This Phase 2b, multicenter, double-blind, placebo-controlled, randomized withdrawal study is designed to assess the efficacy and safety of IMVT-1402 in adult participants with active, difficult-to-treat, anti-citrullinated protein autoantibody (ACPA) positive rheumatoid arthritis (RA).

The primary objective is to evaluate the effects of IMVT-1402 compared to placebo, as measured by the American College of Rheumatology 20% (ACR20) response at Week 28.

The total duration of study participation is expected to be up to 86 weeks for an individual participant with 16 weeks of open-label treatment, 12 weeks of blinded randomized treatment, and 48 weeks of optional long-term extension treatment.

Inclusion Criteria:

• Male and Female participants of age >18 years will be enrolled.
• Diagnosis of 'definite RA' according to the 2010 ACR/ European Alliance of Associations for Rheumatology (EULAR) Rheumatoid Arthritis Classification Criteria.
• Greater than or equal to 6/68 in tender joint count (TJC) and ≥ 6/66 swollen joint count (SJC) at both Screening and Baseline visits.
• C-reactive protein ≥ upper limit of normal (ULN) at Screening Visit.
• Elevated immunoglobulin G (IgG) + ACPA at the Screening Visit.
• Inadequate response to at least 2 classes of biologic/targeted synthetic disease-modifying antirheumatic drugs (DMARDs).

Additional inclusion criteria are defined in the protocol.

Exclusion Criteria:

• Have received rituximab and experienced insufficient efficacy or loss of efficacy
• History of any chronic inflammatory arthritis with onset prior to age 18 or history of acute inflammatory joint disease of different origin from RA.
• Active malignancy or history of malignancy within 5 years prior to Screening Visit.
• Medical history of primary immunodeficiency, T cell or humoral, including common variable immunodeficiency.
• Used any nonimmunosuppressive fragment crystallizable (Fc)-based therapeutic protein (e.g., monoclonal antibody [mAb] or Fc-fusion protein) within 4 weeks prior to or at Screening Visit.
• Used any anti-FcRn treatment within 2 months prior to or at Screening Visit or have a documented history of non-response to prior anti-FcRn treatment.

Other, more specific exclusion criteria are defined in the protocol.