An Adaptive Phase 2a/2b Study of LY3871801 in Adult Participants With Rheumatoid Arthritis

Inclusion Criteria:

• Have a diagnosis of adult-onset RA for at least 3 months prior to screening asdefined by the 2010 ACR/European League Against Rheumatism (EULAR) classificationcriteria.

• Have moderately-to-severely active RA at screening and baseline, defined by thepresence of

• ≥6 swollen joints based on 66 joint count, and

• ≥6 tender joints based on 68 joint count.

• Have had a history of failure (an inadequate response, intolerance, or loss ofresponse) to at least 1 conventional synthetic disease modifying anti rheumatic drug (csDMARD) and either 1 biologic (bDMARD), or targeted synthetic (tsDMARD) treatment.

Exclusion Criteria:

• Have Class IV RA according to ACR revised criteria

• Have presence of 1 or more significant concurrent medical conditions perinvestigator judgment, including but not limited to

• poorly controlled diabetes or hypertension

• chronic kidney disease stage IIIa or IIIb, IV, or V

• symptomatic heart failure according to New York Heart Association class II,III, or IV

• myocardial infarction,unstable angina pectoris, stroke, or transient ischemicattack within the past 12 months before randomization

• severe chronic pulmonary disease, for example, requiring oxygen therapy

• major chronic inflammatory disease or connective tissue disease other than RA,including but not limited to

• systemic lupus erythematosus

• psoriatic arthritis

• axial spondyloarthritis,including ankylosing spondylitis andnon-radiographic axial spondyloarthritis

• reactive arthritis

• gout

• scleroderma

• polymyositis

• dermatomyositis

• active fibromyalgia, or

• multiple sclerosis