| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated  | 
 | 
| E.1.1.1 | Medical condition in easily understood language  | 
Ankylosing Spondylitis is a form of arthritis that primarily affects
 the spine. | 
 
 
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| E.1.1.2 | Therapeutic area  | Diseases [C] - Immune System Diseases [C20] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| E.1.2 | Version  | 20.0 | 
 
| E.1.2 | Level  | PT | 
 
| E.1.2 | Classification code  | 10002556 | 
 
| E.1.2 | Term  | Ankylosing spondylitis | 
 
| E.1.2 | System Organ Class  | 10028395 - Musculoskeletal and connective tissue disorders | 
 
 
 | 
| E.1.3 | Condition being studied is a rare disease  |  No  | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial  | 
Assess the long-term safety and tolerability of bimekizumab
 administered over a period of up to 4 years. | 
 
 
 | 
| E.2.2 | Secondary objectives of the trial  | 
| Assess the long-term efficacy of bimekizumab. | 
 
 
 | 
| E.2.3 | Trial contains a sub-study  |  No  | 
| E.3 | Principal inclusion criteria  | 
- In the opinion of the Investigator, the subject is expected to benefit from participation in an Open Label Extension (OLE) study.
 - Subject completed AS0008 without meeting any withdrawal criteria.
 - Female subjects must be postmenopausal, permanently sterilized or, if of childbearing potential, must be willing to use a highly effective method of contraception.
 - Male subjects with a partner of childbearing potential must be willing to use a condom when sexually active. | 
 
 
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| E.4 | Principal 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). Male subjects who are planning a partner pregnancy during the study or within 20 weeks following the last dose. 
 - Subjects with any current sign or symptom that may indicate a medically significant active infection (except for the common cold) or has had an infection requiring systemic antibiotics within 2 weeks of study entry.
 - Subjects who meet any withdrawal criteria in AS0008. For any subject with an ongoing Serious Adverse Event, or a history of serious infections (including hospitalizations) in the lead-in study, the Medical Monitor must be consulted prior to the subject's entry into AS0009. | 
 
 
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| E.5 End points | 
| E.5.1 | Primary end point(s) | 
1. Incidence of Treatment-Emergent Adverse Events (TEAEs) during the
 study
 2. Incidence of Serious Adverse Event (SAE) during the study | 
 
 
 | 
| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
| 1-2. From Entry Visit (Visit 1) until Last Visit (up to Week 208) | 
 
 
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| E.5.2 | Secondary end point(s) | 
3. Subjects who withdrew due to an Treatment-Emergent Adverse Event (TEAE) during the study
 4. Subjects with Axial Spondyloarthritis International Society 40% response criteria (ASAS40) at Week 48 calculated relative to Baseline of AS0008
 5. Subjects with Axial Spondyloarthritis International Society 20% response criteria (ASAS20) at Week 48 calculated relative to Baseline of AS0008
 6. Change from Baseline of AS0008 in Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) to Week 48  | 
 
 
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| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
3: From Entry Visit (Visit 1) until Last Visit (up to Week 208)
 4-6: Baseline of AS0008, Week 48 | 
 
 
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| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis |  No  | 
| E.6.2 | Prophylaxis |  No  | 
| E.6.3 | Therapy |  Yes  | 
| E.6.4 | Safety |  Yes  | 
| E.6.5 | Efficacy |  Yes  | 
| E.6.6 | Pharmacokinetic |  Yes  | 
| E.6.7 | Pharmacodynamic |  Yes  | 
| E.6.8 | Bioequivalence |  No  | 
| E.6.9 | Dose response |  No  | 
| E.6.10 | Pharmacogenetic |  No  | 
| E.6.11 | Pharmacogenomic |  No  | 
| E.6.12 | Pharmacoeconomic |  No  | 
| E.6.13 | Others |  Yes  | 
| E.6.13.1 | Other scope of the trial description | 
 | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) |  No  | 
| E.7.1.1 | First administration to humans |  No  | 
| E.7.1.2 | Bioequivalence study |  No  | 
| E.7.1.3 | Other |  No  | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) |  Yes  | 
| E.7.3 | Therapeutic confirmatory (Phase III) |  No  | 
| E.7.4 | Therapeutic use (Phase IV) |  No  | 
| E.8 Design of the trial | 
| E.8.1 | Controlled |  No  | 
| E.8.1.1 | Randomised |  No  | 
| E.8.1.2 | Open |  Yes  | 
| E.8.1.3 | Single blind |  No  | 
| E.8.1.4 | Double blind  |  No  | 
| E.8.1.5 | Parallel group |  No  | 
| E.8.1.6 | Cross over  |  No  | 
| E.8.1.7 | Other |  No  | 
| E.8.2 |  Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) |  No  | 
| E.8.2.2 | Placebo  |  No  | 
| E.8.2.3 | Other |  No  | 
| E.8.2.4 | Number of treatment arms in the trial | 1 | 
| E.8.3 | 
                                The trial involves single site in the Member State concerned
                             |  No  | 
| E.8.4 |  The trial involves multiple sites in the Member State concerned  |  Yes  | 
| E.8.4.1 | Number of sites anticipated in Member State concerned | 4 | 
| E.8.5 | The trial involves multiple Member States |  Yes  | 
| E.8.5.1 | Number of sites anticipated in the EEA | 70 | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.1 | Trial being conducted both within and outside the EEA |  Yes  | 
| E.8.6.2 | Trial being conducted completely outside of the EEA |  No  | 
| E.8.6.3 | If E.8.6.1 or E.8.6.2 are Yes, specify the regions in which trial sites are planned | 
| Bulgaria | 
 
| Canada | 
 
| Czech Republic | 
 
| Germany | 
 
| Hungary | 
 
| Poland | 
 
| Russian Federation | 
 
| Spain | 
 
| Ukraine | 
 
| United States | 
 
 
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| E.8.7 | Trial has a data monitoring committee |  No  | 
| E.8.8 | 
                        Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial
                     | 
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| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 5 | 
| E.8.9.1 | In the Member State concerned months | 0 | 
| E.8.9.1 | In the Member State concerned days | 8 | 
| E.8.9.2 | In all countries concerned by the trial years | 5 | 
| E.8.9.2 | In all countries concerned by the trial months | 0 | 
| E.8.9.2 | In all countries concerned by the trial days | 8 |