1521-0081/72/3/606–638$35.00 https://doi.org/10.1124/pr.120.019539 PHARMACOLOGICAL REVIEWS Pharmacol Rev 72:606–638, July 2020 Copyright © 2020 by The Author(s) This is an open access article distributed under the CC BY-NC Attribution 4.0 International license. ASSOCIATE EDITOR: ERIC L. BARKER Drug Resistance in Epilepsy: Clinical Impact, Potential Mechanisms, and New Innovative Treatment Options Wolfgang Löscher, Heidrun Potschka, Sanjay M. Sisodiya, and Annamaria Vezzani Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Hannover, Germany (W.L.); Center for Systems Neuroscience, Hannover, Germany (W.L.); Institute of Pharmacology, Toxicology and Pharmacy, Ludwig-Maximilians-University, Munich, Germany (H.P.); Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom (S.S); and Department of Neuroscience, Mario Negri Institute for Pharmacological Research Istituto di Ricovero e Cura a Carattere Scientifico, Milano, Italy (A.V.) Abstract. ....................................................................................607 Significance Statement ......................................................................607 I. Introduction. ..............................................................................607 II. Pharmacology of Antiseizure Drugs ..........................................................608 III. In Vivo and In Vitro Models of Drug Resistance..............................................610 A. General Aspects . ........................................................................610 Downloaded from B. Rodent and Zebrafish Models with Poor Responsiveness to Antiseizure Drugs.............610 C. Rodent Models with Selection of Responder and Nonresponder Subgroups . .............614 D. Dogs with Spontaneous Seizures . ......................................................615 E. In Vitro Models. ........................................................................615 IV. Current Hypotheses of Mechanisms of Drug Resistance . .....................................616 by guest on September 29, 2021 A. Alteration of Drug Targets in the Brain . ................................................618 B. Alteration of Drug Uptake into the Brain ................................................620 C. Alterations of Pharmacokinetics in the Periphery . .....................................623 D. Neural Network Hypothesis . ............................................................623 E. Intrinsic Severity Hypothesis ............................................................624 F. Gene Variant Hypothesis ................................................................624 G. The Epigenetic Hypothesis. ............................................................625 H. Neuroinflammation and Blood-Brain Barrier Dysfunction as Potential Mechanisms .......626 1. Pathophysiological Link between Neuroinflammation and Blood-Brain Barrier Dysfunction in Epilepsy . ............................................................626 2. Neuroinflammation and Blood-Brain Barrier Dysfunction: Role in Drug Resistance . 627 3. Cyclooxygenase 2–Prostaglandin E2–Prostaglandin E2 Receptor 1 Axis. .............627 4. Interleukin-1b–Interleukin-1–Receptor Type 1 Axis ...................................628 I. Other potential mechanisms of drug resistance. ....................................628 V. How to Overcome Drug Resistance?..........................................................628 A. Development of New Antiseizure Drugs by Using New Drug-Screening Paradigms . .......628 B. Precision Medicine ......................................................................630 Address correspondence to: Dr. Wolfgang Löscher, Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine, Bünteweg 17, D-30559 Hannover, Germany. E-mail: [email protected] W.L.’s work has been supported by the Deutsche Forschungsgemeinschaft and the European Union’s Seventh Framework Programme [FP7/2007-2013] under grant agreement n°602102 (EPITARGET) and n°201380 (EURIPIDES). S.S. is supported by the UK Epilepsy Society. This work was supported by European Community [Grant 279062], EpiPGX. This work was partly carried out at National Institute for Health Research (NIHR) University College London Hospitals Biomedical Research Centre, which receives a proportion of funding from the UK Department of Health’s NIHR Biomedical Research Centres funding scheme. H.P.’s work has been supported by the Deutsche Forschungsgemeinschaft, the European Union’s Seventh Framework Programme [Grant agreement n°201380 EURIPIDES], and European Union-Innovative Medicines Initiative (European Quality In Preclinical Data). A.V.’s work has been supported by the European Union’s Seventh Framework Programme [FP7/2007-2013] under grant agreement n°602102 (EPITARGET) by Fondazione AICE-FIRE and Fondazione Monzino. https://doi.org/10.1124/pr.120.019539. 606 Drug-Resistant Epilepsy 607 C. Development of More Effective Antiseizure Drugs by Revised Target-Based Drug Discovery. ..............................................................................631 D. Targeting of Transporter Function and Expression . .....................................632 E. Anti-Inflammatory Drugs and Strategies to Repair the BBB..............................633 1. Cyclooxygenase 2-Prostaglandin E2 Signaling.........................................633 2. Interleukin-1b–Interleukin-1–Receptor Type 1 Signaling ..............................633 3. Other Anti-Inflammatory Strategies . ................................................633 4. Molecular Mechanisms of Therapeutic Effects.........................................633 5. Strategies to Repair the BBB . ......................................................633 VI. Conclusions . ..............................................................................634 References ..................................................................................634 Abstract——Epilepsy is a chronic neurologic disor- understanding of the molecular, genetic, and structural der that affects over 70 million people worldwide. mechanisms of ASD resistance and discuss how Despite the availability of over 20 antiseizure drugs to overcome this problem. Encouragingly, better (ASDs) for symptomatic treatment of epileptic elucidation of the pathophysiological mechanisms seizures, about one-third ofpatientswithepilepsy underpinning epilepsies and drug resistance by have seizures refractory to pharmacotherapy. concerted preclinical and clinical efforts have recently Patients with such drug-resistant epilepsy (DRE) enabled a revised approach to the development of have increased risks of premature death, injuries, more promising therapies, including numerous psychosocial dysfunction, and a reduced quality of potential etiology-specific drugs (“precision medicine”) life, so development of more effective therapies is for severe pediatric (monogenetic) epilepsies and novel an urgent clinical need. However, the various types multitargeted ASDs for acquired partial epilepsies, of epilepsy and seizures and the complex temporal suggesting that the long hoped-for breakthrough in patterns of refractoriness complicate the issue. therapy for as-yet ASD-resistant patients is a feasible Furthermore, the underlying mechanisms of DRE goal. are not fully understood, though recent work has begun to shape our understanding more clearly. Significance Statement——Drug resistance provides Experimental models of DRE offer opportunities to a major challenge in epilepsy management. Here, we discover, characterize, and challenge putative mechanisms will review the current understanding of the molecular, of drug resistance. Furthermore, such preclinical models genetic, and structural mechanisms of drug resistance are important in developing therapies that may overcome in epilepsy and discuss how the problem might be drug resistance. Here, we will review the current overcome. I. Introduction from the onset of the epilepsy; 2) delayed resistance, which is when the patient initially becomes seizure-free Epilepsy is one of the most common and most disabling chronic neurologic disorders (Devinsky et al., but seizures recur and become uncontrollable; 3) a wax- 2018). People with epilepsy have recurrent unprovoked ing-and-waning (or fluctuating) pattern, which occurs (spontaneous) seizures, which can be focal or general- when the epilepsy alternates between being controlled ized in nature. Seizures cannot be fully controlled in and uncontrolled; or 4) the epilepsy is initially drug- about a third of people with epilepsy, even though resistant but with time responds to treatment (Schmidt multiple antiseizure drugs (ASDs) may have been and Löscher, 2005). Long-term outcome studies in employed singly or in various combinations; this phe- newly treated patients with epilepsy suggest that, after nomenon is drug resistance. In theory, at least four failure of two well-tolerated ASD schedules appropri- clinical patterns of drug resistance can be observed: 1) ately chosen for the seizure type(s), the chance of success de novo (or ab initio) ASD resistance, whereby the with further drug manipulation becomes progressively patient never enters a useful period of seizure freedom less likely (Chen et al., 2018). Thus, drug-resistant ABBREVIATIONS: ASD, antiseizure drug; ASP, Anticonvulsant Screening Program; BBB, blood-brain barrier; BCRP, breast cancer related protein; CA1, Cornu Ammonis sector 1; COX,