Outline of Research Plan The investigators will recruit 40 adolescents with ASD (age
13-17) to participate in an 8-week open label clinical trial of gabapentin, with
wraparound neuroimaging to assess the primary outcome of Aim 1 (response of RAI GABA
levels to 8 weeks of gabapentin treatment) and Aim 2 (evaluation of acute response
to gabapentin as a predictor of response at 8 weeks). Clinical measures of social
cognition described below will be obtained to address Aim 3 (to assess for
clinically measurable improvements in social cognition deficits).
Clinical Assessments The subjects will be assessed with the Autism Diagnostic
Observation Schedule (ADOS-2) and Autism Diagnostic Interview-Revised (ADI-R) to
confirm the diagnosis of ASD. The Ohio Autism Clinical Impressions Scale will assess
overall severity of autism-specific symptoms. The Mini International
Neuropsychiatric Interview for Children and Adolescents (MINI-KID 7.0.2) will be
used to document comorbid psychiatric diagnoses. The Weschler Abbreviated Scales of
Intelligence (WASI-2) will be used to assess IQ. Social cognition deficits will be
assessed using the Reading the Mind in the Eyes test (RMET), the Social
Responsiveness Scale (SRS-2), and the Vineland Adaptive Behavior Scales-II (VABS-II)
Socialization subdomain. The Aberrant Behavior Checklist, Community version (ABC),
will be used to quantify behavioral measures associated with ASD. To assess whether
clinical improvements with gabapentin extend beyond effects on social cognition,
other symptom domains will be assessed pre- and post-treatment as well.
Specifically, information on repetitive and/or compulsive behaviors will be obtained
using the Children's Yale-Brown Obsessive Compulsive Scale modified for Pervasive
Developmental Disorders (CY-BOCS-PDD). The ADHD Rating Scale-IV (ADHD RS-IV) will be
used to assess ADHD symptoms, the Children's Depression Rating Scale (CDRS) to
assess depressive symptoms and the Multidimensional Anxiety Scale for Children, 2nd
edition, (MASC-2) will be used to assess anxiety-related symptoms.
In addition to traditional outcome measures for social functioning in ASD, including
parent report measures (SRS-2) and theory of mind tasks (RMET), a novel technique of
measuring social motor coordination will be used that was developed as a potential
outcome measure in ASD clinical trials. This assessment involves a video-based
analysis of whole-body social motor coordination during a more naturalistic task,
the conversation task of an ADOS-2 administration. Changes in social motor
coordination will be evaluated in relation to changes in GABA levels with treatment
over the course of the clinical trial.
Baseline MRI T1- and T2-weighted high-resolution structural imaging (T1- and
T2-weighted (MPRAGE)) will be acquired, along with a baseline MRS using
MEsher-Garwood Point REsolved Spectroscopy Sequence (MEGA-PRESS: TE: 68 ms, TR: 2 s)
to quantify GABA in a 4 cm x 2.5 cm x 2.5 cm voxel localized in the RAI. Imaging
sessions will be conducted at the Advanced MRI Center (AMRIC) at UMMS, which houses
a 3.0 Tesla Philips Achieva MRI research scanner (Philips Healthcare, Best,
Netherlands) and 8 element phase-array receiver SENSE head coil.
The baseline MRI protocol also leverages collaborations with the Human Connectome
(HCP) and Adolescent Brain Cognitive Developments (ABCD) projects and is designed to
support integration with national multi-site studies for added protocol utility. The
scan session will include 1) a 3D T1-weighted magnetization-prepared rapid
acquisition gradient echo scan for cortical and subcortical segmentation (6.5 min);
- a 3D T2-weighted variable flip angle fast spin echo scan for screening out white
matter lesions and quantification of CSF (6 min); 3) a diffusion imaging scan, for
segmentation of white matter tracts and measurement of diffusion parameters (1.5mm
isotropic, b=1000; 110 directions acquired with both AP and PA phase encoding; 2 x 5
min); 4) a resting state fMRI scan (2mm isotropic ; TR 750 ms; AP, PA phase
encoding; (2-5.75 min runs).
Acute Response of GABA levels A second MRS scan will be obtained two hours after an
approximately 20 mg/kg challenge with gabapentin to obtain the acute response for
Aim 2. Subjects will receive a single dose of gabapentin. The dose used will be
calculated to provide the highest possible dose to the nearest 100 mg without
exceeding 1500 mg or 20 mg/kg, whichever is lower. The weight exclusion criteria
ensures that all subjects will receive at least 17 mg/kg dose. All subjects will be
monitored for adverse effects for up to 4 hours following administration of the
single dose and will have direct phone access to the principal investigator (24
hours/ 7 days a week) for reporting of any post-observation adverse effects. A blood
sample to assess drug level will be taken as close to 3 hours after administration
as possible, allowing time for imaging scan and transport to clinical trials unit
for blood draw. This will be used to control for variability in bioavailability in
interpreting the cortical GABA level changes.
Clinical Trial of Gabapentin The study involves an 8-week open-label clinical trial
with gabapentin in 40 adolescents age 13-17 years who meet DSM-5 criteria for ASD.
At the acute gabapentin dosing visit, baseline safety labs will be obtained,
including complete blood count; comprehensive metabolic panel including
electrolytes, renal function tests, and liver function tests; and creatine kinase.
Baseline EKG will be obtained as well. The above labs will be repeated at week 4 and
week 8 of the clinical trial, or if adverse events occur which indicate the need for
testing.
At baseline and at Weeks 2, 4, and 8, the following clinical measures will be obtained:
OACIS-S, OACIS-I (for post-baseline visits). At baseline and at 8 weeks, the following
assessments will also be administered: VABS-II, SRS-2 (modified to ask about symptoms in
previous 2 weeks), RMET, ABC, CY-BOCS-PDD, ADHD-RS-IV, MASC-2, and CDRS-R. ADOS-2 will
also be re-administered at week 8 for videotape assessment of social motor coordination
as described above. At week 8, a trough serum gabapentin level will be obtained to
account for variability in bioavailability as a potential confounding factor. At week 8,
the MRS scan will be repeated to evaluate RAI GABA levels, and also include a resting
state functional MRI scan.