ABSTRACT
A discovery program targeting respiratory syncytial virus (RSV) identified C-nucleoside 4 (RSV A2 EC50 = 530 nM) as a phenotypic screening lead targeting the RSV RNA-dependent RNA polymerase (RdRp). Prodrug exploration resulted in the discovery of remdesivir (1, GS-5734) that is >30-fold more potent than 4 against RSV in HEp-2 and NHBE cells. Metabolism studies in vitro confirmed the rapid formation of the active triphosphate metabolite, 1-NTP, and in vivo studies in cynomolgus and African Green monkeys demonstrated a >10-fold higher lung tissue concentration of 1-NTP following molar normalized IV dosing of 1 compared to that of 4. A once daily 10 mg/kg IV administration of 1 in an African Green monkey RSV model demonstrated a >2-log10 reduction in the peak lung viral load. These early data following the discovery of 1 supported its potential as a novel treatment for RSV prior to its development for Ebola and approval for COVID-19 treatment.
Subject(s)
Adenosine Monophosphate/analogs & derivatives , Alanine/analogs & derivatives , Antiviral Agents/pharmacology , Prodrugs/pharmacology , Respiratory Syncytial Virus Infections/drug therapy , Respiratory Syncytial Virus, Human/drug effects , Adenosine Monophosphate/pharmacology , Alanine/pharmacology , Animals , Antiviral Agents/chemistry , Antiviral Agents/pharmacokinetics , Caco-2 Cells , Cells, Cultured , Chlorocebus aethiops , Disease Models, Animal , Dogs , Drug Evaluation, Preclinical/methods , Epithelial Cells/virology , Humans , Macaca fascicularis , Male , Prodrugs/chemistry , Prodrugs/pharmacokinetics , Rats, Sprague-Dawley , Respiratory Syncytial Virus Infections/virology , Structure-Activity Relationship , Tissue Distribution , Tubercidin/analogs & derivatives , Tubercidin/chemistry , Viral LoadABSTRACT
The recent Ebola virus (EBOV) outbreak in West Africa was the largest recorded in history with over 28,000 cases, resulting in >11,000 deaths including >500 healthcare workers. A focused screening and lead optimization effort identified 4b (GS-5734) with anti-EBOV EC50 = 86 nM in macrophages as the clinical candidate. Structure activity relationships established that the 1'-CN group and C-linked nucleobase were critical for optimal anti-EBOV potency and selectivity against host polymerases. A robust diastereoselective synthesis provided sufficient quantities of 4b to enable preclinical efficacy in a non-human-primate EBOV challenge model. Once-daily 10 mg/kg iv treatment on days 3-14 postinfection had a significant effect on viremia and mortality, resulting in 100% survival of infected treated animals [ Nature 2016 , 531 , 381 - 385 ]. A phase 2 study (PREVAIL IV) is currently enrolling and will evaluate the effect of 4b on viral shedding from sanctuary sites in EBOV survivors.
Subject(s)
Alanine/analogs & derivatives , Amides/chemistry , Hemorrhagic Fever, Ebola/drug therapy , Phosphoric Acids/chemistry , Prodrugs/chemistry , Prodrugs/pharmacology , Ribonucleotides/chemistry , Virus Diseases/drug therapy , Adenosine Monophosphate/analogs & derivatives , Alanine/chemistry , Cell Line , Drug Discovery , Humans , Microbial Sensitivity Tests , Prodrugs/chemical synthesis , Structure-Activity RelationshipABSTRACT
Novel 4'-substituted ß-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 ß-D-2'-deoxy-2'-α-fluoro-4'-α-cyano-5-aza-7,9-dideaza adenosine as a promising nucleoside lead for RSV.
Subject(s)
Adenosine/chemistry , Antiviral Agents/chemistry , DNA-Directed DNA Polymerase/chemistry , Nucleic Acid Synthesis Inhibitors/chemistry , RNA-Dependent RNA Polymerase/antagonists & inhibitors , RNA/chemistry , Respiratory Syncytial Viruses/enzymology , Respiratory Syncytial Viruses/physiology , Adenosine/chemical synthesis , Adenosine/pharmacology , Antiviral Agents/chemical synthesis , Antiviral Agents/pharmacology , Aza Compounds/chemistry , DNA-Directed DNA Polymerase/metabolism , Drug Evaluation, Preclinical , Nucleic Acid Synthesis Inhibitors/chemical synthesis , Nucleic Acid Synthesis Inhibitors/pharmacology , RNA/metabolism , RNA, Mitochondrial , RNA-Dependent RNA Polymerase/metabolism , Respiratory Syncytial Viruses/drug effects , Structure-Activity Relationship , Virus Replication/drug effectsABSTRACT
Pteridinone-based Toll-like receptor 7 (TLR7) agonists were identified as potent and selective alternatives to the previously reported adenine-based agonists, leading to the discovery of GS-9620. Analogues were optimized for the immunomodulatory activity and selectivity versus other TLRs, based on differential induction of key cytokines including interferon α (IFN-α) and tumor necrosis factor α (TNF-α). In addition, physicochemical properties were adjusted to achieve desirable in vivo pharmacokinetic and pharmacodynamic properties. GS-9620 is currently in clinical evaluation for the treatment of chronic hepatitis B (HBV) infection.
Subject(s)
Antiviral Agents/pharmacology , Hepatitis B, Chronic/drug therapy , Pteridines/pharmacology , Toll-Like Receptor 7/agonists , Administration, Oral , Animals , Antiviral Agents/chemistry , Antiviral Agents/metabolism , Antiviral Agents/pharmacokinetics , Dogs , Drug Evaluation, Preclinical , Female , Humans , Male , Mice , Microsomes, Liver/metabolism , Models, Molecular , Protein Conformation , Pteridines/chemistry , Pteridines/metabolism , Pteridines/pharmacokinetics , Rats , Structure-Activity Relationship , Substrate Specificity , Toll-Like Receptor 7/chemistry , Toll-Like Receptor 7/metabolismABSTRACT
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 1.9-2.1 µM, but only modest cell-based activity in the HCV replicon. Pro-drugs of the parent nucleoside phosphonates improved the cell-based activity.