The AISRS is an 18-item clinician-rated instrument for assessing the 18 core symptoms of ADHD corresponding to the DSM-IV diagnostic symptoms for adults. Based on the clinician's rating for each of the symptoms using a 4-point scale (0=None to 3=Severe), the AISRS total score is derived by summing the score assigned to each of the 18 symptoms. Scores can range from 0 to 54, with a higher score indicating a more severe ADHD symptoms. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2. Reduction was defined as the relative change from the baseline score within a treatment period to post-baseline score within that treatment period.

An AE is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of an investigational product, whether or not related to the investigational product. AEs are reported by study drug taken at time of event and not by randomly assigned sequence.

An AE is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of an investigational product, whether or not related to the investigational product. AEs are reported by study drug taken at time of event and not by randomly assigned sequence.

The CGI-S is a 7-point clinician-rated scale for assessing the global severity of ADHD. Scores could range from 1=Normal, not at all ill to 7=Among the most extremely ill, with a higher score indicating more severe illness. Categorization was as follows: 1=Normal, not at all ill and Borderline mentally ill; 2=Mildly ill; 3=Moderately ill and 4=Markedly ill, Severely ill and Among the most extremely ill patients, with a higher category indicating more severe illness. Analysis of CGI-S was performed using a proportional odds model. For statistical analyses, CGI-S assessments were condensed to one assessment of severity per treatment period by taking the most severe score at the second and third visits within a treatment period.

The CGI-I is a 7-point clinician-rated scale for assessing the global improvement of ADHD. Scores could range from 1=Very much improved to 4=No change to 7=Very much worse, with a lower score indicating the most improvement. Analysis of CGI-I was performed using a proportional odds model. For statistical analyses, CGI-I assessments were condensed to one assessment of improvement per treatment period by taking the worst improvement score at the second and third visits within a treatment period.

The ESS is an 8-item scale used to assess sleepiness. The test consists of a list of 8 situations in which participants rate their tendency to become sleepy on a scale of 0=Would never doze to 3=High chance of dozing. The scores for each of the 8 situations are added to create a total score on a scale with a range from of 0 to 24. A higher score indicates a greater degree of sleepiness. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The PSQI is a participant-rated scale to assess the quality of sleep. The PSQI consists of 7 component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Each component score can range from 0=better (i.e., 0 times per month) to 3=worse (i.e., 3 or more times per week). The sum of these 7 component scores yields one total score with a range of 0 (better) to 21 (worse). A total PSQI score <=5 is associated with good sleep quality; a total score >5 is associated with poor sleep quality. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The QIDS-C is a clinician-administered rating scale to measure the severity of depressive symptoms within the 9 DSM-IV major depression disorder symptom (MDD) domains: depressed mood, loss of interest or pleasure, concentration/decision making, self-outlook, suicidal ideation, energy/fatigability, sleep, weight/appetite change, and psychomotor changes. There is one score (0=none to 3=severe) for each of the of the 9 domains. The total score is obtained by adding the scores for each of the 9 symptom domains. QIDS-C total scores can range from 0 to 27, with a higher score indicating more severe depression. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The TASS is a participant-administered scale to assess study drug effects in the evening. Participants respond to 18 questions about ADHD symptoms, with scores from 0=Not at all to 3=Severe. Total scores can range from 0 to 54, with a higher score indicating more severe ADHD symtoms. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

Cognition was assessed by a computerized cognitive testing (©CNS Vital Signs, Chapel Hill, NC) battery consisting of neuropsychological tests that measure the cognitive domain of cognitive flexibility (score range: -200 to 200), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of complex attention (score range: 0 to 250), with a lower score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of composite memory (score range: -120 to 120), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of executive functioning (score range: -200 to 200), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of speed of processing (score range: -1000 to 200), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of reaction time (lowest time possible is 0 msec), with a lower reaction time indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of reasoning (score range: -15 to 15), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of sustained attention (score range -120 to 120), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of verbal memory (score range: -60 to 60), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of visual memory (score range: -60 to 60), with a higher score indicating better cognition.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of working memory (score range: -48 to 48), with a higher score indicating better cognition.

Participants receive rising doses of MK-8777 100-300 mg BID for 3 weeks (Treatment Period 1). After a 2-week placebo washout period, participants receive rising doses of placebo BID for 3 weeks (Treatment Period 2).

Participants receive rising doses of placebo BID for 3 weeks (Treatment Period 1). After a 2-week placebo washout period, participants receive rising doses of MK-8777 100-300 mg BID for 3 weeks (Treatment Period 2).

Total of all reporting groups

The AISRS is an 18-item clinician-rated instrument for assessing the 18 core symptoms of ADHD corresponding to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) diagnostic symptoms for adults. Based on the clinician's rating for each of the symptoms using a 4-point scale (0=None to 3=Severe), the AISRS total score is derived by summing the score assigned to each of the 18 symptoms. Scores can range from 0 to 54, with a higher score indicating a more severe ADHD symptoms. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2. Reduction was defined as the relative change from the baseline score within a treatment period to post-baseline score within that treatment period.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug, and who had at least one postbaseline AISRS efficacy assessment.

The AISRS is an 18-item clinician-rated instrument for assessing the 18 core symptoms of ADHD corresponding to the DSM-IV diagnostic symptoms for adults. Based on the clinician's rating for each of the symptoms using a 4-point scale (0=None to 3=Severe), the AISRS total score is derived by summing the score assigned to each of the 18 symptoms. Scores can range from 0 to 54, with a higher score indicating a more severe ADHD symptoms. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2. Reduction was defined as the relative change from the baseline score within a treatment period to post-baseline score within that treatment period.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug, and who had at least one postbaseline AISRS efficacy assessment.

An AE is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of an investigational product, whether or not related to the investigational product. AEs are reported by study drug taken at time of event and not by randomly assigned sequence.

The All-Subjects-Treated (AST) population consisted of all participants who received at least one dose of randomized study drug within at least one of the two treatment periods (excluding the placebo run-in period).

An AE is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of an investigational product, whether or not related to the investigational product. AEs are reported by study drug taken at time of event and not by randomly assigned sequence.

The AST population consisted of all participants who received at least one dose of randomized study drug within at least one of the two treatment periods (excluding the placebo run-in period).

The CGI-S is a 7-point clinician-rated scale for assessing the global severity of ADHD. Scores could range from 1=Normal, not at all ill to 7=Among the most extremely ill, with a higher score indicating more severe illness. Categorization was as follows: 1=Normal, not at all ill and Borderline mentally ill; 2=Mildly ill; 3=Moderately ill and 4=Markedly ill, Severely ill and Among the most extremely ill patients, with a higher category indicating more severe illness. Analysis of CGI-S was performed using a proportional odds model. For statistical analyses, CGI-S assessments were condensed to one assessment of severity per treatment period by taking the most severe score at the second and third visits within a treatment period.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug, and who had at least one postbaseline CGI-S efficacy assessment.

The CGI-I is a 7-point clinician-rated scale for assessing the global improvement of ADHD. Scores could range from 1=Very much improved to 4=No change to 7=Very much worse, with a lower score indicating the most improvement. Analysis of CGI-I was performed using a proportional odds model. For statistical analyses, CGI-I assessments were condensed to one assessment of improvement per treatment period by taking the worst improvement score at the second and third visits within a treatment period.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug, and who had at least one postbaseline CGI-I efficacy assessment.

The ESS is an 8-item scale used to assess sleepiness. The test consists of a list of 8 situations in which participants rate their tendency to become sleepy on a scale of 0=Would never doze to 3=High chance of dozing. The scores for each of the 8 situations are added to create a total score on a scale with a range from of 0 to 24. A higher score indicates a greater degree of sleepiness. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline ESS efficacy assessment.

The PSQI is a participant-rated scale to assess the quality of sleep. The PSQI consists of 7 component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Each component score can range from 0=better (i.e., 0 times per month) to 3=worse (i.e., 3 or more times per week). The sum of these 7 component scores yields one total score with a range of 0 (better) to 21 (worse). A total PSQI score <=5 is associated with good sleep quality; a total score >5 is associated with poor sleep quality. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline PSQI efficacy assessment.

The QIDS-C is a clinician-administered rating scale to measure the severity of depressive symptoms within the 9 DSM-IV major depression disorder symptom (MDD) domains: depressed mood, loss of interest or pleasure, concentration/decision making, self-outlook, suicidal ideation, energy/fatigability, sleep, weight/appetite change, and psychomotor changes. There is one score (0=none to 3=severe) for each of the of the 9 domains. The total score is obtained by adding the scores for each of the 9 symptom domains. QIDS-C total scores can range from 0 to 27, with a higher score indicating more severe depression. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline QIDS-C efficacy assessment.

The TASS is a participant-administered scale to assess study drug effects in the evening. Participants respond to 18 questions about ADHD symptoms, with scores from 0=Not at all to 3=Severe. Total scores can range from 0 to 54, with a higher score indicating more severe ADHD symtoms. Baseline was defined as the score at the baseline visit prior to starting dosing for Period 1 and as the last score in the 2-week placebo wash-out period for Period 2.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline TASS efficacy assessment.

Cognition was assessed by a computerized cognitive testing (©CNS Vital Signs, Chapel Hill, NC) battery consisting of neuropsychological tests that measure the cognitive domain of cognitive flexibility (score range: -200 to 200), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for cognitive flexibility.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of complex attention (score range: 0 to 250), with a lower score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for complex attention.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of composite memory (score range: -120 to 120), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for composite memory.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of executive functioning (score range: -200 to 200), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for executive functioning.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of speed of processing (score range: -1000 to 200), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for speed of processing.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of reaction time (lowest time possible is 0 msec), with a lower reaction time indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for reaction time.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of reasoning (score range: -15 to 15), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for reasoning.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of sustained attention (score range -120 to 120), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for sustained attention.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of verbal memory (score range: -60 to 60), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for verbal memory.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of visual memory (score range: -60 to 60), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for visual memory.

Cognition was assessed by a computerized cognitive testing battery consisting of neuropsychological tests that measure the cognitive domain of working memory (score range: -48 to 48), with a higher score indicating better cognition.

The ITT population consisted of all participants who were randomized, who received at least one dose of study drug in at least one period, and who had at least one postbaseline computerized cognition efficacy assessment for working memory.

Participants receive a fixed dose of MK-8777 100 mg BID for up to 3 weeks.

Participants receive rising doses of MK-8777 100-300 mg BID for up to 3 weeks.

The treatment difference between 100-300 mg MK-8777 rising dose and Placebo was estimated for the average effect (average change from baseline) of the 2nd and 3rd week of each period (Day 14 and Day 21).

To correct for multiplicity, p-values (2-sided) should be compared with the 2.5% level of significance.

MMRM with fixed effects for treatment, period, visit, center and treatment by visit interaction, and random effect for participant, and baseline ESS score as covariate. For statistical analyses, the average score from Days 14 and 21 was used.

The treatment difference between 100-300 mg MK-8777 rising dose and Placebo was estimated for the average effect (average change from baseline) of the 2nd and 3rd week of each period (Day 14 and Day 21).

To correct for multiplicity, p-values (2-sided) should be compared with the 2.5% level of significance.

MMRM with fixed effects for treatment, period, visit, center and treatment by visit interaction, and random effect for participant, and baseline PSQI score as covariate.

The treatment difference between 100-300 mg MK-8777 rising dose and Placebo was estimated for the average effect (average change from baseline) of the 2nd and 3rd week of each period (Day 14 and Day 21).

To correct for multiplicity, p-values (2-sided) should be compared with the 2.5% level of significance.