A Study to Assess the Concentration of Bimekizumab in Mature Breast Milk From Mothers Receiving Treatment With Bimzelx® (Bimekizumab)

Inclusion Criteria:

• Study participant must be at least 18 years of age at the time of signing theinformed consent.

• Study participant is being treated with commercial bimekizumab per locally approvedprescribing information and in accordance with her treating physician.

• Study participant is breastfeeding and intends to breastfeed throughout the SamplingPeriod.

• The decision to treat with bimekizumab and to breastfeed is made independently fromand prior to the study participant consenting to participate in the study.

• Study participant must be on bimekizumab treatment for at least 12 weeks afterdelivery and since starting/restarting/continuing bimekizumab prior to sampling (prior to start of the Sampling Period).

• A female study participant is eligible to participate if she is not pregnant anddoes not plan to become pregnant during the study.

Exclusion Criteria:

• Study participant has any medical, obstetrical, or psychiatric condition that, inthe opinion of the Investigator, could jeopardize or would compromise the studyparticipant's ability to participate in this study.

• The infant has any abnormality noted on physical examination or medical historythat, in the opinion of the Investigator, may jeopardize or compromise studyparticipation.

• Study participant has a history of chronic alcohol or drug abuse within the previouslast year.

• Study participant has history of breast implants, breast augmentation, or breastreduction surgery.

• Study participant plans a surgical intervention during the Screening Period andSampling Period or anticipates having surgery while participating in the SamplingPeriod (does not apply to tubal ligation).

• Study participant or her infant has participated in another study of aninvestigational medicinal product (IMP) (and/or an investigational device) withinthe previous 6 months or is currently participating in another study of an IMP (and/or an investigational device), unless the study is UCB PS0036 or a bimekizumabregistry study.

• Study participant or her infant has previously participated (ie, entered thesampling period) in this study.