FrexalimAB in Preservation of Endogenous insULIN Secretion Compared to Placebo in adUlts and Adolescents on Top of inSulin Therapy (FABULINUS)

Inclusion Criteria:

• Participants who meet the criteria of T1D according to American Diabetes Association

• Initiated exogenous insulin replacement therapy not longer than 90 days prior toscreening visit at which random C-peptide will be assessed (V1).

• Receiving at least one of the following T1D standard of care (SOC), insulin hormonereplacement therapy

• one or multiple daily injections (MDI) of basal insulin, prandial insulinand/or premixed insulin, or

• continuous subcutaneous insulin infusion (CSII)

• Participants must be positive for at least 1 of the following T1D autoantibodiesconfirmed by medical history and/or obtained at study screening:

• Glutamic acid decarboxylase (GAD-65)

• Insulinoma Antigen-2 (IA-2)

• Zinc-transporter 8 (ZnT8) or

• Insulin (if obtained not later than 10 days after exogenous insulin therapyinitiation)

• Have random C-peptide levels ≥ 0.2 nmol/L determined at screening visit.

• Be vaccinated according to the local vaccination schedule. Any vaccinations shouldtake place at least 28 days prior to randomization for non-live vaccines and atleast 3 months prior to randomization for live vaccines.

• Contraceptive use by men and women should be consistent with local regulationsregarding the methods of contraception for those participating in clinical studies

Exclusion Criteria:

• Serious systemic viral, bacterial or fungal infection (eg, pneumonia,pyelonephritis), infection requiring hospitalization or IV antibiotics orsignificant chronic viral (including history of recurrent or active herpes zoster,acute or active cytomegalovirus (CMV), Epstein-Barr Virus (EBV) as determined atscreening), bacterial, or fungal infection (eg, osteomyelitis) 30 days before andduring screening.

• Participants with a history of invasive opportunistic infections, such as, but notlimited to histoplasmosis, listeriosis, coccidioidomycosis, candidiasis,pneumocystis jirovecii, and aspergillosis, regardless of resolution.

• Evidence of active or latent tuberculosis (TB) as documented by medical history andexamination, chest X-rays (posterior anterior and lateral), and/or TB testing. Bloodtesting (eg, QuantiFERON® TB Gold test) is strongly preferred; if not available, anylocal approved TB test is allowed.

• Evidence of any clinically significant, severe or unstable, acute or chronicallyprogressive, uncontrolled infection, medical or surgical condition (eg, but notlimited to, cerebral, cardiac, pulmonary, renal, hepatic, gastrointestinal,neurologic, acquired or inherited bone/skeletal disorders including repeated bonefractures for unknown reason, juvenile osteoporosis, osteogenesis imperfecta,osteochondropathies, or any known immune deficiency), or any condition that mayaffect participant safety in the judgment of the Investigator (includingvaccinations which are not updated based on local regulation).

• History or current hypogammaglobulinemia.

• History of a systemic hypersensitivity reaction or significant allergies, other thanlocalized injection site reaction, to any humanized mAb. Clinically significantmultiple or severe drug allergies, intolerance to topical corticosteroids, or severepost-treatment hypersensitivity reactions (including, but not limited to, erythemamultiforme major, linear IgA dermatosis, toxic epidermal necrolysis, and exfoliativedermatitis).

• Has other autoimmune diseases (eg, rheumatoid arthritis [RA], polyarticular juvenileidiopathic arthritis [pJIA], psoriatic arthritis [PsA], ankylosing spondylitis [AS],MS, SLE), except autoimmune thyroiditis with controlled function of thyroid glandand celiac disease (at discretion of investigator).

• History, clinical evidence, suspicion or significant risk for thromboembolic events,as well as myocardial infarction, stroke, antiphospholipid syndrome, otherprothrombotic disorders and/or participants requiring antithrombotic treatment.

• Diabetes of forms other than autoimmune T1D that include but is not limited togenetic forms of diabetes, maturity-onset diabetes of the young (MODY), latentautoimmune diabetes of the adult (LADA), secondary to medications or surgery, type 2diabetes by judgement of the investigator.

• History of malignancy of any organ system, treated or untreated, within 5 years ofscreening, regardless of whether there is evidence of local recurrence ormetastases.

• Systemic corticosteroids (duration > 7 days), adrenocorticotropic hormone 1 monthprior to screening.

• Any IV, IM or SC administered biologic treatments, < 3 months or < than 5 half-lives (whichever is longer), prior to randomization.

• Any live (attenuated or viral-vector) vaccine (including but not limited tovaricella zoster, oral polio, nasal influenza, rabies) within 3 months prior torandomization.

• Any non-live (inactivated, mRNA, recombinant, conjugate, toxoid) vaccineadministered less than 28 days prior to randomization.

• Other medications not compatible or interfering with IMP at discretion ofinvestigator.

• Any immunosuppressive therapy within 12 weeks prior to randomization.

• Course of Thymoglobulin®, teplizumab or other immunomodulatory treatments at anytime.

• Any drugs that may be used for treatment of T1D and type 2 diabetes other thaninsulin including but not limited to metformin, glucagon-like peptide 1 (GLP-1)agonists and sodium-glucose co-transporter-2 and 1 (SGLT2/1) inhibitor and verapamilwithin 2 weeks prior to screening.

• Abnormal laboratory test(s) at screening.

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