Effects of retigabine and the novel M-current activator BVH-7000 on epilepsy-associated KCNQ2 variants
Abstract number :
1.444
Submission category :
1. Basic Mechanisms / 1D. Mechanisms of Therapeutic Interventions
Year :
2022
Submission ID :
2233004
Source :
www.aesnet.org
Presentation date :
12/3/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:29 AM
Authors :
Carlos Vanoye, PhD – Northwestern University, Feinberg School of Medicine; Reshma Desai, MS – Senior Researcher, Pharmacology, Northwestern University, Feinberg School of Medicine; Nora Ghabra, BS – Pharmacology – Northwestern University, Feinberg School of Medicine; Kelly Picchione, PhD – Principal Investigator Biology, Biohaven Labs; Steven Dworetzky, PhD – Senior Vice President, Biohaven Labs; Alfred George, Jr., MD – Professor and Chair, Pharmacology, Northwestern University, Feinberg School of Medicine
This is a Late Breaking abstract
Rationale: The voltage-gated potassium channels KCNQ2 (KV7.2; Q2) and KCNQ3 (KV7.3; Q3), encoded by KCNQ2 and KCNQ3, respectively, co-assemble to form a channel complex (Q2/Q3) responsible for generating the M-current that regulates neuronal excitability. KCNQ2 pathogenic variants identified in children with developmental and epileptic encephalopathy (DEE) most often exhibit loss-of-function with dominant-negative effects. Pharmacological potentiation of M-current with retigabine (RET) or newer investigational agents such as BVH-7000 (BHV; formally KB-3061) is a potential therapy for this condition. Here, we compared the effects of RET with BHV on wild-type (WT) Q2/Q3 and channels comprised of DEE-associated KCNQ2 variants.
Methods: We expressed Q2/Q3 channels in Chinese hamster ovary (CHO) cells and recorded whole-cell currents using automated planar patch clamp first in the absence then presence of vehicle (DMSO) or M-current activator (RET or BVH). Experiments were conducted using cells transfected with an equal mixture of WT and variant KCNQ2 along with WT KCNQ3 to generate heteromultimeric channel complexes that recapitulated the heterozygous state. Specific channel activity was determined by applying the M-current blocker XE-991 (10 µM) at the end of experiments, and only XE-991-sensitive currents were analyzed.
Results: At 3 µM, both compounds induced significant hyperpolarizing shifts in the voltage-dependence of activation (delta V½) of WT channels, but the effect was greater for BHV (RET = -18.7±1.7, n=13; BHV = -32.1±1.4, n=8). Both compounds boosted current amplitude to a similar degree (relative to the no drug condition: RET = 7.0±0.9 fold increase; BHV = 6.2±0.9 fold increase) when measured during -10 mV test pulses. The half-maximal effective concentration (EC50) for delta V½ of WT channels were RET = 4.9 μM; BHV = 1.4 μM. We also assessed the effects of RET and BHV on channels incorporating KCNQ2 variants for which clinical responses to retigabine treatment were reported. BVH (3 µM) induced greater hyperpolarizing shifts in activation V½ than RET (3 µM).
Conclusions: The M-current activators RET and BHV exhibited effects on WT Q2/Q3 channels and restored current for channels containing DEE-associated pathogenic KCNQ2 variants. We are testing several additional variants and determining concentration-response relationships for a more complete understanding of these effects. Delineating the heterogeneity of M-current activator responsiveness of pathogenic variants may enable better deployment of precision pharmacotherapies for KCNQ2-DEE.
Funding: NIH U54-NS108874
Basic Mechanisms