This study was created to provide subjects who complete Week 52 (end of Apremilast Extension Phase) of study CC-10004-PPSO-003 the option to continue to receive open-label apremilast therapy.

The study will consist of up to 208 weeks of long-term treatment followed by an 8-week observational follow-up phase.

Inclusion Criteria:

Subject must satisfy the following criteria to be enrolled in the study:

1. Subject is male or female 6 to 17 years of age, inclusive, at the time the informed consent document is signed by the legal guardian.
2. Subject must have a weight of ≥ 20 kg.
3. Subjects must have an age and sex specific BMI value no lower in range than the 5th percentile on the Centers for Disease Control (CDC) growth chart for children and adolescents.
4. Subject must have completed Week 52 (Apremilast Extension Phase) of Study CC-10004-PPSO-003.
5. Subject is able to sign an assent with a legal guardian/s who understand/s and voluntarily sign/s an informed consent prior to any study-related assessments/procedures being conducted.
6. Subject is willing and able to adhere to the study visit schedule and other protocol requirements.
7. All female subjects of childbearing potential (FCBP) must either practice abstinence from heterosexual contact or use one of the approved contraceptive options as described below while on apremilast and for at least 28 days after administration of the last dose of apremilast. For the purpose of this study, a female subject is considered of childbearing potential if she is ≥ 12 years old or has reached menarche, whichever occurred first.

At the time of study entry, and at any time during the study when a female subject of childbearing potential's contraceptive measures or ability to become pregnant changes, the Investigator will educate the subject regarding abstinence or contraception options and the correct and consistent use of effective contraceptive methods in order to successfully prevent pregnancy.

Females of childbearing potential must have a negative pregnancy test at each visit. All FCBP who engage in activity in which conception is possible must use one of the approved contraceptive options described below:

Option 1: Any one of the following effective methods: hormonal contraception (oral, injection, implant, transdermal patch, vaginal ring); intrauterine device (IUD); tubal ligation; or partner's vasectomy;

OR

Option 2: Male or female condom or nonlatex 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.

NOTE: Option 2 may not be acceptable as a contraception option in all countries per local guidelines/regulations.

Exclusion Criteria:

The presence of any of the following will exclude a subject from enrollment:

1. Subject has a condition, including the presence of laboratory abnormalities, or psychiatric illness, that would place the subject at unacceptable risk if he/she were to participate in the study.

2. Subject has a condition that confounds the ability to interpret data from the study.

3. Subject has evidence of skin conditions, other than psoriasis, that would interfere with clinical assessments.

4. Subject is pregnant or breastfeeding.

5. Subject has guttate, erythrodermic, or pustular psoriasis.

6. Subject has active tuberculosis (TB) or a history of incompletely treated TB.

7. Subject answers "Yes" to any question on the Columbia-Suicide Severity Rating Scale at Visit 16 of study CC-10004-PPSO-003.

8. Subject plans concurrent use of the following therapies that may have a possible effect on psoriasis.

   1. Conventional systemic therapy for psoriasis (including but not limited to cyclosporine, corticosteroids, methotrexate, oral retinoids, mycophenolate, thioguanine, hydroxyurea, sirolimus, sulfasalazine, azathioprine, and fumaric acid esters)
   2. Biologic therapy:

   i. Etanercept (or biosimilar) treatment ii. Adalimumab (or biosimilar) treatment iii. Other TNF or interleukin (IL)-17 blockers (such as infliximab, certolizumab pegol, secukinumab, ixekizumab, brodalumab, or their biosimilars) iv. Anti-IL-12 or anti-IL-23 treatment (such as ustekinumab, guselkumab, or tildrakizumab) c) Use of any investigational drug other than apremilast

9. Subject has prolonged sun exposure or use of tanning booths or other ultraviolet (UV) light sources.

10. Children in Care: a child who has been placed under the control or protection of an agency, organization, institution or entity by the courts, the government or a government body, acting in accordance with powers conferred on them by law or regulation.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication (or other new use) have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors, and if not approved, may be further arbitrated by a Data Sharing Independent Review Panel. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.