Authors :
Presenting Author: Cassandra Kinch, PhD – Stream Neuroscience Inc
Mitchell Kesler, MSc – Stream Neuroscience Inc
Deepika Dogra, PhD – Department of Medical Genetics, University of Calgary
Kyle Morin, BSc – Department of Medical Genetics, University of Calgary
Kingsley Ibhazehiebo, PhD – Department of Medical Genetics, University of Calgary
Jong Rho, MD – Department of Neurology, Yale School of Medicine
Deborah Kurrasch, PhD – Stream Neuroscience Inc
Rationale:
Despite the availability of nearly 40 approved anti-seizure medications (ASMs), one-third of individuals with epilepsy remain refractory and many experience debilitating cognitive or psychiatric side effects. We previously demonstrated that SN-2000, a selective allosteric phosphodiesterase 4B inhibitor (PDE4Bi), reduced spontaneous recurring seizures in the refractory Scn1a+/- mouse model.1 Here, we evaluate the broader preclinical efficacy of SN-2000 across multiple genetic and induced models of epilepsy and explore effects on cognition and behavior.
Methods:
Anti-seizure activity was assessed in epileptic larval zebrafish models, including scn1lab-/-, kcna1-/- and gabra1-/- mutants, as well pentylenetetrazol (PTZ)-induced. Standardized doses (50 mM) of SN-2000, standard-of-care ASMs (valproic acid [VPA], carbamazepine [CBZ], levetiracetam (LEV), lamotrigine [LTG], VPA + clobazam [CLO]) or vehicle were added to zebrafish media, and seizure-like locomotor activity was quantified using established automated behavioral tracking methods.2
Maximal Electroshock (MES) seizure stimulation was performed on C57BL6/129 (WT) mice following oral gavage of SN-2000 40, 60, or 80 mg/kg, VPA 250 mg/kg or vehicle. Recovery time and latency to attack was measured in protected MES-stimulated mice. Anxiety-like behavior was measured in WT mice exposed to SN-2000 40 mg/kg or vehicle placed in an open field with a novel object. Cognition was evaluated in WT and Scn1a+/- mice treated with SN-2000 40 mg/kg or vehicle in a Barnes Maze assay. Mice underwent a 5-day training period followed by a 24-hour probe trial to assess spatial memory retention.
Results:
SN-2000 significantly reduced seizure-like activity in all zebrafish models vs vehicle, with effects comparable to standard-of-care ASMs (Fig. 1a,b). In the MES model, SN-2000 provided dose-dependent seizure protection, with 40, 60, and 80 mg/kg doses conferring 50%, 75% and 75% protection, respectively, vs 0% in vehicle-treated mice and 92% protection in VPA 250 mg/kg exposed mice (Fig. 1c) . Although recovery times were similar across MES protected groups, VPA-treated mice were more prone to attack vs SN-2000 80 mg/kg treated mice (Fig. 2a,b). In the open field, SN-2000 vs vehicle-exposed WT mice spent significantly more time in the center, suggesting potential anxiolytic effects (Fig. 2c). In the Barnes maze, both WT and epileptic Scn1a+/- mice exposed to SN-2000 vs vehicle spent significantly more time near the target location, indicating potential pro-cognitive effects (Fig 2d).
Conclusions:
These findings support PDE4B inhibition as a disease-relevant mechanism in epilepsy and highlight SN-2000 as a promising broad-spectrum anti-seizure therapeutic candidate. SN-2000 demonstrates potential pro-cognitive and behavioral benefits beyond those of available ASMs.
1Kinch et al. AES 2024; 2.349
2Ibhazehiebo et al., Brain. 2018;141(3):744-761
Funding:
This work was supported by Cumming School of Medicine Research Fund (UCalgary) and private equity generated through Stream Neuroscience Inc.