A Study to Assess the Safety, Pharmacokinetics and Pharmacodynamics of UCB4940 in Patients With Psoriasis

Inclusion criteria: * Subject is male or female, aged ≥ 18 years to ≤ 70 years at Screening. Female subjects must either be postmenopausal (at least 1 year), permanently sterilized or, if of childbearing potential, must be willing to use at least 2 effective methods of contraception, including a barrier method during the study period. Effective methods of contraception are methods of birth control, which result in a low failure rate when used consistently and correctly, such as implants, injectables, oral contraceptives, progesterone-releasing intrauterine systems or the TCu 380A intrauterine device, complete sexual abstinence, or vasectomized partner. Male subjects with partners of childbearing potential must be willing to use a condom when sexually active. Both male and female subjects must use the above mentioned contraception for 20 weeks after administration of study drug (anticipated 5 half-lives) * Subject has had a confirmed diagnosis of mild to moderate plaque-type psoriasis for at least 6 months involving ≤ 5 % of body surface area (BSA) (excluding the scalp) * Subject has a body mass index of ≤ 35 kg/m\^2 at Screening * Subject has a minimum of 2 psoriatic lesions with at least 1 plaque in a site suitable for biopsy Exclusion Criteria: * Female subject who is pregnant, or plans to become pregnant during the study, or lactating, or sexually active with childbearing potential who is not using a medically accepted birth control method * Subject has received systemic nonbiologic psoriasis therapy (methotrexate \[MTX\], steroids, cyclophosphamide) or psoralen plus ultraviolet A (PUVA)/ultraviolet A (UVA) phototherapy within 4 weeks prior to Screening * Subject has received treatment with biologic agents within 12 months prior to the study * Subject has received live attenuated vaccination within 6 weeks prior to Screening or intends to have such a vaccination during the course of the study * Subject has received any investigational drug or experimental procedure within 90 days or 5 half-lives, whichever is longer, prior to IMP administration * Subject requires treatment with a nonsteroidal anti-inflammatory drug during the study period. Paracetamol will be permitted for use as an antipyretic and/or analgesic * Subject has an active infection (eg, sepsis, pneumonia, abscess) or has had a serious infection (resulting in hospitalization or requiring parenteral antibiotic treatment) within 6 weeks prior to IMP administration. When in doubt, the Investigator should confer with the UCB Study Physician * Subject has a history of a positive tuberculosis (TB) test or evidence of possible TB or latent TB infection at Screening that cannot be attributed to a prior Bacillus Calmette-Guérin inoculation * Subject has renal or liver impairment, defined as: * For women, serum creatinine level ≥ 125 μmol/L; for men, ≥ 135 μmol/L, or * ALT and aspartate aminotransferase ≥ 2x ULN, or * Alkaline phosphatase and bilirubin \> 1.5x ULN (an isolated bilirubin \> 1.5x ULN is acceptable if bilirubin is fractionated and direct bilirubin is \< 35 %) * Subject has active neoplastic disease or history of neoplastic disease within 5 years of Screening (except for basal or squamous cell carcinoma of the skin or carcinoma in situ that has been definitively treated with standard of care)