| 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  | 
 | 
| 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  | 23.1 | 
 
| E.1.2 | Level  | PT | 
 
| E.1.2 | Classification code  | 10039073 | 
 
| E.1.2 | Term  | Rheumatoid arthritis | 
 
| 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  | 
| To demonstrate the superiority in efficacy of abatacept compared with adalimumab, both on background MTX, in achieving clinical response (ACR50) at Week 24, in early, seropositive (RF+ and ACPA+) RA patients with the SE HLA Class II risk alleles (ie, SE+). | 
 
 
 | 
| E.2.2 | Secondary objectives of the trial  | 
To compare the efficacy of abatacept with adalimumab, both on background MTX in achieving:
 -  clinical remission criteria (DAS28-CRP remission) at Week 24 in early, seropositive RA patients with the SE HLA Class II risk alleles (ie, SE+).
 - clinical response (ACR50) at Week 24 in the whole study population of early, seropositive RA patients.
 - clinical remission criteria (CDAI remission) at Week 24 in early, seropositive RA patients with the SE HLA Class II risk alleles (ie, SE+).
 - improvement in pain at Week 24 in early, seropositive RA patients with the SE HLA Class II risk alleles (ie, SE+).
 
  To determine:
 -  the efficacy over time by treatment in early, seropositive RA patients (SE+ subset and whole population).
 - the improvement in health-related quality of life over time by treatment in early, seropositive RA patients (SE+ subset and whole population). | 
 
 
 | 
| E.2.3 | Trial contains a sub-study  |  No  | 
| E.3 | Principal inclusion criteria  | 
- Early rheumatoid arthritis (RA), defined as symptoms of RA that started ≤ 12 months prior to screening and satisfied the American College of Rheumatology/European League Against Rheumatism 
 (ACR/EULAR) 2010 criteria for the classification of RA at some point during the 12-month period
 - Naïve to any targeted (biologic or nonbiologic) disease-modifying antirheumatic drugs (DMARDs), conventional synthetic DMARDs other than methotrexate (MTX), or investigational therapies for RA
 - Treated with MTX for at least 12 weeks, with a stable dose of oral or parenteral MTX for at least 4 weeks prior to randomization
 - Anti-cyclic citrullinated peptide-2 (Anti-CCP-2) test that is > 3× the upper limit of normal and are positive for rheumatoid factor (RF) according to central lab testing during screening
 -  At least a Disease Activity Score 28-joint count calculated using C-reactive protein (DAS28-CRP) ≥ 3.2 at screening
 - At least 3 tender and at least 3 swollen joints at screening and at randomization    | 
 
 
 | 
| E.4 | Principal exclusion criteria | 
- Women who are breastfeeding
 - Autoimmune disease other than RA (e.g., psoriasis, systemic lupus erythematosus [SLE], vasculitis, seronegative spondyloarthritis, inflammatory bowel disease, Sjogren's syndrome) or currently active fibromyalgia
 - History of or current inflammatory joint disease other than RA (e.g., psoriatic arthritis, gout, reactive arthritis, Lyme disease)
 - At risk for tuberculosis
 - Recent acute infection
 - History of chronic or recurrent bacterial infection (e.g., chronic pyelonephritis, osteomyelitis, bronchiectasis)
 - History of infection of a joint prosthesis or artificial joint
 - History of systemic fungal infections (such as histoplasmosis, blastomycosis, or coccidiomycosis)
 - History of primary immunodeficiency
 - Current clinical findings or a history of a demyelinating disorder 
 - 5 or more joints cannot be assessed for tenderness or swelling   | 
 
 
 | 
| E.5 End points | 
| E.5.1 | Primary end point(s) | 
| Proportion of SE+ participants meeting ACR50 response at Week 24 | 
 
 
 | 
| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
 | 
| E.5.2 | Secondary end point(s) | 
1. Proportion of SE+ participants achieving DAS28-CRP remission (DAS28-CRP < 2.6) at Week 24
 2. Proportion of whole study population participants meeting ACR50 response at Week 24
 3. Proportion of SE+ participants achieving CDAI remission (CDAI ≤ 2.8) at Week 24
 4. Mean change from baseline in SE+ participant-reported pain (VAS) at Week 24
 5. Proportion of SE+ subset and whole population achieving ACR20/50/70 responses, DAS remission, CDAI remission, SDAI remission over the SBTP and OLTP; mean changes from baseline in DAS28-CRP, CDAI, SDAI over the SBTP and OLTP; mean changes from baseline in the 7 ACR core components over the SBTP and OLTP
 6. Mean change from baseline in SF-36 in SE+ subset and whole population at Week 24 and Week 104 (4 physical and 4 mental subscales and the physical component and mental component summary) | 
 
 
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| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
1-4. At Week 24
 5. Over the SBTP and OLTP
 6. At Week 24 and Week 104 | 
 
 
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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 |  No  | 
| E.6.7 | Pharmacodynamic |  No  | 
| 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 |  No  | 
| 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) |  No  | 
| E.7.3 | Therapeutic confirmatory (Phase III) |  Yes  | 
| E.7.4 | Therapeutic use (Phase IV) |  No  | 
| E.8 Design of the trial | 
| E.8.1 | Controlled |  Yes  | 
| E.8.1.1 | Randomised |  Yes  | 
| E.8.1.2 | Open |  No  | 
| E.8.1.3 | Single blind |  Yes  | 
| 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) |  Yes  | 
| E.8.2.2 | Placebo  |  No  | 
| E.8.2.3 | Other |  No  | 
| E.8.2.4 | Number of treatment arms in the trial | 2 | 
| 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 | 5 | 
| E.8.5 | The trial involves multiple Member States |  Yes  | 
| E.8.5.1 | Number of sites anticipated in the EEA | 27 | 
| 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 | 
| Argentina | 
 
| Australia | 
 
| Japan | 
 
| Mexico | 
 
| Taiwan | 
 
| United States | 
 
| France | 
 
| Poland | 
 
| Sweden | 
 
| Netherlands | 
 
| Spain | 
 
| Switzerland | 
 
| Czechia | 
 
| Germany | 
 
| Italy | 
 
| United Kingdom | 
 
 
 | 
| 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
                     | 
| End of trial is defined as last visit for the last participant. | 
 
 
 | 
| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 3 | 
| E.8.9.1 | In the Member State concerned months | 5 | 
| E.8.9.1 | In the Member State concerned days | 6 | 
| E.8.9.2 | In all countries concerned by the trial years | 3 | 
| E.8.9.2 | In all countries concerned by the trial months | 6 | 
| E.8.9.2 | In all countries concerned by the trial days | 22 |