Targeted degradation of MERTK and other TAM receptor paralogs by heterobifunctional targeted protein degraders.

TAM receptors (TYRO3, AXL, and MERTK) comprise a family of homologous receptor tyrosine kinases (RTK) that are expressed across a range of liquid and solid tumors where they contribute to both oncogenic signaling to promote tumor proliferation and survival, as well as expressed on myeloid and immune cells where they function to suppress host anti-tumor immunity. In recent years, several strategies have been employed to inhibit TAM kinases, most notably small molecule tyrosine kinase inhibitors and inhibitory neutralizing monoclonal antibodies (mAbs) that block receptor dimerization. Targeted protein degraders (TPD) use the ubiquitin proteasome pathway to redirect E3 ubiquitin ligase activity and target specific proteins for degradation. Here we employ first-in-class TPDs specific for MERTK/TAMs that consist of a cereblon E3 ligase binder linked to a tyrosine kinase inhibitor targeting MERTK and/or AXL and TYRO3. A series of MERTK TPDs were designed and investigated for their capacity to selectively degrade MERTK chimeric receptors, reduce surface expression on primary efferocytic bone marrow-derived macrophages, and impact on functional reduction in efferocytosis (clearance of apoptotic cells). We demonstrate proof-of-concept and establish that TPDs can be tailored to either selectivity degrades MERTK or concurrently degrade multiple TAMs and modulate receptor expression in vitro and in vivo. This work demonstrates the utility of proteome editing, enabled by tool degraders developed here towards dissecting the therapeutically relevant pathway biology in preclinical models, and the ability for TPDs to degrade transmembrane proteins. These data also provide proof of concept that TPDs may serve as a viable therapeutic strategy for targeting MERTK and other TAMs and that this technology could be expanded to other therapeutically relevant transmembrane proteins.

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.

Pharmacologic Characterization of AMG8379, a Potent and Selective Small Molecule Sulfonamide Antagonist of the Voltage-Gated Sodium Channel NaV1.7.

Potent and selective antagonists of the voltage-gated sodium channel NaV1.7 represent a promising avenue for the development of new chronic pain therapies. We generated a small molecule atropisomer quinolone sulfonamide antagonist AMG8379 and a less active enantiomer AMG8380. Here we show that AMG8379 potently blocks human NaV1.7 channels with an IC50 of 8.5 nM and endogenous tetrodotoxin (TTX)-sensitive sodium channels in dorsal root ganglion (DRG) neurons with an IC50 of 3.1 nM in whole-cell patch clamp electrophysiology assays using a voltage protocol that interrogates channels in a partially inactivated state. AMG8379 was 100- to 1000-fold selective over other NaV family members, including NaV1.4 expressed in muscle and NaV1.5 expressed in the heart, as well as TTX-resistant NaV channels in DRG neurons. Using an ex vivo mouse skin-nerve preparation, AMG8379 blocked mechanically induced action potential firing in C-fibers in both a time-dependent and dose-dependent manner. AMG8379 similarly reduced the frequency of thermally induced C-fiber spiking, whereas AMG8380 affected neither mechanical nor thermal responses. In vivo target engagement of AMG8379 in mice was evaluated in multiple NaV1.7-dependent behavioral endpoints. AMG8379 dose-dependently inhibited intradermal histamine-induced scratching and intraplantar capsaicin-induced licking, and reversed UVB radiation skin burn-induced thermal hyperalgesia; notably, behavioral effects were not observed with AMG8380 at similar plasma exposure levels. AMG8379 is a potent and selective NaV1.7 inhibitor that blocks sodium current in heterologous cells as well as DRG neurons, inhibits action potential firing in peripheral nerve fibers, and exhibits pharmacodynamic effects in translatable models of both itch and pain.

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, 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.

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 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.

Application of a Parallel Synthetic Strategy in the Discovery of Biaryl Acyl Sulfonamides as Efficient and Selective NaV1.7 Inhibitors.

The majority of potent and selective hNaV1.7 inhibitors possess common pharmacophoric features that include a heteroaryl sulfonamide headgroup and a lipophilic aromatic tail group. Recently, reports of similar aromatic tail groups in combination with an acyl sulfonamide headgroup have emerged, with the acyl sulfonamide bestowing levels of selectivity over hNaV1.5 comparable to the heteroaryl sulfonamide. Beginning with commercially available carboxylic acids that met selected pharmacophoric requirements in the lipophilic tail, a parallel synthetic approach was applied to rapidly generate the derived acyl sulfonamides. A biaryl acyl sulfonamide hit from this library was elaborated, optimizing for potency and selectivity with attention to physicochemical properties. The resulting novel leads are potent, ligand and lipophilic efficient, and selective over hNaV1.5. Representative lead 36 demonstrates selectivity over other human NaV isoforms and good pharmacokinetics in rodents. The biaryl acyl sulfonamides reported herein may also offer ADME advantages over known heteroaryl sulfonamide inhibitors.

An Orally Available BACE1 Inhibitor That Affords Robust CNS Aß Reduction without Cardiovascular Liabilities.

BACE1 inhibition to prevent Aß peptide formation is considered to be a potential route to a disease-modifying treatment for Alzheimer's disease. Previous efforts in our laboratory using a combined structure- and property-based approach have resulted in the identification of aminooxazoline xanthenes as potent BACE1 inhibitors. Herein, we report further optimization leading to the discovery of inhibitor 15 as an orally available and highly efficacious BACE1 inhibitor that robustly reduces CSF and brain Aß levels in both rats and nonhuman primates. In addition, compound 15 exhibited low activity on the hERG ion channel and was well tolerated in an integrated cardiovascular safety model.

Development of 2-aminooxazoline 3-azaxanthenes as orally efficacious ß-secretase inhibitors for the potential treatment of Alzheimer's disease.

The ß-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is one of the most hotly pursued targets for the treatment of Alzheimer's disease. We used a structure- and property-based drug design approach to identify 2-aminooxazoline 3-azaxanthenes as potent BACE1 inhibitors which significantly reduced CSF and brain Aß levels in a rat pharmacodynamic model. Compared to the initial lead 2, compound 28 exhibited reduced potential for QTc prolongation in a non-human primate cardiovascular safety model.

Lead optimization and modulation of hERG activity in a series of aminooxazoline xanthene ß-site amyloid precursor protein cleaving enzyme (BACE1) inhibitors.

The optimization of a series of aminooxazoline xanthene inhibitors of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) is described. An early lead compound showed robust Aß lowering activity in a rat pharmacodynamic model, but advancement was precluded by a low therapeutic window to QTc prolongation in cardiovascular models consistent with in vitro activity on the hERG ion channel. While the introduction of polar groups was effective in reducing hERG binding affinity, this came at the expense of higher than desired Pgp-mediated efflux. A balance of low Pgp efflux and hERG activity was achieved by lowering the polar surface area of the P3 substituent while retaining polarity in the P2' side chain. The introduction of a fluorine in position 4 of the xanthene ring improved BACE1 potency (5-10-fold). The combination of these optimized fragments resulted in identification of compound 40, which showed robust Aß reduction in a rat pharmacodynamic model (78% Aß reduction in CSF at 10 mg/kg po) and also showed acceptable cardiovascular safety in vivo.

Inhibitors of ß-site amyloid precursor protein cleaving enzyme (BACE1): identification of (S)-7-(2-fluoropyridin-3-yl)-3-((3-methyloxetan-3-yl)ethynyl)-5'H-spiro[chromeno[2,3-b]pyridine-5,4'-oxazol]-2'-amine (AMG-8718).

We have previously shown that the aminooxazoline xanthene scaffold can generate potent and orally efficacious BACE1 inhibitors although certain of these compounds exhibited potential hERG liabilities. In this article, we describe 4-aza substitution on the xanthene core as a means to increase BACE1 potency while reducing hERG binding affinity. Further optimization of the P3 and P2' side chains resulted in the identification of 42 (AMG-8718), a compound with a balanced profile of BACE1 potency, hERG binding affinity, and Pgp recognition. This compound produced robust and sustained reductions of CSF and brain Aß levels in a rat pharmacodynamic model and exhibited significantly reduced potential for QTc elongation in a cardiovascular safety model.

De novo prediction of p-glycoprotein-mediated efflux liability for druglike compounds.

P-glycoprotein (Pgp) is capable of recognizing and transporting a wide range of chemically diverse compounds in vivo. Overcoming Pgp-mediated efflux can represent a significant challenge when penetration into the central nervous system is required or within the context of developing anticancer therapies. While numerous in silico models have been developed to predict Pgp-mediated efflux, these models rely on training sets and are best suited to make interpolations. Therefore, it is desirable to develop ab initio models that can be used to predict efflux liabilities. Herein, we present a de novo method that can be used to predict Pgp-mediated efflux potential for druglike compounds. A model, which correlates the computed solvation free energy differences obtained in water and chloroform with Pgp-mediated efflux (in logarithmic scale), was successful in predicting Pgp efflux ratios for a wide range of chemically diverse compounds with a R(2) and root-mean-square error of 0.65 and 0.29, respectively.

Establishing the relationship between in vitro potency, pharmacokinetic, and pharmacodynamic parameters in a series of orally available, hydroxyethylamine-derived ß-secretase inhibitors.

Sequential proteolytic cleavage of the amyloid precursor protein (APP) by ß-site APP-cleaving enzyme 1 (BACE1) and the γ-secretase complex produces the amyloid-ß peptide (Aß), which is believed to play a critical role in the pathology of Alzheimer's disease (AD). The aspartyl protease BACE1 catalyzes the rate-limiting step in the production of Aß, and as such it is considered to be an important target for drug development in AD. The development of a BACE1 inhibitor therapeutic has proven to be difficult. The active site of BACE1 is relatively large. Consequently, to achieve sufficient potency, many BACE1 inhibitors have required unfavorable physicochemical properties such as high molecular weight and polar surface area that are detrimental to efficient passage across the blood-brain barrier. Using a rational drug design approach we have designed and developed a new series of hydroxyethylamine-based inhibitors of BACE1 capable of lowering Aß levels in the brains of rats after oral administration. Herein we describe the in vitro and in vivo characterization of two of these molecules and the overall relationship of compound properties [e.g., in vitro permeability, P-glycoprotein (P-gp) efflux, metabolic stability, and pharmacological potency] to the in vivo pharmacodynamic effect with more than 100 compounds across the chemical series. We demonstrate that high in vitro potency for BACE1 was not sufficient to provide central efficacy. A combination of potency, high permeability, low P-gp-mediated efflux, and low clearance was required for compounds to produce robust central Aß reduction after oral dosing.

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.

A Potent and Orally Efficacious, Hydroxyethylamine-Based Inhibitor of ß-Secretase.

ß-Secretase inhibitors are potentially disease-modifying treatments for Alzheimer's disease. Previous efforts in our laboratory have resulted in hydroxyethylamine-derived inhibitors such as 1 with low nanomolar potency against ß-site amyloid precursor protein cleaving enzyme (BACE). When dosed intravenously, compound 1 was also shown to significantly reduce Aß40 levels in plasma, brain, and cerebral spinal fluid. Herein, we report further optimizations that led to the discovery of inhibitor 16 as a novel, potent, and orally efficacious BACE inhibitor.

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.