A Safety Study of CC-92252 in Healthy Adult Subjects and Adult Subjects With Psoriasis

Inclusion Criteria: Subjects must satisfy the following criteria to be enrolled in the study: Part 1, Part 2, and Part 3 1. Subject is ≥ 18 and ≤ 55 years (Part 1 and Part 2) and age is ≥ 18 and ≤ 60 years (Part 3) of age at the time of signing the ICF. 2. Subject has provided informed consent prior to initiation of any study specific activities/procedures 3. Subject has a body mass index (BMI) ≥ 18 and ≤ 30 kg/m2 (Part 1 and Part 2) and BMI ≥ 18 and ≤ 33 kg/m2 (Part 3), at screening. 4. Subject has clinical laboratory safety test results that are within normal limits or considered not clinically significant by the Investigator. Applicable to Part 3 only 5. Subject has a clinical diagnosis of stable plaque-type PsO at least 6 months prior to screening, defined as: BSA ≥ 5% (at both screening and baseline), and sPGA score ≥ 3 (at both screening and baseline) 6. Must have at least two plaques, at least 3 x 3 centimeters (cm) in diameter. One plaque will be used for punch biopsy and the other for Target Plaque Severity Score (TPSS) evaluation. 7. Must be in generally good health (except for PsO) as judged by the Investigator 8. No prior exposure to systemic treatments or biologics for the treatment of psoriasis Exclusion Criteria: The presence of any of the following will exclude a subject from enrollment: Part 1, Part 2, and Part 3 1. Subject has any significant medical condition that would prevent the subject from participating in the study. a. Part 3 only: This exclusion does not apply to plaque psoriasis 2. History or presence of cancer 3. Presence of pre-cancerous conditions 4. History or presence of a systemic infection or any potentially opportunistic infections 5. Subject has any condition, including the presence of laboratory abnormalities, which places the subject at unacceptable risk if he/she were to participate in the study 6. Subject has any condition that confounds the ability to interpret data from the study 7. Subject is pregnant or breastfeeding 8. Part 1 and Part 2 only: Subject was exposed to an investigational drug (new chemical entity) within 30 days preceding the first dose administration, or 5 half-lives of that investigational drug, if known (whichever is longer) 9. Part 1 and Part 2 only: Subject has used any prescribed systemic or topical medication within 30 days prior to the first dose administration. 10. Part 1 and Part 2 only: Subject has used any non-prescribed systemic or topical medication within 14 days prior to the first dose administration. Exceptions may apply on a case-by-case basis if considered not to interfere with the study objectives as agreed to and documented by the Investigator and Sponsor's Medical Monitor. 11. Subject has a history of drug abuse (as defined by the current version of the Diagnostic and Statistical Manual \[DSM\]) within 2 years before the first dose administration, or positive drug screening test reflecting consumption of illicit drugs 12. Subject has a history of alcohol abuse (as defined by the current version of the DSM) within 2 years before the first dose administration, or positive alcohol screen 13. Subject is known to have a history of hepatitis B and/or hepatitis C, or have a positive result to the test for human immunodeficiency virus (HIV) antibodies at screening Note: Subjects who received hepatitis B vaccination and who test positive for hepatitis B surface antibody and negative for both hepatitis B surface antigen and hepatitis B core antibody remain eligible for study participation 14. Subject smokes \> 10 cigarettes per day, or the equivalent in other tobacco products (self-reported) 15. Vaccination within 30 days prior to the first dose administration or subject has plans to receive a vaccination during the course of the study 16. Subject has received immunization with a live or live attenuated vaccine within 2 months prior to the first dose administration or is planning to receive immunization with a live or live attenuated vaccine for 2 months following the last dose administration 17. Subject has a positive QuantiFERON®-TB Gold (or equivalent) TB test at screening or 2 successive indeterminate QuantiFERON®-TB Gold (or equivalent) TB tests at screening 18. Subject has a history of incompletely treated Mycobacterium tuberculosis (TB) infection 19. Topical therapy within 2 weeks of randomization (including, but not limited to, topical corticosteroids, retinoids or vitamin D analog preparations, tacrolimus, pimecrolimus, or anthralin/dithranol). Use of phototherapy within 4 weeks prior to first dose administration. 20. Prolonged sun exposure or use of tanning booths Applicable to Part 3 only 21. Presence of non-plaque psoriasis 22. Subject has psoriasis flare within 4 weeks before screening 23. Presence of dermatological diseases other than plaque psoriasis 24. Presence of Psoriatic Arthritis 25. Use of topical therapy for psoriasis within 14 days of first dosing (including but not limited to corticosteroids, retinoids, vitamin D analog, calcineurin inhibitors, salicylic acid) Exceptions: low potency topical corticosteroids will be allowed as background therapy for treatment of psoriatic lesions of the face, axillae and groin in accordance with the manufacturers' suggested usage; subjects with scalp psoriasis will be permitted to use coal tar shampoo and/or salicylic acid scalp preparations on scalp lesions; Eucerin® cream (the standard emollient for this study; or equivalent) will also be permitted for body lesions only. Subjects must not use these treatments within 24 hours prior to each clinic visit. 26. Use of systemic therapy for psoriasis within 30 days of first dose administration 27. Use of phototherapy for psoriasis within 30 days of first dose administration 28. Use of systemic biologic treatment within 24 weeks of first dose administration 29. Exposure to an immunosuppressive or immunomodulatory drug within 30 days of first dose administration, or five half-lives of the drug (whichever is longer) 30. Exposure to an investigational drug (new chemical entity) within 30 days preceding the first dose administration, or five half-lives of that investigational drug, if known (whichever is longer)