A double-blind, randomized, placebo-controlled trial of adjunctive ganaxolone treatment in female children with protocadherin 19 (PCDH19)-related epilepsy followed by long-term open-label treatment

Protocadherin19 (PCDH19)-related epilepsy is a serious epileptic condition
characterized by early-onset cluster seizures, cognitive and sensory impairment
of varying degrees, and psychiatric and behavioral disturbances affecting
primarily females (Camacho 2012). The condition is caused by an inherited
mutation of the PCDH19 gene located on the X chromosome. This gene encodes for
a calcium-dependent cell-cell adhesion molecule that is expressed in the
central nervous system (CNS; eg, hippocampus, cerebral cortex, thalamus,
amygdala) and which appears to be related to synaptic transmission and
formation of synaptic connections during brain development (Depienne 2009).
The mean age of seizure onset in this condition is approximately 10 months
(range of 3-38 months) (Scheffer 2008, Specchio 2011, Dipienne 2011,
Cappelletti 2015, van Harssel 2013). The mean age of offset of epileptic
seizures is approximately 12.5 years (1-35 years). PCDH19-related epilepsy has
been described as a *semiprogressive* condition, meaning that seizure frequency
increases during the first few years of life (Specchio 2011). However, over
time the seizure frequency lessens, and seizures become less frequent with
increased age.
There is also evidence supporting an allopregnanolone deficiency as a proposed
contributor to the onset of seizures in individuals with PCDH19-related
epilepsy (Tan 2015). It was found that individuals with this genetic mutation
demonstrated a downregulation of steroid hormone-metabolizing enzymes resulting
in reduced allopregnanolone levels compared to non-affected, age-match
controls. Since these neurosteroids are known to have strong anti-convulsant
properties, it is hypothesized that treatment with neurosteroids with similar
action, or analogs such as GNX, may have therapeutic benefit to seizure control.
Ganaxolone is the 3β-methylated synthetic analog of allopregnanolone, an
endogenous allosteric modulator of CNS γ-Aminobutyric acid type A (GABAA)
receptors. Ganaxolone has potency and efficacy comparable to allopregnanolone
(Carter 1997) in activating synaptic and extrasynaptic GABAA receptors at a
site distinct from benzodiazepines and barbiturates. Ganaxolone has protective
activity in diverse rodent seizure models (Reddy 2012, Bialer 2010). Clinical
studies have demonstrated that GNX has anticonvulsant activity with an
acceptable safety and tolerability profile in the dose range of 900 to 1800 mg
in adults and children (Sperling 2017, Laxer 2000, Kerrigan 2000, Pieribone
2007). Further, GNX reduces seizures in children with IS and refractory
pediatric epilepsy. In an OL study, pediatric subjects aged 2 to 60 months
with refractory seizures and a history of IS were treated with GNX doses up to
36 mg/kg for up to 3 months (Kerrigan 2000). Sixteen of the 20 subjects
completed treatment, 15 of whom had a history of IS. Five of the 15 subjects
had a decrease from baseline in the number of spasms of >= 50%, 5 had a decrease
of 25 to 50%, and 5 had a decrease of < 25%. One subject became spasm-free and
1 non-responder (with a decrease of < 25%) was spasm-free from weeks 2 to 7.
An anticonvulsant treatment effect signal of GNX in PCDH19-related epilepsy has
emerged from an ongoing OL flexible-dose exploratory study (Study 1042-0900) of
GNX in children (age range 2-15 years) with rare genetic epilepsies (including
PCDH19) with uncontrolled seizures despite multiple antiepileptic drug (AED)
regimens (ClinicalTrials.gov Identifier: NCT02358538). Following the
screening and baseline evaluations, consenting subjects enrolled into a 26-week
study during which investigators could dose GNX starting with a titration up to
1,800 mg/day for subjects whose body weight was > 30 kg or up to 63 mg/kg /day
for subjects whose body-weight was < 30 kg. The dose could also be reduced for
tolerability reasons. The primary efficacy measure was the percent change from
baseline in the 28-day seizure frequency count. Safety and tolerability
assessments were among the secondary objectives. The median change in 28-day
seizure frequency from baseline in the intent-to-treat (ITT) population
(primary endpoint) was a decrease of 25% (n = 11).
The median change from baseline in seizure-free days in the ITT population (key
secondary endpoint) was an increase of 14% (n = 11). Baseline levels of
allopregnanolone sulfate (Allo-S, an endogenous neurosteroid) and 28-day
seizure rates were also assessed. A ganaxolone-responder was specified by
post-hoc definition, as having at least a 25% reduction in 28-day seizure
rate. In the PCDH19 cohort, responders (n = 6) and non-responders (n = 5) had
plasma Allo-S concentrations (mean ± SD) of 501 ± 430 pg mL-1 and 9,829 ± 6,638
pg mL-1, respectively. When performing a retrospective separation of the
PCDH19 cohort according to their Allo-S level, the 7 subjects with Allo-S
levels below 2,500 pg mL-1 (biomarker-positive) had a 50% reduction in seizure
rates while the 4 subjects with Allo-S levels above 2,500 pg mL-1
(biomarker-negative) had a 84% increase (performed in the research lab of Dr.
Graziano Pinna at the University of Illinois, Chicago, the only laboratory
during the conduct of the study that could reliably produce results for
sulphated neurosteroids). The Clinical Global Impression Scale rated by
Investigators (CGI-I) and Caregivers (CGI-P) has been consistent with seizure
control. In the OL study (1042-0900), there were 4 SAEs (3 related to seizures
and 1 related to rash) possibly related to the study drug in the PCDH19
subjects.
In addition to anticonvulsant activity, GNX has shown positive effects on
anxiety, hyperactivity, and attention in children with fragile X syndrome
(Ligsay 2016). Similar behavior problems occur in individuals with PCDH19
mutations (Smith 2018). It is hypothesized that GNX treatment will increase
and improve GABAA-mediated signaling by boosting the signaling capacity of
existing receptors and improve not only seizure control, but also other
behavioral abnormalities in individuals with the PCDH19 mutation.

Primary: To assess the efficacy of GNX compared with PBO, as adjunctive therapy
for the treatment of primary seizure types in children with
genetically-confirmed PCDH19-related epilepsy during the 17-week double-blind
(DB) phase. Secondary: • To assess the effect of GNX on primary seizure rate in
biomarker-positive subjects. • To assess behavioral/neuropsychiatric changes in
subjects receiving GNX compared with subjects receiving PBO as adjunctive
therapy during the 17-week DB phase. • To assess the safety and tolerability of
GNX compared with PBO as adjunctive therapy during of the 17 week DB phase. •
To assess pharmacokinetic (PK) parameters in subjects receiving GNX doses up to
63 mg/kg/day (or 1800 mg/day maximum) throughout the study. • To assess the
long-term efficacy of GNX when administered as adjunctive therapy throughout
the open-label (OL) phase. • To assess the long-term safety and tolerability of
GNX when administered as adjunctive therapy throughout the open-label phase.
Exploratory Efficacy: • To assess the effect of GNX on primary seizure rate in
biomarker-negative subjects, and compare biomarker-positive vs.
biomarker-negative subjects • To assess changes to quality of life as reported
by the parent/caregiver/LAR. • To assess the effect of GNX on background EEG
activity and to assess any major alterations as possible biomarkers for change
in underlying brain function. To assess changes in other types of seizures
(non-primary) in PCDH19-related epilepsy

Methodology: This is a global, biomarker-stratified, DB, randomized,
PBO-controlled trial of adjunctive GNX treatment in children with a confirmed
pathogenic or likely pathogenic PCDH19 mutation. The trial consists of a
12-week prospective baseline period to collect seizure data, followed by a
17-week DB phase, which is then followed by a long-term OL phase. An
interactive web response system (IWRS) will be used to randomize subjects,
dispense drug, track treatment, and maintain the blind throughout the duration
of the study. , AA 12-week daily historical seizure calendar will be reviewed
at the screening visit to determine eligibility per inclusion/exclusion
criteria. Acceptable historical seizure data must include at least 12
consecutive weeks prior to the Screening visit of documenting seizure type and
frequency (also noting seizure-free days). Procedures specific to this protocol
and not otherwise considered standard of care, will not be performed until
written informed consent from the subject*s parent or legally authorized
representative (LAR) and/or subject assent has been appropriately obtained. In
the event that parent/caregiver/LAR do not routinely maintain a daily seizure
calendar or genetic testing has not been performed per standard of care,
written informed consent will be obtained from the parent/LAR and/or subject
assent, and the subject will be asked to return to the clinic for the screening
visit after they have maintained a 12 week daily historical seizure calendar
and/or genetic testing has been completed. During the screening visit, each
subject*s biomarker level will be assessed via a blood draw and subsequent
analytical quantification. Each subject will then be assigned to 1 of 2 groups:
biomarker-positive or biomarker-negative. A subject will be considered
biomarker-positive if her baseline Allo-S level is less than or equal to 2500
pg/mL (Pinna Lab method or similar). The biomarker group assignment will remain
blinded until database unblinding after the study has completed. Based on the
completed 11-subject 1042-0900 Phase 2a study, it is estimated that
approximately 65% of all subjects will be biomarker-positive. Subject
rescreening is allowed as agreed by Sponsor and Investigator unless there is a
general concern for subject safety or an inability for the subject to become
eligible (eg, GNX allergy, sensitivity or exposure, non-PCDH19 and/or other
ineligible epilepsy, chronic prohibited medical condition or treatment).
Subsequent screening should take place at least 30 days from the subject*s last
visit. The DB phase includes 4 weeks of investigational product titration
followed by 13 weeks of dose maintenance. After meeting the eligibility
criteria, approximately 25 children aged 1-17 years (inclusive) with
PCDH19-related epilepsy will be randomly assigned to receive GNX or PBO (1:1
ratio within each biomarker stratum) for 17 weeks in addition to their standard
anti-seizure treatment. Participants will be titrated to 63 mg/kg/day (max 1800
mg/day) over 4 weeks, and then maintained at that dose for another 13 weeks.
Subjects who are not able to tolerate 63 mg/kg/day (or 1800 mg/day maximum) may
be maintained on a lower dose . A minimum dose of 33 mg/kg/day or 900 mg/day is
generally required following the DB escalation period, unless a lower dose is
agreed to with the sponsor due to tolerability issues such as somnolence. Dose
changes including alternative dosing paradigms (e.g., lower dose during the
daytime and higher dose in the evening) should be discussed with the clinical
research organization (CRO)/sponsor medical monitor prior to making the change
or within 48 hours of making the change. Of note the sponsor defers the final
decision to adjust IP to the treating clinician; dose changes may not exceed
the maximum total daily dose defined by the protocol. For any subject who is
unable to be maintained at the minimum dose, the investigator should contact
the sponsor to discuss continued investigational product dosing. Subjects who
discontinue investigational product should undergo a 2-week taper period,
unless otherwise medically indicated such as drug-induced rash. Subjects who
discontinue investigational product treatment before the completion of the DB
phase will continue to be followed per protocol and, at a minimum, subjects
will be encouraged to maintain daily seizure eDiary entries until the DB phase
is completed. These subjects will also return to the site 2 to 4 weeks after
the taper for safety follow-up assessments. After completing the initial
17-week, DB, PBO-controlled treatment phase, all subjects will be treated with
GNX in the OL phase of the study. Ganaxolone subjects will continue GNX
treatment and PBO subjects will titrate onto GNX. To maintain the blind,
subjects initially randomized to GNX will undergo a blinded titration
(increasing PBO doses) for 4 weeks, while PBO subjects will titrate up to 63
mg/kg/day GNX (1800 mg/day maximum) during the same time period. Any subject
who completes the study or discontinues investigational product treatment
should undergo a 2 week drug de-escalation (taper) period and return to the
site 2 weeks later for safety follow-up assessments. Taper is not required if
the subject is receiving the doe of 18 mg/kg/day or 450 mg/day (or lower).
Participants will be required to complete an eDiary to determine GNX*s effect
on seizures. A variety of clinician and caregiver administered instruments will
be used to assess the efficacy of GNX in PCDH19-related epilepsy, and include:
• Behavior Rating Inventory of Executive Function (BRIEF) • Aberrant Behavior
Checklist - Community (ABC-C) • Children*s Sleep Habit Questionnaire (CSHQ) •
Pediatric Quality of Life Inventory - Family Impact Module (PedsQL-FIM) •
Quality of Life Inventory - Disability (QI-Disability) • Caregiver Global
Impression of Change (CGI-C) - Target Behavior, Clinical Global Impression
Improvement (caregiver), and Clinical Global Impression-Improvement (clinician)

Investigational product, dose, and mode of administration: Ganaxolone is to be
administered in increments of 15 mg/kg/day up to 63 mg/kg/day given as an oral
suspension with food. Subjects <= 28 kg will be dosed on an mg/kg basis.
Subjects > 28 kg will be dosed on a fixed regimen in increments of 450 mg/day
up to 1800 mg/day. Ganaxolone is to be administered during the 4-week titration
period of the DB phase of the study as follows: Dosinga for Subjects Weighing <=
28 kg (62 pounds)b Dose Total mg/kg/day Days 6 mg/kg TID 18 1-7 11 mg/kg TID 33
8-14 16 mg/kg TID 48 15-21 21 mg/kg TID 63 22-28 Dosinga for Subjects Weighing
> 28 kg (62 pounds)c Dose mL per Dose Total mg/day Days 150 mg TID 3 450 1-7
300 mg TID 6 900 8-14 450 mg TID 9 1350 15-21 600 mg TID 12 1800 22-28 TID = 3
times daily. a. To be administered in 3 divided doses following a meal or
snack. b. Subjects weighing <= 28 kg will be dosed according to the subject*s
weight in kilograms. c. Subjects > 28 kg will be dosed on a fixed regimen in
increments of 450 mg/day up to 1800 mg/day. Any subject not tolerating the next
dose level can be maintained at the lower dose for additional days before
advancing to the next dose. If the next dose level is still not tolerated, the
subject can drop back to the last tolerated dose. A minimum dose of 33
mg/kg/day or 900 mg/day is generally required following the DB escalation
period, unless a lower dose is agreed to with the sponsor due to tolerability
issues such as somnolence. Dose changes including alternative dosing paradigm
(e.g., lower dose during the daytime and higher dose in the evening) should be
discussed with the sponsor /CRO medical monitor prior to making the change or
within 48 hours of making the change. Of note, the sponsor defers the final
decision to adjust IP to the treating study clinician; dose changes may not
exceed the maximum total daily dose defined by the protocol. For any subject
who is unable to be maintained at the minimum dose, the investigator should
contact the sponsor to discuss continued investigational product dosing.
Subjects who discontinue investigational product treatment before the
completion of the DB phase will continue to be followed per protocol and, at a
minimum, subjects will be encouraged to maintain daily seizure eDiary entries
until the DB phase is completed. These subjects will also return to the site 2
to 4 weeks after the taper for safety follow-up assessments. During the OL
phase, all subjects will be treated with GNX. Those subjects who received GNX
oral suspension in the 17-week DB phase will receive the same GNX dose in the
OL phase of the study. However, to maintain the study blind, GNX subjects will
enter into a 4-week blinded titration phase by increasing PBO doses in addition
to maintaining GNX. Subjects who received PBO oral suspension in the 17-week DB
phase will enter a 4-week, GNX titration period in the OL phase of the study.

Please refer to patient information sheet section 7