The goal of this clinical trial is to learn if ESK-001 works to treat moderate to severe plaque psoriasis. The main questions it aims to answer are: * Does ESK-001 reduce the severity of people's psoriasis? * How safe is ESK-001 in people with moderate to severe plaque psoriasis? The study includes 2 comparators: a placebo control (a 'dummy' tablet that does not contain the medicine ESK-001 but looks just like it) and an active control (apremilast, which is a medicine approved to treat psoriasis). People taking part in this study must be men or women aged at least 18 years and have had plaque psoriasis for at least 6 months, currently moderate to severe. Participants will: * take drug every day for 24 weeks. * visit the clinic for checkups and tests. * fill out questionnaires about their psoriasis, itch severity, and change in quality of life. * be assessed for health issues and side effects, physical examinations, vital signs, heart electrical activity measurements, and psychological health. * provide blood and urine samples.