Adverse events will be classified using the Medical Dictionary for Regulatory Activities (MedDRA) classification system.

A questionnaire used to assess suicide risk.

Tanner Staging of sexual development assessment will be used to assess sexual maturity.

The ACR Pedi 30 is defined as a minimum of 30 percent improvement from baseline in a minimum of 3 out of 6 components, with no more than 1 component worsening by \>30 percent. The ACR Pedi consists of 6 core criteria: 1. physician global assessment (PGA) of disease activity (visual analog scale \[VAS\]) where 0 represents no disease activity and 100 represents the most disease activity 2. assessment of overall well-being (VAS) where 0 represents very well and 100 represents very poor for overall well-being 3. functional ability (assessed using the Childhood Health Assessment Questionnaire \[CHAQ\]); 4. number of joints with active arthritis (defined as joints with swelling not caused by deformity or joints, in the absence of swelling, with limitation of passive motion accompanied by pain, tenderness, or both) 5. number of joints with limited range of motion 6. laboratory marker of inflammation (C-reactive protein \[CRP\]).

A PPPASI 50 response is defined as a ≥ 50% reduction in PPPASI total score from baseline. The PPPASI is a system used for assessing and grading the severity (in terms of erythema, pustules/vesicle and desquamation/scale) and area of PPP lesions and their response to therapy. The PPPASI produces a numeric score that can range from 0 to 72, with a higher score indicating more severe disease. Participants who discontinued investigational product before week 16 due to lack of efficacy, adverse event, or use of protocol-prohibited medication (intercurrent events) were to be considered as treatment failures as the result of the intercurrent event and the PPPASI-50 values for visits on and after the intercurrent event were imputed as non-responders. The missing PPPASI-50 values due to the other reasons were imputed using the multiple imputation method.

Confirmed clinical recovery means the participant is fit for discharge from hospital, defined by achieving a score of 6 (hospitalized, not requiring supplemental oxygen, no longer requires ongoing medical care), 7 (not hospitalized, limitation on activities and/or requiring home oxygen), or 8 (not hospitalized, no limitations on activities) on the clinical severity status 8-point ordinal scale, without being re-hospitalized prior to Day 29. The Kaplan-Meier estimate of the time to confirmed clinical recovery through Day 29, without re-hospitalization through Day 29, was calculated from Study Day 1 to the earliest date on which the participant had a score of 6, 7, or 8 up to Day 29. Participants who never reached a score of 6, 7, or 8 on the clinical severity status 8-point ordinal scale before or on Day 29 were censored at Day 29. Participants who discontinued from the study before or on Day 29 were censored at time of discontinuation from study.

Confirmed clinical recovery means the participant is fit for discharge from hospital, defined by achieving a score of 6 (hospitalized, not requiring supplemental oxygen, no longer requires ongoing medical care), 7 (not hospitalized, limitation on activities and/or requiring home oxygen), or 8 (not hospitalized, no limitations on activities) on the clinical severity status 8-point ordinal scale, without being re-hospitalized prior to Day 29. The Kaplan-Meier estimate of the time to confirmed clinical recovery through Day 29, without re-hospitalization through Day 29, was calculated from Study Day 1 to the earliest date on which the participant had a score of 6, 7, or 8 up to Day 29. Participants who never reached a score of 6, 7, or 8 on the clinical severity status 8-point ordinal scale before or on Day 29 were censored at Day 29. Participants who discontinued from the study before or on Day 29 were censored at time of discontinuation from study.

Confirmed clinical recovery means the participant is fit for discharge from hospital, defined by achieving a score of 6 (hospitalized, not requiring supplemental oxygen, no longer requires ongoing medical care), 7 (not hospitalized, limitation on activities and/or requiring home oxygen), or 8 (not hospitalized, no limitations on activities) on the clinical severity status 8-point ordinal scale, without being re-hospitalized prior to Day 29. The Kaplan-Meier estimate of the time to confirmed clinical recovery through Day 29, without re-hospitalization through Day 29, was calculated from Study Day 1 to the earliest date on which the participant had a score of 6, 7, or 8 up to Day 29. Participants who never reached a score of 6, 7, or 8 on the clinical severity status 8-point ordinal scale before or on Day 29 were censored at Day 29. Participants who discontinued from the study before or on Day 29 were censored at time of discontinuation from study.

An AE is any noxious, unintended, or untoward medical occurrence that may appear or worsen in a subject during the course of a study. It may be a new intercurrent illness, a worsening concomitant illness, an injury, or any concomitant impairment of the subject's health, including laboratory test values, regardless of etiology. Any worsening (ie, any clinically significant adverse change in the frequency or intensity of a preexisting condition) should be considered an AE.

Body weight in kg

BMI (combined outcome of weight and height in the form of kg/m\^2)

Height (inches or centimeters) will be collected for all pediatric subjects and descriptively summarized

Sexual maturation, assessed by Tanner staging system, will be conducted for all pediatric subjects and descriptively summarized

The sPGA is an assessment by the Investigator of the overall disease severity at the time of evaluation. Erythema (E), induration (I), and desquamation (D) are scored on a 5-point scale, ranging from 0 (clear) to 4 (severe). The National Psoriasis Foundation Psoriasis Score version of a static PGA is calculated by averaging the total body erythema, induration, and desquamation scores. The overall scores are as follows: 0 = Clear; 1. = Almost Clear; 2. = Mild; 3. = Moderate; 4. = Severe. The percentage of participants with a sPGA response was estimated using a multiple imputation method from 100 imputed data sets.

The sPGA is a 5-point scale where 0 = clear, 1 = almost clear, 2 = mild, 3 = moderate, and 4 =severe. Scores incorporate an assessment by the Investigator of the severity of the 3 primary signs of the disease: erythema, scaling and plaque elevation. An sPGA response is defined as sPGA score of clear (0) or almost clear (1) and with at least a 2-point reduction from baseline at Week 16.

The modified sPGA-G is the assessment by the Investigator of the participant's psoriasis lesions' overall disease severity in the genital area at the time of evaluation. The modified sPGA-G is a 5-point scale ranging from clear (0), almost clear (1), mild (2), moderate (3), to severe (4), incorporating an assessment of the severity of the 3 primary signs of the disease: erythema, plaque elevation, and scaling. A modified sPGA-G response is defined as modified sPGA-G score of clear (0) or almost clear (1) and with ≥ 2-point reduction from Baseline at Week 16. Missing values were imputed using the multiple imputation (MI) method. Two-sided 95% confidence intervals (CIs) for the within-group proportions were based on the Wilson-score method.

The sPGA is the assessment by the Investigator of the overall disease severity of plaque psoriasis at the time of evaluation. The sPGA is a 5-point scale ranging from 0 (clear) to 4 (severe), incorporating an assessment of the severity of the three primary signs of the disease: erythema, scaling and plaque elevation. The results presented are for the percentage of participants with a sPGA response. An sPGA response was defined as a score of clear (0) or almost clear (1) with at least a 2-point reduction from baseline at Week 16.

The ScPGA is a measurement of overall scalp involvement by the investigator at the time of evaluation. The ScPGA is a 5-point scale ranging from 0 (clear) to 4 (severe), incorporating an assessment of the severity of the 3 primary signs of the disease: erythema, scaling, and plaque elevation. When making the assessment of overall scalp severity, the investigator factored in areas that had already been cleared (ie, had scores of 0), not limited to the evaluation of remaining lesions for severity; consequently, the severity of each sign was averaged across all areas of involvement, including cleared lesions.

The number of oral ulcers that was counted for the analysis of the primary endpoint included current and recurrent ulcers at each time point; a single oral ulcer could be recounted multiple times if it persisted or recurred at subsequent visits.

Percentage of participants with an American College of Rheumatology 20% (ACR20) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: * ≥ 20% improvement in 78 tender joint count; * ≥ 20% improvement in 76 swollen joint count; and * ≥ 20% improvement in at least 3 of the 5 following parameters: * Patient's self-assessment of pain (measured on a 0 to 10 unit numeric rating scale \[NRS\]); * Patient's global self-assessment of disease activity (measured on a 0 to 10 unit NRS); * Physician's global assessment of disease activity (measured on a 0 to 10 unit NRS); * Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index \[HAQ-DI\]); * C-Reactive Protein (CRP) Those who withdrew early or who did not have sufficient data at Week 16 were counted as non-responders.

PASI-75 response is the percentage of participants who achieved at least a 75% reduction (improvement) from baseline in PASI score at Week 16. The improvement in PASI score was used as a measure of efficacy. The PASI was a measure of psoriatic disease severity taking into account qualitative lesion characteristics (erythema, thickness, and scaling) and degree of skin surface area involvement on defined anatomical regions. PASI scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). The PASI score was set to missing if any severity score or degree of involvement was missing.

ASAS 20 was defined as achieving an improvement from baseline of ≥ 20% and ≥ 1 unit in at least 3 of 4 ASAS domains on a scale of 0 to 10 units and no worsening from baseline of ≥ 20% and ≥ 1 unit in the remaining ASAS domain on a scale of 0 to 10 units. The 4 ASAS domains are: 1. Patient Global Assessment of Disease (0 - 10 unit Numerical Rating Scale \[NRS\]); participant marks a box with an X on a 0 - 10 unit NRS; the left-hand box of 0 = not active and the right-hand box = very active 2. Total Back Pain (0 to 10 unit NRS); participant marks a box with an X on a 0 - 10 unit NRS; the left-hand box of 0 = "no pain" and the right-hand box = "most severe pain" 3. Function (Bath AS Functional Index \[BASFI\] NRS 0 - 10 unit); participant provides a self-administered survey of 10 questions assessing for degree of mobility and functional ability 4. Inflammation domain is determined by the mean of 2 Bath AS Disease Activity Index NRS Questions #5 and #6 for morning stiffness) (0 - 10 unit)

A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 20% improvement in 78 tender joint count; • ≥ 20% improvement in 76 swollen joint count; and • ≥ 20% improvement in at least 3 of the 5 following parameters: -Patient's assessment of pain (measured on a 100 mm visual analog scale \[VAS\]); -Patient's global assessment of disease activity (measured on a 100 mm VAS); -Physician's global assessment of disease activity (measured on a 100 mm VAS); -Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index (HAQ-DI)); -C-Reactive Protein.

PASI-75 response is the percentage of participants who achieved at least a 75% reduction (improvement) from baseline in PASI score at week 16. The improvement in PASI score was used as a measure of efficacy. The PASI is a measure of psoriatic disease severity taking into account qualitative lesion characteristics (erythema, thickness, and scaling) and degree of skin surface area involvement on defined anatomical regions. PASI scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). The PASI score was set to missing if any severity score or degree of involvement is missing.

PASI-75 response is the percentage of participants who achieved at least a 75% reduction (improvement) from baseline in PASI score at Week 16. The improvement in PASI score was used as a measure of efficacy. The PASI was a measure of psoriatic disease severity taking into account qualitative lesion characteristics (erythema, thickness, and scaling) and degree of skin surface area involvement on defined anatomical regions. PASI scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). The PASI score was set to missing if any severity score or degree of involvement is missing.

PPPASI-50 is defined as \>= 50 percent decrease in PPPASI total score from baseline. PPPASI is a disease-specific efficacy assessment tool to evaluated for 3 signs of the disease (erythema, pustules/vesicle and desquamation/scale) as sub-scores on palms or soles. The PPPASI total scores are calculated by sum of the sub-scores and range from 0 to 72 with a higher score indicating more severe disease.

A TEAE is an adverse event with a start date on or after the date of the first dose of apremilast and no later than 28 days after the last dose of apremilast. An adverse event is any noxious, unintended, or untoward medical occurrence that may appear or worsen in a subject during the course of a study. It may be a new intercurrent illness, a worsening concomitant illness, an injury, or any concomitant impairment of the subject's health, including laboratory test values, regardless of etiology. A serious AE is any untoward AE that results in death, is life threatening, requires inpatient hospitalization or prolongation of existing hospitalization or in persistent or significant disability/incapacity, results in a congenital anomaly/birth defect or constitutes an important medical event. The investigator assessment of severity/intensity of an event was defined as mild, moderate or severe.

Maximum observed plasma concentration (Cmax) of apremilast. PK parameters were calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Time to maximum observed plasma concentration obtained directly from the observed concentration versus time data. PK parameters were calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Area under the plasma concentration-time curve from time zero to the 12 hours post dose was calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Area under the plasma concentration-time curve from time zero to the last quantifiable time point and was calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Apparent total plasma clearance (CL/F) of apremilast was calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Apparent total volume of distribution when dosed orally, based on study-state (Vss/F) or in the terminal phase (Vz/F). Pharmacokinetic parameters were calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Terminal-phase elimination half-life (t ½). PK parameters were calculated using non-compartmental methods, plasma concentrations and actual blood sampling times from the intensive sampling schedule.

Clinical remission was defined as a total Mayo score ≤ 2 points, with no individual subscore exceeding 1 point. The TMS is an instrument designed to measure disease activity of UC. The Mayo score ranges from 0 to 12 points. It consists of 4 subscores, each graded from 0 to 3 with higher scores indicating more severe disease. * Stool Frequency Subscore (SFS) * Rectal Bleeding Subscore (RBS) * Endoscopy Subscore * Physician's Global Assessment (PGA). Two-sided 95% confidence intervals (CI) for the within-group percentages are based on the Wilson score method.

EASI is a validated composite scoring system integrating the proportion of the body region (area) involved and the intensity of key signs of atopic dermatitis (AD). A representative lesion is selected for each of the four body regions for assessing the intensity of each of the four signs (erythema, induration /papulation, excoriation, and lichenification). Symptoms (eg, pruritus) and secondary signs (eg, xerosis, scaling) are excluded from the assessment. The total EASI score ranges from 0 to 72. A higher score indicated worse disease status, and a negative change from baseline indicated improvement.

PASI-75 response is the percentage of participants who achieved at least a 75% reduction (improvement) from baseline in PASI score at Week 16. The improvement in PASI score was used as a measure of efficacy. The PASI was a measure of psoriatic disease severity taking into account qualitative lesion characteristics (erythema, thickness and scaling) and degree of skin surface area involvement on defined anatomical regions. PASI scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). The PASI score was set to missing if any severity score or degree of involvement was missing.

The number of oral ulcers were counted at each visit and at the end of the treatment period (starting point was at baseline).

PASI-75 response is the percentage of participants who achieved at least a 75% reduction (improvement) from baseline in PASI score at Week 16. The improvement in PASI score was used as a measure of efficacy. The PASI was a measure of psoriatic disease severity taking into account qualitative lesion characteristics (erythema, thickness and scaling) and degree of skin surface area involvement on defined anatomical regions. PASI scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement).

TEAE = any AE occurring or worsening on or after the first treatment with any study drug. Related = suspected by investigator to be related to study treatment. National Cancer Institute \[NCI\] Common Toxicity Criteria for Adverse Events \[CTCAE\], Version 3.0, grades: 1 = mild, 2 = moderate, 3 = severe, 4 = life threatening, 5 = death. Adverse event (AE) = any noxious, unintended, or untoward medical occurrence occurring at any dose that may appear or worsen in a participant during the course of a study, including new intercurrent illness, worsening concomitant illness, injury, or any concomitant impairment of participant's health, including laboratory test values, regardless of etiology. Serious adverse event (SAE) = any AE which results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect; constitutes an important medical event.

TEAE = any AE occurring or worsening on or after the first treatment with any study drug. Related = suspected by investigator to be related to study treatment. National Cancer Institute \[NCI\] Common Toxicity Criteria for Adverse Events \[CTCAE\], Version 3.0, grades: 1 = mild, 2 = moderate, 3 = severe, 4 = life threatening, 5 = death. Adverse event (AE) = any noxious, unintended, or untoward medical occurrence occurring at any dose that may appear or worsen in a participant during the course of a study, including new intercurrent illness, worsening concomitant illness, injury, or any concomitant impairment of participant's health, including laboratory test values, regardless of etiology. Serious adverse event (SAE) = any AE which: results in death; is life-threatening; requires inpatient hospitalization or prolongation of existing hospitalization; results in persistent or significant disability/incapacity; is a congenital anomaly/birth defect; constitutes an important medical event.

A modified American College of Rheumatology 20% (ACR 20) response was defined as a participant who met the following 3 criteria for improvement from Baseline: • ≥ 20% improvement in 78 tender joint count (includes 10 additional joints often involved in psoriatic arthritis: the first carpometacarpal \[CMC\] and the distal interphalangeal \[DIP\] joints of the fingers); • ≥ 20% improvement in 76 swollen joint count; and • ≥ 20% improvement in at least 3 of the 5 following parameters: ◦ Patient's assessment of pain (measured on a 100 mm visual analog scale \[VAS\]); ◦ Patient's global assessment of disease activity (measured on a 100 mm VAS); ◦ Physician's global assessment of disease activity (measured on a 100 mm VAS); ◦ Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index \[HAQ-DI\]); ◦ C-reactive protein. Participants with no post-baseline ACR scores were considered non-responders.

Concentrations of apremilast in plasma were measured using a validated liquid chromatography tandem mass spectrometry assay.

Area under the plasma concentration-time curve during a dosage interval (tau) at steady state, where tau is 12 hours.

Ratio of accumulation calculated as Day 14 AUC0-τ / Day 1 AUC0-τ

Concentrations of apremilast in plasma were measured using a validated liquid chromatography tandem mass spectrometry assay. AUC from time zero to the last measured time point was calculated by the linear trapezoidal method.

Concentrations of apremilast in plasma were measured using a validated liquid chromatography tandem mass spectrometry assay. AUC from time zero to infinity was calculated as (AUC0-t + Ct/λz), where Ct is the last quantifiable concentration, and λz is the apparent terminal rate constant.

Concentrations of apremilast in plasma were measured using a validated liquid chromatography tandem mass spectrometry assay.

Lag time is the delay between the time of administration and start of absorption.

Relative bioavailability of the oral suspension formulation compared to the tablet formulation, calculated as (AUC0-∞/Dose\[oral suspension\]) / (AUC0-∞/Dose\[tablet\]) \* 100%.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL. AUC0-t was calculated using the linear trapezoidal method when concentrations were increasing and the logarithmic trapezoidal method when concentrations were decreasing.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL. AUC0-t was calculated using the linear trapezoidal method when concentrations were increasing and the logarithmic trapezoidal method when concentrations were decreasing.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL.

The lower limit of quantitation for apremilast plasma concentrations was 1.0 ng/mL.

Plasma concentrations of apremilast were determined by means of a validated, sensitive, and specific high performance liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay.

Plasma concentrations of apremilast were determined by means of a validated, sensitive, and specific high performance liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay.

Plasma concentrations of apremilast were determined by means of a validated, sensitive, and specific high performance liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay.

Plasma concentrations of apremilast were determined by means of a validated, sensitive, and specific high performance liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay.

Plasma concentrations of apremilast were determined by means of a validated, sensitive, and specific high performance liquid chromatography/tandem mass spectrometric (LC-MS/MS) assay.