Neuroactive Steroid N-Methyl-d-aspartate Receptor Positive Allosteric Modulators: Synthesis, SAR, and Pharmacological Activity.

Neuroactive steroids (NASs) play a pivotal role in maintaining homeostasis is the CNS. We have discovered that one NAS in particular, 24(S)-hydroxycholesterol (24(S)-HC), is a positive allosteric modulator (PAM) of NMDA receptors. Using 24(S)-HC as a chemical starting point, we have identified other NASs that have good in vitro potency and efficacy. Herein, we describe the structure activity relationship and pharmacokinetic optimization of this series that ultimately led to SGE-301 (42). We demonstrate that SGE-301 enhances long-term potentiation (LTP) in rat hippocampal slices and, in a dose-dependent manner, improves cognition in a rat social recognition study.

1,2,4-Triazolsulfone: A novel isosteric replacement of acylsulfonamides in the context of NaV1.7 inhibition.

Recently, the identification of several classes of aryl sulfonamides and acyl sulfonamides that potently inhibit NaV1.7 and demonstrate high levels of selectivity over other NaV isoforms have been reported. The fully ionizable nature of these inhibitors has been shown to be an important part of the pharmacophore for the observed potency and isoform selectivity. The requirement of this functionality, however, has presented challenges associated with optimization toward inhibitors with drug-like properties and minimal off-target activity. In an effort to obviate these challenges, we set out to develop an orally bioavailable, selective NaV1.7 inhibitor, lacking these acidic functional groups. Herein, we report the discovery of a novel series of inhibitors wherein a triazolesulfone has been designed to serve as a bioisostere for the acyl sulfonamide. This work culminated in the delivery of a potent series of inhibitors which demonstrated good levels of selectivity over NaV1.5 and favorable pharmacokinetics in rodents.

Discovery of a biarylamide series of potent, state-dependent NaV1.7 inhibitors.

The NaV1.7 ion channel has garnered considerable attention as a target for the treatment of pain. Herein we detail the discovery and structure-activity relationships of a novel series of biaryl amides. Optimization led to the identification of several state-dependent, potent and metabolically stable inhibitors which demonstrated promising levels of selectivity over NaV1.5 and good rat pharmacokinetics. Compound 18, which demonstrated preferential inhibition of a slow inactivated state of NaV1.7, was advanced into a rat formalin study where upon reaching unbound drug levels several fold over the rat NaV1.7 IC50 it failed to demonstrate a robust reduction in nociceptive behavior.

The discovery of benzoxazine sulfonamide inhibitors of NaV1.7: Tools that bridge efficacy and target engagement.

The voltage-gated sodium channel NaV1.7 has received much attention from the scientific community due to compelling human genetic data linking gain- and loss-of-function mutations to pain phenotypes. Despite this genetic validation of NaV1.7 as a target for pain, high quality pharmacological tools facilitate further understanding of target biology, establishment of target coverage requirements and subsequent progression into the clinic. Within the sulfonamide class of inhibitors, reduced potency on rat NaV1.7 versus human NaV1.7 was observed, rendering in vivo rat pharmacology studies challenging. Herein, we report the discovery and optimization of novel benzoxazine sulfonamide inhibitors of human, rat and mouse NaV1.7 which enabled pharmacological assessment in traditional behavioral rodent models of pain and in turn, established a connection between formalin-induced pain and histamine-induced pruritus in mice. The latter represents a simple and efficient means of measuring target engagement.

Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency and Pharmacokinetics While Mitigating Metabolic Liabilities.

Several reports have recently emerged regarding the identification of heteroarylsulfonamides as NaV1.7 inhibitors that demonstrate high levels of selectivity over other NaV isoforms. The optimization of a series of internal NaV1.7 leads that address a number of metabolic liabilities including bioactivation, PXR activation, as well as CYP3A4 induction and inhibition led to the identification of potent and selective inhibitors that demonstrated favorable pharmacokinetic profiles and were devoid of the aforementioned liabilities. The key to achieving this within a series prone to transporter-mediated clearance was the identification of a small range of optimal cLogD values and the discovery of subtle PXR SAR that was not lipophilicity dependent. This enabled the identification of compound 20, which was advanced into a target engagement pharmacodynamic model where it exhibited robust reversal of histamine-induced scratching bouts in mice.

Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency, Pharmacokinetics, and Metabolic Properties to Obtain Atropisomeric Quinolinone (AM-0466) that Affords Robust in Vivo Activity.

Because of its strong genetic validation, NaV1.7 has attracted significant interest as a target for the treatment of pain. We have previously reported on a number of structurally distinct bicyclic heteroarylsulfonamides as NaV1.7 inhibitors that demonstrate high levels of selectivity over other NaV isoforms. Herein, we report the discovery and optimization of a series of atropisomeric quinolinone sulfonamide inhibitors [ Bicyclic sulfonamide compounds as sodium channel inhibitors and their preparation . WO 2014201206, 2014 ] of NaV1.7, which demonstrate nanomolar inhibition of NaV1.7 and exhibit high levels of selectivity over other sodium channel isoforms. After optimization of metabolic and pharmacokinetic properties, including PXR activation, CYP2C9 inhibition, and CYP3A4 TDI, several compounds were advanced into in vivo target engagement and efficacy models. When tested in mice, compound 39 (AM-0466) demonstrated robust pharmacodynamic activity in a NaV1.7-dependent model of histamine-induced pruritus (itch) and additionally in a capsaicin-induced nociception model of pain without any confounding effect in open-field activity.

Correction to "Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency and Pharmacokinetics to Enable in Vivo Target Engagement".

[This corrects the article DOI: 10.1021/acsmedchemlett.6b00243.].

Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency and Pharmacokinetics to Enable in Vivo Target Engagement.

Human genetic evidence has identified the voltage-gated sodium channel NaV1.7 as an attractive target for the treatment of pain. We initially identified naphthalene sulfonamide 3 as a potent and selective inhibitor of NaV1.7. Optimization to reduce biliary clearance by balancing hydrophilicity and hydrophobicity (Log D) while maintaining NaV1.7 potency led to the identification of quinazoline 16 (AM-2099). Compound 16 demonstrated a favorable pharmacokinetic profile in rat and dog and demonstrated dose-dependent reduction of histamine-induced scratching bouts in a mouse behavioral model following oral dosing.

Structure- and property-based design of aminooxazoline xanthenes as selective, orally efficacious, and CNS penetrable BACE inhibitors for the treatment of Alzheimer's disease.

A structure- and property-based drug design approach was employed to identify aminooxazoline xanthenes as potent and selective human ß-secretase inhibitors. These compounds exhibited good isolated enzyme, cell potency, and selectivity against the structurally related aspartyl protease cathepsin D. Our efforts resulted in the identification of a potent, orally bioavailable CNS penetrant compound that exhibited in vivo efficacy. A single oral dose of compound 11a resulted in a significant reduction of CNS Aß40 in naive rats.

Discovery and optimization of potent and selective imidazopyridine and imidazopyridazine mTOR inhibitors.

mTOR is a critical regulator of cellular signaling downstream of multiple growth factors. The mTOR/PI3K/AKT pathway is frequently mutated in human cancers and is thus an important oncology target. Herein we report the evolution of our program to discover ATP-competitive mTOR inhibitors that demonstrate improved pharmacokinetic properties and selectivity compared to our previous leads. Through targeted SAR and structure-guided design, new imidazopyridine and imidazopyridazine scaffolds were identified that demonstrated superior inhibition of mTOR in cellular assays, selectivity over the closely related PIKK family and improved in vivo clearance over our previously reported benzimidazole series.

Design and preparation of a potent series of hydroxyethylamine containing ß-secretase inhibitors that demonstrate robust reduction of central ß-amyloid.

A series of potent hydroxyethyl amine (HEA) derived inhibitors of ß-site APP cleaving enzyme (BACE1) was optimized to address suboptimal pharmacokinetics and poor CNS partitioning. This work identified a series of benzodioxolane analogues that possessed improved metabolic stability and increased oral bioavailability. Subsequent efforts focused on improving CNS exposure by limiting susceptibility to Pgp-mediated efflux and identified an inhibitor which demonstrated robust and sustained reduction of CNS ß-amyloid (Aß) in Sprague-Dawley rats following oral administration.

Design and synthesis of potent, orally efficacious hydroxyethylamine derived ß-site amyloid precursor protein cleaving enzyme (BACE1) inhibitors.

We have previously shown that hydroxyethylamines can be potent inhibitors of the BACE1 enzyme and that the generation of BACE1 inhibitors with CYP 3A4 inhibitory activities in this scaffold affords compounds (e.g., 1) with sufficient bioavailability and pharmacokinetic profiles to reduce central amyloid-ß peptide (Aß) levels in wild-type rats following oral dosing. In this article, we describe further modifications of the P1-phenyl ring of the hydroxyethylamine series to afford potent, dual BACE1/CYP 3A4 inhibitors which demonstrate improved penetration into the CNS. Several of these compounds caused robust reduction of Aß levels in rat CSF and brain following oral dosing, and compound 37 exhibited an improved cardiovascular safety profile relative to 1.

Discovery of triazine-benzimidazoles as selective inhibitors of mTOR.

mTOR is part of the PI3K/AKT pathway and is a central regulator of cell growth and survival. Since many cancers display mutations linked to the mTOR signaling pathway, mTOR has emerged as an important target for oncology therapy. Herein, we report the discovery of triazine benzimidazole inhibitors that inhibit mTOR kinase activity with up to 200-fold selectivity over the structurally homologous kinase PI3Kα. When tested in a panel of cancer cell lines displaying various mutations, a selective inhibitor from this series inhibited cellular proliferation with a mean IC(50) of 0.41 µM. Lead compound 42 demonstrated up to 83% inhibition of mTOR substrate phosphorylation in a murine pharmacodynamic model.

Evaluation of a series of naphthamides as potent, orally active vascular endothelial growth factor receptor-2 tyrosine kinase inhibitors.

We have previously shown N-arylnaphthamides can be potent inhibitors of vascular endothelial growth factor receptors (VEGFRs). N-Alkyl and N-unsubstituted naphthamides were prepared and found to yield nanomolar inhibitors of VEGFR-2 (KDR) with an improved selectivity profile against a panel of tyrosine and serine/threonine kinases. The inhibitory activity of this series was retained at the cellular level. Naphthamides 3, 20, and 22 exhibited good pharmacokinetics following oral dosing and showed potent inhibition of VEGF-induced angiogenesis in the rat corneal model. Once-daily oral administration of 22 for 14 days led to 85% inhibition of established HT29 colon cancer and Calu-6 lung cancer xenografts at doses of 10 and 20 mg/kg, respectively.

Naphthamides as novel and potent vascular endothelial growth factor receptor tyrosine kinase inhibitors: design, synthesis, and evaluation.

A series of naphthyl-based compounds were synthesized as potential inhibitors of vascular endothelial growth factor (VEGF) receptors. Investigations of structure-activity relationships led to the identification of a series of naphthamides that are potent inhibitors of the VEGF receptor tyrosine kinase family. Numerous analogues demonstrated low nanomolar inhibition of VEGF-dependent human umbilical vein endothelial cell (HUVEC) proliferation, and of these several compounds possessed favorable pharmacokinetic (PK) profiles. In particular, compound 48 demonstrated significant antitumor efficacy against established HT29 human colon adenocarcinoma xenografts implanted in athymic mice. A full account of the preparation, structure-activity relationships, pharmacokinetic properties, and pharmacology of analogues within this series is presented.

Novel 2,3-dihydro-1,4-benzoxazines as potent and orally bioavailable inhibitors of tumor-driven angiogenesis.

Angiogenesis is vital for solid tumor growth, and its prevention is a proven strategy for the treatment of disease states such as cancer. The vascular endothelial growth factor (VEGF) pathway provides several opportunities by which small molecules can act as inhibitors of endothelial proliferation and migration. Critical to these processes is signaling through VEGFR-2 or the kinase insert domain receptor (KDR) upon stimulation by its ligand VEGF. Herein, we report the discovery of 2,3-dihydro-1,4-benzoxazines as inhibitors of intrinsic KDR activity (IC 50 < 0.1 microM) and human umbilical vein endothelial cell (HUVEC) proliferation with IC 50 < 0.1 microM. More specifically, compound 16 was identified as a potent (KDR: < 1 nM and HUVEC: 4 nM) and selective inhibitor that exhibited efficacy in angiogenic in vivo models. In addition, this series of molecules is typically well-absorbed orally, further demonstrating the 2,3-dihydro-1,4-benzoxazine moiety as a promising platform for generating kinase-based antiangiogenic therapeutic agents.