SAR439459 is a human anti-TGFβ monoclonal antibody. This phase 1 clinical study investigates the safety, tolerability, and activity of a single dose of SAR439459 in adult participants with OI.

Participants will receive a single IV dose of SAR439459 with safety, pharmacokinetic (PK), and pharmacodynamic (PD) assessments over 24 weeks.

There will be up to 3 dose cohorts. In addition to safety, tolerability, and PK assessments, bone mineral density (BMD) will be evaluated by dual-energy Xray absorptimetry (DXA) scan and a series of blood biomarkers will be monitored to document pharmacodynamic effects of the single dose of SAR439459.

Inclusion Criteria:

• Participants who are clinically categorized as Type I or IV osteogenesis imperfecta with a previously documented pathogenic genetic variant in COL1A1 or COL1A2.
• Participants who have experienced at least 1 bone fracture in the past 10 years OR 2 or more (≥2) fractures since the age of 18.
• Body weight ≥30.0 kg.
• Contraception for sexually active male participants or female patient; not pregnant or breastfeeding; no sperm donating for male participant.
• Signed written informed assent/consent.

Exclusion Criteria:

• Previously installed rods or metal hardware that would prevent bone mineral density evaluation of the lumbar spine.
• History of moderate (25-40°) to severe (>40°) scoliosis assessed as Cobb angle.
• Postmenopausal women.
• History of treatment with denosumab, anti-sclerostin antibody, parathyroid hormone, bisphosphonates, or any other experimental therapy for OI within 6 months prior to any study baseline assessment.
• Known bleeding disorder.
• History of significant bleeding event that required hospitalization, surgery, or a blood transfusion that was possibly associated with increased bleeding tendency.
• Any major surgery within the last 28 days prior to investigational medicinal product (IMP) administration.
• Elective surgery or invasive procedure anticipated within 6 months after the IMP administration.
• Therapeutic doses of anticoagulants or antiplatelet agents (eg, 1 mg/kg bid of enoxaparin, 300 mg of aspirin daily, and 75 mg of clopidogrel daily or equivalent) within 7 days prior to the IMP administration.
• Any known CNS or intraocular lesion that has a risk of bleeding.
• Prior history of skin cancers including melanoma, squamous cell carcinoma, or basal cell carcinoma.
• Clinically significant cardiac valvular disorder or symptomatic heart failure.
• Vitamin D (25-hydoxyvitamin D) <15 ng/dL; rescreening will be allowed after supplementation.

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