The aim of this study is to evaluate safety, tolerability, and efficacy of PRCL-02 in moderate to severe chronic plaque psoriasis

Inclusion Criteria:

• Presents with moderate to severe psoriasis vulgaris based on:

  • Chronic psoriasis vulgaris for at least 6 months
  • Plaque psoriasis involving at least 10% body surface area (BSA)
  • Psoriasis Area and Severity Index (PASI) total score of at least 12

• Have at least 2 evaluable plaques located in 2 different body regions. (Also for participants who elect to have plaques biopsied, should be suitable for a total of 4 punch biopsies each, and one lesion, preferably on a region of the body that is not normally exposed (e.g., trunk), should be selected for biopsy)

• Have a Static Physician's Global Assessment (sPGA) score of greater than or equal to (≥)3

• Are candidates for systemic therapy

• Have a body mass index (BMI) within the range of 18 to 40 kilograms per square meter (kg/m2)

• Women who are of childbearing potential must agree to use 1 highly effective method of contraception, or a combination of 2 effective methods of contraception for the entirety of the study

• Women of non childbearing potential are defined as women who are:

  • Infertile due to surgical sterilization (hysterectomy, bilateral oophorectomy, or tubal ligation), congenital anomaly such as mullerian agenesis; or

  • Post-menopausal, defined as either:

    • A woman at least 50 years of age with an intact uterus, not on hormone therapy, who has had either: cessation of menses for at least 1 year; or at least 6 months of spontaneous amenorrhea with a follicle stimulating hormone greater than (>)40 milli-international units per milliliter (mIU/mL); or
    • A woman 55 years or older not on hormone therapy, who has had at least 6 months of spontaneous amenorrhea; or
    • A woman at least 55 years of age with a diagnosis of menopause prior to staring hormone replacement therapy

Exclusion Criteria:

• Currently enrolled in any other clinical trial involving a study drug or device, or any other type of medical research judged not compatible with this study (Participants in the previous PRCL study (SMAD) will be allowed to be included in this study, provided that they meet all inclusion and none of the exclusion criteria)

• Participated in a clinical study within last 30 days

• Present with pustular, erythrodermic psoriasis, generalized pustular psoriasis, or acute guttate psoriasis

• Have current serious or unstable illnesses including hepatic, renal, gastroenterologic, respiratory, cardiovascular (including a history of ischemic or structural heart disease, conduction system disease or history of clinically significant arrhythmia), endocrinologic, neurologic, psychiatric, immunologic, hematologic, or dermatologic disease

• Have a history of clinically significant severe drug allergies or severe post treatment hypersensitivity reactions

• Have received inactivated vaccine within 4 weeks prior to dosing in this study, or a live vaccine within the last 3 months

• A history of clinically significant opportunistic infection (for example, invasive candidiasis or Pneumocystis pneumonia)

• Had symptomatic herpes zoster within last 3 months or other recent or ongoing infection

• Present with any of the following laboratory test results:

  • Positive QuantiFERON®-tuberculosis test
  • For women, positive serum pregnancy test
  • Evidence of Human Immunodeficiency Virus (HIV) infection or are positive for HIV antibodies
  • Positive test for active hepatitis B
  • Positive of anti-hepatitis C antibody with confirmed presence of hepatitis C virus, or chronic liver disease

• Evidence of clinically significant hepatic or renal impairment

• Clinically significant ECG (electrocardiogram) abnormalities or personal or family history of heart disease, including:

  • Confirmed corrected QT interval with Frederica's correction (QTcF) >450 milliseconds (msec) for both men and women
  • Specific bundle branch blocks, irregular rhythms, history of unexplained syncope, or family history of unexplained death

• Are receiving any of the following therapies for psoriasis:

  • Systemic retinoids within last 12 weeks
  • Systemic psoriasis therapy, such as psoralen and ultraviolet A (PUVA) light therapy, cyclosporine, corticosteroids, methotrexate, oral retinoids, mycophenolate mofetil, thioguanine, hydroxyurea, sirolimus, azathioprine, or phototherapy (including ultraviolet B or self-treatment with tanning beds or therapeutic sunbathing) within last 4 weeks
  • Topical psoriasis treatment within last 2 weeks; or
  • Any biologic agent within the following washout periods: 30 days for anti-tumor necrosis factor (TNF) inhibitors, and 90 days for other agents

Safety population

20 weeks