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Novel 4′-substituted β- d -2′-deoxy-2′-α-fluoro (2′d2′F) nucleoside inhibitors of respiratory syncytial virus (RSV) are reported. The introduction of 4′-substitution onto 2′d2′F nucleoside analogs resulted in compounds demonstrating potent cell based RSV inhibition, improved inhibition of the RSV polymerase by the nucleoside triphosphate metabolites, and enhanced selectivity over incorporation by mitochondrial RNA and DNA polymerases. Selectivity over the mitochondrial polymerases was found to be extremely sensitive to the specific 4′-substitution and not readily predictable. Combining the most potent and selective 4′-groups from N -nucleoside analogs onto a 2′d2′F C -nucleoside analog resulted in the identification of β- d -2′-deoxy-2′-α-fluoro-4′-α-cyano-5-aza-7,9-dideaza adenosine as a promising nucleoside lead for RSV. [ABSTRACT FROM AUTHOR]

Abstract: GS-9148 [(5-(6-amino-purin-9-yl)-4-fluoro-2,5-dihydro-furan-2-yloxymethyl)phosphonic acid] 4 is a novel nucleoside phosphonate HIV-1 reverse transcriptase (RT) inhibitor with a unique resistance profile toward N(t)RTI resistance mutations. To effectively deliver 4 and its active phosphorylated metabolite 15 into target cells, a series of amidate prodrugs were designed as substrates of cathepsin A, an intracellular lysosomal carboxypeptidase highly expressed in peripheral blood mononuclear cells (PBMCs). The ethylalaninyl phosphonamidate prodrug 5 (GS-9131) demonstrated favorable cathepsin A substrate properties, in addition to favorable in vitro intestinal and hepatic stabilities. Following oral dosing (3mg/kg) in Beagle dogs, high levels (>9.0μM) of active metabolite 15 were observed in PBMCs, validating the prodrug design process and leading to the nomination of 5 as a clinical candidate. [Copyright &y& Elsevier]

Abstract: GS-9148 (2′-Fd4AP, 4) has been identified as a nucleoside phosphonate reverse transcriptase (RT) inhibitor with activity against wild-type HIV (EC50 =12μM). Unlike many clinical RT inhibitors, relevant reverse transcriptase mutants (M184V, K65R, 6-TAMs) maintain a susceptibility to 2′-Fd4AP that is similar to wild-type virus. The 2′-fluorine group was rationally designed into the molecule to improve the selectivity profile and in preliminary studies using HepG2 cells, compound 4 showed no measurable effect on mitochondrial DNA content indicating a low potential for mitochondrial toxicity. [Copyright &y& Elsevier]

Abstract: Modified purine analogs of GS-9148 [5-(6-amino-purin-9-yl)-4-fluoro-2,5-dihydro-furan-2-yloxymethyl]-phosphonic acid (2′-Fd4AP) were synthesized and their anti-HIV potency evaluated. The antiviral activity of guanosine analog (2′-Fd4GP) was comparable that of to 2′-Fd4AP in MT-2 cells, but selectivity was reduced. [Copyright &y& Elsevier]

Abstract: A series of nucleoside phosphonate reverse transcriptase (RT) inhibitors have been synthesized and their anti-HIV activity and resistance profiles evaluated. The most potent analog [5-(6-amino-purin-9-yl)-2,5-dihydro-furan-2-yloxymethyl]-phosphonic acid (d4AP) demonstrated a HIV EC50 =2.1μM, and the most favorable resistance profile against HIV-1 variants with K65R, M184V or multiple thymidine analog mutations in RT. [Copyright &y& Elsevier]

Abstract: Phosphonomethoxy nucleoside analogs of the thymine containing nucleoside reverse transcriptase inhibitors (NRTIs), 3′-azido-2′,3′-dideoxythymidine (AZT), 2′,3′-didehydro-2′,3′-dideoxythymidine (d4T), and 2′,3′-dideoxythymidine (ddT), were synthesized. The anti-HIV activity against wild-type and several major nucleoside-resistant strains of HIV-1 was evaluated together with the inhibition of wild-type HIV reverse transcriptase (RT). Phosphonomethoxy analog of d4T, 8 (d4TP), demonstrated antiviral activity with an EC50 value of 26μM, whereas, phosphonomethoxy analogs of ddT, 7 (ddTP), and AZT, 6 (AZTP), were both inactive at concentrations up to 200μM. Bis-isopropyloxymethylcarbonyl (bisPOC) prodrugs improved the anti-HIV activity of 7 and 8 by >150-fold and 29-fold, respectively, allowing for antiviral resistance to be determined. The K65R RT mutant virus was more resistant to the bisPOC prodrugs of 7 and 8 than bisPOC PMPA (tenofovir DF) 1. However, bisPOC prodrug of 7 demonstrated superior resistance toward the RT virus containing multiple thymidine analog mutations (6TAMs) indicating that new phosphonate nucleoside analogs may be suitable for targeting clinically relevant nucleoside resistant HIV-1 strains. [Copyright &y& Elsevier]

The development of potent and selective urokinase-type plasminogen activator (uPA) inhibitors based on the lead molecule 2-(2-hydroxy-3-ethoxyphenyl)-1H-benzimidazole-5-carboxamidine (3a) is described. [Copyright &y& Elsevier]

Graphical abstract Highlights • The structure-guided discovery of a novel BET bromodomain inhibitor is disclosed. • The lead properties were optimized using in-vitro assays and in-vivo PK studies. • The lead compound reduced the in vivo tumor growth two xenograft models. Abstract The bromodomain and extra-terminal (BET) family of proteins, consisting of the bromodomains containing protein 2 (BRD2), BRD3, BRD4, and the testis-specific BRDT, are key epigenetic regulators of gene transcription and has emerged as an attractive target for anticancer therapy. Herein, we describe the discovery of a novel potent BET bromodomain inhibitor, using a systematic structure-based approach focused on improving potency, metabolic stability, and permeability. The optimized dimethylisoxazole aryl-benzimidazole inhibitor exhibited high potency towards BRD4 and related BET proteins in biochemical and cell-based assays and inhibited tumor growth in two proof-of-concept preclinical animal models. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the COVID-19 pandemic, has infected over 260 million people over the past 2 years. Remdesivir (RDV, VEKLURY®) is currently the only antiviral therapy fully approved by the FDA for the treatment of COVID-19. The parent nucleoside of RDV, GS-441524, exhibits antiviral activity against numerous respiratory viruses including SARS-CoV-2, although at reduced in vitro potency compared to RDV in most assays. Here we find in both human alveolar and bronchial primary cells, GS-441524 is metabolized to the pharmacologically active GS-441524 triphosphate (TP) less efficiently than RDV, which correlates with a lower in vitro SARS-CoV-2 antiviral activity. In vivo , African green monkeys (AGM) orally dosed with GS-441524 yielded low plasma levels due to limited oral bioavailability of <10%. When GS-441524 was delivered via intravenous (IV) administration, although plasma concentrations of GS-441524 were significantly higher, lung TP levels were lower than observed from IV RDV. To determine the required systemic exposure of GS-441524 associated with in vivo antiviral efficacy, SARS-CoV-2 infected AGMs were treated with a once-daily IV dose of either 7.5 or 20 mg/kg GS-441524 or IV RDV for 5 days and compared to vehicle control. Despite the reduced lung TP formation compared to IV dosing of RDV, daily treatment with IV GS-441524 resulted in dose-dependent efficacy, with the 20 mg/kg GS-441524 treatment resulting in significant reductions of SARS-CoV-2 replication in the lower respiratory tract of infected animals. These findings demonstrate the in vivo SARS-CoV-2 antiviral efficacy of GS-441524 and support evaluation of its orally bioavailable prodrugs as potential therapies for COVID-19. • GS-441524 and remdesivir both inhibit SARS-CoV-2 in primary human lung cells. • Limited oral bioavailability of GS-441524 in primates necessitates IV administration to yield high plasma concentrations. • Intravenous GS-441524 and remdesivir both reduce SARS-CoV-2 viral burden AGM model. • Antiviral efficacy of GS-441524 suggests prodrugs that increase oral bioavailability are desirable to identify and develop. [ABSTRACT FROM AUTHOR]

The utility of remdesivir treatment in COVID-19 patients is currently limited by the necessity to administer this antiviral intravenously, which has generally limited its use to hospitalized patients. Here, we tested a novel, subcutaneous formulation of remdesivir in the rhesus macaque model of SARS-CoV-2 infection that was previously used to establish the efficacy of remdesivir against this virus in vivo. Compared to vehicle-treated animals, macaques treated with subcutaneous remdesivir from 12 h through 6 days post inoculation showed reduced signs of respiratory disease, a reduction of virus replication in the lower respiratory tract, and an absence of interstitial pneumonia. Thus, early subcutaneous administration of remdesivir can protect from lower respiratory tract disease caused by SARS-CoV-2. • Remdesivir is a nucleotide analog prodrug with broad-spectrum antiviral activity shown to be effective against SARS-CoV-2. • The utility of remdesivir treatment in COVID-19 patients is limited by the necessity to administer it intravenously. • The efficacy of a subcutaneous formulation of remdesivir was tested in the rhesus macaque model of SARS-CoV-2 infection. • Subcutaneous remdesivir reduced respiratory signs, reduced replication in the lungs, and prevented interstitial pneumonia. [ABSTRACT FROM AUTHOR]

Abstract: Ribonucleoside phosphonate analogues containing 2′-α-fluoro modifications were synthesized and their potency evaluated against HCV RNA polymerase. The diphosphophosphonate (triphosphate equivalent) adenine and cytidine analogues displayed potent inhibition of the HCV polymerase in the range of 1.9–2.1μM, but only modest cell-based activity in the HCV replicon. Pro-drugs of the parent nucleoside phosphonates improved the cell-based activity. [Copyright &y& Elsevier]

Abstract: A novel and efficient method for the one-pot synthesis of diamide (bis-amidate) prodrugs of acyclic nucleoside phosphonates, starting from free phosphonic acids or phosphonate diesters is reported. The approach from phosphonate diesters via their bis(trimethylsilyl) esters is highly convenient, eliminates isolation and tedious purification of the phosphonic acids, and affords the corresponding bis-amidates in excellent yields (83–98%) and purity. The methodology has been applied to the synthesis of the potent anticancer agent GS-9219, and symmetrical bis-amidates of other biologically active phosphonic acids. Anti-HIV, antiproliferative, and immunomodulatory activities of the compounds are discussed including the bis-amidate prodrugs 14 and 17 that exhibited anti-HIV activity at submicromolar concentrations with minimal cytotoxicity. [Copyright &y& Elsevier]

Abstract: A diphosphate of a novel cyclopentyl based nucleoside phosphonate with potent inhibition of HIV reverse transcriptase (RT) (20, IC50 =0.13μM) has been discovered. In cell culture the parent phosphonate diacid 9 demonstrated antiviral activity EC50 =16μM, within two-fold of GS-9148, a prodrug of which is currently under clinical investigation, and within 5-fold of tenofovir (PMPA). In vitro cellular metabolism studies using 9 confirmed that the active diphosphate metabolite is produced albeit at a lower efficiency relative to GS-9148. [Copyright &y& Elsevier]

Abstract: An efficient and facile synthesis of a large series of diverse 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides (55 examples of both ribo- and 2′-deoxyribonucleosides), aimed at identifying novel homologues of natural nucleosides, was developed. The key transformation involved nucleophilic substitutions of Tol-protected 6-(mesyloxymethyl)purine nucleosides by primary or secondary amines, alcoholates or thiolates. While the 2′-deoxyribonucleosides were inactive, the ribonucleosides exerted considerable cytostatic effects and some anti-HCV activity with low selectivity. [Copyright &y& Elsevier]

Abstract: An efficient and facile synthesis of a large series of diverse 6-[2-(dialkylamino)vinyl]-, 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, and 6-[2-(alkylsulfanyl)ethyl]purine nucleosides (35 examples of both ribo- and 2′-deoxyribonucleosides) was developed. The key transformations involved conjugate nucleophilic additions of amines, alcoholates, or thiolates to Tol-protected 6-alkylylpurine or 6-vinylpurine nucleosides. 6-[(2-Dialkylamino)vinyl]- and some 6-[(2-dialkylamino)ethyl]purine ribonucleosides exerted significant cytostatic effects and some anti-HCV activity with low selectivity. [Copyright &y& Elsevier]

Abstract: A series of purine l-ribonucleosides 2a–2i bearing diverse C-substituents (alkyl, aryl, hetaryl or hydroxymethyl) in the position 6 were prepared by Pd-catalyzed cross-coupling reactions of 6-chloro-9-(2,3,5-tri-O-acetyl-β-l-ribofuranosyl)purine with the corresponding organometallics followed by deprotection. Unlike their d-ribonucleoside enantiomers that possess strong cytostatic and anti-HCV activity, the l-ribonucleosides were inactive except for 6-benzylpurine nucleoside 2h showing moderate anti-HCV effect in replicon assay. A triphosphate of 2h did not inhibit HCV RNA polymerase. [Copyright &y& Elsevier]

The rational design and synthesis of β-amino-α-hydroxy amide derivatives as reversible inhibitors of methionine aminopeptidase-2 (MetAP2) with anti-proliferative activity against human umbilical vein endothelial cells (HUVECs) is described. [Copyright &y& Elsevier]

The structure-based design of potent and selective urokinase-type plasminogen activator (uPA) inhibitors with 4-aminoarylamidine or 4-aminoarylguanidine S1 binding groups, is described. [Copyright &y& Elsevier]