A Phase 3 Study in Participants With Moderate to Severe Psoriasis

Inclusion Criteria:

- Present with chronic plaque psoriasis based on a confirmed diagnosis of chronic
psoriasis vulgaris for at least 6 months prior to randomization

- At least 10% Body Surface Area (BSA) of Psoriasis at screening and at randomization

- Static Physician Global Assessment (sPGA) score of at least 3 and Psoriasis Area and
Severity Index (PASI) score of at least 12 at screening and at randomization

- Candidate for phototherapy and/or systemic therapy

- Men must agree to use a reliable method of birth control during the study

- Women must agree to use birth control or remain abstinent during the study and for at
least 12 weeks after stopping treatment

Exclusion Criteria:

- Pustular, erythrodermic, and/or guttate forms of psoriasis

- History of drug-induced psoriasis

- Clinically significant flare of psoriasis during the 12 weeks prior to randomization

- Concurrent or recent use of any biologic agent

- Received systemic psoriasis therapy [such as psoralen and ultraviolet A (PUVA) light
therapy] or phototherapy within the previous 4 weeks; or had topical psoriasis
treatment within the previous 2 weeks prior to randomization

- Cannot avoid excessive sun exposure or use of tanning booths for at least 4 weeks
prior to randomization and during the study

- Have participated in any study with interleukin (IL)-17 antagonists, including
LY2439821

- Serious disorder or illness other than plaque psoriasis

- Serious infection within the last 3 months

- Breastfeeding or nursing (lactating) women.