Discovery of clinical candidate Sivopixant (S-600918): Lead optimization of dioxotriazine derivatives as selective P2X3 receptor antagonists.

In previous work, we discovered a lead compound and conducted initial SAR studies on a novel series of dioxotriazines to identify the compound as one of the P2X3 receptor antagonists. This compound showed high P2X3 receptor selectivity and a strong analgesic effect. Although not selected for clinical development, the compound was evaluated from various aspects as a tool compound. In the course of the following study, the molecular structures of the dioxotriazines were modified based on pharmacokinetic/pharmacodynamic (PK/PD) analyses. As a result of these SAR studies, Sivopixant (S-600918) was identified as a clinical candidate with potent and selective antagonistic activity (P2X3 IC50, 4.2 nM; P2X2/3 IC50, 1100 nM) and a strong analgesic effect in the rat partial sciatic nerve ligation model (Seltzer model) of allodynia (ED50, 0.4 mg/kg).

Rational Design of Novel 1,3-Oxazine Based ß-Secretase (BACE1) Inhibitors: Incorporation of a Double Bond To Reduce P-gp Efflux Leading to Robust Aß Reduction in the Brain.

Accumulation of Aß peptides is a hallmark of Alzheimer's disease (AD) and is considered a causal factor in the pathogenesis of AD. ß-Secretase (BACE1) is a key enzyme responsible for producing Aß peptides, and thus agents that inhibit BACE1 should be beneficial for disease-modifying treatment of AD. Here we describe the discovery and optimization of novel oxazine-based BACE1 inhibitors by lowering amidine basicity with the incorporation of a double bond to improve brain penetration. Starting from a 1,3-dihydrooxazine lead 6 identified by a hit-to-lead SAR following HTS, we adopted a p Ka lowering strategy to reduce the P-gp efflux and the high hERG potential leading to the discovery of 15 that produced significant Aß reduction with long duration in pharmacodynamic models and exhibited wide safety margins in cardiovascular safety models. This compound improved the brain-to-plasma ratio relative to 6 by reducing P-gp recognition, which was demonstrated by a P-gp knockout mouse model.

Discovery of novel 5-hydroxy-4-pyridone-3-carboxy acids as potent inhibitors of influenza Cap-dependent endonuclease.

We report the discovery of a novel series of influenza Cap-dependent EndoNuclease (CEN) inhibitors based on the 4-pyridone-carboxylic acid (PYXA) scaffold, which were found from our chelate library. Our SAR research revealed the lipophilic domain to be the key to CEN inhibition. In particular, the position between the chelate and the lipophilic domain in the derivatives was essential for enhancing the potency. Our study, based on virtual modeling, led to the identification of 2y as a potent CEN inhibitor with an IC50 of 5.12nM.

Structure-activity relationship studies and discovery of a potent transient receptor potential vanilloid (TRPV1) antagonist 4-[3-chloro-5-[(1S)-1,2-dihydroxyethyl]-2-pyridyl]-N-[5-(trifluoromethyl)-2-pyridyl]-3,6-dihydro-2H-pyridine-1-carboxamide (V116517) as a clinical candidate for pain management.

A series of novel tetrahydropyridinecarboxamide TRPV1 antagonists were prepared and evaluated in an effort to optimize properties of previously described lead compounds from piperazinecarboxamide series. The compounds were evaluated for their ability to block capsaicin and acid-induced calcium influx in CHO cells expressing human TRPV1. The most potent of these TRPV1 antagonists were further characterized in pharmacokinetic, efficacy, and body temperature studies. On the basis of its pharmacokinetic, in vivo efficacy, safety, and toxicological properties, compound 37 was selected for further evaluation in human clinical trials.

Combining symmetry elements results in potent naphthyridinone (NTD) HIV-1 integrase inhibitors.

A series of naphthyridinone HIV-1 integrase strand-transfer inhibitors have been designed based on a psdeudo-C2 symmetry element present in the two-metal chelation pharmacophore. A combination of two distinct inhibitor binding modes resulted in potent inhibition of the integrase strand-transfer reaction in the low nM range. Effects of aryl and N1 substitutions are disclosed including the impact on protein binding adjusted antiviral activity.

Synthesis and antiviral activity of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV integrase inhibitors.

The medicinal chemistry and structure-activity relationships for a novel series of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV-integrase inhibitors are disclosed. Substituent effects were evaluated at the N-1, C-3, and 7-benzyl positions of the naphthyridinone ring system. Low nanomolar IC(50) values were achieved in an HIV-integrase strand transfer assay with both carboxylic ester and carboxamide groups at C-3. More importantly, several carboxamide congeners showed potent antiviral activity in cellular assays. A 7-benzyl substituent was found to be critical for potent enzyme inhibition, and an N-(2-methoxyethyl)carboxamide moiety at C-3 significantly reduced plasma protein binding effects in vitro. Pharmacokinetic data in rats for one carboxamide analogue demonstrated oral bioavailability and reasonable in vivo clearance.