Synthesis and SAR studies of potent HIV protease inhibitors containing novel dimethylphenoxyl acetates as P2 ligands

Isopropyl substituted 4-thioazolyl valine side chains are highly optimized P(2)-P(3) ligands for C2 symmetry-based HIV protease inhibitors, as exemplified by the drug ritonavir. Replacement of the side chain with the conformationally constrained hexahydrofurofuranyloxy P(2) ligand in combination with a dimethylphenoxyacetate on the other end of the ritonavir core diamine yielded highly potent HIV protease inhibitors. The in vitro antiviral activity in MT4 cells increased by 10- and 20-fold, respectively, in the absence and presence of 50% human serum compared to ritonavir. The structure-activity relationships of inhibitor series with this combination of ligands were investigated. Preliminary pharmacokinetic studies in rats indicated rapid elimination of the inhibitors from the blood, and the plasma levels were not significantly enhanced by coadministration with ritonavir. However, the novel structural features and the high intrinsic antiviral potency of this series provides potential for the future exploration of prodrug strategies.     

Synthesis of Novel Acyclic Nucleoside Analogues with Anti-Retroviral Activity

A series of novel acyclic thymine nucleoside analogues were prepared by the Mitsunobu reaction from appropriately protected chiral triols. The enantiomeric triols were obtained from substituted γ-lactone acids, prepared by asymmetric oxidation of 3-substituted-1,2-cyclopentanediones. The cytotoxic activity of new analogues was evaluated on MCF-7 human breast cancer and HeLa cells, and antiviral activities on human immunodeficiency virus type 1 and hepatitis C virus models. The synthesized compounds revealed specific anti-retroviral activity and no cytotoxic side effects.     

A new splice variant of the human guanylate-binding protein 3 mediates anti-influenza activity through inhibition of viral transcription and replication

Guanylate-binding proteins (GBPs) belong to the family of large GTPases that are induced in response to interferons. GBPs contain an N-terminal globular GTPase domain and a C-terminal α-helical regulatory domain that are connected by a short middle domain. Antiviral activity against vesicular stomatitis virus and encephalomyocarditis virus has been shown for hGBP-1; however, no anti-influenza virus properties for GBPs have been described to date. Here we show that hGBP-1 and hGBP-3 possess anti-influenza viral activity. Furthermore, we have identified a novel splice variant of hGBP-3, named hGBP-3ΔC, with a largely modified C-terminal α-helical domain. While all three GBP isoforms were up-regulated on influenza virus infection, hGBP-3ΔC showed the most prominent antiviral activity in epithelial cells. Mutational analysis of hGBPs revealed that the globular domain is the principal antiviral effector domain, and GTP-binding, but not hydrolysis, is necessary for antiviral action. Furthermore, we showed that hGBP-3ΔC strongly represses the activity of the viral polymerase complex, which results in decreased synthesis of viral vRNA, cRNA, mRNA, and viral proteins, as well.     

Antiviral activities of Janus-type nucleosides and their related oxime-intermediates

Herpes simplex virus (HSV) infection has been recognized as the most common mucosal disease in humans, manifesting as a life-threatening infection especially for patients with compromised immunity. When combined with the emergence of resistance due to the long-term use of classical antiviral agents, these threats make novel therapeutics for HSV a clinically necessity. We therefore designed and synthesized a series of Janus-type nucleosides by combining the natural genetic alphabets into a singular nucleoside structural unit. We also synthesized a series of new compounds and systematically evaluated their antiviral activity and structure-antiviral activity relationship. The results indicated that both nucleosides and their related intermediates exhibited high anti-HSV-1 activity. Compounds HY17 and HY19, in particular, possessed excellent anti-HSV-1 activity with IC₅₀ values of 0.05 and 0.04 µg/mL, respectively. They also showed broad-spectrum antiviral activity against a multitude of diverse viruses, such as HSV-2, influenza virus A (H3N2), CVB3, HBV, HCV, and HPV. These results suggest that once their mechanisms are fully elucidated, these compounds will prove to be promising candidates as antiviral agents.     

Pyrazolopyridine antiherpetics: SAR of C2' and C7 amine substituents

A novel series of potent pyrazolo[1,5-a]pyridine inhibitors of herpes simplex virus 1 replication have been identified. Several complimentary synthetic methods were developed to allow facile access to a diverse set of analogs from common late stage intermediates. Detailed examination of the amine substituents at the C2' position of the pyrimidine and C7 position of the core pyrazolopyridine is described. The antiviral data suggests that non-polar amines are preferred for optimal activity. Additionally, the 2' position has been shown to require an NH group to retain activity levels similar to that of the gold standard acyclovir.     

Synthesis, structure-activity relationship and in vitro biological evaluation of N-arylethyl isoquinoline derivatives as Coxsackievirus B3 inhibitors

Currently, there is no approved antiviral drug for the infection caused by enteroviruses. A series of novel N-arylethyl isoquinoline derivatives defined with substituents on the ring A and C were designed, synthesized and evaluated in vitro for their activities against Coxsackievirus B3 (CVB3). The primary structure-activity relationship revealed that substituents on the ring A were not beneficial for the activity. Among these analogs synthesized, compound 7f bearing a methylenedioxy at the R(4) and R(5) positions afforded an anti-CVB3 activity and a reasonable selectivity index (SI=26.8); furthermore, 7f exhibited a moderate activity against enterovirus 71 (EV71) with SI value of 9.0. Thus it has been selected as an anti-enteroviral lead compound for further investigation.     

Synthesis of guanidino analogues of PMPDAP and their immunobiological activity

A series of novel 9-, 7- and 3-substituted 2- or 6-guanidinopurines as analogues of potent antiviral and immunobiologically active compound enantiomers of PMPDAP was synthesized and evaluated for their biological activity. Compounds containing the combination of guanidino and amino group at the purine moiety enhanced the interferon-gamma-triggered NO production in murine macrophages and stimulated the secretion of cytokines and chemokines in both murine macrophages and human peripheral blood mononuclear cells. The most active compounds are 27 and 54. None of the compounds tested exhibited any significant cytostatic effect or antiviral effect.     

New quaternary ammonium camphor derivatives and their antiviral activity,genotoxic effects and cytotoxicity

The synthesis and biological evaluation of a novel series of dimeric camphor derivatives are described. The resulting compounds were studied for their antiviral activity, cyto- and genotoxicity. Compounds 3a and 3d in which the quaternary nitrogen atoms are separated by the C5H10 and С9H18 aliphatic chain, exhibited the highest efficiency as an agent inhibiting the reproduction of the influenza virus A(H1N1)pdm09. The cytotoxicity data of compounds 3 and 4 revealed their moderate activity against malignant cell lines; compound 3f had the highest activity for the CEM-13 cells. These results show close agreement with the data of independent studies on toxicity of these compounds, in particular that the toxicity of compounds strongly depends on spacer length.     

Monomeric APOBEC3G is catalytically active and has antiviral activity

APOBEC3G (APO3G) is a cytidine deaminase that restricts replication of vif-defective human immunodeficiency virus type 1 (HIV-1). Like other members of the cellular deaminase family, APO3G has the propensity to form homo-multimers. In the current study, we investigated the functional determinants for multimerization of human APO3G and studied the role of APO3G multimerization for catalytic activity, virus encapsidation, and antiviral activity. We found that human APO3G is capable of forming multimeric complexes in transfected HeLa cells. Interestingly, multimerization of APO3G was exquisitely sensitive to RNase treatment, suggesting that interaction of APO3G subunits is facilitated or stabilized by an RNA bridge. Mutation of a conserved cysteine residue (C97) that is part of an N-terminal zinc-finger motif in APO3G abolished multimerization of APO3G; however, the C97 mutation inhibited neither in vitro deaminase activity nor antiviral function of APO3G. These results suggest that monomeric APO3G is both catalytically active and has antiviral activity. Interference studies employing either catalytically inactive or packaging-incompetent APO3G variants suggest that wild-type APO3G is packaged into HIV-1 particles in monomeric form. These results provide novel insights into the catalytic function and antiviral property of APO3G and demonstrate an important role for C97 in the RNA-dependent multimerization of this protein.     

Novel P1 chain-extended HIV protease inhibitors possessing potent anti-HIV activity and remarkable inverse antiviral resistance profiles

A novel series of tyrosine-derived HIV protease inhibitors was synthesized and evaluated for in vitro antiviral activity against wild-type virus and two protease inhibitor-resistant viruses. All of the compounds had wild-type antiviral activities that were similar to or greater than several currently marketed HIV protease inhibitors. In addition, a number of compounds in this series were more potent against the drug-resistant mutant viruses than they were against wild-type virus.     

Synthesis and antiviral activities of novel N-alkoxy-arylsulfonamide-based HIV protease inhibitors

A series of novel N-alkoxy-arylsulfonamide HIV protease inhibitors with low picomolar enzyme activity and single digit nanomolar antiviral activity is disclosed.     

Simple synthesis of novel acyclic (e)-bromovinyl nucleosides as potential antiviral agents

In these study, novel acyclic (E)-bromovinyl nucleosides were synthesized as potential antiviral agents. The coupling of the allylic bromide 9 with bases (thymine, uracil, 5-fluorouracil, 5-iodouracil, cytosine, adenine) afforded a series of novel acyclic nucleosides. The synthesized compounds were evaluated for their antiviral activity against various viruses such as HIV-1, HSV-1, HSV-2, and HCMV. 5-Iodouracil analogue 19 showed weak anti-HIV-1 activity.     

Imidazo[1,2-a]pyridines with potent activity against herpesviruses

Synthesis of a series of 2-aryl-3-pyrimidyl-imidazo[1,2-a]pyridines with potent activity against herpes simplex viruses is described. Synthetic approaches allowing for variation of the 2-aryl, 3-heteroaryl as well as other imidazopyridine substituents are outlined and resulting effects on antiviral activity are highlighted. Several compounds with in vitro antiviral activity similar or better than acyclovir are described.     

Ultra-potent P1 modified arylsulfonamide HIV protease inhibitors: the discovery of GW0385

A novel series of P1 modified HIV protease inhibitors was synthesized and evaluated for in vitro antiviral activity against wild-type virus and protease inhibitor-resistant viruses. Optimization of the P1 moiety resulted in compounds with femtomolar enzyme activities and cellular antiviral activities in the low nanomolar range culminating in the identification of clinical candidate GW0385.     

Novel arylsulfonamides possessing sub-picomolar HIV protease activities and potent anti-HIV activity against wild-type and drug-resistant viral strains

A novel series of P1' chain-extended arylsufonamides was synthesized and evaluated for wild-type HIV protease inhibitory activity and in vitro antiviral activity against wild type virus and two protease inhibitor-resistant mutant viruses. All of the compounds showed dramatic increases in enzyme activity as compared to the currently marketed HIV protease inhibitors amprenavir, indinavir, and nelfinavir. In addition, significant improvements in antiviral potencies against wild type and the two mutant viruses were also realized.     

Synthesis and anti-HIV-1 activity of a novel series of 1,4,2-benzodithiazine-dioxides

Previously, we discovered a series of novel benzodithiazines-dioxides with both antiviral and anticancer activities. In order to design compounds with distinct antiviral properties, we prepared new compounds with modifications on the imidazole and pyrimidine rings. Herein, we present the synthesis and antiviral activity of 8-chloro-2,3-dihydroimidazo[1,2-b][1,4,2]benzodithiazine 5,5-dioxides (22, 23, 30, and 31) and 9-chloro-2,3,4-trihydropyrimido[1,2-b][1,4,2]benzodithiazine 6,6-dioxides (14, 24, 25, and 27). We successfully identified a lead compound with remarkable anti-HIV-1 activity (EC(50)=0.09microM). These compounds showed minimal cytotoxicity and are therefore suitable for antiviral development.     

Design and optimisation of potent gp120-CD4 inhibitors

The synthesis and structure–activity relationship of a series of novel gp120-CD4 inhibitors are described. Pharmacokinetic studies and antiviral spectrum assessment of lead compounds led to the identification of compound 36, a potent gp120-CD4 inhibitor which exhibited antiviral potency across a spectrum of 25 clade B isolates.     

Synthesis and antiviral activity of novel aza-acyclonucleosides

We have prepared a series of novel aza-acyclonucleosides as potential antiviral agents. These compounds were prepared from diethanolamine and the desired purine or pyrimidine base via a Mitsunobu coupling. No antiviral activity was observed against either HSV-1 or HCMV.