Molecular Pharmacology of Selective Na_V1.6 and Dual Na_V1.6/Na_V1.2 Channel Inhibitors that Suppress Excitatory Neuronal Activity Ex Vivo

Voltage-gated sodium channel (NaV) inhibitors are used to treat neurological disorders of hyperexcitability such as epilepsy. These drugs act by attenuating neuronal action potential firing to reduce excitability in the brain. However, all currently available NaV-targeting antiseizure medications nonselectively inhibit the brain channels NaV1.1, NaV1.2, and NaV1.6, which potentially limits the efficacy and therapeutic safety margins of these drugs. Here, we report on XPC-7724 and XPC-5462, which represent a new class of small molecule NaV-targeting compounds. These compounds specifically target inhibition of the NaV1.6 and NaV1.2 channels, which are abundantly expressed in excitatory pyramidal neurons. They have a > 100-fold molecular selectivity against NaV1.1 channels, which are predominantly expressed in inhibitory neurons. Sparing NaV1.1 preserves the inhibitory activity in the brain. These compounds bind to and stabilize the inactivated state of the channels thereby reducing the activity of excitatory neurons. They have higher potency, with longer residency times and slower off-rates, than the clinically used antiseizure medications carbamazepine and phenytoin. The neuronal selectivity of these compounds is demonstrated in brain slices by inhibition of firing in cortical excitatory pyramidal neurons, without impacting fast spiking inhibitory interneurons. XPC-5462 also suppresses epileptiform activity in an ex vivo brain slice seizure model, whereas XPC-7224 does not, suggesting a possible requirement of Nav1.2 inhibition in 0-Mg2+- or 4-AP-induced brain slice seizure models. The profiles of these compounds will facilitate pharmacological dissection of the physiological roles of NaV1.2 and NaV1.6 in neurons and help define the role of specific channels in disease states. This unique selectivity profile provides a new approach to potentially treat disorders of neuronal hyperexcitability by selectively downregulating excitatory circuits

Discovery of Aryl Sulfonamides as Isoform-Selective Inhibitors of Na_V1.7 with Efficacy in Rodent Pain Models

We report on a novel series of aryl sulfonamides that act as nanomolar potent, isoform-selective inhibitors of the human sodium channel hNa_V1.7. The optimization of these inhibitors is described. We aimed to improve potency against hNa_V1.7 while minimizing off-target safety concerns and generated compound <b>3</b>. This agent displayed significant analgesic effects in rodent models of acute and inflammatory pain and demonstrated that binding to the voltage sensor domain 4 site of Na_V1.7 leads to an analgesic effect <i>in vivo</i>. Our findings corroborate the importance of hNa_V1.7 as a drug target for the treatment of pain

Design of Conformationally Constrained Acyl Sulfonamide Isosteres: Identification of <i>N</i>‑([1,2,4]Triazolo[4,3‑<i>a</i>]pyridin-3-yl)methane-sulfonamides as Potent and Selective <i>h</i>Na_V1.7 Inhibitors for the Treatment of Pain

The sodium channel Na_V1.7 has emerged as a promising target for the treatment of pain based on strong genetic validation of its role in nociception. In recent years, a number of aryl and acyl sulfonamides have been reported as potent inhibitors of Na_V1.7, with high selectivity over the cardiac isoform Na_V1.5. Herein, we report on the discovery of a novel series of <i>N</i>-([1,2,4]­triazolo­[4,3-<i>a</i>]­pyridin-3-yl)­methanesulfonamides as selective Na_V1.7 inhibitors. Starting with the crystal structure of an acyl sulfonamide, we rationalized that cyclization to form a fused heterocycle would improve physicochemical properties, in particular lipophilicity. Our design strategy focused on optimization of potency for block of Na_V1.7 and human metabolic stability. Lead compounds <b>10</b>, <b>13</b> (GNE-131), and <b>25</b> showed excellent potency, good <i>in vitro</i> metabolic stability, and low <i>in vivo</i> clearance in mouse, rat, and dog. Compound <b>13</b> also displayed excellent efficacy in a transgenic mouse model of induced pain

Design of Conformationally Constrained Acyl Sulfonamide Isosteres: Identification of <i>N</i>‑([1,2,4]Triazolo[4,3‑<i>a</i>]pyridin-3-yl)methane-sulfonamides as Potent and Selective <i>h</i>Na_V1.7 Inhibitors for the Treatment of Pain

The sodium channel Na_V1.7 has emerged as a promising target for the treatment of pain based on strong genetic validation of its role in nociception. In recent years, a number of aryl and acyl sulfonamides have been reported as potent inhibitors of Na_V1.7, with high selectivity over the cardiac isoform Na_V1.5. Herein, we report on the discovery of a novel series of <i>N</i>-([1,2,4]­triazolo­[4,3-<i>a</i>]­pyridin-3-yl)­methanesulfonamides as selective Na_V1.7 inhibitors. Starting with the crystal structure of an acyl sulfonamide, we rationalized that cyclization to form a fused heterocycle would improve physicochemical properties, in particular lipophilicity. Our design strategy focused on optimization of potency for block of Na_V1.7 and human metabolic stability. Lead compounds <b>10</b>, <b>13</b> (GNE-131), and <b>25</b> showed excellent potency, good <i>in vitro</i> metabolic stability, and low <i>in vivo</i> clearance in mouse, rat, and dog. Compound <b>13</b> also displayed excellent efficacy in a transgenic mouse model of induced pain

Design of Conformationally Constrained Acyl Sulfonamide Isosteres: Identification of <i>N</i>‑([1,2,4]Triazolo[4,3‑<i>a</i>]pyridin-3-yl)methane-sulfonamides as Potent and Selective <i>h</i>Na_V1.7 Inhibitors for the Treatment of Pain

The sodium channel Na_V1.7 has emerged as a promising target for the treatment of pain based on strong genetic validation of its role in nociception. In recent years, a number of aryl and acyl sulfonamides have been reported as potent inhibitors of Na_V1.7, with high selectivity over the cardiac isoform Na_V1.5. Herein, we report on the discovery of a novel series of <i>N</i>-([1,2,4]­triazolo­[4,3-<i>a</i>]­pyridin-3-yl)­methanesulfonamides as selective Na_V1.7 inhibitors. Starting with the crystal structure of an acyl sulfonamide, we rationalized that cyclization to form a fused heterocycle would improve physicochemical properties, in particular lipophilicity. Our design strategy focused on optimization of potency for block of Na_V1.7 and human metabolic stability. Lead compounds <b>10</b>, <b>13</b> (GNE-131), and <b>25</b> showed excellent potency, good <i>in vitro</i> metabolic stability, and low <i>in vivo</i> clearance in mouse, rat, and dog. Compound <b>13</b> also displayed excellent efficacy in a transgenic mouse model of induced pain