Eligibility Details:  
        Inclusion Criteria:
        Subjects must satisfy the following criteria to be enrolled in the study:
          1. Males or females, aged ≥ 18 years at time of consent
          2. For all regions, the local Regulatory Label for treatment with apremilast must be
             followed.
          3. Must understand and voluntarily sign an informed consent document prior to any study
             related assessments/procedures being conducted
          4. Able to adhere to the study visit schedule and other protocol requirements
          5. Have a documented diagnosis of PsA of ≥ 3 months AND ≤ 5 years in duration, meeting
             the CASPAR criteria for PsA at the time of Screening Visit
          6. Have ≥ 3 swollen AND ≥ 3 tender joints, with hand involvement (defined as ≥ 1 swollen
             joint or dactylitis [each clinically active joint of a dactylitic digit is counted as
             one joint]).
          7. Have at least 1 active enthesitis site (one of the SPARCC or LEI sites)
          8. Must not have been treated previously with a TNF blocker or other biologic drug for
             PsA treatment
          9. Must not have been treated with more than 2 csDMARDs
         10. Subjects taking csDMARDs, with the exception of MTX, cyclosporine, or LEF, do not
             require a washout period. However, they must discontinue the csDMARD treatment at
             least one day prior to their Baseline Visit (ie, Visit 2, Day 1)
         11. Subjects who have been previously treated with MTX for < 6 months and who are not on
             stable doses for at least 3 months will require a 28-day washout prior to the Baseline
             Visit (ie, Visit 2, Day 1) to participate in the study
         12. Subjects who have been previously treated with LEF will require a 12-week washout
             prior to the Baseline Visit (ie, Visit 2, Day 1), or treatment with cholestyramine,
             per LEF prescribing label (ie, 8 g cholestyramine 3 times daily for 11 days)
         13. Subjects who have been previously treated with cyclosporine will require a 28-day
             washout prior to the Baseline Visit (ie, Visit 2, Day 1) to participate in the study
         14. If taking MTX (≤ 25 mg/week), continuity of treatment will be allowed if duration of
             treatment is ≥ 6 months and on a stable dose for at least 3 months prior to the
             Baseline Visit (ie, Visit 2, Day 1)
         15. If taking oral glucocorticoids, must be on a stable dose of prednisone ≤ 10 mg/day or
             equivalent for at least 4 weeks prior to the Baseline Visit (ie, Visit 2, Day 1)
         16. If taking NSAIDs or narcotic analgesics, must be on stable dose for at least 4 weeks
             prior to Baseline Visit (ie, Visit 2, Day 1)
         17. A female of childbearing potential (FCBP)† must have a negative pregnancy test at
             screening and baseline. While on IP and for at least 28 days after taking the last
             dose of IP, a FCBP who engages in activity in which conception is possible must use
             one of the approved contraceptive§ options described below:
             Option 1: Any one of the following highly effective methods: hormonal contraception
             (oral, injection, implant, transdermal patch, vaginal ring); intrauterine device;
             tubal ligation; or partner's vasectomy; OR Option 2: Male or female condom (latex
             condom or non-latex condom NOT made out of natural [animal] membrane [for example,
             polyurethane]); PLUS one additional barrier method: (a) diaphragm with spermicide; (b)
             cervical cap with spermicide; or (c) contraceptive sponge with spermicide.
             † An FCBP is defined as a sexually mature female who 1) has not undergone a
             hysterectomy (the surgical removal of the uterus) or bilateral oophorectomy (the
             surgical removal of both ovaries) or 2) has not been postmenopausal for at least 24
             consecutive months (that is, has had menses at any time during the preceding 24
             consecutive months).
             § The female subject's chosen form of contraception must be effective by the time the
             female subject is screened into the study (for example, hormonal contraception should
             be initiated at least 28 days before screening).
         18. Must be in general good health (except for PsA) as judged by the investigator, based
             on medical history, physical examination, and clinical laboratories. (Note: The
             definition of good health means a subject does not have uncontrolled significant
             comorbid conditions).
        Exclusion Criteria:
        The presence of any of the following will exclude a subject from enrollment:
          1. Contraindication to MRI examination including, but not limited to, intracranial metal
             clips, heart pacemakers, insulin pumps, implanted hearing aids, neurostimulators,
             metal hip replacements, profound claustrophobia or inability to lie in the MRI machine
             in an appropriate position to obtain quality images, history of hypersensitivity to
             gadolinium contrast agent
          2. Severe renal impairment (creatinine clearance of less than 30 mL per minute estimated
             by the Cockroft-Gault equation), which would prevent the use of gadolinium enhancement
          3. History of clinically significant (as determined by the investigator) cardiac,
             endocrine, pulmonary, neurologic, psychiatric, hepatic, renal, hematologic,
             immunologic disease, or other major uncontrolled disease
          4. Any condition, including the presence of laboratory abnormalities, which places the
             subject at unacceptable risk if he/she were to participate in the study
          5. Prior history of suicide attempt at any time in the subject's lifetime prior to
             signing the informed consent, or major psychiatric illness requiring hospitalization
             within the last 3 years prior to signing the informed consent.
          6. Pregnant or breast feeding
          7. Active substance abuse or a history of substance abuse within 6 months prior to
             screening
          8. History of allergy or hypersensitivity to any component of the IP
          9. History of rare hereditary problems of galactose intolerance, lapp lactase deficiency
             or glucose-galactose malabsorption
         10. History of positive human immunodeficiency virus (HIV), or congenital or acquired
             immunodeficiency (eg, Common Variable Immunodeficiency Disease)
         11. Active tuberculosis or a history of incompletely treated tuberculosis
         12. Bacterial infections requiring treatment with oral or injectable antibiotics, or
             significant viral or fungal infections, within 4 weeks of screening. Any treatment for
             such infections must have been completed and the infection cured, at least 4 weeks
             prior to screening and no new or recurrent infections prior to the Baseline Visit
         13. Malignancy or history of malignancy or myeloproliferative or lymphoproliferative
             disease within the past 3 years, except for treated (ie, cured) basal cell or squamous
             cell in situ skin carcinomas;
         14. Major surgery (including joint surgery) within 8 weeks prior to screening or planned
             major surgery within 6 months following Baseline Visit
         15. Rheumatic autoimmune disease other than PsA, including, but not limited to: systemic
             lupus erythematosus, mixed connective tissue disease, scleroderma, polymyositis, or
             fibromyalgia
         16. Prior history of or current inflammatory joint disease other than PsA (eg, gout,
             reactive arthritis, RA, ankylosing spondylitis, Lyme disease), which confounds the
             ability to interpret data from the study
         17. Prior treatment with any biologic DMARD
         18. Prior treatment with more than 2 csDMARDs
         19. Use of the following systemic therapy(ies) within 28 days of the Baseline Visit (ie,
             Visit 2, Day 1): cyclosporine or other calcineurin inhibitors, glucocorticoids
             exceeding 10 mg daily prednisone equivalent, as well as mycophenolate.
         20. Use of MTX within 4 weeks of the Baseline Visit (ie, Visit 2, Day 1), unless subject
             is on
         21. Use of LEF within 12 weeks of the Baseline Visit (ie, Visit 2, Day 1), unless subject
             has taken cholestyramine, 8 g three times daily 11 days after stopping LEF
         22. Previous treatment with a JAK inhibitor (including tyk2 inhibitor)
         23. Prior treatment with apremilast, or participation in a clinical study involving
             apremilast
         24. Use of intra-articular (IA) glucocorticoid injection within 8 weeks before the
             Baseline Visit (ie, Visit 2, Day 1).
         25. Use of any investigational drug within 4 weeks of the Baseline Visit, or 5
             pharmacokinetic/pharmacodynamic half-lives, if known (whichever is longer)