PALACE 2: Efficacy and Safety Study of Apremilast to Treat Active Psoriatic Arthritis

Change From Baseline in Health Assessment Questionnaire- Disability Index (HAQ-DI) at Week 24

The Health Assessment Questionnaire - Disability Index is a patient-reported questionnaire consisting of 20 questions referring to eight domains: dressing/grooming, arising, eating, walking, hygiene, reach, grip, and usual activities. Participants assessed their ability to do each task over the past week using the following response categories: without any difficulty (0); with some difficulty (1); with much difficulty (2); and unable to do (3). Scores on each task are summed and averaged to provide an overall score ranging from 0 to 3, where zero represents no disability and three very severe, high-dependency disability. Negative mean changes from Baseline in the overall score indicate improvement in functional ability.

Time frame: Baseline and Week 24

Change From Baseline in 36-item Short Form Health Survey (SF-36) Physical Functioning Domain at Week 16

The Medical Outcome Study Short Form 36-Item Health Survey, Version 2 (SF-36) is a self-administered instrument that measures the impact of disease on overall quality of life and consists of 36 questions in eight domains (physical function, pain, general and mental health, vitality, social function, physical and emotional health). Norm-based scores were used in analyses, calibrated so that 50 is the average score and the standard deviation equals 10. Higher scores indicate a higher level of functioning. The physical functioning domain assesses limitations in physical activities because of health problems. A positive change from Baseline score indicates an improvement.

Time frame: Baseline and Week 16

Percentage of Participants With a Modified Psoriatic Arthritis Response Criteria (PsARC) Response at Week 16

Modified PsARC response is defined as improvement in at least 2 of the 4 measures, at least one of which must be tender joint count or swollen joint count, and no worsening in any of the 4 measures: - 78 tender joint count, - 76 swollen joint count, - Patient global assessment of disease activity, measured on a 100 mm visual Analog scale (VAS), where 0 mm = lowest disease activity and 100 mm = highest; - Physician global assessment of disease activity, measured on a 100 mm VAS, where 0 mm = lowest disease activity and 100 mm = highest. Improvement or worsening in joint counts is defined as decrease or increase, respectively, from baseline by ≥ 30%, and improvement or worsening in global assessments is defined as decrease or increase, respectively, from baseline by ≥ 20 mm VAS.

Time frame: Baseline and Week 16

Change From Baseline in Patient's Assessment of Pain at Week 16

The participant was asked to place a vertical line on a 100-mm visual analog scale on which the left-hand boundary (score = 0 mm) represents "no pain," and the right-hand boundary (score = 100 mm) represents "pain as severe as can be imagined." The distance from the mark to the left-hand boundary was recorded in millimeters.

Time frame: Baseline and Week 16

Change From Baseline in Maastricht Ankylosing Spondylitis Entheses Score (MASES) at Week 16

The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Baseline and Week 16

Change From Baseline in Dactylitis Severity Score at Week 16

Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet will be rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Baseline and Week 16

Change From Baseline in Clinical Disease Activity Index (CDAI) at Week 16

The Clinical Disease Activity Index (CDAI) is a composite index that is calculated as the sum of the: - 28 tender joint count (TJC), - 28 swollen joint count (SJC), - Patient's Global Assessment of Disease Activity measured on a 10 cm visual analog scale (VAS), where 0 cm = lowest disease activity and 10 cm = highest; - Physician's Global Assessment of Disease Activity -measured on a 10 cm VAS, where 0 cm = lowest disease activity and 10 cm = highest. The CDAI score ranges from 0-76 where lower scores indicate less disease activity. The following thresholds of disease activity have been defined for the CDAI: Remission: ≤ 2.8 Low Disease Activity: \> 2.8 and ≤ 10 Moderate Disease Activity: \> 10 and ≤ 22 High Disease Activity: \> 22.

Time frame: Baseline and Week 16

Change From Baseline in the Disease Activity Score (DAS28) at Week 16

The DAS28 measures the severity of disease at a specific time and is derived from the following variables: - 28 tender joint count - 28 swollen joint count, which do not include the distal interphalangeal (DIP) joints, the hip joint, or the joints below the knee; - C-reactive protein (CRP) - Patient's global assessment of disease activity. DAS28(CRP) scores range from 0 to approximately 10, with the upper bound dependent on the highest possible level of CRP. A DAS28 score higher than 5.1 indicates high disease activity, a DAS28 score less than 3.2 indicates low disease activity, and a DAS28 score less than 2.6 indicates clinical remission.

Time frame: Baseline and Week 16

Change From Baseline in the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) Score at Week 16

The FACIT-Fatigue scale is a 13-item self-administered questionnaire that assesses both the physical and functional consequences of fatigue. Each question is answered on a 5-point scale, where 0 means "not at all," and 4 means "very much." The FACIT-Fatigue scale score ranges from 0 to 52, with higher scores denoting lower levels of fatigue. A positive change from baseline score indicates an improvement.

Time frame: Baseline and Week 16

Change From Baseline in 36-item Short Form Health Survey (SF-36) Physical Functioning Domain at Week 24

The Medical Outcome Study Short Form 36-Item Health Survey, Version 2 (SF-36) is a self-administered instrument that measures the impact of disease on overall quality of life and consists of 36 questions in eight domains (physical function, pain, general and mental health, vitality, social function, physical and emotional health). Norm-based scores were used in analyses, calibrated so that 50 is the average score and the standard deviation equals 10. Higher scores indicate a higher level of functioning. The physical functioning domain assesses limitations in physical activities because of health problems. A positive change from Baseline score indicates an improvement.

Time frame: Baseline and Week 24

Percentage of Participants With a Modified Psoriatic Arthritis Response Criteria (PsARC) Response at Week 24

Modified PsARC response is defined as improvement in at least 2 of the 4 measures, at least one of which must be tender joint count or swollen joint count, and no worsening in any of the 4 measures: • 78 tender joint count, • 76 swollen joint count, • Patient global assessment of disease activity, measured on a 100 mm visual Analog scale (VAS), where 0 mm = lowest disease activity and 100 mm = highest; • Physician global assessment of disease activity, measured on a 100 mm VAS, where 0 mm = lowest disease activity and 100 mm = highest. Improvement or worsening in joint counts is defined as decrease or increase, respectively, from baseline by ≥ 30%, and improvement or worsening in global assessments is defined as decrease or increase, respectively, from baseline by ≥ 20 mm VAS.

Time frame: Baseline and Week 24

Change From Baseline in Patient's Assessment of Pain at Week 24

The participant was asked to place a vertical line on a 100-mm visual analog scale on which the left-hand boundary (score = 0 mm) represents "no pain," and the right-hand boundary (score = 100 mm) represents "pain as severe as can be imagined." The distance from the mark to the left-hand boundary was recorded in millimeters.

Time frame: Baseline and Week 24

Change From Baseline in Maastricht Ankylosing Spondylitis Entheses Score (MASES) at Week 24

The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Baseline and Week 24

Change From Baseline in Dactylitis Severity Score at Week 24

Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet will be rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Baseline and Week 24

Change From Baseline in Clinical Disease Activity Index (CDAI) at Week 24

The Clinical Disease Activity Index (CDAI) is a composite index that is calculated as the sum of the: • 28 tender joint count (TJC), • 28 swollen joint count (SJC), • Patient's Global Assessment of Disease Activity measured on a 10 cm visual analog scale (VAS), where 0 cm = lowest disease activity and 10 cm = highest; • Physician's Global Assessment of Disease Activity -measured on a 10 cm VAS, where 0 cm = lowest disease activity and 10 cm = highest. The CDAI score ranges from 0-76 where lower scores indicate less disease activity. The following thresholds of disease activity have been defined for the CDAI: Remission: ≤ 2.8; Low Disease Activity: \> 2.8 and ≤ 10; Moderate Disease Activity: \> 10 and ≤ 22; High Disease Activity: \> 22.

Time frame: Baseline and Week 24

Change From Baseline in the Disease Activity Score (DAS28) at Week 24

The DAS28 measures the severity of disease at a specific time and is derived from the following variables: • 28 tender joint count • 28 swollen joint count, which do not include the DIP joints, the hip joint, or the joints below the knee; • C-reactive protein (CRP) • Patient's global assessment of disease activity. DAS28(CRP) scores range from 0 to approximately 10, with the upper bound dependent on the highest possible level of CRP. A DAS28 score higher than 5.1 indicates high disease activity, a DAS28 score less than 3.2 indicates low disease activity, and a DAS28 score less than 2.6 indicates clinical remission.

Time frame: Baseline and Week 24

Change From Baseline in the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) Score at Week 24

The FACIT-Fatigue scale is a 13-item self-administered questionnaire that assesses both the physical and functional consequences of fatigue. Each question is answered on a 5-point scale, where 0 means "not at all," and 4 means "very much." The FACIT-Fatigue scale score ranges from 0 to 52, with higher scores denoting lower levels of fatigue. A positive change from baseline score indicates an improvement.

Time frame: Baseline and Week 24

Percentage of Participants With MASES Improvement ≥ 20% at Week 16

Percentage of participants with pre-existing enthesopathy whose MASES improved by ≥ 20% from Baseline after 16 weeks of treatment. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Baseline and Week 16

Percentage of Participants With Dactylitis Improvement ≥ 1 Point at Week 16

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improved by ≥ 1 after 16 weeks of treatment. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Baseline and Week 16

Percentage of Participants With Good or Moderate European League Against Rheumatism (EULAR) Response at Week 16

A EULAR response reflects an improvement in disease activity and an attainment of a lower degree of disease activity based on the DAS-28 score. A Good Response is defined as an improvement (decrease) in the DAS28 of more than 1.2 compared with Baseline and attainment of a DAS28 score less than or equal to 3.2. A Moderate Response is defined as either: • an improvement (decrease) in the DAS28 of greater than 0.6 and less than or equal to 1.2 and attainment of a DAS28 score of less than or equal to 5.1 or, • an improvement (decrease) in the DAS28 of more than 1.2 and attainment of a DAS28 score of greater than 3.2.

Time frame: Baseline and Week 16

Percentage of Participants With MASES Improvement ≥ 20% at Week 24

Percentage of participants with pre-existing enthesopathy whose MASES improved by ≥ 20% from Baseline after 24 weeks of treatment. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Baseline and Week 24

Percentage of Participants With Dactylitis Improvement ≥ 1 Point at Week 24

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improved by ≥ 1 after 24 weeks of treatment. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Baseline and Week 24

Percentage of Participants With Good or Moderate EULAR Response at Week 24

EULAR response reflects an improvement in disease activity and an attainment of a lower degree of disease activity based on the DAS-28 score. A Good Response is defined as an improvement (decrease) in the DAS28 of more than 1.2 compared with Baseline and attainment of a DAS28 score less than or equal to 3.2. A Moderate Response is defined as either: • an improvement (decrease) in the DAS28 of greater than 0.6 and less than or equal to 1.2 and attainment of a DAS28 score of less than or equal to 5.1 or, • an improvement (decrease) in the DAS28 of more than 1.2 and attainment of a DAS28 score of greater than 3.2.

Time frame: Baseline and Week 24

Percentage of Participants With a ACR 50 Response at Week 16

Percentage of participants with an American College of Rheumatology 50% (ACR50) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 50% improvement in 78 tender joint count; • ≥ 50% improvement in 76 swollen joint count; and • ≥ 50% improvement in at least 3 of the 5 following parameters: o Patient's assessment of pain (measured on a 100 mm visual analog scale \[VAS\]); o Patient's global assessment of disease activity (measured on a 100 mm VAS); o Physician's global assessment of disease activity (measured on a 100 mm VAS); o Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index (HAQ-DI)); o C-Reactive Protein.

Time frame: Baseline and Week 16

Percentage of Participants With an ACR 70 Response at Week 16

Percentage of participants with an American College of Rheumatology 70% (ACR70) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 70% improvement in 78 tender joint count; • ≥ 70% improvement in 76 swollen joint count; and • ≥ 70% improvement in at least 3 of the 5 following parameters: o Patient's assessment of pain (measured on a 100 mm visual analog scale \[VAS\]); o Patient's global assessment of disease activity (measured on a 100 mm VAS); o Physician's global assessment of disease activity (measured on a 100 mm VAS); o Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index (HAQ-DI)); o C-Reactive Protein.

Time frame: Baseline and Week 16

Percentage of Participants With an ACR 50 Response at Week 24

Percentage of participants with an American College of Rheumatology 50% (ACR50) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 50% improvement in 78 tender joint count; • ≥ 50% improvement in 76 swollen joint count; and • ≥ 50% improvement in at least 3 of the 5 following parameters: o Patient's assessment of pain (measured on a 100 mm visual analog scale \[VAS\]); o Patient's global assessment of disease activity (measured on a 100 mm VAS); o Physician's global assessment of disease activity (measured on a 100 mm VAS); o Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index (HAQ-DI)); o C-Reactive Protein.

Time frame: Baseline and Week 24

Percentage of Participants With a ACR 70 Response at Week 24

Percentage of participants with an American College of Rheumatology 70% (ACR70) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 70% improvement in 78 tender joint count; • ≥ 70% improvement in 76 swollen joint count; and • ≥ 70% 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.

Time frame: Baseline and Week 24

Percentage of Participants Achieving a MASES Score of Zero at Week 16

Percentage of participants with pre-existing enthesopathy whose MASES improves to 0 after 16 weeks of treatment. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Week 16

Percentage of Participants Achieving a Dactylitis Score of Zero at Week 16

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improves to zero after 16 weeks of treatment. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Week 16

Percentage of Participants Achieving a MASES Score of Zero at Week 24

Percentage of participants with pre-existing enthesopathy whose MASES improves to 0 after 24 weeks of treatment. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Week 24

Percentage of Participants Achieving a Dactylitis Score of Zero at Week 24

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improves to zero after 24 weeks of treatment. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Week 24

Percentage of Participants With a ACR 20 Response at Week 52

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 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. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Change From Baseline in Health Assessment Questionnaire - Disability Index (HAQ-DI) at Week 52

The Health Assessment Questionnaire - Disability Index is a patient-reported questionnaire consisting of 20 questions referring to eight domains: dressing/grooming, arising, eating, walking, hygiene, reach, grip, and usual activities. Participants assessed their ability to do each task over the past week using the following response categories: without any difficulty (0); with some difficulty (1); with much difficulty (2); and unable to do (3). Scores on each task are summed and averaged to provide an overall score ranging from 0 to 3, where zero represents no disability and three very severe, high-dependency disability. Negative mean changes from Baseline in the overall score indicate improvement in functional ability.

Time frame: Baseline and Week 52

Change From Baseline in the SF-36 Physical Functioning Scale Score at Week 52

The Medical Outcome Study Short Form 36-Item Health Survey, Version 2 (SF-36) is a self-administered instrument that measures the impact of disease on overall quality of life and consists of 36 questions in eight domains (physical function, pain, general and mental health, vitality, social function, physical and emotional health). Norm-based scores were used in analyses, calibrated so that 50 is the average score and the standard deviation equals 10. Higher scores indicate a higher level of functioning. The physical functioning domain assesses limitations in physical activities because of health problems. A positive change from Baseline score indicates an improvement.

Time frame: Baseline and Week 52

Percentage of Participants With a Modified PsARC Response at Week 52

Modified PsARC response is defined as improvement in at least 2 of the 4 measures, at least one of which must be tender joint count or swollen joint count, and no worsening in any of the 4 measures: • 78 tender joint count, • 76 swollen joint count, • Patient global assessment of disease activity, measured on a 100 mm visual Analog scale (VAS), where 0 mm = lowest disease activity and 100 mm = highest; • Physician global assessment of disease activity, measured on a 100 mm VAS, where 0 mm = lowest disease activity and 100 mm = highest. Improvement or worsening in joint counts is defined as decrease or increase, respectively, from baseline by ≥ 30%, and improvement or worsening in global assessments is defined as decrease or increase, respectively, from baseline by ≥ 20 mm VAS. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Change From Baseline in the Patient Assessment of Pain at Week 52

The participant was asked to place a vertical line on a 100-mm visual analog scale on which the left-hand boundary (score = 0 mm) represents "no pain," and the right-hand boundary (score = 100 mm) represents "pain as severe as can be imagined." The distance from the mark to the left-hand boundary was recorded in millimeters.

Time frame: Baseline and Week 52

Change From Baseline in Maastricht Ankylosing Spondylitis Entheses Score (MASES) at Week 52

The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses.

Time frame: Baseline and Week 52

Change From Baseline in the Dactylitis Severity Score at Week 52

Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet will be rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present.

Time frame: Baseline and Week 52

Change From Baseline in the CDAI Score at Week 52

The Clinical Disease Activity Index (CDAI) is a composite index that is calculated as the sum of the: • 28 tender joint count (TJC), • 28 swollen joint count (SJC), • Patient's Global Assessment of Disease Activity measured on a 10 cm visual analog scale (VAS), where 0 cm = lowest disease activity and 10 cm = highest; • Physician's Global Assessment of Disease Activity -measured on a 10 cm VAS, where 0 cm = lowest disease activity and 10 cm = highest. The CDAI score ranges from 0-76 where lower scores indicate less disease activity. The following thresholds of disease activity have been defined for the CDAI: Remission: ≤ 2.8 Low Disease Activity: \> 2.8 and ≤ 10 Moderate Disease Activity: \> 10 and ≤ 22 High Disease Activity: \> 22.

Time frame: Baseline and Week 52

Change From Baseline in the DAS28 at Week 52

The DAS28 measures the severity of disease at a specific time and is derived from the following variables: • 28 tender joint count • 28 swollen joint count, which do not include the DIP joints, the hip joint, or the joints below the knee; • C-reactive protein (CRP) • Patient's global assessment of disease activity. DAS28(CRP) scores range from 0 to approximately 10, with the upper bound dependent on the highest possible level of CRP. A DAS28 score higher than 5.1 indicates high disease activity, a DAS28 score less than 3.2 indicates low disease activity, and a DAS28 score less than 2.6 indicates clinical remission.

Time frame: Baseline and Week 52

Change From Baseline in the FACIT-Fatigue Scale Score at Week 52

The FACIT-Fatigue scale is a 13-item self-administered questionnaire that assesses both the physical and functional consequences of fatigue. Each question is answered on a 5-point scale, where 0 means "not at all," and 4 means "very much." The FACIT-Fatigue scale score ranges from 0 to 52, with higher scores denoting lower levels of fatigue. A positive change from baseline score indicates an improvement.

Time frame: Baseline and Week 52

Percentage of Participants With MASES Improvement ≥ 20% at Week 52

Percentage of participants with pre-existing enthesopathy whose MASES improved by ≥ 20% from Baseline after 52 weeks. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Percentage of Participants With Dactylitis Improvement ≥ 1 Point at Week 52

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improved by ≥ 1 after 52 weeks. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Percentage of Participants Achieving Good or Moderate EULAR Response at Week 52

A EULAR response reflects an improvement in disease activity and an attainment of a lower degree of disease activity based on the DAS-28 score. A Good Response is defined as an improvement (decrease) in the DAS28 of more than 1.2 compared with Baseline and attainment of a DAS28 score less than or equal to 3.2. A Moderate Response is defined as either: • an improvement (decrease) in the DAS28 of greater than 0.6 and less than or equal to 1.2 and attainment of a DAS28 score of less than or equal to 5.1 or, • an improvement (decrease) in the DAS28 of more than 1.2 and attainment of a DAS28 score of greater than 3.2.

Time frame: Baseline and Week 52

Percentage of Participants With an ACR 50 Response at Week 52

Percentage of participants with an American College of Rheumatology 50% (ACR50) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 50% improvement in 78 tender joint count; • ≥ 50% improvement in 76 swollen joint count; and • ≥ 50% 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. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Percentage of Participants With an ACR 70 Response at Week 52

Percentage of participants with an American College of Rheumatology 70% (ACR70) response. A participant was a responder if the following 3 criteria for improvement from Baseline were met: • ≥ 70% improvement in 78 tender joint count; • ≥ 70% improvement in 76 swollen joint count; and • ≥ 70% 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. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Baseline and Week 52

Percentage of Participants Achieving a MASES Score of Zero at Week 52

Percentage of participants with pre-existing enthesopathy whose MASES improves to 0 after 24 weeks. The Maastricht Ankylosing Spondylitis Enthesitis Score quantitates inflammation of the entheses (enthesitis) by assessing pain at the following entheses (sites where tendons or ligaments insert into the bone): 1st costochondral joints left/right; 7th costochondral joints left/right; posterior superior iliac spine left/right; anterior superior iliac spine left/right; iliac crest left/right; 5th lumbar spinous process; and the proximal insertion of the Archilles tendon left/right. The MASES, ranging from 0 to 13, is the number of painful entheses out of 13 entheses. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Week 52

Percentage of Participants Achieving a Dactylitis Score of Zero at Week 52

Percentage of participants with pre-existing dactylitis whose dactylitis severity score improves to zero after 52 weeks. Dactylitis is characterized by swelling of the entire finger or toe. Each digit on the hands and feet was rated as zero for no dactylitis or 1 for dactylitis present. The dactylitis score is the sum of the individual scores for each digit. The dactylitis severity score, ranging from 0 to 20, is the number of digits on the hands and feet with dactylitis present. Two-sided 95% confidence interval is based on the Clopper-Pearson method.

Time frame: Week 52

Number of Participants With Treatment Emergent Adverse Events During the Placebo-Controlled Phase

A treatment emergent adverse event (TEAE) is an AE with a start date on or after the date of the first dose of Investigational Product (IP). The severity of each adverse event (AE) and serious AE (SAE) was assessed by the investigator and graded based on a scale from Mild - mild symptoms to Severe AEs (non-serious or serious). A serious adverse event (SAE) is any AE which: * Resulted in death * Was life-threatening * Required inpatient hospitalization or prolongation of existing hospitalization * Resulted in persistent or significant disability/incapacity * Was a congenital anomaly/birth defect * Constituted an important medical event

Time frame: Week 0 to Week 16 for placebo participants who entered EE at Week 16 and up to Week 24 for all other participants (placebo participants who remained on placebo through week 24 and participants randomized to the APR 20 mg BID or APR 30 mg BID)

Number of Participants With TEAEs During the Apremilast-Exposure Period

A treatment emergent adverse event (TEAE) is an AE with a start date on or after the date of the first dose of Investigational Product (IP). The severity of each adverse event (AE) and serious AE (SAE) was assessed by the investigator and graded based on a scale from Mild - mild symptoms to Severe AEs (non-serious or serious). A serious adverse event (SAE) is any AE which: * Resulted in death * Was life-threatening * Required inpatient hospitalization or prolongation of existing hospitalization * Resulted in persistent or significant disability/incapacity * Was a congenital anomaly/birth defect * Constituted an important medical event

Time frame: Week 0 to week 260; overall median duration of exposure to apremilast 20 mg and 30 mg BID was 198 weeks