Patient with moderate-to-severe plaque psoriasis will receive Ilumya with or without Halog ointment.

25 adult subjects with moderate to severe plaque psoriasis will receive Ilumya 100mg subcutaneously at weeks 0, 4 and 16.

At week 16, patients with remaining BSA ˃3% will be given HALOG ointment 0.1% to apply BID for 4 weeks. Patients who have ≤3% BSA at week 16 will remain on Ilumya monotherapy.

Patients will continue to be evaluated at weeks 20 and 24.

Inclusion Criteria:

1. Male or female adult ≥ 18 years of age;

2. Diagnosis of moderate-to-severe chronic plaque-type psoriasis as defined by

   • BSA 10%
   • PGA ≥3
   • PASI ≥12

3. Must be a candidate for phototherapy and/or systemic therapy

4. Females of childbearing potential (FCBP) must have a negative serum pregnancy test at Screening and negative urine pregnancy test at Baseline. FCBP who engage in activity in which conception is possible must use one of the approved contraceptive options: hormonal contraception; intrauterine device (IUD); tubal ligation; or partner's vasectomy; Male or female condom diaphragm with spermicide, cervical cap with spermicide, or contraceptive sponge with spermicide.

Exclusion Criteria:

1. Non-plaque forms of psoriasis
2. Women of childbearing potential who are pregnant, intend to become pregnant, or are lactating
3. Presence of significant uncontrolled medical condition that in the opinion of the investigator would affect patient safety during the trial.
4. Active or untreated latent tuberculosis (TB)