Study to Evaluate Broadlumab vs Placebo and Ustekinumab

Inclusion Criteria: * Subject has had stable moderate to severe plaque psoriasis for at least 6 months before first dose of IP. * Subject has involved body surface area \>\_10%, PASI\>\_, and sPGA\>\_3 at screening and at baseline. * For women, a negative serum pregnancy test during screening a negative urine pregnancy test at baseline. * Subject has no known history of active tuberculosis. * Subject has a negative test for tuberculosis during screening. Exclusion Criteria: * Subject diagnosed with erythrodermic psoriasis, pustular psoriasis, guttate psoriasis, medication-induced psoriasis, or other skin conditions at the time of the screening visit that would interfere with evaluations of the effect of IP on psoriasis. * Subject has a planned surgical intervention between baseline and the week 52 evaluation. * Subject an active infection or history of infections. * Subject has any systemic disease considered by the investigator to be clinically significant and uncontrolled. * Subject has known history of Crohn's disease. * Subject has known history of hepatitis B, hepatitis C, or human immunodeficiency virus. * Subject had myocardial infarction or unstable angina pectoris within the past 12 months prior to the first dose of IP. * Subject has any active malignancy, including evidence of cutaneous basal or squamous cell carcinoma or melanoma. * Subject has history of malignancy within 5 years EXCEPT treated and considered cured cutaneous squamous or basal cell carcinoma, in situ cervical cancer, or in situ breast ductal carcinoma. * Subject has received live vaccine(s) within 28 days of the first dose of IP. * Subject has used ustekinumab and/or antio-IL-17 biologic therapy ever or other experimental or commercially available biologi immune modulator(s) within 12weeks prior to the first IP dose * Subject currently is enrolled in another investigational device or drug study, or less than 30 days since ending another investigational device or drug study(s), or receiving other investigational agent(s). * For women not willing to use highly effective methods of birth control during treatment and for 15 weeks after the last dose. * For women; pregnant or breast feeding, or planning to become pregnant while enrolled in the study and for 15 weeks after the last dose.