Innovative models for in vitro detection of seizure

Abstract

Data show that toxicity to the central nervous system (CNS) is the most frequent cause of safety failures during the clinical phase of drug development. CNS endpoints such as seizure pose a safety risk to patients and volunteers and can lead to a loss of competitiveness, delays, and increased costs. Current methods rely on detection in the nonclinical rodent and non-rodent studies required to support clinical trials. There are two main issues with this approach; seizure may be missed in the animal studies and, even if seizure is detected, significant resource has already been invested in the project by this stage. Thus, there is a need to develop improved screening methods that can be used earlier in drug discovery to predict seizure. Advances in stem cell biology coupled with an increased understanding of the role of ion channels in seizure offer an opportunity for a new paradigm in screening. Human derived induced pluripotent stem cells (hiPSCs) representative of almost all cellular subtypes present in the brain can be incorporated into physiologically relevant in vitro models that can be used to determine seizure risk using high-throughput methods. Akin to the success of screening against a panel of ion channels such as hERG to reduce cardiovascular safety liability, the involvement of ion channels in seizure suggests that a similar approach to early seizure detection is valid. Profiling of the ion channels expressed in hiPSC models showing the seizurogenic phenotype coupled with electrophysiological assessment of ion channel function could translate into an ion channel seizure panel for rapid and reliable in vitro detection of seizure. The mechanistic information gathered would support optimal drug design early in development before resources, animals and time have been wasted.

Fig. 1. Development of an ion channel focussed approach to seizure detection. Ion channels in the brain have been associated with seizure (e.g. potassium channels, sodium channels, GABA-A and nicotinic acetylcholine receptors),, however the full complement of ion channels linked to seizure is yet to be resolved. Determination of the ion channel profile of various subtypes of hiPSC-derived neuronal cells followed by assessment of their impact on the seizurogenic phenotype would allow for creation of an in vitro ion channel panel for earlier seizure detection. Ion channels determined as possessing a seizure risk could be transfected into a routinely used cell line and this panel of cells expressing one specific ion channel per cell could be used to screen compounds for seizure risk.

Fig. 2. Potential to improve the current nonclinical screening paradigm for seizure. Characterisation of the ion channels expressed in human iPSC-derived neuronal cells that are linked to seizure and creation of an in vitro ion channel panel to screen for seizure could provide a mechanistic approach to nonclinical seizure detection. This approach would be a suitable addition to the existing nonclinical seizure-liability testing strategies that reduces the use of animal and ex vivo preparations.