Advancing beyond reverse transcriptase inhibitors: The new era of hepatitis B polymerase inhibitors.

Hepatitis B virus (HBV) is a genetically diverse blood-borne virus responsible for chronic hepatitis B. The HBV polymerase plays a key role in viral genome replication within the human body and has been identified as a potential drug target for chronic hepatitis B therapeutics. However, available nucleotide reverse transcriptase inhibitors only target the reverse transcriptase domain of the HBV polymerase; they also pose resistance issues and require lifelong treatment that can burden patients financially. In this study, various chemical classes are reviewed that have been developed to target different domains of the HBV polymerase: Terminal protein, which plays a vital role in the formation of the viral DNA; Reverse transcriptase, which is responsible for the synthesis of the viral DNA from RNA, and; Ribonuclease H, which is responsible for degrading the RNA strand in the RNA-DNA duplex formed during the reverse transcription process. Host factors that interact with the HBV polymerase to achieve HBV replication are also reviewed; these host factors can be targeted by inhibitors to indirectly inhibit polymerase functionality. A detailed analysis of the scope and limitations of these inhibitors from a medicinal chemistry perspective is provided. The structure-activity relationship of these inhibitors and the factors that may affect their potency and selectivity are also examined. This analysis will be useful in supporting the further development of these inhibitors and in designing new inhibitors that can inhibit HBV replication more efficiently.

Safety and Pharmacokinetics of Islatravir in Individuals with Severe Renal Insufficiency.

Islatravir (MK-8591) is a high-potency reverse transcriptase translocation inhibitor in development for the treatment of HIV-1 infection. Data from preclinical and clinical studies suggest that ~30% to 60% of islatravir is excreted renally and that islatravir is not a substrate of renal transporters. To assess the impact of renal impairment on the pharmacokinetics of islatravir, an open-label phase 1 trial was conducted with individuals with severe renal insufficiency (RI). A single dose of islatravir 60 mg was administered orally to individuals with severe RI (estimated glomerular filtration rate [eGFR] <30 mL/min/1.73 m2) and to healthy individuals without renal impairment (matched control group; eGFR ≥90 mL/min/1.73 m2). Safety and tolerability were assessed, and blood samples were collected to measure the pharmacokinetics of islatravir and its major metabolite 4'-ethynyl-2-fluoro-2'deoxyinosine (M4) in plasma, as well as active islatravir-triphosphate (TP) in peripheral blood mononuclear cells (PBMCs). Plasma islatravir and M4 area under the concentration-time curve from zero to infinity (AUC0-∞) were ~2-fold and ~5-fold higher, respectively, in participants with severe RI relative to controls, whereas islatravir-TP AUC0-∞ was ~1.5-fold higher in the RI group than in the control group. The half-lives of islatravir in plasma and islatravir-TP in PBMCs were longer in participants with severe RI than in controls. These findings are consistent with renal excretion playing a major role in islatravir elimination. A single oral dose of islatravir 60 mg was generally well tolerated. These data provide guidance regarding administration of islatravir in individuals with impaired renal function. (This study has been registered at ClinicalTrials.gov under registration no. NCT04303156.).

LINE-1 activation in the cerebellum drives ataxia.

Dysregulation of long interspersed nuclear element 1 (LINE-1, L1), a dominant class of transposable elements in the human genome, has been linked to neurodegenerative diseases, but whether elevated L1 expression is sufficient to cause neurodegeneration has not been directly tested. Here, we show that the cerebellar expression of L1 is significantly elevated in ataxia telangiectasia patients and strongly anti-correlated with the expression of epigenetic silencers. To examine the role of L1 in the disease etiology, we developed an approach for direct targeting of the L1 promoter for overexpression in mice. We demonstrated that L1 activation in the cerebellum led to Purkinje cell dysfunctions and degeneration and was sufficient to cause ataxia. Treatment with a nucleoside reverse transcriptase inhibitor blunted ataxia progression by reducing DNA damage, attenuating gliosis, and reversing deficits of molecular regulators for calcium homeostasis in Purkinje cells. Our study provides the first direct evidence that L1 activation can drive neurodegeneration.

Development of Novel Dihydrofuro[3,4-d]pyrimidine Derivatives as HIV-1 NNRTIs to Overcome the Highly Resistant Mutant Strains F227L/V106A and K103N/Y181C.

Here, we report the design, synthesis, structure-activity relationship studies, antiviral activity, enzyme inhibition, and druggability evaluation of dihydrofuro[3,4-d]pyrimidine derivatives as a potent class of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Compounds 14b (EC50 = 5.79-28.3 nM) and 16c (EC50 = 2.85-18.0 nM) exhibited superior potency against a panel of HIV-1-resistant strains. Especially, for the changeling mutations F227L/V106A and K103N/Y181C, both compounds exhibited remarkably improved activity compared to those of etravirine and rilpivirine. Moreover, 14b and 16c showed moderate RT enzyme inhibition (IC50 = 0.14-0.15 µM), which demonstrated that they acted as HIV-1 NNRTIs. Furthermore, 14b and 16c exhibited favorable pharmacokinetic and safety properties, making them excellent leads for further development.

Structure-Based Design and Discovery of Pyridyl-Bearing Fused Bicyclic HIV-1 Inhibitors: Synthesis, Biological Characterization, and Molecular Modeling Studies.

Two series of new pyridyl-bearing fused bicyclic analogues designed to target the dual-tolerant regions of the non-nucleoside reverse transcriptase inhibitor (NNRTI)-binding pocket were synthesized and evaluated for their anti-HIV activities. Several compounds, such as 6, 14, 15, 21, 30, and 33, were found to be potent inhibitors against the wild-type (WT) HIV-1 strain or multiple NNRTI-resistant strains at low nanomolar levels. Detailed structure-activity relationships were obtained by utilizing the variation of moieties within the corresponding pharmacophores. In vitro metabolic stability profiles and some drug-like properties of selected compounds were assessed, furnishing the preliminary structure-metabolic stability relationships. Furthermore, molecular modeling studies elucidated the binding modes of compounds 6, 15, 21, and 30 in the binding pocket of WT, E138K, K103N, or Y181C HIV-1 RTs. These promising compounds can be used as lead compounds and warrant further structural optimization to yield more active HIV-1 inhibitors.

Islatravir Is Not Expected to Be a Victim or Perpetrator of Drug-Drug Interactions via Major Drug-Metabolizing Enzymes or Transporters.

Islatravir (MK-8591) is a nucleoside reverse transcriptase translocation inhibitor in development for the treatment and prevention of HIV-1. The potential for islatravir to interact with commonly co-prescribed medications was studied in vitro. Elimination of islatravir is expected to be balanced between adenosine deaminase-mediated metabolism and renal excretion. Islatravir did not inhibit uridine diphosphate glucuronosyltransferase 1A1 or cytochrome p450 (CYP) enzymes CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4, nor did it induce CYP1A2, 2B6, or 3A4. Islatravir did not inhibit hepatic transporters organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic cation transporter (OCT) 1, bile salt export pump (BSEP), multidrug resistance-associated protein (MRP) 2, MRP3, or MRP4. Islatravir was neither a substrate nor a significant inhibitor of renal transporters organic anion transporter (OAT) 1, OAT3, OCT2, multidrug and toxin extrusion protein (MATE) 1, or MATE2K. Islatravir did not significantly inhibit P-glycoprotein and breast cancer resistance protein (BCRP); however, it was a substrate of BCRP, which is not expected to be of clinical significance. These findings suggest islatravir is unlikely to be the victim or perpetrator of drug-drug interactions with commonly co-prescribed medications, including statins, diuretics, anti-diabetic drugs, proton pump inhibitors, anticoagulants, benzodiazepines, and selective serotonin reuptake inhibitors.

Discovery of Novel Dihydrothiopyrano[4,3-d]pyrimidine Derivatives as Potent HIV-1 NNRTIs with Significantly Reduced hERG Inhibitory Activity and Improved Resistance Profiles.

Enlightened by the available structural biology information, a novel series of dihydrothiopyrano[4,3-d]pyrimidine derivatives were rationally designed via scaffold hopping and molecular hybridization strategies. Notably, compound 20a yielded exceptionally potent antiviral activities (EC50 = 4.44-54.5 nM) against various HIV-1 strains and improved resistance profiles (RF = 0.5-5.6) compared to etravirine and rilpivirine. Meanwhile, 20a exhibited reduced cytotoxicity (CC50 = 284 µM) and higher SI values (SI = 5210-63992). Molecular dynamics simulations were performed to rationalize the distinct resistance profiles. Besides, 20a displayed better solubility (sol. = 12.8 µg/mL) and no significant inhibition of the main CYP enzymes. Furthermore, 20a was characterized for prominent metabolic stability and in vivo safety properties. Most importantly, the hERG inhibition profile of 20a (IC50 = 19.84 µM) was a remarkable improvement. Overall, 20a possesses huge potential to serve as a promising drug candidate due to its excellent potency, low toxicity, and favorable drug-like properties.

Biochemical and Structural Properties of Entecavir-Resistant Hepatitis B Virus Polymerase with L180M/M204V Mutations.

Entecavir (ETV) is a widely used anti-hepatitis B virus (HBV) drug. However, the emergence of resistant mutations in HBV reverse transcriptase (RT) results in treatment failure. To understand the mechanism underlying the development of ETV resistance by HBV RT, we analyzed the L180M, M204V, and L180M/M204V mutants using a combination of biochemical and structural techniques. ETV-triphosphate (ETV-TP) exhibited competitive inhibition with dGTP in both wild-type (wt) RT and M204V RT, as observed using Lineweaver-Burk plots. In contrast, RT L180M or L180M/M204V did not fit either competitive, uncompetitive, noncompetitive, or typical mixed inhibition, although ETV-TP was a competitive inhibitor of dGTP. Crystallography of HIV RTY115F/F116Y/Q151M/F160M/M184V, mimicking HBV RT L180M/M204V, showed that the F115 bulge (F88 in HBV RT) caused by the F160M mutation induced deviated binding of dCTP from its normal tight binding position. Modeling of ETV-TP on the deviated dCTP indicated that a steric clash could occur between ETV-TP methylene and the 3'-end nucleoside ribose. ETV-TP is likely to interact primarily with HBV RT M171 prior to final accommodation at the deoxynucleoside triphosphate (dNTP) binding site (Y. Yasutake, S. Hattori, H. Hayashi, K. Matsuda, et al., Sci Rep 8:1624, 2018, https://doi.org/10.1038/s41598-018-19602-9). Therefore, in HBV RT L180M/M204V, ETV-TP may be stuck at M171, a residue that is conserved in almost all HBV isolates, leading to the strange inhibition pattern observed in the kinetic analysis. Collectively, our results provide novel insights into the mechanism of ETV resistance of HBV RT caused by L180M and M204V mutations. IMPORTANCE HBV infects 257 million people in the world, who suffer from elevated risks of liver cirrhosis and cancer. ETV is one of the most potent anti-HBV drugs, and ETV resistance mutations in HBV RT have been extensively studied. Nevertheless, the mechanisms underlying ETV resistance have remained elusive. We propose an attractive hypothesis to explain ETV resistance and effectiveness using a combination of kinetic and structural analyses. ETV is likely to have an additional interaction site, M171, beside the dNTP pocket of HBV RT; this finding indicates that nucleos(t)ide analogues (NAs) recognizing multiple interaction sites within RT may effectively inhibit the enzyme. Modification of ETV may render it more effective and enable the rational design of efficient NA inhibitors.

Quinolinonyl Non-Diketo Acid Derivatives as Inhibitors of HIV-1 Ribonuclease H and Polymerase Functions of Reverse Transcriptase.

Novel anti-HIV agents are still needed to overcome resistance issues, in particular inhibitors acting against novel viral targets. The ribonuclease H (RNase H) function of the reverse transcriptase (RT) represents a validated and promising target, and no inhibitor has reached the clinical pipeline yet. Here, we present rationally designed non-diketo acid selective RNase H inhibitors (RHIs) based on the quinolinone scaffold starting from former dual integrase (IN)/RNase H quinolinonyl diketo acids. Several derivatives were synthesized and tested against RNase H and viral replication and found active at micromolar concentrations. Docking studies within the RNase H catalytic site, coupled with site-directed mutagenesis, and Mg2+ titration experiments demonstrated that our compounds coordinate the Mg2+ cofactor and interact with amino acids of the RNase H domain that are highly conserved among naïve and treatment-experienced patients. In general, the new inhibitors influenced also the polymerase activity of RT but were selective against RNase H vs the IN enzyme.

Layer-by-Layer Assembled Nanostructured Lipid Carriers for CD-44 Receptor-Based Targeting in HIV-Infected Macrophages for Efficient HIV-1 Inhibition.

Macrophages act as a cellular reservoir in HIV infection. Elimination of HIV from macrophages has been an unfulfilled dream due to the failure of drugs to reach them. To address this, we developed CD44 receptor-targeted, novel hyaluronic acid (HA)-coated nanostructured lipid carriers (NLCs) of efavirenz via washless layer-by-layer (LbL) assembly of HA and polyallylamine hydrochloride (PAH). NLCs were subjected to TEM analysis, size and zeta potential, in vitro release and encapsulation efficiency studies. The uptake of NLCs in THP-1 cells was studied using fluorescence microscopy and flow cytometry. The anti-HIV efficacy was evaluated using p24 antigen inhibition assay. NLCs were found to be spherical in shape with anionic zeta potential (-23.66 ± 0.87 mV) and 241.83 ± 5.38 nm particle size. NLCs exhibited prolonged release of efavirenz during in vitro drug release studies. Flow cytometry revealed 1.73-fold higher uptake of HA-coated NLCs in THP-1 cells. Cytotoxicity studies showed no significant change in cell viability in presence of NLCs as compared with the control. HA-coated NLCs distributed throughout the cell including cytoplasm, plasma membrane and nucleus, as observed during fluorescence microscopy. HA-coated NLCs demonstrated consistent and significantly higher inhibition (81.26 ± 1.70%) of p24 antigen which was 2.08-fold higher than plain NLCs. The obtained results suggested preferential uptake of HA-coated NLCs via CD44-mediated uptake. The present finding demonstrates that HA-based CD44 receptor targeting in HIV infection is an attractive strategy for maximising the drug delivery to macrophages and achieve effective viral inhibition.

Effects of islatravir (4'-ethynyl-2-fluoro-2'-deoxyadenosine or EFdA) on renal tubular cells and islatravir's interactions with organic anion transporters.

Islatravir (ISL; 4'-ethynyl-2-fluoro-2'-deoxyadenosine or EFdA) is a novel reverse transcriptase translocation inhibitor and has a unique structure and high antiviral activity against wild-type and multidrug resistant HIV strains. In this study, we investigated whether islatravir (ISL) can cause kidney damage compared to tenofovir disoproxil fumarate (TDF) and tenofovir (TFV). We also investigated interactions of these drugs with organic anion transporters (OATs). There is a large gap in ISL concentration between the pharmacological dose to proximal tubular cells and the clinical dose. ISL is unlikely to be taken up via OAT1 or OAT3; therefore, OAT1 and OAT3 may not be involved in the injury to tubular cells. Present data strongly suggests that ISL is not toxic to proximal tubules because blood levels of ISL are not high enough to cause kidney damage in the clinical setting.

Hydrophobic Pocket Occupation Design of Difluoro-Biphenyl-Diarylpyrimidines as Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors: from N-Alkylation to Methyl Hopping on the Pyrimidine Ring.

Considering the nonideal metabolic stability of the difluoro-biphenyl-diarylpyrimidine lead compound 4, a series of novel alkylated difluoro-biphenyl-diarylpyrimidines were designed and synthesized based on their structure. Introducing alkyl or substituted alkyl groups on the linker region to block the potential metabolic sensitive sites generated 22 derivatives. Among them, compound 12a with an N-methyl group displayed excellent anti-HIV-1 activity and selectivity. The methyl group was hopped to the central pyrimidine to occupy the small linker region and maintain the water-mediated hydrogen bond observed in the binding of compound 4 with RT. The resulting compound 16y exhibited an improved anti-HIV-1 activity, much lower cytotoxicity, and nanomolar activity toward multiple mutants. In addition, 16y has a better stability in human liver microsomes than 4. Moreover, no apparent in vivo acute toxicity was observed in 16y-treated female, especially pregnant mice. This series of alkylated compounds with highly potency and safety represent a promising lead template for future discovery.

2,4,5-Trisubstituted Pyrimidines as Potent HIV-1 NNRTIs: Rational Design, Synthesis, Activity Evaluation, and Crystallographic Studies.

There is an urgent unmet medical need for novel human immunodeficiency virus type 1 (HIV-1) inhibitors that are effective against a variety of NNRTI-resistance mutations. We report our research efforts aimed at discovering a novel chemotype of anti-HIV-1 agents with improved potency against a variety of NNRTI-resistance mutations in this paper. Structural modifications of the lead K-5a2 led to the identification of a potent inhibitor 16c. 16c yielded highly potent anti-HIV-1 activities and improved resistance profiles compared with the approved drug etravirine. The co-crystal structure revealed the key role of the water networks surrounding the NNIBP for binding and for resilience against resistance mutations, while suggesting further extension of 16c toward the NNRTI-adjacent site as a lead development strategy. Furthermore, 16c demonstrated favorable pharmacokinetic and safety properties, suggesting the potential of 16c as a promising anti-HIV-1 drug candidate.

Avoiding Drug Resistance in HIV Reverse Transcriptase.

HIV reverse transcriptase (RT) is an enzyme that plays a major role in the replication cycle of HIV and has been a key target of anti-HIV drug development efforts. Because of the high genetic diversity of the virus, mutations in RT can impart resistance to various RT inhibitors. As the prevalence of drug resistance mutations is on the rise, it is necessary to design strategies that will lead to drugs less susceptible to resistance. Here we provide an in-depth review of HIV reverse transcriptase, current RT inhibitors, novel RT inhibitors, and mechanisms of drug resistance. We also present novel strategies that can be useful to overcome RT's ability to escape therapies through drug resistance. While resistance may not be completely avoidable, designing drugs based on the strategies and principles discussed in this review could decrease the prevalence of drug resistance.

Design, synthesis, and biological evaluation of piperidinyl-substituted [1,2,4]triazolo[1,5-a]pyrimidine derivatives as potential anti-HIV-1 agents with reduced cytotoxicity.

Taking the previously reported compound BH-7d as the lead, we designed and synthesized a series of piperidinyl-substituted [1,2,4]triazolo[1,5-a]pyrimidines, and their anti-HIV activities as well as cytotoxicities were evaluated. Several compounds exhibited moderate anti-HIV (IIIB) potency, among which 2b was the most active one (EC50  = 4.29 µM). Structure-activity relationships derived from the antiretroviral results were analyzed. Additionally, most compounds demonstrated reduced cytotoxicity (CC50  > 200 µM) compared with those of BH-7d and etravirine. Molecular docking study further revealed the binding conformation of 2b in the binding pocket of HIV-1 reverse transcriptase.

Novel peptides with HIV-1 reverse transcriptase inhibitory activity derived from the fruits of Quercus infectoria.

The HIV-1 reverse transcriptase (HIV-1 RT), which is responsible for transcription of viral RNA genomes into DNA genomes, has become an important target for the treatment of patients with HIV infection. Hydrolyzed peptides from plants are considered a new source of potential drugs. In order to develop new effective inhibitors, peptides extracted from 111 Asian medicinal plants were screened against the HIV-1 RT. The crude hydrolyzed peptides from the fruit peel of Quercus infectoria were selected for purification and peptide sequence determination by HPLC and LC-MS. Two peptides of interest were synthesized, and an IC50 test was performed to determine their ability to inhibit the HIV-1 RT. The IC50 values of the peptides AIHIILI and LIAVSTNIIFIVV were determined to be 274 ± 5.10 nm and 236.4 ± 7.07 nm, respectively. This indicated that these peptides could be further developed as potential HIV-1 RT inhibitors.

Current status of antivirals and druggable targets of SARS CoV-2 and other human pathogenic coronaviruses.

Coronaviridae is a peculiar viral family, with a very large RNA genome and characteristic appearance, endowed with remarkable tendency to transfer from animals to humans. Since the beginning of the 21st century, three highly transmissible and pathogenic coronaviruses have crossed the species barrier and caused deadly pneumonia, inflicting severe outbreaks and causing human health emergencies of inconceivable magnitude. Indeed, in the past two decades, two human coronaviruses emerged causing serious respiratory illness: severe acute respiratory syndrome coronavirus (SARS-CoV-1) and Middle Eastern respiratory syndrome coronavirus (MERS-CoV), causing more than 10,000 cumulative cases, with mortality rates of 10 % for SARS-CoV-1 and 34.4 % for MERS-CoV. More recently, the severe acute respiratory syndrome coronavirus virus 2 (SARS-CoV-2) has emerged in China and has been identified as the etiological agent of the recent COVID-19 pandemic outbreak. It has rapidly spread throughout the world, causing nearly 22 million cases and ∼ 770,000 deaths worldwide, with an estimated mortality rate of ∼3.6 %, hence posing serious challenges for adequate and effective prevention and treatment. Currently, with the exception of the nucleotide analogue prodrug remdesivir, and despite several efforts, there is no known specific, proven, pharmacological treatment capable of efficiently and rapidly inducing viral containment and clearance of SARS-CoV-2 infection as well as no broad-spectrum drug for other human pathogenic coronaviruses. Another confounding factor is the paucity of molecular information regarding the tendency of coronaviruses to acquire drug resistance, a gap that should be filled in order to optimize the efficacy of antiviral drugs. In this light, the present review provides a systematic update on the current knowledge of the marked global efforts towards the development of antiviral strategies aimed at coping with the infection sustained by SARS-CoV-2 and other human pathogenic coronaviruses, displaying drug resistance profiles. The attention has been focused on antiviral drugs mainly targeting viral protease, RNA polymerase and spike glycoprotein, that have been tested in vitro and/or in clinical trials as well as on promising compounds proven to be active against coronaviruses by an in silico drug repurposing approach. In this respect, novel insights on compounds, identified by structure-based virtual screening on the DrugBank database endowed by multi-targeting profile, are also reported. We specifically identified 14 promising compounds characterized by a good in silico binding affinity towards, at least, two of the four studied targets (viral and host proteins). Among which, ceftolozane and NADH showed the best multi-targeting profile, thus potentially reducing the emergence of resistant virus strains. We also focused on potentially novel pharmacological targets for the development of compounds with anti-pan coronavirus activity. Through the analysis of a large set of viral genomic sequences, the current review provides a comprehensive and specific map of conserved regions across human coronavirus proteins which are essential for virus replication and thus with no or very limited tendency to mutate. Hence, these represent key druggable targets for novel compounds against this virus family. In this respect, the identification of highly effective and innovative pharmacological strategies is of paramount importance for the treatment and/or prophylaxis of the current pandemic but potentially also for future and unavoidable outbreaks of human pathogenic coronaviruses.

New indolylarylsulfone non-nucleoside reverse transcriptase inhibitors show low nanomolar inhibition of single and double HIV-1 mutant strains.

We designed and synthesized 21 new indolylarylsulfones (IASs) as new HIV-1 NNRTIs. Among these, IAS 12 exhibited a remarkable antiviral activity against single and double mutants (K103N EC50 = <0.7 nM; Y181C EC50 = <0.7 nM; Y188L EC50 = 21.3 nM; K103N-Y181C EC50 = 6.2 nM), resulting equally or more active than previuosly reported IAS 6 and some approved anti-HIV-1 drugs. Docking and molecular dynamics simulations of compound 12 in complex with WT, Y181C, Y188L, K103N and K103N-Y181C RTs clarified a general binding mode that was consistent with biological results. Kinetic experiments disclosed that derivative 12 preferentially binds WT and K103N-Y181C RTs to binary and ternary complexes, respectively.

The Pharmacogenetics of Efavirenz Metabolism in Children: The Potential Genetic and Medical Contributions to Child Development in the Context of Long-Term ARV Treatment.

Efavirenz (EFV) is a well-known, effective anti-retroviral drug long used in first-line treatment for children and adults with HIV and HIV/AIDS. Due to its narrow window of effective concentrations, between 1 and 4 µg/mL, and neurological side effects at supratherapeutic levels, several investigations into the pharmacokinetics of the drug and its genetic underpinnings have been carried out, primarily with adult samples. A number of studies, however, have examined the genetic influences on the metabolism of EFV in children. Their primary goal has been to shed light on issues of appropriate pediatric dosing, as well as the manifestation of neurotoxic effects of EFV in some children. Although EFV is currently being phased out of use for the treatment of both adults and children, we share this line of research to highlight an important aspect of medical treatment that is relevant to understanding the development of children diagnosed with HIV.

Structure-Based Bioisosterism Yields HIV-1 NNRTIs with Improved Drug-Resistance Profiles and Favorable Pharmacokinetic Properties.

The development of efficacious NNRTIs for AIDS therapy commonly encountered the rapid generation of drug-resistant mutations, which becomes a major impediment to effective anti-HIV treatment. Using a structure-based bioisosterism strategy, a series of piperidine-substituted thiophene[2,3-d]pyrimidine derivatives were designed and synthesized. Compound 9a yielded the greatest potency, exhibiting significantly better anti-HIV-1 activity than ETR against all of the tested NNRTI-resistant HIV-1 strains. In addition, the phenotypic (cross)resistance of 9a and other NRTIs to the different selected HIV-1 strains was evaluated. As expected, no phenotypic cross-resistance against the NRTIs (AZT and PMPA) was observed with the mutant 9ares strain. Furthermore, 9a was identified with improved solubility, lower CYP liability, and hERG inhibition. Remarkably, 9a exhibited optimal pharmacokinetic properties in rats (F = 37.06%) and safety in mice (LD50 > 2000 mg/kg), which highlights 9a as a promising anti-HIV-1 drug candidate.