A Study to Assess the Long-term Safety, Tolerability, and Efficacy of Bimekizumab in the Treatment of Subjects With Active Psoriatic Arthritis

This is a study to assess the long-term safety, long-term efficacy and tolerability of bimekizumab administered subcutaneously (sc) in adult subjects with psoriatic arthritis (PsA).

Inclusion Criteria: * In the opinion of the Investigator, the subject is expected to benefit from participation in this Open-Label Extension study * Subject completed PA0010 \[NCT03895203\] or PA0011 \[NCT03896581\] without meeting any withdrawal criteria * Female subjects must be postmenopausal, permanently sterilized or willing to use a highly effective method of contraception Exclusion Criteria: * Female subjects who plan to become pregnant during the study or within 20 weeks following the last dose of investigational medicinal product (IMP) * Subjects who meet any withdrawal criteria in PA0010 or PA0011. For any subject with an ongoing serious adverse event (SAE), or a history of serious infections (including hospitalizations) in the feeder studies, the Medical Monitor must be consulted prior to the subject's entry into PA0012, although the decision to enroll the subject remains with the Investigator * Subject has a positive or 2 indeterminate interferon gamma release assays (IGRAs) in one of the feeder studies, unless appropriately evaluated and treated