Publications by authors named "Christopher P Ilch"

5 Publications

  • Page 1 of 1

Engineering Na1.7 Inhibitory JzTx-V Peptides with a Potency and Basicity Profile Suitable for Antibody Conjugation To Enhance Pharmacokinetics.

ACS Chem Biol 2019 04 27;14(4):806-818. Epub 2019 Mar 27.

Drug discovery research on new pain targets with human genetic validation, including the voltage-gated sodium channel Na1.7, is being pursued to address the unmet medical need with respect to chronic pain and the rising opioid epidemic. As part of early research efforts on this front, we have previously developed Na1.7 inhibitory peptide-antibody conjugates with tarantula venom-derived GpTx-1 toxin peptides with an extended half-life (80 h) in rodents but only moderate in vitro activity (hNa1.7 IC = 250 nM) and without in vivo activity. We identified the more potent peptide JzTx-V from our natural peptide collection and improved its selectivity against other sodium channel isoforms through positional analogueing. Here we report utilization of the JzTx-V scaffold in a peptide-antibody conjugate and architectural variations in the linker, peptide loading, and antibody attachment site. We found conjugates with 100-fold improved in vitro potency relative to those of complementary GpTx-1 analogues, but pharmacokinetic and bioimaging analyses of these JzTx-V conjugates revealed a shorter than expected plasma half-life in vivo with accumulation in the liver. In an attempt to increase circulatory serum levels, we sought the reduction of the net +6 charge of the JzTx-V scaffold while retaining a desirable Na in vitro activity profile. The conjugate of a JzTx-V peptide analogue with a +2 formal charge maintained Na1.7 potency with 18-fold improved plasma exposure in rodents. Balancing the loss of peptide and conjugate potency associated with the reduction of net charge necessary for improved target exposure resulted in a compound with moderate activity in a Na1.7-dependent pharmacodynamic model but requires further optimization to identify a conjugate that can fully engage Na1.7 in vivo.
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http://dx.doi.org/10.1021/acschembio.9b00183DOI Listing
April 2019

Discovery of Tarantula Venom-Derived Na1.7-Inhibitory JzTx-V Peptide 5-Br-Trp24 Analogue AM-6120 with Systemic Block of Histamine-Induced Pruritis.

J Med Chem 2018 11 22;61(21):9500-9512. Epub 2018 Oct 22.

Therapeutic Discovery, Amgen Research , Amgen Inc. , 1120 Veterans Blvd , South San Francisco , California 94080 , United States.

Inhibitors of the voltage-gated sodium channel Na1.7 are being investigated as pain therapeutics due to compelling human genetics. We previously identified Na1.7-inhibitory peptides GpTx-1 and JzTx-V from tarantula venom screens. Potency and selectivity were modulated through attribute-based positional scans of native residues via chemical synthesis. Herein, we report JzTx-V lead optimization to identify a pharmacodynamically active peptide variant. Molecular docking of peptide ensembles from NMR into a homology model-derived Na1.7 structure supported prioritization of key residues clustered on a hydrophobic face of the disulfide-rich folded peptide for derivatization. Replacing Trp24 with 5-Br-Trp24 identified lead peptides with activity in electrophysiology assays in engineered and neuronal cells. 5-Br-Trp24 containing peptide AM-6120 was characterized in X-ray crystallography and pharmacokinetic studies and blocked histamine-induced pruritis in mice after subcutaneous administration, demonstrating systemic Na1.7-dependent pharmacodynamics. Our data suggests a need for high target coverage based on plasma exposure for impacting in vivo end points with selectivity-optimized peptidic Na1.7 inhibitors.
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http://dx.doi.org/10.1021/acs.jmedchem.8b00736DOI Listing
November 2018

Pharmacologic Characterization of AMG8379, a Potent and Selective Small Molecule Sulfonamide Antagonist of the Voltage-Gated Sodium Channel Na1.7.

J Pharmacol Exp Ther 2017 07 4;362(1):146-160. Epub 2017 May 4.

Department of Neuroscience (T.J.K., R.Y., S.A, C.P.I., M.J., D.J., J.H.L., S.G.L., J.Li., D.L., J.Lu., D.M., D.O., K.T., J.W., V.Y., D.X.D.Z., R.T.F., B.D.M.), Department of Medicinal Chemistry (M.M.W.), and Department of Pharmacokinetics and Drug Metabolism (X.B., V.B., J.R.), Amgen Inc., Cambridge, Massachusetts and Thousand Oaks, California

Potent and selective antagonists of the voltage-gated sodium channel Na1.7 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 Na1.7 channels with an IC of 8.5 nM and endogenous tetrodotoxin (TTX)-sensitive sodium channels in dorsal root ganglion (DRG) neurons with an IC 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 Na family members, including Na1.4 expressed in muscle and Na1.5 expressed in the heart, as well as TTX-resistant Na 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 Na1.7-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 Na1.7 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.
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http://dx.doi.org/10.1124/jpet.116.239590DOI Listing
July 2017

Cerebrovasodilation evoked by stimulation of subthalamic vasodilator area and hypoxia depends upon the integrity of cortical neurons in the rat.

Neurosci Lett 2004 Sep;368(1):92-5

Memory Pharmaceuticals Corp., 100 Philips Parkway, Montvale, NJ 07645, USA.

In Sprague-Dawley rats symmetrical sites of the parietal cortex were microinjected with ibotenic acid (IBO, 10microg in 1microl) to lesion local neurons or with saline (1microl). Five days later, changes of cortical cerebral blood flow (CBF) in response to hypoxia and stimulation of the subthalamic vasodilator area (SVA) were measured using laser-Doppler flowmetry (LDF). The baseline CBF over the IBO- and saline-injected cortical sites did not differ significantly, but spontaneous waves of CBF were abolished over the lesioned sites. Elevations of CBF evoked by hypoxia or stimulation of SVA were attenuated by 54% and 88%, respectively (P < 0.05) over the lesioned sites, compared to saline-injected or non-injected sites. Hypercarbic cerebrovasodilation was comparable over all sites. We conclude that the SVA-evoked increase of CBF and about 50% of the hypoxia-evoked increase of CBF are mediated by excitation of cortical neurons.
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http://dx.doi.org/10.1016/j.neulet.2004.06.063DOI Listing
September 2004

Electrical stimulation of the dorsal periaqueductal gray decreases volume of the brain infarction independently of accompanying hypertension and cerebrovasodilation.

Brain Res 2003 Dec;994(2):135-45

Departments of Psychiatry and Neuroscience, Columbia University and New York State Psychiatric Institute, 1051 Riverside Dr, Box #42, New York, NY 10032, USA.

We investigated whether selective stimulation of neurons of the sympathoinhibitory ventral periaqueductal gray (VPAG), or sympathoexcitatory dorsal periaqueductal gray (DPAG), differentially modulates CBF and EEG and exerts neuroprotection. Electrical stimulation of either regions of PAG comparably elevated AP and CBF, whereas chemical stimulation with the D,L-homocysteine produced either sympathoinhibition accompanied by decrease in CBF from ventral region or sympathoexcitation accompanied by increase in CBF from dorsal region in nonspinalized rats. The CBF effects evoked from DPAG and VPAG by chemical stimulation were preserved in spinalized rats supporting that the evoked CBF responses result directly from stimulation and are not secondary to AP changes. Stimulation of either region, whether chemical or electrical, synchronized the EEG. To explore whether PAG stimulation might protect the brain against ischemic injury, in other rats the VPAG or DPAG were stimulated for 1 h (50 Hz, 1 s on/1 s off, 75-100 microA) and the middle cerebral artery occluded 72 h later. Stimulation of the DPAG, but not VPAG, significantly reduced infarction volumes relative to sham-stimulated controls as determined 24 h after occlusion. Elevations of AP and CBF did not differ between groups. We conclude: (a). intrinsic neurons of D- and VPAG differentially regulate CBF; (b). neurons of DPAG are neuroprotective independently of changes in CBF and/or AP. The DPAG effect on infarct volume may be related to the central neuroprotective pathway evoked by stimulation of the cerebellar FN.
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http://dx.doi.org/10.1016/j.brainres.2003.08.001DOI Listing
December 2003