For the treatment of severe (see Note 1 below) plaque psoriasis in patients 18 years of age or older who have experienced failure, intolerance, or have a contraindication to adequate trials of several standard therapies (see Note 2 below). Claims for the first 6 months must be written by a dermatologist. Monitoring of patients is required to determine if continuation of therapy beyond 12 weeks is required. Patients not responding adequately at 12 weeks should have treatment discontinued. Note 1: Definition of severe plaque psoriasis: - Body Surface Area (BSA) involvement of at least 10%, or involvement of the face, hands, feet or genital regions, AND - Psoriasis Area and Severity Index (PASI) score of at least 10 (not required if there is involvement of the face, hands, feet or genital regions), AND - Dermatology Life Quality Index (DLQI) score of at least 10. Note 2: Definition of failure, intolerance or contraindication to adequate trials of standard therapies: - 6 month trial of at least 3 topical agents including vitamin D analogues and steroids, AND - 12 week trial of phototherapy (unless not accessible), AND - 6 month trial of at least 2 systemic, oral agents used alone or in combination - Methotrexate 15-30mg per week - Acitretin (could have been used with phototherapy) - Cyclosporine Maintenance/Renewal: After 3 months of therapy, patients who respond to therapy should have: - at least a 50% reduction in PASI, AND - at least a 50% reduction in BSA involvement, AND - at least a 5 point reduction in DLQI score Approvals will allow for standard dosing for Bimzelx, which is 320mg subcutaneously every 4 weeks for the first 16 weeks, and every 8 weeks thereafter. A dose of 320mg every 4 weeks after the first 16 weeks may be considered in patients with a body weight of 120kg or more who did not achieve a complete skin response. For patients with no improvement after 16 weeks of treatment at the Health Canada approved dose, higher or more frequent doses are not recommended and the physician should consider switching to an alternative biologic agent.