A Study of PDC-1421 Treatment in Adult Patients With Attention-Deficit Hyperactivity Disorder (ADHD)

Inclusion Criteria:

1. Aged 18-70 years

2. Female subjects of child-bearing potential must test negative to pregnancy and use
appropriate birth control method from the beginning of study to the 15 days later
after ending of study

3. Subjects must be able to understand and willing to sign informed consent

4. Able to discontinue the use of any psychotropic medications for the treatment of ADHD
symptoms at screening

5. Meet strict operational criteria for adult ADHD according to the Diagnostic and
Statistical Manual of Mental Disorders, 5th Edition (DSM-5)

6. A total score of 20 or higher on the 18-item total ADHD symptoms score of Conners'
Adult Attention-Deficit/Hyperactivity Disorder Rating Scale-Self Report: Short Version
(CAARS-S:S) at screening

7. Have a moderate or severe symptom of ADHD with score of 4 or higher in Clinical Global
Impression-ADHD-Severity (CGI-ADHD-S) at screening

Exclusion Criteria:

1. Have any clinically significant concurrent medical condition (endocrine, renal,
respiratory, cardiovascular, hematological, immunological, cerebrovascular,
neurological, anorexia, obesity or malignancy) that has become unstable and may
interfere with the interpretation of safety and efficacy evaluations

2. Have any clinically significant abnormal laboratory, vital sign, physical examination,
or electrocardiogram (ECG) findings at screening that, in the opinion of the
investigator, may interfere with the interpretation of safety or efficacy evaluations

3. Have known serological evidence of human immunodeficiency virus (HIV) antibody

4. Are pregnant as confirmed by a positive pregnancy test at screening

5. Have QTc values >450 msec at screening using Fridericia's QTc formula

6. Have current of bipolar and psychotic disorders

7. Have a current major depression disorder, obsessive-compulsive disorder,
post-traumatic stress disorder, generalized anxiety disorder, panic disorder and
eating disorder (also if treated but not currently symptomatic)

8. Have any history of a significant suicide attempt, or possess a current risk of
attempting suicide, in the investigator's opinion, based on clinical interview and
responses provided on the Beck Scale for Suicidal Ideation (BSS)

9. Have a history of jailing or imprisonment in the past 6 months due to worsening of
symptoms of ADHD