Long-term Safety, Tolerability, and Efficacy of Bimekizumab in Adults with Active Psoriatic Arthritis: A Multicenter, Open-label Extension Study

The primary objective of this study is to assess the long-term **safety** and **tolerability** of bimekizumab when administered subcutaneously in adult subjects with **Psoriatic Arthritis**. This is clinically relevant as it aims to ensure that bimekizumab can be safely used over extended periods, which is crucial for chronic conditions like Psoriatic Arthritis that require ongoing management.

Secondary objectives include:

• Assessing the long-term **efficacy** of bimekizumab. This will provide insights into the sustained therapeutic benefits of the treatment, which is important for maintaining patient quality of life and managing disease progression.

The clinical trial involves a total of **471 participants** diagnosed with **Psoriatic Arthritis**. The study population includes both male and female adults, with an age range that encompasses individuals from young adulthood to older age. Participants were selected based on their completion of previous studies PA0010 or PA0011 without meeting any withdrawal criteria, and they are expected to benefit from participation in this Open-Label Extension study. Female participants are required to be postmenopausal, permanently sterilized, or willing to use a highly effective method of contraception. The trial does not include vulnerable populations, and no specific lifestyle considerations such as diet or physical activity are highlighted in the selection criteria. The sponsor has not provided additional information regarding the general health status or specific lifestyle habits of the participants.

The clinical trial is designed as a **multicenter, open-label extension study** to evaluate the long-term safety, tolerability, and efficacy of **bimekizumab** in adult subjects with active **psoriatic arthritis**. The trial will involve the administration of bimekizumab via **subcutaneous injection**. The study is expected to span from November 21, 2019, to May 19, 2026, with participants involved for a maximum treatment period of 192 weeks. The primary objective is to assess the incidence of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs) throughout the study duration. Secondary endpoints include the evaluation of American College of Rheumatology (ACR) improvement responses and Psoriasis Area Severity Index (PASI) responses at various time points, as well as assessments of enthesitis and dactylitis-free states.

Participants eligible for this study must have completed prior studies PA0010 or PA0011 without meeting any withdrawal criteria and must be expected to benefit from the extension study. Female participants must be postmenopausal, permanently sterilized, or willing to use a highly effective method of contraception. The study visits will include an initial screening visit to confirm eligibility, followed by regular follow-up visits to monitor safety and efficacy outcomes. The end-of-study visit will conclude the participant's involvement, ensuring all necessary data is collected and any final assessments are completed.

Participants may be withdrawn from the study if they experience TEAEs leading to withdrawal from the investigational medicinal product, or if they no longer meet the inclusion criteria. The study will utilize a pre-filled syringe device for the administration of bimekizumab, ensuring ease of use and consistency in dosing. The trial is not categorized as a low-intervention study and is conducted as a phase III clinical trial, focusing on the long-term outcomes in patients with active psoriatic arthritis.

The clinical trial involves the administration of **bimekizumab**, an experimental medication, to assess its long-term safety, tolerability, and efficacy in subjects with active **psoriatic arthritis**. Bimekizumab is provided as a **solution for injection** and is administered via the **subcutaneous route**. The medication is supplied in a 1mL Type I glass pre-filled syringe, equipped with a staked 27G, ½” thin wall needle. The syringe is sealed with a fluropolymer laminated bromobutyl rubber stopper and a rigid needle shield, which includes an elastomeric needle cover and a polypropylene Rigid Needle Shield (RNS). Each syringe is pre-assembled and ready for use, featuring functional secondary packaging components. The maximum total dose of bimekizumab is 160 mg, with a treatment period extending up to 192 weeks.

No non-experimental treatments, such as standard-of-care therapy, placebo, or comparator treatments, are utilized in this study. The trial is designed as an open-label extension study, focusing solely on the administration of bimekizumab. Participant compliance with the dosing schedule is monitored throughout the study to ensure adherence to the treatment regimen. The study does not include a pediatric formulation, and bimekizumab is not classified as an orphan drug. The trial's primary objective is to evaluate the long-term safety and tolerability of bimekizumab in adult subjects with psoriatic arthritis.

The efficacy of **bimekizumab** in the treatment of active psoriatic arthritis will be assessed through a series of predefined endpoints. Primary efficacy endpoints include the incidence of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs) during the study. Secondary efficacy endpoints will evaluate the American College of Rheumatology (ACR) improvement responses at various timepoints, specifically ACR20, ACR50, and ACR70 responses at Weeks 24, 52, and 140, using the baseline data from previous studies PA0010 or PA0011.

Additional secondary endpoints include the Psoriasis Area Severity Index (PASI) responses, with PASI75 and PASI90 being measured at Weeks 24, 52, and 140. The Investigator Global Assessment (IGA) will also be utilized to determine scores of 0 (clear) or 1 (almost clear) with at least a 2-grade reduction at the same timepoints. Enthesitis and dactylitis will be assessed using the Leeds Enthesitis Index (LEI) and the Leeds Dactylitis Index (LDI), respectively, at Weeks 24, 52, and 140, focusing on achieving an enthesitis-free or dactylitis-free state.

The efficacy assessments will be conducted at specified intervals throughout the study, ensuring a comprehensive evaluation of the long-term effects of bimekizumab. These assessments will be based on validated scales and indices, providing a robust framework for determining the therapeutic impact of the treatment on patients with psoriatic arthritis.