The purpose of this study is to evaluate the effect and safety of Lisdexamfetamine dimesylate (Vyvanse®) in the treatment of Attention Deficit Hyperactivity Disorder (ADHD) in children and adolescents with ADHD and comorbid Autism Spectrum Disorder (ASD). This would be a novel study as there is no known safety or efficacy data for amphetamine based medications in this population. In addition, although health related quality of life and executive function are known to improve with the treatment of lisdexamfetamine dimesylate in the ADHD population (Banaschewski 2013; Findling 2009; Turgay 2010), it has not been shown in the co-morbid ADHD and ASD population. ADHD is the most common pediatric neurobiological condition affecting approximately five percent of the pediatric population (Feldman 2009). ASD is being increasingly recognized as affecting a substantial amount of the pediatric population, with recent prevalence data showing 1 in 68 affected (Baio, 2014). Prior to the introduction of DSM-5 (APA, 2013), exclusion criteria precluded the diagnosis of ADHD when ASD was present. Studies have shown that 41%-71% of children with ASD also meet criteria for ADHD (Goldstein 2004, Sturm 2004,Yoshida 2004, Gadow 2006). This means that up to 1% of the population may have co-morbid ADHD and ASD. With the official recognition of this comorbidity, treatment of comorbid ADHD when ASD is also present has been increasingly recognized as an important strategy in improving executive functioning and quality of life in those affected. Studies have indicated that some of the medications commonly used to treat ADHD, are effective and safe when used in comorbid ADHD and ASD. At this time, there have been well designed studies demonstrating safety and efficacy for methylphenidate (Ghuman et al. 2009; Handen et al. 2000; Quintana et al. 1995; RUPP 2005), guanfacine XR (Posey 2004; Scahill 2015), and atomoxetine (Arnold 2006; Harfterkamp 2012).

ADHD is the most common pediatric neurobiological condition affecting approximately five percent of the pediatric population (Faraone, Stephen V., Sergeant, J. et al. 2003; Feldman & Belanger 2009). ASD is being increasingly recognized as affecting a substantial amount of the pediatric population, with recent prevalence data showing 1 in 68 affected (U.S. Department of Health and Human Services 2010). Prior to the introduction of DSM-5, exclusion criteria precluded the diagnosis for ADHD when ASD was present (American Psychiatric Association 2013). Studies have shown that 41%-71% of children with ASD also meet criteria for ADHD, meaning up to 1% of the population may have comorbid ADHD and ASD (Goldstein & Schewbach 2004).

With the official recognition of comorbidity, treatment of comorbid ADHD when ASD is also present has been increasingly recognized as an important strategy in decreasing ADHD symptoms, and improving executive functioning and quality of life of those affected. Studies have indicated that some of the medications (methylphenidate, guanfacine XR and atomoxetine) commonly used to treat ADHD are effective and safe when used in comorbid ADHD and ASD (Ornstein & Kollins 2012; Ghuman et al. 2009; Handen et al. 2000; Quintana et al. 1995; Posey et al. 2004; Scahill et al. 2015; M. et al. 2012). While amphetamine class compounds are amongst the first line of treatment in ADHD, the lack of studies in this population has discouraged their use in subjects with comorbid ADHD and ASD.

The lack of safety and efficacy data is problematic as it limits therapeutic options for the population of subjects with ADHD and ASD. Amphetamines and methylphenidate medications are equally considered first line treatment options for ADHD (CADDRA 2011). Some subjects may preferentially respond to one group of medications over another, therefore it is important to have clear safety and efficacy data for both therapeutic options.

A retrospective chart review of this population indicates that treatment is started with methylphenidate versus combined amphetamine/dextroamfetamine at a ratio of 2.78:1 (Stigler et al. 2004). Due to the availability of evidence of efficacy in this comorbid population, clinicians may choose to skip to what is considered a second line medication for ADHD symptomatology rather than using LDX (or another amphetamine-based ADHD medication such as dexedrine or Adderall XR) that may have a larger effect size for treating these symptoms.

LDX has been shown to be an effective treatment for ADHD in subjects 6 and above. With long lasting effectiveness shown to last up to 14 hours, it could potentially improve ADHD symptoms and overall quality of life for children and adolescents with ADHD and ASD in home, school and after-school functioning.

The purpose of this study is to evaluate the safety and efficacy of LDX in treating ADHD when ASD is co-morbid.

Inclusion Criteria:

1. Male or female subject aged 6-12 years at the time of consent/assent.
2. Subjects parent(s) or legally authorized representative (LAR) must provide signature of informed consent, and there must be documentation of assent (if applicable) by the subject in accordance with the International Council on Harmonisation (ICH) Good Clinical Practice (GCP) Guideline E6 (1996), any updates or revisions, and applicable regulations, before completing any study related procedures.
3. Subject and parent(s)/LAR are willing and able to comply with all of the requirements defined in the protocol.
4. Subject meets Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-V) criteria for a diagnosis of ADHD combined presentation, inattentive presentation or hyperactive/impulsive presentation based on history and a minimum ADHD-RS score of 32 and a minimum CGI-S of 4 at baseline.
5. Subject meets DSM-V criteria for a diagnosis of ASD-level 1 based on history and Autism Diagnostic Observation Scale (ADOS-2).
6. Subject has an SRS-2 total score of ≥ 70.
7. Subject has a Clinical Global Impressions - Severity of Illness (CGI-S) score ≥ 4 at the baseline visit (visit 2)
8. Subject has a blood pressure measurement within 95th percentile for age, and sex (Appendix 1,1.1,2 & 2.2). Subject and parent/legally authorized representative (LAR) are willing, able and likely to comply with the study procedures and restrictions within the protocol.

Exclusion Criteria:

1. Subject has any condition that, in the opinion of the investigator, represent an inappropriate risk to the subject or may confound the interpretation of the study.
2. Subject has a known history or presence of structural cardiac abnormalities, cardiovascular or cerebrovascular disease, serious heart rhythm abnormalities, syncope, tachycardia, cardiac conduction problems (such as clinically significant heart block or QT interval prolongation), exercise-related cardiac events including syncope and pre-syncope or clinically significant bradycardia.
3. Subject has a known history of symptomatic cardiovascular disease, unexplained syncope, exertional chest pain, advanced arteriosclerosis, structural cardiac abnormality, cardiomyopathy, serious heart rhythm abnormalities, coronary artery disease or other serious cardiac problems placing them at increased vulnerability to sympathomimetic effects of a stimulant drug.
4. Subject has a history of seizure disorder (other than a single childhood febrile seizure occurring before the age of 3 years).
5. Subject has glaucoma.
6. Subject is currently using prohibited medication.
7. Subject has a known or suspected allergy, hypersensitivity, or clinically significant intolerance to LDX.
8. Subject has taken another investigational product within 30 day prior to baseline.
9. Subject has initiated behavioural therapy within 1 month of the baseline visit (visit 0). Subject may not initiate behavioural therapy during the study.
10. Subject is female and is pregnant or currently lactating.
11. Subject is currently considered a suicide risk in the opinion of the investigator, has previously made a suicide attempt, or has a prior history of or is currently demonstrating active suicide ideation. Subjects with intermittent passive suicidal ideation are not necessarily excluded based on the assessment of the investigator.
12. History of failure to respond to an adequate trial of an amphetamine based medication.
13. Subject is currently abusing an illicit substance or lives with someone known to currently abuse stimulants or cocaine..
14. Subject has a known renal or hepatic insufficiency.