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:

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

2. Participant must have either typical CIDP, or one of the following 2 CIDP variants:motor CIDP (including motor-predominant CIDP), multifocal CIDP (also known as LewisSumner Syndrome). Diagnosis must be confirmed by the study adjudication committee.

3. Participants must have responded to IVIg in the past 5 years. Response must be anobjective clinically meaningful improvement defined by at least one of thefollowing: ≥1 point decrease in adjusted INCAT score, ≥4 points increase in I-RODScentile score, ≥3 points increase in the MRC-SS, ≥8 kilopascal improvement in meangrip strength (1 hand), or an equivalent improvement based on information documentedin medical records as per the Investigator's judgment.

4. Participant must be on a stable maintenance dosage of IVIg, defined as no changegreater than 10% in frequency or dose of IVIg within 8 weeks prior to Screening, andremaining stable until baseline.

5. 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).

6. Participant must be receiving treatment with IVIg within a standard maintenancedosing regimen, defined as per EAN/PNS 2021 CIDP guidelines: 0.4 to 1 g/kg every 2to 6 weeks. The IVIg maintenance dosing regimen should be equivalent or higher thana weekly dose of 0.1 g/kg body weight (for example, 0.3 g/kg every 3 weeks).

7. 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.

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

9. 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.

10. All participants must agree to use contraception methods during and after the studyas required.

11. Contraceptive use by men and women participating in the study should be consistentwith local regulations regarding the methods of contraception for thoseparticipating in clinical studies.

12. A male participant is eligible to participate if they agree to the following duringthe study intervention period and for at least 55 weeks after the last dose of studymedication.

--Refrain from donating or cryopreserving sperm. PLUS, either:

--Be abstinent from heterosexual intercourse (abstinent on a long-term andpersistent basis) and agree to remain abstinent. OR

--Must agree to use contraception/barrier as detailed below:

13. A male condom and an additional highly effective contraceptive method (Contraceptiveand barrier guidance per protocol) when having sexual intercourse with a woman ofchildbearing potential (WOCBP) who is not currently pregnant.

14. A female participant is eligible to participate if she is not pregnant orbreastfeeding, and one of the following conditions applies:

• Is a woman of nonchildbearing potential (WONCBP) as defined by the protocol. OR

• Is a WOCBP and agrees to use a contraceptive method that is highly effective (with a failure rate of <1% per year), as described in the protocol during thestudy intervention period (to be effective before starting the intervention)and for at least 55 weeks after the last administration of study interventionand agrees not to donate or cryopreserve eggs (ova, oocytes) for the purpose ofreproduction during this period.

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

16. 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:

1. 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.

2. Sensory CIDP, distal CIDP and focal CIDP variants.

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

4. Poorly controlled diabetes (HbA1c glycated hemoglobin >7% at the Screening visit).

5. Serious infections requiring hospitalization within 30 days prior to Screening, anyactive infection requiring treatment during Screening, or presence of a conditionthat may predispose the participant to increased risk of infection (eg, medicalhistory such as known immunodeficiency or history of recurrent infections).

6. 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.

7. 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.

8. 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).

9. 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.

10. 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.

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

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

13. Treatment with plasma exchange within 8 weeks prior to Screening.

14. Treatment within 3 months prior to dosing with immunosuppressive/ immunomodulatormedication, or corticosteroids (except ≤20 mg/day of prednisone or equivalent whichis allowed), or prior treatment (at any time) with highly immunosuppressive/chemotherapeutic medications with sustained effects (eg, mitoxantrone, alemtuzumab,or cladribine).

15. Prior treatment with riliprubart.

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

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

18. Prior treatment with B-cell depleting agents such as rituximab within 6 months priorto riliprubart dosing, or until return of B-cell counts to normal levels, whicheveris longer.

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

20. 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.

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

22. Positive result of any of the following tests:

• HBsAg

• Anti-HBc; unless anti-HBs Ab X are also positive, indicating natural immunity.

• Anti-HCV antibodies.

• Anti-HIV1 and anti-HIV2 antibodies.

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

24. Accommodation in an institution because of regulatory or legal order; imprisoned orlegally institutionalized.

25. 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.

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

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

28. Treatment with efgartigimod within 8 weeks prior to screening.

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