A 6 Week Study of MG01CI 1400 mg Compared With Placebo in Adults With ADHD ( Attention Deficit/Hyperactivity )

Inclusion Criteria: * Subject is a man or a non-pregnant, non-lactating woman 18 to 55 years of age, inclusive, at the Screening Visit. * Subject has a diagnosis of ADHD based on criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and DSM5. * Subject has ADHD with at least moderate clinical severity (Clinical Global Impression-Severity \[CGI-S\]) score of 4 or greater). * Subject has a score on the total ADHD symptom score with adult prompts of the CAARS-Inv of at least 22. * Female subjects of childbearing potential must agree to use an effective contraceptive throughout the study * Subject is able to attend the clinic regularly and reliably. * Subject is able to swallow tablets and capsules. * Subject is able to understand, read, write, and speak English fluently to complete the study-related materials (or Hebrew for Israeli subjects). * Subject is able to understand and sign an informed consent form to participate in the study. Exclusion Criteria: * Subject did not respond in the past to 2 adequate trials of stimulant treatments or 1 adequate trial of atomoxetine treatment (in the investigator's judgment). * Subject has any psychiatric condition clinically significant or unstable medical or surgical condition that may preclude safe and complete study participation as determined by the investigator . * Subject has a known or suspected human immune deficiency virus-positive status or has diseases such as acquired immunodeficiency disorder, hepatitis C, hepatitis B, or tuberculosis. * Subject has a history of an allergy or sensitivity to B-complex vitamins. * Subject has a history of intellectual disability or a history or suspicion of autism spectrum disorder. * Subject has a current Axis I diagnosis (other than ADHD) according to the Structured Clinical Interview for DSM IV Axis I Disorders (SCID) or has a lifetime history of bipolar disorder or psychosis. * Subject has used mega-dose vitamin B6/pyridoxine during the 28 days before the Screening Visit. * Subject has used high-dose supplements of omega-3 fatty acids ≥ 500 mg on at least 1 day or folic acid supplements during the 2 weeks before the Screening Visit. * Subject has used an investigational medication/treatment in the 30 days before the Screening Visit * Subject has used any medication or food supplement that the investigator or the medical monitor considers unacceptable during the 14-day period before randomization. * Subject has a current drug or alcohol dependence or substance abuse disorder according to DSM-IV. Subject should also agree to keep their caffeine intake consistent and refrain from consuming ≥300 mg per day of caffeine (no more than three 8-ounce servings of coffee) during the study. * Subject has suicidality, defined as active ideation, an intent or plan, or any significant lifetime suicidal behavior. Subjects exhibiting history (within previous 12 months) of non-suicidal self-injurious behavior will be excluded. * Subject has taken any prescription or non-prescription ADHD medications during the 14 days (for all psychotropic medications other than fluoxetine) or 28 days (for fluoxetine) before the randomization visit. * Subject is significantly visually impaired to an extent that is not able to be corrected by prescription glasses or contact lenses * Subject is related to the sponsor, investigator, or study staff. * Subject has any condition that, in the principal investigator's opinion, would place the subject at risk or influence the conduct of the study or interpretation of results, * Subject cannot fully comprehend the implications of the protocol, cannot comply with its requirements, or is incapable of following the study schedule for any reason. * Subject is pregnant, lactating, or using an inadequate contraceptive method. * If there is a ≥25% change in the CAARS-Inv results between the Interim visit (off drug) assessment and the Baseline assessment, or if the subject does not return for the Baseline CAARS-Inv assessment, the subject will not be randomized. For subjects not needing washout, if there is a ≥25% change in the CAARS-Inv results between the Screening Visit assessment and the Baseline assessment, or if the subject does not return for the Baseline CAARS-Inv assessment, the subject will not be randomized.