This Phase 3 multicenter, randomized, placebo-controlled, double-blind study is designed to evaluate the efficacy and safety of apremilast in subjects with moderate to severe genital psoriasis (modified sPGA-G ≥3, moderate or severe).

Approximately 286 subjects with moderate to severe genital psoriasis will be randomized 1:1 to receive either apremilast 30 mg BID or placebo for the first 16 weeks.

The study will consist of four phases:

• Screening Phase - up to 35 days

• Double-blind Placebo-controlled Phase - Weeks 0 to 16

  - Subjects will be randomly assigned to either apremilast 30 mg tablets orally BID or placebo tablets (identical in appearance to apremilast 30 mg tablets) orally BID.

• Apremilast Extension Phase - Weeks 16 to 32

  - All subjects will be switched to (or continue with) apremilast 30 mg BID. All subjects will maintain this dosing through Week 32.

• Observational Follow-up Phase - 4 weeks - Four-week Post-Treatment Observational Follow-up Phase for all subjects who complete the study or discontinue the study early.

Inclusion Criteria:

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

1. Subject is ≥ 18 years of age at the time of signing the informed consent form (ICF).
2. Subject must have a diagnosis of chronic plaque psoriasis for at least 6 months prior to signing the ICF.
3. Subject must have a diagnosis of moderate or severe psoriasis of the genital area at Screening and Baseline.
4. Subject must have a diagnosis of moderate or severe psoriasis at Screening and Baseline.
5. Subject must have plaque psoriasis (BSA ≥ 1%) in a non-genital area at both Screening and Baseline.
6. Subject must have been inadequately controlled with or intolerant of topical therapy, or topical therapy is inappropriate for the treatment of psoriasis affecting the genital area.
7. Subject must be in good health (except for psoriasis) as judged by the investigator, based on medical history, physical examination, clinical laboratories, and urinalysis.
8. Subject must meet laboratory criteria

Exclusion Criteria:

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

1. Subject has any significant medical condition or laboratory abnormality, that would prevent the subject from participating in the study.
2. 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.
3. Subject has positive Hepatitis B surface antigen or anti-hepatitis C antibody at Screening.
4. Subject has active tuberculosis (TB) or a history of incompletely treated TB.
5. Subject has prior history of suicide attempt at any time in the subject's life time prior to signing the informed consent and randomization, or major psychiatric illness requiring hospitalization within the last 3 years prior to signing the informed consent.
6. Subject has current or planned therapies that may have a possible effect on psoriasis of the body and/or genital area during the course of the treatment phase of the trial
7. Subject had prior treatment with apremilast.

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 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. If not approved, a Data Sharing Independent Review Panel will arbitrate and make the final decision. 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.