Inclusion criteria:
* Male or female participant at least 18 years of age
* Participant is able to provide written informed consent and comply with the requirements of this study protocol.
* Participant has a BSA score of \>3 prior to randomization.
* Participant has previously failed treatment with an IL-17or IL-23 agent, defined as previous treatment with either drug for at least 3 months without achieving a BSA ≤3.
* Participant's last dose with most recent IL-17 or IL-23 agent was at least 28 days prior to baseline visit.
* Participant who are women of childbearing potential (WOCBP) must have a negative urine pregnancy test at screening and must be practicing an adequate and medically acceptable method of birth control for at least 30 days prior to Day 0 and at least 6 months after the last dose of study. Acceptable methods of birth control include intrauterine device (IUD) oral, transdermal, implanted or injected hormonal contraceptives (must have been initiated at least 1 month before entering the study); tubal ligation; abstinence; barrier methods with spermicide. If not of child-bearing potential, participants must have a sterile or vasectomized partner; have had a hysterectomy, a bilateral oophorectomy or be clinically diagnosed infertile; or be in a menopausal state for at least a year.
* Tuberculin purified protein derivative (PPD) or QuantiFERON TB-Gold test (QFT) negative at the time of screening, or if participant has a history of positive PPD or QuantiFERON, he/she has initiated or completed the appropriate treatment for latent tuberculosis.
* Participant is judged to be in good general health as determined by the principal investigator.
Exclusion criteria:
* Have predominantly pustular, erythrodermic, and/or guttate forms of psoriasis.
* Have drug induced psoriasis
* History of an ongoing, chronic or recurrent infectious disease, or evidence of tuberculosis infection as defined by a positive tuberculin purified protein derivative (PPD) or QuantiFERON TB-Gold test (QFT) at Screening. Participant with a positive or indeterminate PPD or QFT test must be assessed for evidence of active TB versus latent TB within 12 weeks prior to Baseline, including signs and symptoms and chest x-ray. If presence of latent tuberculosis is established, then treatment must have been initiated at least for 4 weeks prior to Baseline and completed. Participant with evidence of active TB may not be enrolled.
* Participants with a history of HIV, or history of hepatitis C or B infections.
* Use of any of the following therapies within 4 weeks prior to Baseline (Visit 2): systemic non-biologic psoriasis therapies, including, but not limited to: psoralens (topical or oral) and ultraviolet A (PUVA) therapy, cyclosporine, methotrexate, azathioprine, corticosteroids, apremilast, any JAK or TYK2 Inhibitors, oral retinoids, mycophenolate mofetil, sirolimus, 1, 25 dihydroxyvitamin D analogs, and other forms of phototherapy (including UVB or self-treatment with tanning beds or therapeutic sunbathing).
* Use of topical corticosteroids, topical calcineurin inhibitors, or other topical preparations with immunomodulatory properties within 2 weeks prior to Baseline (Visit 2).
* Use of any investigational drug or any systemic drug for psoriasis within 4 weeks prior to Baseline (Visit 2).
* Serious concomitant illness that could require the use of systemic corticosteroids or otherwise interfere with the participant's participation in the trial.
* Myocardial infarction or stroke within the 6 months prior to Baseline (Visit 2).
* Clinically important deviation as judged by the investigator (such WBC\< 3) from normal limits in physical examination, vital sign measurements, clinical laboratory tests results, and not associated with a chronic, well-controlled medical condition.
* Administration of any live vaccines 3 months prior to Baseline (Visit 2) and during the study.
* Have a current or history of lymphoproliferative disease within 5 years prior to Baseline (Visit 2); or have current or history of any malignant disease within 5 years prior to Baseline (Visit 2).
* History of suicide attempt, or are clinically judged by investigator to be at risk of suicide.
* History of IBD.
* Acute liver failure/cirrhosis.
* Had a serious infection, been hospitalized, or received IV antibiotics for an infection, within 12 weeks prior to Baseline (Visit 2).
* Known immunodeficiency, or history of infection typical of an immunocompromised host.