Protocol Amendment 1 (dated 16-Sep-2015) was implemented after the date of first patient first visit (FPFV on 28-Aug-2015). Two subjects were randomized at the time of the amendment. The rationale for this amendment was to add an echocardiogram during dosing in response to a request from the Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte). This echocardiogram was added at Day OP22. In addition, the following changes were made: - It was clarified that either urine or serum pregnancy tests could be used for all visits. - It was pointed out that the decision to continue in the OLE study (EP0073) occurred at Day OP43. - Clarification on the procedure for dose reduction in cases of poor tolerability of UCB0942 400 mg bid (ie, reduction to UCB0942 200 mg bid and in some cases to UCB0942 100 mg bid). - The withdrawal criteria for elevated transaminases were reworded as the previous description was not clear.

Protocol Amendment 2 (dated 19-Nov-2015) was implemented after 22 subjects were randomized. The rationale for this amendment was to make the video monitoring language in the protocol more flexible so that sites/Investigators could perform this according to their usual practice. This new language also allowed video- electroencephalogram (EEG) monitoring as some sites did not perform video-only monitoring. A second change was the wording of the drug misuse exclusion criterion. As is customary in most UCB protocols, exclusion for drug misuse is only applicable if the Investigator deems that study participation is either a risk to the subject or that the drug misuse could confound the outcomes measured in the study. The wording of this exclusion criterion was changed to match that of other UCB studies.

Protocol Amendment 3 (dated-13 May-2016) was implemented after 35 subjects were randomized. The rationale for this amendment was to add and describe an optional interim analysis for purposes of planning and designing of future studies. Other reasons for the amendment included the following: - To add an exploratory objective, variable and associated assessment (Diary Addendum). Note that this was already part of the study, but not clearly described in the protocol. - To clarify procedures for dosing when there was intolerance to IMP during the Inpatient Period. - To allow and specify flexibility in dosing during the Outpatient Maintenance Period. - To further specify which subjects required an echocardiogram at 6 months after the last dose of UCB0942. - To expand the range of body mass index (BMI) allowed for inclusion in the study. - To revise procedures for assessment of suicidality using the Columbia-Suicide Severity Rating Scale (C-SSRS) (specifically, the C-SSRS withdrawal criterion) in line with revision to UCB SOP, which became effective on 01-Apr-2016. - To update the protocol information pertaining to potential drug-induced liver injury (PDILI) (exclusion criteria, withdrawal criteria, adverse events (AEs) of special interest, and assessments) based on new standard language which was being applied across all protocols at UCB. Note that these additions do not reflect a change in the known safety of the compound.

Protocol Amendment 4 (dated 10-Oct-2016) was implemented after all subjects were randomized. The rationale for this amendment was to describe a tiered approach to database lock and unblinding. Other changes included: - Correction of an inconsistency between the Summary section and the Study Design section pertaining to allowable dose changes - Clarification of the reporting period for AEs - Specification that the Baseline version of the Seizure Severity Questionnaire (SSQ) was to be used in all instances where it was administered - Correction of the number of questions in the SSQ from 11 to 10 - Correction of several cross references - Other minor administrative changes