Researchers want to find out if giving the drug Apremilast in combination with Clobetasol spray can help people clear their moderate to severe plaque psoriasis quicker than if Apremilast is used by itself.

People over age 18 with moderate to severe plaque psoriasis who choose to be in the study and pass the four week screening period will visit the study center about 8 times over about 16 weeks. All participants will be given Apremilast, a pill that you take in the morning and at night, and which studies have shown may reduce inflammation and improve psoriasis symptoms. All participants will also be given Clobetasol to spray twice daily for two weeks, then once daily for two weeks, then every other day for two weeks. All drugs and study visits are at no cost to participants.

Inclusion Criteria:

1. Must be in general good health (except for disease under study) as judged by the Sponsor Investigator, based on medical history, and physical examination. (NOTE: The definition of good health means a subject does not have uncontrolled significant co-morbid conditions).

2. Females of childbearing potential (FCBP)† must have a negative pregnancy test at Screening and Baseline.

   Option 1: Any one of the following highly 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 (latex 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

3. Plaque psoriasis with at least 10% body surface area (BSA) involving the body with or without scalp lesions in adults aged 18 years and older.

Exclusion Criteria:

1. Other than disease under study, any clinically significant (as determined by the Sponsor Investigator) cardiac, endocrinologic, pulmonary, neurologic, psychiatric, hepatic, renal, hematologic, immunologic disease, or other major disease that is currently uncontrolled.

2. Any condition which would place the subject at unacceptable risk if he/she were to participate in the study.

3. Prior history of suicide attempt at any time in the subject's life time prior to screening or baseline, or major psychiatric illness requiring hospitalization within the last 3 years.

4. Pregnant or breast feeding.

5. Active substance abuse or a history of substance abuse within 6 months prior to Screening.

6. Malignancy or history of malignancy, except for:

   1. treated [ie, cured] basal cell or squamous cell in situ skin carcinomas;
   2. treated [ie, cured] cervical intraepithelial neoplasia (CIN) or carcinoma in situ of cervix with no evidence of recurrence within the previous 5 years.

7. Use of any investigational drug within 4 weeks prior to baseline, or 5 pharmacokinetic/pharmacodynamic half-lives, if known (whichever is longer).

8. Prior treatment with apremilast.

9. Concomitant use of drugs that treat psoriasis including but not limited to methotrexate, acitretin, cyclosporine within 4 weeks of baseline.

10. Adalimumab, etanercept, efalizumab, infliximab, or certolizumab pegol within 12 weeks prior to baseline.

11. Alefacept, briakinumab, ixekizumab, brodalumab or ustekinumab within 24 weeks prior to baseline.

12. Use of phototherapy within 4 weeks prior to baseline

13. Plaque-type psoriasis with BSA<10%

14. Psoriasis predominantly involving the face or folds (groin or axilla)

15. Psoriasis only of the palms/soles, pustular or other forms of psoriasis

16. Concurrent skin or systemic infection

17. History of intolerance to topical steroids or apremilast.

18. Topical therapy within 2 weeks of baseline (including but not limited to topical corticosteroids, topical retinoids or vitamin D analog preparations, tacrolimus, pimecrolimus, or anthralin/dithranol). Exceptions: Clobetasol Spray 0.05%.