Willard Lew

Discovery and Development of GS 4104 (oseltamivir) An Orally Active Influenza Neuraminidase Inhibitor

Rational drug design utilizing available X-ray crystal structures of sialic acid analogues bound to the active site of influenza virus neuraminidase has led to the discovery of a series of potent carbocyclic influenza neuraminidase inhibitors. From this series, GS 4104 (oseltamivir, TAMIFLU ) has emerged as a promising antiviral for the treatment and prophylaxis of human influenza infection. This article will summarize the design, discovery, and development of oseltamivir as an oral therapeutic to treat influenza infection.

Discovery of a potent and selective aurora kinase inhibitor.

This communication describes the discovery of a novel series of Aurora kinase inhibitors. Key SAR and critical binding elements are discussed. Some of the more advanced analogues potently inhibit cellular proliferation and induce phenotypes consistent with Aurora kinase inhibition. In particular, compound 21 (SNS-314) is a potent and selective Aurora kinase inhibitor that exhibits significant activity in pre-clinical in vivo tumor models.

A new series of C3-aza carbocyclic influenza neuraminidase inhibitors: synthesis and inhibitory activity☆

The synthesis and influenza neuraminidase inhibitory activity of a new series of C3-aza carbocyclic neuraminidase inhibitors are described. Analogues 3c and 3j, bearing a 3-pentyl group, exhibit influenza A inhibitory activities comparable to that of 1.

Structure-activity relationships of carbocyclic influenza neuraminidase inhibitors

Abstract The structure-activity relationships (SAR) for a new class of potent inhibitors (1) of influenza neuraminidase are described. Systematic modifications of substituents at the C-3, C-4, and C-5 positions of the carbocyclic ring were performed to establish fundamental SAR to assist in the design of potent inhibitors with activity against both of influenza A and B viruses.

Preclinical characterization of GS-9669, a Thumb Site II Inhibitor of the Hepatitis C Virus NS5B Polymerase

ABSTRACT GS-9669 is a highly optimized thumb site II nonnucleoside inhibitor of the hepatitis C virus (HCV) RNA polymerase, with a binding affinity of 1.35 nM for the genotype (GT) 1b protein. It is a selective inhibitor of HCV RNA replication, with a mean 50% effective concentration (EC50) of ≤11 nM in genotype 1 and 5 replicon assays, but lacks useful activity against genotypes 2 to 4. The M423T mutation is readily generated clinically upon monotherapy with the thumb site II inhibitors filibuvir and lomibuvir, and it is notable that GS-9669 exhibited only a 3-fold loss in potency against this variant in the genotype 1b replicon. Rather than M423T, resistance predominantly tracks to residues R422K and L419M and residue I482L in GT 1b and 1a replicons, respectively. GS-9669 exhibited at least additive activity in combination with agents encompassing four other direct modes of action (NS3 protease, NS5A, NS5B via an alternative allosteric binding site, and NS5B nucleotide) as well as with alpha interferon or ribavirin in replicon assays. It exhibited high metabolic stability in in vitro human liver microsomal assays, which, in combination with its pharmacokinetic profiles in rat, dog, and two monkey species, is predictive of good human pharmacokinetics. GS-9669 is well suited for combination with other orally active, direct-acting antiviral agents in the treatment of genotype 1 chronic HCV infection. (This study has been registered at ClinicalTrials.gov under registration number NCT01431898.)

Carbocyclic influenza neuraminidase inhibitors possessing a C3-Cyclic amine side chain : Synthesis and inhibitory activity

As part of our continuing work in the area of influenza neuraminidase inhibitors, a series of C3-aza inhibitors possessing a cyclic amine side chain was synthesized and evaluated for influenza neuraminidase inhibitory activity. Analogues possessing a six-, seven- and eight-membered ring, 4c-e, respectively, at the C3 position exhibited excellent influenza B neuraminidase inhibition.

2-Aminobenzimidazoles as potent Aurora kinase inhibitors

This Letter describes the discovery and key structure-activity relationship (SAR) of a series of 2-aminobenzimidazoles as potent Aurora kinase inhibitors. 2-Aminobenzimidazole serves as a bioisostere of the biaryl urea residue of SNS-314 (1c), which is a potent Aurora kinase inhibitor and entered clinical testing in patients with solid tumors. Compared to SNS-314, this series of compounds offers better aqueous solubility while retaining comparable in vitro potency in biochemical and cell-based assays; in particular, 6m has also demonstrated a comparable mouse iv PK profile to SNS-314.

Water-soluble prodrugs of an Aurora kinase inhibitor.

Compound 1 (SNS-314) is a potent and selective Aurora kinase inhibitor that is currently in clinical trials in patients with advanced solid tumors. This communication describes the synthesis of prodrug derivatives of 1 with improved aqueous solubility profiles. In particular, phosphonooxymethyl-derived prodrug 2g has significantly enhanced solubility and is converted to the biologically active parent (1) following iv as well as po administration to rodents.

Discovery of GS-9669, a Thumb Site II Non-Nucleoside Inhibitor of NS5B for the Treatment of Genotype 1 Chronic Hepatitis C Infection

Investigation of thiophene-2-carboxylic acid HCV NS5B site II inhibitors, guided by measurement of cell culture medium binding, revealed the structure-activity relationships for intrinsic cellular potency. The pharmacokinetic profile was enhanced through incorporation of heterocyclic ethers on the N-alkyl substituent. Hydroxyl groups were incorporated to modulate protein binding. Intrinsic potency was further improved through enantiospecific introduction of an olefin in the N-acyl motif, resulting in the discovery of the phase 2 clinical candidate GS-9669. The unexpected activity of this compound against the clinically relevant NS5B M423T mutant, relative to the wild type, was shown to arise from both the N-alkyl substituent and the N-acyl group.

Design and synthesis of 2-amino-pyrazolopyridines as Polo-like kinase 1 inhibitors.

A series of 2-amino-isoxazolopyridines was designed and synthesized as Polo-like kinase (Plk) inhibitors. Key SAR and crystallographic data are discussed. More advanced analogues inhibit Plk1 with good enzymatic activity and modest cell-based activity. Differential selectivity among the three Plk isoforms is observed.