Discovery of a Class of Novel Tankyrase Inhibitors that Bind to Both the Nicotinamide Pocket and the Induced Pocket

Potent and selective inhibitors of tankyrases have recently been characterized to bind to an induced pocket. Here we report the identification of a novel potent and selective tankyrase inhibitor that binds to both the nicotinamide pocket and the induced pocket. The crystal structure of human TNKS1 in complex with this “dual-binder” provides a molecular basis for their strong and specific interactions and suggests clues for the further development of tankyrase inhibitors

Inhibition of Inactive States of Tetrodotoxin-Sensitive Sodium Channels Reduces Spontaneous Firing of C-Fiber Nociceptors and Produces Analgesia in Formalin and Complete Freund's Adjuvant Models of Pain.

While genetic evidence shows that the Nav1.7 voltage-gated sodium ion channel is a key regulator of pain, it is unclear exactly how Nav1.7 governs neuronal firing and what biophysical, physiological, and distribution properties of a pharmacological Nav1.7 inhibitor are required to produce analgesia. Here we characterize a series of aminotriazine inhibitors of Nav1.7 in vitro and in rodent models of pain and test the effects of the previously reported "compound 52" aminotriazine inhibitor on the spiking properties of nociceptors in vivo. Multiple aminotriazines, including some with low terminal brain to plasma concentration ratios, showed analgesic efficacy in the formalin model of pain. Effective concentrations were consistent with the in vitro potency as measured on partially-inactivated Nav1.7 but were far below concentrations required to inhibit non-inactivated Nav1.7. Compound 52 also reversed thermal hyperalgesia in the complete Freund's adjuvant (CFA) model of pain. To study neuronal mechanisms, electrophysiological recordings were made in vivo from single nociceptive fibers from the rat tibial nerve one day after CFA injection. Compound 52 reduced the spontaneous firing of C-fiber nociceptors from approximately 0.7 Hz to 0.2 Hz and decreased the number of action potentials evoked by suprathreshold tactile and heat stimuli. It did not, however, appreciably alter the C-fiber thresholds for response to tactile or thermal stimuli. Surprisingly, compound 52 did not affect spontaneous activity or evoked responses of Aδ-fiber nociceptors. Results suggest that inhibition of inactivated states of TTX-S channels, mostly likely Nav1.7, in the peripheral nervous system produces analgesia by regulating the spontaneous discharge of C-fiber nociceptors

Structure-Based Design of 2‑Aminopyridine Oxazolidinones as Potent and Selective Tankyrase Inhibitors

Aberrant activation of the Wnt pathway has been implicated in the development and formation of many cancers. TNKS inhibition has been shown to antagonize Wnt signaling via Axin stabilization in APC mutant colon cancer cell lines. We employed structure-based design to identify a series of 2-aminopyridine oxazolidinones as potent and selective TNKS inhibitors. These compounds exhibited good enzyme and cell potency as well as selectivity over other PARP isoforms. Co-crystal structures of these 2-aminopyridine oxazolidinones complexed to TNKS reveal an induced-pocket binding mode that does not involve interactions with the nicotinamide binding pocket. Oral dosing of lead compounds <b>3</b> and <b>4</b> resulted in significant effects on several Wnt-pathway biomarkers in a three day DLD-1 mouse tumor PD model

<i>In vitro</i> and <i>in vivo</i> properties of aminotriazines used in this study.

<p>Shown for each compound are IC50 on non-inactivated human Nav1.7, IC50 on 20%-inactivated human Nav1.7, and IC50 on 20%-inactivated rat Nav1.7, all taken with patch-clamp electrophysiology; <i>in vitro</i> plasma protein binding; the ratio of brain to plasma concentrations <i>in vivo</i>; whether the compound produced analgesic efficacy in the rat formalin model of pain; and the plasma concentration corresponding to the lowest dose that produced efficacy. IC50s on hNav1.7 were measured with manual patch-clamp electrophysiology; IC50s on rNav1.7 were measured with the PatchXpress® automated electrophysiology platform. Brain to plasma ratios were calculated from concentrations experimentally measured following the formalin test. ND = no data. Analgesic efficacy was determined by a statistically significant (p < 0.05) decrease in formalin-induced flinching for which the same dose did not produce a reduction in movement in the open field assay that obviated the formalin result. Effective [plasma] is the mean (n = 8, except n = 7 for compound E) terminal plasma concentration produced by the lowest effective dose of each compound.</p><p><i>In vitro</i> and <i>in vivo</i> properties of aminotriazines used in this study.</p

Compound 52 reduced the ongoing spontaneous activity of C-fiber nociceptors but not Aδ-fiber nociceptors.

<p>Intravenous injection of compound 52 decreased ongoing spontaneous activity of C-fiber nociceptors sensitized by intraplantar administration of CFA (upper panel). The level of ongoing spontaneous activity of sensitized C-fiber nociceptors was significantly lower following administration of compound 52 than following administration of vehicle, from 12 minutes post-administration on. The attenuation of ongoing spontaneous activity by compound 52 continued until the end of the monitoring period (26 minutes after administration of drug). In contrast, administration of compound 52 did not decrease the level of ongoing spontaneous activity in Aδ-fiber nociceptors when compared to vehicle (lower panel). *p < 0.05; **p < 0.01.</p