Discovery of Sisunatovir (RV521), an Inhibitor of Respiratory Syncytial Virus Fusion.

RV521 is an orally bioavailable inhibitor of respiratory syncytial virus (RSV) fusion that was identified after a lead optimization process based upon hits that originated from a physical property directed hit profiling exercise at Reviral. This exercise encompassed collaborations with a number of contract organizations with collaborative medicinal chemistry and virology during the optimization phase in addition to those utilized as the compound proceeded through preclinical and clinical evaluation. RV521 exhibited a mean IC50 of 1.2 nM against a panel of RSV A and B laboratory strains and clinical isolates with antiviral efficacy in the Balb/C mouse model of RSV infection. Oral bioavailability in preclinical species ranged from 42 to >100% with evidence of highly efficient penetration into lung tissue. In healthy adult human volunteers experimentally infected with RSV, a potent antiviral effect was observed with a significant reduction in viral load and symptoms compared to placebo.

JNJ-5371678, Defining a Role for Fusion Inhibitors in the Treatment of Respiratory Syncytial Virus.

Inhibitors of the respiratory syncytial virus (RSV) fusion protein block entry of the virus into the cell and have shown varying efficacy in a human challenge model of RSV disease. Trials in patient populations are yet to show significant benefits. Jonckers et al. ( J. Med. Chem. 2020, DOI: 10.1021/acs.jmedchem.0c00226) describe the discovery of JNJ-53718678 which can now claim the leading position in clinical evaluation. For RSV inhibitors, the current status of the clinical development of the compound is discussed.

State of the Art in Respiratory Syncytial Virus Drug Discovery and Development.

Respiratory syncytial virus (RSV) is a globally prevalent viral infection with limited treatment options which hospitalizes millions each year. Treatment options have been limited to palivizumab, a monoclonal antibody, approved for prophylaxis in high-risk infants and ribavirin with very limited efficacy and significant safety concerns. This Perspective surveys the range of direct acting antiviral agents (DAAs) that target key steps in the viral life cycle. A number of approaches to DAAs have produced landmark clinical studies over the past few years, notably in fusion and nucleoside inhibitors, and an update of the clinical status of these compounds is provided. Non-nucleoside inhibitors of replication are reviewed in addition to inhibitors of other mechanisms, notably the RSV N and G proteins. This article will provide an informative perspective of the current status of drug discovery targeted at providing an effective therapy for RSV infection.

RSV604, a novel inhibitor of respiratory syncytial virus replication.

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections worldwide, yet no effective vaccine or antiviral treatment is available. Here we report the discovery and initial development of RSV604, a novel benzodiazepine with submicromolar anti-RSV activity. It proved to be equipotent against all clinical isolates tested of both the A and B subtypes of the virus. The compound has a low rate of in vitro resistance development. Sequencing revealed that the resistant virus had mutations within the nucleocapsid protein. This is a novel mechanism of action for anti-RSV compounds. In a three-dimensional human airway epithelial cell model, RSV604 was able to pass from the basolateral side of the epithelium effectively to inhibit virus replication after mucosal inoculation. RSV604, which is currently in phase II clinical trials, represents the first in a new class of RSV inhibitors and may have significant potential for the effective treatment of RSV disease.

1,4-benzodiazepines as inhibitors of respiratory syncytial virus. The identification of a clinical candidate.

Respiratory syncytial virus (RSV) is the cause of one-fifth of all lower respiratory tract infections worldwide and is increasingly being recognized as representing a serious threat to patient groups with poorly functioning or immature immune systems. Racemic 1,4-benzodiazepines show potent anti-RSV activity in vitro. Anti-RSV evaluation of 3-position R- and S-benzodiazepine enantiomers and subsequent optimization of this series resulted in selection of a clinical candidate. Antiviral activity was found to reside mainly in the S-enantiomer, and the R-enantiomers were consistently less active against RSV. Analogues of 1,4-(S)-benzodiazepine were synthesized as part of the lead optimization program at Arrow and tested in the XTT assay. From this exercise, (S)-1-(2-fluorophenyl)-3-(2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]-diazepin-3-yl)-urea, 17b (RSV-604) was identified as a clinical candidate, exhibiting potent anti-RSV activity in the XTT assay, which was confirmed in secondary assays. Compound 17b also possessed a good pharmacokinetic profile and has now progressed into the clinic.

Optimization and SAR for dual ErbB-1/ErbB-2 tyrosine kinase inhibition in the 6-furanylquinazoline series.

Synthetic modifications on a 6-furanylquinazoline scaffold to optimize the dual ErbB-1/ErbB-2 tyrosine kinase inhibition afforded consistent SAR whereby a 4-(3-fluorobenzyloxy)-3-haloanilino provided the best enzyme potency and cellular selectivity. Changes made to the 6-furanyl group had little impact on the enzyme activity, but appeared to dramatically affect the cellular efficacy. The discovery of lapatinib emerged from this work.

1,4-Benzodiazepines as inhibitors of respiratory syncytial virus.

Respiratory syncytial virus (RSV) is the cause of one-fifth of all lower respiratory tract infections worldwide and is increasingly being recognized as a serious threat to patient groups with poorly functioning immune systems. Our approach to finding a novel inhibitor of this virus was to screen a 20 000-member diverse library in a whole cell XTT assay. Parallel assays were carried out in the absence of virus in order to quantify any associated cell toxicity. This identified 100 compounds with IC(50)'s less than 50 muM. A-33903 (18), a 1,4-benzodiazepine analogue, was chosen as the starting point for lead optimization. This molecule was moderately active and demonstrated good pharmacokinetic properties. The most potent compounds identified from this work were A-58568 (47), A-58569 (44), and A-62066 (46), where modifications to the aromatic substitution enhanced potency, and A-58175 (42), where the amide linker was modified.

Discovery and biological evaluation of potent dual ErbB-2/EGFR tyrosine kinase inhibitors: 6-thiazolylquinazolines.

We have identified a novel class of 6-thiazolylquinazolines as potent and selective inhibitors of both ErbB-2 and EGFR tyrosine kinase activity, with IC(50) values in the nanomolar range. These compounds inhibited the growth of both EGFR (HN5) and ErbB-2 (BT474) over-expressing human tumor cell lines in vitro. Using xenograft models of the same cell lines, we found that the compounds given orally inhibited in vivo tumor growth significantly compared with control animals.

Small molecule inhibitors of the class 1 receptor tyrosine kinase family.

This review covers literature describing research progress in erbB family tyrosine kinase inhibition over the last year. Excellent recent reviews are available, thus we have focussed on current developments of leading small molecule drug candidates as well as their erbB family inhibition profile. The most advanced erbB family tyrosine kinase (TK) inhibitors are demonstrating promising anti-cancer activity in clinical trials and are discussed. Several inhibition strategies are emerging: EGFR TK selective, irreversible TK inhibition and dual EGFR/erbB2 TK inhibitors. While small structural differences are seen in the leading compounds, the variations in their inhibition profiles and compound properties suggest that biological systems judge structural diversity differently. The readers' attention is drawn to common issues of selectivity and potency generally encountered with kinase inhibitors.