Synthesis, inhibitory activity and oral dosing formulation of AV5124, the structural analogue of influenza virus endonuclease inhibitor baloxavir

Abstract

Background The development and clinical implementation of the cap-dependent endonuclease (CEN) inhibitor baloxavir marboxil was a breakthrough in influenza therapy, but it was associated with the emergence of drug-resistant variants. Objectives To design and synthesize structural analogues of CEN inhibitors and evaluate their safety, pharmacokinetics and antiviral potency in vitro and in vivo. Methods The drug candidate AV5124 and its active metabolite AV5116 were synthesized based on pharmacophore modelling. Stability in plasma and microsomes, plasma protein binding, cytotoxicity and antiviral activities were assessed in vitro. Pharmacokinetics after IV or oral administration were analysed in CD-1 mice. Acute toxicity and protective efficacy against lethal A(H1N1)pdm09 influenza virus challenge were examined in BALB/c mice. Results Pharmacophore model-assisted, 3D molecular docking predicted key supramolecular interactions of the metal-binding group and bulky hydrophobic group of AV5116 with the CEN binding site (Protein Data Bank code: 6FS6) that are essential for high antiviral activity. AV5116 inhibited influenza virus polymerase complexes in cell-free assays and replication of oseltamivir-susceptible and -resistant influenza A and B viruses at nanomolar concentrations. Notably, AV5116 was equipotent or more potent than baloxavir acid (BXA) against WT (I38-WT) viruses and viruses with reduced BXA susceptibility carrying an I38T polymerase acidic (PA) substitution. AV5116 exhibited low cytotoxicity in Madin–Darby canine kidney cells and lacked mitochondrial toxicity, resulting in favourable selective indices. Treatment with 20 or 50 mg/kg AV5124 prevented death in 60% and 100% of animals, respectively. Conclusions Overall, AV5124 and A5116 are promising inhibitors of the influenza virus CEN and warrant further development as potent anti-influenza agents.

Discovery of a Macrocyclic Influenza Cap-Dependent Endonuclease Inhibitor

“…A schematic illustration of the known modification strategy of baloxavir is displayed in Scheme . − These compounds have demonstrated significant antiviral activity in vitro and/or in vivo . However, with only a few exceptions, the reported scaffold was not able to improve the potency of the baloxavir-resistant strains. In our search for the next generation of CENi that can retain relatively high potency to the baloxavir-resistant PA/I38X variants, we have discovered a “waist-to-tail” macrocyclic compound 8 , which displays a dramatically smaller potency shift between the wild type and PA/I38T variant.…”

“…14 The above-mentioned viral fitness and clinical outcomes from baloxavir-resistant strains underscore the necessity of exploring inhibitors that can maintain efficacy toward them. Several polymerase inhibitors, 11,12,19 other than baloxavir, have been reported in the literature, such as RO-7 (3), 20 AL-794/ALS-033719, 21 AV-5124/AV-5116 (4/5), 22 and ZX-7101A/ZX-7101. 23 A schematic illustration of the known modification strategy of baloxavir is displayed in Scheme 1.…”

“…Several polymerase inhibitors, ,, other than baloxavir, have been reported in the literature, such as RO-7 ( 3 ), AL-794/ALS-033719, AV-5124/AV-5116 ( 4 / 5 ), and ZX-7101A/ZX-7101 . A schematic illustration of the known modification strategy of baloxavir is displayed in Scheme . − These compounds have demonstrated significant antiviral activity in vitro and/or in vivo .…”

Aprotinin—Drug against Respiratory Diseases

“…There are currently seven viral target proteins, including nine antivirals approved for the treatment of influenza ( Table 2 ) [ 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ].…”

In Search of Antiviral Metal-Based Drugs

“…Recently, due to the covid pandemic, more and more researchers are trying to discover and develop metal-based factors with antiviral activity [7,8]. Although there are limited the efforts compared to the solely organic small molecules,…”