The main purpose of this study is to evaluate the efficacy and safety of LY3871801 in adult participants with active moderately-to-severe rheumatoid arthritis (RA).

Inclusion Criteria:

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

• Have moderately-to-severely active RA at screening and baseline, defined by the presence 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 of response) 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 per investigator 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 ischemic attack 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 and non-radiographic axial spondyloarthritis
    • reactive arthritis
    • gout
    • scleroderma
    • polymyositis
    • dermatomyositis
    • active fibromyalgia, or
    • multiple sclerosis

Anonymized individual patient level data will be provided in a secure access environment upon approval of a research proposal and a signed data sharing agreement.

Data are available 6 months after the primary publication and approval of the indication studied in the US and European Union (EU), whichever is later. Data will be indefinitely available for requesting.

A research proposal must be approved by an independent review panel and researchers must sign a data sharing agreement.