A Study of Ixekizumab in Participants With Plaque Psoriasis

Inclusion Criteria: * Males and females with chronic moderate or severe plaque psoriasis for at least 6 months who are candidates for systemic therapy or phototherapy * Men and women of childbearing potential must agree to use a reliable method of birth control and men may not donate sperm for the duration of the study. Women must test negative for pregnancy at screening and agree not to become pregnant during the study and until the first normal period following the end of the study * Have a body mass index (BMI) of 18.5 to 40.0 kilograms per square meter (kg/m²), inclusive, at screening * Have greater than or equal to (≥) 10 percent body surface area (BSA) involvement at screening and first admission to the clinical research unit (CRU) * Have both a Static Physicians Global Assessment (sPGA) score of ≥3 and Psoriasis Area Severity Index (PASI) score ≥12 at screening and first admission to the CRU Exclusion Criteria: * Forms of psoriasis other than chronic plaque-type * Pregnant or nursing (lactating women) * History of an ongoing, chronic or recurrent infectious disease, or evidence of tuberculosis infection * Have major surgery within 8 weeks prior to first admission to the clinical research unit or during the study * Have a history of lymphoproliferative disease, or signs or symptoms of lymphoproliferative disease, or have active or history of malignant disease, or have uncontrolled cerebrocardiovascular or neuropsychiatric disease * Require treatment with the cocktail drugs or with inhibitors of cytochrome P450 (CYP) 3A, CYP2C9, CYP2D6, CYP2C19, CYP1A2, or with inducers of CYP3A or CYP1A2, or with rifampin (inducer of multiple CYPs) or with substrates of CYP3A, CYP2C9, CYP2D6, CYP2C19, or CYP1A2 with narrow therapeutic indices within 14 days prior to the first administration of the drug cocktail through the end of Week 12 assessments * Have any known allergy or hypersensitivity to any component of the study cocktail or ixekizumab * Have participated in any other study with ixekizumab, secukinumab or brodalumab, or have been prescribed ixekizumab or secukinumab