Extension Trial Assessing the Safety and Efficacy of BI 655066/ABBV-066/Risankizumab in Patients With Moderate to Severe Chronic Plaque Psoriasis

Inclusion criteria: * Participants with moderate to severe chronic plaque psoriasis, who have successfully completed Study 1311.2 (NCT02054481; the lead-in study). Successful completion of the lead-in study is defined as either of the following: 1. Completion of the entire follow up period, thus reaching End-of-study (EOS) visit. 2. Loss of response, defined as decrease in response to achieving \< 50% improvement in Psoriasis Area and Severity Index Score (PASI50) at any time from Week 24. * Participant must give informed consent and sign an approved consent form prior to any study procedures in accordance with Good Clinical Practice (GCP) and local legislation * Applicable only for female participants: * Negative urine pregnancy dip stick test at the roll-over visit, and if available at roll-over visit, negative Serum ß-Human Chorionic Gonadotropin (ß-HCG) test. In addition: Women of childbearing potential (not surgically sterilized and between menarche and 1 year postmenopausal), that, if sexually active agree to use one of the appropriate medically accepted methods of birth control in addition to the consistent and correct use of a condom from date of the roll-over visit until 12 weeks after last treatment in this study. Medically accepted methods of contraception are: ethinyl estradiol containing contraceptives, diaphragm with spermicide substance, and intra-uterine-device. OR Female participants which have vasectomized sexual partner(s) (vasectomy at least 1 year prior to enrollment). OR Surgically sterilized female participants with documentation of prior hysterectomy, tubal ligation or complete bilateral oophorectomy. OR Postmenopausal women with postmenopausal is defined as permanent cessation ≥ 1 year of previously occurring menses. Exclusion criteria: * Participants who experienced any drug related serious adverse event (SAE) in the lead-in study * Participants who have developed guttate, erythrodermic or pustular psoriasis or drug-induced psoriasis (as diagnosed by the investigator), during the lead-in study. * Evidence of current or previous clinically significant disease, medical condition other than psoriasis, or finding of the medical examination (including vital signs and electrocardiography \[ECG\]), that in the opinion of the investigator, would compromise the safety of the participant or the quality of the data. * Known clinically important acute or chronic infections including hepatitis, human immunodeficiency virus (HIV). In regards to tuberculosis (TB), the following applies: * Signs or symptoms suggestive of current active or latent TB upon medical history, physical examination and/or a chest radiograph (both posterior-anterior and lateral views, taken within 3 months prior to the first administration of study drug and read by a qualified radiologist). * History of latent or active TB prior to screening, except for participants with documented completion of an adequate treatment regimen, at least 6 months prior to the first administration of study agent. * Positive QuantiFERON-TB Gold In-Tube test (IGRA) within 2 months prior to the roll-over visit (if available), in which active TB has not been ruled out. This does not apply to participants with history of latent TB with documented completion of an adequate treatment regimen, at least 6 months prior to the first administration of study agent. * Participants who have developed malignancy, or suspicion of active malignant disease during the lead-in study (except treated cutaneous squamous cell or basal cell carcinoma or carcinoma in situ of the cervix that have been adequately treated). * Intake of restricted medications or other drugs considered likely to interfere with the safe conduct of this study, as assessed by the investigator. * Alcohol or drug abuse within 3 months prior to the roll-over visit that would interfere with trial participation or any ongoing condition leading to a decreased compliance to study procedures in the opinion of the investigator. * Any clinically significant laboratory abnormalities based on the last available laboratory results received during the lead-in study (according to the investigator's medical assessment). * Pre-menopausal woman who is pregnant or nursing.