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

Intent to Treat (ITT) = all randomized participants with at least one oral ulcer evaluation (including the baseline visit). A Last Observation Carried Forward (LOCF) approach was applied for participants terminated early. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

A 100-mm VAS pain scale for oral ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

The percentage of participants who were genital ulcer-free (complete response: free from active genital ulcers)

Intent to Treat (ITT) = all randomized participants with at least one genital ulcer at baseline. A Last Observation Carried Forward (LOCF) approach was applied for participants terminated early. If a participant had no post-baseline genital ulcer assessment, the baseline value was carried forward for calculation.

A 100-mm VAS pain scale for genital ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

Not analyzed due to low numbers of genital ulcers; not considered meaningful.

Area under curve (AUC^85) from Day 1 to Day 85 for the number of oral ulcers per day was determined using the trapezoidal rule and divided by the days between the date of the last observation and baseline. The AUC was determined using the LOCF approach to impute missing values.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

Area under curve (AUC^85) from Day 1 to Day 85 for the number of genital ulcers per day was not analyzed.

No population analyzed due to small number of participants with genital ulcers; not considered meaningful.

Area under curve (AUC) from Day 1 to Day 85 (AUC^85) for the number of oral plus genital ulcers per day was determined using the trapezoidal rule and divided by the days between the date of the last observation and baseline. The AUC was determined using the LOCF approach to impute missing values.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

Sum of the number oral ulcers, genital ulcers or oral plus genital ulcers at Day 85

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

Comparison of the percentage of participants who were oral ulcer-free (complete response: free from active oral ulcers), or whose oral ulcers were reduced by ≥ 50%, (partial response) between the apremilast-treated and the placebo-treated groups. In this case, partial response also includes complete response.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

The Behçet's Disease Current Activity Index consists of three component scores, a participant's perception of disease activity, a clinician's overall perception of disease activity and a Behçet's Disease Current Activity Index Score. The score ranges from 0 to 12. A higher score indicates higher level of disease activity (worsening) and a negative change from baseline indicates improvement.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

A Treatment Emergent Adverse Event (TEAE) was defined as any AE occurring or worsening on or after the first treatment of any study drug, and within 28 days after the last dose of the last study drug. A treatment related toxicity was considered by the investigator to be not suspected or suspected. Severity grades according to Common Terminology Criteria for Adverse Events v3.0 (CTCAE) on a 1-5 scale: Grade 1= Mild AE, Grade 2= Moderate AE, Grade 3= Severe AE, Grade 4= Life-threatening or disabling AE, Grade 5=Death related to AE.

Safety Population defined as all participants who were randomized and received at least 1 dose of Investigational Product.

A flare was defined as the development of new manifestations of BD or worsening of existing disease, meeting the following criteria:

1. Organ involvement: any major organ involvement (eg, central nervous system, gastrointestinal tract);
2. Oral/genital ulcers: ≥ 100% increase in the number of oral or genital ulcers from Day 1 or a minimum increase of 3 in the number of oral or genital ulcers, whichever is greater;
3. Arthritis: ≥ 50% increase in the number of swollen joints, or a minimum increase of 3 swollen joints, whichever is greater;
4. Skin lesions (non-oral/genital ulcers): ≥ 50% increase in the total score of the Physician's Global Assessment of Skin Lesions, or a minimum increase of 2 in the total score of the Physician's Global Assessment of Skin Lesions, whichever is greater'
5. New onset or worsening of existing Behçet Disease-related inflammatory eye disease requiring initiation of immunosuppressive therapy (uveitis).

Safety population included all participants who were randomized and received at least 1 dose of Investigational Product.

The number of oral ulcers were counted at Day 169 in reference to the participants' first day of active treatment (Day 1 or Day 85).

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

A 100-mm VAS pain scale for oral ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

The percentage of participants who were genital ulcer-free (complete response: free from active genital ulcers)

Intent to Treat (ITT) = all randomized participants with at least one genital ulcer at baseline visit. A Last Observation Carried Forward (LOCF) approach was applied for participants terminated early. If a participant had no post-baseline genital ulcer assessment, the baseline value was carried forward for calculation.

A 100-mm VAS pain scale for genital ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

Not analyzed due to low numbers of genital ulcers; not considered meaningful.

The Behçet's Disease Current Activity Index consists of three component scores, a participant's perception of disease activity, a clinician's overall perception of disease activity and a Behçet's Disease Current Activity Index Score. The score ranges from 0 to 12. A higher score indicates higher level of disease activity (worsening) and a negative change from baseline indicates improvement.

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

A flare was defined as the development of new manifestations of BD or worsening of existing disease, meeting the following criteria:

1. Organ involvement: any major organ involvement (eg, central nervous system, gastrointestinal tract);
2. Oral/genital ulcers: ≥ 100% increase in the number of oral or genital ulcers from Day 1 or a minimum increase of 3 in the number of oral or genital ulcers, whichever is greater;
3. Arthritis: ≥ 50% increase in the number of swollen joints, or a minimum increase of 3 swollen joints, whichever is greater;
4. Skin lesions (non-oral/genital ulcers): ≥ 50% increase in the total score of the Physician's Global Assessment of Skin Lesions, or a minimum increase of 2 in the total score of the Physician's Global Assessment of Skin Lesions, whichever is greater;
5. New onset or worsening of existing Behçet Disease-related inflammatory eye disease requiring initiation of immunosuppressive therapy (uveitis).

The ITT population included all randomized participants with at least one oral ulcer evaluation (including the baseline evaluation). A LOCF approach was applied for participants terminated early from the study. If a participant had no post-baseline oral ulcer assessment, the baseline value was carried forward for calculation.

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

Includes participants who entered the Observational Follow-up Phase from either the Treatment Phase or the Extension Phase

A 100-mm VAS pain scale for oral ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

Includes participants who entered the Observational Follow-up Phase from either the Treatment Phase or the Extension Phase.

The percentage of participants who were genital ulcer-free (complete response: free from active genital ulcers)

Intent to Treat (ITT) = all randomized participants with at least one genital ulcer at baseline. A Last Observation Carried Forward (LOCF) approach was applied for participants terminated early. If a participant had no post-baseline genital ulcer assessment, the baseline value was carried forward for calculation.

A 100-mm VAS pain scale for genital ulcers was completed by the participant at timepoints specified in the protocol. Each 100-mm VAS was presented to the participant on a single sheet of bond paper. The participant was asked to draw a single line perpendicular to the VAS line at the point that represented the severity of their pain during the previous week, with 0 mm (the left-hand end of the scale) representing no pain and 100 mm (the right-hand end of the scale) representing the worst pain imaginable. The distance of the perpendicular line from the left-hand end of the scale was measured by ruler and recorded. When responding to a VAS item, participants specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.

Not analyzed due to low numbers of genital ulcers; not considered meaningful.

The Behçet's Disease Current Activity Index consists of three component scores, a participant's perception of disease activity, a clinician's overall perception of disease activity and a Behçet's Disease Current Activity Index Score. The score ranges from 0 to 12. A higher score indicates higher level of disease activity (worsening) and a negative change from baseline indicates improvement.

Includes participants who entered the Observational Follow-up Phase from either the Treatment Phase or the Extension Phase

A Treatment Emergent Adverse Event (TEAE) is as any AE occurring or worsening on or after the first treatment of any study drug, and within 28 days after the last dose of the last study drug. A treatment related toxicity was considered by the investigator to be not suspected or suspected. Severity grades according to Common Terminology Criteria for Adverse Events v3.0 (CTCAE) on a 1-5 scale: Grade 1= Mild AE, Grade 2= Moderate AE, Grade 3= Severe AE, Grade 4= Life-threatening or disabling AE, Grade 5=Death related to AE.

Safety analyses for the apremilast-exposure period was based on the apremilast participants as treated (AAT) Population, and included those who were randomized (at the randomization visit) or switched (at the Day 85 visit) to apremilast 30 mg BID, and received at least one dose of apremilast after the initial randomization or switch to 30 mg BID.