- Primary failure (no response within 12 weeks) to 1 or more interleukin-17 (IL-17) biologic response modifiers (eg, brodalumab, ixekizumab, secukinumab) OR more than 1 biologic response modifier other than an IL-17 - Study participant has a presence of guttate, inverse, pustular, or erythrodermic PSO or other dermatological condition that may impact the clinical assessment of PSO - Study participant has a history of inflammatory bowel disease (IBD) or symptoms suggestive of IBD - History of active tuberculosis unless successfully treated, latent TB unless prophylactically treated - Study participant has an active infection or history of infections (such as serious infection, chronic infections, opportunistic infections, unusually severe infections) - Study participant has previously received bimekizumab - Study participant has previously received ustekinumab - Study participant has received drugs outside the specified timeframes relative to the Baseline Visit or receives prohibited concomitant treatments - Study participant has the presence of active suicidal ideation, or positive suicide behavior - Study participant diagnosed with severe depression in the past 6 months (prior to Screening) should be excluded - Study participant has a history of psychiatric inpatient hospitalization within the past year before enrolling into the study