This study will evaluate the systemic exposure and characterize the plasma pharmacokinetic (PK) profile and assess the safety and tolerability of ARQ-154 foam 0.3%.

ARQ-154-127 is a Phase 1, open-label, single arm, maximum usage pharmacokinetic and safety study of roflumilast foam 0.3% in participants with scalp and body psoriasis.

The goal of the study is to:

• Evaluate the systemic exposure and characterize the plasma pharmacokinetic (PK) profile of ARQ-154 foam 0.3%.
• Assess the safety and tolerability of ARQ-154 foam 0.3%

Inclusion Criteria:

• Males and females, ages 2 years to < 12 years old at Day 1.
• Clinical diagnosis of psoriasis vulgaris of at least 2 months duration at Screening as determined by the Investigator.
• Scalp psoriasis with an Investigator Global Assessment (S-IGA) of scalp disease severity of at least Moderate ('3') at Day 1.
• An IGA of body (non-scalp) psoriasis (B-IGA) of at least Mild ('2') at Day 1.
• Extent of scalp psoriasis involving ≥ 10% of the total scalp at Day 1.
• Body psoriasis (non-scalp) involving at least 3% BSA on Day 1.

Exclusion Criteria:

• Participants who cannot discontinue medications and treatments prior to Day 1 (first application of IP).
• Current diagnosis of non-plaque forms of psoriasis. Current diagnosis of drug-induced psoriasis.
• Participants who have significant active systemic or localized infection or have had any infection that required oral or intravenous administration of antibiotics, antifungal or antiviral agents within 7 days prior to Day 1.
• Participants with skin conditions other than psoriasis vulgaris that would interfere with evaluations of the effect of the study medication, as determined by the Investigator.
• Participants who cannot discontinue the use of strong cytochrome P-450 CYP3A4 inhibitors for 2 weeks prior to Day 1 and during the study period.
• A medical history of severe renal insufficiency, moderate to severe hepatic disorders (e.g., Child-Pugh B or C), or chronic infectious disease (e.g., hepatitis B, hepatitis C, or human immunodeficiency virus [HIV]).
• Participants who are family members of the clinical study staff or sponsor.