Residual Disease MEMory in PSOriasis Skin During EnstiLAR® and Narrow-band Ultraviolet B Therapy: The MEMPSOLAR Study

Psoriasis is a non-communicable chronic immune-mediated disease. Psoriatic skin is characterized by excessive proliferation of skin cells and infiltration of immune cells. The cause of psoriasis is so far unknown. Established therapeutics include topical, oral-systemic, biologic, narrow-band ultraviolet B (NB-UVB). A persistent antipsoriatic effect by the newest biologic therapies has been demonstrated after treatment discontinuation. However, the remittive hallmark of psoriasis suggests the existence of a molecular scar, a kind of disease memory, in clinically healed skin. It has been suggested that this disease memory can be attributed to the tissue-resident memory T (TRM) cell. The main purpose of the study is to investigate whether (NB-UVB) treatment and concomitant Enstilar® treatment can change the amount of TRMs in the skin as well as change the expression in the microenvironment around these cells in the skin from psoriasis patients. In addition, the investigators will investigate whether the treatment can change the quantity and types of other psoriasis-related cells in the skin. In addition to this, the investigators will also examine the effect of treatment on patient-related parameters.

Inclusion Criteria: Age: 1. Women or men with chronic stable plaque psoriasis aged 18 years or older at the time of consent. Consent must be obtained prior to any study-related procedures. The participants must furthermore be willing to participate and must be of a condition capable of giving informed consent. Type of participant and disease characteristics: 2. History of chronic stable plaque psoriasis. 3. Candidate for topical treatment, as judged by the investigator. 4. Candidate for NB-UVB treatment, as judged by the investigator. 5. Two target lesions of \~3 cm at its longest axis located on the body (except for the scalp, face, or intertriginous areas), scoring at least 1 for each of redness, thickness, and scaliness on the TPSS. 6. Women involved in any sexual intercourse that could lead to pregnancy must agree to use an effective contraceptive method from at least 4 weeks before baseline (visit 2). Effective contraceptive methods are: Systemic hormonal contraceptives (oral contraceptive, transdermal patches, vaginal rings, long-acting injectables, or implants), intrauterine devices, vasectomy, or barrier methods of contraception in conjunction with spermicide. This must be used until EOT. Hormonal contraceptives must be on a stable dose for at least 4 weeks before baseline (visit 2). a. Women of nonchildbearing potential are as follows: i. Women ≥60 years of age. ii. Women who have had surgical sterilization (hysterectomy, bilateral oophorectomy, bilateral salpingectomy, or bilateral tubal ligation) iii. Women \>40 and \