A Study to Evaluate SAR441566 Efficacy and Safety in Adults With Rheumatoid Arthritis

Inclusion Criteria:

• Diagnosis of adult-onset RA classified by ACR/EULAR 2010 revised classificationcriteria for RA of at least 3 months duration, with the onset of signs and symptomsof RA of at least 6 months duration

• Moderate-to-severely active RA, defined as:

• persistently active disease >= 6 tender and >= 6 swollen joints

• high sensitivity C-reactive protein ≥ 4 mg/L

• Continuous treatment with MTX for at least 12 consecutive weeks prior torandomization and with stable dose/means of administration at least 6 weeks prior tothe screening visit

• MTX - 10 to 25 mg/week (or per local labeling requirements for the treatment ofRA if the dose range differs) and folic/folinic acid (as part of MTX regimen)

• Inadequate clinical response to MTX at a dose of 10-25 mg/week after proper doseescalation according to local standards

• BMI within the range [18 - 35] kg/m^2 (inclusive)

Exclusion Criteria:

• Immunologic disorder other than RA, with the exception of secondary Sjogren'ssyndrome associated with RA, and medically controlled diabetes or thyroid disorderas per Investigator's judgement

• Any condition (other than RA) requiring oral, intravenous, IM, or intra-articularglucocorticoid therapy

• Uncontrolled polymyalgia rheumatica or fibromyalgia

• History of recurrent or recent serious infection (eg, pneumonia, septicemia) orinfection(s) requiring hospitalization or treatment with IV anti-infectives (antibiotics, antivirals, antifungals, antihelminthics) within 30 days prior to D1.Infections(s) requiring oral anti-infectives (antibiotics, antivirals, antifungals,antihelminthics) within 14 days prior to D1

• Known history of or suspected significant current immunosuppression, includinghistory of invasive opportunistic or helminthic infections despite infectionresolution or otherwise recurrent infections of abnormal frequency or prolongedduration

• History of moderate-to-severe congestive heart failure (NYHA Class III or IV),recent cerebrovascular accident, or any other condition in the opinion of theInvestigator that would put the participant at risk by participation in the protocol

• History of solid organ transplant

• History of alcohol or drug abuse within the past 2 years

• History of diagnosis of demyelinating disease such as but not limited to:

• Multiple Sclerosis

• Acute Disseminated Encephalomyelitis

• Balo's Disease (Concentric Sclerosis)

• Charcot-Marie-Tooth Disease

• Guillain-Barre Syndrome

• human T-lymphotropic virus 1 Associated Myelopathy

• Neuromyelitis Optica (Devic's Disease)

• Planned surgery during the treatment period

• Participants who are Steinbrocker class IV functional capacity (incapacitated,largely or wholly bed-ridden or confined to a wheelchair, with little or noself-care)

• Vaccination with live or live-attenuated virus vaccine within 3 months prior toscreening or plan to receive one during the trial including at least 3 months afterthe last dose of study drug

• Any non-live vaccine (eg, COVID-19) within 14 days prior to randomization or plan toreceive one during the trial

• Participant with personal or family history of long QT syndrome

• Active malignancy, lymphoproliferative disease, or malignancy in remission for lessthan 5 years, except adequately treated (cured) localized carcinoma in situ of thecervix or ductal breast, or squamous cell carcinoma, or basal cell carcinoma of theskin

• Previous or current use of biologic therapy or targeted synthetic disease modifyinganti-rheumatic drugs (tsDMARD - such as JAK inhibitors) for RA

• Use of oral glucocorticoid greater than prednisone 10 mg per day or equivalent perday, or a change in dosage within 4 weeks prior to screening. The dose of oralglucocorticoid must remain stable.

• Use of parenteral glucocorticoids or intra-articular glucocorticoids within 4 weeksprior to screening

• Initiation or change in dose for nonsteroidal anti-inflammatory drugs (NSAIDs)within 1 week prior to screening

The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.