A Study to Test the Efficacy and Safety of Riliprubart Against the Usual Treatment of Intravenous Immunoglobulin (IVIg) in People With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

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 2 CIDP variants:motor CIDP, multifocal CIDP (also known as Lewis Sumner Syndrome). Diagnosis must beconfirmed by the study adjudication committee.

• Participants must have responded to IVIg in the past 5 years.

• Participant must be on a stable maintenance dosage of IVIg.

• Participant must have residual disability, defined as an INCAT score of 2 to 9 atScreening that is confirmed at baseline (a score of 2 should be exclusively from legdisability component of INCAT).

• Participant must be receiving treatment with IVIg within a standard maintenancedosing regimen, defined as per EAN/PNS 2021 CIDP guidelines.

• Participants receiving IVIg infusions at home are eligible, as long as IVIginfusions are switched to a hospital or infusion center setting at least 1 cycleprior to baseline.

• 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

• Participant must have a body weight at Screening of 35 kg to 154 kg (77 to 340 lbs)inclusive.

• Evidence of at least one clinically meaningful deterioration within 2 years, or atleast 2 clinically meaningful deteriorations within 5 years prior to screening whichoccurred during period of interrupted dosing, reduced dosage, or extended intervalsbetween doses of immunoglobin therapy, as verified by clinical examination ormedical records.

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 IgM monoclonal gammopathy, POEMS syndrome, lumbosacralradiculoplexus 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, anyactive infection requiring antimicrobial treatment during Screening, or presence ofa condition that may predispose the participant to increased risk of infection (eg,medical history such as known immunodeficiency or history of recurrent infections).

• 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 contraindication related to the administration of immunoglobulins (eghypersensitivity, chronic kidney disease, thromboembolic diseases or recentthromboembolic event, known history of IgA deficiency at the time of Screening).

• Any other clinically meaningful medical history or ongoing medical condition (asdetermined by the Investigator at Screening) that might impact the 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, per theInvestigator'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 the C-SSRS duringScreening, OR if in the Investigator's judgment, the participant is at risk for asuicide attempt.

• 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.

• Recent treatment with plasma exchange

• Treatment within 3 months prior to dosing with immunosuppressive/ immunomodulatormedication, or corticosteroids (with exception of maintenance dose, which isallowed), or prior treatment (at any time) with highly immunosuppressive/chemotherapeutic medications with sustained effects (eg, mitoxantrone, alemtuzumab,or cladribine).

• Prior treatment with riliprubart.

• Recent use of any specific complement system inhibitor (eg, eculizumab).

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

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

• 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; imprisoned orlegally institutionalized.

• Participant not suitable for participation, whatever the reason, as judged by theInvestigator, including medical or clinical conditions, or participants potentiallyat risk of noncompliance to study procedures.

• Participants are employees of the clinical study site or other individuals directlyinvolved in the conduct of the study, or immediate family members of suchindividuals.

• Any country-related specific regulation that would prevent the participant fromentering the study as defined by the protocol.

• Recent treatment with efgartigimod.

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