SAR439459 is a human anti-Transforming growth factor β (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.

The duration of the study for all participants will be approximately 29 weeks:

• Up to 5 weeks from initiation of screening to dose administration
• Treatment on Day 1
• Follow-up and observation of safety and PD for 24 weeks
• Final study visit at Week 24

Inclusion Criteria:

• Participants who are clinically categorized as Type I or IV osteogenesis imperfecta with a previously documented pathogenic genetic variant in human collagen type 1 alpha 1 gene (COL1A1) or human collagen type 1 alpha 2 gene (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 (note: only two of the L1-L4 vertebrae are necessary for evaluation).

• History of moderate (25-40°) to severe (>40°) scoliosis assessed as Cobb angle (unless scoliosis does not impact assessment of bone mineral density in the lumbar vertebrae in the opinion of the investigator).

• Postmenopausal women who:

  • Are within 5 years of the onset of menopause (for example less than 5 years from their last menstruation or post-hysterectomy), however if the person has been on hormone replacement therapy for more than 1 year prior to enrollment, then they are eligible regardless of time from onset of menopause. The person must be willing to continue hormone replacement therapy throughout the study duration. OR
  • Were previously on hormone replacement therapy but have stopped within the past 5 years.

• 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 central nervous system (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.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org