A Study to Test the Effects and Safety of Riliprubart in People With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) for Which the Usual Treatments do Not Work

Inclusion Criteria:

Participants are eligible to be included in the study only if all of the following criteria apply:

• Participant must have CIDP or possible CIDP criteria, based on European Academy ofNeurology (EAN)/ Peripheral Nerve Society (PNS) Task Force CIDP guidelines, secondrevision (2021).

• Participant must have either typical CIDP, or one of the following two CIDPvariants: motor CIDP, multifocal CIDP (also known as Lewis Sumner Syndrome).Diagnosis must be confirmed by the adjudication committee.

• Participant must be refractory to either immunoglobulin therapy or corticosteroidtherapy, as defined below.

• Immunoglobulin-refractory subgroup: Historic evidence of failure or inadequateresponse to immunoglobulin therapy prior to screening

• Corticosteroid-refractory subgroup: Historic evidence of failure or inadequateresponse to corticosteroid therapy prior to screening

• Participant has an INCAT score of 2 to 9

• Any allowed immunosuppressant drugs (azathioprine, cyclosporine, or mycophenolatemofetil) have been taken for ≥6 months

• Participant may be receiving low-dose oral corticosteroids (≤20 mg/day of prednisoneor equivalent)

• Participant must have active disease, defined by a CIDP disease activity score (CDAS) of ≥ 2 points at Screening

• Participant must have documented vaccinations against encapsulated bacterialpathogens given within 5 years prior to Day 1 or initiated a minimum of 14 daysprior to first dose of study intervention

• Contraception for sexually active male or female participants; not pregnant orbreastfeeding; no sperm donating for male participant

• A body weight at Screening of 35 kg to 154 kg (77 to 340 lbs), inclusive

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

• Polyneuropathy of other causes, including but not limited to: acute demyelinatingpolyneuropathies (eg, Guillain-Barré syndrome), hereditary demyelinatingneuropathies, neuropathies secondary to infection or systemic disease, diabeticneuropathy, drug- or toxin-induced neuropathies, multifocal motor neuropathy,polyneuropathy related to Immunoglobulin M (IgM) monoclonal gammopathy, POEMSsyndrome, and lumbosacral radiculoplexus neuropathy.

• Sensory CIDP, Distal CIDP and focal CIDP variants.

• Any other neurological or systemic disease that can cause symptoms and signsinterfering with treatment or outcome assessments

• Poorly controlled diabetes

• Serious infections requiring hospitalization within 30 days prior to Screening andany active infection requiring antimicrobial treatment during screening or presenceof a condition that may predispose the participant to increased risk of infection (eg, medical history such as known immunodeficiency or history of recurrentinfections)

• Clinical diagnosis of Systemic Lupus Erythematosus (SLE) or family history of SLE.For a participant with an antinuclear antibody (ANA) titer ≥1:160 and a positiveanti-double-stranded DNA (anti-dsDNA) at Screening, SLE diagnosis must be ruled outprior to enrollment.

• Sensitivity to any of the study interventions, or components thereof, or drug orother allergy that, in the opinion of the Investigator, contraindicatesparticipation in the study. Specifically, history of any hypersensitivity reactionto riliprubart or its components or of a severe allergic or anaphylactic reaction toany humanized or murine monoclonal antibody.

• Any other clinically meaningful medical history or ongoing medical condition (asdetermined by the Investigator at Screening) that might impact benefit-riskassessment, jeopardize the safety of the participant, or compromise the quality ofthe data collected in this study; or history or presence of other significantconcomitant illness that would adversely affect participation in this study, perInvestigator's judgment.

• Documented history of attempted suicide over the 6 months prior to the Screeningvisit, presence of suicidal ideation of category 4 or 5 on C-SSRS during screening,OR if in the Investigator's judgment, the participant is at risk for a suicideattempt.

• Evidence of CIDP worsening within the 6 weeks following a prior vaccination that, inthe opinion of the Investigator, constituted a relapse

• Recent or planned major surgery that could confound the results of the trial or putthe participant at undue risk

• Participant has recently received immunoglobulins (IVIg or SCIg)

• Recent treatment with plasma exchange

• Prior treatment with riliprubart

• Prior treatment with (any time) with highly immunosuppressive/chemotherapeuticmedications with sustained effects, eg, mitoxantrone, alemtuzumab, cladribine

• Prior treatment (any time) with total lymphoid irradiation or bone marrowtransplantation

• Prior treatment with B-cell-depleting agents such as rituximab within 6 months

• Use of any specific complement system inhibitor (eg, eculizumab) within 12 weeks or 5 times the half-life of the product, whichever is longer

• Treatment within 6 months prior to dosing with immunosuppressive/ chemotherapeuticmedications, such as cyclophosphamide, methotrexate, tacrolimus, interferon, ortumor necrosis factor (TNF)-α inhibitors. Certain immunosuppressants commonly usedin CIDP (azathioprine, cyclosporine, or mycophenolate mofetil) are allowed, asindicated under inclusion criterion.

• Any vaccination received within 28 days prior to dosing (with few exceptions to beconfirmed at screening)

• Participation in another clinical trial with an investigational drug or receipt ofan investigational product within 12 weeks or 5 times the half-life of the product,whichever is longer, prior to Screening

• Any screening laboratory values outside normal limits or abnormal ECG considered inthe Investigator's judgment to be clinically significant in the context of thistrial

• Positive result of any of the following tests:

• Hepatitis B surface antigen (HBsAg).

• Anti-hepatitis B core antibodies (anti-HBc Ab) (unless anti-hepatitis B surfaceantibodies [anti-HBs Ab] are also positive, indicating natural immunity).

• Anti-hepatitis C virus (anti-HCV) antibodies (participants with positivehepatitis C antibody due to prior resolved disease can be enrolled, only if aconfirmatory negative Hepatitis RNA test is obtained).

• Anti-human immunodeficiency virus 1 and 2 (anti-HIV1 and anti-HIV2) antibodies.

• Pregnancy, defined as a positive result of a highly sensitive urine or serumpregnancy test, or lactation

• Accommodation in an institution because of regulatory or legal order; eg, imprisonedor legally institutionalized

• Participant not suitable for participation, whatever the reason, as judged by theInvestigator, including medical or clinical conditions, or potential risk fornoncompliance to study procedures

• Participants are employees at the clinical study site or other individuals directlyinvolved in the conduct of the study, or immediate family member of such individuals

• Any country related specific regulation that would prevent the participant fromentering the study

• Recent treatment with efgartigimod

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