Multiple Dose Study of UCB4940 as add-on to Certolizumab Pegol in Subjects With Rheumatoid Arthritis

Inclusion Criteria To be eligible to participate in this study, all of the following criteria must be met: * Subject is informed and given approved written Informed Consent Form (ICF). * Subject is considered reliable and capable of adhering to the protocol. * Subject must have a diagnosis of adult-onset moderate-to-severe RA of at least 6 months' duration as defined by ACR/EULAR 2010 classification criteria. * Subject must have: * ≥6 tender joints (out of 68) * ≥6 swollen joints (out of 66) * CRP≥10.0mg/L . * Subject must have had inadequate response to at least 1 synthetic DMARD. * Subject is at least 18 years and less than 70 years of age at Visit 1 (Screening). * Female subjects must either be: * postmenopausal * permanently sterilized or, * if of childbearing potential, must be willing to use at least 2 effective methods of contraception, * Male subjects with partners of childbearing potential must be willing to use a condom when sexually active, during the study and for 5 months after last administration of study drug. Exclusion Criteria Subjects are not permitted to enroll in the study if any of the following criteria is met: * Subject has previously participated in this study or has previously been assigned to treatment in a study of the investigational medicinal product (IMP) under investigation in this study (UCB4940 and/or CZP). * Subject has a history or active systemic/respiratory infection due to fungal, parasitic, or mycotic pathogens. * Subjects with known tuberculosis (TB) infection, at high risk of acquiring TB infection, or latent TB infection are excluded. * Subject is at high risk of infection. * Subject has an active infection or has had a serious infection within 12 weeks prior to the first dose of study drug at Week 0. * Subject has renal or liver impairment. * Subject has a current or past history of gastrointestinal ulceration. * Subject has active neoplastic disease or history of neoplastic disease. * Subject has a concomitant diagnosis of any other inflammatory condition. * Subject has a secondary, non-inflammatory condition or a known diagnosis of fibromyalgia.