HIV for antiretroviral drug resistance in Jamaican adults

This study reports on the drug resistance profiles for HIV-infected adults in Jamaica using genotypic methods. The genetic diversity of HIV-1 found in these patients was also determined using phylogenetic analysis. Epidemiological data were documented for each patient, blood was collected by venous puncture, and plasma was separated and stored. Viral RNA was extracted and analyzed for mutations in the viral genome by the amplification of the protease and reverse transcriptase (Pro-RT) regions using a nested PCR method. The rate of drug resistance among treatment-experienced individuals was 35%, while treatment-naive individuals showed a prevalence of 29%. The overall prevalence of drug resistance mutations in Jamaicans was consistent with the increased use of antiretroviral drugs in the region, with many of the mutations detected reducing susceptibility to the drugs commonly used to treat Jamaican patients. These results indicate the need for regular drug resistant surveillance to guide treatment strategies.

Synthesis, structure-activity relationships, and docking studies of N-phenylarylformamide derivatives (PAFAs) as non-nucleoside HIV reverse transcriptase inhibitors

A series of N-phenylarylformamide derivatives (PAFAs) with anti-wild-type HIV-1 activity (EC(50) values) ranging from 0.3 nM to 5.1 nM and therapeutic index (TI) ranging from 10 616 to 271 000 were identified as novel non-nucleoside reverse transcriptase inhibitors. Among them, compound 13g (EC(50) = 0.30 nM, TI = 184 578), 13l (EC(50) = 0.37 nM, TI = 212 819), 13m (EC(50) = 0.32 nM, TI = 260 617) and 13r (EC(50) = 0.27 nM, TI = 271 000) displayed the highest activity against this type virus nearly as potent as lead compound GW678248. Moreover, all of them were also active to inhibit the double mutant strain A(17) (K103N + Y181C) with EC(50) values of 0.29 μM, 0.14 μM, 0.10 μM and 0.27 μM, respectively. In particular, compound 13m, which showed broad-spectrum anti-HIV activity, was also effective to inhibit the HIV-2 ROD replication within 4.37 μM concentration.

Rhodium(II) acetate-catalyzed stereoselective synthesis, SAR and anti-HIV activity of novel oxindoles bearing cyclopropane ring

Novel oxindole derivatives bearing substituted cyclopropane ring have been designed on the basis of docking studies with HIV-1 RT using the software DS 2.5 and synthesized as probable NNRTIs against HIV-1 using rhodium(II) acetate-catalyzed stereoselective cyclopropanation reaction. The cyclopropane isomer, having trans relationship with respect to carbonyl of lactam moiety and functional group on the cyclopropane ring, was the major product in all cases along with a small amount of cis and methylene products. The trans isomers interacted well with HIV-1 RT through H-bonding with amino acids, like Lys101, Lys103, His235, Tyr318, constituting the non-nucleoside inhibitor binding pocket (NNIBP) during docking experiments. However, the compounds showed very little activity when subjected to in vitro anti-HIV-1 screening using β-galactosidase assay (TZM-bl cells) and GFP quantification (CEM-GFP cells). The very low level of in vitro HIV inhibition, in comparison to predicted EC(50) values on the basis of computational studies, during CEM-GFP screening using AZT as positive control indicated that probably the HIV RT is not the viral target and the molecules work through some different mechanism.

Design, synthesis, and evaluation of diarylpyridines and diarylanilines as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

On the basis of the structures and activities of our previously identified non-nucleoside reverse transcriptase inhibitors (NNRTIs), we designed and synthesized two sets of derivatives, diarylpyridines (A) and diarylanilines (B), and tested their anti-HIV-1 activity against infection by HIV-1 NL4-3 and IIIB in TZM-bl and MT-2 cells, respectively. The results showed that most compounds exhibited potent anti-HIV-1 activity with low nanomolar EC50 values, and some of them, such as 13m, 14c, and 14e, displayed high potency with subnanomolar EC50 values, which were more potent than etravirine (TMC125, 1) in the same assays. Notably, these compounds were also highly effective against infection by multi-RTI-resistant strains, suggesting a high potential to further develop these compounds as a novel class of NNRTIs with improved antiviral efficacy and resistance profile.

Novel 1,3-dihydro-benzimidazol-2-ones and their analogues as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

A series of novel benzimidazolones and their analogues, characterized by the presence of one or more methyl groups or other bioisosteric moieties at different positions of the phenyl ring at N-1, were synthesized and evaluated as inhibitors of human immunodeficiency virus type-1 (HIV-1). Most of the new compounds proved to be highly effective in inhibiting both HIV-1 replication in MT4 cells with minimal cytotoxicity and RT enzyme at nanomolar concentrations. Some derivatives were also tested against RTs containing single amino acid mutations responsible for resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs). The different potencies displayed by the new compounds were studied using molecular modeling.

New pyridinone derivatives as potent HIV-1 nonnucleoside reverse transcriptase inhibitors

Several 5-ethyl-6-methyl-4-cycloalkyloxy-pyridin-2(1H)-ones were synthesized and evaluated for their anti HIV-1 activities against wild-type virus and clinically relevant mutant strains. A racemic mixture (10) with methyl substituents at positions 3 and 5 of the cyclohexyloxy moiety had potent antiviral activity against wild-type HIV-1. Subsequent stereoselective synthesis of a stereoisomer displaying both methyl groups in equatorial position was found to have the best EC(50). Further modulations focused on position 3 of the pyridinone ring improved the antiviral activity against mutant viral strains. Compounds bearing a 3-ethyl (22) or 3-isopropyl group (23) had the highest activity against wild-type HIV-1 and displayed low-nanomolar potency against several clinically relevant mutant strains.